Merge pull request #86 from google/sys_ptrs

A bunch of changes to sys/prog package

33 files changed, 710 insertions, 993 deletions

diff --git a/host/host.go b/host/host.go
index 220f8aaf6..a58964e8c 100644
--- a/host/host.go
+++ b/host/host.go
@@ -60,11 +60,7 @@ func isSupportedSyzkall(c *sys.Call) bool {
 	case "syz_test":
 		return false
 	case "syz_open_dev":
-		ptr, ok := c.Args[0].(sys.PtrType)
-		if !ok {
-			return true
-		}
-		fname, ok := ptr.Type.(sys.StrConstType)
+		fname, ok := extractStringConst(c.Args[0])
 		if !ok {
 			panic("first open arg is not a pointer to string const")
 		}
@@ -84,7 +80,7 @@ func isSupportedSyzkall(c *sys.Call) bool {
 			}
 			return false
 		}
-		return check(fname.Val[:len(fname.Val)-1])
+		return check(fname)
 	case "syz_open_pts":
 		return true
 	case "syz_fuse_mount":
@@ -99,7 +95,7 @@ func isSupportedSyzkall(c *sys.Call) bool {
 }
 
 func isSupportedSocket(c *sys.Call) bool {
-	af, ok := c.Args[0].(sys.ConstType)
+	af, ok := c.Args[0].(*sys.ConstType)
 	if !ok {
 		println(c.Name)
 		panic("socket family is not const")
@@ -112,17 +108,27 @@ func isSupportedSocket(c *sys.Call) bool {
 }
 
 func isSupportedOpen(c *sys.Call) bool {
-	ptr, ok := c.Args[0].(sys.PtrType)
-	if !ok {
-		panic("first open arg is not a pointer")
-	}
-	fname, ok := ptr.Type.(sys.StrConstType)
+	fname, ok := extractStringConst(c.Args[0])
 	if !ok {
 		return true
 	}
-	fd, err := syscall.Open(fname.Val[:len(fname.Val)-1], syscall.O_RDONLY, 0)
+	fd, err := syscall.Open(fname, syscall.O_RDONLY, 0)
 	if fd != -1 {
 		syscall.Close(fd)
 	}
 	return err == nil
 }
+
+func extractStringConst(typ sys.Type) (string, bool) {
+	ptr, ok := typ.(*sys.PtrType)
+	if !ok {
+		panic("first open arg is not a pointer to string const")
+	}
+	str, ok := ptr.Type.(*sys.BufferType)
+	if !ok || str.Kind != sys.BufferString || len(str.Values) != 1 {
+		return "", false
+	}
+	v := str.Values[0]
+	v = v[:len(v)-1] // string terminating \x00
+	return v, true
+}
diff --git a/prog/analysis.go b/prog/analysis.go
index baf87fbb5..4bf6506f1 100644
--- a/prog/analysis.go
+++ b/prog/analysis.go
@@ -51,18 +51,19 @@ func newState(ct *ChoiceTable) *state {
 func (s *state) analyze(c *Call) {
 	foreachArgArray(&c.Args, c.Ret, func(arg, base *Arg, _ *[]*Arg) {
 		switch typ := arg.Type.(type) {
-		case sys.FilenameType:
-			if arg.Kind == ArgData && arg.Dir != DirOut {
-				s.files[string(arg.Data)] = true
-			}
-		case sys.ResourceType:
-			if arg.Dir != DirIn {
+		case *sys.ResourceType:
+			if arg.Type.Dir() != sys.DirIn {
 				s.resources[typ.Desc.Name] = append(s.resources[typ.Desc.Name], arg)
 				// TODO: negative PIDs and add them as well (that's process groups).
 			}
-		case sys.BufferType:
-			if typ.Kind == sys.BufferString && arg.Kind == ArgData && len(arg.Data) != 0 {
-				s.strings[string(arg.Data)] = true
+		case *sys.BufferType:
+			if arg.Type.Dir() != sys.DirOut && arg.Kind == ArgData && len(arg.Data) != 0 {
+				switch typ.Kind {
+				case sys.BufferString:
+					s.strings[string(arg.Data)] = true
+				case sys.BufferFilename:
+					s.files[string(arg.Data)] = true
+				}
 			}
 		}
 	})
@@ -149,186 +150,67 @@ func foreachArg(c *Call, f func(arg, base *Arg, parent *[]*Arg)) {
 	foreachArgArray(&c.Args, nil, f)
 }
 
-func assignTypeAndDir(c *Call) error {
-	var rec func(arg *Arg, typ sys.Type, dir ArgDir) error
-	rec = func(arg *Arg, typ sys.Type, dir ArgDir) error {
-		if arg.Call != nil && arg.Call != c {
-			panic(fmt.Sprintf("different call is already assigned: %p %p %v %v", arg.Call, c, arg.Call.Meta.Name, c.Meta.Name))
-		}
-		arg.Call = c
-		if arg.Type != nil && arg.Type.Name() != typ.Name() {
-			panic("different type is already assigned: " + arg.Type.Name() + " vs " + typ.Name())
-		}
-		arg.Type = typ
-		switch arg.Kind {
-		case ArgPointer:
-			arg.Dir = DirIn
-			switch typ1 := typ.(type) {
-			case sys.PtrType:
-				if arg.Res != nil {
-					if err := rec(arg.Res, typ1.Type, ArgDir(typ1.Dir)); err != nil {
-						return err
-					}
-				}
-			}
-		case ArgGroup:
-			arg.Dir = dir
-			switch typ1 := typ.(type) {
-			case *sys.StructType:
-				if len(arg.Inner) != len(typ1.Fields) {
-					return fmt.Errorf("wrong struct field count: %v, want %v", len(arg.Inner), len(typ1.Fields))
-				}
-				for i, arg1 := range arg.Inner {
-					if err := rec(arg1, typ1.Fields[i], dir); err != nil {
-						return err
-					}
-				}
-			case sys.ArrayType:
-				for _, arg1 := range arg.Inner {
-					if err := rec(arg1, typ1.Type, dir); err != nil {
-						return err
-					}
-				}
-			}
-		case ArgUnion:
-			arg.Dir = dir
-			if err := rec(arg.Option, arg.OptionType, dir); err != nil {
-				return err
-			}
-		default:
-			arg.Dir = dir
-		}
-		return nil
-	}
-	for i, arg := range c.Args {
-		if c.Meta == nil {
-			panic("nil meta")
-		}
-		if err := rec(arg, c.Meta.Args[i], DirIn); err != nil {
-			return err
-		}
-	}
-	if c.Ret == nil {
-		c.Ret = returnArg()
-		c.Ret.Call = c
-		c.Ret.Type = c.Meta.Ret
-		c.Ret.Dir = DirOut
-	}
-	return nil
-}
-
-func generateSize(typ sys.Type, arg *Arg, lenType sys.LenType) *Arg {
+func generateSize(arg *Arg, lenType *sys.LenType) *Arg {
 	if arg == nil {
 		// Arg is an optional pointer, set size to 0.
-		return constArg(0)
+		return constArg(lenType, 0)
 	}
 
-	switch typ.(type) {
-	case sys.VmaType:
-		return pageSizeArg(arg.AddrPagesNum, 0)
-	case sys.ArrayType:
+	switch arg.Type.(type) {
+	case *sys.VmaType:
+		return pageSizeArg(lenType, arg.AddrPagesNum, 0)
+	case *sys.ArrayType:
 		if lenType.ByteSize {
-			return constArg(arg.Size(typ))
+			return constArg(lenType, arg.Size())
 		} else {
-			return constArg(uintptr(len(arg.Inner)))
+			return constArg(lenType, uintptr(len(arg.Inner)))
 		}
 	default:
-		return constArg(arg.Size(typ))
+		return constArg(lenType, arg.Size())
 	}
 }
 
-func assignSizes(types []sys.Type, args []*Arg) {
+func assignSizes(args []*Arg) {
+	// Create a map of args and calculate size of the whole struct.
 	argsMap := make(map[string]*Arg)
-	typesMap := make(map[string]sys.Type)
-
-	// Create a map of args and types.
-	for i, typ := range types {
-		if sys.IsPad(typ) {
+	var parentSize uintptr
+	for _, arg := range args {
+		parentSize += arg.Size()
+		if sys.IsPad(arg.Type) {
 			continue
 		}
-		if typ.Name() == "parent" {
-			panic("parent is reserved len name")
-		}
-
-		innerArg := args[i].InnerArg(typ)
-		innerType := typ.InnerType()
-
-		if _, ok := argsMap[typ.Name()]; ok {
-			panic(fmt.Sprintf("mutiple args with the same name '%v', types: %+v, args: %+v", typ.Name(), types, args))
-		}
-		argsMap[typ.Name()] = innerArg
-		typesMap[typ.Name()] = innerType
-	}
-
-	// Calculate size of the whole struct.
-	var parentSize uintptr
-	for i, typ := range types {
-		parentSize += args[i].Size(typ)
+		argsMap[arg.Type.Name()] = arg
 	}
 
 	// Fill in size arguments.
-	for i, typ := range types {
-		if lenType, ok := typ.InnerType().(sys.LenType); ok {
-			lenArg := args[i].InnerArg(typ)
-			if lenArg == nil {
-				// Pointer to optional len field, no need to fill in value.
-				continue
-			}
-
-			if lenType.Buf == "parent" {
-				*lenArg = *constArg(parentSize)
+	for _, arg := range args {
+		if arg = arg.InnerArg(); arg == nil {
+			continue // Pointer to optional len field, no need to fill in value.
+		}
+		if typ, ok := arg.Type.(*sys.LenType); ok {
+			if typ.Buf == "parent" {
+				arg.Val = parentSize
 				continue
 			}
 
-			arg, ok := argsMap[lenType.Buf]
+			buf, ok := argsMap[typ.Buf]
 			if !ok {
-				panic(fmt.Sprintf("len field '%v' references non existent field '%v', argsMap: %+v, typesMap: %+v",
-					lenType.Name(), lenType.Buf, argsMap, typesMap))
+				panic(fmt.Sprintf("len field '%v' references non existent field '%v', argsMap: %+v",
+					typ.Name(), typ.Buf, argsMap))
 			}
-			typ := typesMap[lenType.Buf]
 
-			*lenArg = *generateSize(typ, arg, lenType)
+			*arg = *generateSize(buf.InnerArg(), typ)
 		}
 	}
 }
 
 func assignSizesCall(c *Call) {
-	var rec func(arg *Arg, typ sys.Type)
-	rec = func(arg *Arg, typ sys.Type) {
-		switch arg.Kind {
-		case ArgPointer:
-			switch typ1 := typ.(type) {
-			case sys.PtrType:
-				if arg.Res != nil {
-					rec(arg.Res, typ1.Type)
-				}
-			}
-		case ArgGroup:
-			switch typ1 := typ.(type) {
-			case *sys.StructType:
-				if len(arg.Inner) != len(typ1.Fields) {
-					panic(fmt.Sprintf("wrong struct field count: %v, want %v", len(arg.Inner), len(typ1.Fields)))
-				}
-				for i, arg1 := range arg.Inner {
-					rec(arg1, typ1.Fields[i])
-				}
-				assignSizes(typ1.Fields, arg.Inner)
-			case sys.ArrayType:
-				for _, arg1 := range arg.Inner {
-					rec(arg1, typ1.Type)
-				}
-			}
-		case ArgUnion:
-			rec(arg.Option, arg.OptionType)
+	assignSizes(c.Args)
+	foreachArg(c, func(arg, base *Arg, parent *[]*Arg) {
+		if _, ok := arg.Type.(*sys.StructType); ok {
+			assignSizes(arg.Inner)
 		}
-	}
-	if c.Meta == nil {
-		panic("nil meta")
-	}
-	for i, arg := range c.Args {
-		rec(arg, c.Meta.Args[i])
-	}
-	assignSizes(c.Meta.Args, c.Args)
+	})
 }
 
 func sanitizeCall(c *Call) {
diff --git a/prog/clone.go b/prog/clone.go
index 14f9db759..69a54cd4e 100644
--- a/prog/clone.go
+++ b/prog/clone.go
@@ -24,7 +24,6 @@ func (p *Prog) Clone() *Prog {
 func (arg *Arg) clone(c *Call, newargs map[*Arg]*Arg) *Arg {
 	arg1 := new(Arg)
 	*arg1 = *arg
-	arg1.Call = c
 	arg1.Data = append([]byte{}, arg.Data...)
 	switch arg.Kind {
 	case ArgPointer:
diff --git a/prog/encoding.go b/prog/encoding.go
index 01438f5b9..7afe218be 100644
--- a/prog/encoding.go
+++ b/prog/encoding.go
@@ -93,7 +93,7 @@ func (a *Arg) serialize(buf io.Writer, vars map[*Arg]int, varSeq *int) {
 		switch a.Type.(type) {
 		case *sys.StructType:
 			delims = []byte{'{', '}'}
-		case sys.ArrayType:
+		case *sys.ArrayType:
 			delims = []byte{'[', ']'}
 		default:
 			panic("unknown group type")
@@ -137,7 +137,10 @@ func Deserialize(data []byte) (prog *Prog, err error) {
 		if meta == nil {
 			return nil, fmt.Errorf("unknown syscall %v", name)
 		}
-		c := &Call{Meta: meta}
+		c := &Call{
+			Meta: meta,
+			Ret:  returnArg(meta.Ret),
+		}
 		prog.Calls = append(prog.Calls, c)
 		p.Parse('(')
 		for i := 0; p.Char() != ')'; i++ {
@@ -164,9 +167,6 @@ func Deserialize(data []byte) (prog *Prog, err error) {
 		if len(c.Args) != len(meta.Args) {
 			return nil, fmt.Errorf("wrong call arg count: %v, want %v", len(c.Args), len(meta.Args))
 		}
-		if err := assignTypeAndDir(c); err != nil {
-			return nil, err
-		}
 		if r != "" {
 			vars[r] = c.Ret
 		}
@@ -196,14 +196,14 @@ func parseArg(typ sys.Type, p *parser, vars map[string]*Arg) (*Arg, error) {
 		if err != nil {
 			return nil, fmt.Errorf("wrong arg value '%v': %v", val, err)
 		}
-		arg = constArg(uintptr(v))
+		arg = constArg(typ, uintptr(v))
 	case 'r':
 		id := p.Ident()
 		v, ok := vars[id]
 		if !ok || v == nil {
 			return nil, fmt.Errorf("result %v references unknown variable (vars=%+v)", id, vars)
 		}
-		arg = resultArg(v)
+		arg = resultArg(typ, v)
 		if p.Char() == '/' {
 			p.Parse('/')
 			op := p.Ident()
@@ -225,9 +225,9 @@ func parseArg(typ sys.Type, p *parser, vars map[string]*Arg) (*Arg, error) {
 	case '&':
 		var typ1 sys.Type
 		switch t1 := typ.(type) {
-		case sys.PtrType:
+		case *sys.PtrType:
 			typ1 = t1.Type
-		case sys.VmaType:
+		case *sys.VmaType:
 		default:
 			return nil, fmt.Errorf("& arg is not a pointer: %#v", typ)
 		}
@@ -241,13 +241,13 @@ func parseArg(typ sys.Type, p *parser, vars map[string]*Arg) (*Arg, error) {
 		if err != nil {
 			return nil, err
 		}
-		arg = pointerArg(page, off, size, inner)
+		arg = pointerArg(typ, page, off, size, inner)
 	case '(':
 		page, off, _, err := parseAddr(p, false)
 		if err != nil {
 			return nil, err
 		}
-		arg = pageSizeArg(page, off)
+		arg = pageSizeArg(typ, page, off)
 	case '"':
 		p.Parse('"')
 		val := ""
@@ -259,7 +259,7 @@ func parseArg(typ sys.Type, p *parser, vars map[string]*Arg) (*Arg, error) {
 		if err != nil {
 			return nil, fmt.Errorf("data arg has bad value '%v'", val)
 		}
-		arg = dataArg(data)
+		arg = dataArg(typ, data)
 	case '{':
 		t1, ok := typ.(*sys.StructType)
 		if !ok {
@@ -273,7 +273,7 @@ func parseArg(typ sys.Type, p *parser, vars map[string]*Arg) (*Arg, error) {
 			}
 			fld := t1.Fields[i]
 			if sys.IsPad(fld) {
-				inner = append(inner, constArg(0))
+				inner = append(inner, constArg(fld, 0))
 			} else {
 				arg, err := parseArg(fld, p, vars)
 				if err != nil {
@@ -286,12 +286,12 @@ func parseArg(typ sys.Type, p *parser, vars map[string]*Arg) (*Arg, error) {
 			}
 		}
 		p.Parse('}')
-		if sys.IsPad(t1.Fields[len(t1.Fields)-1]) {
-			inner = append(inner, constArg(0))
+		if last := t1.Fields[len(t1.Fields)-1]; sys.IsPad(last) {
+			inner = append(inner, constArg(last, 0))
 		}
-		arg = groupArg(inner)
+		arg = groupArg(typ, inner)
 	case '[':
-		t1, ok := typ.(sys.ArrayType)
+		t1, ok := typ.(*sys.ArrayType)
 		if !ok {
 			return nil, fmt.Errorf("'[' arg is not an array: %#v", typ)
 		}
@@ -308,7 +308,7 @@ func parseArg(typ sys.Type, p *parser, vars map[string]*Arg) (*Arg, error) {
 			}
 		}
 		p.Parse(']')
-		arg = groupArg(inner)
+		arg = groupArg(typ, inner)
 	case '@':
 		t1, ok := typ.(*sys.UnionType)
 		if !ok {
@@ -331,7 +331,7 @@ func parseArg(typ sys.Type, p *parser, vars map[string]*Arg) (*Arg, error) {
 		if err != nil {
 			return nil, err
 		}
-		arg = unionArg(opt, optType)
+		arg = unionArg(typ, opt, optType)
 	case 'n':
 		p.Parse('n')
 		p.Parse('i')
diff --git a/prog/encodingexec.go b/prog/encodingexec.go
index 239ef3514..4c2cd2524 100644
--- a/prog/encodingexec.go
+++ b/prog/encodingexec.go
@@ -46,7 +46,7 @@ func (p *Prog) SerializeForExec() []byte {
 				w.args[base] = &argInfo{}
 			}
 			w.args[arg] = &argInfo{Offset: w.args[base].CurSize}
-			w.args[base].CurSize += arg.Size(arg.Type)
+			w.args[base].CurSize += arg.Size()
 		})
 		// Generate copyin instructions that fill in data into pointer arguments.
 		foreachArg(c, func(arg, _ *Arg, _ *[]*Arg) {
@@ -69,7 +69,7 @@ func (p *Prog) SerializeForExec() []byte {
 					if arg1.Kind == ArgData && len(arg1.Data) == 0 {
 						return
 					}
-					if arg1.Dir != DirOut {
+					if arg1.Type.Dir() != sys.DirOut {
 						w.write(ExecInstrCopyin)
 						w.write(physicalAddr(arg) + w.args[arg1].Offset)
 						w.writeArg(arg1)
@@ -105,7 +105,7 @@ func (p *Prog) SerializeForExec() []byte {
 				instrSeq++
 				w.write(ExecInstrCopyout)
 				w.write(physicalAddr(base) + info.Offset)
-				w.write(arg.Size(arg.Type))
+				w.write(arg.Size())
 			default:
 				panic("bad arg kind in copyout")
 			}
@@ -147,21 +147,21 @@ func (w *execContext) writeArg(arg *Arg) {
 	switch arg.Kind {
 	case ArgConst:
 		w.write(ExecArgConst)
-		w.write(arg.Size(arg.Type))
-		w.write(arg.Value(arg.Type))
+		w.write(arg.Size())
+		w.write(arg.Value())
 	case ArgResult:
 		w.write(ExecArgResult)
-		w.write(arg.Size(arg.Type))
+		w.write(arg.Size())
 		w.write(w.args[arg.Res].Idx)
 		w.write(arg.OpDiv)
 		w.write(arg.OpAdd)
 	case ArgPointer:
 		w.write(ExecArgConst)
-		w.write(arg.Size(arg.Type))
+		w.write(arg.Size())
 		w.write(physicalAddr(arg))
 	case ArgPageSize:
 		w.write(ExecArgConst)
-		w.write(arg.Size(arg.Type))
+		w.write(arg.Size())
 		w.write(arg.AddrPage * pageSize)
 	case ArgData:
 		w.write(ExecArgData)
diff --git a/prog/mutation.go b/prog/mutation.go
index 577e24796..8d5fa36a4 100644
--- a/prog/mutation.go
+++ b/prog/mutation.go
@@ -57,13 +57,13 @@ func (p *Prog) Mutate(rs rand.Source, ncalls int, ct *ChoiceTable) {
 						if base.Kind != ArgPointer || base.Res == nil {
 							panic("bad base arg")
 						}
-						baseSize = base.Res.Size(base.Res.Type)
+						baseSize = base.Res.Size()
 					}
 					switch a := arg.Type.(type) {
-					case sys.IntType, sys.FlagsType, sys.FileoffType, sys.ResourceType, sys.VmaType:
-						arg1, calls1 := r.generateArg(s, arg.Type, arg.Dir)
-						p.replaceArg(arg, arg1, calls1)
-					case sys.BufferType:
+					case *sys.IntType, *sys.FlagsType, *sys.ResourceType, *sys.VmaType:
+						arg1, calls1 := r.generateArg(s, arg.Type)
+						p.replaceArg(c, arg, arg1, calls1)
+					case *sys.BufferType:
 						switch a.Kind {
 						case sys.BufferBlobRand, sys.BufferBlobRange:
 							var data []byte
@@ -89,23 +89,16 @@ func (p *Prog) Mutate(rs rand.Source, ncalls int, ct *ChoiceTable) {
 							if r.bin() {
 								arg.Data = mutateData(r, append([]byte{}, arg.Data...), int(0), ^int(0))
 							} else {
-								arg.Data = r.randString(s)
+								arg.Data = r.randString(s, a.Values, a.Dir())
 							}
-						case sys.BufferFilesystem:
-							arg.Data = r.filesystem(s)
+						case sys.BufferFilename:
+							arg.Data = []byte(r.filename(s))
 						case sys.BufferSockaddr:
 							arg.Data = r.sockaddr(s)
-						case sys.BufferAlgType:
-							arg.Data = r.algType(s)
-						case sys.BufferAlgName:
-							arg.Data = r.algName(s)
 						default:
 							panic("unknown buffer kind")
 						}
-					case sys.FilenameType:
-						filename := r.filename(s)
-						arg.Data = []byte(filename)
-					case sys.ArrayType:
+					case *sys.ArrayType:
 						count := uintptr(0)
 						switch a.Kind {
 						case sys.ArrayRandLen:
@@ -123,7 +116,7 @@ func (p *Prog) Mutate(rs rand.Source, ncalls int, ct *ChoiceTable) {
 						if count > uintptr(len(arg.Inner)) {
 							var calls []*Call
 							for count > uintptr(len(arg.Inner)) {
-								arg1, calls1 := r.generateArg(s, a.Type, arg.Dir)
+								arg1, calls1 := r.generateArg(s, a.Type)
 								arg.Inner = append(arg.Inner, arg1)
 								for _, c1 := range calls1 {
 									calls = append(calls, c1)
@@ -131,27 +124,25 @@ func (p *Prog) Mutate(rs rand.Source, ncalls int, ct *ChoiceTable) {
 								}
 							}
 							for _, c1 := range calls {
-								assignTypeAndDir(c1)
 								sanitizeCall(c1)
 							}
-							assignTypeAndDir(c)
 							sanitizeCall(c)
 							p.insertBefore(c, calls)
 						} else if count < uintptr(len(arg.Inner)) {
 							for _, arg := range arg.Inner[count:] {
-								p.removeArg(arg)
+								p.removeArg(c, arg)
 							}
 							arg.Inner = arg.Inner[:count]
 						}
 						// TODO: swap elements of the array
-					case sys.PtrType:
+					case *sys.PtrType:
 						// TODO: we don't know size for out args
 						size := uintptr(1)
 						if arg.Res != nil {
-							size = arg.Res.Size(arg.Res.Type)
+							size = arg.Res.Size()
 						}
-						arg1, calls1 := r.addr(s, size, arg.Res)
-						p.replaceArg(arg, arg1, calls1)
+						arg1, calls1 := r.addr(s, a, size, arg.Res)
+						p.replaceArg(c, arg, arg1, calls1)
 					case *sys.StructType:
 						ctor := isSpecialStruct(a)
 						if ctor == nil {
@@ -159,7 +150,7 @@ func (p *Prog) Mutate(rs rand.Source, ncalls int, ct *ChoiceTable) {
 						}
 						arg1, calls1 := ctor(r, s)
 						for i, f := range arg1.Inner {
-							p.replaceArg(arg.Inner[i], f, calls1)
+							p.replaceArg(c, arg.Inner[i], f, calls1)
 							calls1 = nil
 						}
 					case *sys.UnionType:
@@ -167,23 +158,22 @@ func (p *Prog) Mutate(rs rand.Source, ncalls int, ct *ChoiceTable) {
 						for optType.Name() == arg.OptionType.Name() {
 							optType = a.Options[r.Intn(len(a.Options))]
 						}
-						p.removeArg(arg.Option)
-						opt, calls := r.generateArg(s, optType, arg.Dir)
-						arg1 := unionArg(opt, optType)
-						p.replaceArg(arg, arg1, calls)
-					case sys.LenType:
+						p.removeArg(c, arg.Option)
+						opt, calls := r.generateArg(s, optType)
+						arg1 := unionArg(a, opt, optType)
+						p.replaceArg(c, arg, arg1, calls)
+					case *sys.LenType:
 						panic("bad arg returned by mutationArgs: LenType")
-					case sys.ConstType, sys.StrConstType:
+					case *sys.ConstType:
 						panic("bad arg returned by mutationArgs: ConstType")
 					default:
 						panic(fmt.Sprintf("bad arg returned by mutationArgs: %#v, type=%#v", *arg, arg.Type))
 					}
 
