sys: add padding to structs again

Struct padding was accidentially lost after:
852e3d2eae98a913b7ec91822ba4dc61059a6955
Restore it. Now with tests.

Fixes #78

6 files changed, 119 insertions, 44 deletions

diff --git a/prog/encodingexec_test.go b/prog/encodingexec_test.go
index 651352fd6..eddda5199 100644
--- a/prog/encodingexec_test.go
+++ b/prog/encodingexec_test.go
@@ -67,15 +67,26 @@ func TestSerializeForExec(t *testing.T) {
 			},
 		},
 		{
-			// TODO: the offsets are currently caclulated incorrectly.
 			"syz_test$align0(&(0x7f0000000000)={0x1, 0x2, 0x3, 0x4, 0x5})",
 			[]uint64{
 				instrCopyin, dataOffset + 0, argConst, 2, 1,
+				instrCopyin, dataOffset + 4, argConst, 4, 2,
+				instrCopyin, dataOffset + 8, argConst, 1, 3,
+				instrCopyin, dataOffset + 10, argConst, 2, 4,
+				instrCopyin, dataOffset + 16, argConst, 8, 5,
+				callID("syz_test$align0"), 1, argConst, ptrSize, dataOffset,
+				instrEOF,
+			},
+		},
+		{
+			"syz_test$align1(&(0x7f0000000000)={0x1, 0x2, 0x3, 0x4, 0x5})",
+			[]uint64{
+				instrCopyin, dataOffset + 0, argConst, 2, 1,
 				instrCopyin, dataOffset + 2, argConst, 4, 2,
 				instrCopyin, dataOffset + 6, argConst, 1, 3,
 				instrCopyin, dataOffset + 7, argConst, 2, 4,
 				instrCopyin, dataOffset + 9, argConst, 8, 5,
-				callID("syz_test$align0"), 1, argConst, ptrSize, dataOffset,
+				callID("syz_test$align1"), 1, argConst, ptrSize, dataOffset,
 				instrEOF,
 			},
 		},
@@ -88,6 +99,17 @@ func TestSerializeForExec(t *testing.T) {
 				instrEOF,
 			},
 		},
+		{
+			"syz_test$array0(&(0x7f0000000000)={0x1, [@f0=0x2, @f1=0x3], 0x4})",
+			[]uint64{
+				instrCopyin, dataOffset + 0, argConst, 1, 1,
+				instrCopyin, dataOffset + 1, argConst, 2, 2,
+				instrCopyin, dataOffset + 3, argConst, 8, 3,
+				instrCopyin, dataOffset + 11, argConst, 8, 4,
+				callID("syz_test$array0"), 1, argConst, ptrSize, dataOffset,
+				instrEOF,
+			},
+		},
 	}
 
 	for i, test := range tests {
diff --git a/sys/align.go b/sys/align.go
index 4c91c28be..6e8563da4 100644
--- a/sys/align.go
+++ b/sys/align.go
@@ -3,51 +3,37 @@
 
 package sys
 
-import (
-	"fmt"
-)
-
 func initAlign() {
-	var rec func(t Type) Type
-	rec = func(t Type) Type {
+	var rec func(t Type)
+	rec = func(t Type) {
 		switch t1 := t.(type) {
 		case PtrType:
-			t1.Type = rec(t1.Type)
-			t = t1
+			rec(t1.Type)
 		case ArrayType:
-			t1.Type = rec(t1.Type)
-			t = t1
+			rec(t1.Type)
 		case *StructType:
-			for i, f := range t1.Fields {
-				t1.Fields[i] = rec(f)
+			if !t1.padded {
+				t1.padded = true
+				for _, f := range t1.Fields {
+					rec(f)
+				}
+				addAlignment(t1)
 			}
-			t = addAlignment(t1)
 		case *UnionType:
-			opts := make(map[string]bool)
-			for i, opt := range t1.Options {
-				if opts[opt.Name()] {
-					panic(fmt.Sprintf("duplicate option %v in union %v", opt.Name(), t.Name()))
-				}
-				opts[opt.Name()] = true
-				t1.Options[i] = rec(opt)
+			for _, opt := range t1.Options {
+				rec(opt)
 			}
 		}
-		return t
 	}
-	for _, c := range Calls {
-		for i, t := range c.Args {
-			c.Args[i] = rec(t)
-		}
-		if c.Ret != nil {
-			c.Ret = rec(c.Ret)
-		}
+
+	for _, s := range Structs {
+		rec(s)
 	}
 }
 
