Commit fded5dbb authored by Ian Lance Taylor's avatar Ian Lance Taylor

runtime: don't crash if signal delivered on g0 stack

Also, if we changed the gsignal stack to match the stack we are
executing on, restore it when returning from the signal handler, for
safety.

Fixes #18255.

Change-Id: Ic289b36e4e38a56f8a6d4b5d74f68121c242e81a
Reviewed-on: https://go-review.googlesource.com/34239
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: default avatarBryan Mills <bcmills@google.com>
Reviewed-by: default avatarDavid Crawshaw <crawshaw@golang.org>
parent 265e5476
......@@ -145,6 +145,7 @@ if test "$tsan" = "yes"; then
testtsan tsan3.go
testtsan tsan4.go
testtsan tsan8.go
testtsan tsan9.go
# These tests are only reliable using clang or GCC version 7 or later.
# Otherwise runtime/cgo/libcgo.h can't tell whether TSAN is in use.
......
// Copyright 2016 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.
package main
// This program failed when run under the C/C++ ThreadSanitizer. The
// TSAN library was not keeping track of whether signals should be
// delivered on the alternate signal stack.
/*
#cgo CFLAGS: -g -fsanitize=thread
#cgo LDFLAGS: -g -fsanitize=thread
#include <stdlib.h>
#include <sys/time.h>
void spin() {
size_t n;
struct timeval tvstart, tvnow;
int diff;
gettimeofday(&tvstart, NULL);
for (n = 0; n < 1<<20; n++) {
free(malloc(n));
gettimeofday(&tvnow, NULL);
diff = (tvnow.tv_sec - tvstart.tv_sec) * 1000 * 1000 + (tvnow.tv_usec - tvstart.tv_usec);
// Profile frequency is 100Hz so we should definitely
// get a signal in 50 milliseconds.
if (diff > 50 * 1000) {
break;
}
}
}
*/
import "C"
import (
"io/ioutil"
"runtime/pprof"
"time"
)
func goSpin() {
start := time.Now()
for n := 0; n < 1<<20; n++ {
_ = make([]byte, n)
if time.Since(start) > 50*time.Millisecond {
break
}
}
}
func main() {
pprof.StartCPUProfile(ioutil.Discard)
go C.spin()
goSpin()
pprof.StopCPUProfile()
}
......@@ -212,8 +212,24 @@ func sigtrampgo(sig uint32, info *siginfo, ctx unsafe.Pointer) {
}
// If some non-Go code called sigaltstack, adjust.
setStack := false
var gsignalStack gsignalStack
sp := uintptr(unsafe.Pointer(&sig))
if sp < g.m.gsignal.stack.lo || sp >= g.m.gsignal.stack.hi {
if sp >= g.m.g0.stack.lo && sp < g.m.g0.stack.hi {
// The signal was delivered on the g0 stack.
// This can happen when linked with C code
// using the thread sanitizer, which collects
// signals then delivers them itself by calling
// the signal handler directly when C code,
// including C code called via cgo, calls a
// TSAN-intercepted function such as malloc.
st := stackt{ss_size: g.m.g0.stack.hi - g.m.g0.stack.lo}
setSignalstackSP(&st, g.m.g0.stack.lo)
setGsignalStack(&st, &gsignalStack)
g.m.gsignal.stktopsp = getcallersp(unsafe.Pointer(&sig))
setStack = true
} else {
var st stackt
sigaltstack(nil, &st)
if st.ss_flags&_SS_DISABLE != 0 {
......@@ -229,8 +245,10 @@ func sigtrampgo(sig uint32, info *siginfo, ctx unsafe.Pointer) {
sigNotOnStack(sig)
dropm()
}
setGsignalStack(&st)
setGsignalStack(&st, &gsignalStack)
g.m.gsignal.stktopsp = getcallersp(unsafe.Pointer(&sig))
setStack = true
}
}
setg(g.m.gsignal)
......@@ -238,6 +256,9 @@ func sigtrampgo(sig uint32, info *siginfo, ctx unsafe.Pointer) {
c.fixsigcode(sig)
sighandler(sig, info, ctx, g)
setg(g)
if setStack {
restoreGsignalStack(&gsignalStack)
}
}
// sigpanic turns a synchronous signal into a run-time panic.
......@@ -585,7 +606,7 @@ func minitSignalStack() {
signalstack(&_g_.m.gsignal.stack)
_g_.m.newSigstack = true
} else {
setGsignalStack(&st)
setGsignalStack(&st, nil)
_g_.m.newSigstack = false
}
}
......@@ -618,14 +639,32 @@ func unminitSignals() {
}
}
// gsignalStack saves the fields of the gsignal stack changed by
// setGsignalStack.
type gsignalStack struct {
stack stack
stackguard0 uintptr
stackguard1 uintptr
stackAlloc uintptr
stktopsp uintptr
}
// setGsignalStack sets the gsignal stack of the current m to an
// alternate signal stack returned from the sigaltstack system call.
// It saves the old values in *old for use by restoreGsignalStack.
// This is used when handling a signal if non-Go code has set the
// alternate signal stack.
//go:nosplit
//go:nowritebarrierrec
func setGsignalStack(st *stackt) {
func setGsignalStack(st *stackt, old *gsignalStack) {
g := getg()
if old != nil {
old.stack = g.m.gsignal.stack
old.stackguard0 = g.m.gsignal.stackguard0
old.stackguard1 = g.m.gsignal.stackguard1
old.stackAlloc = g.m.gsignal.stackAlloc
old.stktopsp = g.m.gsignal.stktopsp
}
stsp := uintptr(unsafe.Pointer(st.ss_sp))
g.m.gsignal.stack.lo = stsp
g.m.gsignal.stack.hi = stsp + st.ss_size
......@@ -634,6 +673,19 @@ func setGsignalStack(st *stackt) {
g.m.gsignal.stackAlloc = st.ss_size
}
// restoreGsignalStack restores the gsignal stack to the value it had
// before entering the signal handler.
//go:nosplit
//go:nowritebarrierrec
func restoreGsignalStack(st *gsignalStack) {
gp := getg().m.gsignal
gp.stack = st.stack
gp.stackguard0 = st.stackguard0
gp.stackguard1 = st.stackguard1
gp.stackAlloc = st.stackAlloc
gp.stktopsp = st.stktopsp
}
// signalstack sets the current thread's alternate signal stack to s.
//go:nosplit
func signalstack(s *stack) {
......
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