1 // Copyright 2012 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 //go:build unix 6 7 package runtime 8 9 import ( 10 "internal/abi" 11 "runtime/internal/atomic" 12 "runtime/internal/sys" 13 "unsafe" 14 ) 15 16 // sigTabT is the type of an entry in the global sigtable array. 17 // sigtable is inherently system dependent, and appears in OS-specific files, 18 // but sigTabT is the same for all Unixy systems. 19 // The sigtable array is indexed by a system signal number to get the flags 20 // and printable name of each signal. 21 type sigTabT struct { 22 flags int32 23 name string 24 } 25 26 //go:linkname os_sigpipe os.sigpipe 27 func os_sigpipe() { 28 systemstack(sigpipe) 29 } 30 31 func signame(sig uint32) string { 32 if sig >= uint32(len(sigtable)) { 33 return "" 34 } 35 return sigtable[sig].name 36 } 37 38 const ( 39 _SIG_DFL uintptr = 0 40 _SIG_IGN uintptr = 1 41 ) 42 43 // sigPreempt is the signal used for non-cooperative preemption. 44 // 45 // There's no good way to choose this signal, but there are some 46 // heuristics: 47 // 48 // 1. It should be a signal that's passed-through by debuggers by 49 // default. On Linux, this is SIGALRM, SIGURG, SIGCHLD, SIGIO, 50 // SIGVTALRM, SIGPROF, and SIGWINCH, plus some glibc-internal signals. 51 // 52 // 2. It shouldn't be used internally by libc in mixed Go/C binaries 53 // because libc may assume it's the only thing that can handle these 54 // signals. For example SIGCANCEL or SIGSETXID. 55 // 56 // 3. It should be a signal that can happen spuriously without 57 // consequences. For example, SIGALRM is a bad choice because the 58 // signal handler can't tell if it was caused by the real process 59 // alarm or not (arguably this means the signal is broken, but I 60 // digress). SIGUSR1 and SIGUSR2 are also bad because those are often 61 // used in meaningful ways by applications. 62 // 63 // 4. We need to deal with platforms without real-time signals (like 64 // macOS), so those are out. 65 // 66 // We use SIGURG because it meets all of these criteria, is extremely 67 // unlikely to be used by an application for its "real" meaning (both 68 // because out-of-band data is basically unused and because SIGURG 69 // doesn't report which socket has the condition, making it pretty 70 // useless), and even if it is, the application has to be ready for 71 // spurious SIGURG. SIGIO wouldn't be a bad choice either, but is more 72 // likely to be used for real. 73 const sigPreempt = _SIGURG 74 75 // Stores the signal handlers registered before Go installed its own. 76 // These signal handlers will be invoked in cases where Go doesn't want to 77 // handle a particular signal (e.g., signal occurred on a non-Go thread). 78 // See sigfwdgo for more information on when the signals are forwarded. 79 // 80 // This is read by the signal handler; accesses should use 81 // atomic.Loaduintptr and atomic.Storeuintptr. 82 var fwdSig [_NSIG]uintptr 83 84 // handlingSig is indexed by signal number and is non-zero if we are 85 // currently handling the signal. Or, to put it another way, whether 86 // the signal handler is currently set to the Go signal handler or not. 87 // This is uint32 rather than bool so that we can use atomic instructions. 88 var handlingSig [_NSIG]uint32 89 90 // channels for synchronizing signal mask updates with the signal mask 91 // thread 92 var ( 93 disableSigChan chan uint32 94 enableSigChan chan uint32 95 maskUpdatedChan chan struct{} 96 ) 97 98 func init() { 99 // _NSIG is the number of signals on this operating system. 100 // sigtable should describe what to do for all the possible signals. 101 if len(sigtable) != _NSIG { 102 print("runtime: len(sigtable)=", len(sigtable), " _NSIG=", _NSIG, "\n") 103 throw("bad sigtable len") 104 } 105 } 106 107 var signalsOK bool 108 109 // Initialize signals. 110 // Called by libpreinit so runtime may not be initialized. 111 // 112 //go:nosplit 113 //go:nowritebarrierrec 114 func initsig(preinit bool) { 115 if !preinit { 116 // It's now OK for signal handlers to run. 117 signalsOK = true 118 } 119 120 // For c-archive/c-shared this is called by libpreinit with 121 // preinit == true. 122 if (isarchive || islibrary) && !preinit { 123 return 124 } 125 126 for i := uint32(0); i < _NSIG; i++ { 127 t := &sigtable[i] 128 if t.flags == 0 || t.flags&_SigDefault != 0 { 129 continue 130 } 131 132 // We don't need to use atomic operations here because 133 // there shouldn't be any other goroutines running yet. 134 fwdSig[i] = getsig(i) 135 136 if !sigInstallGoHandler(i) { 137 // Even if we are not installing a signal handler, 138 // set SA_ONSTACK if necessary. 139 if fwdSig[i] != _SIG_DFL && fwdSig[i] != _SIG_IGN { 140 setsigstack(i) 141 } else if fwdSig[i] == _SIG_IGN { 142 sigInitIgnored(i) 143 } 144 continue 145 } 146 147 handlingSig[i] = 1 148 setsig(i, abi.FuncPCABIInternal(sighandler)) 149 } 150 } 151 152 //go:nosplit 153 //go:nowritebarrierrec 154 func sigInstallGoHandler(sig uint32) bool { 155 // For some signals, we respect an inherited SIG_IGN handler 156 // rather than insist on installing our own default handler. 157 // Even these signals can be fetched using the os/signal package. 158 switch sig { 159 case _SIGHUP, _SIGINT: 160 if atomic.Loaduintptr(&fwdSig[sig]) == _SIG_IGN { 161 return false 162 } 163 } 164 165 if (GOOS == "linux" || GOOS == "android") && !iscgo && sig == sigPerThreadSyscall { 166 // sigPerThreadSyscall is the same signal used by glibc for 167 // per-thread syscalls on Linux. We use it for the same purpose 168 // in non-cgo binaries. 169 return true 170 } 171 172 t := &sigtable[sig] 173 if t.flags&_SigSetStack != 0 { 174 return false 175 } 176 177 // When built using c-archive or c-shared, only install signal 178 // handlers for synchronous signals and SIGPIPE and sigPreempt. 