 					// Update base pointer if size has increased.
-					if base != nil && baseSize < base.Res.Size(base.Res.Type) {
-						arg1, calls1 := r.addr(s, base.Res.Size(base.Res.Type), base.Res)
+					if base != nil && baseSize < base.Res.Size() {
+						arg1, calls1 := r.addr(s, base.Type, base.Res.Size(), base.Res)
 						for _, c1 := range calls1 {
-							assignTypeAndDir(c1)
 							sanitizeCall(c1)
 						}
 						p.insertBefore(c, calls1)
@@ -194,8 +184,6 @@ func (p *Prog) Mutate(rs rand.Source, ncalls int, ct *ChoiceTable) {
 
 					// Update all len fields.
 					assignSizesCall(c)
-					// Assign Arg.Type fields for newly created len args.
-					assignTypeAndDir(c)
 				}
 			},
 			1, func() {
@@ -210,7 +198,6 @@ func (p *Prog) Mutate(rs rand.Source, ncalls int, ct *ChoiceTable) {
 		)
 	}
 	for _, c := range p.Calls {
-		assignTypeAndDir(c)
 		sanitizeCall(c)
 	}
 	if err := p.validate(); err != nil {
@@ -254,18 +241,7 @@ func Minimize(p0 *Prog, callIndex0 int, pred func(*Prog, int) bool) (*Prog, int)
 			}
 		}
 		// Prepend uber-mmap.
-		mmap := &Call{
-			Meta: sys.CallMap["mmap"],
-			Args: []*Arg{
-				pointerArg(0, 0, uintptr(hi)+1, nil),
-				pageSizeArg(uintptr(hi)+1, 0),
-				constArg(sys.PROT_READ | sys.PROT_WRITE),
-				constArg(sys.MAP_ANONYMOUS | sys.MAP_PRIVATE | sys.MAP_FIXED),
-				constArg(sys.InvalidFD),
-				constArg(0),
-			},
-		}
-		assignTypeAndDir(mmap)
+		mmap := createMmapCall(0, uintptr(hi)+1)
 		p.Calls = append([]*Call{mmap}, p.Calls...)
 		if callIndex != -1 {
 			callIndex++
@@ -332,19 +308,23 @@ func mutationArgs(c *Call) (args, bases []*Arg) {
 				return
 			}
 			// These special structs are mutated as a whole.
-		case sys.ArrayType:
+		case *sys.ArrayType:
 			// Don't mutate fixed-size arrays.
 			if typ.Kind == sys.ArrayRangeLen && typ.RangeBegin == typ.RangeEnd {
 				return
 			}
-		case sys.LenType:
+		case *sys.LenType:
 			// Size is updated when the size-of arg change.
 			return
-		case sys.ConstType, sys.StrConstType:
+		case *sys.ConstType:
 			// Well, this is const.
 			return
+		case *sys.BufferType:
+			if typ.Kind == sys.BufferString && len(typ.Values) == 1 {
+				return // string const
+			}
 		}
-		if arg.Dir == DirOut {
+		if arg.Type.Dir() == sys.DirOut {
 			return
 		}
 		if base != nil {
diff --git a/prog/prio.go b/prog/prio.go
index 8983c1c92..59a205a5d 100644
--- a/prog/prio.go
+++ b/prog/prio.go
@@ -50,9 +50,9 @@ func calcStaticPriorities() [][]float32 {
 				uses[id][c.ID] = weight
 			}
 		}
-		foreachArgType(c, func(t sys.Type, d ArgDir) {
+		sys.ForeachType(c, func(t sys.Type) {
 			switch a := t.(type) {
-			case sys.ResourceType:
+			case *sys.ResourceType:
 				if a.Desc.Name == "pid" || a.Desc.Name == "uid" || a.Desc.Name == "gid" {
 					// Pid/uid/gid usually play auxiliary role,
 					// but massively happen in some structs.
@@ -68,34 +68,35 @@ func calcStaticPriorities() [][]float32 {
 						noteUsage(float32(w), str)
 					}
 				}
-			case sys.PtrType:
+			case *sys.PtrType:
 				if _, ok := a.Type.(*sys.StructType); ok {
 					noteUsage(1.0, "ptrto-%v", a.Type.Name())
 				}
 				if _, ok := a.Type.(*sys.UnionType); ok {
 					noteUsage(1.0, "ptrto-%v", a.Type.Name())
 				}
-				if arr, ok := a.Type.(sys.ArrayType); ok {
+				if arr, ok := a.Type.(*sys.ArrayType); ok {
 					noteUsage(1.0, "ptrto-%v", arr.Type.Name())
 				}
-			case sys.BufferType:
+			case *sys.BufferType:
 				switch a.Kind {
-				case sys.BufferBlobRand, sys.BufferBlobRange, sys.BufferFilesystem, sys.BufferAlgType, sys.BufferAlgName:
+				case sys.BufferBlobRand, sys.BufferBlobRange:
 				case sys.BufferString:
-					noteUsage(0.2, "str")
+					if a.SubKind != "" {
+						noteUsage(0.2, fmt.Sprintf("str-%v", a.SubKind))
+					}
 				case sys.BufferSockaddr:
 					noteUsage(1.0, "sockaddr")
+				case sys.BufferFilename:
+					noteUsage(1.0, "filename")
 				default:
 					panic("unknown buffer kind")
 				}
-			case sys.VmaType:
+			case *sys.VmaType:
 				noteUsage(0.5, "vma")
-			case sys.FilenameType:
-				noteUsage(1.0, "filename")
-			case sys.IntType:
+			case *sys.IntType:
 				switch a.Kind {
-				case sys.IntPlain:
-				case sys.IntRange:
+				case sys.IntPlain, sys.IntFileoff, sys.IntRange:
 				case sys.IntSignalno:
 					noteUsage(1.0, "signalno")
 				case sys.IntInaddr:
@@ -196,47 +197,6 @@ func normalizePrio(prios [][]float32) {
 	}
 }
 
-func foreachArgType(meta *sys.Call, f func(sys.Type, ArgDir)) {
-	seen := make(map[sys.Type]bool)
-	var rec func(t sys.Type, dir ArgDir)
-	rec = func(t sys.Type, d ArgDir) {
-		f(t, d)
-		switch a := t.(type) {
-		case sys.ArrayType:
-			rec(a.Type, d)
-		case sys.PtrType:
-			rec(a.Type, ArgDir(a.Dir))
-		case *sys.StructType:
-			if seen[a] {
-				return // prune recursion via pointers to structs/unions
-			}
-			seen[a] = true
-			for _, f := range a.Fields {
-				rec(f, d)
-			}
-		case *sys.UnionType:
-			if seen[a] {
-				return // prune recursion via pointers to structs/unions
-			}
-			seen[a] = true
-			for _, opt := range a.Options {
-				rec(opt, d)
-			}
-		case sys.ResourceType, sys.FileoffType, sys.BufferType,
-			sys.VmaType, sys.LenType, sys.FlagsType, sys.ConstType,
-			sys.StrConstType, sys.IntType, sys.FilenameType:
-		default:
-			panic("unknown type")
-		}
-	}
-	for _, t := range meta.Args {
-		rec(t, DirIn)
-	}
-	if meta.Ret != nil {
-		rec(meta.Ret, DirOut)
-	}
-}
-
 // ChooseTable allows to do a weighted choice of a syscall for a given syscall
 // based on call-to-call priorities and a set of enabled syscalls.
 type ChoiceTable struct {
diff --git a/prog/prog.go b/prog/prog.go
index 9953f3ef0..e3a0febd2 100644
--- a/prog/prog.go
+++ b/prog/prog.go
@@ -20,10 +20,8 @@ type Call struct {
 }
 
 type Arg struct {
-	Call         *Call
 	Type         sys.Type
 	Kind         ArgKind
-	Dir          ArgDir
 	Val          uintptr       // value of ArgConst
 	AddrPage     uintptr       // page index for ArgPointer address, page count for ArgPageSize
 	AddrOffset   int           // page offset for ArgPointer address
@@ -53,26 +51,17 @@ const (
 	ArgReturn // fake value denoting syscall return value
 )
 
-type ArgDir sys.Dir
-
-const (
-	DirIn    = ArgDir(sys.DirIn)
-	DirOut   = ArgDir(sys.DirOut)
-	DirInOut = ArgDir(sys.DirInOut)
-)
-
 // Returns inner arg for PtrType args
-func (a *Arg) InnerArg(typ sys.Type) *Arg {
-	switch typ1 := typ.(type) {
-	case sys.PtrType:
+func (a *Arg) InnerArg() *Arg {
+	switch typ := a.Type.(type) {
+	case *sys.PtrType:
 		if a.Res == nil {
-			if typ.Optional() {
-				return nil
-			} else {
-				panic(fmt.Sprintf("non-optional pointer is nil\narg: %+v\ntype: %+v", a, typ1))
+			if !typ.Optional() {
+				panic(fmt.Sprintf("non-optional pointer is nil\narg: %+v\ntype: %+v", a, typ))
 			}
+			return nil
 		} else {
-			return a.Res.InnerArg(typ1.Type)
+			return a.Res.InnerArg()
 		}
 	default:
 		return a
@@ -96,43 +85,39 @@ func encodeValue(value, size uintptr, bigEndian bool) uintptr {
 }
 
 // Returns value taking endianness into consideration.
-func (a *Arg) Value(typ sys.Type) uintptr {
-	switch t := typ.(type) {
-	case sys.IntType:
-		return encodeValue(a.Val, t.Size(), t.BigEndian)
-	case sys.ConstType:
-		return encodeValue(a.Val, t.Size(), t.BigEndian)
-	case sys.FlagsType:
-		return encodeValue(a.Val, t.Size(), t.BigEndian)
-	case sys.LenType:
-		return encodeValue(a.Val, t.Size(), t.BigEndian)
-	case sys.FileoffType:
-		return encodeValue(a.Val, t.Size(), t.BigEndian)
+func (a *Arg) Value() uintptr {
+	switch typ := a.Type.(type) {
+	case *sys.IntType:
+		return encodeValue(a.Val, typ.Size(), typ.BigEndian)
+	case *sys.ConstType:
+		return encodeValue(a.Val, typ.Size(), typ.BigEndian)
+	case *sys.FlagsType:
+		return encodeValue(a.Val, typ.Size(), typ.BigEndian)
+	case *sys.LenType:
+		return encodeValue(a.Val, typ.Size(), typ.BigEndian)
 	}
 	return a.Val
 }
 
-func (a *Arg) Size(typ sys.Type) uintptr {
-	switch typ1 := typ.(type) {
-	case sys.IntType, sys.LenType, sys.FlagsType, sys.ConstType, sys.StrConstType,
-		sys.FileoffType, sys.ResourceType, sys.VmaType, sys.PtrType:
+func (a *Arg) Size() uintptr {
+	switch typ := a.Type.(type) {
+	case *sys.IntType, *sys.LenType, *sys.FlagsType, *sys.ConstType,
+		*sys.ResourceType, *sys.VmaType, *sys.PtrType:
 		return typ.Size()
-	case sys.FilenameType:
-		return uintptr(len(a.Data))
-	case sys.BufferType:
+	case *sys.BufferType:
 		return uintptr(len(a.Data))
 	case *sys.StructType:
 		var size uintptr
-		for i, f := range typ1.Fields {
-			size += a.Inner[i].Size(f)
+		for _, fld := range a.Inner {
+			size += fld.Size()
 		}
 		return size
 	case *sys.UnionType:
-		return a.Option.Size(a.OptionType)
-	case sys.ArrayType:
+		return a.Option.Size()
+	case *sys.ArrayType:
 		var size uintptr
 		for _, in := range a.Inner {
-			size += in.Size(typ1.Type)
+			size += in.Size()
 		}
 		return size
 	default:
@@ -140,12 +125,12 @@ func (a *Arg) Size(typ sys.Type) uintptr {
 	}
 }
 
-func constArg(v uintptr) *Arg {
-	return &Arg{Kind: ArgConst, Val: v}
+func constArg(t sys.Type, v uintptr) *Arg {
+	return &Arg{Type: t, Kind: ArgConst, Val: v}
 }
 
-func resultArg(r *Arg) *Arg {
-	arg := &Arg{Kind: ArgResult, Res: r}
+func resultArg(t sys.Type, r *Arg) *Arg {
+	arg := &Arg{Type: t, Kind: ArgResult, Res: r}
 	if r.Uses == nil {
 		r.Uses = make(map[*Arg]bool)
 	}
@@ -156,28 +141,28 @@ func resultArg(r *Arg) *Arg {
 	return arg
 }
 
-func dataArg(data []byte) *Arg {
-	return &Arg{Kind: ArgData, Data: append([]byte{}, data...)}
+func dataArg(t sys.Type, data []byte) *Arg {
+	return &Arg{Type: t, Kind: ArgData, Data: append([]byte{}, data...)}
 }
 
-func pointerArg(page uintptr, off int, npages uintptr, obj *Arg) *Arg {
-	return &Arg{Kind: ArgPointer, AddrPage: page, AddrOffset: off, AddrPagesNum: npages, Res: obj}
+func pointerArg(t sys.Type, page uintptr, off int, npages uintptr, obj *Arg) *Arg {
+	return &Arg{Type: t, Kind: ArgPointer, AddrPage: page, AddrOffset: off, AddrPagesNum: npages, Res: obj}
 }
 
-func pageSizeArg(npages uintptr, off int) *Arg {
-	return &Arg{Kind: ArgPageSize, AddrPage: npages, AddrOffset: off}
+func pageSizeArg(t sys.Type, npages uintptr, off int) *Arg {
+	return &Arg{Type: t, Kind: ArgPageSize, AddrPage: npages, AddrOffset: off}
 }
 
-func groupArg(inner []*Arg) *Arg {
-	return &Arg{Kind: ArgGroup, Inner: inner}
+func groupArg(t sys.Type, inner []*Arg) *Arg {
+	return &Arg{Type: t, Kind: ArgGroup, Inner: inner}
 }
 
-func unionArg(opt *Arg, typ sys.Type) *Arg {
-	return &Arg{Kind: ArgUnion, Option: opt, OptionType: typ}
+func unionArg(t sys.Type, opt *Arg, typ sys.Type) *Arg {
+	return &Arg{Type: t, Kind: ArgUnion, Option: opt, OptionType: typ}
 }
 
-func returnArg() *Arg {
-	return &Arg{Kind: ArgReturn, Dir: DirOut}
+func returnArg(t sys.Type) *Arg {
+	return &Arg{Type: t, Kind: ArgReturn}
 }
 
 func (p *Prog) insertBefore(c *Call, calls []*Call) {
@@ -197,8 +182,8 @@ func (p *Prog) insertBefore(c *Call, calls []*Call) {
 	p.Calls = newCalls
 }
 
