Source file src/runtime/traceback.go
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 "internal/abi" 9 "internal/bytealg" 10 "internal/goarch" 11 "internal/runtime/pprof/label" 12 "internal/runtime/sys" 13 "internal/stringslite" 14 "unsafe" 15 ) 16 17 // The code in this file implements stack trace walking for all architectures. 18 // The most important fact about a given architecture is whether it uses a link register. 19 // On systems with link registers, the prologue for a non-leaf function stores the 20 // incoming value of LR at the bottom of the newly allocated stack frame. 21 // On systems without link registers (x86), the architecture pushes a return PC during 22 // the call instruction, so the return PC ends up above the stack frame. 23 // In this file, the return PC is always called LR, no matter how it was found. 24 25 const usesLR = sys.MinFrameSize > 0 26 27 const ( 28 // tracebackInnerFrames is the number of innermost frames to print in a 29 // stack trace. The total maximum frames is tracebackInnerFrames + 30 // tracebackOuterFrames. 31 tracebackInnerFrames = 50 32 33 // tracebackOuterFrames is the number of outermost frames to print in a 34 // stack trace. 35 tracebackOuterFrames = 50 36 ) 37 38 // unwindFlags control the behavior of various unwinders. 39 type unwindFlags uint8 40 41 const ( 42 // unwindPrintErrors indicates that if unwinding encounters an error, it 43 // should print a message and stop without throwing. This is used for things 44 // like stack printing, where it's better to get incomplete information than 45 // to crash. This is also used in situations where everything may not be 46 // stopped nicely and the stack walk may not be able to complete, such as 47 // during profiling signals or during a crash. 48 // 49 // If neither unwindPrintErrors or unwindSilentErrors are set, unwinding 50 // performs extra consistency checks and throws on any error. 51 // 52 // Note that there are a small number of fatal situations that will throw 53 // regardless of unwindPrintErrors or unwindSilentErrors. 54 unwindPrintErrors unwindFlags = 1 << iota 55 56 // unwindSilentErrors silently ignores errors during unwinding. 57 unwindSilentErrors 58 59 // unwindTrap indicates that the initial PC and SP are from a trap, not a 60 // return PC from a call. 61 // 62 // The unwindTrap flag is updated during unwinding. If set, frame.pc is the 63 // address of a faulting instruction instead of the return address of a 64 // call. It also means the liveness at pc may not be known. 65 // 66 // TODO: Distinguish frame.continpc, which is really the stack map PC, from 67 // the actual continuation PC, which is computed differently depending on 68 // this flag and a few other things. 69 unwindTrap 70 71 // unwindJumpStack indicates that, if the traceback is on a system stack, it 72 // should resume tracing at the user stack when the system stack is 73 // exhausted. 74 unwindJumpStack 75 ) 76 77 // errFatal reports whether an unwinding error should throw rather than be 78 // tolerated: always with neither unwindPrintErrors nor unwindSilentErrors 79 // set (e.g. GC unwinds), or under GODEBUG=tracebackcrash=1. 80 func (u *unwinder) errFatal() bool { 81 return u.flags&(unwindPrintErrors|unwindSilentErrors) == 0 || debug.tracebackcrash != 0 82 } 83 84 // An unwinder iterates the physical stack frames of a Go sack. 85 // 86 // Typical use of an unwinder looks like: 87 // 88 // var u unwinder 89 // for u.init(gp, 0); u.valid(); u.next() { 90 // // ... use frame info in u ... 91 // } 92 // 93 // Implementation note: This is carefully structured to be pointer-free because 94 // tracebacks happen in places that disallow write barriers (e.g., signals). 95 // Even if this is stack-allocated, its pointer-receiver methods don't know that 96 // their receiver is on the stack, so they still emit write barriers. Here we 97 // address that by carefully avoiding any pointers in this type. Another 98 // approach would be to split this into a mutable part that's passed by pointer 99 // but contains no pointers itself and an immutable part that's passed and 100 // returned by value and can contain pointers. We could potentially hide that 101 // we're doing that in trivial methods that are inlined into the caller that has 102 // the stack allocation, but that's fragile. 103 type unwinder struct { 104 // frame is the current physical stack frame, or all 0s if 105 // there is no frame. 106 frame stkframe 107 108 // g is the G who's stack is being unwound. If the 109 // unwindJumpStack flag is set and the unwinder jumps stacks, 110 // this will be different from the initial G. 111 g guintptr 112 113 // cgoCtxt is the index into g.cgoCtxt of the next frame on the cgo stack. 114 // The cgo stack is unwound in tandem with the Go stack as we find marker frames. 115 cgoCtxt int 116 117 // calleeFuncID is the function ID of the caller of the current 118 // frame. 119 calleeFuncID abi.FuncID 120 121 // flags are the flags to this unwind. Some of these are updated as we 122 // unwind (see the flags documentation). 