179 if (isarchive || islibrary) && t.flags&_SigPanic == 0 && sig != _SIGPIPE && sig != sigPreempt { 180 return false 181 } 182 183 return true 184 } 185 186 // sigenable enables the Go signal handler to catch the signal sig. 187 // It is only called while holding the os/signal.handlers lock, 188 // via os/signal.enableSignal and signal_enable. 189 func sigenable(sig uint32) { 190 if sig >= uint32(len(sigtable)) { 191 return 192 } 193 194 // SIGPROF is handled specially for profiling. 195 if sig == _SIGPROF { 196 return 197 } 198 199 t := &sigtable[sig] 200 if t.flags&_SigNotify != 0 { 201 ensureSigM() 202 enableSigChan <- sig 203 <-maskUpdatedChan 204 if atomic.Cas(&handlingSig[sig], 0, 1) { 205 atomic.Storeuintptr(&fwdSig[sig], getsig(sig)) 206 setsig(sig, abi.FuncPCABIInternal(sighandler)) 207 } 208 } 209 } 210 211 // sigdisable disables the Go signal handler for the signal sig. 212 // It is only called while holding the os/signal.handlers lock, 213 // via os/signal.disableSignal and signal_disable. 214 func sigdisable(sig uint32) { 215 if sig >= uint32(len(sigtable)) { 216 return 217 } 218 219 // SIGPROF is handled specially for profiling. 220 if sig == _SIGPROF { 221 return 222 } 223 224 t := &sigtable[sig] 225 if t.flags&_SigNotify != 0 { 226 ensureSigM() 227 disableSigChan <- sig 228 <-maskUpdatedChan 229 230 // If initsig does not install a signal handler for a 231 // signal, then to go back to the state before Notify 232 // we should remove the one we installed. 233 if !sigInstallGoHandler(sig) { 234 atomic.Store(&handlingSig[sig], 0) 235 setsig(sig, atomic.Loaduintptr(&fwdSig[sig])) 236 } 237 } 238 } 239 240 // sigignore ignores the signal sig. 241 // It is only called while holding the os/signal.handlers lock, 242 // via os/signal.ignoreSignal and signal_ignore. 243 func sigignore(sig uint32) { 244 if sig >= uint32(len(sigtable)) { 245 return 246 } 247 248 // SIGPROF is handled specially for profiling. 249 if sig == _SIGPROF { 250 return 251 } 252 253 t := &sigtable[sig] 254 if t.flags&_SigNotify != 0 { 255 atomic.Store(&handlingSig[sig], 0) 256 setsig(sig, _SIG_IGN) 257 } 258 } 259 260 // clearSignalHandlers clears all signal handlers that are not ignored 261 // back to the default. This is called by the child after a fork, so that 262 // we can enable the signal mask for the exec without worrying about 263 // running a signal handler in the child. 264 // 265 //go:nosplit 266 //go:nowritebarrierrec 267 func clearSignalHandlers() { 268 for i := uint32(0); i < _NSIG; i++ { 269 if atomic.Load(&handlingSig[i]) != 0 { 270 setsig(i, _SIG_DFL) 271 } 272 } 273 } 274 275 // setProcessCPUProfilerTimer is called when the profiling timer changes. 276 // It is called with prof.signalLock held. hz is the new timer, and is 0 if 277 // profiling is being disabled. Enable or disable the signal as 278 // required for -buildmode=c-archive. 279 func setProcessCPUProfilerTimer(hz int32) { 280 if hz != 0 { 281 // Enable the Go signal handler if not enabled. 282 if atomic.Cas(&handlingSig[_SIGPROF], 0, 1) { 283 h := getsig(_SIGPROF) 284 // If no signal handler was installed before, then we record 285 // _SIG_IGN here. When we turn off profiling (below) we'll start 286 // ignoring SIGPROF signals. We do this, rather than change 287 // to SIG_DFL, because there may be a pending SIGPROF 288 // signal that has not yet been delivered to some other thread. 289 // If we change to SIG_DFL when turning off profiling, the 290 // program will crash when that SIGPROF is delivered. We assume 291 // that programs that use profiling don't want to crash on a 292 // stray SIGPROF. See issue 19320. 293 // We do the change here instead of when turning off profiling, 294 // because there we may race with a signal handler running 295 // concurrently, in particular, sigfwdgo may observe _SIG_DFL and 296 // die. See issue 43828. 297 if h == _SIG_DFL { 298 h = _SIG_IGN 299 } 300 atomic.Storeuintptr(&fwdSig[_SIGPROF], h) 301 setsig(_SIGPROF, abi.FuncPCABIInternal(sighandler)) 302 } 303 304 var it itimerval 305 it.it_interval.tv_sec = 0 306 it.it_interval.set_usec(1000000 / hz) 307 it.it_value = it.it_interval 308 setitimer(_ITIMER_PROF, &it, nil) 309 } else { 310 setitimer(_ITIMER_PROF, &itimerval{}, nil) 311 312 // If the Go signal handler should be disabled by default, 313 // switch back to the signal handler that was installed 314 // when we enabled profiling. We don't try to handle the case 315 // of a program that changes the SIGPROF handler while Go 316 // profiling is enabled. 317 if !sigInstallGoHandler(_SIGPROF) { 318 if atomic.Cas(&handlingSig[_SIGPROF], 1, 0) { 319 h := atomic.Loaduintptr(&fwdSig[_SIGPROF]) 320 setsig(_SIGPROF, h) 321 } 322 } 323 } 324 } 325 326 // setThreadCPUProfilerHz makes any thread-specific changes required to 327 // implement profiling at a rate of hz. 328 // No changes required on Unix systems when using setitimer. 329 func setThreadCPUProfilerHz(hz int32) { 330 getg().m.profilehz = hz 331 } 332 333 func sigpipe() { 334 if signal_ignored(_SIGPIPE) || sigsend(_SIGPIPE) { 335 return 336 } 337 dieFromSignal(_SIGPIPE) 338 } 339 340 // doSigPreempt handles a preemption signal on gp. 341 func doSigPreempt(gp *g, ctxt *sigctxt) { 342 // Check if this G wants to be preempted and is safe to 343 // preempt. 344 if wantAsyncPreempt(gp) { 345 if ok, newpc := isAsyncSafePoint(gp, ctxt.sigpc(), ctxt.sigsp(), ctxt.siglr()); ok { 346 // Adjust the PC and inject a call to asyncPreempt. 347 ctxt.pushCall(abi.FuncPCABI0(asyncPreempt), newpc) 348 } 349 } 350 351 // Acknowledge the preemption. 352 atomic.Xadd(&gp.m.preemptGen, 1) 353 atomic.Store(&gp.m.signalPending, 0) 354 355 if GOOS == "darwin" || GOOS == "ios" { 356 atomic.Xadd(&pendingPreemptSignals, -1) 357 } 358 } 359 360 const preemptMSupported = true 361 362 // preemptM sends a preemption request to mp. This request may be 363 // handled asynchronously and may be coalesced with other requests to 364 // the M. When the request is received, if the running G or P are 365 // marked for preemption and the goroutine is at an asynchronous 366 // safe-point, it will preempt the goroutine. It always atomically 367 // increments mp.preemptGen after handling a preemption request. 