-// replaceArg replaces arg with arg1 in p, and inserts calls before arg call.
-func (p *Prog) replaceArg(arg, arg1 *Arg, calls []*Call) {
+// replaceArg replaces arg with arg1 in call c in program p, and inserts calls before arg call.
+func (p *Prog) replaceArg(c *Call, arg, arg1 *Arg, calls []*Call) {
 	if arg.Kind != ArgConst && arg.Kind != ArgResult && arg.Kind != ArgPointer && arg.Kind != ArgUnion {
 		panic(fmt.Sprintf("replaceArg: bad arg kind %v", arg.Kind))
 	}
@@ -209,10 +194,8 @@ func (p *Prog) replaceArg(arg, arg1 *Arg, calls []*Call) {
 		delete(arg.Res.Uses, arg)
 	}
 	for _, c := range calls {
-		assignTypeAndDir(c)
 		sanitizeCall(c)
 	}
-	c := arg.Call
 	p.insertBefore(c, calls)
 	// Somewhat hacky, but safe and preserves references to arg.
 	uses := arg.Uses
@@ -222,12 +205,11 @@ func (p *Prog) replaceArg(arg, arg1 *Arg, calls []*Call) {
 		delete(arg.Res.Uses, arg1)
 		arg.Res.Uses[arg] = true
 	}
-	assignTypeAndDir(c)
 	sanitizeCall(c)
 }
 
-// removeArg removes all references to/from arg0 from p.
-func (p *Prog) removeArg(arg0 *Arg) {
+// removeArg removes all references to/from arg0 of call c from p.
+func (p *Prog) removeArg(c *Call, arg0 *Arg) {
 	foreachSubarg(arg0, func(arg, _ *Arg, _ *[]*Arg) {
 		if arg.Kind == ArgResult {
 			if _, ok := arg.Res.Uses[arg]; !ok {
@@ -239,8 +221,8 @@ func (p *Prog) removeArg(arg0 *Arg) {
 			if arg1.Kind != ArgResult {
 				panic("use references not ArgResult")
 			}
-			arg2 := constArg(arg1.Type.Default())
-			p.replaceArg(arg1, arg2, nil)
+			arg2 := constArg(arg1.Type, arg1.Type.Default())
+			p.replaceArg(c, arg1, arg2, nil)
 		}
 	})
 }
@@ -251,7 +233,7 @@ func (p *Prog) removeCall(idx int) {
 	copy(p.Calls[idx:], p.Calls[idx+1:])
 	p.Calls = p.Calls[:len(p.Calls)-1]
 	for _, arg := range c.Args {
-		p.removeArg(arg)
+		p.removeArg(c, arg)
 	}
-	p.removeArg(c.Ret)
+	p.removeArg(c, c.Ret)
 }
diff --git a/prog/rand.go b/prog/rand.go
index 18dceeaea..eb24dcc4d 100644
--- a/prog/rand.go
+++ b/prog/rand.go
@@ -193,25 +193,25 @@ func (r *randGen) inport(s *state) uint16 {
 	return uint16(r.Intn(20))<<8 + 0xab
 }
 
-func (r *randGen) in6addr(s *state) (arg *Arg, calls []*Call) {
+func (r *randGen) in6addr(s *state, typ sys.Type) (arg *Arg, calls []*Call) {
 	// addr: loopback (big endian)
-	return groupArg([]*Arg{
-		constArg(0),
-		constArg(0),
-		constArg(0),
-		constArg(1 << 24),
+	return groupArg(typ, []*Arg{
+		constArg(nil, 0),
+		constArg(nil, 0),
+		constArg(nil, 0),
+		constArg(nil, 1<<24),
 	}), nil
 }
 
-func (r *randGen) inaddrany(s *state) (arg *Arg, calls []*Call) {
+func (r *randGen) inaddrany(s *state, typ sys.Type) (arg *Arg, calls []*Call) {
 	if r.bin() {
-		return r.in6addr(s)
+		return r.in6addr(s, typ)
 	} else {
-		return groupArg([]*Arg{
-			constArg(uintptr(r.inaddr(s))),
-			constArg(0),
-			constArg(0),
-			constArg(0),
+		return groupArg(typ, []*Arg{
+			constArg(nil, uintptr(r.inaddr(s))),
+			constArg(nil, 0),
+			constArg(nil, 0),
+			constArg(nil, 0),
 		}), nil
 	}
 }
@@ -258,7 +258,20 @@ func (r *randGen) sockaddr(s *state) []byte {
 	return data
 }
 
-func (r *randGen) randString(s *state) []byte {
+func (r *randGen) randString(s *state, vals []string, dir sys.Dir) []byte {
+	data := r.randStringImpl(s, vals)
+	if dir == sys.DirOut {
+		for i := range data {
+			data[i] = 0
+		}
+	}
+	return data
+}
+
+func (r *randGen) randStringImpl(s *state, vals []string) []byte {
+	if len(vals) != 0 {
+		return []byte(vals[r.Intn(len(vals))])
+	}
 	if len(s.strings) != 0 && r.bin() {
 		// Return an existing string.
 		strings := make([]string, 0, len(s.strings))
@@ -288,81 +301,43 @@ func (r *randGen) randString(s *state) []byte {
 	return buf.Bytes()
 }
 
-func (r *randGen) filesystem(s *state) []byte {
-	dict := []string{"sysfs", "rootfs", "ramfs", "tmpfs", "devtmpfs", "debugfs",
-		"securityfs", "sockfs", "pipefs", "anon_inodefs", "devpts", "ext3", "ext2", "ext4",
-		"hugetlbfs", "vfat", "ecryptfs", "kdbusfs", "fuseblk", "fuse", "rpc_pipefs",
-		"nfs", "nfs4", "nfsd", "binfmt_misc", "autofs", "xfs", "jfs", "msdos", "ntfs",
-		"minix", "hfs", "hfsplus", "qnx4", "ufs", "btrfs", "configfs", "ncpfs", "qnx6",
-		"exofs", "befs", "vxfs", "gfs2", "gfs2meta", "fusectl", "bfs", "nsfs", "efs",
-		"cifs", "efivarfs", "affs", "tracefs", "bdev", "ocfs2", "ocfs2_dlmfs", "hpfs",
-		"proc", "afs", "reiserfs", "jffs2", "romfs", "aio", "sysv", "v7", "udf",
-		"ceph", "pstore", "adfs", "9p", "hostfs", "squashfs", "cramfs", "iso9660",
-		"coda", "nilfs2", "logfs", "overlay", "f2fs", "omfs", "ubifs", "openpromfs"}
-	return []byte(dict[r.Intn(len(dict))] + "\x00")
-}
-
-func (r *randGen) algType(s *state) []byte {
-	dict := []string{"aead", "hash", "rng", "skcipher"}
-	res := make([]byte, 14)
-	copy(res, dict[r.Intn(len(dict))])
-	return res
-}
-
-func (r *randGen) algName(s *state) []byte {
-	dict := []string{"cmac(aes)", "ecb(aes)", "cbc(aes)", "hmac(sha1)", "pcbc(fcrypt)", "ghash",
-		"jitterentropy_rng", "stdrng", "stdrng", "stdrng", "stdrng", "hmac(sha256)", "stdrng",
-		"stdrng", "stdrng", "stdrng", "stdrng", "842", "lz4hc", "lz4", "lzo", "crct10dif", "crc32",
-		"crc32c", "michael_mic", "zlib", "deflate", "poly1305", "chacha20", "salsa20", "seed",
-		"anubis", "khazad", "xeta", "xtea", "tea", "ecb(arc4)", "arc4", "cast6", "cast5", "camellia",
-		"aes", "tnepres", "serpent", "twofish", "blowfish", "fcrypt", "des3_ede", "des", "tgr128",
-		"tgr160", "tgr192", "wp256", "wp384", "wp512", "sha384", "sha512", "sha224", "sha256",
-		"sha1", "rmd320", "rmd256", "rmd160", "rmd128", "md5", "md4", "digest_null", "compress_null",
-		"ecb(cipher_null)", "cipher_null", "rsa", "poly1305", "xts(serpent)", "lrw(serpent)",
-		"ctr(serpent)", "cbc(serpent)", "__ecb-serpent-sse2", "ecb(serpent)", "__xts-serpent-sse2",
-		"__lrw-serpent-sse2", "__ctr-serpent-sse2", "__cbc-serpent-sse2", "__ecb-serpent-sse2",
-		"salsa20", "xts(twofish)", "lrw(twofish)", "ctr(twofish)", "cbc(twofish)", "ecb(twofish)",
-		"twofish", "ctr(blowfish)", "cbc(blowfish)", "ecb(blowfish)", "blowfish", "xts(camellia)",
-		"lrw(camellia)", "ctr(camellia)", "cbc(camellia)", "ecb(camellia)", "camellia", "ctr(des3_ede)",
-		"cbc(des3_ede)", "ecb(des3_ede)", "des3_ede", "aes"}
-	res := make([]byte, 64)
-	copy(res, dict[r.Intn(len(dict))])
-	return res
-}
-
 func isSpecialStruct(typ sys.Type) func(r *randGen, s *state) (*Arg, []*Call) {
-	if _, ok := typ.(*sys.StructType); !ok {
+	a, ok := typ.(*sys.StructType)
+	if !ok {
 		panic("must be a struct")
 	}
 	switch typ.Name() {
 	case "timespec":
 		return func(r *randGen, s *state) (*Arg, []*Call) {
-			return r.timespec(s, false)
+			return r.timespec(s, a, false)
 		}
 	case "timeval":
 		return func(r *randGen, s *state) (*Arg, []*Call) {
-			return r.timespec(s, true)
+			return r.timespec(s, a, true)
 		}
 	case "in6_addr":
 		return func(r *randGen, s *state) (*Arg, []*Call) {
-			return r.in6addr(s)
+			return r.in6addr(s, a)
 		}
 	case "in_addr_any":
 		return func(r *randGen, s *state) (*Arg, []*Call) {
-			return r.inaddrany(s)
+			return r.inaddrany(s, a)
 		}
 	}
 	return nil
 }
 
-func (r *randGen) timespec(s *state, usec bool) (arg *Arg, calls []*Call) {
+func (r *randGen) timespec(s *state, typ *sys.StructType, usec bool) (arg *Arg, calls []*Call) {
 	// We need to generate timespec/timeval that are either (1) definitely in the past,
 	// or (2) definitely in unreachable fututre, or (3) few ms ahead of now.
 	// Note timespec/timeval can be absolute or relative to now.
 	r.choose(
 		1, func() {
 			// now for relative, past for absolute
-			arg = groupArg([]*Arg{constArg(0), constArg(0)})
+			arg = groupArg(typ, []*Arg{
+				constArg(typ.Fields[0], 0),
+				constArg(typ.Fields[1], 0),
+			})
 		},
 		1, func() {
 			// few ms ahead for relative, past for absolute
@@ -370,46 +345,77 @@ func (r *randGen) timespec(s *state, usec bool) (arg *Arg, calls []*Call) {
 			if usec {
 				nsec /= 1e3
 			}
-			arg = groupArg([]*Arg{constArg(0), constArg(nsec)})
+			arg = groupArg(typ, []*Arg{
+				constArg(typ.Fields[0], 0),
+				constArg(typ.Fields[1], nsec),
+			})
 		},
 		1, func() {
 			// unreachable fututre for both relative and absolute
-			arg = groupArg([]*Arg{constArg(2e9), constArg(0)})
+			arg = groupArg(typ, []*Arg{
+				constArg(typ.Fields[0], 2e9),
+				constArg(typ.Fields[1], 0),
+			})
 		},
 		1, func() {
 			// few ms ahead for absolute
-			tp := groupArg([]*Arg{constArg(0), constArg(0)})
+			meta := sys.CallMap["clock_gettime"]
+			ptrArgType := meta.Args[1].(*sys.PtrType)
+			argType := ptrArgType.Type.(*sys.StructType)
+			tp := groupArg(argType, []*Arg{
+				constArg(argType.Fields[0], 0),
+				constArg(argType.Fields[1], 0),
+			})
 			var tpaddr *Arg
-			tpaddr, calls = r.addr(s, 2*ptrSize, tp)
+			tpaddr, calls = r.addr(s, ptrArgType, 2*ptrSize, tp)
 			gettime := &Call{
-				Meta: sys.CallMap["clock_gettime"],
+				Meta: meta,
 				Args: []*Arg{
-					constArg(sys.CLOCK_REALTIME),
+					constArg(meta.Args[0], sys.CLOCK_REALTIME),
 					tpaddr,
 				},
+				Ret: returnArg(meta.Ret),
 			}
 			calls = append(calls, gettime)
-			sec := resultArg(tp.Inner[0])
-			nsec := resultArg(tp.Inner[1])
+			sec := resultArg(typ.Fields[0], tp.Inner[0])
+			nsec := resultArg(typ.Fields[1], tp.Inner[1])
 			if usec {
 				nsec.OpDiv = 1e3
 				nsec.OpAdd = 10 * 1e3
 			} else {
 				nsec.OpAdd = 10 * 1e6
 			}
-			arg = groupArg([]*Arg{sec, nsec})
+			arg = groupArg(typ, []*Arg{sec, nsec})
 		},
 	)
 	return
 }
 
-func (r *randGen) addr1(s *state, size uintptr, data *Arg) (*Arg, []*Call) {
+// createMmapCall creates a "normal" mmap call that maps [start, start+npages) page range.
+func createMmapCall(start, npages uintptr) *Call {
+	meta := sys.CallMap["mmap"]
+	mmap := &Call{
+		Meta: meta,
+		Args: []*Arg{
+			pointerArg(meta.Args[0], start, 0, npages, nil),
+			pageSizeArg(meta.Args[1], npages, 0),
+			constArg(meta.Args[2], sys.PROT_READ|sys.PROT_WRITE),
+			constArg(meta.Args[3], sys.MAP_ANONYMOUS|sys.MAP_PRIVATE|sys.MAP_FIXED),
+			constArg(meta.Args[4], sys.InvalidFD),
+			constArg(meta.Args[5], 0),
+		},
+		Ret: returnArg(meta.Ret),
+	}
+	return mmap
+}
+
+func (r *randGen) addr1(s *state, typ sys.Type, size uintptr, data *Arg) (*Arg, []*Call) {
 	npages := (size + pageSize - 1) / pageSize
 	if npages == 0 {
 		npages = 1
 	}
 	if r.oneOf(10) {
-		return r.randPageAddr(s, npages, data, false), nil
+		return r.randPageAddr(s, typ, npages, data, false), nil
 	}
 	for i := uintptr(0); i < maxPages-npages; i++ {
 		free := true
@@ -422,24 +428,14 @@ func (r *randGen) addr1(s *state, size uintptr, data *Arg) (*Arg, []*Call) {
 		if !free {
 			continue
 		}
-		c := &Call{
-			Meta: sys.CallMap["mmap"],
-			Args: []*Arg{
-				pointerArg(i, 0, npages, nil),
-				pageSizeArg(npages, 0),
-				constArg(sys.PROT_READ | sys.PROT_WRITE),
-				constArg(sys.MAP_ANONYMOUS | sys.MAP_PRIVATE | sys.MAP_FIXED),
-				constArg(sys.InvalidFD),
-				constArg(0),
-			},
-		}
-		return pointerArg(i, 0, 0, data), []*Call{c}
+		c := createMmapCall(i, npages)
+		return pointerArg(typ, i, 0, 0, data), []*Call{c}
 	}
-	return r.randPageAddr(s, npages, data, false), nil
+	return r.randPageAddr(s, typ, npages, data, false), nil
 }
 
-func (r *randGen) addr(s *state, size uintptr, data *Arg) (*Arg, []*Call) {
-	arg, calls := r.addr1(s, size, data)
+func (r *randGen) addr(s *state, typ sys.Type, size uintptr, data *Arg) (*Arg, []*Call) {
+	arg, calls := r.addr1(s, typ, size, data)
 	if arg.Kind != ArgPointer {
 		panic("bad")
 	}
@@ -457,7 +453,7 @@ func (r *randGen) addr(s *state, size uintptr, data *Arg) (*Arg, []*Call) {
 	return arg, calls
 }
 
-func (r *randGen) randPageAddr(s *state, npages uintptr, data *Arg, vma bool) *Arg {
+func (r *randGen) randPageAddr(s *state, typ sys.Type, npages uintptr, data *Arg, vma bool) *Arg {
 	var starts []uintptr
 	for i := uintptr(0); i < maxPages-npages; i++ {
 		busy := true
@@ -483,13 +479,13 @@ func (r *randGen) randPageAddr(s *state, npages uintptr, data *Arg, vma bool) *A
 	if !vma {
 		npages = 0
 	}
-	return pointerArg(page, 0, npages, data)
+	return pointerArg(typ, page, 0, npages, data)
 }
 
-func (r *randGen) createResource(s *state, res sys.ResourceType) (arg *Arg, calls []*Call) {
+func (r *randGen) createResource(s *state, res *sys.ResourceType) (arg *Arg, calls []*Call) {
 	if r.inCreateResource {
 		special := res.SpecialValues()
-		return constArg(special[r.Intn(len(special))]), nil
+		return constArg(res, special[r.Intn(len(special))]), nil
 	}
 	r.inCreateResource = true
 	defer func() { r.inCreateResource = false }()
@@ -516,7 +512,7 @@ func (r *randGen) createResource(s *state, res sys.ResourceType) (arg *Arg, call
 		metas = append(metas, meta)
 	}
 	if len(metas) == 0 {
-		return constArg(res.Default()), nil
+		return constArg(res, res.Default()), nil
 	}
 
 	// Now we have a set of candidate calls that can create the necessary resource.
@@ -535,7 +531,7 @@ func (r *randGen) createResource(s *state, res sys.ResourceType) (arg *Arg, call
 		}
 		if len(allres) != 0 {
 			// Bingo!
-			arg := resultArg(allres[r.Intn(len(allres))])
+			arg := resultArg(res, allres[r.Intn(len(allres))])
 			return arg, calls
 		}
 		switch meta.Name {
@@ -599,23 +595,25 @@ func (r *randGen) generateCall(s *state, p *Prog) []*Call {
 }
 
 func (r *randGen) generateParticularCall(s *state, meta *sys.Call) (calls []*Call) {
-	c := &Call{Meta: meta}
-	c.Args, calls = r.generateArgs(s, meta.Args, DirIn)
+	c := &Call{
+		Meta: meta,
+		Ret:  returnArg(meta.Ret),
+	}
+	c.Args, calls = r.generateArgs(s, meta.Args)
 	calls = append(calls, c)
 	for _, c1 := range calls {
-		assignTypeAndDir(c1)
 		sanitizeCall(c1)
 	}
 	return calls
 }
 
-func (r *randGen) generateArgs(s *state, types []sys.Type, dir ArgDir) ([]*Arg, []*Call) {
+func (r *randGen) generateArgs(s *state, types []sys.Type) ([]*Arg, []*Call) {
 	var calls []*Call
 	args := make([]*Arg, len(types))
 
 	// Generate all args. Size args have the default value 0 for now.
 	for i, typ := range types {
-		arg, calls1 := r.generateArg(s, typ, dir)
+		arg, calls1 := r.generateArg(s, typ)
 		if arg == nil {
 			panic(fmt.Sprintf("generated arg is nil for type '%v', types: %+v", typ.Name(), types))
 		}
@@ -623,36 +621,37 @@ func (r *randGen) generateArgs(s *state, types []sys.Type, dir ArgDir) ([]*Arg,
 		calls = append(calls, calls1...)
 	}
 
