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 <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

13 files changed, 140 insertions, 16 deletions

diff --git a/src/runtime/cgo/gcc_linux_arm64.c b/src/runtime/cgo/gcc_linux_arm64.c
index b328407f39..8630f2f03e 100644
--- a/src/runtime/cgo/gcc_linux_arm64.c
+++ b/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);
diff --git a/src/runtime/cgo/gcc_mmap.c b/src/runtime/cgo/gcc_mmap.c
index 5cf6bdf8cf..e6a621d5a3 100644
--- a/src/runtime/cgo/gcc_mmap.c
+++ b/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>
diff --git a/src/runtime/cgo/gcc_sigaction.c b/src/runtime/cgo/gcc_sigaction.c
index 72fb08d720..05dee2affe 100644
--- a/src/runtime/cgo/gcc_sigaction.c
+++ b/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>
diff --git a/src/runtime/cgo/mmap.go b/src/runtime/cgo/mmap.go
index ad5f6df70a..00fb7fced6 100644
--- a/src/runtime/cgo/mmap.go
+++ b/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
 
diff --git a/src/runtime/cgo/sigaction.go b/src/runtime/cgo/sigaction.go
index e25f4ff2f3..076fbc1a0a 100644
--- a/src/runtime/cgo/sigaction.go
+++ b/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
 
diff --git a/src/runtime/cgo_mmap.go b/src/runtime/cgo_mmap.go
index b7c70c6fff..048621f306 100644
--- a/src/runtime/cgo_mmap.go
+++ b/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
 
diff --git a/src/runtime/cgo_sigaction.go b/src/runtime/cgo_sigaction.go
index 9832d35f03..3ef6800cd9 100644
--- a/src/runtime/cgo_sigaction.go
+++ b/src/runtime/cgo_sigaction.go
@@ -4,7 +4,7 @@
 
 // Support for memory sanitizer. See runtime/cgo/sigaction.go.
 
-// +build linux,amd64 freebsd,amd64
+// +build linux,amd64 freebsd,amd64 linux,arm64
 
 package runtime
 
diff --git a/src/runtime/mmap.go b/src/runtime/mmap.go
index e1333c62fe..152cbcdae5 100644
--- a/src/runtime/mmap.go
+++ b/src/runtime/mmap.go
@@ -7,6 +7,7 @@
 // +build !windows
 // +build !nacl
 // +build !linux !amd64
+// +build !linux !arm64
 
 package runtime
 
diff --git a/src/runtime/msan/msan.go b/src/runtime/msan/msan.go
index b6ea3f0d16..c81577ddda 100644
--- a/src/runtime/msan/msan.go
+++ b/src/runtime/msan/msan.go
@@ -2,7 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build msan,linux,amd64
+// +build msan,linux
+// +build amd64 arm64
 
 package msan
 
diff --git a/src/runtime/msan_arm64.s b/src/runtime/msan_arm64.s
new file mode 100644
index 0000000000..4dfe5e3133
--- /dev/null
+++ b/src/runtime/msan_arm64.s
@@ -0,0 +1,62 @@
+// Copyright 2018 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 "textflag.h"
+
+#define RARG0 R0
+#define RARG1 R1
+#define FARG R3
+
+// func runtime·domsanread(addr unsafe.Pointer, sz uintptr)
+// Called from msanread.
+TEXT	runtime·domsanread(SB), NOSPLIT, $0-16
+	MOVD	addr+0(FP), RARG0
+	MOVD	size+8(FP), RARG1
+	// void __msan_read_go(void *addr, uintptr_t sz);
+	MOVD	$__msan_read_go(SB), FARG
+	JMP	msancall<>(SB)
+
+// func runtime·msanwrite(addr unsafe.Pointer, sz uintptr)
+// Called from instrumented code.
+TEXT	runtime·msanwrite(SB), NOSPLIT, $0-16
+	MOVD	addr+0(FP), RARG0
+	MOVD	size+8(FP), RARG1
+	// void __msan_write_go(void *addr, uintptr_t sz);
+	MOVD	$__msan_write_go(SB), FARG
+	JMP	msancall<>(SB)
+
+// func runtime·msanmalloc(addr unsafe.Pointer, sz uintptr)
+TEXT	runtime·msanmalloc(SB), NOSPLIT, $0-16
+	MOVD	addr+0(FP), RARG0
+	MOVD	size+8(FP), RARG1
+	// void __msan_malloc_go(void *addr, uintptr_t sz);
+	MOVD	$__msan_malloc_go(SB), FARG
+	JMP	msancall<>(SB)
+
+// func runtime·msanfree(addr unsafe.Pointer, sz uintptr)
+TEXT	runtime·msanfree(SB), NOSPLIT, $0-16
+	MOVD	addr+0(FP), RARG0
+	MOVD	size+8(FP), RARG1
+	// void __msan_free_go(void *addr, uintptr_t sz);
+	MOVD	$__msan_free_go(SB), FARG
+	JMP	msancall<>(SB)
+
+// Switches SP to g0 stack and calls (FARG). Arguments already set.
+TEXT	msancall<>(SB), NOSPLIT, $0-0
+	MOVD	g_m(g), R10
+	MOVD	m_g0(R10), R11
+	MOVD	RSP, R19	// callee-saved
+	CMP	R11, g
+	BEQ	g0stack
+
+	MOVD	(g_sched+gobuf_sp)(R11), R4
+	MOVD	R4, RSP
+
+g0stack:
+	BL	(FARG)
+	MOVD	R19, RSP
+	RET
diff --git a/src/runtime/rt0_linux_arm64.s b/src/runtime/rt0_linux_arm64.s
index e81e598d3a..458f082159 100644
--- a/src/runtime/rt0_linux_arm64.s
+++ b/src/runtime/rt0_linux_arm64.s
@@ -11,7 +11,7 @@ TEXT _rt0_arm64_linux(SB),NOSPLIT|NOFRAME,$0
 
