-
Notifications
You must be signed in to change notification settings - Fork 17.6k
/
signal_unix.go
1217 lines (1093 loc) · 37.1 KB
/
signal_unix.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
// Copyright 2012 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.
// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
package runtime
import (
"runtime/internal/atomic"
"unsafe"
)
// sigTabT is the type of an entry in the global sigtable array.
// sigtable is inherently system dependent, and appears in OS-specific files,
// but sigTabT is the same for all Unixy systems.
// The sigtable array is indexed by a system signal number to get the flags
// and printable name of each signal.
type sigTabT struct {
flags int32
name string
}
//go:linkname os_sigpipe os.sigpipe
func os_sigpipe() {
systemstack(sigpipe)
}
func signame(sig uint32) string {
if sig >= uint32(len(sigtable)) {
return ""
}
return sigtable[sig].name
}
const (
_SIG_DFL uintptr = 0
_SIG_IGN uintptr = 1
)
// sigPreempt is the signal used for non-cooperative preemption.
//
// There's no good way to choose this signal, but there are some
// heuristics:
//
// 1. It should be a signal that's passed-through by debuggers by
// default. On Linux, this is SIGALRM, SIGURG, SIGCHLD, SIGIO,
// SIGVTALRM, SIGPROF, and SIGWINCH, plus some glibc-internal signals.
//
// 2. It shouldn't be used internally by libc in mixed Go/C binaries
// because libc may assume it's the only thing that can handle these
// signals. For example SIGCANCEL or SIGSETXID.
//
// 3. It should be a signal that can happen spuriously without
// consequences. For example, SIGALRM is a bad choice because the
// signal handler can't tell if it was caused by the real process
// alarm or not (arguably this means the signal is broken, but I
// digress). SIGUSR1 and SIGUSR2 are also bad because those are often
// used in meaningful ways by applications.
//
// 4. We need to deal with platforms without real-time signals (like
// macOS), so those are out.
//
// We use SIGURG because it meets all of these criteria, is extremely
// unlikely to be used by an application for its "real" meaning (both
// because out-of-band data is basically unused and because SIGURG
// doesn't report which socket has the condition, making it pretty
// useless), and even if it is, the application has to be ready for
// spurious SIGURG. SIGIO wouldn't be a bad choice either, but is more
// likely to be used for real.
const sigPreempt = _SIGURG
// Stores the signal handlers registered before Go installed its own.
// These signal handlers will be invoked in cases where Go doesn't want to
// handle a particular signal (e.g., signal occurred on a non-Go thread).
// See sigfwdgo for more information on when the signals are forwarded.
//
// This is read by the signal handler; accesses should use
// atomic.Loaduintptr and atomic.Storeuintptr.
var fwdSig [_NSIG]uintptr
// handlingSig is indexed by signal number and is non-zero if we are
// currently handling the signal. Or, to put it another way, whether
// the signal handler is currently set to the Go signal handler or not.
// This is uint32 rather than bool so that we can use atomic instructions.
var handlingSig [_NSIG]uint32
// channels for synchronizing signal mask updates with the signal mask
// thread
var (
disableSigChan chan uint32
enableSigChan chan uint32
maskUpdatedChan chan struct{}
)
func init() {
// _NSIG is the number of signals on this operating system.
// sigtable should describe what to do for all the possible signals.
if len(sigtable) != _NSIG {
print("runtime: len(sigtable)=", len(sigtable), " _NSIG=", _NSIG, "\n")
throw("bad sigtable len")
}
}
var signalsOK bool
// Initialize signals.
// Called by libpreinit so runtime may not be initialized.
