github.com/4ad/go@v0.0.0-20161219182952-69a12818b605/src/runtime/traceback.go (about) 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. 4 5 package runtime 6 7 import ( 8 "runtime/internal/atomic" 9 "runtime/internal/sys" 10 "unsafe" 11 ) 12 13 // The code in this file implements stack trace walking for all architectures. 14 // The most important fact about a given architecture is whether it uses a link register. 15 // On systems with link registers, the prologue for a non-leaf function stores the 16 // incoming value of LR at the bottom of the newly allocated stack frame. 17 // On systems without link registers, the architecture pushes a return PC during 18 // the call instruction, so the return PC ends up above the stack frame. 19 // In this file, the return PC is always called LR, no matter how it was found. 20 // 21 // To date, the opposite of a link register architecture is an x86 architecture. 22 // This code may need to change if some other kind of non-link-register 23 // architecture comes along. 24 // 25 // The other important fact is the size of a pointer: on 32-bit systems the LR 26 // takes up only 4 bytes on the stack, while on 64-bit systems it takes up 8 bytes. 27 // Typically this is ptrSize. 28 // 29 // As an exception, amd64p32 has ptrSize == 4 but the CALL instruction still 30 // stores an 8-byte return PC onto the stack. To accommodate this, we use regSize 31 // as the size of the architecture-pushed return PC. 32 // 33 // usesLR is defined below in terms of minFrameSize, which is defined in 34 // arch_$GOARCH.go. ptrSize and regSize are defined in stubs.go. 35 36 const usesLR = sys.MinFrameSize > 0 37 38 const returnAddrOffset = sys.GoarchSparc64 * 120 39 40 var ( 41 // initialized in tracebackinit 42 goexitPC uintptr 43 jmpdeferPC uintptr 44 mcallPC uintptr 45 morestackPC uintptr 46 mstartPC uintptr 47 rt0_goPC uintptr 48 sigpanicPC uintptr 49 runfinqPC uintptr 50 bgsweepPC uintptr 51 forcegchelperPC uintptr 52 timerprocPC uintptr 53 gcBgMarkWorkerPC uintptr 54 systemstack_switchPC uintptr 55 systemstackPC uintptr 56 stackBarrierPC uintptr 57 cgocallback_gofuncPC uintptr 58 59 gogoPC uintptr 60 61 externalthreadhandlerp uintptr // initialized elsewhere 62 ) 63 64 func tracebackinit() { 65 // Go variable initialization happens late during runtime startup. 66 // Instead of initializing the variables above in the declarations, 67 // schedinit calls this function so that the variables are 68 // initialized and available earlier in the startup sequence. 69 goexitPC = funcPC(goexit) 70 jmpdeferPC = funcPC(jmpdefer) 71 mcallPC = funcPC(mcall) 72 morestackPC = funcPC(morestack) 73 mstartPC = funcPC(mstart) 74 rt0_goPC = funcPC(rt0_go) 75 sigpanicPC = funcPC(sigpanic) 76 runfinqPC = funcPC(runfinq) 77 bgsweepPC = funcPC(bgsweep) 78 forcegchelperPC = funcPC(forcegchelper) 79 timerprocPC = funcPC(timerproc) 80 gcBgMarkWorkerPC = funcPC(gcBgMarkWorker) 81 systemstack_switchPC = funcPC(systemstack_switch) 82 systemstackPC = funcPC(systemstack) 83 stackBarrierPC = funcPC(stackBarrier) 84 cgocallback_gofuncPC = funcPC(cgocallback_gofunc) 85 86 // used by sigprof handler 87 gogoPC = funcPC(gogo) 88 } 89 90 // Traceback over the deferred function calls. 91 // Report them like calls that have been invoked but not started executing yet. 92 func tracebackdefers(gp *g, callback func(*stkframe, unsafe.Pointer) bool, v unsafe.Pointer) { 93 var frame stkframe 94 for d := gp._defer; d != nil; d = d.link { 95 fn := d.fn 96 if fn == nil { 97 // Defer of nil function. Args don't matter. 98 frame.pc = 0 99 frame.fn = nil 100 frame.argp = 0 101 frame.arglen = 0 102 frame.argmap = nil 103 } else { 104 frame.pc = fn.fn 105 f := findfunc(frame.pc) 106 if f == nil { 107 print("runtime: unknown pc in defer ", hex(frame.pc), "\n") 108 throw("unknown pc") 109 } 110 frame.fn = f 111 frame.argp = uintptr(deferArgs(d)) 112 frame.arglen, frame.argmap = getArgInfo(&frame, f, true) 113 } 114 frame.continpc = frame.pc 115 if !callback((*stkframe)(noescape(unsafe.Pointer(&frame))), v) { 116 return 117 } 118 } 119 } 120 121 // Generic traceback. Handles runtime stack prints (pcbuf == nil), 122 // the runtime.Callers function (pcbuf != nil), as well as the garbage 123 // collector (callback != nil). A little clunky to merge these, but avoids 124 // duplicating the code and all its subtlety. 125 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 { 126 if goexitPC == 0 { 127 throw("gentraceback before goexitPC initialization") 128 } 129 g := getg() 130 if g == gp && g == g.m.curg { 131 // The starting sp has been passed in as a uintptr, and the caller may 132 // have other uintptr-typed stack references as well. 133 // If during one of the calls that got us here or during one of the 134 // callbacks below the stack must be grown, all these uintptr references 135 // to the stack will not be updated, and gentraceback will continue 136 // to inspect the old stack memory, which may no longer be valid. 