123 flags unwindFlags 124 } 125 126 // init initializes u to start unwinding gp's stack and positions the 127 // iterator on gp's innermost frame. gp must not be the current G. 128 // 129 // A single unwinder can be reused for multiple unwinds. 130 func (u *unwinder) init(gp *g, flags unwindFlags) { 131 // Implementation note: This starts the iterator on the first frame and we 132 // provide a "valid" method. Alternatively, this could start in a "before 133 // the first frame" state and "next" could return whether it was able to 134 // move to the next frame, but that's both more awkward to use in a "for" 135 // loop and is harder to implement because we have to do things differently 136 // for the first frame. 137 u.initAt(^uintptr(0), ^uintptr(0), ^uintptr(0), gp, flags) 138 } 139 140 func (u *unwinder) initAt(pc0, sp0, lr0 uintptr, gp *g, flags unwindFlags) { 141 // Don't call this "g"; it's too easy get "g" and "gp" confused. 142 if ourg := getg(); ourg == gp && ourg == ourg.m.curg { 143 // The starting sp has been passed in as a uintptr, and the caller may 144 // have other uintptr-typed stack references as well. 145 // If during one of the calls that got us here or during one of the 146 // callbacks below the stack must be grown, all these uintptr references 147 // to the stack will not be updated, and traceback will continue 148 // to inspect the old stack memory, which may no longer be valid. 149 // Even if all the variables were updated correctly, it is not clear that 150 // we want to expose a traceback that begins on one stack and ends 151 // on another stack. That could confuse callers quite a bit. 152 // Instead, we require that initAt and any other function that 153 // accepts an sp for the current goroutine (typically obtained by 154 // calling GetCallerSP) must not run on that goroutine's stack but 155 // instead on the g0 stack. 156 throw("cannot trace user goroutine on its own stack") 157 } 158 159 if pc0 == ^uintptr(0) && sp0 == ^uintptr(0) { // Signal to fetch saved values from gp. 160 if gp.syscallsp != 0 { 161 pc0 = gp.syscallpc 162 sp0 = gp.syscallsp 163 if usesLR { 164 lr0 = 0 165 } 166 } else { 167 pc0 = gp.sched.pc 168 sp0 = gp.sched.sp 169 if usesLR { 170 lr0 = gp.sched.lr 171 } 172 } 173 } 174 175 var frame stkframe 176 frame.pc = pc0 177 frame.sp = sp0 178 if usesLR { 179 frame.lr = lr0 180 } 181 182 // If the PC is zero, it's likely a nil function call. 183 // Start in the caller's frame. 184 if frame.pc == 0 { 185 if usesLR { 186 frame.pc = *(*uintptr)(unsafe.Pointer(frame.sp)) 187 frame.lr = 0 188 } else { 189 frame.pc = *(*uintptr)(unsafe.Pointer(frame.sp)) 190 frame.sp += goarch.PtrSize 191 } 192 } 193 194 // internal/runtime/atomic functions call into kernel helpers on 195 // arm < 7. See internal/runtime/atomic/sys_linux_arm.s. 196 // 197 // Start in the caller's frame. 198 if GOARCH == "arm" && goarm < 7 && GOOS == "linux" && frame.pc&0xffff0000 == 0xffff0000 { 199 // Note that the calls are simple BL without pushing the return 200 // address, so we use LR directly. 201 // 202 // The kernel helpers are frameless leaf functions, so SP and 203 // LR are not touched. 204 frame.pc = frame.lr 205 frame.lr = 0 206 } 207 208 f := findfunc(frame.pc) 209 if !f.valid() { 210 if flags&unwindSilentErrors == 0 { 211 print("runtime: g ", gp.goid, " gp=", gp, ": unknown pc ", hex(frame.pc), "\n") 212 tracebackHexdump(gp.stack, &frame, 0) 213 } 214 if flags&(unwindPrintErrors|unwindSilentErrors) == 0 { 215 throw("unknown pc") 216 } 217 *u = unwinder{} 218 return 219 } 220 frame.fn = f 221 222 // Populate the unwinder. 223 *u = unwinder{ 224 frame: frame, 225 g: gp.guintptr(), 226 cgoCtxt: len(gp.cgoCtxt) - 1, 227 calleeFuncID: abi.FuncIDNormal, 228 flags: flags, 229 } 230 231 isSyscall := frame.pc == pc0 && frame.sp == sp0 && pc0 == gp.syscallpc && sp0 == gp.syscallsp 232 u.resolveInternal(true, isSyscall) 233 } 234 235 func (u *unwinder) valid() bool { 236 return u.frame.pc != 0 237 } 238 239 // resolveInternal fills in u.frame based on u.frame.fn, pc, and sp. 240 // 241 // innermost indicates that this is the first resolve on this stack. If 242 // innermost is set, isSyscall indicates that the PC/SP was retrieved from 243 // gp.syscall*; this is otherwise ignored. 244 // 245 // On entry, u.frame contains: 246 // - fn is the running function. 247 // - pc is the PC in the running function. 248 // - sp is the stack pointer at that program counter. 249 // - For the innermost frame on LR machines, lr is the program counter that called fn. 250 // 251 // On return, u.frame contains: 252 // - fp is the stack pointer of the caller. 253 // - lr is the program counter that called fn. 254 // - varp, argp, and continpc are populated for the current frame. 255 // 256 // If fn is a stack-jumping function, resolveInternal can change the entire 257 // frame state to follow that stack jump. 258 // 259 // This is internal to unwinder. 260 func (u *unwinder) resolveInternal(innermost, isSyscall bool) { 261 frame := &u.frame 262 gp := u.g.ptr() 263 264 f := frame.fn 265 if f.pcsp == 0 { 266 // No frame information, must be external function, like race support. 267 // See golang.org/issue/13568. 