runtime: fix exit1 arguments on Darwin

exit1 calls the bsdthread_terminate system call on Darwin. Currently
it passes no arguments on 386, arm, and arm64, and an exit status on
amd64. None of these are right. The signature of bsdthread_terminate
is:

int bsdthread_terminate(user_addr_t stackaddr, size_t freesize, uint32_t port, uint32_t sem);

Fix all of the Darwin exit1 implementations to call
bsdthread_terminate with 0 for all of these arguments so it doesn't
try to unmap some random memory, free some random port, or signal a
random semaphore.

This isn't a problem in practice because exit1 is never called.
However, we're about to start using exit1.

Change-Id: Idc534d196e3104e5253fc399553f21eb608693d7
Reviewed-on: https://go-review.googlesource.com/46036
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/sys_darwin_386.s

@@ -19,7 +19,13 @@ TEXT runtime·exit(SB),NOSPLIT,$0
 
 // Exit this OS thread (like pthread_exit, which eventually
 // calls __bsdthread_terminate).
-TEXT runtime·exit1(SB),NOSPLIT,$0
+TEXT runtime·exit1(SB),NOSPLIT,$16-0
+	// __bsdthread_terminate takes 4 word-size arguments.
+	// Set them all to 0. (None are an exit status.)
+	MOVL	$0, 0(SP)
+	MOVL	$0, 4(SP)
+	MOVL	$0, 8(SP)
+	MOVL	$0, 12(SP)
 	MOVL	$361, AX
 	INT	$0x80
 	JAE 2(PC)

src/runtime/sys_darwin_amd64.s

@@ -26,12 +26,19 @@ TEXT runtime·exit(SB),NOSPLIT,$0
 // Exit this OS thread (like pthread_exit, which eventually
 // calls __bsdthread_terminate).
 TEXT runtime·exit1(SB),NOSPLIT,$0
-	MOVL	code+0(FP), DI		// arg 1 exit status
+	// __bsdthread_terminate takes 4 word-size arguments.
+	// Set them all to 0. (None are an exit status.)
+	MOVL	$0, DI
+	MOVL	$0, SI
+	MOVL	$0, DX
+	MOVL	$0, R10
 	MOVL	$(0x2000000+361), AX	// syscall entry
 	SYSCALL
 	MOVL	$0xf1, 0xf1  // crash
 	RET
 
+
+
 TEXT runtime·open(SB),NOSPLIT,$0
 	MOVQ	name+0(FP), DI		// arg 1 pathname
 	MOVL	mode+8(FP), SI		// arg 2 flags

src/runtime/sys_darwin_arm.s

@@ -90,6 +90,12 @@ TEXT runtime·exit(SB),NOSPLIT,$-4
 // Exit this OS thread (like pthread_exit, which eventually
 // calls __bsdthread_terminate).
 TEXT runtime·exit1(SB),NOSPLIT,$0
+	// __bsdthread_terminate takes 4 word-size arguments.
+	// Set them all to 0. (None are an exit status.)
+	MOVW	$0, R0
+	MOVW	$0, R1
+	MOVW	$0, R2
+	MOVW	$0, R3
 	MOVW	$SYS_bsdthread_terminate, R12
 	SWI	$0x80
 	MOVW	$1234, R0

src/runtime/sys_darwin_arm64.s

@@ -90,6 +90,12 @@ TEXT runtime·exit(SB),NOSPLIT,$-8
 // Exit this OS thread (like pthread_exit, which eventually
 // calls __bsdthread_terminate).
 TEXT runtime·exit1(SB),NOSPLIT,$0
+	// __bsdthread_terminate takes 4 word-size arguments.
+	// Set them all to 0. (None are an exit status.)
+	MOVW	$0, R0
+	MOVW	$0, R1
+	MOVW	$0, R2
+	MOVW	$0, R3
 	MOVW	$SYS_bsdthread_terminate, R16
 	SVC	$0x80
 	MOVD	$1234, R0