137 // Even if all the variables were updated correctly, it is not clear that 138 // we want to expose a traceback that begins on one stack and ends 139 // on another stack. That could confuse callers quite a bit. 140 // Instead, we require that gentraceback and any other function that 141 // accepts an sp for the current goroutine (typically obtained by 142 // calling getcallersp) must not run on that goroutine's stack but 143 // instead on the g0 stack. 144 throw("gentraceback cannot trace user goroutine on its own stack") 145 } 146 level, _, _ := gotraceback() 147 148 // Fix up returns to the stack barrier by fetching the 149 // original return PC from gp.stkbar. 150 stkbarG := gp 151 stkbar := stkbarG.stkbar[stkbarG.stkbarPos:] 152 153 if pc0 == ^uintptr(0) && sp0 == ^uintptr(0) { // Signal to fetch saved values from gp. 154 if gp.syscallsp != 0 { 155 pc0 = gp.syscallpc 156 sp0 = gp.syscallsp 157 if usesLR { 158 lr0 = 0 159 } 160 } else { 161 pc0 = gp.sched.pc 162 sp0 = gp.sched.sp 163 if usesLR { 164 lr0 = gp.sched.lr 165 } 166 } 167 } 168 169 nprint := 0 170 var frame stkframe 171 frame.pc = pc0 172 frame.sp = sp0 173 if usesLR { 174 frame.lr = lr0 175 } 176 waspanic := false 177 cgoCtxt := gp.cgoCtxt 178 printing := pcbuf == nil && callback == nil 179 _defer := gp._defer 180 181 for _defer != nil && _defer.sp == _NoArgs { 182 _defer = _defer.link 183 } 184 185 // If the PC is zero, it's likely a nil function call. 186 // Start in the caller's frame. 187 if frame.pc == 0 { 188 if usesLR { 189 frame.pc = *(*uintptr)(unsafe.Pointer(frame.sp + returnAddrOffset)) 190 frame.lr = 0 191 } else { 192 frame.pc = uintptr(*(*sys.Uintreg)(unsafe.Pointer(frame.sp))) 193 frame.sp += sys.RegSize 194 } 195 } 196 197 f := findfunc(frame.pc) 198 if f != nil && f.entry == stackBarrierPC { 199 // We got caught in the middle of a stack barrier 200 // (presumably by a signal), so stkbar may be 201 // inconsistent with the barriers on the stack. 202 // Simulate the completion of the barrier. 203 // 204 // On x86, SP will be exactly one word above 205 // savedLRPtr. On LR machines, SP will be above 206 // savedLRPtr by some frame size. 207 var stkbarPos uintptr 208 if len(stkbar) > 0 && stkbar[0].savedLRPtr < sp0 { 209 // stackBarrier has not incremented stkbarPos. 210 stkbarPos = gp.stkbarPos 211 } else if gp.stkbarPos > 0 && gp.stkbar[gp.stkbarPos-1].savedLRPtr < sp0 { 212 // stackBarrier has incremented stkbarPos. 213 stkbarPos = gp.stkbarPos - 1 214 } else { 215 printlock() 216 print("runtime: failed to unwind through stackBarrier at SP ", hex(sp0), "; ") 217 gcPrintStkbars(gp, int(gp.stkbarPos)) 218 print("\n") 219 throw("inconsistent state in stackBarrier") 220 } 221 222 frame.pc = gp.stkbar[stkbarPos].savedLRVal 223 stkbar = gp.stkbar[stkbarPos+1:] 224 f = findfunc(frame.pc) 225 } 226 if f == nil { 227 if callback != nil { 228 print("runtime: unknown pc ", hex(frame.pc), "\n") 229 throw("unknown pc") 230 } 231 return 0 232 } 233 frame.fn = f 234 235 var cache pcvalueCache 236 237 n := 0 238 for n < max { 239 // Typically: 240 // pc is the PC of the running function. 241 // sp is the stack pointer at that program counter. 242 // fp is the frame pointer (caller's stack pointer) at that program counter, or nil if unknown. 243 // stk is the stack containing sp. 244 // The caller's program counter is lr, unless lr is zero, in which case it is *(uintptr*)sp. 245 f = frame.fn 246 if f.pcsp == 0 { 247 // No frame information, must be external function, like race support. 248 // See golang.org/issue/13568. 249 break 250 } 251 252 // Found an actual function. 253 // Derive frame pointer and link register. 254 if frame.fp == 0 { 255 // We want to jump over the systemstack switch. If we're running on the 256 // g0, this systemstack is at the top of the stack. 257 // if we're not on g0 or there's a no curg, then this is a regular call. 258 sp := frame.sp 259 if flags&_TraceJumpStack != 0 && f.entry == systemstackPC && gp == g.m.g0 && gp.m.curg != nil { 260 sp = gp.m.curg.sched.sp 261 frame.sp = sp 262 stkbarG = gp.m.curg 263 stkbar = stkbarG.stkbar[stkbarG.stkbarPos:] 264 cgoCtxt = gp.m.curg.cgoCtxt 265 } 266 frame.fp = sp + uintptr(funcspdelta(f, frame.pc, &cache)) 267 if !usesLR { 268 // On x86, call instruction pushes return PC before entering new function. 269 frame.fp += sys.RegSize 270 } 271 } 272 var flr *_func 273 if topofstack(f) { 274 frame.lr = 0 275 flr = nil 276 } else if usesLR && f.entry == jmpdeferPC { 277 // jmpdefer modifies SP/LR/PC non-atomically. 278 // If a profiling interrupt arrives during jmpdefer, 279 // the stack unwind may see a mismatched register set 280 // and get confused. Stop if we see PC within jmpdefer 281 // to avoid that confusion. 