 // When building with -buildmode=c-shared, this symbol is called when the shared
 // library is loaded.
-TEXT _rt0_arm64_linux_lib(SB),NOSPLIT,$168
+TEXT _rt0_arm64_linux_lib(SB),NOSPLIT,$184
 	// Preserve callee-save registers.
 	MOVD R19, 24(RSP)
 	MOVD R20, 32(RSP)
@@ -30,6 +30,10 @@ TEXT _rt0_arm64_linux_lib(SB),NOSPLIT,$168
 	FMOVD F13, 136(RSP)
 	FMOVD F14, 144(RSP)
 	FMOVD F15, 152(RSP)
+	MOVD g, 160(RSP)
+
+	// Initialize g as null in case of using g later e.g. sigaction in cgo_sigaction.go
+	MOVD	ZR, g
 
 	MOVD	R0, _rt0_arm64_linux_lib_argc<>(SB)
 	MOVD	R1, _rt0_arm64_linux_lib_argv<>(SB)
@@ -74,6 +78,7 @@ restore:
 	FMOVD 136(RSP), F13
 	FMOVD 144(RSP), F14
 	FMOVD 152(RSP), F15
+	MOVD 160(RSP), g
 	RET
 
 TEXT _rt0_arm64_linux_lib_go(SB),NOSPLIT,$0
diff --git a/src/runtime/sigaction.go b/src/runtime/sigaction.go
index eb454f9327..3c888579d0 100644
--- a/src/runtime/sigaction.go
+++ b/src/runtime/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,!arm64 freebsd,!amd64
 
 package runtime
 
diff --git a/src/runtime/sys_linux_arm64.s b/src/runtime/sys_linux_arm64.s
index f930d1f044..c6afd76a65 100644
--- a/src/runtime/sys_linux_arm64.s
+++ b/src/runtime/sys_linux_arm64.s
@@ -292,6 +292,16 @@ TEXT runtime·rt_sigaction(SB),NOSPLIT|NOFRAME,$0-36
 	MOVW	R0, ret+32(FP)
 	RET
 
+// Call the function stored in _cgo_sigaction using the GCC calling convention.
+TEXT runtime·callCgoSigaction(SB),NOSPLIT,$0
+	MOVD	sig+0(FP), R0
+	MOVD	new+8(FP), R1
+	MOVD	old+16(FP), R2
+	MOVD	 _cgo_sigaction(SB), R3
+	BL	R3
+	MOVW	R0, ret+24(FP)
+	RET
+
 TEXT runtime·sigfwd(SB),NOSPLIT,$0-32
 	MOVW	sig+8(FP), R0
 	MOVD	info+16(FP), R1
@@ -320,7 +330,7 @@ TEXT runtime·cgoSigtramp(SB),NOSPLIT,$0
 	MOVD	$runtime·sigtramp(SB), R3
 	B	(R3)
 
-TEXT runtime·mmap(SB),NOSPLIT|NOFRAME,$0
+TEXT runtime·sysMmap(SB),NOSPLIT|NOFRAME,$0
 	MOVD	addr+0(FP), R0
 	MOVD	n+8(FP), R1
 	MOVW	prot+16(FP), R2
@@ -341,7 +351,21 @@ ok:
 	MOVD	$0, err+40(FP)
 	RET
 
-TEXT runtime·munmap(SB),NOSPLIT|NOFRAME,$0
+// Call the function stored in _cgo_mmap using the GCC calling convention.
+// This must be called on the system stack.
+TEXT runtime·callCgoMmap(SB),NOSPLIT,$0
+	MOVD	addr+0(FP), R0
+	MOVD	n+8(FP), R1
+	MOVW	prot+16(FP), R2
+	MOVW	flags+20(FP), R3
+	MOVW	fd+24(FP), R4
+	MOVW	off+28(FP), R5
+	MOVD	_cgo_mmap(SB), R9
+	BL	R9
+	MOVD	R0, ret+32(FP)
+	RET
+
+TEXT runtime·sysMunmap(SB),NOSPLIT|NOFRAME,$0
 	MOVD	addr+0(FP), R0
 	MOVD	n+8(FP), R1
 	MOVD	$SYS_munmap, R8
@@ -352,6 +376,15 @@ TEXT runtime·munmap(SB),NOSPLIT|NOFRAME,$0
 cool:
 	RET
 
+// Call the function stored in _cgo_munmap using the GCC calling convention.
+// This must be called on the system stack.
+TEXT runtime·callCgoMunmap(SB),NOSPLIT,$0
+	MOVD	addr+0(FP), R0
+	MOVD	n+8(FP), R1
+	MOVD	_cgo_munmap(SB), R9
+	BL	R9
+	RET
+
 TEXT runtime·madvise(SB),NOSPLIT|NOFRAME,$0
 	MOVD	addr+0(FP), R0
 	MOVD	n+8(FP), R1