1 // Copyright 2009 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.
12 // The code in this file implements stack trace walking for all architectures.
13 // The most important fact about a given architecture is whether it uses a link register.
14 // On systems with link registers, the prologue for a non-leaf function stores the
15 // incoming value of LR at the bottom of the newly allocated stack frame.
16 // On systems without link registers, the architecture pushes a return PC during
17 // the call instruction, so the return PC ends up above the stack frame.
18 // In this file, the return PC is always called LR, no matter how it was found.
20 // To date, the opposite of a link register architecture is an x86 architecture.
21 // This code may need to change if some other kind of non-link-register
22 // architecture comes along.
24 // The other important fact is the size of a pointer: on 32-bit systems the LR
25 // takes up only 4 bytes on the stack, while on 64-bit systems it takes up 8 bytes.
26 // Typically this is ptrSize.
28 // As an exception, amd64p32 has ptrSize == 4 but the CALL instruction still
29 // stores an 8-byte return PC onto the stack. To accommodate this, we use regSize
30 // as the size of the architecture-pushed return PC.
32 // usesLR is defined below in terms of minFrameSize, which is defined in
33 // arch_$GOARCH.go. ptrSize and regSize are defined in stubs.go.
35 const usesLR = sys.MinFrameSize > 0
38 // initialized in tracebackinit
48 forcegchelperPC uintptr
50 gcBgMarkWorkerPC uintptr
51 systemstack_switchPC uintptr
53 stackBarrierPC uintptr
54 cgocallback_gofuncPC uintptr
58 externalthreadhandlerp uintptr // initialized elsewhere
61 func tracebackinit() {
62 // Go variable initialization happens late during runtime startup.
63 // Instead of initializing the variables above in the declarations,
64 // schedinit calls this function so that the variables are
65 // initialized and available earlier in the startup sequence.
66 goexitPC = funcPC(goexit)
67 jmpdeferPC = funcPC(jmpdefer)
68 mcallPC = funcPC(mcall)
69 morestackPC = funcPC(morestack)
70 mstartPC = funcPC(mstart)
71 rt0_goPC = funcPC(rt0_go)
72 sigpanicPC = funcPC(sigpanic)
73 runfinqPC = funcPC(runfinq)
74 bgsweepPC = funcPC(bgsweep)
75 forcegchelperPC = funcPC(forcegchelper)
76 timerprocPC = funcPC(timerproc)
77 gcBgMarkWorkerPC = funcPC(gcBgMarkWorker)
78 systemstack_switchPC = funcPC(systemstack_switch)
79 systemstackPC = funcPC(systemstack)
80 stackBarrierPC = funcPC(stackBarrier)
81 cgocallback_gofuncPC = funcPC(cgocallback_gofunc)
83 // used by sigprof handler
87 // Traceback over the deferred function calls.
88 // Report them like calls that have been invoked but not started executing yet.
89 func tracebackdefers(gp *g, callback func(*stkframe, unsafe.Pointer) bool, v unsafe.Pointer) {
91 for d := gp._defer; d != nil; d = d.link {
94 // Defer of nil function. Args don't matter.
101 frame.pc = uintptr(fn.fn)
102 f := findfunc(frame.pc)
104 print("runtime: unknown pc in defer ", hex(frame.pc), "\n")
108 frame.argp = uintptr(deferArgs(d))
109 setArgInfo(&frame, f, true)
111 frame.continpc = frame.pc
112 if !callback((*stkframe)(noescape(unsafe.Pointer(&frame))), v) {
118 // Generic traceback. Handles runtime stack prints (pcbuf == nil),
119 // the runtime.Callers function (pcbuf != nil), as well as the garbage
120 // collector (callback != nil). A little clunky to merge these, but avoids
121 // duplicating the code and all its subtlety.
122 func gentraceback(pc0, sp0, lr0 uintptr, gp *g, skip int, pcbuf *uintptr, max int, callback func(*stkframe, unsafe.Pointer) bool, v unsafe.Pointer, flags uint) int {
124 throw("gentraceback before goexitPC initialization")
127 if g == gp && g == g.m.curg {
128 // The starting sp has been passed in as a uintptr, and the caller may
129 // have other uintptr-typed stack references as well.
130 // If during one of the calls that got us here or during one of the
131 // callbacks below the stack must be grown, all these uintptr references
132 // to the stack will not be updated, and gentraceback will continue
133 // to inspect the old stack memory, which may no longer be valid.
