runtime: mlock signal stack on macOS/ARM64

Apparently, the macOS ARM64 kernel has a bug where when a signal
arrives and the signal stack is not currently faulted in, it may
kill the program with a SIGILL. Work around it by mlock the
signal stacks.

Fixes #42774.

Change-Id: I99a4b3fdb6d8af1c945725ddc2c25568d81c510a
Reviewed-on: https://go-review.googlesource.com/c/go/+/273686
Trust: Cherry Zhang <[email protected]>
Reviewed-by: Austin Clements <[email protected]>
Run-TryBot: Austin Clements <[email protected]>
TryBot-Result: Go Bot <[email protected]>

Author: cherrymui

src/runtime/os_darwin.go

@@ -283,6 +283,12 @@ func libpreinit() {
 func mpreinit(mp *m) {
 	mp.gsignal = malg(32 * 1024) // OS X wants >= 8K
 	mp.gsignal.m = mp
+	if GOOS == "darwin" && GOARCH == "arm64" {
+		// mlock the signal stack to work around a kernel bug where it may
+		// SIGILL when the signal stack is not faulted in while a signal
+		// arrives. See issue 42774.
+		mlock(unsafe.Pointer(mp.gsignal.stack.hi-physPageSize), physPageSize)
+	}
 }
 
 // Called to initialize a new m (including the bootstrap m).

src/runtime/sys_darwin.go

@@ -226,6 +226,13 @@ func madvise(addr unsafe.Pointer, n uintptr, flags int32) {
 }
 func madvise_trampoline()
 
+//go:nosplit
+//go:cgo_unsafe_args
+func mlock(addr unsafe.Pointer, n uintptr) {
+	libcCall(unsafe.Pointer(funcPC(mlock_trampoline)), unsafe.Pointer(&addr))
+}
+func mlock_trampoline()
+
 //go:nosplit
 //go:cgo_unsafe_args
 func read(fd int32, p unsafe.Pointer, n int32) int32 {
@@ -465,6 +472,7 @@ func setNonblock(fd int32) {
 //go:cgo_import_dynamic libc_mmap mmap "/usr/lib/libSystem.B.dylib"
 //go:cgo_import_dynamic libc_munmap munmap "/usr/lib/libSystem.B.dylib"
 //go:cgo_import_dynamic libc_madvise madvise "/usr/lib/libSystem.B.dylib"
+//go:cgo_import_dynamic libc_mlock mlock "/usr/lib/libSystem.B.dylib"
 //go:cgo_import_dynamic libc_error __error "/usr/lib/libSystem.B.dylib"
 //go:cgo_import_dynamic libc_usleep usleep "/usr/lib/libSystem.B.dylib"
 

src/runtime/sys_darwin_amd64.s

@@ -105,6 +105,9 @@ TEXT runtime·madvise_trampoline(SB), NOSPLIT, $0
 	POPQ	BP
 	RET
 
+TEXT runtime·mlock_trampoline(SB), NOSPLIT, $0
+	UNDEF // unimplemented
+
 GLOBL timebase<>(SB),NOPTR,$(machTimebaseInfo__size)
 
 TEXT runtime·nanotime_trampoline(SB),NOSPLIT,$0

src/runtime/sys_darwin_arm64.s

@@ -120,6 +120,12 @@ TEXT runtime·madvise_trampoline(SB),NOSPLIT,$0
 	BL	libc_madvise(SB)
 	RET
 
+TEXT runtime·mlock_trampoline(SB),NOSPLIT,$0
+	MOVD	8(R0), R1	// arg 2 len
+	MOVD	0(R0), R0	// arg 1 addr
+	BL	libc_mlock(SB)
+	RET
+
 TEXT runtime·setitimer_trampoline(SB),NOSPLIT,$0
 	MOVD	8(R0), R1	// arg 2 new
 	MOVD	16(R0), R2	// arg 3 old