//go:nosplit
//go:nowritebarrierrec
func initsig(preinit bool) {
if !preinit {
// It's now OK for signal handlers to run.
signalsOK = true
}
// For c-archive/c-shared this is called by libpreinit with
// preinit == true.
if (isarchive || islibrary) && !preinit {
return
}
for i := uint32(0); i < _NSIG; i++ {
t := &sigtable[i]
if t.flags == 0 || t.flags&_SigDefault != 0 {
continue
}
// We don't need to use atomic operations here because
// there shouldn't be any other goroutines running yet.
fwdSig[i] = getsig(i)
if !sigInstallGoHandler(i) {
// Even if we are not installing a signal handler,
// set SA_ONSTACK if necessary.
if fwdSig[i] != _SIG_DFL && fwdSig[i] != _SIG_IGN {
setsigstack(i)
} else if fwdSig[i] == _SIG_IGN {
sigInitIgnored(i)
}
continue
}
handlingSig[i] = 1
setsig(i, funcPC(sighandler))
}
}
//go:nosplit
//go:nowritebarrierrec
func sigInstallGoHandler(sig uint32) bool {
// For some signals, we respect an inherited SIG_IGN handler
// rather than insist on installing our own default handler.
// Even these signals can be fetched using the os/signal package.
switch sig {
case _SIGHUP, _SIGINT:
if atomic.Loaduintptr(&fwdSig[sig]) == _SIG_IGN {
return false
}
}
t := &sigtable[sig]
if t.flags&_SigSetStack != 0 {
return false
}
// When built using c-archive or c-shared, only install signal
// handlers for synchronous signals and SIGPIPE.
if (isarchive || islibrary) && t.flags&_SigPanic == 0 && sig != _SIGPIPE {
return false
}
return true
}
// sigenable enables the Go signal handler to catch the signal sig.
// It is only called while holding the os/signal.handlers lock,
// via os/signal.enableSignal and signal_enable.
func sigenable(sig uint32) {
if sig >= uint32(len(sigtable)) {
return
}
// SIGPROF is handled specially for profiling.
if sig == _SIGPROF {
return
}
t := &sigtable[sig]
if t.flags&_SigNotify != 0 {
ensureSigM()
enableSigChan <- sig
<-maskUpdatedChan
if atomic.Cas(&handlingSig[sig], 0, 1) {
atomic.Storeuintptr(&fwdSig[sig], getsig(sig))
setsig(sig, funcPC(sighandler))
}
}
}
// sigdisable disables the Go signal handler for the signal sig.
// It is only called while holding the os/signal.handlers lock,
// via os/signal.disableSignal and signal_disable.
func sigdisable(sig uint32) {
if sig >= uint32(len(sigtable)) {
return
}
// SIGPROF is handled specially for profiling.
if sig == _SIGPROF {
return
}
t := &sigtable[sig]
if t.flags&_SigNotify != 0 {
ensureSigM()
disableSigChan <- sig
<-maskUpdatedChan
// If initsig does not install a signal handler for a
// signal, then to go back to the state before Notify
// we should remove the one we installed.
if !sigInstallGoHandler(sig) {
atomic.Store(&handlingSig[sig], 0)
setsig(sig, atomic.Loaduintptr(&fwdSig[sig]))
}
}
}
// sigignore ignores the signal sig.
// It is only called while holding the os/signal.handlers lock,
// via os/signal.ignoreSignal and signal_ignore.
func sigignore(sig uint32) {
if sig >= uint32(len(sigtable)) {
return
}
// SIGPROF is handled specially for profiling.
if sig == _SIGPROF {
return
}
t := &sigtable[sig]
if t.flags&_SigNotify != 0 {
atomic.Store(&handlingSig[sig], 0)
setsig(sig, _SIG_IGN)
}
}
// clearSignalHandlers clears all signal handlers that are not ignored
// back to the default. This is called by the child after a fork, so that
// we can enable the signal mask for the exec without worrying about
// running a signal handler in the child.
//go:nosplit
//go:nowritebarrierrec
func clearSignalHandlers() {
for i := uint32(0); i < _NSIG; i++ {
if atomic.Load(&handlingSig[i]) != 0 {
setsig(i, _SIG_DFL)
}
}
}
// setProcessCPUProfiler is called when the profiling timer changes.