368 func preemptM(mp *m) { 369 // On Darwin, don't try to preempt threads during exec. 370 // Issue #41702. 371 if GOOS == "darwin" || GOOS == "ios" { 372 execLock.rlock() 373 } 374 375 if atomic.Cas(&mp.signalPending, 0, 1) { 376 if GOOS == "darwin" || GOOS == "ios" { 377 atomic.Xadd(&pendingPreemptSignals, 1) 378 } 379 380 // If multiple threads are preempting the same M, it may send many 381 // signals to the same M such that it hardly make progress, causing 382 // live-lock problem. Apparently this could happen on darwin. See 383 // issue #37741. 384 // Only send a signal if there isn't already one pending. 385 signalM(mp, sigPreempt) 386 } 387 388 if GOOS == "darwin" || GOOS == "ios" { 389 execLock.runlock() 390 } 391 } 392 393 // sigFetchG fetches the value of G safely when running in a signal handler. 394 // On some architectures, the g value may be clobbered when running in a VDSO. 395 // See issue #32912. 396 // 397 //go:nosplit 398 func sigFetchG(c *sigctxt) *g { 399 switch GOARCH { 400 case "arm", "arm64", "ppc64", "ppc64le", "riscv64", "s390x": 401 if !iscgo && inVDSOPage(c.sigpc()) { 402 // When using cgo, we save the g on TLS and load it from there 403 // in sigtramp. Just use that. 404 // Otherwise, before making a VDSO call we save the g to the 405 // bottom of the signal stack. Fetch from there. 406 // TODO: in efence mode, stack is sysAlloc'd, so this wouldn't 407 // work. 408 sp := getcallersp() 409 s := spanOf(sp) 410 if s != nil && s.state.get() == mSpanManual && s.base() < sp && sp < s.limit { 411 gp := *(**g)(unsafe.Pointer(s.base())) 412 return gp 413 } 414 return nil 415 } 416 } 417 return getg() 418 } 419 420 // sigtrampgo is called from the signal handler function, sigtramp, 421 // written in assembly code. 422 // This is called by the signal handler, and the world may be stopped. 423 // 424 // It must be nosplit because getg() is still the G that was running 425 // (if any) when the signal was delivered, but it's (usually) called 426 // on the gsignal stack. Until this switches the G to gsignal, the 427 // stack bounds check won't work. 428 // 429 //go:nosplit 430 //go:nowritebarrierrec 431 func sigtrampgo(sig uint32, info *siginfo, ctx unsafe.Pointer) { 432 if sigfwdgo(sig, info, ctx) { 433 return 434 } 435 c := &sigctxt{info, ctx} 436 g := sigFetchG(c) 437 setg(g) 438 if g == nil { 439 if sig == _SIGPROF { 440 // Some platforms (Linux) have per-thread timers, which we use in 441 // combination with the process-wide timer. Avoid double-counting. 442 if validSIGPROF(nil, c) { 443 sigprofNonGoPC(c.sigpc()) 444 } 445 return 446 } 447 if sig == sigPreempt && preemptMSupported && debug.asyncpreemptoff == 0 { 448 // This is probably a signal from preemptM sent 449 // while executing Go code but received while 450 // executing non-Go code. 451 // We got past sigfwdgo, so we know that there is 452 // no non-Go signal handler for sigPreempt. 453 // The default behavior for sigPreempt is to ignore 454 // the signal, so badsignal will be a no-op anyway. 455 if GOOS == "darwin" || GOOS == "ios" { 456 atomic.Xadd(&pendingPreemptSignals, -1) 457 } 458 return 459 } 460 c.fixsigcode(sig) 461 badsignal(uintptr(sig), c) 462 return 463 } 464 465 setg(g.m.gsignal) 466 467 // If some non-Go code called sigaltstack, adjust. 468 var gsignalStack gsignalStack 469 setStack := adjustSignalStack(sig, g.m, &gsignalStack) 470 if setStack { 471 g.m.gsignal.stktopsp = getcallersp() 472 } 473 474 if g.stackguard0 == stackFork { 475 signalDuringFork(sig) 476 } 477 478 c.fixsigcode(sig) 479 sighandler(sig, info, ctx, g) 480 setg(g) 481 if setStack { 482 restoreGsignalStack(&gsignalStack) 483 } 484 } 485 486 // If the signal handler receives a SIGPROF signal on a non-Go thread, 487 // it tries to collect a traceback into sigprofCallers. 488 // sigprofCallersUse is set to non-zero while sigprofCallers holds a traceback. 489 var sigprofCallers cgoCallers 490 var sigprofCallersUse uint32 491 492 // sigprofNonGo is called if we receive a SIGPROF signal on a non-Go thread, 493 // and the signal handler collected a stack trace in sigprofCallers. 494 // When this is called, sigprofCallersUse will be non-zero. 495 // g is nil, and what we can do is very limited. 496 // 497 // It is called from the signal handling functions written in assembly code that 498 // are active for cgo programs, cgoSigtramp and sigprofNonGoWrapper, which have 499 // not verified that the SIGPROF delivery corresponds to the best available 500 // profiling source for this thread. 501 // 502 //go:nosplit 503 //go:nowritebarrierrec 504 func sigprofNonGo(sig uint32, info *siginfo, ctx unsafe.Pointer) { 505 if prof.hz != 0 { 506 c := &sigctxt{info, ctx} 507 // Some platforms (Linux) have per-thread timers, which we use in 508 // combination with the process-wide timer. Avoid double-counting. 509 if validSIGPROF(nil, c) { 510 n := 0 511 for n < len(sigprofCallers) && sigprofCallers[n] != 0 { 512 n++ 513 } 514 cpuprof.addNonGo(sigprofCallers[:n]) 515 } 516 } 517 518 atomic.Store(&sigprofCallersUse, 0) 519 } 520 521 // sigprofNonGoPC is called when a profiling signal arrived on a 522 // non-Go thread and we have a single PC value, not a stack trace. 523 // g is nil, and what we can do is very limited. 524 // 525 //go:nosplit 526 //go:nowritebarrierrec 527 func sigprofNonGoPC(pc uintptr) { 528 if prof.hz != 0 { 529 stk := []uintptr{ 530 pc, 531 abi.FuncPCABIInternal(_ExternalCode) + sys.PCQuantum, 532 } 533 cpuprof.addNonGo(stk) 534 } 535 } 536 537 // adjustSignalStack adjusts the current stack guard based on the 538 // stack pointer that is actually in use while handling a signal. 