-	assignSizes(types, args)
+	assignSizes(args)
 
 	return args, calls
 }
 
-func (r *randGen) generateArg(s *state, typ sys.Type, dir ArgDir) (arg *Arg, calls []*Call) {
-	if dir == DirOut {
+func (r *randGen) generateArg(s *state, typ sys.Type) (arg *Arg, calls []*Call) {
+	if typ.Dir() == sys.DirOut {
 		// No need to generate something interesting for output scalar arguments.
 		// But we still need to generate the argument itself so that it can be referenced
 		// in subsequent calls. For the same reason we do generate pointer/array/struct
 		// output arguments (their elements can be referenced in subsequent calls).
 		switch typ.(type) {
-		case sys.IntType, sys.FlagsType, sys.ConstType, sys.StrConstType, sys.FileoffType, sys.ResourceType:
-			return constArg(0), nil
+		case *sys.IntType, *sys.FlagsType, *sys.ConstType,
+			*sys.ResourceType, *sys.VmaType:
+			return constArg(typ, 0), nil
 		}
 	}
 
 	if typ.Optional() && r.oneOf(5) {
-		if _, ok := typ.(sys.BufferType); ok {
+		if _, ok := typ.(*sys.BufferType); ok {
 			panic("impossible") // parent PtrType must be Optional instead
 		}
-		return constArg(typ.Default()), nil
+		return constArg(typ, typ.Default()), nil
 	}
 