268 u.finishInternal() 269 return 270 } 271 272 // Compute function info flags. 273 flag := f.flag 274 if f.funcID == abi.FuncID_cgocallback { 275 // cgocallback does write SP to switch from the g0 to the curg stack, 276 // but it carefully arranges that during the transition BOTH stacks 277 // have cgocallback frame valid for unwinding through. 278 // So we don't need to exclude it with the other SP-writing functions. 279 flag &^= abi.FuncFlagSPWrite 280 } 281 if isSyscall { 282 // Some Syscall functions write to SP, but they do so only after 283 // saving the entry PC/SP using entersyscall. 284 // Since we are using the entry PC/SP, the later SP write doesn't matter. 285 flag &^= abi.FuncFlagSPWrite 286 } 287 288 // Found an actual function. 289 // Derive frame pointer. 290 if frame.fp == 0 { 291 // Jump over system stack transitions. If we're on g0 and there's a user 292 // goroutine, try to jump. Otherwise this is a regular call. 293 // We also defensively check that this won't switch M's on us, 294 // which could happen at critical points in the scheduler. 295 // This ensures gp.m doesn't change from a stack jump. 296 if u.flags&unwindJumpStack != 0 && gp == gp.m.g0 && gp.m.curg != nil && gp.m.curg.m == gp.m { 297 switch f.funcID { 298 case abi.FuncID_morestack: 299 // morestack does not return normally -- newstack() 300 // gogo's to curg.sched. Match that. 301 // This keeps morestack() from showing up in the backtrace, 302 // but that makes some sense since it'll never be returned 303 // to. 304 gp = gp.m.curg 305 u.g.set(gp) 306 frame.pc = gp.sched.pc 307 frame.fn = findfunc(frame.pc) 308 f = frame.fn 309 flag = f.flag 310 frame.lr = gp.sched.lr 311 frame.sp = gp.sched.sp 312 u.cgoCtxt = len(gp.cgoCtxt) - 1 313 case abi.FuncID_systemstack: 314 // systemstack returns normally, so just follow the 315 // stack transition. 316 if usesLR && funcspdelta(f, frame.pc) == 0 { 317 // We're at the function prologue and the stack 318 // switch hasn't happened, or epilogue where we're 319 // about to return. Just unwind normally. 320 // Do this only on LR machines because on x86 321 // systemstack doesn't have an SP delta (the CALL 322 // instruction opens the frame), therefore no way 323 // to check. 324 flag &^= abi.FuncFlagSPWrite 325 break 326 } 327 gp = gp.m.curg 328 u.g.set(gp) 329 frame.sp = gp.sched.sp 330 u.cgoCtxt = len(gp.cgoCtxt) - 1 331 flag &^= abi.FuncFlagSPWrite 332 } 333 } 334 frame.fp = frame.sp + uintptr(funcspdelta(f, frame.pc)) 335 if !usesLR { 336 // On x86, call instruction pushes return PC before entering new function. 337 frame.fp += goarch.PtrSize 338 } 339 } 340 341 // Derive link register. 342 if flag&abi.FuncFlagTopFrame != 0 { 343 // This function marks the top of the stack. Stop the traceback. 344 frame.lr = 0 345 } else if flag&abi.FuncFlagSPWrite != 0 && (!innermost || u.flags&(unwindPrintErrors|unwindSilentErrors) != 0) { 346 // The function we are in does a write to SP that we don't know 347 // how to encode in the spdelta table. Examples include context 348 // switch routines like runtime.gogo but also any code that switches 349 // to the g0 stack to run host C code. 350 // We can't reliably unwind the SP (we might not even be on 351 // the stack we think we are), so stop the traceback here. 352 // 353 // The one exception (encoded in the complex condition above) is that 354 // we assume if we're doing a precise traceback, and this is the 355 // innermost frame, that the SPWRITE function voluntarily preempted itself on entry 356 // during the stack growth check. In that case, the function has 357 // not yet had a chance to do any writes to SP and is safe to unwind. 358 // isAsyncSafePoint does not allow assembly functions to be async preempted, 359 // and preemptPark double-checks that SPWRITE functions are not async preempted. 360 // So for GC stack traversal, we can safely ignore SPWRITE for the innermost frame, 361 // but farther up the stack we'd better not find any. 362 // This is somewhat imprecise because we're just guessing that we're in the stack 363 // growth check. It would be better if SPWRITE were encoded in the spdelta 364 // table so we would know for sure that we were still in safe code. 365 // 366 // uSE uPE inn | action 367 // T _ _ | frame.lr = 0 368 // F T _ | frame.lr = 0 369 // F F F | print; panic 370 // F F T | ignore SPWrite 371 if u.flags&(unwindPrintErrors|unwindSilentErrors) == 0 && !innermost { 372 println("traceback: unexpected SPWRITE function", funcname(f)) 373 throw("traceback") 374 } 375 frame.lr = 0 376 } else { 377 var lrPtr uintptr 378 if usesLR { 379 if innermost && frame.sp < frame.fp || frame.lr == 0 { 380 lrPtr = frame.sp 381 frame.lr = *(*uintptr)(unsafe.Pointer(lrPtr)) 382 } 383 } else { 384 if frame.lr == 0 { 385 lrPtr = frame.fp - goarch.PtrSize 386 frame.lr = *(*uintptr)(unsafe.Pointer(lrPtr)) 387 } 388 } 389 } 390 391 frame.varp = frame.fp 392 if !usesLR { 393 // On x86, call instruction pushes return PC before entering new function. 394 frame.varp -= goarch.PtrSize 395 } 396 397 // For architectures with frame pointers, if there's 398 // a frame, then there's a saved frame pointer here. 399 // 400 // NOTE: This code is not as general as it looks. 