539 // We do this in case some non-Go code called sigaltstack. 540 // This reports whether the stack was adjusted, and if so stores the old 541 // signal stack in *gsigstack. 542 // 543 //go:nosplit 544 func adjustSignalStack(sig uint32, mp *m, gsigStack *gsignalStack) bool { 545 sp := uintptr(unsafe.Pointer(&sig)) 546 if sp >= mp.gsignal.stack.lo && sp < mp.gsignal.stack.hi { 547 return false 548 } 549 550 var st stackt 551 sigaltstack(nil, &st) 552 stsp := uintptr(unsafe.Pointer(st.ss_sp)) 553 if st.ss_flags&_SS_DISABLE == 0 && sp >= stsp && sp < stsp+st.ss_size { 554 setGsignalStack(&st, gsigStack) 555 return true 556 } 557 558 if sp >= mp.g0.stack.lo && sp < mp.g0.stack.hi { 559 // The signal was delivered on the g0 stack. 560 // This can happen when linked with C code 561 // using the thread sanitizer, which collects 562 // signals then delivers them itself by calling 563 // the signal handler directly when C code, 564 // including C code called via cgo, calls a 565 // TSAN-intercepted function such as malloc. 566 // 567 // We check this condition last as g0.stack.lo 568 // may be not very accurate (see mstart). 569 st := stackt{ss_size: mp.g0.stack.hi - mp.g0.stack.lo} 570 setSignalstackSP(&st, mp.g0.stack.lo) 571 setGsignalStack(&st, gsigStack) 572 return true 573 } 574 575 // sp is not within gsignal stack, g0 stack, or sigaltstack. Bad. 576 setg(nil) 577 needm() 578 if st.ss_flags&_SS_DISABLE != 0 { 579 noSignalStack(sig) 580 } else { 581 sigNotOnStack(sig) 582 } 583 dropm() 584 return false 585 } 586 587 // crashing is the number of m's we have waited for when implementing 588 // GOTRACEBACK=crash when a signal is received. 589 var crashing int32 590 591 // testSigtrap and testSigusr1 are used by the runtime tests. If 592 // non-nil, it is called on SIGTRAP/SIGUSR1. If it returns true, the 593 // normal behavior on this signal is suppressed. 594 var testSigtrap func(info *siginfo, ctxt *sigctxt, gp *g) bool 595 var testSigusr1 func(gp *g) bool 596 597 // sighandler is invoked when a signal occurs. The global g will be 598 // set to a gsignal goroutine and we will be running on the alternate 599 // signal stack. The parameter g will be the value of the global g 600 // when the signal occurred. The sig, info, and ctxt parameters are 601 // from the system signal handler: they are the parameters passed when 602 // the SA is passed to the sigaction system call. 603 // 604 // The garbage collector may have stopped the world, so write barriers 605 // are not allowed. 606 // 607 //go:nowritebarrierrec 608 func sighandler(sig uint32, info *siginfo, ctxt unsafe.Pointer, gp *g) { 609 _g_ := getg() 610 c := &sigctxt{info, ctxt} 611 mp := _g_.m 612 613 // Cgo TSAN (not the Go race detector) intercepts signals and calls the 614 // signal handler at a later time. When the signal handler is called, the 615 // memory may have changed, but the signal context remains old. The 616 // unmatched signal context and memory makes it unsafe to unwind or inspect 617 // the stack. So we ignore delayed non-fatal signals that will cause a stack 618 // inspection (profiling signal and preemption signal). 619 // cgo_yield is only non-nil for TSAN, and is specifically used to trigger 620 // signal delivery. We use that as an indicator of delayed signals. 621 // For delayed signals, the handler is called on the g0 stack (see 622 // adjustSignalStack). 623 delayedSignal := *cgo_yield != nil && mp != nil && _g_.stack == mp.g0.stack 624 625 if sig == _SIGPROF { 626 // Some platforms (Linux) have per-thread timers, which we use in 627 // combination with the process-wide timer. Avoid double-counting. 628 if !delayedSignal && validSIGPROF(mp, c) { 629 sigprof(c.sigpc(), c.sigsp(), c.siglr(), gp, mp) 630 } 631 return 632 } 633 634 if sig == _SIGTRAP && testSigtrap != nil && testSigtrap(info, (*sigctxt)(noescape(unsafe.Pointer(c))), gp) { 635 return 636 } 637 638 if sig == _SIGUSR1 && testSigusr1 != nil && testSigusr1(gp) { 639 return 640 } 641 642 if (GOOS == "linux" || GOOS == "android") && sig == sigPerThreadSyscall { 643 // sigPerThreadSyscall is the same signal used by glibc for 644 // per-thread syscalls on Linux. We use it for the same purpose 645 // in non-cgo binaries. Since this signal is not _SigNotify, 646 // there is nothing more to do once we run the syscall. 647 runPerThreadSyscall() 648 return 649 } 650 651 if sig == sigPreempt && debug.asyncpreemptoff == 0 && !delayedSignal { 652 // Might be a preemption signal. 653 doSigPreempt(gp, c) 654 // Even if this was definitely a preemption signal, it 655 // may have been coalesced with another signal, so we 656 // still let it through to the application. 657 } 658 659 flags := int32(_SigThrow) 660 if sig < uint32(len(sigtable)) { 661 flags = sigtable[sig].flags 662 } 663 if c.sigcode() != _SI_USER && flags&_SigPanic != 0 && gp.throwsplit { 664 // We can't safely sigpanic because it may grow the 665 // stack. Abort in the signal handler instead. 666 flags = _SigThrow 667 } 668 if isAbortPC(c.sigpc()) { 669 // On many architectures, the abort function just 670 // causes a memory fault. Don't turn that into a panic. 671 flags = _SigThrow 672 } 673 if c.sigcode() != _SI_USER && flags&_SigPanic != 0 { 674 // The signal is going to cause a panic. 675 // Arrange the stack so that it looks like the point 676 // where the signal occurred made a call to the 677 // function sigpanic. Then set the PC to sigpanic. 