 	switch a := typ.(type) {
-	case sys.ResourceType:
+	case *sys.ResourceType:
 		r.choose(
 			1, func() {
 				special := a.SpecialValues()
-				arg = constArg(special[r.Intn(len(special))])
+				arg = constArg(a, special[r.Intn(len(special))])
 			},
 			90, func() {
 				// Get an existing resource.
@@ -664,7 +663,7 @@ func (r *randGen) generateArg(s *state, typ sys.Type, dir ArgDir) (arg *Arg, cal
 					}
 				}
 				if len(allres) != 0 {
-					arg = resultArg(allres[r.Intn(len(allres))])
+					arg = resultArg(a, allres[r.Intn(len(allres))])
 				} else {
 					arg, calls = r.createResource(s, a)
 				}
@@ -675,16 +674,7 @@ func (r *randGen) generateArg(s *state, typ sys.Type, dir ArgDir) (arg *Arg, cal
 			},
 		)
 		return arg, calls
-	case sys.FileoffType:
-		// TODO: can do better
-		var arg *Arg
-		r.choose(
-			90, func() { arg = constArg(0) },
-			10, func() { arg = constArg(r.rand(100)) },
-			1, func() { arg = constArg(r.randInt()) },
-		)
-		return arg, nil
-	case sys.BufferType:
+	case *sys.BufferType:
 		switch a.Kind {
 		case sys.BufferBlobRand, sys.BufferBlobRange:
 			sz := r.randBufLen()
@@ -692,56 +682,38 @@ func (r *randGen) generateArg(s *state, typ sys.Type, dir ArgDir) (arg *Arg, cal
 				sz = r.randRange(int(a.RangeBegin), int(a.RangeEnd))
 			}
 			data := make([]byte, sz)
-			if dir != DirOut {
+			if a.Dir() != sys.DirOut {
 				for i := range data {
 					data[i] = byte(r.Intn(256))
 				}
 			}
-			return dataArg(data), nil
+			return dataArg(a, data), nil
 		case sys.BufferString:
-			data := r.randString(s)
-			return dataArg(data), nil
-		case sys.BufferFilesystem:
-			data := r.filesystem(s)
-			return dataArg(data), nil
+			data := r.randString(s, a.Values, a.Dir())
+			return dataArg(a, data), nil
+		case sys.BufferFilename:
+			filename := r.filename(s)
+			return dataArg(a, []byte(filename)), nil
 		case sys.BufferSockaddr:
 			data := r.sockaddr(s)
-			if dir == DirOut {
-				for i := range data {
-					data[i] = 0
-				}
-			}
-			return dataArg(data), nil
-		case sys.BufferAlgType:
-			data := r.algType(s)
-			if dir == DirOut {
-				for i := range data {
-					data[i] = 0
-				}
-			}
-			return dataArg(data), nil
-		case sys.BufferAlgName:
-			data := r.algName(s)
-			if dir == DirOut {
+			if a.Dir() == sys.DirOut {
 				for i := range data {
 					data[i] = 0
 				}
 			}
-			return dataArg(data), nil
+			return dataArg(a, data), nil
 		default:
 			panic("unknown buffer kind")
 		}
-	case sys.VmaType:
+	case *sys.VmaType:
 		npages := r.randPageCount()
-		arg := r.randPageAddr(s, npages, nil, true)
+		arg := r.randPageAddr(s, a, npages, nil, true)
 		return arg, nil
-	case sys.FlagsType:
-		return constArg(r.flags(a.Vals)), nil
-	case sys.ConstType:
-		return constArg(a.Val), nil
-	case sys.StrConstType:
-		return dataArg([]byte(a.Val)), nil
-	case sys.IntType:
+	case *sys.FlagsType:
+		return constArg(a, r.flags(a.Vals)), nil
+	case *sys.ConstType:
+		return constArg(a, a.Val), nil
+	case *sys.IntType:
 		v := r.randInt()
 		switch a.Kind {
 		case sys.IntSignalno:
@@ -750,14 +722,17 @@ func (r *randGen) generateArg(s *state, typ sys.Type, dir ArgDir) (arg *Arg, cal
 			v = uintptr(r.inaddr(s))
 		case sys.IntInport:
 			v = uintptr(r.inport(s))
+		case sys.IntFileoff:
+			r.choose(
+				90, func() { v = 0 },
+				10, func() { v = r.rand(100) },
+				1, func() { v = r.randInt() },
+			)
 		case sys.IntRange:
 			v = r.randRangeInt(a.RangeBegin, a.RangeEnd)
 		}
-		return constArg(v), nil
-	case sys.FilenameType:
-		filename := r.filename(s)
-		return dataArg([]byte(filename)), nil
-	case sys.ArrayType:
+		return constArg(a, v), nil
+	case *sys.ArrayType:
 		count := uintptr(0)
 		switch a.Kind {
 		case sys.ArrayRandLen:
@@ -768,28 +743,28 @@ func (r *randGen) generateArg(s *state, typ sys.Type, dir ArgDir) (arg *Arg, cal
 		var inner []*Arg
 		var calls []*Call
 		for i := uintptr(0); i < count; i++ {
-			arg1, calls1 := r.generateArg(s, a.Type, dir)
+			arg1, calls1 := r.generateArg(s, a.Type)
 			inner = append(inner, arg1)
 			calls = append(calls, calls1...)
 		}
-		return groupArg(inner), calls
+		return groupArg(a, inner), calls
 	case *sys.StructType:
-		if ctor := isSpecialStruct(a); ctor != nil && dir != DirOut {
+		if ctor := isSpecialStruct(a); ctor != nil && a.Dir() != sys.DirOut {
 			arg, calls = ctor(r, s)
 			return
 		}
-		args, calls := r.generateArgs(s, a.Fields, dir)
-		group := groupArg(args)
+		args, calls := r.generateArgs(s, a.Fields)
+		group := groupArg(a, args)
 		return group, calls
 	case *sys.UnionType:
 		optType := a.Options[r.Intn(len(a.Options))]
-		opt, calls := r.generateArg(s, optType, dir)
-		return unionArg(opt, optType), calls
-	case sys.PtrType:
-		inner, calls := r.generateArg(s, a.Type, ArgDir(a.Dir))
-		if ArgDir(a.Dir) == DirOut && inner == nil {
+		opt, calls := r.generateArg(s, optType)
+		return unionArg(a, opt, optType), calls
+	case *sys.PtrType:
+		inner, calls := r.generateArg(s, a.Type)
+		if a.Dir() == sys.DirOut && inner == nil {
 			// No data, but we should have got size.
-			arg, calls1 := r.addr(s, inner.Size(a.Type), nil)
+			arg, calls1 := r.addr(s, a, inner.Size(), nil)
 			calls = append(calls, calls1...)
 			return arg, calls
 		}
@@ -798,15 +773,15 @@ func (r *randGen) generateArg(s *state, typ sys.Type, dir ArgDir) (arg *Arg, cal
 			// So try to reuse a previously used address.
 			addrs := s.resources["iocbptr"]
 			addr := addrs[r.Intn(len(addrs))]
-			arg = pointerArg(addr.AddrPage, addr.AddrOffset, addr.AddrPagesNum, inner)
+			arg = pointerArg(a, addr.AddrPage, addr.AddrOffset, addr.AddrPagesNum, inner)
 			return arg, calls
 		}
-		arg, calls1 := r.addr(s, inner.Size(a.Type), inner)
+		arg, calls1 := r.addr(s, a, inner.Size(), inner)
 		calls = append(calls, calls1...)
 		return arg, calls
-	case sys.LenType:
+	case *sys.LenType:
 		// Return placeholder value of 0 while generating len args.
-		return constArg(0), nil
+		return constArg(a, 0), nil
 	default:
 		panic("unknown argument type")
 	}
diff --git a/prog/size_test.go b/prog/size_test.go
index 41068e713..ad1ba8740 100644
--- a/prog/size_test.go
+++ b/prog/size_test.go
@@ -16,7 +16,6 @@ func TestAssignSizeRandom(t *testing.T) {
 		data0 := p.Serialize()
 		for _, call := range p.Calls {
 			assignSizesCall(call)
-			assignTypeAndDir(call)
 		}
 		if data1 := p.Serialize(); !bytes.Equal(data0, data1) {
 			t.Fatalf("different lens assigned, initial: %v, new: %v", data0, data1)
@@ -26,7 +25,6 @@ func TestAssignSizeRandom(t *testing.T) {
 			data0 := p.Serialize()
 			for _, call := range p.Calls {
 				assignSizesCall(call)
-				assignTypeAndDir(call)
 			}
 			if data1 := p.Serialize(); !bytes.Equal(data0, data1) {
 				t.Fatalf("different lens assigned, initial: %v, new: %v", data0, data1)
@@ -113,7 +111,6 @@ func TestAssignSize(t *testing.T) {
 		}
 		for _, call := range p.Calls {
 			assignSizesCall(call)
-			assignTypeAndDir(call)
 		}
 		p1 := strings.TrimSpace(string(p.Serialize()))
 		if p1 != test.sizedProg {
diff --git a/prog/validation.go b/prog/validation.go
index a1b68ba1b..701d0ce3d 100644
--- a/prog/validation.go
+++ b/prog/validation.go
@@ -41,9 +41,6 @@ func (c *Call) validate(ctx *validCtx) error {
 		if arg == nil {
 			return fmt.Errorf("syscall %v: nil arg", c.Meta.Name)
 		}
-		if arg.Call != c {
-			return fmt.Errorf("syscall %v: arg has wrong call, call=%p, arg=%+v", c.Meta.Name, c, *arg)
-		}
 		if ctx.args[arg] {
 			return fmt.Errorf("syscall %v: arg is referenced several times in the tree", c.Meta.Name)
 		}
@@ -55,9 +52,9 @@ func (c *Call) validate(ctx *validCtx) error {
 			return fmt.Errorf("syscall %v: no type", c.Meta.Name)
 		}
 		if arg.Type.Name() != typ.Name() {
-			return fmt.Errorf("syscall %v: arg '%v' type mismatch", c.Meta.Name, typ.Name())
+			return fmt.Errorf("syscall %v: type name mismatch: %v vs %v", c.Meta.Name, arg.Type.Name(), typ.Name())
 		}
-		if arg.Dir == DirOut {
+		if arg.Type.Dir() == sys.DirOut {
 			if arg.Val != 0 || arg.AddrPage != 0 || arg.AddrOffset != 0 {
 				return fmt.Errorf("syscall %v: output arg '%v' has data", c.Meta.Name, typ.Name())
 			}
@@ -68,23 +65,17 @@ func (c *Call) validate(ctx *validCtx) error {
 			}
 		}
 		switch arg.Type.(type) {
-		case sys.ResourceType:
+		case *sys.ResourceType:
 			switch arg.Kind {
 			case ArgResult:
 			case ArgReturn:
 			case ArgConst:
-				if arg.Dir == DirOut && arg.Val != 0 {
+				if arg.Type.Dir() == sys.DirOut && arg.Val != 0 {
 					return fmt.Errorf("syscall %v: out resource arg '%v' has bad const value %v", c.Meta.Name, typ.Name(), arg.Val)
 				}
 			default:
 				return fmt.Errorf("syscall %v: fd arg '%v' has bad kind %v", c.Meta.Name, typ.Name(), arg.Kind)
 			}
-		case sys.FilenameType:
-			switch arg.Kind {
-			case ArgData:
-			default:
-				return fmt.Errorf("syscall %v: filename arg '%v' has bad kind %v", c.Meta.Name, typ.Name(), arg.Kind)
-			}
 		case *sys.StructType, *sys.ArrayType:
 			switch arg.Kind {
 			case ArgGroup:
@@ -105,25 +96,25 @@ func (c *Call) validate(ctx *validCtx) error {
 				return fmt.Errorf("syscall %v: result arg '%v' has no reference", c.Meta.Name, typ.Name())
 			}
 			if !ctx.args[arg.Res] {
-				return fmt.Errorf("syscall %v: result arg '%v' references out-of-tree result: %p%+v -> %v %p%+v",
-					c.Meta.Name, typ.Name(), arg, arg, arg.Res.Call.Meta.Name, arg.Res, arg.Res)
+				return fmt.Errorf("syscall %v: result arg '%v' references out-of-tree result: %p%+v -> %p%+v",
+					c.Meta.Name, typ.Name(), arg, arg, arg.Res, arg.Res)
 			}
 			if _, ok := arg.Res.Uses[arg]; !ok {
 				return fmt.Errorf("syscall %v: result arg '%v' has broken link (%+v)", c.Meta.Name, typ.Name(), arg.Res.Uses)
 			}
 		case ArgPointer:
-			if arg.Dir != DirIn {
-				return fmt.Errorf("syscall %v: pointer arg '%v' has output direction", c.Meta.Name, typ.Name())
-			}
 			switch typ1 := typ.(type) {
-			case sys.VmaType:
+			case *sys.VmaType:
 				if arg.Res != nil {
 					return fmt.Errorf("syscall %v: vma arg '%v' has data", c.Meta.Name, typ.Name())
 				}
 				if arg.AddrPagesNum == 0 {
 					return fmt.Errorf("syscall %v: vma arg '%v' has size 0", c.Meta.Name, typ.Name())
 				}
-			case sys.PtrType:
+			case *sys.PtrType:
+				if arg.Type.Dir() != sys.DirIn {
+					return fmt.Errorf("syscall %v: pointer arg '%v' has output direction", c.Meta.Name, typ.Name())
+				}
 				if arg.Res == nil && !typ.Optional() {
 					return fmt.Errorf("syscall %v: non optional pointer arg '%v' is nil", c.Meta.Name, typ.Name())
 				}
@@ -151,7 +142,7 @@ func (c *Call) validate(ctx *validCtx) error {
 						return err
 					}
 				}
-			case sys.ArrayType:
+			case *sys.ArrayType:
 				for _, arg1 := range arg.Inner {
 					if err := checkArg(arg1, typ1.Type); err != nil {
 						return err
@@ -185,7 +176,7 @@ func (c *Call) validate(ctx *validCtx) error {
 		return nil
 	}
 	for i, arg := range c.Args {
-		if c.Ret.Kind != ArgReturn {
+		if arg.Kind == ArgReturn {
 			return fmt.Errorf("syscall %v: arg '%v' has wrong return kind", c.Meta.Name, arg.Type.Name())
 		}
 		if err := checkArg(arg, c.Meta.Args[i]); err != nil {
diff --git a/sys/README.md b/sys/README.md
index 18b3c76ab..8125a7b7c 100644
--- a/sys/README.md
+++ b/sys/README.md
@@ -23,7 +23,7 @@ Pseudo-formal grammar of syscall description:
 	type = typename [ "[" type-options "]" ]
 	typename = "const" | "intN" | "intptr" | "flags" | "array" | "ptr" |
 			"buffer" | "string" | "strconst" | "filename" |
-			"fileoff" | "len" | "bytesize" | "vma"
+			"len" | "bytesize" | "vma"
 	type-options = [type-opt ["," type-opt]]
 ```
 common type-options include:
@@ -44,12 +44,12 @@ rest of the type-options are type-specific:
 		type of the object; direction (in/out/inout)
 	"buffer": a pointer to a memory buffer (like read/write buffer argument), type-options:
 		direction (in/out/inout)
-	"string": a pointer to a memory buffer, similar to buffer[in]
-	"strconst": a pointer to a constant string, type-options:
-		the underlying string (for example "/dev/dsp")
+	"string": a zero-terminated memory buffer (no pointer indirection implied), type-options:
+		either a string value in quotes for constant strings (e.g. "foo"),
+		or a reference to string flags,
+		optionally followed by a buffer size (string values will be padded with \x00 to that size)
 	"filename": a file/link/dir name
-	"fileoff": offset within a file, type-options:
-		argname of the file
+	"fileoff": offset within a file
 	"len": length of another field (for array it is number of elements), type-options:
 		argname of the object
 	"bytesize": similar to "len", but always denotes the size in bytes, type-options:
@@ -62,6 +62,10 @@ Flags are described as:
 ```
 	flagname = const ["," const]*
 ```
+or for string flags as:
+```
+	flagname = "\"" literal "\"" ["," "\"" literal "\""]*
+```
 
 ### Structs
 
diff --git a/sys/align.go b/sys/align.go
index 055a433f8..1b1ea66ac 100644
--- a/sys/align.go
+++ b/sys/align.go
@@ -7,9 +7,9 @@ func initAlign() {
 	var rec func(t Type)
 	rec = func(t Type) {
 		switch t1 := t.(type) {
-		case PtrType:
+		case *PtrType:
 			rec(t1.Type)
-		case ArrayType:
+		case *ArrayType:
 			rec(t1.Type)
 		case *StructType:
 			if !t1.padded {
@@ -49,10 +49,10 @@ func addAlignment(t *StructType) {
 			fields = append(fields, makePad(pad))
 		}
 		fields = append(fields, f)
-		if at, ok := f.(ArrayType); ok && (at.Kind == ArrayRandLen || (at.Kind == ArrayRangeLen && at.RangeBegin != at.RangeEnd)) {
+		if at, ok := f.(*ArrayType); ok && (at.Kind == ArrayRandLen || (at.Kind == ArrayRangeLen && at.RangeBegin != at.RangeEnd)) {
 			varLen = true
 		}
-		if at, ok := f.(BufferType); ok && (at.Kind == BufferBlobRand || (at.Kind == BufferBlobRange && at.RangeBegin != at.RangeEnd)) {
+		if at, ok := f.(*BufferType); ok && (at.Kind == BufferBlobRand || (at.Kind == BufferBlobRange && at.RangeBegin != at.RangeEnd)) {
 			varLen = true
 		}
 		if varLen && i != len(t.Fields)-1 {
@@ -71,7 +71,7 @@ func addAlignment(t *StructType) {
 }
 
 func makePad(sz uintptr) Type {
-	return ConstType{
+	return &ConstType{
 		TypeCommon: TypeCommon{TypeName: "pad", IsOptional: false},
 		TypeSize:   sz,
 		Val:        0,
diff --git a/sys/bpf.txt b/sys/bpf.txt
index 68b4c0ab9..e7338cc53 100644
--- a/sys/bpf.txt
+++ b/sys/bpf.txt
@@ -52,7 +52,7 @@ bpf_prog {
 	type	flags[bpf_prog_type, int32]
 	ninsn	len[insns, int32]
 	insns	ptr[in, array[bpf_insn]]
-	license	string
+	license	ptr[in, string]
 	loglev	int32
 	logsize	len[log, int32]
 	log	buffer[out]
diff --git a/sys/decl.go b/sys/decl.go
index 89773b0dd..84c2f8c08 100644
--- a/sys/decl.go
+++ b/sys/decl.go
@@ -19,17 +19,25 @@ type Call struct {
 	Ret      Type
 }
 
+type Dir int
+
+const (
+	DirIn Dir = iota
+	DirOut
+	DirInOut
+)
+
 type Type interface {
 	Name() string
+	Dir() Dir
 	Optional() bool
 	Default() uintptr
 	Size() uintptr
 	Align() uintptr
-	InnerType() Type // returns inner type for PtrType
 }
 
 func IsPad(t Type) bool {
-	if ct, ok := t.(ConstType); ok && ct.IsPad {
+	if ct, ok := t.(*ConstType); ok && ct.IsPad {
 		return true
 	}
 	return false
@@ -37,21 +45,26 @@ func IsPad(t Type) bool {
 
 type TypeCommon struct {
 	TypeName   string
+	ArgDir     Dir
 	IsOptional bool
 }
 
-func (t TypeCommon) Name() string {
+func (t *TypeCommon) Name() string {
 	return t.TypeName
 }
 
-func (t TypeCommon) Optional() bool {
+func (t *TypeCommon) Optional() bool {
 	return t.IsOptional
 }
 
-func (t TypeCommon) Default() uintptr {
+func (t *TypeCommon) Default() uintptr {
 	return 0
 }
 
+func (t TypeCommon) Dir() Dir {
+	return t.ArgDir
+}
+
 const (
 	InvalidFD = ^uintptr(0)
 )
@@ -68,55 +81,30 @@ type ResourceType struct {
 	Desc *ResourceDesc
 }
 
-func (t ResourceType) Default() uintptr {
+func (t *ResourceType) Default() uintptr {
 	return t.Desc.Values[0]
 }
 
-func (t ResourceType) SpecialValues() []uintptr {
+func (t *ResourceType) SpecialValues() []uintptr {
 	return t.Desc.Values
 }
 
-func (t ResourceType) Size() uintptr {
+func (t *ResourceType) Size() uintptr {
 	return t.Desc.Type.Size()
 }
 
-func (t ResourceType) Align() uintptr {
+func (t *ResourceType) Align() uintptr {
 	return t.Desc.Type.Align()
 }
 
-func (t ResourceType) InnerType() Type {
-	return t
-}
-
-type FileoffType struct {
-	TypeCommon
-	TypeSize  uintptr
-	BigEndian bool
-	File      string
-}
-
-func (t FileoffType) Size() uintptr {
-	return t.TypeSize
-}
-
-func (t FileoffType) Align() uintptr {
-	return t.Size()
-}
-
-func (t FileoffType) InnerType() Type {
-	return t
-}
-
 type BufferKind int
 
 const (
 	BufferBlobRand BufferKind = iota
 	BufferBlobRange
 	BufferString
+	BufferFilename
 	BufferSockaddr
-	BufferFilesystem
-	BufferAlgType
-	BufferAlgName
 )
 
 type BufferType struct {
@@ -124,48 +112,48 @@ type BufferType struct {
 	Kind       BufferKind
 	RangeBegin uintptr // for BufferBlobRange kind
 	RangeEnd   uintptr // for BufferBlobRange kind
+	SubKind    string
+	Values     []string // possible values for BufferString kind
 }
 
-func (t BufferType) Size() uintptr {
+func (t *BufferType) Size() uintptr {
 	switch t.Kind {
-	case BufferAlgType:
-		return 14
-	case BufferAlgName:
-		return 64
+	case BufferString:
+		size := 0
+		for _, s := range t.Values {
+			if size != 0 && size != len(s) {
+				size = 0
+				break
+			}
+			size = len(s)
+		}
+		if size != 0 {
+			return uintptr(size)
+		}
 	case BufferBlobRange:
 		if t.RangeBegin == t.RangeEnd {
 			return t.RangeBegin
 		}
-		fallthrough
-	default:
-		panic(fmt.Sprintf("buffer size is not statically known: %v", t.Name()))
 	}
+	panic(fmt.Sprintf("buffer size is not statically known: %v", t.Name()))
 }
 
-func (t BufferType) Align() uintptr {
+func (t *BufferType) Align() uintptr {
 	return 1
 }
 
-func (t BufferType) InnerType() Type {
-	return t
-}
-
 type VmaType struct {
 	TypeCommon
 }
 
-func (t VmaType) Size() uintptr {
+func (t *VmaType) Size() uintptr {
 	return ptrSize
 }
 
-func (t VmaType) Align() uintptr {
+func (t *VmaType) Align() uintptr {
 	return t.Size()
 }
 
-func (t VmaType) InnerType() Type {
-	return t
-}
-
 type LenType struct {
 	TypeCommon
 	TypeSize  uintptr
@@ -174,18 +162,14 @@ type LenType struct {
 	Buf       string
 }
 
-func (t LenType) Size() uintptr {
+func (t *LenType) Size() uintptr {
 	return t.TypeSize
 }
 
-func (t LenType) Align() uintptr {
+func (t *LenType) Align() uintptr {
 	return t.Size()
 }
 
-func (t LenType) InnerType() Type {
-	return t
-}
-
 type FlagsType struct {
 	TypeCommon
 	TypeSize  uintptr
@@ -193,18 +177,14 @@ type FlagsType struct {
 	Vals      []uintptr
 }
 
-func (t FlagsType) Size() uintptr {
+func (t *FlagsType) Size() uintptr {
 	return t.TypeSize
 }
 
-func (t FlagsType) Align() uintptr {
+func (t *FlagsType) Align() uintptr {
 	return t.Size()
 }
 
-func (t FlagsType) InnerType() Type {
-	return t
-}
-
 type ConstType struct {
 	TypeCommon
 	TypeSize  uintptr
@@ -213,36 +193,14 @@ type ConstType struct {
 	IsPad     bool
 }
 
-func (t ConstType) Size() uintptr {
+func (t *ConstType) Size() uintptr {
 	return t.TypeSize
 }
 
-func (t ConstType) Align() uintptr {
+func (t *ConstType) Align() uintptr {
 	return t.Size()
 }
 
-func (t ConstType) InnerType() Type {
-	return t
-}
-
-type StrConstType struct {
-	TypeCommon
-	TypeSize uintptr
-	Val      string
-}
-
-func (t StrConstType) Size() uintptr {
-	return uintptr(len(t.Val))
-}
-
-func (t StrConstType) Align() uintptr {
-	return 1
-}
-
-func (t StrConstType) InnerType() Type {
-	return t
-}
-
 type IntKind int
 
 const (
@@ -250,6 +208,7 @@ const (
 	IntSignalno
 	IntInaddr
 	IntInport
+	IntFileoff // offset within a file
 	IntRange
 )
 
@@ -262,34 +221,14 @@ type IntType struct {
 	RangeEnd   int64
 }
 
-func (t IntType) Size() uintptr {