// It is called with prof.lock held. hz is the new timer, and is 0 if
// profiling is being disabled. Enable or disable the signal as
// required for -buildmode=c-archive.
func setProcessCPUProfiler(hz int32) {
if hz != 0 {
// Enable the Go signal handler if not enabled.
if atomic.Cas(&handlingSig[_SIGPROF], 0, 1) {
atomic.Storeuintptr(&fwdSig[_SIGPROF], getsig(_SIGPROF))
setsig(_SIGPROF, funcPC(sighandler))
}
var it itimerval
it.it_interval.tv_sec = 0
it.it_interval.set_usec(1000000 / hz)
it.it_value = it.it_interval
setitimer(_ITIMER_PROF, &it, nil)
} else {
// If the Go signal handler should be disabled by default,
// switch back to the signal handler that was installed
// when we enabled profiling. We don't try to handle the case
// of a program that changes the SIGPROF handler while Go
// profiling is enabled.
//
// If no signal handler was installed before, then start
// ignoring SIGPROF signals. We do this, rather than change
// to SIG_DFL, because there may be a pending SIGPROF
// signal that has not yet been delivered to some other thread.
// If we change to SIG_DFL here, the program will crash
// when that SIGPROF is delivered. We assume that programs
// that use profiling don't want to crash on a stray SIGPROF.
// See issue 19320.
if !sigInstallGoHandler(_SIGPROF) {
if atomic.Cas(&handlingSig[_SIGPROF], 1, 0) {
h := atomic.Loaduintptr(&fwdSig[_SIGPROF])
if h == _SIG_DFL {
h = _SIG_IGN
}
setsig(_SIGPROF, h)
}
}
setitimer(_ITIMER_PROF, &itimerval{}, nil)
}
}
// setThreadCPUProfiler makes any thread-specific changes required to
// implement profiling at a rate of hz.
// No changes required on Unix systems.
func setThreadCPUProfiler(hz int32) {
getg().m.profilehz = hz
}
func sigpipe() {
if signal_ignored(_SIGPIPE) || sigsend(_SIGPIPE) {
return
}
dieFromSignal(_SIGPIPE)
}
// doSigPreempt handles a preemption signal on gp.
func doSigPreempt(gp *g, ctxt *sigctxt) {
// Check if this G wants to be preempted and is safe to
// preempt.
if wantAsyncPreempt(gp) {
if ok, newpc := isAsyncSafePoint(gp, ctxt.sigpc(), ctxt.sigsp(), ctxt.siglr()); ok {
// Adjust the PC and inject a call to asyncPreempt.
ctxt.pushCall(funcPC(asyncPreempt), newpc)
}
}
// Acknowledge the preemption.
atomic.Xadd(&gp.m.preemptGen, 1)
atomic.Store(&gp.m.signalPending, 0)
if GOOS == "darwin" || GOOS == "ios" {
atomic.Xadd(&pendingPreemptSignals, -1)
}
}
const preemptMSupported = true
// preemptM sends a preemption request to mp. This request may be
// handled asynchronously and may be coalesced with other requests to
// the M. When the request is received, if the running G or P are
// marked for preemption and the goroutine is at an asynchronous
// safe-point, it will preempt the goroutine. It always atomically
// increments mp.preemptGen after handling a preemption request.
func preemptM(mp *m) {
// On Darwin, don't try to preempt threads during exec.
// Issue #41702.
if GOOS == "darwin" || GOOS == "ios" {
execLock.rlock()
}
if atomic.Cas(&mp.signalPending, 0, 1) {
if GOOS == "darwin" || GOOS == "ios" {
atomic.Xadd(&pendingPreemptSignals, 1)
}
// If multiple threads are preempting the same M, it may send many
// signals to the same M such that it hardly make progress, causing
// live-lock problem. Apparently this could happen on darwin. See
// issue #37741.
// Only send a signal if there isn't already one pending.
signalM(mp, sigPreempt)
}
if GOOS == "darwin" || GOOS == "ios" {
execLock.runlock()
}
}
// sigFetchG fetches the value of G safely when running in a signal handler.
// On some architectures, the g value may be clobbered when running in a VDSO.
// See issue #32912.
