pkg/compiler: allow specifying static size for filename's

Sometimes filenames are embed into structs and need to take fixed space.

5 files changed, 32 insertions, 9 deletions

diff --git a/prog/analysis.go b/prog/analysis.go
index 626af7446..7d5cc0099 100644
--- a/prog/analysis.go
+++ b/prog/analysis.go
@@ -73,11 +73,16 @@ func (s *state) analyzeImpl(c *Call, resources bool) {
 		case *BufferType:
 			a := arg.(*DataArg)
 			if typ.Dir() != DirOut && len(a.Data()) != 0 {
+				val := string(a.Data())
+				// Remove trailing zero padding.
+				for len(val) >= 2 && val[len(val)-1] == 0 && val[len(val)-2] == 0 {
+					val = val[:len(val)-1]
+				}
 				switch typ.Kind {
 				case BufferString:
-					s.strings[string(a.Data())] = true
+					s.strings[val] = true
 				case BufferFilename:
-					s.files[string(a.Data())] = true
+					s.files[val] = true
 				}
 			}
 		}
diff --git a/prog/mutation.go b/prog/mutation.go
index dd465cf3d..85a718a80 100644
--- a/prog/mutation.go
+++ b/prog/mutation.go
@@ -194,7 +194,7 @@ func (target *Target) mutateArg(r *randGen, s *state, arg Arg, ctx ArgCtx, updat
 				a.data = r.randString(s, t)
 			}
 		case BufferFilename:
-			a.data = []byte(r.filename(s))
+			a.data = []byte(r.filename(s, t))
 		case BufferText:
 			data := append([]byte{}, a.Data()...)
 			a.data = r.mutateText(t.Text, data)
diff --git a/prog/rand.go b/prog/rand.go
index 97571b7ea..d8ba0f33d 100644
--- a/prog/rand.go
+++ b/prog/rand.go
@@ -150,7 +150,19 @@ func (r *randGen) flags(vv []uint64) (v uint64) {
 	return
 }
 
-func (r *randGen) filename(s *state) string {
+func (r *randGen) filename(s *state, typ *BufferType) string {
+	fn := r.filenameImpl(s)
+	if !typ.Varlen() {
+		size := typ.Size()
+		if uint64(len(fn)) < size {
+			fn += string(make([]byte, size-uint64(len(fn))))
+		}
+		fn = fn[:size]
+	}
+	return fn
+}
+
+func (r *randGen) filenameImpl(s *state) string {
 	dir := "."
 	if r.oneOf(2) && len(s.files) != 0 {
 		files := make([]string, 0, len(s.files))
@@ -540,18 +552,20 @@ func (r *randGen) generateArgImpl(s *state, typ Type, ignoreSpecial bool) (arg A
 			return MakeDataArg(a, data), nil
 		case BufferFilename:
 			if a.Dir() == DirOut {
-				sz := 0
+				var sz uint64
 				switch {
+				case !a.Varlen():
+					sz = a.Size()
 				case r.nOutOf(1, 3):
-					sz = r.Intn(100)
+					sz = r.rand(100)
 				case r.nOutOf(1, 2):
 					sz = 108 // UNIX_PATH_MAX
 				default:
 					sz = 4096 // PATH_MAX
 				}
-				return MakeOutDataArg(a, uint64(sz)), nil
+				return MakeOutDataArg(a, sz), nil
 			}
-			return MakeDataArg(a, []byte(r.filename(s))), nil
+			return MakeDataArg(a, []byte(r.filename(s, a))), nil
 		case BufferText:
 			if a.Dir() == DirOut {
 				return MakeOutDataArg(a, uint64(r.Intn(100))), nil
diff --git a/prog/size_test.go b/prog/size_test.go
index 08b7cba92..8ce368d09 100644
--- a/prog/size_test.go
+++ b/prog/size_test.go
@@ -146,6 +146,10 @@ func TestAssignSize(t *testing.T) {
 			"syz_test$length28(&(0x7f0000000000), 0x0)",
 			"syz_test$length28(&(0x7f0000000000)=@f1, 0x2a)",
 		},
+		{
+			"syz_test$length29(&(0x7f0000000000)={'./a\\x00', './b/c\\x00', 0x0, 0x0, 0x0})",
+			"syz_test$length29(&(0x7f0000000000)={'./a\\x00', './b/c\\x00', 0xa, 0x14, 0x21})",
+		},
 	}
 
 	for i, test := range tests {
diff --git a/prog/types.go b/prog/types.go
index cdf1a0863..1dee2015b 100644
--- a/prog/types.go
+++ b/prog/types.go
@@ -259,7 +259,7 @@ const (
 type BufferType struct {
 	TypeCommon
 	Kind       BufferKind
-	RangeBegin uint64   // for BufferBlobRange kind
+	RangeBegin uint64   // for BufferBlobRange kind, or static size for BufferFilename
 	RangeEnd   uint64   // for BufferBlobRange kind
 	Text       TextKind // for BufferText
 	SubKind    string