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runtime: for c-archive/c-shared, don't install unnecessary signal handlers

Browse Source 
Only install signal handlers for synchronous signals that become
run-time panics.  Set the SA_ONSTACK flag for other signal handlers as
needed.

Fixes #13028.
Update #12465.
Update #13034.
Update #13042.

Change-Id: I28375e70641f60630e10f3c86e24b6e4f8a35cc9
Reviewed-on: https://go-review.googlesource.com/17903
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Ian Lance Taylor 2015-12-16 12:16:17 -08:00
parent 32cf985d1a
commit fbdfa99246
12 changed files with 635 additions and 21 deletions
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185
misc/cgo/testcarchive/main2.c Normal file
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@ -0,0 +1,185 @@
// Copyright 2015 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.
// Test installing a signal handler before the Go code starts.
// This is a lot like misc/cgo/testcshared/main4.c.
#include <setjmp.h>
#include <signal.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include <sched.h>
#include <time.h>
#include "libgo2.h"
static void die(const char* msg) {
perror(msg);
exit(EXIT_FAILURE);
}
static volatile sig_atomic_t sigioSeen;
// Use up some stack space.
static void recur(int i, char *p) {
char a[1024];
*p = '\0';
if (i > 0) {
recur(i - 1, a);
}
}
// Signal handler that uses up more stack space than a goroutine will have.
static void ioHandler(int signo, siginfo_t* info, void* ctxt) {
char a[1024];
recur(4, a);
sigioSeen = 1;
}
static jmp_buf jmp;
static char* nullPointer;
// Signal handler for SIGSEGV on a C thread.
static void segvHandler(int signo, siginfo_t* info, void* ctxt) {
sigset_t mask;
int i;
if (sigemptyset(&mask) < 0) {
die("sigemptyset");
}
if (sigaddset(&mask, SIGSEGV) < 0) {
die("sigaddset");
}
i = sigprocmask(SIG_UNBLOCK, &mask, NULL);
if (i != 0) {
fprintf(stderr, "sigprocmask: %s\n", strerror(i));
exit(EXIT_FAILURE);
}
// Don't try this at home.
longjmp(jmp, signo);
// We should never get here.
abort();
}
// Set up the signal handlers in a high priority constructor,
// so that they are installed before the Go code starts.
static void init(void) __attribute__ ((constructor (200)));
static void init() {
struct sigaction sa;
memset(&sa, 0, sizeof sa);
sa.sa_sigaction = ioHandler;
if (sigemptyset(&sa.sa_mask) < 0) {
die("sigemptyset");
}
sa.sa_flags = SA_SIGINFO;
if (sigaction(SIGIO, &sa, NULL) < 0) {
die("sigaction");
}
sa.sa_sigaction = segvHandler;
if (sigaction(SIGSEGV, &sa, NULL) < 0 || sigaction(SIGBUS, &sa, NULL) < 0) {
die("sigaction");
}
}
int main(int argc, char** argv) {
int verbose;
sigset_t mask;
int i;
verbose = argc > 1;
setvbuf(stdout, NULL, _IONBF, 0);
// Call setsid so that we can use kill(0, SIGIO) below.
// Don't check the return value so that this works both from
// a job control shell and from a shell script.
setsid();
if (verbose) {
printf("calling RunGoroutines\n");
}
RunGoroutines();
// Block SIGIO in this thread to make it more likely that it
// will be delivered to a goroutine.
if (verbose) {
printf("calling pthread_sigmask\n");
}
if (sigemptyset(&mask) < 0) {
die("sigemptyset");
}
if (sigaddset(&mask, SIGIO) < 0) {
die("sigaddset");
}
i = pthread_sigmask(SIG_BLOCK, &mask, NULL);
if (i != 0) {
fprintf(stderr, "pthread_sigmask: %s\n", strerror(i));
exit(EXIT_FAILURE);
}
if (verbose) {
printf("calling kill\n");
}
if (kill(0, SIGIO) < 0) {
die("kill");
}
if (verbose) {
printf("waiting for sigioSeen\n");
}
// Wait until the signal has been delivered.
i = 0;
while (!sigioSeen) {
if (sched_yield() < 0) {
perror("sched_yield");
}
i++;
if (i > 10000) {
fprintf(stderr, "looping too long waiting for signal\n");
exit(EXIT_FAILURE);
}
}
if (verbose) {
printf("calling setjmp\n");
}
// Test that a SIGSEGV on this thread is delivered to us.
if (setjmp(jmp) == 0) {
if (verbose) {
printf("triggering SIGSEGV\n");
}
*nullPointer = '\0';
fprintf(stderr, "continued after address error\n");
exit(EXIT_FAILURE);
}
if (verbose) {
printf("calling TestSEGV\n");
}
TestSEGV();
printf("PASS\n");
return 0;
}