401 // On x86, the ABI is to save the frame pointer word at the 402 // top of the stack frame, so we have to back down over it. 403 // On arm64, the frame pointer should be at the bottom of 404 // the stack (with R29 (aka FP) = RSP), in which case we would 405 // not want to do the subtraction here. But we started out without 406 // any frame pointer, and when we wanted to add it, we didn't 407 // want to break all the assembly doing direct writes to 8(RSP) 408 // to set the first parameter to a called function. 409 // So we decided to write the FP link *below* the stack pointer 410 // (with R29 = RSP - 8 in Go functions). 411 // This is technically ABI-compatible but not standard. 412 // And it happens to end up mimicking the x86 layout. 413 // Other architectures may make different decisions. 414 if frame.varp > frame.sp && framepointer_enabled { 415 frame.varp -= goarch.PtrSize 416 } 417 418 frame.argp = frame.fp + sys.MinFrameSize 419 420 // Determine frame's 'continuation PC', where it can continue. 421 // Normally this is the return address on the stack, but if sigpanic 422 // is immediately below this function on the stack, then the frame 423 // stopped executing due to a trap, and frame.pc is probably not 424 // a safe point for looking up liveness information. In this panicking case, 425 // the function either doesn't return at all (if it has no defers or if the 426 // defers do not recover) or it returns from one of the calls to 427 // deferproc a second time (if the corresponding deferred func recovers). 428 // In the latter case, use a deferreturn call site as the continuation pc. 429 frame.continpc = frame.pc 430 if u.calleeFuncID == abi.FuncID_sigpanic { 431 if frame.fn.deferreturn != 0 { 432 frame.continpc = frame.fn.entry() + uintptr(frame.fn.deferreturn) + 1 433 // Note: this may perhaps keep return variables alive longer than 434 // strictly necessary, as we are using "function has a defer statement" 435 // as a proxy for "function actually deferred something". It seems 436 // to be a minor drawback. (We used to actually look through the 437 // gp._defer for a defer corresponding to this function, but that 438 // is hard to do with defer records on the stack during a stack copy.) 439 // Note: the +1 is to offset the -1 that 440 // (*stkframe).getStackMap does to back up a return 441 // address make sure the pc is in the CALL instruction. 442 } else { 443 frame.continpc = 0 444 } 445 } 446 } 447 448 func isInjectedCall(id abi.FuncID) bool { 449 return id == abi.FuncID_sigpanic || id == abi.FuncID_asyncPreempt || id == abi.FuncID_debugCallV2 450 } 451 452 func (u *unwinder) next() { 453 frame := &u.frame 454 f := frame.fn 455 gp := u.g.ptr() 456 457 // Do not unwind past the bottom of the stack. 458 if frame.lr == 0 { 459 u.finishInternal() 460 return 461 } 462 flr := findfunc(frame.lr) 463 if !flr.valid() { 464 // This happens if you get a profiling interrupt at just the wrong time. 465 fail := u.errFatal() 466 doPrint := u.flags&unwindSilentErrors == 0 467 if doPrint && gp.m != nil && gp.m.incgo && f.funcID == abi.FuncID_sigpanic { 468 // We can inject sigpanic 469 // calls directly into C code, 470 // in which case we'll see a C 471 // return PC. Don't complain. 472 doPrint = false 473 } 474 if fail || doPrint { 475 print("runtime: g ", gp.goid, ": unexpected return pc for ", funcname(f), " called from ", hex(frame.lr), "\n") 476 tracebackHexdump(gp.stack, frame, 0) 477 } 478 if fail { 479 throw("unknown caller pc") 480 } 481 frame.lr = 0 482 u.finishInternal() 483 return 484 } 485 486 if frame.pc == frame.lr && frame.sp == frame.fp { 487 // If the next frame is identical to the current frame, we cannot make 488 // progress, like the invalid-caller-PC case above. A stuck frame does not 489 // always mean the stack is corrupt: a signal can land in machine code the 490 // runtime has no unwind information for, such as a JIT or an assembly blob 491 // entered by a jump from a frameless Go symbol, whose prologue leaves 492 // pc == lr and sp == fp. Such generated machine code is an ABI violation, 493 // but does not imply the stack is corrupt. Do not unwind, because no 494 // amount of unwinding can recover that failure class. 495 fail := u.errFatal() 496 if fail || u.flags&unwindSilentErrors == 0 { 497 print("runtime: traceback stuck. pc=", hex(frame.pc), " sp=", hex(frame.sp), "\n") 498 tracebackHexdump(gp.stack, frame, frame.sp) 499 } 500 if fail { 501 throw("traceback stuck") 502 } 503 frame.lr = 0 504 u.finishInternal() 505 return 506 } 507 508 injectedCall := isInjectedCall(f.funcID) 509 if injectedCall { 510 u.flags |= unwindTrap 511 } else { 512 u.flags &^= unwindTrap 513 } 514 515 // Unwind to next frame. 516 u.calleeFuncID = f.funcID 517 frame.fn = flr 518 frame.pc = frame.lr 519 frame.lr = 0 520 frame.sp = frame.fp 521 frame.fp = 0 522 523 // On link register architectures, sighandler saves the LR on stack 524 // before faking a call. 525 if usesLR && injectedCall { 526 x := *(*uintptr)(unsafe.Pointer(frame.sp)) 527 // same as the size bump used in scanframeworker. 