//
//go:nosplit
func sigFetchG(c *sigctxt) *g {
switch GOARCH {
case "arm", "arm64":
if !iscgo && inVDSOPage(c.sigpc()) {
// When using cgo, we save the g on TLS and load it from there
// in sigtramp. Just use that.
// Otherwise, before making a VDSO call we save the g to the
// bottom of the signal stack. Fetch from there.
// TODO: in efence mode, stack is sysAlloc'd, so this wouldn't
// work.
sp := getcallersp()
s := spanOf(sp)
if s != nil && s.state.get() == mSpanManual && s.base() < sp && sp < s.limit {
gp := *(**g)(unsafe.Pointer(s.base()))
return gp
}
return nil
}
}
return getg()
}
// sigtrampgo is called from the signal handler function, sigtramp,
// written in assembly code.
// This is called by the signal handler, and the world may be stopped.
//
// It must be nosplit because getg() is still the G that was running
// (if any) when the signal was delivered, but it's (usually) called
// on the gsignal stack. Until this switches the G to gsignal, the
// stack bounds check won't work.
//
//go:nosplit
//go:nowritebarrierrec
func sigtrampgo(sig uint32, info *siginfo, ctx unsafe.Pointer) {
if sigfwdgo(sig, info, ctx) {
return
}
c := &sigctxt{info, ctx}
g := sigFetchG(c)
setg(g)
if g == nil {
if sig == _SIGPROF {
sigprofNonGoPC(c.sigpc())
return
}
if sig == sigPreempt && preemptMSupported && debug.asyncpreemptoff == 0 {
// This is probably a signal from preemptM sent
// while executing Go code but received while
// executing non-Go code.
// We got past sigfwdgo, so we know that there is
// no non-Go signal handler for sigPreempt.
// The default behavior for sigPreempt is to ignore
// the signal, so badsignal will be a no-op anyway.
if GOOS == "darwin" || GOOS == "ios" {
atomic.Xadd(&pendingPreemptSignals, -1)
}
return
}
c.fixsigcode(sig)
badsignal(uintptr(sig), c)
return
}
setg(g.m.gsignal)
// If some non-Go code called sigaltstack, adjust.
var gsignalStack gsignalStack
setStack := adjustSignalStack(sig, g.m, &gsignalStack)
if setStack {
g.m.gsignal.stktopsp = getcallersp()
}
if g.stackguard0 == stackFork {
signalDuringFork(sig)
}
c.fixsigcode(sig)
sighandler(sig, info, ctx, g)
setg(g)
if setStack {
restoreGsignalStack(&gsignalStack)
}
}
// adjustSignalStack adjusts the current stack guard based on the
// stack pointer that is actually in use while handling a signal.
// We do this in case some non-Go code called sigaltstack.
// This reports whether the stack was adjusted, and if so stores the old
// signal stack in *gsigstack.
//go:nosplit
func adjustSignalStack(sig uint32, mp *m, gsigStack *gsignalStack) bool {
sp := uintptr(unsafe.Pointer(&sig))
if sp >= mp.gsignal.stack.lo && sp < mp.gsignal.stack.hi {
return false
}
if sp >= mp.g0.stack.lo && sp < mp.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: mp.g0.stack.hi - mp.g0.stack.lo}
setSignalstackSP(&st, mp.g0.stack.lo)
setGsignalStack(&st, gsigStack)
return true
}
var st stackt
sigaltstack(nil, &st)
if st.ss_flags&_SS_DISABLE != 0 {
setg(nil)
needm()
noSignalStack(sig)
dropm()
}
stsp := uintptr(unsafe.Pointer(st.ss_sp))
if sp < stsp || sp >= stsp+st.ss_size {
setg(nil)
needm()
sigNotOnStack(sig)
dropm()
}
setGsignalStack(&st, gsigStack)
return true
}
// crashing is the number of m's we have waited for when implementing
// GOTRACEBACK=crash when a signal is received.
var crashing int32
// testSigtrap and testSigusr1 are used by the runtime tests. If
// non-nil, it is called on SIGTRAP/SIGUSR1. If it returns true, the
// normal behavior on this signal is suppressed.
var testSigtrap func(info *siginfo, ctxt *sigctxt, gp *g) bool
var testSigusr1 func(gp *g) bool
// sighandler is invoked when a signal occurs. The global g will be
// set to a gsignal goroutine and we will be running on the alternate
// signal stack. The parameter g will be the value of the global g
// when the signal occurred. The sig, info, and ctxt parameters are
// from the system signal handler: they are the parameters passed when
// the SA is passed to the sigaction system call.