134 // Even if all the variables were updated correctly, it is not clear that
135 // we want to expose a traceback that begins on one stack and ends
136 // on another stack. That could confuse callers quite a bit.
137 // Instead, we require that gentraceback and any other function that
138 // accepts an sp for the current goroutine (typically obtained by
139 // calling getcallersp) must not run on that goroutine's stack but
140 // instead on the g0 stack.
141 throw("gentraceback cannot trace user goroutine on its own stack")
143 level, _, _ := gotraceback()
145 // Fix up returns to the stack barrier by fetching the
146 // original return PC from gp.stkbar.
147 stkbar := gp.stkbar[gp.stkbarPos:]
149 if pc0 == ^uintptr(0) && sp0 == ^uintptr(0) { // Signal to fetch saved values from gp.
150 if gp.syscallsp != 0 {
173 printing := pcbuf == nil && callback == nil
176 for _defer != nil && uintptr(_defer.sp) == _NoArgs {
180 // If the PC is zero, it's likely a nil function call.
181 // Start in the caller's frame.
184 frame.pc = *(*uintptr)(unsafe.Pointer(frame.sp))
187 frame.pc = uintptr(*(*sys.Uintreg)(unsafe.Pointer(frame.sp)))
188 frame.sp += sys.RegSize
192 f := findfunc(frame.pc)
195 print("runtime: unknown pc ", hex(frame.pc), "\n")
202 var cache pcvalueCache
207 // pc is the PC of the running function.
208 // sp is the stack pointer at that program counter.
209 // fp is the frame pointer (caller's stack pointer) at that program counter, or nil if unknown.
210 // stk is the stack containing sp.
211 // The caller's program counter is lr, unless lr is zero, in which case it is *(uintptr*)sp.
214 // Found an actual function.
215 // Derive frame pointer and link register.
217 // We want to jump over the systemstack switch. If we're running on the
218 // g0, this systemstack is at the top of the stack.
219 // if we're not on g0 or there's a no curg, then this is a regular call.
221 if flags&_TraceJumpStack != 0 && f.entry == systemstackPC && gp == g.m.g0 && gp.m.curg != nil {
222 sp = gp.m.curg.sched.sp
223 stkbar = gp.m.curg.stkbar[gp.m.curg.stkbarPos:]
225 frame.fp = sp + uintptr(funcspdelta(f, frame.pc, &cache))
227 // On x86, call instruction pushes return PC before entering new function.
228 frame.fp += sys.RegSize
235 } else if usesLR && f.entry == jmpdeferPC {
236 // jmpdefer modifies SP/LR/PC non-atomically.
237 // If a profiling interrupt arrives during jmpdefer,
238 // the stack unwind may see a mismatched register set
239 // and get confused. Stop if we see PC within jmpdefer
240 // to avoid that confusion.
241 // See golang.org/issue/8153.
243 throw("traceback_arm: found jmpdefer when tracing with callback")
249 if n == 0 && frame.sp < frame.fp || frame.lr == 0 {
251 frame.lr = *(*uintptr)(unsafe.Pointer(lrPtr))
255 lrPtr = frame.fp - sys.RegSize
256 frame.lr = uintptr(*(*sys.Uintreg)(unsafe.Pointer(lrPtr)))
259 if frame.lr == stackBarrierPC {
260 // Recover original PC.
261 if stkbar[0].savedLRPtr != lrPtr {
262 print("found next stack barrier at ", hex(lrPtr), "; expected ")
263 gcPrintStkbars(stkbar)
265 throw("missed stack barrier")
267 frame.lr = stkbar[0].savedLRVal
270 flr = findfunc(frame.lr)
272 // This happens if you get a profiling interrupt at just the wrong time.
273 // In that context it is okay to stop early.
274 // But if callback is set, we're doing a garbage collection and must
275 // get everything, so crash loudly.
277 print("runtime: unexpected return pc for ", funcname(f), " called from ", hex(frame.lr), "\n")
278 throw("unknown caller pc")
283 frame.varp = frame.fp
285 // On x86, call instruction pushes return PC before entering new function.
286 frame.varp -= sys.RegSize
289 // If framepointer_enabled and there's a frame, then
290 // there's a saved bp here.
291 if framepointer_enabled && GOARCH == "amd64" && frame.varp > frame.sp {
292 frame.varp -= sys.RegSize
295 // Derive size of arguments.
296 // Most functions have a fixed-size argument block,
297 // so we can use metadata about the function f.
298 // Not all, though: there are some variadic functions
299 // in package runtime and reflect, and for those we use call-specific
300 // metadata recorded by f's caller.