282 // See golang.org/issue/8153. 283 if callback != nil { 284 throw("traceback_arm: found jmpdefer when tracing with callback") 285 } 286 frame.lr = 0 287 } else { 288 var lrPtr uintptr 289 if usesLR { 290 if n == 0 && frame.sp < frame.fp || frame.lr == 0 { 291 lrPtr = frame.sp + returnAddrOffset 292 frame.lr = *(*uintptr)(unsafe.Pointer(lrPtr)) 293 } 294 } else { 295 if frame.lr == 0 { 296 lrPtr = frame.fp - sys.RegSize 297 frame.lr = uintptr(*(*sys.Uintreg)(unsafe.Pointer(lrPtr))) 298 } 299 } 300 if frame.lr == stackBarrierPC { 301 // Recover original PC. 302 if len(stkbar) == 0 || stkbar[0].savedLRPtr != lrPtr { 303 print("found next stack barrier at ", hex(lrPtr), "; expected ") 304 gcPrintStkbars(stkbarG, len(stkbarG.stkbar)-len(stkbar)) 305 print("\n") 306 throw("missed stack barrier") 307 } 308 frame.lr = stkbar[0].savedLRVal 309 stkbar = stkbar[1:] 310 } 311 flr = findfunc(frame.lr) 312 if flr == nil { 313 // This happens if you get a profiling interrupt at just the wrong time. 314 // In that context it is okay to stop early. 315 // But if callback is set, we're doing a garbage collection and must 316 // get everything, so crash loudly. 317 if callback != nil { 318 print("runtime: unexpected return pc for ", funcname(f), " called from ", hex(frame.lr), "\n") 319 throw("unknown caller pc") 320 } 321 } 322 } 323 324 frame.varp = frame.fp 325 if !usesLR { 326 // On x86, call instruction pushes return PC before entering new function. 327 frame.varp -= sys.RegSize 328 } 329 330 // If framepointer_enabled and there's a frame, then 331 // there's a saved bp here. 332 if framepointer_enabled && GOARCH == "amd64" && frame.varp > frame.sp { 333 frame.varp -= sys.RegSize 334 } 335 336 // Derive size of arguments. 337 // Most functions have a fixed-size argument block, 338 // so we can use metadata about the function f. 339 // Not all, though: there are some variadic functions 340 // in package runtime and reflect, and for those we use call-specific 341 // metadata recorded by f's caller. 342 if callback != nil || printing { 343 frame.argp = frame.fp + sys.MinFrameSize 344 frame.arglen, frame.argmap = getArgInfo(&frame, f, callback != nil) 345 } 346 347 // Determine frame's 'continuation PC', where it can continue. 348 // Normally this is the return address on the stack, but if sigpanic 349 // is immediately below this function on the stack, then the frame 350 // stopped executing due to a trap, and frame.pc is probably not 351 // a safe point for looking up liveness information. In this panicking case, 352 // the function either doesn't return at all (if it has no defers or if the 353 // defers do not recover) or it returns from one of the calls to 354 // deferproc a second time (if the corresponding deferred func recovers). 355 // It suffices to assume that the most recent deferproc is the one that 356 // returns; everything live at earlier deferprocs is still live at that one. 357 frame.continpc = frame.pc 358 if waspanic { 359 if _defer != nil && _defer.sp == frame.sp { 360 frame.continpc = _defer.pc 361 } else { 362 frame.continpc = 0 363 } 364 } 365 366 // Unwind our local defer stack past this frame. 367 for _defer != nil && (_defer.sp == frame.sp || _defer.sp == _NoArgs) { 368 _defer = _defer.link 369 } 370 371 if skip > 0 { 372 skip-- 373 goto skipped 374 } 375 376 if pcbuf != nil { 377 (*[1 << 20]uintptr)(unsafe.Pointer(pcbuf))[n] = frame.pc 378 } 379 if callback != nil { 380 if !callback((*stkframe)(noescape(unsafe.Pointer(&frame))), v) { 381 return n 382 } 383 } 384 if printing { 385 if (flags&_TraceRuntimeFrames) != 0 || showframe(f, gp) { 386 // Print during crash. 387 // main(0x1, 0x2, 0x3) 388 // /home/rsc/go/src/runtime/x.go:23 +0xf 389 // 390 tracepc := frame.pc // back up to CALL instruction for funcline. 391 // SPARC64's PC holds the address of the *current* 392 // instruction, so it doesn't need this. 393 if (n > 0 || flags&_TraceTrap == 0) && frame.pc > f.entry && !waspanic && sys.GoarchSparc64 == 0 { 394 tracepc-- 395 } 396 name := funcname(f) 397 if name == "runtime.gopanic" { 398 name = "panic" 399 } 400 print(name, "(") 401 argp := (*[100]uintptr)(unsafe.Pointer(frame.argp)) 402 for i := uintptr(0); i < frame.arglen/sys.PtrSize; i++ { 403 if i >= 10 { 404 print(", ...") 405 break 406 } 407 if i != 0 { 408 print(", ") 409 } 410 print(hex(argp[i])) 411 } 412 print(")\n") 413 file, line := funcline(f, tracepc) 414 print("\t", file, ":", line) 415 if frame.pc > f.entry { 416 print(" +", hex(frame.pc-f.entry)) 417 } 418 if g.m.throwing > 0 && gp == g.m.curg || level >= 2 { 419 print(" fp=", hex(frame.fp), " sp=", hex(frame.sp)) 420 } 421 print("\n") 422 nprint++ 423 } 424 } 425 n++ 426 427 skipped: 428 if f.entry == cgocallback_gofuncPC && len(cgoCtxt) > 0 { 429 ctxt := cgoCtxt[len(cgoCtxt)-1] 430 cgoCtxt = cgoCtxt[:len(cgoCtxt)-1] 431 432 // skip only applies to Go frames. 