//
// The garbage collector may have stopped the world, so write barriers
// are not allowed.
//
//go:nowritebarrierrec
func sighandler(sig uint32, info *siginfo, ctxt unsafe.Pointer, gp *g) {
_g_ := getg()
c := &sigctxt{info, ctxt}
if sig == _SIGPROF {
sigprof(c.sigpc(), c.sigsp(), c.siglr(), gp, _g_.m)
return
}
if sig == _SIGTRAP && testSigtrap != nil && testSigtrap(info, (*sigctxt)(noescape(unsafe.Pointer(c))), gp) {
return
}
if sig == _SIGUSR1 && testSigusr1 != nil && testSigusr1(gp) {
return
}
if sig == sigPreempt && debug.asyncpreemptoff == 0 {
// Might be a preemption signal.
doSigPreempt(gp, c)
// Even if this was definitely a preemption signal, it
// may have been coalesced with another signal, so we
// still let it through to the application.
}
flags := int32(_SigThrow)
if sig < uint32(len(sigtable)) {
flags = sigtable[sig].flags
}
if c.sigcode() != _SI_USER && flags&_SigPanic != 0 && gp.throwsplit {
// We can't safely sigpanic because it may grow the
// stack. Abort in the signal handler instead.
flags = _SigThrow
}
if isAbortPC(c.sigpc()) {
// On many architectures, the abort function just
// causes a memory fault. Don't turn that into a panic.
flags = _SigThrow
}
if c.sigcode() != _SI_USER && flags&_SigPanic != 0 {
// The signal is going to cause a panic.
// Arrange the stack so that it looks like the point
// where the signal occurred made a call to the
// function sigpanic. Then set the PC to sigpanic.
// Have to pass arguments out of band since
// augmenting the stack frame would break
// the unwinding code.
gp.sig = sig
gp.sigcode0 = uintptr(c.sigcode())
gp.sigcode1 = uintptr(c.fault())
gp.sigpc = c.sigpc()
c.preparePanic(sig, gp)
return
}
if c.sigcode() == _SI_USER || flags&_SigNotify != 0 {
if sigsend(sig) {
return
}
}
if c.sigcode() == _SI_USER && signal_ignored(sig) {
return
}
if flags&_SigKill != 0 {
dieFromSignal(sig)
}
// _SigThrow means that we should exit now.
// If we get here with _SigPanic, it means that the signal
// was sent to us by a program (c.sigcode() == _SI_USER);
// in that case, if we didn't handle it in sigsend, we exit now.
if flags&(_SigThrow|_SigPanic) == 0 {
return
}
_g_.m.throwing = 1
_g_.m.caughtsig.set(gp)
if crashing == 0 {
startpanic_m()
}
if sig < uint32(len(sigtable)) {
print(sigtable[sig].name, "\n")
} else {
print("Signal ", sig, "\n")
}
print("PC=", hex(c.sigpc()), " m=", _g_.m.id, " sigcode=", c.sigcode(), "\n")
if _g_.m.lockedg != 0 && _g_.m.ncgo > 0 && gp == _g_.m.g0 {
print("signal arrived during cgo execution\n")
gp = _g_.m.lockedg.ptr()
}
if sig == _SIGILL || sig == _SIGFPE {
// It would be nice to know how long the instruction is.
// Unfortunately, that's complicated to do in general (mostly for x86
// and s930x, but other archs have non-standard instruction lengths also).
// Opt to print 16 bytes, which covers most instructions.
const maxN = 16
n := uintptr(maxN)
// We have to be careful, though. If we're near the end of
// a page and the following page isn't mapped, we could
// segfault. So make sure we don't straddle a page (even though
// that could lead to printing an incomplete instruction).