301 if callback != nil || printing {
302 frame.argp = frame.fp + sys.MinFrameSize
303 setArgInfo(&frame, f, callback != nil)
306 // Determine frame's 'continuation PC', where it can continue.
307 // Normally this is the return address on the stack, but if sigpanic
308 // is immediately below this function on the stack, then the frame
309 // stopped executing due to a trap, and frame.pc is probably not
310 // a safe point for looking up liveness information. In this panicking case,
311 // the function either doesn't return at all (if it has no defers or if the
312 // defers do not recover) or it returns from one of the calls to
313 // deferproc a second time (if the corresponding deferred func recovers).
314 // It suffices to assume that the most recent deferproc is the one that
315 // returns; everything live at earlier deferprocs is still live at that one.
316 frame.continpc = frame.pc
318 if _defer != nil && _defer.sp == frame.sp {
319 frame.continpc = _defer.pc
325 // Unwind our local defer stack past this frame.
326 for _defer != nil && (_defer.sp == frame.sp || _defer.sp == _NoArgs) {
336 (*[1 << 20]uintptr)(unsafe.Pointer(pcbuf))[n] = frame.pc
339 if !callback((*stkframe)(noescape(unsafe.Pointer(&frame))), v) {
344 if (flags&_TraceRuntimeFrames) != 0 || showframe(f, gp) {
345 // Print during crash.
346 // main(0x1, 0x2, 0x3)
347 // /home/rsc/go/src/runtime/x.go:23 +0xf
349 tracepc := frame.pc // back up to CALL instruction for funcline.
350 if (n > 0 || flags&_TraceTrap == 0) && frame.pc > f.entry && !waspanic {
353 print(funcname(f), "(")
354 argp := (*[100]uintptr)(unsafe.Pointer(frame.argp))
355 for i := uintptr(0); i < frame.arglen/sys.PtrSize; i++ {
366 file, line := funcline(f, tracepc)
367 print("\t", file, ":", line)
368 if frame.pc > f.entry {
369 print(" +", hex(frame.pc-f.entry))
371 if g.m.throwing > 0 && gp == g.m.curg || level >= 2 {
372 print(" fp=", hex(frame.fp), " sp=", hex(frame.sp))
381 waspanic = f.entry == sigpanicPC
383 // Do not unwind past the bottom of the stack.
388 // Unwind to next frame.
396 // On link register architectures, sighandler saves the LR on stack
397 // before faking a call to sigpanic.
398 if usesLR && waspanic {
399 x := *(*uintptr)(unsafe.Pointer(frame.sp))
400 frame.sp += sys.MinFrameSize
401 if GOARCH == "arm64" {
402 // arm64 needs 16-byte aligned SP, always
403 frame.sp += sys.PtrSize
405 f = findfunc(frame.pc)
409 } else if funcspdelta(f, frame.pc, &cache) == 0 {
419 // If callback != nil, we're being called to gather stack information during
420 // garbage collection or stack growth. In that context, require that we used
421 // up the entire defer stack. If not, then there is a bug somewhere and the
422 // garbage collection or stack growth may not have seen the correct picture
423 // of the stack. Crash now instead of silently executing the garbage collection
424 // or stack copy incorrectly and setting up for a mysterious crash later.
426 // Note that panic != nil is okay here: there can be leftover panics,
427 // because the defers on the panic stack do not nest in frame order as
428 // they do on the defer stack. If you have:
434 // frame 4's panic starts running defers
435 // frame 5, running d3, defers d4
437 // frame 5's panic starts running defers
438 // frame 6, running d4, garbage collects
439 // frame 6, running d2, garbage collects
441 // During the execution of d4, the panic stack is d4 -> d3, which
442 // is nested properly, and we'll treat frame 3 as resumable, because we
443 // can find d3. (And in fact frame 3 is resumable. If d4 recovers
444 // and frame 5 continues running, d3, d3 can recover and we'll
445 // resume execution in (returning from) frame 3.)
447 // During the execution of d2, however, the panic stack is d2 -> d3,
448 // which is inverted. The scan will match d2 to frame 2 but having
449 // d2 on the stack until then means it will not match d3 to frame 3.
450 // This is okay: if we're running d2, then all the defers after d2 have
451 // completed and their corresponding frames are dead. Not finding d3
452 // for frame 3 means we'll set frame 3's continpc == 0, which is correct
453 // (frame 3 is dead). At the end of the walk the panic stack can thus
454 // contain defers (d3 in this case) for dead frames. The inversion here
455 // always indicates a dead frame, and the effect of the inversion on the
456 // scan is to hide those dead frames, so the scan is still okay:
457 // what's left on the panic stack are exactly (and only) the dead frames.
