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runtime: use sigaltstack on macOS/ARM64

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Currently we don't use sigaltstack on darwin/arm64, as is not
supported on iOS. However, it is supported on macOS. Use it.
(iOS remains unchanged.)

Change-Id: Icc154c5e2edf2dbdc8ca68741ad9157fc15a72ee
Reviewed-on: https://go-review.googlesource.com/c/go/+/256917
Trust: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Cherry Zhang 2020-09-12 12:33:24 -04:00
parent 04c7e32517
commit 28e549dec3
7 changed files with 27 additions and 19 deletions
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2
misc/cgo/test/sigaltstack.go
View File

@ -62,7 +62,7 @@ import (
func testSigaltstack(t *testing.T) {
switch {
case runtime.GOOS == "solaris", runtime.GOOS == "illumos", (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && runtime.GOARCH == "arm64":
case runtime.GOOS == "solaris", runtime.GOOS == "illumos", runtime.GOOS == "ios" && runtime.GOARCH == "arm64":
t.Skipf("switching signal stack not implemented on %s/%s", runtime.GOOS, runtime.GOARCH)
}

2
src/cmd/internal/obj/arm64/obj7.go
View File

@ -589,7 +589,7 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
q1.To.Reg = REGSP
q1.Spadj = c.autosize
if c.ctxt.Headtype == objabi.Hdarwin {
if objabi.GOOS == "ios" {
// iOS does not support SA_ONSTACK. We will run the signal handler
// on the G stack. If we write below SP, it may be clobbered by
// the signal handler. So we save LR after decrementing SP.

7
src/runtime/mkpreempt.go
View File

@ -340,12 +340,9 @@ func genARM64() {
p("MOVD R29, -8(RSP)") // save frame pointer (only used on Linux)
p("SUB $8, RSP, R29") // set up new frame pointer
p("#endif")
// On darwin, save the LR again after decrementing SP. We run the
// signal handler on the G stack (as it doesn't support SA_ONSTACK),
// On iOS, save the LR again after decrementing SP. We run the
// signal handler on the G stack (as it doesn't support sigaltstack),
// so any writes below SP may be clobbered.
p("#ifdef GOOS_darwin")
p("MOVD R30, (RSP)")
p("#endif")
p("#ifdef GOOS_ios")
p("MOVD R30, (RSP)")
p("#endif")

8
src/runtime/os_darwin.go
View File

@ -289,9 +289,9 @@ func mpreinit(mp *m) {
// Called to initialize a new m (including the bootstrap m).
// Called on the new thread, cannot allocate memory.
func minit() {
// The alternate signal stack is buggy on arm64.
// iOS does not support alternate signal stack.
// The signal handler handles it directly.
if GOARCH != "arm64" {
if !(GOOS == "ios" && GOARCH == "arm64") {
minitSignalStack()
}
minitSignalMask()
@ -301,9 +301,9 @@ func minit() {
// Called from dropm to undo the effect of an minit.
//go:nosplit
func unminit() {
// The alternate signal stack is buggy on arm64.
// iOS does not support alternate signal stack.
// See minit.
if GOARCH != "arm64" {
if !(GOOS == "ios" && GOARCH == "arm64") {
unminitSignals()
}
}

3
src/runtime/preempt_arm64.s
View File

@ -10,9 +10,6 @@ TEXT ·asyncPreempt(SB),NOSPLIT|NOFRAME,$0-0
MOVD R29, -8(RSP)
SUB $8, RSP, R29
#endif
#ifdef GOOS_darwin
MOVD R30, (RSP)
#endif
#ifdef GOOS_ios
MOVD R30, (RSP)
#endif

2
src/runtime/stack.go
View File

@ -66,7 +66,7 @@ const (
// to each stack below the usual guard area for OS-specific
// purposes like signal handling. Used on Windows, Plan 9,
// and iOS because they do not use a separate stack.
_StackSystem = sys.GoosWindows*512*sys.PtrSize + sys.GoosPlan9*512 + (sys.GoosDarwin+sys.GoosIos)*sys.GoarchArm64*1024
_StackSystem = sys.GoosWindows*512*sys.PtrSize + sys.GoosPlan9*512 + sys.GoosIos*sys.GoarchArm64*1024
// The minimum size of stack used by Go code
_StackMin = 2048

22
src/runtime/sys_darwin_arm64.s
View File

@ -202,6 +202,7 @@ TEXT runtime·sigtramp(SB),NOSPLIT,$192
BEQ 2(PC)
BL runtime·load_g(SB)
#ifdef GOOS_ios
MOVD RSP, R6
CMP $0, g
BEQ nog
@ -226,16 +227,21 @@ nog:
// Switch to gsignal stack.
MOVD R6, RSP
// Call sigtrampgo.
// Save arguments.
MOVW R0, (8*1)(RSP)
MOVD R1, (8*2)(RSP)
MOVD R2, (8*3)(RSP)
#endif
// Call sigtrampgo.
MOVD $runtime·sigtrampgo(SB), R11
BL (R11)
#ifdef GOOS_ios
// Switch to old stack.
MOVD (8*4)(RSP), R5
MOVD R5, RSP
#endif
// Restore callee-save registers.
MOVD (8*4)(RSP), R19
@ -329,12 +335,20 @@ TEXT runtime·fcntl_trampoline(SB),NOSPLIT,$0
ADD $16, RSP
RET
// sigaltstack on iOS is not supported and will always
// run the signal handler on the main stack, so our sigtramp has
// to do the stack switch ourselves.
TEXT runtime·sigaltstack_trampoline(SB),NOSPLIT,$0
#ifdef GOOS_ios
// sigaltstack on iOS is not supported and will always
// run the signal handler on the main stack, so our sigtramp has
// to do the stack switch ourselves.
MOVW $43, R0
BL libc_exit(SB)
#else
MOVD 8(R0), R1 // arg 2 old
MOVD 0(R0), R0 // arg 1 new
CALL libc_sigaltstack(SB)
CBZ R0, 2(PC)
BL notok<>(SB)
#endif
RET
// Thread related functions