runtime: add syscalls needed for android/amd64 logging.

access, connect, socket.

In Android-L, logging is done by writing the log messages to the logd
process through a unix domain socket.

Also, changed the arg types of those syscall stubs to match linux
programming APIs.

For golang/go#10743

Change-Id: I66368a03316e253561e9e76aadd180c2cd2e48f3
Reviewed-on: https://go-review.googlesource.com/15993Reviewed-by: David Crawshaw <crawshaw@golang.org>

src/runtime/defs_linux_amd64.go

@@ -87,6 +87,10 @@ const (
 	_EPOLL_CTL_ADD = 0x1
 	_EPOLL_CTL_DEL = 0x2
 	_EPOLL_CTL_MOD = 0x3
+
+	_AF_UNIX    = 0x1
+	_F_SETFL    = 0x4
+	_SOCK_DGRAM = 0x2
 )
 
 type timespec struct {
@@ -253,3 +257,8 @@ type sigcontext struct {
 	fpstate     *fpstate1
 	__reserved1 [8]uint64
 }
+
+type sockaddr_un struct {
+	family uint16
+	path   [108]byte
+}

src/runtime/print1_write_android.go

@@ -116,7 +116,7 @@ func initLogd() {
 		exit(2)
 	}
 
-	errno := connect(uintptr(fd), unsafe.Pointer(&logdAddr), int32(unsafe.Sizeof(logdAddr)))
+	errno := connect(fd, unsafe.Pointer(&logdAddr), int32(unsafe.Sizeof(logdAddr)))
 	if errno < 0 {
 		msg := []byte("runtime: cannot connect to /dev/socket/logdw\x00")
 		write(2, unsafe.Pointer(&msg[0]), int32(len(msg)))

src/runtime/stubs_android.go

@@ -2,9 +2,15 @@ package runtime
 
 import "unsafe"
 
+// Return values of access/connect/socket are the return values of the syscall
+// (may encode error numbers).
+
+// int access(const char *, int)
 //go:noescape
 func access(name *byte, mode int32) int32
 
-func connect(fd uintptr, addr unsafe.Pointer, len int32) int32
+// int connect(int, const struct sockaddr*, socklen_t)
+func connect(fd int32, addr unsafe.Pointer, len int32) int32
 
+// int socket(int, int, int)
 func socket(domain int32, typ int32, prot int32) int32

src/runtime/sys_linux_amd64.s

@@ -442,3 +442,33 @@ TEXT runtime·closeonexec(SB),NOSPLIT,$0
 	MOVL	$72, AX  // fcntl
 	SYSCALL
 	RET
+
+
+// int access(const char *name, int mode)
+TEXT runtime·access(SB),NOSPLIT,$0
+	MOVQ	name+0(FP), DI
+	MOVL	mode+8(FP), SI
+	MOVL	$21, AX  // syscall entry
+	SYSCALL
+	MOVL	AX, ret+16(FP)
+	RET
+
+// int connect(int fd, const struct sockaddr *addr, socklen_t addrlen)
+TEXT runtime·connect(SB),NOSPLIT,$0-28
+	MOVL	fd+0(FP), DI
+	MOVQ	addr+8(FP), SI
+	MOVL	addrlen+16(FP), DX
+	MOVL	$42, AX  // syscall entry
+	SYSCALL
+	MOVL	AX, ret+24(FP)
+	RET
+
+// int socket(int domain, int type, int protocol)
+TEXT runtime·socket(SB),NOSPLIT,$0-20
+	MOVL	domain+0(FP), DI
+	MOVL	type+4(FP), SI
+	MOVL	protocol+8(FP), DX
+	MOVL	$41, AX  // syscall entry
+	SYSCALL
+	MOVL	AX, ret+16(FP)
+	RET