678 679 // Have to pass arguments out of band since 680 // augmenting the stack frame would break 681 // the unwinding code. 682 gp.sig = sig 683 gp.sigcode0 = uintptr(c.sigcode()) 684 gp.sigcode1 = uintptr(c.fault()) 685 gp.sigpc = c.sigpc() 686 687 c.preparePanic(sig, gp) 688 return 689 } 690 691 if c.sigcode() == _SI_USER || flags&_SigNotify != 0 { 692 if sigsend(sig) { 693 return 694 } 695 } 696 697 if c.sigcode() == _SI_USER && signal_ignored(sig) { 698 return 699 } 700 701 if flags&_SigKill != 0 { 702 dieFromSignal(sig) 703 } 704 705 // _SigThrow means that we should exit now. 706 // If we get here with _SigPanic, it means that the signal 707 // was sent to us by a program (c.sigcode() == _SI_USER); 708 // in that case, if we didn't handle it in sigsend, we exit now. 709 if flags&(_SigThrow|_SigPanic) == 0 { 710 return 711 } 712 713 _g_.m.throwing = throwTypeRuntime 714 _g_.m.caughtsig.set(gp) 715 716 if crashing == 0 { 717 startpanic_m() 718 } 719 720 if sig < uint32(len(sigtable)) { 721 print(sigtable[sig].name, "\n") 722 } else { 723 print("Signal ", sig, "\n") 724 } 725 726 print("PC=", hex(c.sigpc()), " m=", _g_.m.id, " sigcode=", c.sigcode(), "\n") 727 if _g_.m.incgo && gp == _g_.m.g0 && _g_.m.curg != nil { 728 print("signal arrived during cgo execution\n") 729 // Switch to curg so that we get a traceback of the Go code 730 // leading up to the cgocall, which switched from curg to g0. 731 gp = _g_.m.curg 732 } 733 if sig == _SIGILL || sig == _SIGFPE { 734 // It would be nice to know how long the instruction is. 735 // Unfortunately, that's complicated to do in general (mostly for x86 736 // and s930x, but other archs have non-standard instruction lengths also). 737 // Opt to print 16 bytes, which covers most instructions. 738 const maxN = 16 739 n := uintptr(maxN) 740 // We have to be careful, though. If we're near the end of 741 // a page and the following page isn't mapped, we could 742 // segfault. So make sure we don't straddle a page (even though 743 // that could lead to printing an incomplete instruction). 744 // We're assuming here we can read at least the page containing the PC. 745 // I suppose it is possible that the page is mapped executable but not readable? 746 pc := c.sigpc() 747 if n > physPageSize-pc%physPageSize { 748 n = physPageSize - pc%physPageSize 749 } 750 print("instruction bytes:") 751 b := (*[maxN]byte)(unsafe.Pointer(pc)) 752 for i := uintptr(0); i < n; i++ { 753 print(" ", hex(b[i])) 754 } 755 println() 756 } 757 print("\n") 758 759 level, _, docrash := gotraceback() 760 if level > 0 { 761 goroutineheader(gp) 762 tracebacktrap(c.sigpc(), c.sigsp(), c.siglr(), gp) 763 if crashing > 0 && gp != _g_.m.curg && _g_.m.curg != nil && readgstatus(_g_.m.curg)&^_Gscan == _Grunning { 764 // tracebackothers on original m skipped this one; trace it now. 765 goroutineheader(_g_.m.curg) 766 traceback(^uintptr(0), ^uintptr(0), 0, _g_.m.curg) 767 } else if crashing == 0 { 768 tracebackothers(gp) 769 print("\n") 770 } 771 dumpregs(c) 772 } 773 774 if docrash { 775 crashing++ 776 if crashing < mcount()-int32(extraMCount) { 777 // There are other m's that need to dump their stacks. 778 // Relay SIGQUIT to the next m by sending it to the current process. 779 // All m's that have already received SIGQUIT have signal masks blocking 780 // receipt of any signals, so the SIGQUIT will go to an m that hasn't seen it yet. 781 // When the last m receives the SIGQUIT, it will fall through to the call to 782 // crash below. Just in case the relaying gets botched, each m involved in 783 // the relay sleeps for 5 seconds and then does the crash/exit itself. 784 // In expected operation, the last m has received the SIGQUIT and run 785 // crash/exit and the process is gone, all long before any of the 786 // 5-second sleeps have finished. 787 print("\n-----\n\n") 788 raiseproc(_SIGQUIT) 789 usleep(5 * 1000 * 1000) 790 } 791 crash() 792 } 793 794 printDebugLog() 795 796 exit(2) 797 } 798 799 // sigpanic turns a synchronous signal into a run-time panic. 800 // If the signal handler sees a synchronous panic, it arranges the 801 // stack to look like the function where the signal occurred called 802 // sigpanic, sets the signal's PC value to sigpanic, and returns from 803 // the signal handler. The effect is that the program will act as 804 // though the function that got the signal simply called sigpanic 805 // instead. 806 // 807 // This must NOT be nosplit because the linker doesn't know where 808 // sigpanic calls can be injected. 809 // 810 // The signal handler must not inject a call to sigpanic if 811 // getg().throwsplit, since sigpanic may need to grow the stack. 812 // 813 // This is exported via linkname to assembly in runtime/cgo. 814 // 815 //go:linkname sigpanic 816 func sigpanic() { 817 g := getg() 818 if !canpanic(g) { 819 throw("unexpected signal during runtime execution") 820 } 821 822 switch g.sig { 823 case _SIGBUS: 824 if g.sigcode0 == _BUS_ADRERR && g.sigcode1 < 0x1000 { 825 panicmem() 826 } 827 // Support runtime/debug.SetPanicOnFault. 828 if g.paniconfault { 829 panicmemAddr(g.sigcode1) 830 } 831 print("unexpected fault address ", hex(g.sigcode1), "\n") 832 throw("fault") 833 case _SIGSEGV: 834 if (g.sigcode0 == 0 || g.sigcode0 == _SEGV_MAPERR || g.sigcode0 == _SEGV_ACCERR) && g.sigcode1 < 0x1000 { 835 panicmem() 836 } 837 // Support runtime/debug.SetPanicOnFault. 838 if g.paniconfault { 839 panicmemAddr(g.sigcode1) 840 } 841 print("unexpected fault address ", hex(g.sigcode1), "\n") 842 throw("fault") 843 case _SIGFPE: 844 switch g.sigcode0 { 845 case _FPE_INTDIV: 846 panicdivide() 847 case _FPE_INTOVF: 848 panicoverflow() 849 } 850 panicfloat() 851 } 852 853 if g.sig >= uint32(len(sigtable)) { 854 // can't happen: we looked up g.sig in sigtable to decide to call sigpanic 855 throw("unexpected signal value") 856 } 857 panic(errorString(sigtable[g.sig].name)) 858 } 859 860 // dieFromSignal kills the program with a signal. 861 // This provides the expected exit status for the shell. 862 // This is only called with fatal signals expected to kill the process. 863 // 864 //go:nosplit 865 //go:nowritebarrierrec 866 func dieFromSignal(sig uint32) { 867 unblocksig(sig) 868 // Mark the signal as unhandled to ensure it is forwarded. 