// We're assuming here we can read at least the page containing the PC.
// I suppose it is possible that the page is mapped executable but not readable?
pc := c.sigpc()
if n > physPageSize-pc%physPageSize {
n = physPageSize - pc%physPageSize
}
print("instruction bytes:")
b := (*[maxN]byte)(unsafe.Pointer(pc))
for i := uintptr(0); i < n; i++ {
print(" ", hex(b[i]))
}
println()
}
print("\n")
level, _, docrash := gotraceback()
if level > 0 {
goroutineheader(gp)
tracebacktrap(c.sigpc(), c.sigsp(), c.siglr(), gp)
if crashing > 0 && gp != _g_.m.curg && _g_.m.curg != nil && readgstatus(_g_.m.curg)&^_Gscan == _Grunning {
// tracebackothers on original m skipped this one; trace it now.
goroutineheader(_g_.m.curg)
traceback(^uintptr(0), ^uintptr(0), 0, _g_.m.curg)
} else if crashing == 0 {
tracebackothers(gp)
print("\n")
}
dumpregs(c)
}
if docrash {
crashing++
if crashing < mcount()-int32(extraMCount) {
// There are other m's that need to dump their stacks.
// Relay SIGQUIT to the next m by sending it to the current process.
// All m's that have already received SIGQUIT have signal masks blocking
// receipt of any signals, so the SIGQUIT will go to an m that hasn't seen it yet.
// When the last m receives the SIGQUIT, it will fall through to the call to
// crash below. Just in case the relaying gets botched, each m involved in
// the relay sleeps for 5 seconds and then does the crash/exit itself.
// In expected operation, the last m has received the SIGQUIT and run
// crash/exit and the process is gone, all long before any of the
// 5-second sleeps have finished.
print("\n-----\n\n")
raiseproc(_SIGQUIT)
usleep(5 * 1000 * 1000)
}
crash()
}
printDebugLog()
exit(2)
}
// sigpanic turns a synchronous signal into a run-time panic.
// If the signal handler sees a synchronous panic, it arranges the
// stack to look like the function where the signal occurred called
// sigpanic, sets the signal's PC value to sigpanic, and returns from
// the signal handler. The effect is that the program will act as
// though the function that got the signal simply called sigpanic
// instead.
//
// This must NOT be nosplit because the linker doesn't know where
// sigpanic calls can be injected.
//
// The signal handler must not inject a call to sigpanic if
// getg().throwsplit, since sigpanic may need to grow the stack.
//
// This is exported via linkname to assembly in runtime/cgo.
//go:linkname sigpanic
func sigpanic() {
g := getg()
if !canpanic(g) {
throw("unexpected signal during runtime execution")
}
switch g.sig {
case _SIGBUS:
if g.sigcode0 == _BUS_ADRERR && g.sigcode1 < 0x1000 {
panicmem()
}
// Support runtime/debug.SetPanicOnFault.
if g.paniconfault {
panicmemAddr(g.sigcode1)
}
print("unexpected fault address ", hex(g.sigcode1), "\n")
throw("fault")
case _SIGSEGV:
if (g.sigcode0 == 0 || g.sigcode0 == _SEGV_MAPERR || g.sigcode0 == _SEGV_ACCERR) && g.sigcode1 < 0x1000 {
panicmem()
}
// Support runtime/debug.SetPanicOnFault.
if g.paniconfault {
panicmemAddr(g.sigcode1)
}
print("unexpected fault address ", hex(g.sigcode1), "\n")
throw("fault")
case _SIGFPE:
switch g.sigcode0 {
case _FPE_INTDIV:
panicdivide()
case _FPE_INTOVF:
panicoverflow()
}
panicfloat()
}
if g.sig >= uint32(len(sigtable)) {
// can't happen: we looked up g.sig in sigtable to decide to call sigpanic
throw("unexpected signal value")
}
panic(errorString(sigtable[g.sig].name))
}
// dieFromSignal kills the program with a signal.