528 frame.sp += alignUp(sys.MinFrameSize, sys.StackAlign) 529 f = findfunc(frame.pc) 530 frame.fn = f 531 if !f.valid() { 532 frame.pc = x 533 } else if funcspdelta(f, frame.pc) == 0 { 534 frame.lr = x 535 } 536 } 537 538 u.resolveInternal(false, false) 539 } 540 541 // finishInternal is an unwinder-internal helper called after the stack has been 542 // exhausted. It sets the unwinder to an invalid state and checks that it 543 // successfully unwound the entire stack. 544 func (u *unwinder) finishInternal() { 545 u.frame.pc = 0 546 547 // Note that panic != nil is okay here: there can be leftover panics, 548 // because the defers on the panic stack do not nest in frame order as 549 // they do on the defer stack. If you have: 550 // 551 // frame 1 defers d1 552 // frame 2 defers d2 553 // frame 3 defers d3 554 // frame 4 panics 555 // frame 4's panic starts running defers 556 // frame 5, running d3, defers d4 557 // frame 5 panics 558 // frame 5's panic starts running defers 559 // frame 6, running d4, garbage collects 560 // frame 6, running d2, garbage collects 561 // 562 // During the execution of d4, the panic stack is d4 -> d3, which 563 // is nested properly, and we'll treat frame 3 as resumable, because we 564 // can find d3. (And in fact frame 3 is resumable. If d4 recovers 565 // and frame 5 continues running, d3, d3 can recover and we'll 566 // resume execution in (returning from) frame 3.) 567 // 568 // During the execution of d2, however, the panic stack is d2 -> d3, 569 // which is inverted. The scan will match d2 to frame 2 but having 570 // d2 on the stack until then means it will not match d3 to frame 3. 571 // This is okay: if we're running d2, then all the defers after d2 have 572 // completed and their corresponding frames are dead. Not finding d3 573 // for frame 3 means we'll set frame 3's continpc == 0, which is correct 574 // (frame 3 is dead). At the end of the walk the panic stack can thus 575 // contain defers (d3 in this case) for dead frames. The inversion here 576 // always indicates a dead frame, and the effect of the inversion on the 577 // scan is to hide those dead frames, so the scan is still okay: 578 // what's left on the panic stack are exactly (and only) the dead frames. 579 // 580 // We require callback != nil here because only when callback != nil 581 // do we know that gentraceback is being called in a "must be correct" 582 // context as opposed to a "best effort" context. The tracebacks with 583 // callbacks only happen when everything is stopped nicely. 584 // At other times, such as when gathering a stack for a profiling signal 585 // or when printing a traceback during a crash, everything may not be 586 // stopped nicely, and the stack walk may not be able to complete. 587 gp := u.g.ptr() 588 if u.flags&(unwindPrintErrors|unwindSilentErrors) == 0 && u.frame.sp != gp.stktopsp { 589 print("runtime: g", gp.goid, ": frame.sp=", hex(u.frame.sp), " top=", hex(gp.stktopsp), "\n") 590 print("\tstack=[", hex(gp.stack.lo), "-", hex(gp.stack.hi), "\n") 591 throw("traceback did not unwind completely") 592 } 593 } 594 595 // symPC returns the PC that should be used for symbolizing the current frame. 596 // Specifically, this is the PC of the last instruction executed in this frame. 597 // 598 // If this frame did a normal call, then frame.pc is a return PC, so this will 599 // return frame.pc-1, which points into the CALL instruction. If the frame was 600 // interrupted by a signal (e.g., profiler, segv, etc) then frame.pc is for the 601 // trapped instruction, so this returns frame.pc. See issue #34123. Finally, 602 // frame.pc can be at function entry when the frame is initialized without 603 // actually running code, like in runtime.mstart, in which case this returns 604 // frame.pc because that's the best we can do. 605 func (u *unwinder) symPC() uintptr { 606 if u.flags&unwindTrap == 0 && u.frame.pc > u.frame.fn.entry() { 607 // Regular call. 608 return u.frame.pc - 1 609 } 610 // Trapping instruction or we're at the function entry point. 611 return u.frame.pc 612 } 613 614 // cgoCallers populates pcBuf with the cgo callers of the current frame using 615 // the registered cgo unwinder. It returns the number of PCs written to pcBuf. 616 // If the current frame is not a cgo frame or if there's no registered cgo 617 // unwinder, it returns 0. 618 func (u *unwinder) cgoCallers(pcBuf []uintptr) int { 619 if !cgoTracebackAvailable() || u.frame.fn.funcID != abi.FuncID_cgocallback || u.cgoCtxt < 0 { 620 // We don't have a cgo unwinder (typical case), or we do but we're not 621 // in a cgo frame or we're out of cgo context. 622 return 0 623 } 624 625 ctxt := u.g.ptr().cgoCtxt[u.cgoCtxt] 626 u.cgoCtxt-- 627 cgoContextPCs(ctxt, pcBuf) 628 for i, pc := range pcBuf { 629 if pc == 0 { 630 return i 631 } 632 } 633 return len(pcBuf) 634 } 635 636 // tracebackPCs populates pcBuf with the return addresses for each frame from u 637 // and returns the number of PCs written to pcBuf. The returned PCs correspond 638 // to "logical frames" rather than "physical frames"; that is if A is inlined 639 // into B, this will still return a PCs for both A and B. This also includes PCs 640 // generated by the cgo unwinder, if one is registered. 