45
misc/cgo/testcarchive/src/libgo2/libgo2.go Normal file
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@ -0,0 +1,45 @@
// Copyright 2015 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
import "C"
import (
"fmt"
"os"
"runtime"
)
// RunGoroutines starts some goroutines that don't do anything.
// The idea is to get some threads going, so that a signal will be delivered
// to a thread started by Go.
//export RunGoroutines
func RunGoroutines() {
for i := 0; i < 4; i++ {
go func() {
runtime.LockOSThread()
select {}
}()
}
}
var P *byte
// TestSEGV makes sure that an invalid address turns into a run-time Go panic.
//export TestSEGV
func TestSEGV() {
defer func() {
if recover() == nil {
fmt.Fprintln(os.Stderr, "no panic from segv")
os.Exit(1)
}
}()
*P = 0
fmt.Fprintln(os.Stderr, "continued after segv")
os.Exit(1)
}
func main() {
}

27
misc/cgo/testcarchive/test.bash
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@ -23,11 +23,16 @@ fi
rm -rf libgo.a libgo.h testp pkg
status=0
# Installing first will create the header files we want.
GOPATH=$(pwd) go install -buildmode=c-archive libgo
$(go env CC) $(go env GOGCCFLAGS) $ccargs -o testp main.c pkg/$(go env GOOS)_$(go env GOARCH)/libgo.a
$bin arg1 arg2
if ! $bin arg1 arg2; then
echo "FAIL test1"
status=1
fi
rm -f libgo.a libgo.h testp
# Test building libgo other than installing it.
@ -35,10 +40,26 @@ rm -f libgo.a libgo.h testp
GOPATH=$(pwd) go build -buildmode=c-archive src/libgo/libgo.go
$(go env CC) $(go env GOGCCFLAGS) $ccargs -o testp main.c libgo.a
$bin arg1 arg2
if ! $bin arg1 arg2; then
echo "FAIL test2"
status=1
fi
rm -f libgo.a libgo.h testp
GOPATH=$(pwd) go build -buildmode=c-archive -o libgo.a libgo
$(go env CC) $(go env GOGCCFLAGS) $ccargs -o testp main.c libgo.a
$bin arg1 arg2
if ! $bin arg1 arg2; then
echo "FAIL test3"
status=1
fi
rm -rf libgo.a libgo.h testp pkg
GOPATH=$(pwd) go build -buildmode=c-archive -o libgo2.a libgo2
$(go env CC) $(go env GOGCCFLAGS) $ccargs -o testp main2.c libgo2.a
if ! $bin; then
echo "FAIL test4"
status=1
fi
rm -rf libgo2.a libgo2.h testp pkg
exit $status