433 // callback != nil only used when we only care 434 // about Go frames. 435 if skip == 0 && callback == nil { 436 n = tracebackCgoContext(pcbuf, printing, ctxt, n, max) 437 } 438 } 439 440 waspanic = f.entry == sigpanicPC 441 442 // Do not unwind past the bottom of the stack. 443 if flr == nil { 444 break 445 } 446 447 // Unwind to next frame. 448 frame.fn = flr 449 frame.pc = frame.lr 450 frame.lr = 0 451 frame.sp = frame.fp 452 frame.fp = 0 453 frame.argmap = nil 454 455 // On link register architectures, sighandler saves the LR on stack 456 // before faking a call to sigpanic. 457 if usesLR && waspanic { 458 x := *(*uintptr)(unsafe.Pointer(frame.sp + returnAddrOffset)) 459 frame.sp += sys.MinFrameSize 460 if GOARCH == "arm64" { 461 // arm64 needs 16-byte aligned SP, always 462 frame.sp += sys.PtrSize 463 } 464 f = findfunc(frame.pc) 465 frame.fn = f 466 if f == nil { 467 frame.pc = x 468 } else if funcspdelta(f, frame.pc, &cache) == 0 { 469 frame.lr = x 470 } 471 } 472 } 473 474 if printing { 475 n = nprint 476 } 477 478 // If callback != nil, we're being called to gather stack information during 479 // garbage collection or stack growth. In that context, require that we used 480 // up the entire defer stack. If not, then there is a bug somewhere and the 481 // garbage collection or stack growth may not have seen the correct picture 482 // of the stack. Crash now instead of silently executing the garbage collection 483 // or stack copy incorrectly and setting up for a mysterious crash later. 484 // 485 // Note that panic != nil is okay here: there can be leftover panics, 486 // because the defers on the panic stack do not nest in frame order as 487 // they do on the defer stack. If you have: 488 // 489 // frame 1 defers d1 490 // frame 2 defers d2 491 // frame 3 defers d3 492 // frame 4 panics 493 // frame 4's panic starts running defers 494 // frame 5, running d3, defers d4 495 // frame 5 panics 496 // frame 5's panic starts running defers 497 // frame 6, running d4, garbage collects 498 // frame 6, running d2, garbage collects 499 // 500 // During the execution of d4, the panic stack is d4 -> d3, which 501 // is nested properly, and we'll treat frame 3 as resumable, because we 502 // can find d3. (And in fact frame 3 is resumable. If d4 recovers 503 // and frame 5 continues running, d3, d3 can recover and we'll 504 // resume execution in (returning from) frame 3.) 505 // 506 // During the execution of d2, however, the panic stack is d2 -> d3, 507 // which is inverted. The scan will match d2 to frame 2 but having 508 // d2 on the stack until then means it will not match d3 to frame 3. 509 // This is okay: if we're running d2, then all the defers after d2 have 510 // completed and their corresponding frames are dead. Not finding d3 511 // for frame 3 means we'll set frame 3's continpc == 0, which is correct 512 // (frame 3 is dead). At the end of the walk the panic stack can thus 513 // contain defers (d3 in this case) for dead frames. The inversion here 514 // always indicates a dead frame, and the effect of the inversion on the 515 // scan is to hide those dead frames, so the scan is still okay: 516 // what's left on the panic stack are exactly (and only) the dead frames. 517 // 518 // We require callback != nil here because only when callback != nil 519 // do we know that gentraceback is being called in a "must be correct" 520 // context as opposed to a "best effort" context. The tracebacks with 521 // callbacks only happen when everything is stopped nicely. 522 // At other times, such as when gathering a stack for a profiling signal 523 // or when printing a traceback during a crash, everything may not be 524 // stopped nicely, and the stack walk may not be able to complete. 525 // It's okay in those situations not to use up the entire defer stack: 526 // incomplete information then is still better than nothing. 527 if callback != nil && n < max && _defer != nil { 528 if _defer != nil { 529 print("runtime: g", gp.goid, ": leftover defer sp=", hex(_defer.sp), " pc=", hex(_defer.pc), "\n") 530 } 531 for _defer = gp._defer; _defer != nil; _defer = _defer.link { 532 print("\tdefer ", _defer, " sp=", hex(_defer.sp), " pc=", hex(_defer.pc), "\n") 533 } 534 throw("traceback has leftover defers") 535 } 536 537 if callback != nil && n < max && len(stkbar) > 0 { 538 print("runtime: g", gp.goid, ": leftover stack barriers ") 539 gcPrintStkbars(stkbarG, len(stkbarG.stkbar)-len(stkbar)) 540 print("\n") 541 throw("traceback has leftover stack barriers") 542 } 543 544 if callback != nil && n < max && frame.sp != gp.stktopsp { 545 print("runtime: g", gp.goid, ": frame.sp=", hex(frame.sp), " top=", hex(gp.stktopsp), "\n") 546 print("\tstack=[", hex(gp.stack.lo), "-", hex(gp.stack.hi), "] n=", n, " max=", max, "\n") 547 throw("traceback did not unwind completely") 548 } 549 550 return n 551 } 552 553 func getArgInfo(frame *stkframe, f *_func, needArgMap bool) (arglen uintptr, argmap *bitvector) { 554 arglen = uintptr(f.args) 555 if needArgMap && f.args == _ArgsSizeUnknown { 556 // Extract argument bitmaps for reflect stubs from the calls they made to reflect. 