// This provides the expected exit status for the shell.
// This is only called with fatal signals expected to kill the process.
//go:nosplit
//go:nowritebarrierrec
func dieFromSignal(sig uint32) {
unblocksig(sig)
// Mark the signal as unhandled to ensure it is forwarded.
atomic.Store(&handlingSig[sig], 0)
raise(sig)
// That should have killed us. On some systems, though, raise
// sends the signal to the whole process rather than to just
// the current thread, which means that the signal may not yet
// have been delivered. Give other threads a chance to run and
// pick up the signal.
osyield()
osyield()
osyield()
// If that didn't work, try _SIG_DFL.
setsig(sig, _SIG_DFL)
raise(sig)
osyield()
osyield()
osyield()
// If we are still somehow running, just exit with the wrong status.
exit(2)
}
// raisebadsignal is called when a signal is received on a non-Go
// thread, and the Go program does not want to handle it (that is, the
// program has not called os/signal.Notify for the signal).
func raisebadsignal(sig uint32, c *sigctxt) {
if sig == _SIGPROF {
// Ignore profiling signals that arrive on non-Go threads.
return
}
var handler uintptr
if sig >= _NSIG {
handler = _SIG_DFL
} else {
handler = atomic.Loaduintptr(&fwdSig[sig])
}
// Reset the signal handler and raise the signal.
// We are currently running inside a signal handler, so the
// signal is blocked. We need to unblock it before raising the
// signal, or the signal we raise will be ignored until we return
// from the signal handler. We know that the signal was unblocked
// before entering the handler, or else we would not have received
// it. That means that we don't have to worry about blocking it
// again.
unblocksig(sig)
setsig(sig, handler)
// If we're linked into a non-Go program we want to try to
// avoid modifying the original context in which the signal
// was raised. If the handler is the default, we know it
// is non-recoverable, so we don't have to worry about
// re-installing sighandler. At this point we can just
// return and the signal will be re-raised and caught by
// the default handler with the correct context.
//
// On FreeBSD, the libthr sigaction code prevents
// this from working so we fall through to raise.
if GOOS != "freebsd" && (isarchive || islibrary) && handler == _SIG_DFL && c.sigcode() != _SI_USER {
return
}
raise(sig)
// Give the signal a chance to be delivered.
// In almost all real cases the program is about to crash,
// so sleeping here is not a waste of time.
usleep(1000)
// If the signal didn't cause the program to exit, restore the
// Go signal handler and carry on.
//
// We may receive another instance of the signal before we
// restore the Go handler, but that is not so bad: we know
// that the Go program has been ignoring the signal.
setsig(sig, funcPC(sighandler))
}
//go:nosplit
func crash() {
// OS X core dumps are linear dumps of the mapped memory,
// from the first virtual byte to the last, with zeros in the gaps.
// Because of the way we arrange the address space on 64-bit systems,
// this means the OS X core file will be >128 GB and even on a zippy
// workstation can take OS X well over an hour to write (uninterruptible).
// Save users from making that mistake.
if GOOS == "darwin" && GOARCH == "amd64" {
return
}
dieFromSignal(_SIGABRT)
}
// ensureSigM starts one global, sleeping thread to make sure at least one thread
// is available to catch signals enabled for os/signal.
func ensureSigM() {
if maskUpdatedChan != nil {
return
}
maskUpdatedChan = make(chan struct{})
disableSigChan = make(chan uint32)
enableSigChan = make(chan uint32)
go func() {
// Signal masks are per-thread, so make sure this goroutine stays on one
// thread.
LockOSThread()
defer UnlockOSThread()
// The sigBlocked mask contains the signals not active for os/signal,
// initially all signals except the essential. When signal.Notify()/Stop is called,
// sigenable/sigdisable in turn notify this thread to update its signal
// mask accordingly.
sigBlocked := sigset_all
for i := range sigtable {
if !blockableSig(uint32(i)) {
sigdelset(&sigBlocked, i)
}
}
sigprocmask(_SIG_SETMASK, &sigBlocked, nil)
for {
select {
case sig := <-enableSigChan:
if sig > 0 {
sigdelset(&sigBlocked, int(sig))
}
case sig := <-disableSigChan:
if sig > 0 && blockableSig(sig) {
sigaddset(&sigBlocked, int(sig))
}
}
sigprocmask(_SIG_SETMASK, &sigBlocked, nil)
maskUpdatedChan <- struct{}{}
}
}()
}
// This is called when we receive a signal when there is no signal stack.