869 atomic.Store(&handlingSig[sig], 0) 870 raise(sig) 871 872 // That should have killed us. On some systems, though, raise 873 // sends the signal to the whole process rather than to just 874 // the current thread, which means that the signal may not yet 875 // have been delivered. Give other threads a chance to run and 876 // pick up the signal. 877 osyield() 878 osyield() 879 osyield() 880 881 // If that didn't work, try _SIG_DFL. 882 setsig(sig, _SIG_DFL) 883 raise(sig) 884 885 osyield() 886 osyield() 887 osyield() 888 889 // If we are still somehow running, just exit with the wrong status. 890 exit(2) 891 } 892 893 // raisebadsignal is called when a signal is received on a non-Go 894 // thread, and the Go program does not want to handle it (that is, the 895 // program has not called os/signal.Notify for the signal). 896 func raisebadsignal(sig uint32, c *sigctxt) { 897 if sig == _SIGPROF { 898 // Ignore profiling signals that arrive on non-Go threads. 899 return 900 } 901 902 var handler uintptr 903 if sig >= _NSIG { 904 handler = _SIG_DFL 905 } else { 906 handler = atomic.Loaduintptr(&fwdSig[sig]) 907 } 908 909 // Reset the signal handler and raise the signal. 910 // We are currently running inside a signal handler, so the 911 // signal is blocked. We need to unblock it before raising the 912 // signal, or the signal we raise will be ignored until we return 913 // from the signal handler. We know that the signal was unblocked 914 // before entering the handler, or else we would not have received 915 // it. That means that we don't have to worry about blocking it 916 // again. 917 unblocksig(sig) 918 setsig(sig, handler) 919 920 // If we're linked into a non-Go program we want to try to 921 // avoid modifying the original context in which the signal 922 // was raised. If the handler is the default, we know it 923 // is non-recoverable, so we don't have to worry about 924 // re-installing sighandler. At this point we can just 925 // return and the signal will be re-raised and caught by 926 // the default handler with the correct context. 927 // 928 // On FreeBSD, the libthr sigaction code prevents 929 // this from working so we fall through to raise. 930 if GOOS != "freebsd" && (isarchive || islibrary) && handler == _SIG_DFL && c.sigcode() != _SI_USER { 931 return 932 } 933 934 raise(sig) 935 936 // Give the signal a chance to be delivered. 937 // In almost all real cases the program is about to crash, 938 // so sleeping here is not a waste of time. 939 usleep(1000) 940 941 // If the signal didn't cause the program to exit, restore the 942 // Go signal handler and carry on. 943 // 944 // We may receive another instance of the signal before we 945 // restore the Go handler, but that is not so bad: we know 946 // that the Go program has been ignoring the signal. 947 setsig(sig, abi.FuncPCABIInternal(sighandler)) 948 } 949 950 //go:nosplit 951 func crash() { 952 // OS X core dumps are linear dumps of the mapped memory, 953 // from the first virtual byte to the last, with zeros in the gaps. 954 // Because of the way we arrange the address space on 64-bit systems, 955 // this means the OS X core file will be >128 GB and even on a zippy 956 // workstation can take OS X well over an hour to write (uninterruptible). 957 // Save users from making that mistake. 958 if GOOS == "darwin" && GOARCH == "amd64" { 959 return 960 } 961 962 dieFromSignal(_SIGABRT) 963 } 964 965 // ensureSigM starts one global, sleeping thread to make sure at least one thread 966 // is available to catch signals enabled for os/signal. 967 func ensureSigM() { 968 if maskUpdatedChan != nil { 969 return 970 } 971 maskUpdatedChan = make(chan struct{}) 972 disableSigChan = make(chan uint32) 973 enableSigChan = make(chan uint32) 974 go func() { 975 // Signal masks are per-thread, so make sure this goroutine stays on one 976 // thread. 977 LockOSThread() 978 defer UnlockOSThread() 979 // The sigBlocked mask contains the signals not active for os/signal, 980 // initially all signals except the essential. When signal.Notify()/Stop is called, 981 // sigenable/sigdisable in turn notify this thread to update its signal 982 // mask accordingly. 983 sigBlocked := sigset_all 984 for i := range sigtable { 985 if !blockableSig(uint32(i)) { 986 sigdelset(&sigBlocked, i) 987 } 988 } 989 sigprocmask(_SIG_SETMASK, &sigBlocked, nil) 990 for { 991 select { 992 case sig := <-enableSigChan: 993 if sig > 0 { 994 sigdelset(&sigBlocked, int(sig)) 995 } 996 case sig := <-disableSigChan: 997 if sig > 0 && blockableSig(sig) { 998 sigaddset(&sigBlocked, int(sig)) 999 } 1000 } 1001 sigprocmask(_SIG_SETMASK, &sigBlocked, nil) 1002 maskUpdatedChan <- struct{}{} 1003 } 1004 }() 1005 } 1006 1007 // This is called when we receive a signal when there is no signal stack. 1008 // This can only happen if non-Go code calls sigaltstack to disable the 1009 // signal stack. 1010 func noSignalStack(sig uint32) { 1011 println("signal", sig, "received on thread with no signal stack") 1012 throw("non-Go code disabled sigaltstack") 1013 } 1014 1015 // This is called if we receive a signal when there is a signal stack 1016 // but we are not on it. This can only happen if non-Go code called 1017 // sigaction without setting the SS_ONSTACK flag. 1018 func sigNotOnStack(sig uint32) { 1019 println("signal", sig, "received but handler not on signal stack") 1020 throw("non-Go code set up signal handler without SA_ONSTACK flag") 1021 } 1022 1023 // signalDuringFork is called if we receive a signal while doing a fork. 1024 // We do not want signals at that time, as a signal sent to the process 1025 // group may be delivered to the child process, causing confusion. 1026 // This should never be called, because we block signals across the fork; 1027 // this function is just a safety check. See issue 18600 for background. 