diff --git a/src/cmd/cgo/ast.go b/src/cmd/cgo/ast.go
index 54d6bc2559..a073407a96 100644
--- a/src/cmd/cgo/ast.go
+++ b/src/cmd/cgo/ast.go
@@ -13,7 +13,6 @@ import (
 	"go/scanner"
 	"go/token"
 	"os"
-	"path/filepath"
 	"strings"
 )
 
@@ -44,14 +43,7 @@ func sourceLine(n ast.Node) int {
 // attached to the import "C" comment, a list of references to C.xxx,
 // a list of exported functions, and the actual AST, to be rewritten and
 // printed.
-func (f *File) ParseGo(name string, src []byte) {
-	// Create absolute path for file, so that it will be used in error
-	// messages and recorded in debug line number information.
-	// This matches the rest of the toolchain. See golang.org/issue/5122.
-	if aname, err := filepath.Abs(name); err == nil {
-		name = aname
-	}
-
+func (f *File) ParseGo(abspath string, src []byte) {
 	// Two different parses: once with comments, once without.
 	// The printer is not good enough at printing comments in the
 	// right place when we start editing the AST behind its back,
@@ -60,8 +52,8 @@ func (f *File) ParseGo(name string, src []byte) {
 	// and reprinting.
 	// In cgo mode, we ignore ast2 and just apply edits directly
 	// the text behind ast1. In godefs mode we modify and print ast2.
-	ast1 := parse(name, src, parser.ParseComments)
-	ast2 := parse(name, src, 0)
+	ast1 := parse(abspath, src, parser.ParseComments)
+	ast2 := parse(abspath, src, 0)
 
 	f.Package = ast1.Name.Name
 	f.Name = make(map[string]*Name)
@@ -88,7 +80,7 @@ func (f *File) ParseGo(name string, src []byte) {
 				cg = d.Doc
 			}
 			if cg != nil {
-				f.Preamble += fmt.Sprintf("#line %d %q\n", sourceLine(cg), name)
+				f.Preamble += fmt.Sprintf("#line %d %q\n", sourceLine(cg), abspath)
 				f.Preamble += commentText(cg) + "\n"
 				f.Preamble += "#line 1 \"cgo-generated-wrapper\"\n"
 			}
diff --git a/src/cmd/cgo/godefs.go b/src/cmd/cgo/godefs.go
index b4fd9c5a6e..c0d59aee01 100644
--- a/src/cmd/cgo/godefs.go
+++ b/src/cmd/cgo/godefs.go
@@ -16,7 +16,7 @@ import (
 )
 
 // godefs returns the output for -godefs mode.
-func (p *Package) godefs(f *File, srcfile string) string {
+func (p *Package) godefs(f *File) string {
 	var buf bytes.Buffer
 
 	fmt.Fprintf(&buf, "// Code generated by cmd/cgo -godefs; DO NOT EDIT.\n")
diff --git a/src/cmd/cgo/main.go b/src/cmd/cgo/main.go
index 7d02ac3c54..c1116e28ec 100644
--- a/src/cmd/cgo/main.go
+++ b/src/cmd/cgo/main.go
@@ -243,6 +243,8 @@ var gccgopkgpath = flag.String("gccgopkgpath", "", "-fgo-pkgpath option used wit
 var gccgoMangler func(string) string
 var importRuntimeCgo = flag.Bool("import_runtime_cgo", true, "import runtime/cgo in generated code")
 var importSyscall = flag.Bool("import_syscall", true, "import syscall in generated code")
+var trimpath = flag.String("trimpath", "", "applies supplied rewrites or trims prefixes to recorded source file paths")
+
 var goarch, goos string
 
 func main() {
@@ -322,6 +324,13 @@ func main() {
 			input = filepath.Join(*srcDir, input)
 		}
 
+		// Create absolute path for file, so that it will be used in error
+		// messages and recorded in debug line number information.
+		// This matches the rest of the toolchain. See golang.org/issue/5122.
+		if aname, err := filepath.Abs(input); err == nil {
+			input = aname
+		}
+
 		b, err := ioutil.ReadFile(input)
 		if err != nil {
 			fatalf("%s", err)
@@ -330,6 +339,10 @@ func main() {
 			fatalf("%s", err)
 		}
 
+		// Apply trimpath to the file path. The path won't be read from after this point.
+		input, _ = objabi.ApplyRewrites(input, *trimpath)
+		goFiles[i] = input
+
 		f := new(File)
 		f.Edit = edit.NewBuffer(b)
 		f.ParseGo(input, b)
@@ -367,7 +380,7 @@ func main() {
 		p.PackagePath = f.Package
 		p.Record(f)
 		if *godefs {
-			os.Stdout.WriteString(p.godefs(f, input))
+			os.Stdout.WriteString(p.godefs(f))
 		} else {
 			p.writeOutput(f, input)
 		}
diff --git a/src/cmd/internal/objabi/line.go b/src/cmd/internal/objabi/line.go
index 178c8363d9..0733b65138 100644
--- a/src/cmd/internal/objabi/line.go
+++ b/src/cmd/internal/objabi/line.go
@@ -37,27 +37,38 @@ func AbsFile(dir, file, rewrites string) string {
 		abs = filepath.Join(dir, file)
 	}
 
-	start := 0
-	for i := 0; i <= len(rewrites); i++ {
-		if i == len(rewrites) || rewrites[i] == ';' {
-			if new, ok := applyRewrite(abs, rewrites[start:i]); ok {
-				abs = new
-				goto Rewritten
-			}
-			start = i + 1
-		}
-	}
-	if hasPathPrefix(abs, GOROOT) {
+	abs, rewritten := ApplyRewrites(abs, rewrites)
+	if !rewritten && hasPathPrefix(abs, GOROOT) {
 		abs = "$GOROOT" + abs[len(GOROOT):]
 	}
 
-Rewritten:
 	if abs == "" {
 		abs = "??"
 	}
 	return abs
 }
 
+// ApplyRewrites returns the filename for file in the given directory,
+// as rewritten by the rewrites argument.
+//
+// The rewrites argument is a ;-separated list of rewrites.
+// Each rewrite is of the form "prefix" or "prefix=>replace",
+// where prefix must match a leading sequence of path elements
+// and is either removed entirely or replaced by the replacement.
+func ApplyRewrites(file, rewrites string) (string, bool) {
+	start := 0
+	for i := 0; i <= len(rewrites); i++ {
+		if i == len(rewrites) || rewrites[i] == ';' {
+			if new, ok := applyRewrite(file, rewrites[start:i]); ok {
+				return new, true
+			}
+			start = i + 1
+		}
+	}
+
+	return file, false
+}
+
 // applyRewrite applies the rewrite to the path,
 // returning the rewritten path and a boolean
 // indicating whether the rewrite applied at all.