// This can only happen if non-Go code calls sigaltstack to disable the
// signal stack.
func noSignalStack(sig uint32) {
println("signal", sig, "received on thread with no signal stack")
throw("non-Go code disabled sigaltstack")
}
// This is called if we receive a signal when there is a signal stack
// but we are not on it. This can only happen if non-Go code called
// sigaction without setting the SS_ONSTACK flag.
func sigNotOnStack(sig uint32) {
println("signal", sig, "received but handler not on signal stack")
throw("non-Go code set up signal handler without SA_ONSTACK flag")
}
// signalDuringFork is called if we receive a signal while doing a fork.
// We do not want signals at that time, as a signal sent to the process
// group may be delivered to the child process, causing confusion.
// This should never be called, because we block signals across the fork;
// this function is just a safety check. See issue 18600 for background.
func signalDuringFork(sig uint32) {
println("signal", sig, "received during fork")
throw("signal received during fork")
}
var badginsignalMsg = "fatal: bad g in signal handler\n"
// This runs on a foreign stack, without an m or a g. No stack split.
//go:nosplit
//go:norace
//go:nowritebarrierrec
func badsignal(sig uintptr, c *sigctxt) {
if !iscgo && !cgoHasExtraM {
// There is no extra M. needm will not be able to grab
// an M. Instead of hanging, just crash.
// Cannot call split-stack function as there is no G.
s := stringStructOf(&badginsignalMsg)
write(2, s.str, int32(s.len))
exit(2)
*(*uintptr)(unsafe.Pointer(uintptr(123))) = 2
}
needm()
if !sigsend(uint32(sig)) {
// A foreign thread received the signal sig, and the
// Go code does not want to handle it.
raisebadsignal(uint32(sig), c)
}
dropm()
}
//go:noescape
func sigfwd(fn uintptr, sig uint32, info *siginfo, ctx unsafe.Pointer)
// Determines if the signal should be handled by Go and if not, forwards the
// signal to the handler that was installed before Go's. Returns whether the
// signal was forwarded.
// This is called by the signal handler, and the world may be stopped.
//go:nosplit
//go:nowritebarrierrec
func sigfwdgo(sig uint32, info *siginfo, ctx unsafe.Pointer) bool {
if sig >= uint32(len(sigtable)) {
return false
}
fwdFn := atomic.Loaduintptr(&fwdSig[sig])
flags := sigtable[sig].flags
// If we aren't handling the signal, forward it.
if atomic.Load(&handlingSig[sig]) == 0 || !signalsOK {
// If the signal is ignored, doing nothing is the same as forwarding.
if fwdFn == _SIG_IGN || (fwdFn == _SIG_DFL && flags&_SigIgn != 0) {
return true
}
// We are not handling the signal and there is no other handler to forward to.
// Crash with the default behavior.
if fwdFn == _SIG_DFL {
setsig(sig, _SIG_DFL)
dieFromSignal(sig)
return false
}
sigfwd(fwdFn, sig, info, ctx)
return true
}
// This function and its caller sigtrampgo assumes SIGPIPE is delivered on the
// originating thread. This property does not hold on macOS (golang.org/issue/33384),
// so we have no choice but to ignore SIGPIPE.
if (GOOS == "darwin" || GOOS == "ios") && sig == _SIGPIPE {
return true
}
// If there is no handler to forward to, no need to forward.
if fwdFn == _SIG_DFL {
return false
}
c := &sigctxt{info, ctx}
// Only forward synchronous signals and SIGPIPE.
// Unfortunately, user generated SIGPIPEs will also be forwarded, because si_code