459 // We require callback != nil here because only when callback != nil
460 // do we know that gentraceback is being called in a "must be correct"
461 // context as opposed to a "best effort" context. The tracebacks with
462 // callbacks only happen when everything is stopped nicely.
463 // At other times, such as when gathering a stack for a profiling signal
464 // or when printing a traceback during a crash, everything may not be
465 // stopped nicely, and the stack walk may not be able to complete.
466 // It's okay in those situations not to use up the entire defer stack:
467 // incomplete information then is still better than nothing.
468 if callback != nil && n < max && _defer != nil {
470 print("runtime: g", gp.goid, ": leftover defer sp=", hex(_defer.sp), " pc=", hex(_defer.pc), "\n")
472 for _defer = gp._defer; _defer != nil; _defer = _defer.link {
473 print("\tdefer ", _defer, " sp=", hex(_defer.sp), " pc=", hex(_defer.pc), "\n")
475 throw("traceback has leftover defers")
478 if callback != nil && n < max && len(stkbar) > 0 {
479 print("runtime: g", gp.goid, ": leftover stack barriers ")
480 gcPrintStkbars(stkbar)
482 throw("traceback has leftover stack barriers")
485 if callback != nil && n < max && frame.sp != gp.stktopsp {
486 print("runtime: g", gp.goid, ": frame.sp=", hex(frame.sp), " top=", hex(gp.stktopsp), "\n")
487 print("\tstack=[", hex(gp.stack.lo), "-", hex(gp.stack.hi), "] n=", n, " max=", max, "\n")
488 throw("traceback did not unwind completely")
494 func setArgInfo(frame *stkframe, f *_func, needArgMap bool) {
495 frame.arglen = uintptr(f.args)
496 if needArgMap && f.args == _ArgsSizeUnknown {
497 // Extract argument bitmaps for reflect stubs from the calls they made to reflect.
499 case "reflect.makeFuncStub", "reflect.methodValueCall":
500 arg0 := frame.sp + sys.MinFrameSize
501 fn := *(**[2]uintptr)(unsafe.Pointer(arg0))
502 if fn[0] != f.entry {
503 print("runtime: confused by ", funcname(f), "\n")
504 throw("reflect mismatch")
506 bv := (*bitvector)(unsafe.Pointer(fn[1]))
507 frame.arglen = uintptr(bv.n * sys.PtrSize)
513 func printcreatedby(gp *g) {
514 // Show what created goroutine, except main goroutine (goid 1).
517 if f != nil && showframe(f, gp) && gp.goid != 1 {
518 print("created by ", funcname(f), "\n")
519 tracepc := pc // back up to CALL instruction for funcline.
521 tracepc -= sys.PCQuantum
523 file, line := funcline(f, tracepc)
524 print("\t", file, ":", line)
526 print(" +", hex(pc-f.entry))
532 func traceback(pc, sp, lr uintptr, gp *g) {
533 traceback1(pc, sp, lr, gp, 0)
536 // tracebacktrap is like traceback but expects that the PC and SP were obtained
537 // from a trap, not from gp->sched or gp->syscallpc/gp->syscallsp or getcallerpc/getcallersp.
538 // Because they are from a trap instead of from a saved pair,
539 // the initial PC must not be rewound to the previous instruction.
540 // (All the saved pairs record a PC that is a return address, so we
541 // rewind it into the CALL instruction.)
542 func tracebacktrap(pc, sp, lr uintptr, gp *g) {
543 traceback1(pc, sp, lr, gp, _TraceTrap)
546 func traceback1(pc, sp, lr uintptr, gp *g, flags uint) {
548 if readgstatus(gp)&^_Gscan == _Gsyscall {
549 // Override registers if blocked in system call.
554 // Print traceback. By default, omits runtime frames.
555 // If that means we print nothing at all, repeat forcing all frames printed.