557 switch funcname(f) { 558 case "reflect.makeFuncStub", "reflect.methodValueCall": 559 arg0 := frame.sp + sys.MinFrameSize 560 fn := *(**[2]uintptr)(unsafe.Pointer(arg0)) 561 if fn[0] != f.entry { 562 print("runtime: confused by ", funcname(f), "\n") 563 throw("reflect mismatch") 564 } 565 bv := (*bitvector)(unsafe.Pointer(fn[1])) 566 arglen = uintptr(bv.n * sys.PtrSize) 567 argmap = bv 568 } 569 } 570 return 571 } 572 573 // tracebackCgoContext handles tracing back a cgo context value, from 574 // the context argument to setCgoTraceback, for the gentraceback 575 // function. It returns the new value of n. 576 func tracebackCgoContext(pcbuf *uintptr, printing bool, ctxt uintptr, n, max int) int { 577 var cgoPCs [32]uintptr 578 cgoContextPCs(ctxt, cgoPCs[:]) 579 var arg cgoSymbolizerArg 580 anySymbolized := false 581 for _, pc := range cgoPCs { 582 if pc == 0 || n >= max { 583 break 584 } 585 if pcbuf != nil { 586 (*[1 << 20]uintptr)(unsafe.Pointer(pcbuf))[n] = pc 587 } 588 if printing { 589 if cgoSymbolizer == nil { 590 print("non-Go function at pc=", hex(pc), "\n") 591 } else { 592 c := printOneCgoTraceback(pc, max-n, &arg) 593 n += c - 1 // +1 a few lines down 594 anySymbolized = true 595 } 596 } 597 n++ 598 } 599 if anySymbolized { 600 arg.pc = 0 601 callCgoSymbolizer(&arg) 602 } 603 return n 604 } 605 606 func printcreatedby(gp *g) { 607 // Show what created goroutine, except main goroutine (goid 1). 608 pc := gp.gopc 609 f := findfunc(pc) 610 if f != nil && showframe(f, gp) && gp.goid != 1 { 611 print("created by ", funcname(f), "\n") 612 tracepc := pc // back up to CALL instruction for funcline. 613 // SPARC64's PC holds the address of the *current* 614 // instruction, so it doesn't need this. 615 if pc > f.entry && sys.GoarchSparc64 == 0 { 616 tracepc -= sys.PCQuantum 617 } 618 file, line := funcline(f, tracepc) 619 print("\t", file, ":", line) 620 if pc > f.entry { 621 print(" +", hex(pc-f.entry)) 622 } 623 print("\n") 624 } 625 } 626 627 func traceback(pc, sp, lr uintptr, gp *g) { 628 traceback1(pc, sp, lr, gp, 0) 629 } 630 631 // tracebacktrap is like traceback but expects that the PC and SP were obtained 632 // from a trap, not from gp->sched or gp->syscallpc/gp->syscallsp or getcallerpc/getcallersp. 633 // Because they are from a trap instead of from a saved pair, 634 // the initial PC must not be rewound to the previous instruction. 635 // (All the saved pairs record a PC that is a return address, so we 636 // rewind it into the CALL instruction.) 637 func tracebacktrap(pc, sp, lr uintptr, gp *g) { 638 traceback1(pc, sp, lr, gp, _TraceTrap) 639 } 640 641 func traceback1(pc, sp, lr uintptr, gp *g, flags uint) { 642 // If the goroutine is in cgo, and we have a cgo traceback, print that. 643 if iscgo && gp.m != nil && gp.m.ncgo > 0 && gp.syscallsp != 0 && gp.m.cgoCallers != nil && gp.m.cgoCallers[0] != 0 { 644 // Lock cgoCallers so that a signal handler won't 645 // change it, copy the array, reset it, unlock it. 646 // We are locked to the thread and are not running 647 // concurrently with a signal handler. 648 // We just have to stop a signal handler from interrupting 649 // in the middle of our copy. 650 atomic.Store(&gp.m.cgoCallersUse, 1) 651 cgoCallers := *gp.m.cgoCallers 652 gp.m.cgoCallers[0] = 0 653 atomic.Store(&gp.m.cgoCallersUse, 0) 654 655 printCgoTraceback(&cgoCallers) 656 } 657 658 var n int 659 if readgstatus(gp)&^_Gscan == _Gsyscall { 660 // Override registers if blocked in system call. 661 pc = gp.syscallpc 662 sp = gp.syscallsp 663 flags &^= _TraceTrap 664 } 665 // Print traceback. By default, omits runtime frames. 666 // If that means we print nothing at all, repeat forcing all frames printed. 667 n = gentraceback(pc, sp, lr, gp, 0, nil, _TracebackMaxFrames, nil, nil, flags) 668 if n == 0 && (flags&_TraceRuntimeFrames) == 0 { 669 n = gentraceback(pc, sp, lr, gp, 0, nil, _TracebackMaxFrames, nil, nil, flags|_TraceRuntimeFrames) 670 } 671 if n == _TracebackMaxFrames { 672 print("...additional frames elided...\n") 673 } 674 printcreatedby(gp) 675 } 676 677 func callers(skip int, pcbuf []uintptr) int { 678 sp := getcallersp(unsafe.Pointer(&skip)) 679 pc := getcallerpc(unsafe.Pointer(&skip)) 680 gp := getg() 681 var n int 682 systemstack(func() { 683 n = gentraceback(pc, sp, 0, gp, skip, &pcbuf[0], len(pcbuf), nil, nil, 0) 684 }) 685 return n 686 } 687 688 func gcallers(gp *g, skip int, pcbuf []uintptr) int { 689 return gentraceback(^uintptr(0), ^uintptr(0), 0, gp, skip, &pcbuf[0], len(pcbuf), nil, nil, 0) 690 } 691 692 func showframe(f *_func, gp *g) bool { 693 g := getg() 694 if g.m.throwing > 0 && gp != nil && (gp == g.m.curg || gp == g.m.caughtsig.ptr()) { 695 return true 696 } 697 level, _, _ := gotraceback() 698 name := funcname(f) 699 700 // Special case: always show runtime.gopanic frame, so that we can 701 // see where a panic started in the middle of a stack trace. 