214
misc/cgo/testcshared/main4.c Normal file
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@ -0,0 +1,214 @@
// Copyright 2015 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.
// Test that a signal handler that uses up stack space does not crash
// if the signal is delivered to a thread running a goroutine.
// This is a lot like misc/cgo/testcarchive/main2.c.
#include <setjmp.h>
#include <signal.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include <sched.h>
#include <time.h>
#include <dlfcn.h>
static void die(const char* msg) {
perror(msg);
exit(EXIT_FAILURE);
}
static volatile sig_atomic_t sigioSeen;
// Use up some stack space.
static void recur(int i, char *p) {
char a[1024];
*p = '\0';
if (i > 0) {
recur(i - 1, a);
}
}
// Signal handler that uses up more stack space than a goroutine will have.
static void ioHandler(int signo, siginfo_t* info, void* ctxt) {
char a[1024];
recur(4, a);
sigioSeen = 1;
}
static jmp_buf jmp;
static char* nullPointer;
// Signal handler for SIGSEGV on a C thread.
static void segvHandler(int signo, siginfo_t* info, void* ctxt) {
sigset_t mask;
int i;
if (sigemptyset(&mask) < 0) {
die("sigemptyset");
}
if (sigaddset(&mask, SIGSEGV) < 0) {
die("sigaddset");
}
i = sigprocmask(SIG_UNBLOCK, &mask, NULL);
if (i != 0) {
fprintf(stderr, "sigprocmask: %s\n", strerror(i));
exit(EXIT_FAILURE);
}
// Don't try this at home.
longjmp(jmp, signo);
// We should never get here.
abort();
}
int main(int argc, char** argv) {
int verbose;
struct sigaction sa;
void* handle;
void (*fn)(void);
sigset_t mask;
int i;
verbose = argc > 2;
setvbuf(stdout, NULL, _IONBF, 0);
// Call setsid so that we can use kill(0, SIGIO) below.
// Don't check the return value so that this works both from
// a job control shell and from a shell script.
setsid();
if (verbose) {
printf("calling sigaction\n");
}
memset(&sa, 0, sizeof sa);
sa.sa_sigaction = ioHandler;
if (sigemptyset(&sa.sa_mask) < 0) {
die("sigemptyset");
}
sa.sa_flags = SA_SIGINFO;
if (sigaction(SIGIO, &sa, NULL) < 0) {
die("sigaction");
}
sa.sa_sigaction = segvHandler;
if (sigaction(SIGSEGV, &sa, NULL) < 0 || sigaction(SIGBUS, &sa, NULL) < 0) {
die("sigaction");
}
if (verbose) {
printf("calling dlopen\n");
}
handle = dlopen(argv[1], RTLD_NOW | RTLD_GLOBAL);
if (handle == NULL) {
fprintf(stderr, "%s\n", dlerror());
exit(EXIT_FAILURE);
}
if (verbose) {
printf("calling dlsym\n");
}
// Start some goroutines.
fn = (void(*)(void))dlsym(handle, "RunGoroutines");
if (fn == NULL) {
fprintf(stderr, "%s\n", dlerror());
exit(EXIT_FAILURE);
}
if (verbose) {
printf("calling RunGoroutines\n");
}
fn();
// Block SIGIO in this thread to make it more likely that it
// will be delivered to a goroutine.
if (verbose) {
printf("calling pthread_sigmask\n");
}
if (sigemptyset(&mask) < 0) {
die("sigemptyset");
}
if (sigaddset(&mask, SIGIO) < 0) {
die("sigaddset");
}
i = pthread_sigmask(SIG_BLOCK, &mask, NULL);
if (i != 0) {
fprintf(stderr, "pthread_sigmask: %s\n", strerror(i));
exit(EXIT_FAILURE);
}
if (verbose) {
printf("calling kill\n");
}
if (kill(0, SIGIO) < 0) {
die("kill");
}
if (verbose) {
printf("waiting for sigioSeen\n");
}
// Wait until the signal has been delivered.
i = 0;
while (!sigioSeen) {
if (sched_yield() < 0) {
perror("sched_yield");
}
i++;
if (i > 10000) {
fprintf(stderr, "looping too long waiting for signal\n");
exit(EXIT_FAILURE);
}
}
if (verbose) {
printf("calling setjmp\n");
}
// Test that a SIGSEGV on this thread is delivered to us.
if (setjmp(jmp) == 0) {
if (verbose) {
printf("triggering SIGSEGV\n");
}
*nullPointer = '\0';
fprintf(stderr, "continued after address error\n");
exit(EXIT_FAILURE);
}
if (verbose) {
printf("calling dlsym\n");
}
// Make sure that a SIGSEGV in Go causes a run-time panic.
fn = (void (*)(void))dlsym(handle, "TestSEGV");
if (fn == NULL) {
fprintf(stderr, "%s\n", dlerror());
exit(EXIT_FAILURE);
}
if (verbose) {
printf("calling TestSEGV\n");
}
fn();
printf("PASS\n");
return 0;
}

45
misc/cgo/testcshared/src/libgo4/libgo4.go Normal file
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@ -0,0 +1,45 @@
// Copyright 2015 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
import "C"
import (
"fmt"
"os"
"runtime"
)
// RunGoroutines starts some goroutines that don't do anything.
// The idea is to get some threads going, so that a signal will be delivered
// to a thread started by Go.
//export RunGoroutines
func RunGoroutines() {
for i := 0; i < 4; i++ {
go func() {
runtime.LockOSThread()
select {}
}()
}
}
var P *byte
// TestSEGV makes sure that an invalid address turns into a run-time Go panic.
//export TestSEGV
func TestSEGV() {
defer func() {
if recover() == nil {
fmt.Fprintln(os.Stderr, "no panic from segv")
os.Exit(1)
}
}()
*P = 0
fmt.Fprintln(os.Stderr, "continued after segv")
os.Exit(1)
}
func main() {
}

