runtime, runtime/msan: add msan runtime support

These are the runtime support functions for letting Go code interoperate
with the C/C++ memory sanitizer.  Calls to msanread/msanwrite are now
inserted by the compiler with the -msan option.  Calls to
msanmalloc/msanfree will be from other runtime functions in a subsequent
CL.

Change-Id: I64fb061b38cc6519153face242eccd291c07d1f2
Reviewed-on: https://go-review.googlesource.com/16162
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/go/build/deps_test.go

@@ -263,8 +263,9 @@ var pkgDeps = map[string][]string{
 	// that shows up in programs that use cgo.
 	"C": {},
 
-	// Race detector uses cgo.
+	// Race detector/MSan uses cgo.
 	"runtime/race": {"C"},
+	"runtime/msan": {"C"},
 
 	// Plan 9 alone needs io/ioutil and os.
 	"os/user": {"L4", "CGO", "io/ioutil", "os", "syscall"},

src/runtime/msan.go

+// Copyright 2015 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build msan
+
+package runtime
+
+import (
+	"unsafe"
+)
+
+// Public memory sanitizer API.
+
+func MSanRead(addr unsafe.Pointer, len int) {
+	msanread(addr, uintptr(len))
+}
+
+func MSanWrite(addr unsafe.Pointer, len int) {
+	msanwrite(addr, uintptr(len))
+}
+
+// Private interface for the runtime.
+const msanenabled = true
+
+//go:noescape
+func msanread(addr unsafe.Pointer, sz uintptr)
+
+//go:noescape
+func msanwrite(addr unsafe.Pointer, sz uintptr)
+
+//go:noescape
+func msanmalloc(addr unsafe.Pointer, sz uintptr)
+
+//go:noescape
+func msanfree(addr unsafe.Pointer, sz uintptr)
+
+// These are called from msan_amd64.s
+//go:cgo_import_static __msan_read_go
+//go:cgo_import_static __msan_write_go
+//go:cgo_import_static __msan_malloc_go
+//go:cgo_import_static __msan_free_go

src/runtime/msan/msan.go

+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build msan,linux,amd64
+
+package msan
+
+/*
+#cgo CFLAGS: -fsanitize=memory
+#cgo LDFLAGS: -fsanitize=memory
+
+#include <stdint.h>
+#include <sanitizer/msan_interface.h>
+
+void __msan_read_go(void *addr, uintptr_t sz) {
+	__msan_check_mem_is_initialized(addr, sz);
+}
+
+void __msan_write_go(void *addr, uintptr_t sz) {
+	__msan_unpoison(addr, sz);
+}
+
+void __msan_malloc_go(void *addr, uintptr_t sz) {
+	__msan_unpoison(addr, sz);
+}
+
+void __msan_free_go(void *addr, uintptr_t sz) {
+	__msan_poison(addr, sz);
+}
+*/
+import "C"

src/runtime/msan0.go

+// Copyright 2015 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !msan
+
+// Dummy MSan support API, used when not built with -msan.
+
+package runtime
+
+import (
+	"unsafe"
+)
+
+const msanenabled = false
+
+// Because msanenabled is false, none of these functions should be called.
+
+func msanread(addr unsafe.Pointer, sz uintptr)   { throw("race") }
+func msanwrite(addr unsafe.Pointer, sz uintptr)  { throw("race") }
+func msanmalloc(addr unsafe.Pointer, sz uintptr) { throw("msan") }
+func msanfree(addr unsafe.Pointer, sz uintptr)   { throw("msan") }

src/runtime/msan_amd64.s

+// Copyright 2015 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build msan
+
+#include "go_asm.h"
+#include "go_tls.h"
+#include "funcdata.h"
+#include "textflag.h"
+
+// This is like race_amd64.s, but for the msan calls.
+// See race_amd64.s for detailed comments.
+
+#ifdef GOOS_windows
+#define RARG0 CX
+#define RARG1 DX
+#define RARG2 R8
+#define RARG3 R9
+#else
+#define RARG0 DI
+#define RARG1 SI
+#define RARG2 DX
+#define RARG3 CX
+#endif
+
+// func runtime·msanread(addr unsafe.Pointer, sz uintptr)
+// Called from instrumented code.
+TEXT	runtime·msanread(SB), NOSPLIT, $0-16
+	MOVQ	addr+0(FP), RARG0
+	MOVQ	size+8(FP), RARG1
+	// void __msan_read_go(void *addr, uintptr_t sz);
+	MOVQ	$__msan_read_go(SB), AX
+	JMP	msancall<>(SB)
+
+// func runtime·msanwrite(addr unsafe.Pointer, sz uintptr)
+// Called from instrumented code.
+TEXT	runtime·msanwrite(SB), NOSPLIT, $0-16
+	MOVQ	addr+0(FP), RARG0
+	MOVQ	size+8(FP), RARG1
+	// void __msan_write_go(void *addr, uintptr_t sz);
+	MOVQ	$__msan_write_go(SB), AX
+	JMP	msancall<>(SB)
+
+// func runtime·msanmalloc(addr unsafe.Pointer, sz uintptr)
+TEXT	runtime·msanmalloc(SB), NOSPLIT, $0-16
+	MOVQ	addr+0(FP), RARG0
+	MOVQ	size+8(FP), RARG1
+	// void __msan_malloc_go(void *addr, uintptr_t sz);
+	MOVQ	$__msan_malloc_go(SB), AX
+	JMP	msancall<>(SB)
+
+// func runtime·msanfree(addr unsafe.Pointer, sz uintptr)
+TEXT	runtime·msanfree(SB), NOSPLIT, $0-16
+	MOVQ	addr+0(FP), RARG0
+	MOVQ	size+8(FP), RARG1
+	// void __msan_free_go(void *addr, uintptr_t sz);
+	MOVQ	$__msan_free_go(SB), AX
+	JMP	msancall<>(SB)
+
+// Switches SP to g0 stack and calls (AX). Arguments already set.
+TEXT	msancall<>(SB), NOSPLIT, $0-0
+	get_tls(R12)
+	MOVQ	g(R12), R14
+	MOVQ	g_m(R14), R13
+	// Switch to g0 stack.
+	MOVQ	SP, R12		// callee-saved, preserved across the CALL
+	MOVQ	m_g0(R13), R10
+	CMPQ	R10, R14
+	JE	call	// already on g0
+	MOVQ	(g_sched+gobuf_sp)(R10), SP
+call:
+	ANDQ	$~15, SP	// alignment for gcc ABI
+	CALL	AX
+	MOVQ	R12, SP
+	RET