+func (t *IntType) Size() uintptr {
 	return t.TypeSize
 }
 
-func (t IntType) Align() uintptr {
+func (t *IntType) Align() uintptr {
 	return t.Size()
 }
 
-func (t IntType) InnerType() Type {
-	return t
-}
-
-type FilenameType struct {
-	TypeCommon
-}
-
-func (t FilenameType) Size() uintptr {
-	panic("filename size is not statically known")
-}
-
-func (t FilenameType) Align() uintptr {
-	return 1
-}
-
-func (t FilenameType) InnerType() Type {
-	return t
-}
-
 type ArrayKind int
 
 const (
@@ -305,39 +244,30 @@ type ArrayType struct {
 	RangeEnd   uintptr
 }
 
-func (t ArrayType) Size() uintptr {
+func (t *ArrayType) Size() uintptr {
 	if t.RangeBegin == t.RangeEnd {
 		return t.RangeBegin * t.Type.Size()
 	}
 	return 0 // for trailing embed arrays
 }
 
-func (t ArrayType) Align() uintptr {
+func (t *ArrayType) Align() uintptr {
 	return t.Type.Align()
 }
 
-func (t ArrayType) InnerType() Type {
-	return t
-}
-
 type PtrType struct {
 	TypeCommon
 	Type Type
-	Dir  Dir
 }
 
-func (t PtrType) Size() uintptr {
+func (t *PtrType) Size() uintptr {
 	return ptrSize
 }
 
-func (t PtrType) Align() uintptr {
+func (t *PtrType) Align() uintptr {
 	return t.Size()
 }
 
-func (t PtrType) InnerType() Type {
-	return t.Type.InnerType()
-}
-
 type StructType struct {
 	TypeCommon
 	Fields []Type
@@ -370,10 +300,6 @@ func (t *StructType) Align() uintptr {
 	return align
 }
 
-func (t *StructType) InnerType() Type {
-	return t
-}
-
 type UnionType struct {
 	TypeCommon
 	Options []Type
@@ -403,18 +329,6 @@ func (t *UnionType) Align() uintptr {
 	return align
 }
 
-func (t *UnionType) InnerType() Type {
-	return t
-}
-
-type Dir int
-
-const (
-	DirIn Dir = iota
-	DirOut
-	DirInOut
-)
-
 var ctors = make(map[string][]*Call)
 
 // ResourceConstructors returns a list of calls that can create a resource of the given kind.
@@ -431,56 +345,20 @@ func initResources() {
 func resourceCtors(kind []string, precise bool) []*Call {
 	// Find calls that produce the necessary resources.
 	var metas []*Call
-	// Recurse into arguments to see if there is an out/inout arg of necessary type.
-	seen := make(map[Type]bool)
-	var checkArg func(typ Type, dir Dir) bool
-	checkArg = func(typ Type, dir Dir) bool {
-		if resarg, ok := typ.(ResourceType); ok && dir != DirIn && isCompatibleResource(kind, resarg.Desc.Kind, precise) {
-			return true
-		}
-		switch typ1 := typ.(type) {
-		case ArrayType:
-			if checkArg(typ1.Type, dir) {
-				return true
-			}
-		case *StructType:
-			if seen[typ1] {
-				return false // prune recursion via pointers to structs/unions
-			}
-			seen[typ1] = true
-			for _, fld := range typ1.Fields {
-				if checkArg(fld, dir) {
-					return true
-				}
-			}
-		case *UnionType:
-			if seen[typ1] {
-				return false // prune recursion via pointers to structs/unions
-			}
-			seen[typ1] = true
-			for _, opt := range typ1.Options {
-				if checkArg(opt, dir) {
-					return true
-				}
-			}
-		case PtrType:
-			if checkArg(typ1.Type, typ1.Dir) {
-				return true
-			}
-		}
-		return false
-	}
 	for _, meta := range Calls {
+		// Recurse into arguments to see if there is an out/inout arg of necessary type.
 		ok := false
-		for _, arg := range meta.Args {
-			if checkArg(arg, DirIn) {
-				ok = true
-				break
+		ForeachType(meta, func(typ Type) {
+			if ok {
+				return
 			}
-		}
-		if !ok && meta.Ret != nil && checkArg(meta.Ret, DirOut) {
-			ok = true
-		}
+			switch typ1 := typ.(type) {
+			case *ResourceType:
+				if typ1.Dir() != DirIn && isCompatibleResource(kind, typ1.Desc.Kind, precise) {
+					ok = true
+				}
+			}
+		})
 		if ok {
 			metas = append(metas, meta)
 		}
@@ -524,41 +402,16 @@ func isCompatibleResource(dst, src []string, precise bool) bool {
 	return true
 }
 
-func (c *Call) InputResources() []ResourceType {
-	var resources []ResourceType
-	seen := make(map[Type]bool)
-	var checkArg func(typ Type, dir Dir)
-	checkArg = func(typ Type, dir Dir) {
+func (c *Call) InputResources() []*ResourceType {
+	var resources []*ResourceType
+	ForeachType(c, func(typ Type) {
 		switch typ1 := typ.(type) {
-		case ResourceType:
-			if dir != DirOut && !typ1.IsOptional {
+		case *ResourceType:
+			if typ1.Dir() != DirOut && !typ1.IsOptional {
 				resources = append(resources, typ1)
 			}
-		case ArrayType:
-			checkArg(typ1.Type, dir)
-		case PtrType:
-			checkArg(typ1.Type, typ1.Dir)
-		case *StructType:
-			if seen[typ1] {
-				return // prune recursion via pointers to structs/unions
-			}
-			seen[typ1] = true
-			for _, fld := range typ1.Fields {
-				checkArg(fld, dir)
-			}
-		case *UnionType:
-			if seen[typ1] {
-				return // prune recursion via pointers to structs/unions
-			}
-			seen[typ1] = true
-			for _, opt := range typ1.Options {
-				checkArg(opt, dir)
-			}
 		}
-	}
-	for _, arg := range c.Args {
-		checkArg(arg, DirIn)
-	}
+	})
 	return resources
 }
 
@@ -598,6 +451,46 @@ func TransitivelyEnabledCalls(enabled map[*Call]bool) map[*Call]bool {
 	return supported
 }
 
+func ForeachType(meta *Call, f func(Type)) {
+	seen := make(map[Type]bool)
+	var rec func(t Type)
+	rec = func(t Type) {
+		f(t)
+		switch a := t.(type) {
+		case *PtrType:
+			rec(a.Type)
+		case *ArrayType:
+			rec(a.Type)
+		case *StructType:
+			if seen[a] {
+				return // prune recursion via pointers to structs/unions
+			}
+			seen[a] = true
+			for _, f := range a.Fields {
+				rec(f)
+			}
+		case *UnionType:
+			if seen[a] {
+				return // prune recursion via pointers to structs/unions
+			}
+			seen[a] = true
+			for _, opt := range a.Options {
+				rec(opt)
+			}
+		case *ResourceType, *BufferType, *VmaType, *LenType,
+			*FlagsType, *ConstType, *IntType:
+		default:
+			panic("unknown type")
+		}
+	}
+	for _, t := range meta.Args {
+		rec(t)
+	}
+	if meta.Ret != nil {
+		rec(meta.Ret)
+	}
+}
+
 var (
 	Calls     []*Call
 	CallCount int
diff --git a/sys/dri.txt b/sys/dri.txt
index 3c5753f23..bc35016e4 100644
--- a/sys/dri.txt
+++ b/sys/dri.txt
@@ -10,9 +10,9 @@ resource drm_agp_handle[intptr]
 resource drm_gem_handle[int32]
 resource drm_gem_name[int32]
 
-syz_open_dev$dri(dev strconst["/dev/dri/card#"], id intptr, flags flags[open_flags]) fd_dri
-syz_open_dev$dricontrol(dev strconst["/dev/dri/controlD#"], id intptr, flags flags[open_flags]) fd_dri
-syz_open_dev$drirender(dev strconst["/dev/dri/renderD#"], id intptr, flags flags[open_flags]) fd_dri
+syz_open_dev$dri(dev ptr[in, string["/dev/dri/card#"]], id intptr, flags flags[open_flags]) fd_dri
+syz_open_dev$dricontrol(dev ptr[in, string["/dev/dri/controlD#"]], id intptr, flags flags[open_flags]) fd_dri
+syz_open_dev$drirender(dev ptr[in, string["/dev/dri/renderD#"]], id intptr, flags flags[open_flags]) fd_dri
 
 ioctl$DRM_IOCTL_VERSION(fd fd_dri, cmd const[DRM_IOCTL_VERSION], arg ptr[in, drm_version])
 ioctl$DRM_IOCTL_GET_UNIQUE(fd fd_dri, cmd const[DRM_IOCTL_GET_UNIQUE], arg ptr[in, drm_unique_out])
diff --git a/sys/input.txt b/sys/input.txt
index 236d6c89c..4266c2b2b 100644
--- a/sys/input.txt
+++ b/sys/input.txt
@@ -6,10 +6,10 @@ include <linux/input.h>
 resource fd_evdev[fd]
 
 # There seems to be nothing special we can do with this fd.
-syz_open_dev$mouse(dev strconst["/dev/input/mouse#"], id intptr, flags flags[open_flags]) fd
-syz_open_dev$mice(dev strconst["/dev/input/mice"], id const[0], flags flags[open_flags]) fd
+syz_open_dev$mouse(dev ptr[in, string["/dev/input/mouse#"]], id intptr, flags flags[open_flags]) fd
+syz_open_dev$mice(dev ptr[in, string["/dev/input/mice"]], id const[0], flags flags[open_flags]) fd
 
-syz_open_dev$evdev(dev strconst["/dev/input/event#"], id intptr, flags flags[open_flags]) fd_evdev
+syz_open_dev$evdev(dev ptr[in, string["/dev/input/event#"]], id intptr, flags flags[open_flags]) fd_evdev
 
 write$evdev(fd fd_evdev, data ptr[in, array[input_event]], len bytesize[data])
 
diff --git a/sys/kdbus.txt b/sys/kdbus.txt
index 5d40b8625..97bd49e70 100644
--- a/sys/kdbus.txt
+++ b/sys/kdbus.txt
@@ -6,7 +6,7 @@ include <uapi/linux/fcntl.h>
 
 resource fd_kdbus[fd]
 
-openat$kdbus(fd const[AT_FDCWD], file strconst["/dev/kdbus"], flags flags[open_flags], mode const[0]) fd_kdbus
+openat$kdbus(fd const[AT_FDCWD], file ptr[in, string["/dev/kdbus"]], flags flags[open_flags], mode const[0]) fd_kdbus
 ioctl$kdbus_bus_make(fd fd_kdbus, cmd const[KDBUS_CMD_BUS_MAKE], arg ptr[in, kdbus_cmd_bus_make])
 ioctl$kdbus_ep_make(fd fd_kdbus, cmd const[KDBUS_CMD_ENDPOINT_MAKE], arg ptr[in, kdbus_cmd_ep_make])
 ioctl$kdbus_ep_update(fd fd_kdbus, cmd const[KDBUS_CMD_ENDPOINT_UPDATE], arg ptr[in, kdbus_cmd_ep_update])
diff --git a/sys/key.txt b/sys/key.txt
index 6c431682c..c0b18f5e8 100644
--- a/sys/key.txt
+++ b/sys/key.txt
@@ -6,17 +6,17 @@ include <uapi/linux/keyctl.h>
 
 resource key[int32]: KEY_SPEC_THREAD_KEYRING, KEY_SPEC_PROCESS_KEYRING, KEY_SPEC_SESSION_KEYRING, KEY_SPEC_USER_KEYRING, KEY_SPEC_USER_SESSION_KEYRING, KEY_SPEC_GROUP_KEYRING, KEY_SPEC_REQKEY_AUTH_KEY, KEY_SPEC_REQUESTOR_KEYRING
 
-add_key(type string, desc string, payload buffer[in, opt], paylen len[payload], keyring flags[keyring_type]) key
-request_key(type string, desc string, callout string, keyring flags[keyring_type]) key
+add_key(type ptr[in, string], desc ptr[in, string], payload buffer[in, opt], paylen len[payload], keyring flags[keyring_type]) key
+request_key(type ptr[in, string], desc ptr[in, string], callout ptr[in, string], keyring flags[keyring_type]) key
 keyctl$get_keyring_id(code const[KEYCTL_GET_KEYRING_ID], key key, create intptr)
-keyctl$join(code const[KEYCTL_JOIN_SESSION_KEYRING], session string)
+keyctl$join(code const[KEYCTL_JOIN_SESSION_KEYRING], session ptr[in, string])
 keyctl$update(code const[KEYCTL_UPDATE], key key, payload buffer[in, opt], paylen len[payload])
 keyctl$revoke(code const[KEYCTL_REVOKE], key key)
 keyctl$describe(code const[KEYCTL_DESCRIBE], key key, desc buffer[out], len len[desc])
 keyctl$clear(code const[KEYCTL_CLEAR], key key)
 keyctl$link(code const[KEYCTL_LINK], key1 key, key2 key)
 keyctl$unlink(code const[KEYCTL_UNLINK], key1 key, key2 key)
-keyctl$search(code const[KEYCTL_SEARCH], key key, type string, desc string, ring key)
+keyctl$search(code const[KEYCTL_SEARCH], key key, type ptr[in, string], desc ptr[in, string], ring key)
 keyctl$read(code const[KEYCTL_READ], key key, payload buffer[out], len len[payload])
 keyctl$chown(code const[KEYCTL_CHOWN], key key, uid uid, gid gid)
 # perm is a mask of KEY_POS_VIEW, etc consants, but they cover almost whole int32.
diff --git a/sys/kvm.txt b/sys/kvm.txt
index b80f4ce72..96e73d74e 100644
--- a/sys/kvm.txt
+++ b/sys/kvm.txt
@@ -9,7 +9,7 @@ resource fd_kvm[fd]
 resource fd_kvmvm[fd]
 resource fd_kvmcpu[fd]
 
-syz_open_dev$kvm(dev strconst["/dev/kvm"], id const[0], flags flags[open_flags]) fd_kvm
+syz_open_dev$kvm(dev ptr[in, string["/dev/kvm"]], id const[0], flags flags[open_flags]) fd_kvm
 
 ioctl$KVM_CREATE_VM(fd fd_kvm, cmd const[KVM_CREATE_VM], type const[0]) fd_kvmvm
 ioctl$KVM_GET_MSR_INDEX_LIST(fd fd_kvm, cmd const[KVM_GET_MSR_INDEX_LIST], arg ptr[in, kvm_msr_list])
@@ -99,7 +99,7 @@ ioctl$KVM_SET_GUEST_DEBUG(fd fd_kvmcpu, cmd const[KVM_SET_GUEST_DEBUG], arg ptr[
 ioctl$KVM_SMI(fd fd_kvmcpu, cmd const[KVM_SMI])
 
 # TODO: extend support (there are some ioctls)
-openat$xenevtchn(fd const[AT_FDCWD], file strconst["/dev/xen/evtchn"], flags flags[open_flags], mode const[0]) fd
+openat$xenevtchn(fd const[AT_FDCWD], file ptr[in, string["/dev/xen/evtchn"]], flags flags[open_flags], mode const[0]) fd
 
 kvm_mem_region_flags = KVM_MEM_LOG_DIRTY_PAGES, KVM_MEM_READONLY, KVM_MEMSLOT_INVALID, KVM_MEMSLOT_INCOHERENT
 kvm_mp_state = KVM_MP_STATE_RUNNABLE, KVM_MP_STATE_UNINITIALIZED, KVM_MP_STATE_INIT_RECEIVED, KVM_MP_STATE_HALTED, KVM_MP_STATE_SIPI_RECEIVED, KVM_MP_STATE_STOPPED, KVM_MP_STATE_CHECK_STOP, KVM_MP_STATE_OPERATING, KVM_MP_STATE_LOAD
diff --git a/sys/perf.txt b/sys/perf.txt
index a860d75c8..e35ad22b9 100644
--- a/sys/perf.txt
+++ b/sys/perf.txt
@@ -15,7 +15,7 @@ ioctl$PERF_EVENT_IOC_REFRESH(fd fd_perf, cmd const[PERF_EVENT_IOC_REFRESH], refr
 ioctl$PERF_EVENT_IOC_PERIOD(fd fd_perf, cmd const[PERF_EVENT_IOC_PERIOD], period ptr[in, int64])
 ioctl$PERF_EVENT_IOC_ID(fd fd_perf, cmd const[PERF_EVENT_IOC_ID], id ptr[out, int64])
 ioctl$PERF_EVENT_IOC_SET_OUTPUT(fd fd_perf, cmd const[PERF_EVENT_IOC_SET_OUTPUT], other fd_perf)
-ioctl$PERF_EVENT_IOC_SET_FILTER(fd fd_perf, cmd const[PERF_EVENT_IOC_SET_FILTER], filter string)
+ioctl$PERF_EVENT_IOC_SET_FILTER(fd fd_perf, cmd const[PERF_EVENT_IOC_SET_FILTER], filter ptr[in, string])
 ioctl$PERF_EVENT_IOC_SET_BPF(fd fd_perf, cmd const[PERF_EVENT_IOC_SET_BPF], prog fd_bpf_prog)
 
 perf_flags = PERF_FLAG_FD_NO_GROUP, PERF_FLAG_FD_OUTPUT, PERF_FLAG_PID_CGROUP, PERF_FLAG_FD_CLOEXEC
diff --git a/sys/random.txt b/sys/random.txt
index 7c8fd11c0..234d1be40 100755
--- a/sys/random.txt
+++ b/sys/random.txt
@@ -5,8 +5,8 @@ include <linux/random.h>
 
 resource fd_random[fd]
 
-syz_open_dev$random(dev strconst["/dev/random"], id const[0], flags flags[open_flags]) fd_random
-syz_open_dev$urandom(dev strconst["/dev/urandom"], id const[0], flags flags[open_flags]) fd_random
+syz_open_dev$random(dev ptr[in, string["/dev/random"]], id const[0], flags flags[open_flags]) fd_random
+syz_open_dev$urandom(dev ptr[in, string["/dev/urandom"]], id const[0], flags flags[open_flags]) fd_random
 
 ioctl$RNDGETENTCNT(fd fd_random, cmd const[RNDGETENTCNT], arg ptr[out, int32])
 ioctl$RNDADDTOENTCNT(fd fd_random, cmd const[RNDADDTOENTCNT], arg ptr[in, int32])
diff --git a/sys/sndcontrol.txt b/sys/sndcontrol.txt
index 20d5cc320..1ec602f03 100644
--- a/sys/sndcontrol.txt
+++ b/sys/sndcontrol.txt
@@ -5,7 +5,7 @@ include <sound/asound.h>
 
 resource fd_sndctrl[fd]
 
-syz_open_dev$sndctrl(dev strconst["/dev/snd/controlC#"], id intptr, flags flags[open_flags]) fd_sndctrl
+syz_open_dev$sndctrl(dev ptr[in, string["/dev/snd/controlC#"]], id intptr, flags flags[open_flags]) fd_sndctrl
 
 ioctl$SNDRV_CTL_IOCTL_PVERSION(fd fd_sndctrl, cmd const[SNDRV_CTL_IOCTL_PVERSION], arg buffer[out])
 ioctl$SNDRV_CTL_IOCTL_CARD_INFO(fd fd_sndctrl, cmd const[SNDRV_CTL_IOCTL_CARD_INFO], arg buffer[out])
@@ -61,7 +61,7 @@ snd_ctl_elem_info {
 	items	int32
 	item	int32
 	name	array[int8, 64]
-	nameptr	string
+	nameptr	ptr[in, string]
 	namelen	len[nameptr, int32]
 	pad1	array[const[0, int8], 44]
 	d	array[int16, 4]
diff --git a/sys/sndseq.txt b/sys/sndseq.txt
index 62a844ed7..40ad7118d 100644
--- a/sys/sndseq.txt
+++ b/sys/sndseq.txt
@@ -6,7 +6,7 @@ include <sound/asequencer.h>
 
 resource fd_sndseq[fd]
 
-syz_open_dev$sndseq(dev strconst["/dev/snd/seq"], id const[0], flags flags[open_flags]) fd_sndseq
+syz_open_dev$sndseq(dev ptr[in, string["/dev/snd/seq"]], id const[0], flags flags[open_flags]) fd_sndseq
 write$sndseq(fd fd_sndseq, data ptr[in, array[snd_seq_event]], len bytesize[data])
 
 ioctl$SNDRV_SEQ_IOCTL_PVERSION(fd fd_sndseq, cmd const[SNDRV_SEQ_IOCTL_PVERSION], arg ptr[out, int32])
diff --git a/sys/sndtimer.txt b/sys/sndtimer.txt
index 67e0a13a8..f7eebc2af 100644
--- a/sys/sndtimer.txt
+++ b/sys/sndtimer.txt
@@ -5,7 +5,7 @@ include <sound/asound.h>
 
 resource fd_sndtimer[fd]
 
-syz_open_dev$sndtimer(dev strconst["/dev/snd/timer"], id const[0], flags flags[open_flags]) fd_sndtimer
+syz_open_dev$sndtimer(dev ptr[in, string["/dev/snd/timer"]], id const[0], flags flags[open_flags]) fd_sndtimer
 
 ioctl$SNDRV_TIMER_IOCTL_PVERSION(fd fd_sndtimer, cmd const[SNDRV_TIMER_IOCTL_PVERSION], arg ptr[out, int32])
 ioctl$SNDRV_TIMER_IOCTL_NEXT_DEVICE(fd fd_sndtimer, cmd const[SNDRV_TIMER_IOCTL_NEXT_DEVICE], arg ptr[in, snd_timer_id])
diff --git a/sys/socket.txt b/sys/socket.txt
index b2db95849..74728194f 100644
--- a/sys/socket.txt
+++ b/sys/socket.txt
@@ -46,7 +46,7 @@ ioctl$SIOCINQ(fd sock, cmd const[SIOCINQ], arg ptr[out, int32])
 setsockopt$sock_void(fd sock, level const[SOL_SOCKET], optname flags[sockopt_opt_sock_void], optval const[0], optlen const[0])
 getsockopt$sock_int(fd sock, level const[SOL_SOCKET], optname flags[sockopt_opt_sock_int], optval ptr[out, int32], optlen ptr[inout, len[optval, int32]])
 setsockopt$sock_int(fd sock, level const[SOL_SOCKET], optname flags[sockopt_opt_sock_int], optval ptr[in, int32], optlen len[optval])
-setsockopt$sock_str(fd sock, level const[SOL_SOCKET], optname const[SO_BINDTODEVICE], optval string, optlen len[optval])
+setsockopt$sock_str(fd sock, level const[SOL_SOCKET], optname const[SO_BINDTODEVICE], optval ptr[in, string], optlen len[optval])
 getsockopt$sock_linger(fd sock, level const[SOL_SOCKET], optname const[SO_LINGER], optval ptr[out, linger], optlen ptr[inout, len[optval, int32]])
 setsockopt$sock_linger(fd sock, level const[SOL_SOCKET], optname const[SO_LINGER], optval ptr[in, linger], optlen len[optval])
 getsockopt$sock_cred(fd sock, level const[SOL_SOCKET], optname const[SO_PEERCRED], optval ptr[out, ucred], optlen ptr[inout, len[optval, int32]])
@@ -273,10 +273,10 @@ sendmmsg$alg(fd sock_algconn, mmsg ptr[in, array[msghdr_alg]], vlen len[mmsg], f
 
 sockaddr_alg {
 	family	const[AF_ALG, int16]
-	type	salg_type
+	type	string[salg_type, 14]
 	feat	flags[af_alg_type, int32]
 	mask	flags[af_alg_type, int32]
-	name	salg_name
+	name	string[salg_name, 64]
 }
 
 msghdr_alg {
@@ -320,6 +320,9 @@ cmsghdr_alg_assoc {
 
 af_alg_type = CRYPTO_ALG_TYPE_MASK, CRYPTO_ALG_TYPE_CIPHER, CRYPTO_ALG_TYPE_COMPRESS, CRYPTO_ALG_TYPE_AEAD, CRYPTO_ALG_TYPE_BLKCIPHER, CRYPTO_ALG_TYPE_ABLKCIPHER, CRYPTO_ALG_TYPE_GIVCIPHER, CRYPTO_ALG_TYPE_DIGEST, CRYPTO_ALG_TYPE_HASH, CRYPTO_ALG_TYPE_SHASH, CRYPTO_ALG_TYPE_AHASH, CRYPTO_ALG_TYPE_RNG, CRYPTO_ALG_TYPE_AKCIPHER, CRYPTO_ALG_TYPE_PCOMPRESS, CRYPTO_ALG_LARVAL, CRYPTO_ALG_DEAD, CRYPTO_ALG_DYING, CRYPTO_ALG_ASYNC, CRYPTO_ALG_NEED_FALLBACK, CRYPTO_ALG_GENIV, CRYPTO_ALG_TESTED, CRYPTO_ALG_INSTANCE, CRYPTO_ALG_KERN_DRIVER_ONLY, CRYPTO_ALG_INTERNAL
 
+salg_type = "aead", "hash", "rng", "skcipher"
+salg_name = "cmac(aes)", "ecb(aes)", "cbc(aes)", "hmac(sha1)", "pcbc(fcrypt)", "ghash", "jitterentropy_rng", "stdrng", "stdrng", "stdrng", "stdrng", "hmac(sha256)", "stdrng", "stdrng", "stdrng", "stdrng", "stdrng", "842", "lz4hc", "lz4", "lzo", "crct10dif", "crc32", "crc32c", "michael_mic", "zlib", "deflate", "poly1305", "chacha20", "salsa20", "seed", "anubis", "khazad", "xeta", "xtea", "tea", "ecb(arc4)", "arc4", "cast6", "cast5", "camellia", "aes", "tnepres", "serpent", "twofish", "blowfish", "fcrypt", "des3_ede", "des", "tgr128", "tgr160", "tgr192", "wp256", "wp384", "wp512", "sha384", "sha512", "sha224", "sha256", "sha1", "rmd320", "rmd256", "rmd160", "rmd128", "md5", "md4", "digest_null", "compress_null", "ecb(cipher_null)", "cipher_null", "rsa", "poly1305", "xts(serpent)", "lrw(serpent)", "ctr(serpent)", "cbc(serpent)", "__ecb-serpent-sse2", "ecb(serpent)", "__xts-serpent-sse2", "__lrw-serpent-sse2", "__ctr-serpent-sse2", "__cbc-serpent-sse2", "__ecb-serpent-sse2", "salsa20", "xts(twofish)", "lrw(twofish)", "ctr(twofish)", "cbc(twofish)", "ecb(twofish)", "twofish", "ctr(blowfish)", "cbc(blowfish)", "ecb(blowfish)", "blowfish", "xts(camellia)", "lrw(camellia)", "ctr(camellia)", "cbc(camellia)", "ecb(camellia)", "camellia", "ctr(des3_ede)", "cbc(des3_ede)", "ecb(des3_ede)", "des3_ede", "aes"
+
 
 
 
diff --git a/sys/sys.txt b/sys/sys.txt
index be0d10860..c6da9a800 100644
--- a/sys/sys.txt
+++ b/sys/sys.txt
@@ -79,14 +79,14 @@ openat(fd fd_dir, file filename, flags flags[open_flags], mode flags[open_mode])
 creat(file filename, mode flags[open_mode]) fd
 close(fd fd)
 read(fd fd, buf buffer[out], count len[buf]) len[buf]
-pread64(fd fd, buf buffer[out], count len[buf], pos fileoff[fd])
+pread64(fd fd, buf buffer[out], count len[buf], pos fileoff)
 readv(fd fd, vec ptr[in, array[iovec_out]], vlen len[vec])
-preadv(fd fd, vec ptr[in, array[iovec_out]], vlen len[vec], off fileoff[fd])