38
misc/cgo/testcshared/test.bash
View File

@ -28,9 +28,9 @@ fi
androidpath=/data/local/tmp/testcshared-$$
function cleanup() {
rm -rf libgo.$libext libgo2.$libext libgo.h testp testp2 testp3 pkg
rm -rf $(go env GOROOT)/${installdir}
rm -f libgo.$libext libgo2.$libext libgo4.$libext libgo.h libgo4.h
rm -f testp testp2 testp3 testp4
rm -rf pkg $(go env GOROOT)/${installdir}
if [ "$goos" == "android" ]; then
adb shell rm -rf $androidpath
@ -93,6 +93,8 @@ if [ "$goos" == "android" ]; then
GOGCCFLAGS="${GOGCCFLAGS} -pie"
fi
status=0
# test0: exported symbols in shared lib are accessible.
# TODO(iant): using _shared here shouldn't really be necessary.
$(go env CC) ${GOGCCFLAGS} -I ${installdir} -o testp main0.c libgo.$libext
@ -101,7 +103,7 @@ binpush testp
output=$(run LD_LIBRARY_PATH=. ./testp)
if [ "$output" != "PASS" ]; then
echo "FAIL test0 got ${output}"
exit 1
status=1
fi
# test1: shared library can be dynamically loaded and exported symbols are accessible.
@ -110,7 +112,7 @@ binpush testp
output=$(run ./testp ./libgo.$libext)
if [ "$output" != "PASS" ]; then
echo "FAIL test1 got ${output}"
exit 1
status=1
fi
# test2: tests libgo2 which does not export any functions.
@ -125,7 +127,7 @@ binpush testp2
output=$(run LD_LIBRARY_PATH=. ./testp2)
if [ "$output" != "PASS" ]; then
echo "FAIL test2 got ${output}"
exit 1
status=1
fi
# test3: tests main.main is exported on android.
@ -135,7 +137,27 @@ if [ "$goos" == "android" ]; then
output=$(run ./testp ./libgo.so)
if [ "$output" != "PASS" ]; then
echo "FAIL test3 got ${output}"
exit 1
status=1
fi
fi
echo "ok"
# test4: tests signal handlers
GOPATH=$(pwd) go build -buildmode=c-shared $suffix -o libgo4.$libext libgo4
binpush libgo4.$libext
$(go env CC) ${GOGCCFLAGS} -pthread -o testp4 main4.c -ldl
binpush testp4
output=$(run ./testp4 ./libgo4.$libext 2>&1)
if test "$output" != "PASS"; then
echo "FAIL test4 got ${output}"
if test "$goos" != "android"; then
echo "re-running test4 in verbose mode"
./testp4 ./libgo4.$libext verbose
fi
status=1
fi
if test $status = 0; then
echo "ok"
fi
exit $status

60
misc/cgo/testsigfwd/main.go
View File

@ -7,9 +7,14 @@ package main
import "fmt"
/*
#cgo CFLAGS: -pthread
#cgo LDFLAGS: -pthread
#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <pthread.h>
int *p;
static void sigsegv() {
@ -18,16 +23,65 @@ static void sigsegv() {
exit(2);
}
static void sighandler(int signum) {
static void segvhandler(int signum) {
if (signum == SIGSEGV) {
exit(0); // success
}
}
static volatile sig_atomic_t sigioSeen;
// Use up some stack space.
static void recur(int i, char *p) {
char a[1024];
*p = '\0';
if (i > 0) {
recur(i - 1, a);
}
}
static void iohandler(int signum) {
char a[1024];
recur(4, a);
sigioSeen = 1;
}
static void* sigioThread(void* arg __attribute__ ((unused))) {
raise(SIGIO);
}
static void sigioOnThread() {
pthread_t tid;
int i;
pthread_create(&tid, NULL, sigioThread, NULL);
pthread_join(tid, NULL);
// Wait until the signal has been delivered.
i = 0;
while (!sigioSeen) {
if (sched_yield() < 0) {
perror("sched_yield");
}
i++;
if (i > 10000) {
fprintf(stderr, "looping too long waiting for signal\n");
exit(EXIT_FAILURE);
}
}
}
static void __attribute__ ((constructor)) sigsetup(void) {
struct sigaction act;
act.sa_handler = &sighandler;
sigaction(SIGSEGV, &act, 0);
memset(&act, 0, sizeof act);
act.sa_handler = segvhandler;
sigaction(SIGSEGV, &act, NULL);
act.sa_handler = iohandler;
sigaction(SIGIO, &act, NULL);
}
*/
import "C"