641 // 642 // If skip != 0, this skips this many logical frames. 643 // 644 // Callers should set the unwindSilentErrors flag on u. 645 func tracebackPCs(u *unwinder, skip int, pcBuf []uintptr) int { 646 var cgoBuf [32]uintptr 647 n := 0 648 for ; n < len(pcBuf) && u.valid(); u.next() { 649 f := u.frame.fn 650 cgoN := u.cgoCallers(cgoBuf[:]) 651 652 // TODO: Why does &u.cache cause u to escape? (Same in traceback2) 653 for iu, uf := newInlineUnwinder(f, u.symPC()); n < len(pcBuf) && uf.valid(); uf = iu.next(uf) { 654 sf := iu.srcFunc(uf) 655 if sf.funcID == abi.FuncIDWrapper && elideWrapperCalling(u.calleeFuncID) { 656 // ignore wrappers 657 } else if skip > 0 { 658 skip-- 659 } else { 660 // Callers expect the pc buffer to contain return addresses 661 // and do the -1 themselves, so we add 1 to the call pc to 662 // create a "return pc". Since there is no actual call, here 663 // "return pc" just means a pc you subtract 1 from to get 664 // the pc of the "call". The actual no-op we insert may or 665 // may not be 1 byte. 666 pcBuf[n] = uf.pc + 1 667 n++ 668 } 669 u.calleeFuncID = sf.funcID 670 } 671 // Add cgo frames (if we're done skipping over the requested number of 672 // Go frames). 673 if skip == 0 { 674 n += copy(pcBuf[n:], cgoBuf[:cgoN]) 675 } 676 } 677 return n 678 } 679 680 // printArgs prints function arguments in traceback. 681 func printArgs(f funcInfo, argp unsafe.Pointer, pc uintptr) { 682 p := (*[abi.TraceArgsMaxLen]uint8)(funcdata(f, abi.FUNCDATA_ArgInfo)) 683 if p == nil { 684 return 685 } 686 687 liveInfo := funcdata(f, abi.FUNCDATA_ArgLiveInfo) 688 liveIdx := pcdatavalue(f, abi.PCDATA_ArgLiveIndex, pc) 689 startOffset := uint8(0xff) // smallest offset that needs liveness info (slots with a lower offset is always live) 690 if liveInfo != nil { 691 startOffset = *(*uint8)(liveInfo) 692 } 693 694 isLive := func(off, slotIdx uint8) bool { 695 if liveInfo == nil || liveIdx <= 0 { 696 return true // no liveness info, always live 697 } 698 if off < startOffset { 699 return true 700 } 701 bits := *(*uint8)(add(liveInfo, uintptr(liveIdx)+uintptr(slotIdx/8))) 702 return bits&(1<<(slotIdx%8)) != 0 703 } 704 705 print1 := func(off, sz, slotIdx uint8) { 706 x := readUnaligned64(add(argp, uintptr(off))) 707 // mask out irrelevant bits 708 if sz < 8 { 709 shift := 64 - sz*8 710 if goarch.BigEndian { 711 x = x >> shift 712 } else { 713 x = x << shift >> shift 714 } 715 } 716 print(hex(x)) 717 if !isLive(off, slotIdx) { 718 print("?") 719 } 720 } 721 722 start := true 723 printcomma := func() { 724 if !start { 725 print(", ") 726 } 727 } 728 pi := 0 729 slotIdx := uint8(0) // register arg spill slot index 730 printloop: 731 for { 732 o := p[pi] 733 pi++ 734 switch o { 735 case abi.TraceArgsEndSeq: 736 break printloop 737 case abi.TraceArgsStartAgg: 738 printcomma() 739 print("{") 740 start = true 741 continue 742 case abi.TraceArgsEndAgg: 743 print("}") 744 case abi.TraceArgsDotdotdot: 745 printcomma() 746 print("...") 747 case abi.TraceArgsOffsetTooLarge: 748 printcomma() 749 print("_") 750 default: 751 printcomma() 752 sz := p[pi] 753 pi++ 754 print1(o, sz, slotIdx) 755 if o >= startOffset { 756 slotIdx++ 757 } 758 } 759 start = false 760 } 761 } 762 763 // funcNamePiecesForPrint returns the function name for printing to the user. 764 // It returns five pieces so it doesn't need an allocation for string 765 // concatenation. 766 func funcNamePiecesForPrint(name string) (string, string, string, string, string) { 767 // Replace the shape name in generic function with "...". 768 i := bytealg.IndexByteString(name, '[') 769 if i < 0 { 770 return name, "", "", "", "" 771 } 772 j := len(name) - 1 773 for name[j] != ']' { 774 j-- 775 } 776 if j <= i { 777 return name, "", "", "", "" 778 } 779 780 interior := name[i+1 : j] // '[' interior ']' 781 // This is an early-out to skip the more-detailed parsing that 782 // follows -- if there's no '[' in the interior, that implies 783 // (assuming balanced brackets) no ']' in the interior, and thus 784 // this will be the answer. If brackets are not balanced 785 // (malformed input, which was already a risk), this will 786 // eat/hide the unbalanced "]". 787 if bytealg.IndexByteString(interior, '[') < 0 { 788 return name[:i], "[...]", name[j+1:], "", "" 789 } 790 // Generic method of generic type. 791 // know interior contains at least "...[..." 792 // expect interior contains "...]___[...". 793 // don't know whether "..." contains balanced brackets or not. 794 // or the compiler might have a bug in its naming-things department. 795 // hope to return name[:i], "[...]", ___, "[...]", name[j+1:] 796 depth := 1 // beginning after first "[", looking for balancing "]" 797 rbr, lbr := -1, -1 798 for k, c := range interior { 799 if c == '[' { 800 depth++ 801 if depth != 1 { 802 continue 803 } 804 // rbr != -1 because rbr is only assigned if depth == 0 805 lbr = k 806 break // success, depth == 1, rbr >= 0, lbr > rbr 807 } 808 if c == ']' { 809 depth-- 810 if depth < 0 { 811 break // malformed "...]