+preadv(fd fd, vec ptr[in, array[iovec_out]], vlen len[vec], off fileoff)
 write(fd fd, buf buffer[in], count len[buf]) len[buf]
-pwrite64(fd fd, buf buffer[in], count len[buf], pos fileoff[fd])
+pwrite64(fd fd, buf buffer[in], count len[buf], pos fileoff)
 writev(fd fd, vec ptr[in, array[iovec_in]], vlen len[vec])
-pwritev(fd fd, vec ptr[in, array[iovec_in]], vlen len[vec], off fileoff[fd])
-lseek(fd fd, offset fileoff[fd], whence flags[seek_whence])
+pwritev(fd fd, vec ptr[in, array[iovec_in]], vlen len[vec], off fileoff)
+lseek(fd fd, offset fileoff, whence flags[seek_whence])
 
 dup(oldfd fd) fd
 dup2(oldfd fd, newfd fd) fd
@@ -96,9 +96,9 @@ pipe(pipefd ptr[out, pipefd])
 pipe2(pipefd ptr[out, pipefd], flags flags[pipe_flags])
 
 tee(fdin fd, fdout fd, len int64, f flags[splice_flags])
-splice(fdin fd, offin fileoff[fdin], fdout fd, offout fileoff[fdout], len int64, f flags[splice_flags])
+splice(fdin fd, offin fileoff, fdout fd, offout fileoff, len int64, f flags[splice_flags])
 vmsplice(fd fd, vec ptr[in, array[iovec_in]], vlen len[vec], f flags[splice_flags])
-sendfile(fdout fd, fdin fd, off ptr[inout, fileoff[fdin, int64], opt], count int64)
+sendfile(fdout fd, fdin fd, off ptr[inout, fileoff[int64], opt], count int64)
 
 stat(file filename, statbuf ptr[out, stat])
 lstat(file filename, statbuf ptr[out, stat])
@@ -136,14 +136,14 @@ ioctl$UFFDIO_WAKE(fd fd_uffd, cmd const[UFFDIO_WAKE], arg ptr[in, uffdio_range])
 ioctl$UFFDIO_COPY(fd fd_uffd, cmd const[UFFDIO_WAKE], arg ptr[in, uffdio_range])
 ioctl$UFFDIO_ZEROPAGE(fd fd_uffd, cmd const[UFFDIO_WAKE], arg ptr[in, uffdio_range])
 
-mmap(addr vma, len len[addr], prot flags[mmap_prot], flags flags[mmap_flags], fd fd, offset fileoff[fd]) vma
+mmap(addr vma, len len[addr], prot flags[mmap_prot], flags flags[mmap_flags], fd fd, offset fileoff) vma
 munmap(addr vma, len len[addr])
 mremap(addr vma, len len[addr], newlen len[newaddr], flags flags[mremap_flags], newaddr vma) vma
 remap_file_pages(addr vma, size len[addr], prot flags[mmap_prot], pgoff intptr, flags flags[mmap_flags])
 mprotect(addr vma, len len[addr], prot flags[mmap_prot])
 msync(addr vma, len len[addr], f flags[msync_flags])
 madvise(addr vma, len len[addr], advice flags[madvise_flags])
-fadvise64(fd fd, offset fileoff[fd], len intptr, advice flags[fadvise_flags])
+fadvise64(fd fd, offset fileoff, len intptr, advice flags[fadvise_flags])
 readahead(fd fd, off intptr, count intptr)
 mbind(addr vma, len len[addr], mode flags[mbind_mode], nodemask ptr[in, int64], maxnode intptr, flags flags[mbind_flags])
 move_pages(pid pid, nr len[pages], pages ptr[in, array[vma]], nodes ptr[in, array[int32], opt], status ptr[out, array[int32]], flags flags[move_pages_flags])
@@ -156,7 +156,7 @@ mlock2(addr vma, size len[addr], flags flags[mlock_flags])
 munlock(addr vma, size len[addr])
 mlockall(flags flags[mlockall_flags])
 munlockall()
-memfd_create(name string, flags flags[memfd_flags]) fd
+memfd_create(name ptr[in, string], flags flags[memfd_flags]) fd
 unshare(flags flags[clone_flags])
 kcmp(pid1 pid, pid2 pid, type flags[kcmp_flags], fd1 fd, fd2 fd)
 
@@ -220,7 +220,7 @@ prctl$intptr(option flags[prctl_code_intptr], arg intptr)
 prctl$getreaper(option flags[prctl_code_getreaper], arg ptr[out, intptr])
 prctl$setendian(option const[PR_SET_ENDIAN], arg flags[prctl_endian])
 prctl$setfpexc(option const[PR_SET_FPEXC], arg flags[prctl_fpexc])
-prctl$setname(option const[PR_SET_NAME], name string)
+prctl$setname(option const[PR_SET_NAME], name ptr[in, string])
 prctl$getname(option const[PR_GET_NAME], name buffer[out])
 prctl$setptracer(option const[PR_SET_PTRACER], pid pid)
 prctl$seccomp(option const[PR_SET_SECCOMP], mode flags[prctl_seccomp_mode], prog ptr[in, sock_fprog])
@@ -230,12 +230,12 @@ arch_prctl(code flags[arch_prctl_code], addr buffer[in])
 seccomp(op flags[seccomp_op], flags flags[seccomp_flags], prog ptr[in, sock_fprog])
 
 resource fd_mq[fd]
-mq_open(name string, flags flags[mq_open_flags], mode flags[open_mode], attr ptr[in, mq_attr]) fd_mq
+mq_open(name ptr[in, string], flags flags[mq_open_flags], mode flags[open_mode], attr ptr[in, mq_attr]) fd_mq
 mq_timedsend(mqd fd_mq, msg buffer[in], msglen len[msg], prio intptr, timeout ptr[in, timespec, opt])
 mq_timedreceive(mqd fd_mq, msg buffer[out], msglen len[msg], prio intptr, timeout ptr[in, timespec, opt])
 mq_notify(mqd fd_mq, notif ptr[in, sigevent])
 mq_getsetattr(mqd fd_mq, attr ptr[in, mq_attr], oldattr ptr[out, mq_attr, opt])
-mq_unlink(name string)
+mq_unlink(name ptr[in, string])
 
 resource ipc[int32]: 0, 0xffffffffffffffff
 resource ipc_msq[ipc]
@@ -345,21 +345,23 @@ getdents64(fd fd_dir, ent buffer[out], count len[ent])
 name_to_handle_at(fd fd_dir, file filename, handle ptr[in, file_handle], mnt ptr[out, int32], flags flags[name_to_handle_at_flags])
 open_by_handle_at(mountdirfd fd, handle ptr[in, file_handle], flags flags[open_flags])
 
-mount(src filename, dst filename, type filesystem, flags flags[mount_flags], data buffer[in])
-mount$fs(src filesystem, dst filename, type filesystem, flags flags[mount_flags], data buffer[in])
+mount(src filename, dst filename, type ptr[in, string[filesystem]], flags flags[mount_flags], data buffer[in])
+mount$fs(src ptr[in, string[filesystem]], dst filename, type ptr[in, string[filesystem]], flags flags[mount_flags], data buffer[in])
 umount2(path filename, flags flags[umount_flags])
 pivot_root(new_root filename, put_old filename)
 
-sysfs$1(option flags[sysfs_opt1], fsname string)
-sysfs$2(option flags[sysfs_opt2], fsindex intptr, fsname buffer[out])
-sysfs$3(option flags[sysfs_opt3])
+filesystem = "sysfs", "rootfs", "ramfs", "tmpfs", "devtmpfs", "debugfs", "securityfs", "sockfs", "pipefs", "anon_inodefs", "devpts", "ext3", "ext2", "ext4", "hugetlbfs", "vfat", "ecryptfs", "kdbusfs", "fuseblk", "fuse", "rpc_pipefs", "nfs", "nfs4", "nfsd", "binfmt_misc", "autofs", "xfs", "jfs", "msdos", "ntfs", "minix", "hfs", "hfsplus", "qnx4", "ufs", "btrfs", "configfs", "ncpfs", "qnx6", "exofs", "befs", "vxfs", "gfs2", "gfs2meta", "fusectl", "bfs", "nsfs", "efs", "cifs", "efivarfs", "affs", "tracefs", "bdev", "ocfs2", "ocfs2_dlmfs", "hpfs", "proc", "afs", "reiserfs", "jffs2", "romfs", "aio", "sysv", "v7", "udf", "ceph", "pstore", "adfs", "9p", "hostfs", "squashfs", "cramfs", "iso9660", "coda", "nilfs2", "logfs", "overlay", "f2fs", "omfs", "ubifs", "openpromfs"
+
+sysfs$1(option const[1], fsname ptr[in, string])
+sysfs$2(option const[2], fsindex intptr, fsname buffer[out])
+sysfs$3(option const[3])
 statfs(path filename, buf buffer[out])
 fstatfs(fd fd, buf buffer[out])
 
 uselib(lib filename)
-init_module(mod string, len len[mod], args string)
-finit_module(fd fd, args string, flags flags[finit_module_flags])
-delete_module(name string, flags flags[delete_module_flags])
+init_module(mod ptr[in, string], len len[mod], args ptr[in, string])
+finit_module(fd fd, args ptr[in, string], flags flags[finit_module_flags])
+delete_module(name ptr[in, string], flags flags[delete_module_flags])
 kexec_load(entry intptr, nr_segments len[segments], segments ptr[in, array[kexec_segment]], flags flags[kexec_load_flags])
 get_kernel_syms(table buffer[out])
 syslog(cmd flags[syslog_cmd], buf buffer[out, opt], len len[buf])
@@ -381,18 +383,18 @@ ioprio_set$pid(which flags[ioprio_which_pid], who pid, prio intptr)
 ioprio_set$uid(which flags[ioprio_which_uid], who uid, prio intptr)
 setns(fd fd, type flags[ns_type])
 
-setxattr(path filename, name string, val string, size len[val], flags flags[setxattr_flags])
-lsetxattr(path filename,  name string, val string, size len[val], flags flags[setxattr_flags])
-fsetxattr(fd fd,  name string, val string, size len[val], flags flags[setxattr_flags])
-getxattr(path filename,  name string, val buffer[out], size len[val])
-lgetxattr(path filename,  name string, val buffer[out], size len[val])
-fgetxattr(fd fd,  name string, val buffer[out], size len[val])
+setxattr(path filename, name ptr[in, string], val ptr[in, string], size len[val], flags flags[setxattr_flags])
+lsetxattr(path filename,  name ptr[in, string], val ptr[in, string], size len[val], flags flags[setxattr_flags])
+fsetxattr(fd fd,  name ptr[in, string], val ptr[in, string], size len[val], flags flags[setxattr_flags])
+getxattr(path filename,  name ptr[in, string], val buffer[out], size len[val])
+lgetxattr(path filename,  name ptr[in, string], val buffer[out], size len[val])
+fgetxattr(fd fd,  name ptr[in, string], val buffer[out], size len[val])
 listxattr(path filename, list buffer[out], size len[list])
 llistxattr(path filename, list buffer[out], size len[list])
 flistxattr(fd fd, list buffer[out], size len[list])
-removexattr(path filename,  name string)
-lremovexattr(path filename,  name string)
-fremovexattr(fd fd,  name string)
+removexattr(path filename,  name ptr[in, string])
+lremovexattr(path filename,  name ptr[in, string])
+fremovexattr(fd fd,  name ptr[in, string])
 
 resource timerid[int32]
 timer_create(id flags[clock_id], ev ptr[in, sigevent], timerid ptr[out, timerid])
@@ -463,55 +465,55 @@ membarrier(cmd const[1], flags const[0])
 # These devices are relatively safe (don't reboot and don't corrupt kernel memory).
 # They need a more comprehensive support. But let at least open them for now,
 # maybe fuzzer will be able to skrew them in a useful way.
-syz_open_dev$floppy(dev strconst["/dev/fd#"], id intptr, flags flags[open_flags]) fd
-syz_open_dev$pktcdvd(dev strconst["/dev/pktcdvd/control"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$lightnvm(dev strconst["/dev/lightnvm/control"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$vcs(dev strconst["/dev/vcs"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$vcsn(dev strconst["/dev/vcs#"], id intptr, flags flags[open_flags]) fd
-syz_open_dev$vcsa(dev strconst["/dev/vcsa#"], id intptr, flags flags[open_flags]) fd
-syz_open_dev$vga_arbiter(dev strconst["/dev/vga_arbiter"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$vhci(dev strconst["/dev/vhci"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$userio(dev strconst["/dev/userio"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$rtc(dev strconst["/dev/rtc"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$rfkill(dev strconst["/dev/rfkill"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$qat_adf_ctl(dev strconst["/dev/qat_adf_ctl"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$ppp(dev strconst["/dev/ppp"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$mixer(dev strconst["/dev/mixer"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$irnet(dev strconst["/dev/irnet"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$hwrng(dev strconst["/dev/hwrng"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$hpet(dev strconst["/dev/hpet"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$hidraw0(dev strconst["/dev/hidraw0"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$fb0(dev strconst["/dev/fb0"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$cuse(dev strconst["/dev/cuse"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$console(dev strconst["/dev/console"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$capi20(dev strconst["/dev/capi20"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$autofs(dev strconst["/dev/autofs"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$binder(dev strconst["/dev/binder"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$ion(dev strconst["/dev/ion"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$keychord(dev strconst["/dev/keychord"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$zygote(dev strconst["/dev/socket/zygote"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$sw_sync(dev strconst["/dev/sw_sync"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$sr(dev strconst["/dev/sr0"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$sequencer(dev strconst["/dev/sequencer"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$sequencer2(dev strconst["/dev/sequencer2"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$dsp(dev strconst["/dev/dsp"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$audio(dev strconst["/dev/audio"], id const[0], flags flags[open_flags]) fd
-syz_open_dev$usbmon(dev strconst["/dev/usbmon#"], id intptr, flags flags[open_flags]) fd
-syz_open_dev$sg(dev strconst["/dev/sg#"], id intptr, flags flags[open_flags]) fd
-syz_open_dev$midi(dev strconst["/dev/midi#"], id intptr, flags flags[open_flags]) fd
-syz_open_dev$loop(dev strconst["/dev/loop#"], id intptr, flags flags[open_flags]) fd
-syz_open_dev$ircomm(dev strconst["/dev/ircomm#"], id intptr, flags flags[open_flags]) fd
-syz_open_dev$dspn(dev strconst["/dev/dsp#"], id intptr, flags flags[open_flags]) fd
-syz_open_dev$dmmidi(dev strconst["/dev/dmmidi#"], id intptr, flags flags[open_flags]) fd
-syz_open_dev$admmidi(dev strconst["/dev/admmidi#"], id intptr, flags flags[open_flags]) fd
-syz_open_dev$adsp(dev strconst["/dev/adsp#"], id intptr, flags flags[open_flags]) fd
-syz_open_dev$amidi(dev strconst["/dev/amidi#"], id intptr, flags flags[open_flags]) fd
-syz_open_dev$audion(dev strconst["/dev/audio#"], id intptr, flags flags[open_flags]) fd
-syz_open_dev$usb(dev strconst["/dev/bus/usb/00#/00#"], id intptr, flags flags[open_flags]) fd
-syz_open_dev$sndhw(dev strconst["/dev/snd/hwC#D#"], id intptr, flags flags[open_flags]) fd
-syz_open_dev$sndmidi(dev strconst["/dev/snd/midiC#D#"], id intptr, flags flags[open_flags]) fd
-syz_open_dev$sndpcmc(dev strconst["/dev/snd/pcmC#D#c"], id intptr, flags flags[open_flags]) fd
-syz_open_dev$sndpcmp(dev strconst["/dev/snd/pcmC#D#p"], id intptr, flags flags[open_flags]) fd
+syz_open_dev$floppy(dev ptr[in, string["/dev/fd#"]], id intptr, flags flags[open_flags]) fd
+syz_open_dev$pktcdvd(dev ptr[in, string["/dev/pktcdvd/control"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$lightnvm(dev ptr[in, string["/dev/lightnvm/control"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$vcs(dev ptr[in, string["/dev/vcs"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$vcsn(dev ptr[in, string["/dev/vcs#"]], id intptr, flags flags[open_flags]) fd
+syz_open_dev$vcsa(dev ptr[in, string["/dev/vcsa#"]], id intptr, flags flags[open_flags]) fd
+syz_open_dev$vga_arbiter(dev ptr[in, string["/dev/vga_arbiter"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$vhci(dev ptr[in, string["/dev/vhci"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$userio(dev ptr[in, string["/dev/userio"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$rtc(dev ptr[in, string["/dev/rtc"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$rfkill(dev ptr[in, string["/dev/rfkill"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$qat_adf_ctl(dev ptr[in, string["/dev/qat_adf_ctl"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$ppp(dev ptr[in, string["/dev/ppp"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$mixer(dev ptr[in, string["/dev/mixer"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$irnet(dev ptr[in, string["/dev/irnet"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$hwrng(dev ptr[in, string["/dev/hwrng"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$hpet(dev ptr[in, string["/dev/hpet"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$hidraw0(dev ptr[in, string["/dev/hidraw0"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$fb0(dev ptr[in, string["/dev/fb0"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$cuse(dev ptr[in, string["/dev/cuse"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$console(dev ptr[in, string["/dev/console"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$capi20(dev ptr[in, string["/dev/capi20"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$autofs(dev ptr[in, string["/dev/autofs"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$binder(dev ptr[in, string["/dev/binder"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$ion(dev ptr[in, string["/dev/ion"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$keychord(dev ptr[in, string["/dev/keychord"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$zygote(dev ptr[in, string["/dev/socket/zygote"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$sw_sync(dev ptr[in, string["/dev/sw_sync"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$sr(dev ptr[in, string["/dev/sr0"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$sequencer(dev ptr[in, string["/dev/sequencer"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$sequencer2(dev ptr[in, string["/dev/sequencer2"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$dsp(dev ptr[in, string["/dev/dsp"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$audio(dev ptr[in, string["/dev/audio"]], id const[0], flags flags[open_flags]) fd
+syz_open_dev$usbmon(dev ptr[in, string["/dev/usbmon#"]], id intptr, flags flags[open_flags]) fd
+syz_open_dev$sg(dev ptr[in, string["/dev/sg#"]], id intptr, flags flags[open_flags]) fd
+syz_open_dev$midi(dev ptr[in, string["/dev/midi#"]], id intptr, flags flags[open_flags]) fd
+syz_open_dev$loop(dev ptr[in, string["/dev/loop#"]], id intptr, flags flags[open_flags]) fd
+syz_open_dev$ircomm(dev ptr[in, string["/dev/ircomm#"]], id intptr, flags flags[open_flags]) fd
+syz_open_dev$dspn(dev ptr[in, string["/dev/dsp#"]], id intptr, flags flags[open_flags]) fd
+syz_open_dev$dmmidi(dev ptr[in, string["/dev/dmmidi#"]], id intptr, flags flags[open_flags]) fd
+syz_open_dev$admmidi(dev ptr[in, string["/dev/admmidi#"]], id intptr, flags flags[open_flags]) fd
+syz_open_dev$adsp(dev ptr[in, string["/dev/adsp#"]], id intptr, flags flags[open_flags]) fd
+syz_open_dev$amidi(dev ptr[in, string["/dev/amidi#"]], id intptr, flags flags[open_flags]) fd
+syz_open_dev$audion(dev ptr[in, string["/dev/audio#"]], id intptr, flags flags[open_flags]) fd
+syz_open_dev$usb(dev ptr[in, string["/dev/bus/usb/00#/00#"]], id intptr, flags flags[open_flags]) fd
+syz_open_dev$sndhw(dev ptr[in, string["/dev/snd/hwC#D#"]], id intptr, flags flags[open_flags]) fd
+syz_open_dev$sndmidi(dev ptr[in, string["/dev/snd/midiC#D#"]], id intptr, flags flags[open_flags]) fd
+syz_open_dev$sndpcmc(dev ptr[in, string["/dev/snd/pcmC#D#c"]], id intptr, flags flags[open_flags]) fd
+syz_open_dev$sndpcmp(dev ptr[in, string["/dev/snd/pcmC#D#p"]], id intptr, flags flags[open_flags]) fd
 
 
 
@@ -1167,9 +1169,6 @@ ioprio_which_uid = IOPRIO_WHO_USER
 setxattr_flags = XATTR_CREATE, XATTR_REPLACE
 ns_type = 0, CLONE_NEWIPC, CLONE_NEWNET, CLONE_NEWUTS
 personality_flags = PER_LINUX, PER_SVR4, PER_SVR3, PER_OSR5, PER_WYSEV386, PER_ISCR4, PER_BSD, PER_XENIX, PER_LINUX32, PER_IRIX32, PER_IRIXN32, PER_IRIX64, PER_RISCOS, PER_SOLARIS, PER_UW7, PER_OSF4, PER_HPUX, ADDR_NO_RANDOMIZE, MMAP_PAGE_ZERO, ADDR_COMPAT_LAYOUT, READ_IMPLIES_EXEC, ADDR_LIMIT_32BIT, SHORT_INODE, WHOLE_SECONDS, STICKY_TIMEOUTS, ADDR_LIMIT_3GB
-sysfs_opt1 = 1
-sysfs_opt2 = 2
-sysfs_opt3 = 3
 clock_id = CLOCK_REALTIME, CLOCK_REALTIME_COARSE, CLOCK_MONOTONIC, CLOCK_MONOTONIC_COARSE, CLOCK_MONOTONIC_RAW, CLOCK_BOOTTIME, CLOCK_PROCESS_CPUTIME_ID, CLOCK_THREAD_CPUTIME_ID
 sigprocmask_how = SIG_BLOCK, SIG_UNBLOCK, SIG_SETMASK
 getitimer_which = ITIMER_REAL, ITIMER_VIRTUAL, ITIMER_PROF
diff --git a/sys/tlk_device.txt b/sys/tlk_device.txt
index 7535d16f7..1d5bd8229 100644
--- a/sys/tlk_device.txt
+++ b/sys/tlk_device.txt
@@ -12,7 +12,7 @@ include <security/tlk_driver/ote_protocol.h>
 resource fd_tlk[fd]
 resource te_session_id[int32]
 
-syz_open_dev$tlk_device(dev strconst["/dev/tlk_device"], id const[0], flags flags[open_flags]) fd_tlk
+syz_open_dev$tlk_device(dev ptr[in, string["/dev/tlk_device"]], id const[0], flags flags[open_flags]) fd_tlk
 
 ioctl$TE_IOCTL_OPEN_CLIENT_SESSION(fd fd_tlk, cmd const[TE_IOCTL_OPEN_CLIENT_SESSION], arg ptr[inout, te_opensession])