13
src/os/signal/doc.go
View File

@ -156,14 +156,19 @@ If the Go runtime sees an existing signal handler for the SIGCANCEL or
SIGSETXID signals (which are used only on GNU/Linux), it will turn on
the SA_ONSTACK flag and otherwise keep the signal handler.
For other signals listed above, the Go runtime will install a signal
For the synchronous signals, the Go runtime will install a signal
handler. It will save any existing signal handler. If a synchronous
signal arrives while executing non-Go code, the Go runtime will invoke
the existing signal handler instead of the Go signal handler.
If a signal is delivered to a non-Go thread, it will act as described
above, except that if there is an existing non-Go signal handler, that
handler will be installed before raising the signal.
Go code built with -buildmode=c-archive or -buildmode=c-shared will
not install any other signal handlers. TODO: Describe Notify behavior.
Go code built otherwise will install a signal handler for the
asynchronous signals listed above, and save any existing signal
handler. If a signal is delivered to a non-Go thread, it will act as
described above, except that if there is an existing non-Go signal
handler, that handler will be installed before raising the signal.
Windows

8
src/runtime/signal1_unix.go
View File

@ -65,6 +65,14 @@ func initsig() {
continue
}
// When built using c-archive or c-shared, only
// install signal handlers for synchronous signals.
// Set SA_ONSTACK for other signals if necessary.
if (isarchive || islibrary) && t.flags&_SigPanic == 0 {
setsigstack(i)
continue
}
t.flags |= _SigHandling
setsig(i, funcPC(sighandler), true)
}

11
src/runtime/signal2_unix.go
View File

@ -16,8 +16,6 @@ func sigfwd(fn uintptr, sig uint32, info *siginfo, ctx unsafe.Pointer)
// signal was forwarded.
//go:nosplit
func sigfwdgo(sig uint32, info *siginfo, ctx unsafe.Pointer) bool {
g := getg()
c := &sigctxt{info, ctx}
if sig >= uint32(len(sigtable)) {
return false
}
@ -28,13 +26,22 @@ func sigfwdgo(sig uint32, info *siginfo, ctx unsafe.Pointer) bool {
if fwdFn == _SIG_DFL {
return false
}
// If we aren't handling the signal, forward it.
if flags&_SigHandling == 0 {
sigfwd(fwdFn, sig, info, ctx)
return true
}
// Only forward synchronous signals.
c := &sigctxt{info, ctx}
if c.sigcode() == _SI_USER || flags&_SigPanic == 0 {
return false
}
// Determine if the signal occurred inside Go code. We test that:
// (1) we were in a goroutine (i.e., m.curg != nil), and
// (2) we weren't in CGO (i.e., m.curg.syscallsp == 0).
g := getg()
if g != nil && g.m != nil && g.m.curg != nil && g.m.curg.syscallsp == 0 {
return false
}

6
src/runtime/sys_darwin_amd64.s
View File

@ -214,10 +214,14 @@ TEXT runtime·sigaction(SB),NOSPLIT,$0-24
TEXT runtime·sigfwd(SB),NOSPLIT,$0-32
MOVQ fn+0(FP), AX
MOVQ sig+8(FP), DI
MOVL sig+8(FP), DI
MOVQ info+16(FP), SI
MOVQ ctx+24(FP), DX
MOVQ SP, BP
SUBQ $64, SP
ANDQ $~15, SP // alignment for x86_64 ABI
CALL AX
MOVQ BP, SP
RET
TEXT runtime·sigreturn(SB),NOSPLIT,$0-12

4
src/runtime/sys_linux_arm.s
View File

@ -339,7 +339,11 @@ TEXT runtime·sigfwd(SB),NOSPLIT,$0-16
MOVW info+8(FP), R1
MOVW ctx+12(FP), R2
MOVW fn+0(FP), R11
MOVW R13, R4
SUB $24, R13
BIC $0x7, R13 // alignment for ELF ABI
BL (R11)
MOVW R4, R13
RET
TEXT runtime·sigtramp(SB),NOSPLIT,$12