...]" 812 } 813 if depth != 0 { 814 continue 815 } 816 // cannot execute this twice; depth == 0 -> { ']' -> malformed, '[' -> success } 817 rbr = k 818 } 819 } 820 if depth == 1 { 821 if rbr >= 0 && lbr > rbr { 822 return name[:i], "[...]", interior[rbr+1 : lbr], "[...]", name[j+1:] 823 } 824 if rbr == -1 && lbr == -1 { 825 // the bracket seen in the interior must have been balanced in a "[]" pattern, not "][" 826 // return the single-brackets (not a generic method of a generic type) result 827 return name[:i], "[...]", name[j+1:], "", "" 828 } 829 } 830 831 // malformed, return the whole name 832 return name, "", "", "", "" 833 834 } 835 836 // funcNameForPrint returns the function name for printing to the user. 837 func funcNameForPrint(name string) string { 838 a, b, c, d, e := funcNamePiecesForPrint(name) 839 return a + b + c + d + e 840 } 841 842 // printFuncName prints a function name. name is the function name in 843 // the binary's func data table. 844 func printFuncName(name string) { 845 if name == "runtime.gopanic" { 846 print("panic") 847 return 848 } 849 a, b, c, d, e := funcNamePiecesForPrint(name) 850 print(a, b, c, d, e) 851 } 852 853 func printcreatedby(gp *g) { 854 // Show what created goroutine, except main goroutine (goid 1). 855 pc := gp.gopc 856 f := findfunc(pc) 857 if f.valid() && showframe(f.srcFunc(), gp, false, abi.FuncIDNormal) && gp.goid != 1 { 858 printcreatedby1(f, pc, gp.parentGoid) 859 } 860 } 861 862 func printcreatedby1(f funcInfo, pc uintptr, goid uint64) { 863 print("created by ") 864 printFuncName(funcname(f)) 865 if goid != 0 { 866 print(" in goroutine ", goid) 867 } 868 print("\n") 869 tracepc := pc // back up to CALL instruction for funcline. 870 if pc > f.entry() { 871 tracepc -= sys.PCQuantum 872 } 873 file, line := funcline(f, tracepc) 874 print("\t", file, ":", line) 875 if pc > f.entry() { 876 print(" +", hex(pc-f.entry())) 877 } 878 print("\n") 879 } 880 881 func traceback(pc, sp, lr uintptr, gp *g) { 882 traceback1(pc, sp, lr, gp, 0) 883 } 884 885 // tracebacktrap is like traceback but expects that the PC and SP were obtained 886 // from a trap, not from gp->sched or gp->syscallpc/gp->syscallsp or GetCallerPC/GetCallerSP. 887 // Because they are from a trap instead of from a saved pair, 888 // the initial PC must not be rewound to the previous instruction. 889 // (All the saved pairs record a PC that is a return address, so we 890 // rewind it into the CALL instruction.) 891 // If gp.m.libcall{g,pc,sp} information is available, it uses that information in preference to 892 // the pc/sp/lr passed in. 893 func tracebacktrap(pc, sp, lr uintptr, gp *g) { 894 if gp.m.libcallsp != 0 { 895 // We're in C code somewhere, traceback from the saved position. 896 traceback1(gp.m.libcallpc, gp.m.libcallsp, 0, gp.m.libcallg.ptr(), 0) 897 return 898 } 899 traceback1(pc, sp, lr, gp, unwindTrap) 900 } 901 902 func traceback1(pc, sp, lr uintptr, gp *g, flags unwindFlags) { 903 // If the goroutine is in cgo, and we have a cgo traceback, print that. 904 if iscgo && gp.m != nil && gp.m.ncgo > 0 && gp.syscallsp != 0 && gp.m.cgoCallers != nil && gp.m.cgoCallers[0] != 0 { 905 // Lock cgoCallers so that a signal handler won't 906 // change it, copy the array, reset it, unlock it. 907 // We are locked to the thread and are not running 908 // concurrently with a signal handler. 909 // We just have to stop a signal handler from interrupting 910 // in the middle of our copy. 911 gp.m.cgoCallersUse.Store(1) 912 cgoCallers := *gp.m.cgoCallers 913 gp.m.cgoCallers[0] = 0 914 gp.m.cgoCallersUse.Store(0) 915 916 printCgoTraceback(&cgoCallers) 917 } 918 919 if readgstatus(gp)&^_Gscan == _Gsyscall { 920 // Override registers if blocked in system call. 921 pc = gp.syscallpc 922 sp = gp.syscallsp 923 flags &^= unwindTrap 924 } 925 if gp.m != nil && gp.m.vdsoSP != 0 { 926 // Override registers if running in VDSO. This comes after the 927 // _Gsyscall check to cover VDSO calls after entersyscall. 928 pc = gp.m.vdsoPC 929 sp = gp.m.vdsoSP 930 flags &^= unwindTrap 931 } 932 933 // Print traceback. 934 // 935 // We print the first tracebackInnerFrames frames, and the last 936 // tracebackOuterFrames frames. There are many possible approaches to this. 937 // There are various complications to this: 938 // 939 // - We'd prefer to walk the stack once because in really bad situations 940 // traceback may crash (and we want as much output as possible) or the stack 941 // may be changing. 942 // 943 // - Each physical frame can represent several logical frames, so we might 944 // have to pause in the middle of a physical frame and pick up in the middle 945 // of a physical frame. 946 // 947 // - The cgo symbolizer can expand a cgo PC to more than one logical frame, 948 // and involves juggling state on the C side that we don't manage. Since its 949 // expansion state is managed on the C side, we can't capture the expansion 950 // state part way through, and because the output strings are managed on the 951 // C side, we can't capture the output. Thus, our only choice is to replay a 952 // whole expansion, potentially discarding some of it. 953 // 954 // Rejected approaches: 955 // 956 // - Do two passes where the first pass just counts and the second pass does 957 // all the printing. This is undesirable if the stack is corrupted or changing 958 // because we won't see a partial stack if we panic. 