556 n = gentraceback(pc, sp, lr, gp, 0, nil, _TracebackMaxFrames, nil, nil, flags)
557 if n == 0 && (flags&_TraceRuntimeFrames) == 0 {
558 n = gentraceback(pc, sp, lr, gp, 0, nil, _TracebackMaxFrames, nil, nil, flags|_TraceRuntimeFrames)
560 if n == _TracebackMaxFrames {
561 print("...additional frames elided...\n")
566 func callers(skip int, pcbuf []uintptr) int {
567 sp := getcallersp(unsafe.Pointer(&skip))
568 pc := uintptr(getcallerpc(unsafe.Pointer(&skip)))
572 n = gentraceback(pc, sp, 0, gp, skip, &pcbuf[0], len(pcbuf), nil, nil, 0)
577 func gcallers(gp *g, skip int, pcbuf []uintptr) int {
578 return gentraceback(^uintptr(0), ^uintptr(0), 0, gp, skip, &pcbuf[0], len(pcbuf), nil, nil, 0)
581 func showframe(f *_func, gp *g) bool {
583 if g.m.throwing > 0 && gp != nil && (gp == g.m.curg || gp == g.m.caughtsig.ptr()) {
586 level, _, _ := gotraceback()
589 // Special case: always show runtime.panic frame, so that we can
590 // see where a panic started in the middle of a stack trace.
591 // See golang.org/issue/5832.
592 if name == "runtime.panic" {
596 return level > 1 || f != nil && contains(name, ".") && (!hasprefix(name, "runtime.") || isExportedRuntime(name))
599 // isExportedRuntime reports whether name is an exported runtime function.
600 // It is only for runtime functions, so ASCII A-Z is fine.
601 func isExportedRuntime(name string) bool {
602 const n = len("runtime.")
603 return len(name) > n && name[:n] == "runtime." && 'A' <= name[n] && name[n] <= 'Z'
606 var gStatusStrings = [...]string{
608 _Grunnable: "runnable",
609 _Grunning: "running",
610 _Gsyscall: "syscall",
611 _Gwaiting: "waiting",
613 _Genqueue: "enqueue",
614 _Gcopystack: "copystack",
617 var gScanStatusStrings = [...]string{
619 _Grunnable: "scanrunnable",
620 _Grunning: "scanrunning",
621 _Gsyscall: "scansyscall",
622 _Gwaiting: "scanwaiting",
624 _Genqueue: "scanenqueue",
627 func goroutineheader(gp *g) {
628 gpstatus := readgstatus(gp)
630 // Basic string status
632 if 0 <= gpstatus && gpstatus < uint32(len(gStatusStrings)) {
633 status = gStatusStrings[gpstatus]
634 } else if gpstatus&_Gscan != 0 && 0 <= gpstatus&^_Gscan && gpstatus&^_Gscan < uint32(len(gStatusStrings)) {
635 status = gStatusStrings[gpstatus&^_Gscan]
641 if (gpstatus == _Gwaiting || gpstatus == _Gscanwaiting) && gp.waitreason != "" {
642 status = gp.waitreason
645 // approx time the G is blocked, in minutes
647 gpstatus &^= _Gscan // drop the scan bit
648 if (gpstatus == _Gwaiting || gpstatus == _Gsyscall) && gp.waitsince != 0 {
649 waitfor = (nanotime() - gp.waitsince) / 60e9
651 print("goroutine ", gp.goid, " [", status)
653 print(", ", waitfor, " minutes")
655 if gp.lockedm != nil {
656 print(", locked to thread")
661 func tracebackothers(me *g) {
662 level, _, _ := gotraceback()
664 // Show the current goroutine first, if we haven't already.
667 if gp != nil && gp != me {
670 traceback(^uintptr(0), ^uintptr(0), 0, gp)
674 for _, gp := range allgs {
675 if gp == me || gp == g.m.curg || readgstatus(gp) == _Gdead || isSystemGoroutine(gp) && level < 2 {
680 // Note: gp.m == g.m occurs when tracebackothers is
681 // called from a signal handler initiated during a
682 // systemstack call. The original G is still in the
683 // running state, and we want to print its stack.
684 if gp.m != g.m && readgstatus(gp)&^_Gscan == _Grunning {
685 print("\tgoroutine running on other thread; stack unavailable\n")
688 traceback(^uintptr(0), ^uintptr(0), 0, gp)
694 // Does f mark the top of a goroutine stack?
695 func topofstack(f *_func) bool {
697 return pc == goexitPC ||
702 externalthreadhandlerp != 0 && pc == externalthreadhandlerp
705 // isSystemGoroutine reports whether the goroutine g must be omitted in
706 // stack dumps and deadlock detector.
707 func isSystemGoroutine(gp *g) bool {
709 return pc == runfinqPC && !fingRunning ||
711 pc == forcegchelperPC ||
713 pc == gcBgMarkWorkerPC