-func addAlignment(t *StructType) Type {
+func addAlignment(t *StructType) {
 	if t.packed {
-		t.padded = true
-		return t
+		return
 	}
 	var fields []Type
 	var off, align uintptr
@@ -77,8 +63,6 @@ func addAlignment(t *StructType) Type {
 		fields = append(fields, makePad(pad))
 	}
 	t.Fields = fields
-	t.padded = true
-	return t
 }
 
 func makePad(sz uintptr) Type {
diff --git a/sys/decl.go b/sys/decl.go
index 2cc8f22e5..f792f541c 100644
--- a/sys/decl.go
+++ b/sys/decl.go
@@ -252,11 +252,14 @@ type ArrayType struct {
 }
 
 func (t ArrayType) Size() uintptr {
-	panic("should not be called")
+	if t.RangeBegin == t.RangeEnd {
+		return t.RangeBegin * t.Type.Size()
+	}
+	return 0 // for trailing embed arrays
 }
 
 func (t ArrayType) Align() uintptr {
-	panic("should not be called")
+	return t.Type.Align()
 }
 
 type PtrType struct {
@@ -282,11 +285,27 @@ type StructType struct {
 }
 
 func (t *StructType) Size() uintptr {
-	panic("not called")
+	if !t.padded {
+		panic("struct is not padded yet")
+	}
+	var size uintptr
+	for _, f := range t.Fields {
+		size += f.Size()
+	}
+	return size
 }
 
 func (t *StructType) Align() uintptr {
-	panic("not called")
+	if t.align != 0 {
+		return t.align // overrided by user attribute
+	}
+	var align uintptr
+	for _, f := range t.Fields {
+		if a1 := f.Align(); align < a1 {
+			align = a1
+		}
+	}
+	return align
 }
 
 type UnionType struct {
@@ -296,11 +315,26 @@ type UnionType struct {
 }
 
 func (t *UnionType) Size() uintptr {
-	panic("not called")
+	if t.varlen {
+		panic("union size is not statically known")
+	}
+	size := t.Options[0].Size()
+	for _, opt := range t.Options {
+		if size < opt.Size() {
+			size = opt.Size()
+		}
+	}
+	return size
 }
 
 func (t *UnionType) Align() uintptr {
-	panic("not called")
+	var align uintptr
+	for _, opt := range t.Options {
+		if a1 := opt.Align(); align < a1 {
+			align = a1
+		}
+	}
+	return align
 }
 
 type Dir int
@@ -503,6 +537,7 @@ var (
 
 func init() {
 	initCalls()
+	initStructFields()
 	initResources()
 	initAlign()
 
diff --git a/sys/test.txt b/sys/test.txt
index 2fc41e677..a01c6b3c2 100644
--- a/sys/test.txt
+++ b/sys/test.txt
@@ -15,6 +15,7 @@ syz_test$opt2(a0 vma[opt])
 
 # Struct alignment.
 syz_test$align0(a0 ptr[in, syz_align0])
+syz_test$align1(a0 ptr[in, syz_align1])
 
 syz_align0 {
 	f0	int16
@@ -24,6 +25,14 @@ syz_align0 {
 	f4	int64
 }
 
+syz_align1 {
+	f0	int16
+	f1	int32
+	f2	int8
+	f3	int16
+	f4	int64
+} [packed]
+
 # Unions.
 
 syz_test$union0(a0 ptr[in, syz_union_struct])
@@ -38,3 +47,19 @@ syz_union0 [
 	f1	array[int64, 10]
 	f2	int8
 ]
+
+# Arrays.
+
+syz_test$array0(a0 ptr[in, syz_array_struct])
+
+# Struct with a variable-length array or variable-length unions.
+syz_array_struct {
+	f0	int8
+	f1	array[syz_array_union, 1:2]
+	f2	int64
+} [packed]
+
+syz_array_union [
+	f0	int16
+	f1	int64
+] [varlen]
diff --git a/sysgen/sysgen.go b/sysgen/sysgen.go
index e7a0fae00..c27e413c3 100644
--- a/sysgen/sysgen.go
+++ b/sysgen/sysgen.go
@@ -283,7 +283,7 @@ func generateStructs(desc *Description, consts map[string]uint64, out io.Writer)
 	}
 	fmt.Fprintf(out, "}\n")
 
-	fmt.Fprintf(out, "func init() {\n")
+	fmt.Fprintf(out, "func initStructFields() {\n")
 	for _, str := range structArray {
 		typ := "StructType"
 		fields := "Fields"
diff --git a/sysparser/lexer.go b/sysparser/lexer.go
index 21c7b77ef..85f657d41 100644
--- a/sysparser/lexer.go
+++ b/sysparser/lexer.go
@@ -86,8 +86,17 @@ func Parse(in io.Reader) *Description {
 						}
 					}
 				}
-				if str.IsUnion && len(str.Flds) <= 1 {
-					failf("union %v has only %v fields, need at least 2", str.Name, len(str.Flds))
+				if str.IsUnion {
+					if len(str.Flds) <= 1 {
+						failf("union %v has only %v fields, need at least 2", str.Name, len(str.Flds))
+					}
+					fields := make(map[string]bool)
+					for _, f := range str.Flds {
+						if fields[f[0]] {
+							failf("duplicate filed %v in struct/union %v", f[0], str.Name)
+						}
+						fields[f[0]] = true
+					}
 				}
 				structs[str.Name] = *str
 				str = nil