702 // See golang.org/issue/5832. 703 if name == "runtime.gopanic" { 704 return true 705 } 706 707 return level > 1 || f != nil && contains(name, ".") && (!hasprefix(name, "runtime.") || isExportedRuntime(name)) 708 } 709 710 // isExportedRuntime reports whether name is an exported runtime function. 711 // It is only for runtime functions, so ASCII A-Z is fine. 712 func isExportedRuntime(name string) bool { 713 const n = len("runtime.") 714 return len(name) > n && name[:n] == "runtime." && 'A' <= name[n] && name[n] <= 'Z' 715 } 716 717 var gStatusStrings = [...]string{ 718 _Gidle: "idle", 719 _Grunnable: "runnable", 720 _Grunning: "running", 721 _Gsyscall: "syscall", 722 _Gwaiting: "waiting", 723 _Gdead: "dead", 724 _Gcopystack: "copystack", 725 } 726 727 func goroutineheader(gp *g) { 728 gpstatus := readgstatus(gp) 729 730 isScan := gpstatus&_Gscan != 0 731 gpstatus &^= _Gscan // drop the scan bit 732 733 // Basic string status 734 var status string 735 if 0 <= gpstatus && gpstatus < uint32(len(gStatusStrings)) { 736 status = gStatusStrings[gpstatus] 737 } else { 738 status = "???" 739 } 740 741 // Override. 742 if gpstatus == _Gwaiting && gp.waitreason != "" { 743 status = gp.waitreason 744 } 745 746 // approx time the G is blocked, in minutes 747 var waitfor int64 748 if (gpstatus == _Gwaiting || gpstatus == _Gsyscall) && gp.waitsince != 0 { 749 waitfor = (nanotime() - gp.waitsince) / 60e9 750 } 751 print("goroutine ", gp.goid, " [", status) 752 if isScan { 753 print(" (scan)") 754 } 755 if waitfor >= 1 { 756 print(", ", waitfor, " minutes") 757 } 758 if gp.lockedm != nil { 759 print(", locked to thread") 760 } 761 print("]:\n") 762 } 763 764 func tracebackothers(me *g) { 765 level, _, _ := gotraceback() 766 767 // Show the current goroutine first, if we haven't already. 768 g := getg() 769 gp := g.m.curg 770 if gp != nil && gp != me { 771 print("\n") 772 goroutineheader(gp) 773 traceback(^uintptr(0), ^uintptr(0), 0, gp) 774 } 775 776 lock(&allglock) 777 for _, gp := range allgs { 778 if gp == me || gp == g.m.curg || readgstatus(gp) == _Gdead || isSystemGoroutine(gp) && level < 2 { 779 continue 780 } 781 print("\n") 782 goroutineheader(gp) 783 // Note: gp.m == g.m occurs when tracebackothers is 784 // called from a signal handler initiated during a 785 // systemstack call. The original G is still in the 786 // running state, and we want to print its stack. 787 if gp.m != g.m && readgstatus(gp)&^_Gscan == _Grunning { 788 print("\tgoroutine running on other thread; stack unavailable\n") 789 printcreatedby(gp) 790 } else { 791 traceback(^uintptr(0), ^uintptr(0), 0, gp) 792 } 793 } 794 unlock(&allglock) 795 } 796 797 // Does f mark the top of a goroutine stack? 798 func topofstack(f *_func) bool { 799 pc := f.entry 800 return pc == goexitPC || 801 pc == mstartPC || 802 pc == mcallPC || 803 pc == morestackPC || 804 pc == rt0_goPC || 805 externalthreadhandlerp != 0 && pc == externalthreadhandlerp 806 } 807 808 // isSystemGoroutine reports whether the goroutine g must be omitted in 809 // stack dumps and deadlock detector. 810 func isSystemGoroutine(gp *g) bool { 811 pc := gp.startpc 812 return pc == runfinqPC && !fingRunning || 813 pc == bgsweepPC || 814 pc == forcegchelperPC || 815 pc == timerprocPC || 816 pc == gcBgMarkWorkerPC 817 } 818 819 // SetCgoTraceback records three C functions to use to gather 820 // traceback information from C code and to convert that traceback 821 // information into symbolic information. These are used when printing 822 // stack traces for a program that uses cgo. 823 // 824 // The traceback and context functions may be called from a signal 825 // handler, and must therefore use only async-signal safe functions. 826 // The symbolizer function may be called while the program is 827 // crashing, and so must be cautious about using memory. None of the 828 // functions may call back into Go. 829 // 830 // The context function will be called with a single argument, a 831 // pointer to a struct: 832 // 833 // struct { 834 // Context uintptr 835 // } 836 // 837 // In C syntax, this struct will be 838 // 839 // struct { 840 // uintptr_t Context; 841 // }; 842 // 843 // If the Context field is 0, the context function is being called to 844 // record the current traceback context. It should record in the 845 // Context field whatever information is needed about the current 846 // point of execution to later produce a stack trace, probably the 847 // stack pointer and PC. In this case the context function will be 848 // called from C code. 849 // 850 // If the Context field is not 0, then it is a value returned by a 851 // previous call to the context function. This case is called when the 852 // context is no longer needed; that is, when the Go code is returning 853 // to its C code caller. This permits the context function to release 854 // any associated resources. 