runtime: enable memory sanitizer on arm64

Changes include:
1. open compilation option -msan for arm64
2. modify doc to explain -msan is also supported on linux/arm64
3. wrap msan lib API in msan_arm64.s
4. use libc for sigaction syscalls when cgo is enabled
5. use libc for mmap syscalls when cgo is enabled

Change-Id: I26ebe61ff7ce1906125f54a0182a720f9d58ec11
Reviewed-on: https://go-review.googlesource.com/109255
Run-TryBot: Ian Lance Taylor <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>

Author: zorrorffm

src/cmd/dist/test.go

@@ -676,7 +676,7 @@ func (t *tester) registerTests() {
 		if gohostos == "linux" && goarch == "amd64" {
 			t.registerTest("testasan", "../misc/cgo/testasan", "go", "run", "main.go")
 		}
-		if goos == "linux" && goarch == "amd64" {
+		if goos == "linux" && (goarch == "amd64" || goarch == "arm64") {
 			t.registerHostTest("testsanitizers/msan", "../misc/cgo/testsanitizers", "misc/cgo/testsanitizers", ".")
 		}
 		if t.hasBash() && goos != "android" && !t.iOS() && gohostos != "windows" {

src/cmd/go/alldocs.go

@@ -105,7 +105,7 @@
 // 		Supported only on linux/amd64, freebsd/amd64, darwin/amd64 and windows/amd64.
 // 	-msan
 // 		enable interoperation with memory sanitizer.
-// 		Supported only on linux/amd64,
+// 		Supported only on linux/amd64, linux/arm64
 // 		and only with Clang/LLVM as the host C compiler.
 // 	-v
 // 		print the names of packages as they are compiled.

src/cmd/go/internal/work/build.go

@@ -65,7 +65,7 @@ and test commands:
 		Supported only on linux/amd64, freebsd/amd64, darwin/amd64 and windows/amd64.
 	-msan
 		enable interoperation with memory sanitizer.
-		Supported only on linux/amd64,
+		Supported only on linux/amd64, linux/arm64
 		and only with Clang/LLVM as the host C compiler.
 	-v
 		print the names of packages as they are compiled.

src/cmd/go/internal/work/init.go

@@ -39,12 +39,12 @@ func instrumentInit() {
 		fmt.Fprintf(os.Stderr, "go %s: may not use -race and -msan simultaneously\n", flag.Args()[0])
 		os.Exit(2)
 	}
-	if cfg.BuildMSan && (cfg.Goos != "linux" || cfg.Goarch != "amd64") {
+	if cfg.BuildMSan && (cfg.Goos != "linux" || cfg.Goarch != "amd64" && cfg.Goarch != "arm64") {
 		fmt.Fprintf(os.Stderr, "-msan is not supported on %s/%s\n", cfg.Goos, cfg.Goarch)
 		os.Exit(2)
 	}
-	if cfg.Goarch != "amd64" || cfg.Goos != "linux" && cfg.Goos != "freebsd" && cfg.Goos != "darwin" && cfg.Goos != "windows" {
-		fmt.Fprintf(os.Stderr, "go %s: -race and -msan are only supported on linux/amd64, freebsd/amd64, darwin/amd64 and windows/amd64\n", flag.Args()[0])
+	if cfg.BuildRace && (cfg.Goarch != "amd64" || cfg.Goos != "linux" && cfg.Goos != "freebsd" && cfg.Goos != "darwin" && cfg.Goos != "windows") {
+		fmt.Fprintf(os.Stderr, "go %s: -race is only supported on linux/amd64, freebsd/amd64, darwin/amd64 and windows/amd64\n", flag.Args()[0])
 		os.Exit(2)
 	}
 

src/runtime/cgo/gcc_linux_arm64.c

@@ -3,8 +3,10 @@
 // license that can be found in the LICENSE file.
 
 #include <pthread.h>
+#include <errno.h>
 #include <string.h>
 #include <signal.h>
+#include <stdlib.h>
 #include "libcgo.h"
 #include "libcgo_unix.h"
 
@@ -59,14 +61,34 @@ threadentry(void *v)
 void
 x_cgo_init(G *g, void (*setg)(void*), void **tlsg, void **tlsbase)
 {
-	pthread_attr_t attr;
+	pthread_attr_t *attr;
 	size_t size;
 
+	/* The memory sanitizer distributed with versions of clang
+	   before 3.8 has a bug: if you call mmap before malloc, mmap
+	   may return an address that is later overwritten by the msan
+	   library.  Avoid this problem by forcing a call to malloc
+	   here, before we ever call malloc.
+
+	   This is only required for the memory sanitizer, so it's
+	   unfortunate that we always run it.  It should be possible
+	   to remove this when we no longer care about versions of
+	   clang before 3.8.  The test for this is
+	   misc/cgo/testsanitizers.
+
+	   GCC works hard to eliminate a seemingly unnecessary call to
+	   malloc, so we actually use the memory we allocate.  */
+
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	attr = (pthread_attr_t*)malloc(sizeof *attr);
+	if (attr == NULL) {
+		fatalf("malloc failed: %s", strerror(errno));
+	}
+	pthread_attr_init(attr);
+	pthread_attr_getstacksize(attr, &size);
+	g->stacklo = (uintptr)&size - size + 4096;
+	pthread_attr_destroy(attr);
+	free(attr);
 
 	if (x_cgo_inittls) {
 		x_cgo_inittls(tlsg, tlsbase);

src/runtime/cgo/gcc_mmap.c

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build linux,amd64
+// +build linux,amd64 linux,arm64
 
 #include <errno.h>
 #include <stdint.h>

src/runtime/cgo/gcc_sigaction.c

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build linux,amd64
+// +build linux,amd64 linux,arm64
 
 #include <errno.h>
 #include <stddef.h>

src/runtime/cgo/mmap.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build linux,amd64
+// +build linux,amd64 linux,arm64
 
 package cgo
 

src/runtime/cgo/sigaction.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build linux,amd64 freebsd,amd64
+// +build linux,amd64 freebsd,amd64 linux,arm64
 
 package cgo
 

src/runtime/cgo_mmap.go

@@ -4,7 +4,7 @@
 
 // Support for memory sanitizer. See runtime/cgo/mmap.go.
 
-// +build linux,amd64
+// +build linux,amd64 linux,arm64
 
 package runtime