1028 func signalDuringFork(sig uint32) { 1029 println("signal", sig, "received during fork") 1030 throw("signal received during fork") 1031 } 1032 1033 var badginsignalMsg = "fatal: bad g in signal handler\n" 1034 1035 // This runs on a foreign stack, without an m or a g. No stack split. 1036 // 1037 //go:nosplit 1038 //go:norace 1039 //go:nowritebarrierrec 1040 func badsignal(sig uintptr, c *sigctxt) { 1041 if !iscgo && !cgoHasExtraM { 1042 // There is no extra M. needm will not be able to grab 1043 // an M. Instead of hanging, just crash. 1044 // Cannot call split-stack function as there is no G. 1045 s := stringStructOf(&badginsignalMsg) 1046 write(2, s.str, int32(s.len)) 1047 exit(2) 1048 *(*uintptr)(unsafe.Pointer(uintptr(123))) = 2 1049 } 1050 needm() 1051 if !sigsend(uint32(sig)) { 1052 // A foreign thread received the signal sig, and the 1053 // Go code does not want to handle it. 1054 raisebadsignal(uint32(sig), c) 1055 } 1056 dropm() 1057 } 1058 1059 //go:noescape 1060 func sigfwd(fn uintptr, sig uint32, info *siginfo, ctx unsafe.Pointer) 1061 1062 // Determines if the signal should be handled by Go and if not, forwards the 1063 // signal to the handler that was installed before Go's. Returns whether the 1064 // signal was forwarded. 1065 // This is called by the signal handler, and the world may be stopped. 1066 // 1067 //go:nosplit 1068 //go:nowritebarrierrec 1069 func sigfwdgo(sig uint32, info *siginfo, ctx unsafe.Pointer) bool { 1070 if sig >= uint32(len(sigtable)) { 1071 return false 1072 } 1073 fwdFn := atomic.Loaduintptr(&fwdSig[sig]) 1074 flags := sigtable[sig].flags 1075 1076 // If we aren't handling the signal, forward it. 1077 if atomic.Load(&handlingSig[sig]) == 0 || !signalsOK { 1078 // If the signal is ignored, doing nothing is the same as forwarding. 1079 if fwdFn == _SIG_IGN || (fwdFn == _SIG_DFL && flags&_SigIgn != 0) { 1080 return true 1081 } 1082 // We are not handling the signal and there is no other handler to forward to. 1083 // Crash with the default behavior. 1084 if fwdFn == _SIG_DFL { 1085 setsig(sig, _SIG_DFL) 1086 dieFromSignal(sig) 1087 return false 1088 } 1089 1090 sigfwd(fwdFn, sig, info, ctx) 1091 return true 1092 } 1093 1094 // This function and its caller sigtrampgo assumes SIGPIPE is delivered on the 1095 // originating thread. This property does not hold on macOS (golang.org/issue/33384), 1096 // so we have no choice but to ignore SIGPIPE. 1097 if (GOOS == "darwin" || GOOS == "ios") && sig == _SIGPIPE { 1098 return true 1099 } 1100 1101 // If there is no handler to forward to, no need to forward. 1102 if fwdFn == _SIG_DFL { 1103 return false 1104 } 1105 1106 c := &sigctxt{info, ctx} 1107 // Only forward synchronous signals and SIGPIPE. 1108 // Unfortunately, user generated SIGPIPEs will also be forwarded, because si_code 1109 // is set to _SI_USER even for a SIGPIPE raised from a write to a closed socket 1110 // or pipe. 1111 if (c.sigcode() == _SI_USER || flags&_SigPanic == 0) && sig != _SIGPIPE { 1112 return false 1113 } 1114 // Determine if the signal occurred inside Go code. We test that: 1115 // (1) we weren't in VDSO page, 1116 // (2) we were in a goroutine (i.e., m.curg != nil), and 1117 // (3) we weren't in CGO. 1118 g := sigFetchG(c) 1119 if g != nil && g.m != nil && g.m.curg != nil && !g.m.incgo { 1120 return false 1121 } 1122 1123 // Signal not handled by Go, forward it. 1124 if fwdFn != _SIG_IGN { 1125 sigfwd(fwdFn, sig, info, ctx) 1126 } 1127 1128 return true 1129 } 1130 1131 // sigsave saves the current thread's signal mask into *p. 1132 // This is used to preserve the non-Go signal mask when a non-Go 1133 // thread calls a Go function. 1134 // This is nosplit and nowritebarrierrec because it is called by needm 1135 // which may be called on a non-Go thread with no g available. 1136 // 1137 //go:nosplit 1138 //go:nowritebarrierrec 1139 func sigsave(p *sigset) { 1140 sigprocmask(_SIG_SETMASK, nil, p) 1141 } 1142 1143 // msigrestore sets the current thread's signal mask to sigmask. 1144 // This is used to restore the non-Go signal mask when a non-Go thread 1145 // calls a Go function. 1146 // This is nosplit and nowritebarrierrec because it is called by dropm 1147 // after g has been cleared. 1148 // 1149 //go:nosplit 1150 //go:nowritebarrierrec 1151 func msigrestore(sigmask sigset) { 1152 sigprocmask(_SIG_SETMASK, &sigmask, nil) 1153 } 1154 1155 // sigsetAllExiting is used by sigblock(true) when a thread is 1156 // exiting. sigset_all is defined in OS specific code, and per GOOS 1157 // behavior may override this default for sigsetAllExiting: see 1158 // osinit(). 1159 var sigsetAllExiting = sigset_all 1160 1161 // sigblock blocks signals in the current thread's signal mask. 1162 // This is used to block signals while setting up and tearing down g 1163 // when a non-Go thread calls a Go function. When a thread is exiting 1164 // we use the sigsetAllExiting value, otherwise the OS specific 1165 // definition of sigset_all is used. 1166 // This is nosplit and nowritebarrierrec because it is called by needm 1167 // which may be called on a non-Go thread with no g available. 1168 // 1169 //go:nosplit 1170 //go:nowritebarrierrec 1171 func sigblock(exiting bool) { 1172 if exiting { 1173 sigprocmask(_SIG_SETMASK, &sigsetAllExiting, nil) 1174 return 1175 } 1176 sigprocmask(_SIG_SETMASK, &sigset_all, nil) 1177 } 1178 1179 // unblocksig removes sig from the current thread's signal mask. 1180 // This is nosplit and nowritebarrierrec because it is called from 1181 // dieFromSignal, which can be called by sigfwdgo while running in the 1182 // signal handler, on the signal stack, with no g available. 