855 // 856 // While it would be correct for the context function to record a 857 // complete a stack trace whenever it is called, and simply copy that 858 // out in the traceback function, in a typical program the context 859 // function will be called many times without ever recording a 860 // traceback for that context. Recording a complete stack trace in a 861 // call to the context function is likely to be inefficient. 862 // 863 // The traceback function will be called with a single argument, a 864 // pointer to a struct: 865 // 866 // struct { 867 // Context uintptr 868 // SigContext uintptr 869 // Buf *uintptr 870 // Max uintptr 871 // } 872 // 873 // In C syntax, this struct will be 874 // 875 // struct { 876 // uintptr_t Context; 877 // uintptr_t SigContext; 878 // uintptr_t* Buf; 879 // uintptr_t Max; 880 // }; 881 // 882 // The Context field will be zero to gather a traceback from the 883 // current program execution point. In this case, the traceback 884 // function will be called from C code. 885 // 886 // Otherwise Context will be a value previously returned by a call to 887 // the context function. The traceback function should gather a stack 888 // trace from that saved point in the program execution. The traceback 889 // function may be called from an execution thread other than the one 890 // that recorded the context, but only when the context is known to be 891 // valid and unchanging. The traceback function may also be called 892 // deeper in the call stack on the same thread that recorded the 893 // context. The traceback function may be called multiple times with 894 // the same Context value; it will usually be appropriate to cache the 895 // result, if possible, the first time this is called for a specific 896 // context value. 897 // 898 // If the traceback function is called from a signal handler on a Unix 899 // system, SigContext will be the signal context argument passed to 900 // the signal handler (a C ucontext_t* cast to uintptr_t). This may be 901 // used to start tracing at the point where the signal occurred. If 902 // the traceback function is not called from a signal handler, 903 // SigContext will be zero. 904 // 905 // Buf is where the traceback information should be stored. It should 906 // be PC values, such that Buf[0] is the PC of the caller, Buf[1] is 907 // the PC of that function's caller, and so on. Max is the maximum 908 // number of entries to store. The function should store a zero to 909 // indicate the top of the stack, or that the caller is on a different 910 // stack, presumably a Go stack. 911 // 912 // Unlike runtime.Callers, the PC values returned should, when passed 913 // to the symbolizer function, return the file/line of the call 914 // instruction. No additional subtraction is required or appropriate. 915 // 916 // The symbolizer function will be called with a single argument, a 917 // pointer to a struct: 918 // 919 // struct { 920 // PC uintptr // program counter to fetch information for 921 // File *byte // file name (NUL terminated) 922 // Lineno uintptr // line number 923 // Func *byte // function name (NUL terminated) 924 // Entry uintptr // function entry point 925 // More uintptr // set non-zero if more info for this PC 926 // Data uintptr // unused by runtime, available for function 927 // } 928 // 929 // In C syntax, this struct will be 930 // 931 // struct { 932 // uintptr_t PC; 933 // char* File; 934 // uintptr_t Lineno; 935 // char* Func; 936 // uintptr_t Entry; 937 // uintptr_t More; 938 // uintptr_t Data; 939 // }; 940 // 941 // The PC field will be a value returned by a call to the traceback 942 // function. 943 // 944 // The first time the function is called for a particular traceback, 945 // all the fields except PC will be 0. The function should fill in the 946 // other fields if possible, setting them to 0/nil if the information 947 // is not available. The Data field may be used to store any useful 948 // information across calls. The More field should be set to non-zero 949 // if there is more information for this PC, zero otherwise. If More 950 // is set non-zero, the function will be called again with the same 951 // PC, and may return different information (this is intended for use 952 // with inlined functions). If More is zero, the function will be 953 // called with the next PC value in the traceback. When the traceback 954 // is complete, the function will be called once more with PC set to 955 // zero; this may be used to free any information. Each call will 956 // leave the fields of the struct set to the same values they had upon 957 // return, except for the PC field when the More field is zero. The 958 // function must not keep a copy of the struct pointer between calls. 