cmd/compile: add -msan option

The -msan option causes the compiler to add instrumentation for the
C/C++ memory sanitizer.  Every memory read/write will be preceded by
a call to msanread/msanwrite.

This CL passes tests but is not usable by itself.  The actual
implementation of msanread/msanwrite in the runtime package, and support
for -msan in the go tool and the linker, and tests, will follow in
subsequent CLs.

Change-Id: I3d517fb3e6e65d9bf9433db070a420fd11f57816
Reviewed-on: https://go-review.googlesource.com/16160Reviewed-by: David Crawshaw <crawshaw@golang.org>

src/cmd/compile/doc.go

@@ -66,6 +66,8 @@ Flags:
 		Write memory profile for the compilation to file.
 	-memprofilerate rate
 		Set runtime.MemProfileRate for the compilation to rate.
+	-msan
+		Insert calls to C/C++ memory sanitizer.
 	-nolocalimports
 		Disallow local (relative) imports.
 	-o file

src/cmd/compile/internal/gc/builtin.go

@@ -155,6 +155,8 @@ const runtimeimport = "" +
 	"func @\"\".racewrite (? uintptr)\n" +
 	"func @\"\".racereadrange (@\"\".addr·1 uintptr, @\"\".size·2 uintptr)\n" +
 	"func @\"\".racewriterange (@\"\".addr·1 uintptr, @\"\".size·2 uintptr)\n" +
+	"func @\"\".msanread (@\"\".addr·1 uintptr, @\"\".size·2 uintptr)\n" +
+	"func @\"\".msanwrite (@\"\".addr·1 uintptr, @\"\".size·2 uintptr)\n" +
 	"\n" +
 	"$$\n"
 

src/cmd/compile/internal/gc/builtin/runtime.go

@@ -193,3 +193,7 @@ func raceread(uintptr)
 func racewrite(uintptr)
 func racereadrange(addr, size uintptr)
 func racewriterange(addr, size uintptr)
+
+// memory sanitizer
+func msanread(addr, size uintptr)
+func msanwrite(addr, size uintptr)

src/cmd/compile/internal/gc/go.go

@@ -511,6 +511,8 @@ var Runtimepkg *Pkg // package runtime
 
 var racepkg *Pkg // package runtime/race
 
+var msanpkg *Pkg // package runtime/msan
+
 var typepkg *Pkg // fake package for runtime type info (headers)
 
 var typelinkpkg *Pkg // fake package for runtime type info (data)
@@ -645,6 +647,8 @@ var flag_installsuffix string
 
 var flag_race int
 
+var flag_msan int
+
 var flag_largemodel int
 
 // Whether we are adding any sort of code instrumentation, such as

src/cmd/compile/internal/gc/lex.go

@@ -200,6 +200,7 @@ func Main() {
 	obj.Flagcount("l", "disable inlining", &Debug['l'])
 	obj.Flagcount("live", "debug liveness analysis", &debuglive)
 	obj.Flagcount("m", "print optimization decisions", &Debug['m'])
+	obj.Flagcount("msan", "build code compatible with C/C++ memory sanitizer", &flag_msan)
 	obj.Flagcount("nolocalimports", "reject local (relative) imports", &nolocalimports)
 	obj.Flagstr("o", "write output to `file`", &outfile)
 	obj.Flagstr("p", "set expected package import `path`", &myimportpath)
@@ -249,6 +250,14 @@ func Main() {
 	if flag_race != 0 {
 		racepkg = mkpkg("runtime/race")
 		racepkg.Name = "race"
+	}
+	if flag_msan != 0 {
+		msanpkg = mkpkg("runtime/msan")
+		msanpkg.Name = "msan"
+	}
+	if flag_race != 0 && flag_msan != 0 {
+		log.Fatal("can not use both -race and -msan")
+	} else if flag_race != 0 || flag_msan != 0 {
 		instrumenting = true
 	}
 
@@ -623,6 +632,9 @@ func findpkg(name string) (file string, ok bool) {
 		} else if flag_race != 0 {
 			suffixsep = "_"
 			suffix = "race"
+		} else if flag_msan != 0 {
+			suffixsep = "_"
+			suffix = "msan"
 		}
 
 		file = fmt.Sprintf("%s/pkg/%s_%s%s%s/%s.a", goroot, goos, goarch, suffixsep, suffix, name)

src/cmd/compile/internal/gc/racewalk.go

@@ -18,6 +18,11 @@ import (
 // 3. It inserts a call to raceread before each memory read.
 // 4. It inserts a call to racewrite before each memory write.
 //
+// For flag_msan:
+//
+// 1. It inserts a call to msanread before each memory read.
+// 2. It inserts a call to msanwrite before each memory write.
+//
 // The rewriting is not yet complete. Certain nodes are not rewritten
 // but should be.
 