1183 // 1184 //go:nosplit 1185 //go:nowritebarrierrec 1186 func unblocksig(sig uint32) { 1187 var set sigset 1188 sigaddset(&set, int(sig)) 1189 sigprocmask(_SIG_UNBLOCK, &set, nil) 1190 } 1191 1192 // minitSignals is called when initializing a new m to set the 1193 // thread's alternate signal stack and signal mask. 1194 func minitSignals() { 1195 minitSignalStack() 1196 minitSignalMask() 1197 } 1198 1199 // minitSignalStack is called when initializing a new m to set the 1200 // alternate signal stack. If the alternate signal stack is not set 1201 // for the thread (the normal case) then set the alternate signal 1202 // stack to the gsignal stack. If the alternate signal stack is set 1203 // for the thread (the case when a non-Go thread sets the alternate 1204 // signal stack and then calls a Go function) then set the gsignal 1205 // stack to the alternate signal stack. We also set the alternate 1206 // signal stack to the gsignal stack if cgo is not used (regardless 1207 // of whether it is already set). Record which choice was made in 1208 // newSigstack, so that it can be undone in unminit. 1209 func minitSignalStack() { 1210 _g_ := getg() 1211 var st stackt 1212 sigaltstack(nil, &st) 1213 if st.ss_flags&_SS_DISABLE != 0 || !iscgo { 1214 signalstack(&_g_.m.gsignal.stack) 1215 _g_.m.newSigstack = true 1216 } else { 1217 setGsignalStack(&st, &_g_.m.goSigStack) 1218 _g_.m.newSigstack = false 1219 } 1220 } 1221 1222 // minitSignalMask is called when initializing a new m to set the 1223 // thread's signal mask. When this is called all signals have been 1224 // blocked for the thread. This starts with m.sigmask, which was set 1225 // either from initSigmask for a newly created thread or by calling 1226 // sigsave if this is a non-Go thread calling a Go function. It 1227 // removes all essential signals from the mask, thus causing those 1228 // signals to not be blocked. Then it sets the thread's signal mask. 1229 // After this is called the thread can receive signals. 1230 func minitSignalMask() { 1231 nmask := getg().m.sigmask 1232 for i := range sigtable { 1233 if !blockableSig(uint32(i)) { 1234 sigdelset(&nmask, i) 1235 } 1236 } 1237 sigprocmask(_SIG_SETMASK, &nmask, nil) 1238 } 1239 1240 // unminitSignals is called from dropm, via unminit, to undo the 1241 // effect of calling minit on a non-Go thread. 1242 // 1243 //go:nosplit 1244 func unminitSignals() { 1245 if getg().m.newSigstack { 1246 st := stackt{ss_flags: _SS_DISABLE} 1247 sigaltstack(&st, nil) 1248 } else { 1249 // We got the signal stack from someone else. Restore 1250 // the Go-allocated stack in case this M gets reused 1251 // for another thread (e.g., it's an extram). Also, on 1252 // Android, libc allocates a signal stack for all 1253 // threads, so it's important to restore the Go stack 1254 // even on Go-created threads so we can free it. 1255 restoreGsignalStack(&getg().m.goSigStack) 1256 } 1257 } 1258 1259 // blockableSig reports whether sig may be blocked by the signal mask. 1260 // We never want to block the signals marked _SigUnblock; 1261 // these are the synchronous signals that turn into a Go panic. 1262 // We never want to block the preemption signal if it is being used. 1263 // In a Go program--not a c-archive/c-shared--we never want to block 1264 // the signals marked _SigKill or _SigThrow, as otherwise it's possible 1265 // for all running threads to block them and delay their delivery until 1266 // we start a new thread. When linked into a C program we let the C code 1267 // decide on the disposition of those signals. 1268 func blockableSig(sig uint32) bool { 1269 flags := sigtable[sig].flags 1270 if flags&_SigUnblock != 0 { 1271 return false 1272 } 1273 if sig == sigPreempt && preemptMSupported && debug.asyncpreemptoff == 0 { 1274 return false 1275 } 1276 if isarchive || islibrary { 1277 return true 1278 } 1279 return flags&(_SigKill|_SigThrow) == 0 1280 } 1281 1282 // gsignalStack saves the fields of the gsignal stack changed by 1283 // setGsignalStack. 1284 type gsignalStack struct { 1285 stack stack 1286 stackguard0 uintptr 1287 stackguard1 uintptr 1288 stktopsp uintptr 1289 } 1290 1291 // setGsignalStack sets the gsignal stack of the current m to an 1292 // alternate signal stack returned from the sigaltstack system call. 1293 // It saves the old values in *old for use by restoreGsignalStack. 1294 // This is used when handling a signal if non-Go code has set the 1295 // alternate signal stack. 1296 // 1297 //go:nosplit 1298 //go:nowritebarrierrec 1299 func setGsignalStack(st *stackt, old *gsignalStack) { 1300 g := getg() 1301 if old != nil { 1302 old.stack = g.m.gsignal.stack 1303 old.stackguard0 = g.m.gsignal.stackguard0 1304 old.stackguard1 = g.m.gsignal.stackguard1 1305 old.stktopsp = g.m.gsignal.stktopsp 1306 } 1307 stsp := uintptr(unsafe.Pointer(st.ss_sp)) 1308 g.m.gsignal.stack.lo = stsp 1309 g.m.gsignal.stack.hi = stsp + st.ss_size 1310 g.m.gsignal.stackguard0 = stsp + _StackGuard 1311 g.m.gsignal.stackguard1 = stsp + _StackGuard 1312 } 1313 1314 // restoreGsignalStack restores the gsignal stack to the value it had 1315 // before entering the signal handler. 1316 // 1317 //go:nosplit 1318 //go:nowritebarrierrec 1319 func restoreGsignalStack(st *gsignalStack) { 1320 gp := getg().m.gsignal 1321 gp.stack = st.stack 1322 gp.stackguard0 = st.stackguard0 1323 gp.stackguard1 = st.stackguard1 1324 gp.stktopsp = st.stktopsp 1325 } 1326 1327 // signalstack sets the current thread's alternate signal stack to s. 1328 // 1329 //go:nosplit 1330 func signalstack(s *stack) { 1331 st := stackt{ss_size: s.hi - s.lo} 1332 setSignalstackSP(&st, s.lo) 1333 sigaltstack(&st, nil) 1334 } 1335 1336 // setsigsegv is used on darwin/arm64 to fake a segmentation fault. 1337 // 1338 // This is exported via linkname to assembly in runtime/cgo. 1339 // 1340 //go:nosplit 1341 //go:linkname setsigsegv 1342 func setsigsegv(pc uintptr) { 1343 g := getg() 1344 g.sig = _SIGSEGV 1345 g.sigpc = pc 1346 g.sigcode0 = _SEGV_MAPERR 1347 g.sigcode1 = 0 // TODO: emulate si_addr 1348 } 1349