959 // 960 // When calling SetCgoTraceback, the version argument is the version 961 // number of the structs that the functions expect to receive. 962 // Currently this must be zero. 963 // 964 // The symbolizer function may be nil, in which case the results of 965 // the traceback function will be displayed as numbers. If the 966 // traceback function is nil, the symbolizer function will never be 967 // called. The context function may be nil, in which case the 968 // traceback function will only be called with the context field set 969 // to zero. If the context function is nil, then calls from Go to C 970 // to Go will not show a traceback for the C portion of the call stack. 971 // 972 // SetCgoTraceback should be called only once, ideally from an init function. 973 func SetCgoTraceback(version int, traceback, context, symbolizer unsafe.Pointer) { 974 if version != 0 { 975 panic("unsupported version") 976 } 977 978 if cgoTraceback != nil && cgoTraceback != traceback || 979 cgoContext != nil && cgoContext != context || 980 cgoSymbolizer != nil && cgoSymbolizer != symbolizer { 981 panic("call SetCgoTraceback only once") 982 } 983 984 cgoTraceback = traceback 985 cgoContext = context 986 cgoSymbolizer = symbolizer 987 988 // The context function is called when a C function calls a Go 989 // function. As such it is only called by C code in runtime/cgo. 990 if _cgo_set_context_function != nil { 991 cgocall(_cgo_set_context_function, context) 992 } 993 } 994 995 var cgoTraceback unsafe.Pointer 996 var cgoContext unsafe.Pointer 997 var cgoSymbolizer unsafe.Pointer 998 999 // cgoTracebackArg is the type passed to cgoTraceback. 1000 type cgoTracebackArg struct { 1001 context uintptr 1002 sigContext uintptr 1003 buf *uintptr 1004 max uintptr 1005 } 1006 1007 // cgoContextArg is the type passed to the context function. 1008 type cgoContextArg struct { 1009 context uintptr 1010 } 1011 1012 // cgoSymbolizerArg is the type passed to cgoSymbolizer. 1013 type cgoSymbolizerArg struct { 1014 pc uintptr 1015 file *byte 1016 lineno uintptr 1017 funcName *byte 1018 entry uintptr 1019 more uintptr 1020 data uintptr 1021 } 1022 1023 // cgoTraceback prints a traceback of callers. 1024 func printCgoTraceback(callers *cgoCallers) { 1025 if cgoSymbolizer == nil { 1026 for _, c := range callers { 1027 if c == 0 { 1028 break 1029 } 1030 print("non-Go function at pc=", hex(c), "\n") 1031 } 1032 return 1033 } 1034 1035 var arg cgoSymbolizerArg 1036 for _, c := range callers { 1037 if c == 0 { 1038 break 1039 } 1040 printOneCgoTraceback(c, 0x7fffffff, &arg) 1041 } 1042 arg.pc = 0 1043 callCgoSymbolizer(&arg) 1044 } 1045 1046 // printOneCgoTraceback prints the traceback of a single cgo caller. 1047 // This can print more than one line because of inlining. 1048 // Returns the number of frames printed. 1049 func printOneCgoTraceback(pc uintptr, max int, arg *cgoSymbolizerArg) int { 1050 c := 0 1051 arg.pc = pc 1052 for { 1053 if c > max { 1054 break 1055 } 1056 callCgoSymbolizer(arg) 1057 if arg.funcName != nil { 1058 // Note that we don't print any argument 1059 // information here, not even parentheses. 1060 // The symbolizer must add that if appropriate. 1061 println(gostringnocopy(arg.funcName)) 1062 } else { 1063 println("non-Go function") 1064 } 1065 print("\t") 1066 if arg.file != nil { 1067 print(gostringnocopy(arg.file), ":", arg.lineno, " ") 1068 } 1069 print("pc=", hex(pc), "\n") 1070 c++ 1071 if arg.more == 0 { 1072 break 1073 } 1074 } 1075 return c 1076 } 1077 1078 // callCgoSymbolizer calls the cgoSymbolizer function. 1079 func callCgoSymbolizer(arg *cgoSymbolizerArg) { 1080 call := cgocall 1081 if panicking > 0 || getg().m.curg != getg() { 1082 // We do not want to call into the scheduler when panicking 1083 // or when on the system stack. 1084 call = asmcgocall 1085 } 1086 call(cgoSymbolizer, noescape(unsafe.Pointer(arg))) 1087 } 1088 1089 // cgoContextPCs gets the PC values from a cgo traceback. 1090 func cgoContextPCs(ctxt uintptr, buf []uintptr) { 1091 if cgoTraceback == nil { 1092 return 1093 } 1094 call := cgocall 1095 if panicking > 0 || getg().m.curg != getg() { 1096 // We do not want to call into the scheduler when panicking 1097 // or when on the system stack. 1098 call = asmcgocall 1099 } 1100 arg := cgoTracebackArg{ 1101 context: ctxt, 1102 buf: (*uintptr)(noescape(unsafe.Pointer(&buf[0]))), 1103 max: uintptr(len(buf)), 1104 } 1105 call(cgoTraceback, noescape(unsafe.Pointer(&arg))) 1106 }