@@ -26,11 +31,11 @@ import (
 
 // Do not instrument the following packages at all,
 // at best instrumentation would cause infinite recursion.
-var omit_pkgs = []string{"runtime", "runtime/race"}
+var omit_pkgs = []string{"runtime", "runtime/race", "runtime/msan"}
 
 // Only insert racefuncenter/racefuncexit into the following packages.
 // Memory accesses in the packages are either uninteresting or will cause false positives.
-var noinst_pkgs = []string{"sync", "sync/atomic"}
+var norace_inst_pkgs = []string{"sync", "sync/atomic"}
 
 func ispkgin(pkgs []string) bool {
 	if myimportpath != "" {
@@ -49,25 +54,27 @@ func instrument(fn *Node) {
 		return
 	}
 
-	if !ispkgin(noinst_pkgs) {
+	if flag_race == 0 || !ispkgin(norace_inst_pkgs) {
 		instrumentlist(fn.Nbody, nil)
 
 		// nothing interesting for race detector in fn->enter
 		instrumentlist(fn.Func.Exit, nil)
 	}
 
-	// nodpc is the PC of the caller as extracted by
-	// getcallerpc. We use -widthptr(FP) for x86.
-	// BUG: this will not work on arm.
-	nodpc := Nod(OXXX, nil, nil)
-
-	*nodpc = *nodfp
-	nodpc.Type = Types[TUINTPTR]
-	nodpc.Xoffset = int64(-Widthptr)
-	nd := mkcall("racefuncenter", nil, nil, nodpc)
-	fn.Func.Enter = concat(list1(nd), fn.Func.Enter)
-	nd = mkcall("racefuncexit", nil, nil)
-	fn.Func.Exit = list(fn.Func.Exit, nd)
+	if flag_race != 0 {
+		// nodpc is the PC of the caller as extracted by
+		// getcallerpc. We use -widthptr(FP) for x86.
+		// BUG: this will not work on arm.
+		nodpc := Nod(OXXX, nil, nil)
+
+		*nodpc = *nodfp
+		nodpc.Type = Types[TUINTPTR]
+		nodpc.Xoffset = int64(-Widthptr)
+		nd := mkcall("racefuncenter", nil, nil, nodpc)
+		fn.Func.Enter = concat(list1(nd), fn.Func.Enter)
+		nd = mkcall("racefuncexit", nil, nil)
+		fn.Func.Exit = list(fn.Func.Exit, nd)
+	}
 
 	if Debug['W'] != 0 {
 		s := fmt.Sprintf("after instrument %v", fn.Func.Nname.Sym)
@@ -427,7 +434,8 @@ ret:
 
 func isartificial(n *Node) bool {
 	// compiler-emitted artificial things that we do not want to instrument,
-	// cant' possibly participate in a data race.
+	// can't possibly participate in a data race.
+	// can't be seen by C/C++ and therefore irrelevant for msan.
 	if n.Op == ONAME && n.Sym != nil && n.Sym.Name != "" {
 		if n.Sym.Name == "_" {
 			return true
@@ -489,13 +497,19 @@ func callinstr(np **Node, init **NodeList, wr int, skip int) bool {
 		n = treecopy(n, 0)
 		makeaddable(n)
 		var f *Node
-		if t.Etype == TSTRUCT || Isfixedarray(t) {
+		if flag_msan != 0 {
+			name := "msanread"
+			if wr != 0 {
+				name = "msanwrite"
+			}
+			f = mkcall(name, nil, init, uintptraddr(n), Nodintconst(t.Width))
+		} else if flag_race != 0 && (t.Etype == TSTRUCT || Isfixedarray(t)) {
 			name := "racereadrange"
 			if wr != 0 {
 				name = "racewriterange"
 			}
 			f = mkcall(name, nil, init, uintptraddr(n), Nodintconst(t.Width))
-		} else {
+		} else if flag_race != 0 {
 			name := "raceread"
 			if wr != 0 {
 				name = "racewrite"

src/cmd/compile/internal/gc/reflect.go

@@ -1292,6 +1292,9 @@ func dumptypestructs() {
 		if flag_race != 0 {
 			dimportpath(racepkg)
 		}
+		if flag_msan != 0 {
+			dimportpath(msanpkg)
+		}
 		dimportpath(mkpkg("main"))
 	}
 }

src/cmd/compile/internal/gc/subr.go

@@ -1643,7 +1643,7 @@ func ullmancalc(n *Node) {
 		ul = UINF
 		goto out
 
-		// hard with race detector
+		// hard with instrumented code
 	case OANDAND, OOROR:
 		if instrumenting {
 			ul = UINF

src/cmd/compile/internal/gc/walk.go

@@ -3037,7 +3037,7 @@ func walkappend(n *Node, init **NodeList, dst *Node) *Node {
 	}
 
 	// General case, with no function calls left as arguments.
-	// Leave for gen, except that race detector requires old form
+	// Leave for gen, except that instrumentation requires old form.
 	if !instrumenting {
 		return n
 	}