 ioctl$TE_IOCTL_CLOSE_CLIENT_SESSION(fd fd_tlk, cmd const[TE_IOCTL_CLOSE_CLIENT_SESSION], arg ptr[inout, te_closesession])
diff --git a/sys/tty.txt b/sys/tty.txt
index 67b11b754..e9717806c 100644
--- a/sys/tty.txt
+++ b/sys/tty.txt
@@ -8,7 +8,7 @@ include <uapi/linux/fcntl.h>
 
 resource fd_tty[fd]
 
-openat$ptmx(fd const[AT_FDCWD], file strconst["/dev/ptmx"], flags flags[open_flags], mode const[0]) fd_tty
+openat$ptmx(fd const[AT_FDCWD], file ptr[in, string["/dev/ptmx"]], flags flags[open_flags], mode const[0]) fd_tty
 syz_open_pts(fd fd_tty, flags flags[open_flags]) fd_tty
 ioctl$TCGETS(fd fd_tty, cmd const[TCGETS], arg ptr[out, termios])
 ioctl$TCSETS(fd fd_tty, cmd const[TCSETS], arg ptr[in, termios])
diff --git a/sys/tun.txt b/sys/tun.txt
index 04e640786..a730ed86a 100755
--- a/sys/tun.txt
+++ b/sys/tun.txt
@@ -6,7 +6,7 @@ include <linux/virtio_net.h>
 
 resource fd_tun[fd]
 
-syz_open_dev$tun(dev strconst["/dev/net/tun"], id const[0], flags flags[open_flags]) fd_tun
+syz_open_dev$tun(dev ptr[in, string["/dev/net/tun"]], id const[0], flags flags[open_flags]) fd_tun
 write$tun(fd fd_tun, buf ptr[in, tun_buffer], count len[buf])
 
 ioctl$TUNGETFEATURES(fd fd_tun, cmd const[TUNGETFEATURES], arg ptr[out, int32])
diff --git a/sysgen/sysgen.go b/sysgen/sysgen.go
index d197b774b..fda931b14 100644
--- a/sysgen/sysgen.go
+++ b/sysgen/sysgen.go
@@ -162,7 +162,7 @@ func generate(arch string, desc *Description, consts map[string]uint64, out io.W
 		fmt.Fprintf(out, "func() { Calls = append(Calls, &Call{Name: \"%v\", CallName: \"%v\"", s.Name, s.CallName)
 		if len(s.Ret) != 0 {
 			fmt.Fprintf(out, ", Ret: ")
-			generateArg("", "ret", s.Ret[0], s.Ret[1:], desc, consts, true, false, out)
+			generateArg("", "ret", s.Ret[0], "out", s.Ret[1:], desc, consts, true, false, out)
 		}
 		fmt.Fprintf(out, ", Args: []Type{")
 		for i, a := range s.Args {
@@ -170,7 +170,7 @@ func generate(arch string, desc *Description, consts map[string]uint64, out io.W
 				fmt.Fprintf(out, ", ")
 			}
 			logf(5, "      generate description for arg %v", i)
-			generateArg("", a[0], a[1], a[2:], desc, consts, true, false, out)
+			generateArg("", a[0], a[1], "in", a[2:], desc, consts, true, false, out)
 		}
 		if skipCurrentSyscall != "" {
 			logf(0, "unsupported syscall: %v due to %v", s.Name, skipCurrentSyscall)
@@ -230,7 +230,7 @@ func generateResources(desc *Description, consts map[string]uint64, out io.Write
 			}
 		}
 		fmt.Fprintf(out, "\"%v\": &ResourceDesc{Name: \"%v\", Type: ", name, name)
-		generateArg("", "resource-type", underlying, nil, desc, consts, true, true, out)
+		generateArg("", "resource-type", underlying, "inout", nil, desc, consts, true, true, out)
 		fmt.Fprintf(out, ", Kind: []string{")
 		for i, k := range kind {
 			if i != 0 {
@@ -253,11 +253,21 @@ func generateResources(desc *Description, consts map[string]uint64, out io.Write
 	fmt.Fprintf(out, "}\n")
 }
 
-func generateStructEntry(str Struct, key string, name string, out io.Writer) {
+type structKey struct {
+	name  string
+	field string
+	dir   string
+}
+
+func generateStructEntry(str Struct, key structKey, out io.Writer) {
 	typ := "StructType"
 	if str.IsUnion {
 		typ = "UnionType"
 	}
+	name := key.field
+	if name == "" {
+		name = key.name
+	}
 	packed := ""
 	if str.Packed {
 		packed = ", packed: true"
@@ -270,11 +280,11 @@ func generateStructEntry(str Struct, key string, name string, out io.Writer) {
 	if str.Align != 0 {
 		align = fmt.Sprintf(", align: %v", str.Align)
 	}
-	fmt.Fprintf(out, "\"%v\": &%v{TypeCommon: TypeCommon{TypeName: \"%v\", IsOptional: %v} %v %v %v},\n",
-		key, typ, name, false, packed, align, varlen)
+	fmt.Fprintf(out, "\"%v\": &%v{TypeCommon: TypeCommon{TypeName: \"%v\", ArgDir: %v, IsOptional: %v} %v %v %v},\n",
+		key, typ, name, fmtDir(key.dir), false, packed, align, varlen)
 }
 
-func generateStructFields(str Struct, key string, desc *Description, consts map[string]uint64, out io.Writer) {
+func generateStructFields(str Struct, key structKey, desc *Description, consts map[string]uint64, out io.Writer) {
 	typ := "StructType"
 	fields := "Fields"
 	if str.IsUnion {
@@ -284,7 +294,7 @@ func generateStructFields(str Struct, key string, desc *Description, consts map[
 	fmt.Fprintf(out, "{ s := Structs[\"%v\"].(*%v)\n", key, typ)
 	for _, a := range str.Flds {
 		fmt.Fprintf(out, "s.%v = append(s.%v, ", fields, fields)
-		generateArg(str.Name, a[0], a[1], a[2:], desc, consts, false, true, out)
+		generateArg(str.Name, a[0], a[1], key.dir, a[2:], desc, consts, false, true, out)
 		fmt.Fprintf(out, ")\n")
 	}
 	fmt.Fprintf(out, "}\n")
@@ -301,24 +311,23 @@ func generateStructs(desc *Description, consts map[string]uint64, out io.Writer)
 	// for each field indexed by the name of the parent struct and the
 	// field name.
 
-	structMap := make(map[string]Struct)
+	structMap := make(map[structKey]Struct)
 	for _, str := range desc.Structs {
-		if _, ok := structMap[str.Name]; ok {
-			failf("two structs with the same name '%v'", str.Name)
+		for _, dir := range []string{"in", "out", "inout"} {
+			structMap[structKey{str.Name, "", dir}] = str
 		}
-		structMap[str.Name] = str
 		for _, a := range str.Flds {
 			if innerStr, ok := desc.Structs[a[1]]; ok {
-				structMap[fmt.Sprintf("%v-%v", str.Name, a[0])] = innerStr
+				for _, dir := range []string{"in", "out", "inout"} {
+					structMap[structKey{a[1], a[0], dir}] = innerStr
+				}
 			}
 		}
 	}
 
 	fmt.Fprintf(out, "var Structs = map[string]Type{\n")
 	for key, str := range structMap {
-		keyParts := strings.Split(key, "-")
-		name := keyParts[len(keyParts)-1]
-		generateStructEntry(str, key, name, out)
+		generateStructEntry(str, key, out)
 	}
 	fmt.Fprintf(out, "}\n")
 
@@ -351,7 +360,7 @@ func parseRange(buffer string, consts map[string]uint64) (string, string) {
 }
 
 func generateArg(
-	parent, name, typ string,
+	parent, name, typ, dir string,
 	a []string,
 	desc *Description,
 	consts map[string]uint64,
@@ -369,7 +378,7 @@ func generateArg(
 		}
 	}
 	common := func() string {
-		return fmt.Sprintf("TypeCommon: TypeCommon{TypeName: %v, IsOptional: %v}", name, opt)
+		return fmt.Sprintf("TypeCommon: TypeCommon{TypeName: %v, ArgDir: %v, IsOptional: %v}", name, fmtDir(dir), opt)
 	}
 	canBeArg := false
 	switch typ {
@@ -378,61 +387,89 @@ func generateArg(
 		size := uint64(ptrSize)
 		bigEndian := false
 		if isField {
-			if want := 2; len(a) != want {
+			if want := 1; len(a) != want {
 				failf("wrong number of arguments for %v arg %v, want %v, got %v", typ, name, want, len(a))
 			}
-			size, bigEndian = decodeIntType(a[1])
+			size, bigEndian = decodeIntType(a[0])
 		} else {
-			if want := 1; len(a) != want {
+			if want := 0; len(a) != want {
 				failf("wrong number of arguments for %v arg %v, want %v, got %v", typ, name, want, len(a))
 			}
 		}
-		fmt.Fprintf(out, "FileoffType{%v, File: \"%v\", TypeSize: %v, BigEndian: %v}", common(), a[0], size, bigEndian)
+		fmt.Fprintf(out, "&IntType{%v, TypeSize: %v, BigEndian: %v, Kind: IntFileoff}", common(), size, bigEndian)
 	case "buffer":
 		canBeArg = true
 		if want := 1; len(a) != want {
 			failf("wrong number of arguments for %v arg %v, want %v, got %v", typ, name, want, len(a))
 		}
-		commonHdr := common()
+		ptrCommonHdr := common()
+		dir = a[0]
 		opt = false
-		fmt.Fprintf(out, "PtrType{%v, Dir: %v, Type: BufferType{%v, Kind: BufferBlobRand}}", commonHdr, fmtDir(a[0]), common())
+		fmt.Fprintf(out, "&PtrType{%v, Type: &BufferType{%v, Kind: BufferBlobRand}}", ptrCommonHdr, common())
 	case "string":
-		canBeArg = true
-		if want := 0; len(a) != want {
-			failf("wrong number of arguments for %v arg %v, want %v, got %v", typ, name, want, len(a))
+		if len(a) != 0 && len(a) != 1 && len(a) != 2 {
+			failf("wrong number of arguments for %v arg %v, want 0-2, got %v", typ, name, len(a))
+		}
+		var vals []string
+		subkind := ""
+		if len(a) >= 1 {
+			if a[0][0] == '"' {
+				vals = append(vals, a[0][1:len(a[0])-1])
+			} else {
+				vals1, ok := desc.StrFlags[a[0]]
+				if !ok {
+					failf("unknown string flags %v", a[0])
+				}
+				vals = append([]string{}, vals1...)
+				subkind = a[0]
+			}
 		}
-		commonHdr := common()
-		opt = false
-		fmt.Fprintf(out, "PtrType{%v, Dir: %v, Type: BufferType{%v, Kind: BufferString}}", commonHdr, fmtDir("in"), common())
-	case "filesystem":
-		canBeArg = true
-		if want := 0; len(a) != want {
-			failf("wrong number of arguments for %v arg %v, want %v, got %v", typ, name, want, len(a))
+		for i, s := range vals {
+			vals[i] = s + "\x00"
 		}
-		commonHdr := common()
-		opt = false
-		fmt.Fprintf(out, "PtrType{%v, Dir: %v, Type: BufferType{%v, Kind: BufferFilesystem}}", commonHdr, fmtDir("in"), common())
+		if len(a) >= 2 {
+			var size uint64
+			if v, ok := consts[a[1]]; ok {
+				size = v
+			} else {
+				v, err := strconv.ParseUint(a[1], 10, 64)
+				if err != nil {
+					failf("failed to parse string length for %v", name, a[1])
+				}
+				size = v
+			}
+			for i, s := range vals {
+				if uint64(len(s)) > size {
+					failf("string value %q exceeds buffer length %v for arg %v", s, size, name)
+				}
+				for uint64(len(s)) < size {
+					s += "\x00"
+				}
+				vals[i] = s
+			}
+		}
+		fmt.Fprintf(out, "&BufferType{%v, Kind: BufferString, SubKind: %q, Values: %#v}", common(), subkind, vals)
 	case "sockaddr":
 		if want := 0; len(a) != want {
 			failf("wrong number of arguments for %v arg %v, want %v, got %v", typ, name, want, len(a))
 		}
-		fmt.Fprintf(out, "BufferType{%v, Kind: BufferSockaddr}", common())
+		fmt.Fprintf(out, "&BufferType{%v, Kind: BufferSockaddr}", common())
 	case "salg_type":
 		if want := 0; len(a) != want {
 			failf("wrong number of arguments for %v arg %v, want %v, got %v", typ, name, want, len(a))
 		}
-		fmt.Fprintf(out, "BufferType{%v, Kind: BufferAlgType}", common())
+		fmt.Fprintf(out, "&BufferType{%v, Kind: BufferAlgType}", common())
 	case "salg_name":
 		if want := 0; len(a) != want {
 			failf("wrong number of arguments for %v arg %v, want %v, got %v", typ, name, want, len(a))
 		}
-		fmt.Fprintf(out, "BufferType{%v, Kind: BufferAlgName}", common())
+		fmt.Fprintf(out, "&BufferType{%v, Kind: BufferAlgName}", common())
 	case "vma":
 		canBeArg = true
 		if want := 0; len(a) != want {
 			failf("wrong number of arguments for %v arg %v, want %v, got %v", typ, name, want, len(a))
 		}
-		fmt.Fprintf(out, "VmaType{%v}", common())
+		fmt.Fprintf(out, "&VmaType{%v}", common())
 	case "len", "bytesize":
 		canBeArg = true
 		size := uint64(ptrSize)
@@ -447,7 +484,7 @@ func generateArg(
 				failf("wrong number of arguments for %v arg %v, want %v, got %v", typ, name, want, len(a))
 			}
 		}
-		fmt.Fprintf(out, "LenType{%v, Buf: \"%v\", TypeSize: %v, BigEndian: %v, ByteSize: %v}", common(), a[0], size, bigEndian, typ == "bytesize")
+		fmt.Fprintf(out, "&LenType{%v, Buf: \"%v\", TypeSize: %v, BigEndian: %v, ByteSize: %v}", common(), a[0], size, bigEndian, typ == "bytesize")
 	case "flags":
 		canBeArg = true
 		size := uint64(ptrSize)
@@ -467,9 +504,9 @@ func generateArg(
 			failf("unknown flag %v", a[0])
 		}
 		if len(vals) == 0 {
-			fmt.Fprintf(out, "IntType{%v, TypeSize: %v, BigEndian: %v}", common(), size, bigEndian)
+			fmt.Fprintf(out, "&IntType{%v, TypeSize: %v, BigEndian: %v}", common(), size, bigEndian)
 		} else {
-			fmt.Fprintf(out, "FlagsType{%v, TypeSize: %v, BigEndian: %v, Vals: []uintptr{%v}}", common(), size, bigEndian, strings.Join(vals, ","))
+			fmt.Fprintf(out, "&FlagsType{%v, TypeSize: %v, BigEndian: %v, Vals: []uintptr{%v}}", common(), size, bigEndian, strings.Join(vals, ","))
 		}
 	case "const":
 		canBeArg = true
@@ -494,22 +531,16 @@ func generateArg(
 			val = "0"
 			skipSyscall(fmt.Sprintf("missing const %v", a[0]))
 		}
-		fmt.Fprintf(out, "ConstType{%v, TypeSize: %v, BigEndian: %v, Val: uintptr(%v)}", common(), size, bigEndian, val)
-	case "strconst":
-		canBeArg = true
-		if want := 1; len(a) != want {
-			failf("wrong number of arguments for %v arg %v, want %v, got %v", typ, name, want, len(a))
-		}
-		fmt.Fprintf(out, "PtrType{%v, Dir: %v, Type: StrConstType{%v, Val: \"%v\"}}", common(), fmtDir("in"), common(), a[0]+"\\x00")
+		fmt.Fprintf(out, "&ConstType{%v, TypeSize: %v, BigEndian: %v, Val: uintptr(%v)}", common(), size, bigEndian, val)
 	case "int8", "int16", "int32", "int64", "intptr", "int16be", "int32be", "int64be", "intptrbe":
 		canBeArg = true
 		size, bigEndian := decodeIntType(typ)
 		switch len(a) {
 		case 0:
-			fmt.Fprintf(out, "IntType{%v, TypeSize: %v, BigEndian: %v}", common(), size, bigEndian)
+			fmt.Fprintf(out, "&IntType{%v, TypeSize: %v, BigEndian: %v}", common(), size, bigEndian)
 		case 1:
 			begin, end := parseRange(a[0], consts)
-			fmt.Fprintf(out, "IntType{%v, TypeSize: %v, BigEndian: %v, Kind: IntRange, RangeBegin: %v, RangeEnd: %v}", common(), size, bigEndian, begin, end)
+			fmt.Fprintf(out, "&IntType{%v, TypeSize: %v, BigEndian: %v, Kind: IntRange, RangeBegin: %v, RangeEnd: %v}", common(), size, bigEndian, begin, end)
 		default:
 			failf("wrong number of arguments for %v arg %v, want 0 or 1, got %v", typ, name, len(a))
 		}
@@ -518,41 +549,42 @@ func generateArg(
 		if want := 0; len(a) != want {
 			failf("wrong number of arguments for %v arg %v, want %v, got %v", typ, name, want, len(a))
 		}
-		fmt.Fprintf(out, "IntType{%v, TypeSize: 4, Kind: IntSignalno}", common())
+		fmt.Fprintf(out, "&IntType{%v, TypeSize: 4, Kind: IntSignalno}", common())
 	case "in_addr":
 		if want := 0; len(a) != want {
 			failf("wrong number of arguments for %v arg %v, want %v, got %v", typ, name, want, len(a))
 		}
-		fmt.Fprintf(out, "IntType{%v, TypeSize: 4, Kind: IntInaddr}", common())
+		fmt.Fprintf(out, "&IntType{%v, TypeSize: 4, Kind: IntInaddr}", common())
 	case "in_port":
 		if want := 0; len(a) != want {
 			failf("wrong number of arguments for %v arg %v, want %v, got %v", typ, name, want, len(a))
 		}
-		fmt.Fprintf(out, "IntType{%v, TypeSize: 2, Kind: IntInport}", common())
+		fmt.Fprintf(out, "&IntType{%v, TypeSize: 2, Kind: IntInport}", common())
 	case "filename":
 		canBeArg = true
 		if want := 0; len(a) != want {
 			failf("wrong number of arguments for %v arg %v, want %v, got %v", typ, name, want, len(a))
 		}
-		commonHdr := common()
+		ptrCommonHdr := common()
+		dir = "in"
 		opt = false
-		fmt.Fprintf(out, "PtrType{%v, Dir: DirIn, Type: FilenameType{%v}}", commonHdr, common())
+		fmt.Fprintf(out, "&PtrType{%v, Type: &BufferType{%v, Kind: BufferFilename}}", ptrCommonHdr, common())
 	case "array":
 		if len(a) != 1 && len(a) != 2 {
 			failf("wrong number of arguments for %v arg %v, want 1 or 2, got %v", typ, name, len(a))
 		}
 		if len(a) == 1 {
 			if a[0] == "int8" {
-				fmt.Fprintf(out, "BufferType{%v, Kind: BufferBlobRand}", common())
+				fmt.Fprintf(out, "&BufferType{%v, Kind: BufferBlobRand}", common())
 			} else {
-				fmt.Fprintf(out, "ArrayType{%v, Type: %v, Kind: ArrayRandLen}", common(), generateType(a[0], desc, consts))
+				fmt.Fprintf(out, "&ArrayType{%v, Type: %v, Kind: ArrayRandLen}", common(), generateType(a[0], dir, desc, consts))
 			}
 		} else {
 			begin, end := parseRange(a[1], consts)
 			if a[0] == "int8" {
-				fmt.Fprintf(out, "BufferType{%v, Kind: BufferBlobRange, RangeBegin: %v, RangeEnd: %v}", common(), begin, end)
+				fmt.Fprintf(out, "&BufferType{%v, Kind: BufferBlobRange, RangeBegin: %v, RangeEnd: %v}", common(), begin, end)
 			} else {
-				fmt.Fprintf(out, "ArrayType{%v, Type: %v, Kind: ArrayRangeLen, RangeBegin: %v, RangeEnd: %v}", common(), generateType(a[0], desc, consts), begin, end)
+				fmt.Fprintf(out, "&ArrayType{%v, Type: %v, Kind: ArrayRangeLen, RangeBegin: %v, RangeEnd: %v}", common(), generateType(a[0], dir, desc, consts), begin, end)
 			}
 		}
 	case "ptr":
@@ -560,11 +592,12 @@ func generateArg(
 		if want := 2; len(a) != want {
 			failf("wrong number of arguments for %v arg %v, want %v, got %v", typ, name, want, len(a))
 		}
-		fmt.Fprintf(out, "PtrType{%v, Type: %v, Dir: %v}", common(), generateType(a[1], desc, consts), fmtDir(a[0]))
+		dir = "in"
+		fmt.Fprintf(out, "&PtrType{%v, Type: %v}", common(), generateType(a[1], a[0], desc, consts))
 	default:
 		if strings.HasPrefix(typ, "unnamed") {
 			if inner, ok := desc.Unnamed[typ]; ok {
-				generateArg("", "", inner[0], inner[1:], desc, consts, false, isField, out)
+				generateArg("", "", inner[0], dir, inner[1:], desc, consts, false, isField, out)
 			} else {
 				failf("unknown unnamed type '%v'", typ)
 			}
@@ -572,16 +605,12 @@ func generateArg(
 			if len(a) != 0 {
 				failf("struct '%v' has args", typ)
 			}
-			if parent == "" {
-				fmt.Fprintf(out, "Structs[\"%v\"]", typ)
-			} else {
-				fmt.Fprintf(out, "Structs[\"%v-%v\"]", parent, origName)
-			}
+			fmt.Fprintf(out, "Structs[\"%v\"]", structKey{typ, origName, dir})
 		} else if _, ok := desc.Resources[typ]; ok {
 			if len(a) != 0 {
 				failf("resource '%v' has args", typ)
 			}
-			fmt.Fprintf(out, "ResourceType{%v, Desc: Resources[\"%v\"]}", common(), typ)
+			fmt.Fprintf(out, "&ResourceType{%v, Desc: Resources[\"%v\"]}", common(), typ)
 			return
 		} else {
 			failf("unknown arg type \"%v\" for %v", typ, name)
@@ -592,9 +621,9 @@ func generateArg(
 	}
 }
 
-func generateType(typ string, desc *Description, consts map[string]uint64) string {
+func generateType(typ, dir string, desc *Description, consts map[string]uint64) string {
 	buf := new(bytes.Buffer)
-	generateArg("", "", typ, nil, desc, consts, false, true, buf)
+	generateArg("", "", typ, dir, nil, desc, consts, false, true, buf)
 	return buf.String()
 }
 
diff --git a/sysparser/lexer.go b/sysparser/lexer.go
index 06210a584..a3b8f58ed 100644
--- a/sysparser/lexer.go
+++ b/sysparser/lexer.go
@@ -18,6 +18,7 @@ type Description struct {
 	Structs   map[string]Struct
 	Unnamed   map[string][]string
 	Flags     map[string][]string
+	StrFlags  map[string][]string
 	Resources map[string]Resource
 }
 
@@ -51,6 +52,7 @@ func Parse(in io.Reader) *Description {
 	structs := make(map[string]Struct)
 	unnamed := make(map[string][]string)
 	flags := make(map[string][]string)
+	strflags := make(map[string][]string)
 	resources := make(map[string]Resource)
 	var str *Struct
 	for p.Scan() {
@@ -93,6 +95,9 @@ func Parse(in io.Reader) *Description {
 				}
 				fields := make(map[string]bool)
 				for _, f := range str.Flds {
+					if f[0] == "parent" {
+						failf("struct/union %v contains reserved field 'parent'", str.Name)
+					}
 					if fields[f[0]] {
 						failf("duplicate field %v in struct/union %v", f[0], str.Name)
 					}
@@ -189,12 +194,24 @@ func Parse(in io.Reader) *Description {
 				case '=':
 					// flag
 					p.Parse('=')
-					vals := []string{p.Ident()}
-					for !p.EOF() {
+					str := p.Char() == '"'
+					var vals []string
+					for {
+						v := p.Ident()
+						if str {
+							v = v[1 : len(v)-1]
+						}
+						vals = append(vals, v)
+						if p.EOF() {
+							break
+						}
 						p.Parse(',')
-						vals = append(vals, p.Ident())
 					}
-					flags[name] = vals
+					if str {
+						strflags[name] = vals
+					} else {
+						flags[name] = vals
+					}
 				case '{', '[':
 					p.Parse(ch)
 					if _, ok := structs[name]; ok {
@@ -221,6 +238,7 @@ func Parse(in io.Reader) *Description {
 		Structs:   structs,
 		Unnamed:   unnamed,
 		Flags:     flags,
+		StrFlags:  strflags,
 		Resources: resources,
 	}
 }
diff --git a/sysparser/parser.go b/sysparser/parser.go
index 590847b0e..d5021eee6 100644
--- a/sysparser/parser.go
+++ b/sysparser/parser.go
@@ -70,11 +70,10 @@ func (p *parser) Ident() string {
 	start, end := p.i, 0
 	if p.Char() == '"' {
 		p.Parse('"')
-		start++
 		for p.Char() != '"' {
 			p.i++
 		}
-		end = p.i
+		end = p.i + 1
 		p.Parse('"')
 	} else {
 		for p.i < len(p.s) &&