959 // 960 // - Keep a ring buffer of the last N logical frames and use this to print 961 // the bottom frames once we reach the end of the stack. This works, but 962 // requires keeping a surprising amount of state on the stack, and we have 963 // to run the cgo symbolizer twice—once to count frames, and a second to 964 // print them—since we can't retain the strings it returns. 965 // 966 // Instead, we print the outer frames, and if we reach that limit, we clone 967 // the unwinder, count the remaining frames, and then skip forward and 968 // finish printing from the clone. This makes two passes over the outer part 969 // of the stack, but the single pass over the inner part ensures that's 970 // printed immediately and not revisited. It keeps minimal state on the 971 // stack. And through a combination of skip counts and limits, we can do all 972 // of the steps we need with a single traceback printer implementation. 973 // 974 // We could be more lax about exactly how many frames we print, for example 975 // always stopping and resuming on physical frame boundaries, or at least 976 // cgo expansion boundaries. It's not clear that's much simpler. 977 flags |= unwindPrintErrors 978 var u unwinder 979 tracebackWithRuntime := func(showRuntime bool) int { 980 const maxInt int = 0x7fffffff 981 u.initAt(pc, sp, lr, gp, flags) 982 n, lastN := traceback2(&u, showRuntime, 0, tracebackInnerFrames) 983 if n < tracebackInnerFrames { 984 // We printed the whole stack. 985 return n 986 } 987 // Clone the unwinder and figure out how many frames are left. This 988 // count will include any logical frames already printed for u's current 989 // physical frame. 990 u2 := u 991 remaining, _ := traceback2(&u, showRuntime, maxInt, 0) 992 elide := remaining - lastN - tracebackOuterFrames 993 if elide > 0 { 994 print("...", elide, " frames elided...\n") 995 traceback2(&u2, showRuntime, lastN+elide, tracebackOuterFrames) 996 } else if elide <= 0 { 997 // There are tracebackOuterFrames or fewer frames left to print. 998 // Just print the rest of the stack. 999 traceback2(&u2, showRuntime, lastN, tracebackOuterFrames) 1000 } 1001 return n 1002 } 1003 // By default, omits runtime frames. If that means we print nothing at all, 1004 // repeat forcing all frames printed. 1005 if tracebackWithRuntime(false) == 0 { 1006 tracebackWithRuntime(true) 1007 } 1008 printcreatedby(gp) 1009 1010 if gp.ancestors == nil { 1011 return 1012 } 1013 for _, ancestor := range *gp.ancestors { 1014 printAncestorTraceback(ancestor) 1015 } 1016 } 1017 1018 // traceback2 prints a stack trace starting at u. It skips the first "skip" 1019 // logical frames, after which it prints at most "max" logical frames. It 1020 // returns n, which is the number of logical frames skipped and printed, and 1021 // lastN, which is the number of logical frames skipped or printed just in the 1022 // physical frame that u references. 1023 func traceback2(u *unwinder, showRuntime bool, skip, max int) (n, lastN int) { 1024 // commitFrame commits to a logical frame and returns whether this frame 1025 // should be printed and whether iteration should stop. 1026 commitFrame := func() (pr, stop bool) { 1027 if skip == 0 && max == 0 { 1028 // Stop 1029 return false, true 1030 } 1031 n++ 1032 lastN++ 1033 if skip > 0 { 1034 // Skip 1035 skip-- 1036 return false, false 1037 } 1038 // Print 1039 max-- 1040 return true, false 1041 } 1042 1043 gp := u.g.ptr() 1044 level, _, _ := gotraceback() 1045 var cgoBuf [32]uintptr 1046 for ; u.valid(); u.next() { 1047 lastN = 0 1048 f := u.frame.fn 1049 for iu, uf := newInlineUnwinder(f, u.symPC()); uf.valid(); uf = iu.next(uf) { 1050 sf := iu.srcFunc(uf) 1051 callee := u.calleeFuncID 1052 u.calleeFuncID = sf.funcID 1053 if !(showRuntime || showframe(sf, gp, n == 0, callee)) { 1054 continue 1055 } 1056 1057 if pr, stop := commitFrame(); stop { 1058 return 1059 } else if !pr { 1060 continue 1061 } 1062 1063 name := sf.name() 1064 file, line := iu.fileLine(uf) 1065 // Print during crash. 1066 // main(0x1, 0x2, 0x3) 1067 // /home/rsc/go/src/runtime/x.go:23 +0xf 1068 // 1069 printFuncName(name) 1070 print("(") 1071 if iu.isInlined(uf) { 1072 print("...") 1073 } else { 1074 argp := unsafe.Pointer(u.frame.argp) 1075 printArgs(f, argp, u.symPC()) 1076 } 1077 print(")\n") 1078 print("\t", file, ":", line) 1079 if !iu.isInlined(uf) { 1080 if u.frame.pc > f.entry() { 1081 print(" +", hex(u.frame.pc-f.entry())) 1082 } 1083 if gp.m != nil && gp.m.throwing >= throwTypeRuntime && gp == gp.m.curg || level >= 2 { 1084 print(" fp=", hex(u.frame.fp), " sp=", hex(u.frame.sp), " pc=", hex(u.frame.pc)) 1085 } 1086 } 1087 print("\n") 1088 } 1089 1090 // Print cgo frames. 1091 if cgoN := u.cgoCallers(cgoBuf[:]); cgoN > 0 { 1092 var arg cgoSymbolizerArg 1093 anySymbolized := false 1094 stop := false 1095 for _, pc := range cgoBuf[:cgoN] { 1096 if !cgoSymbolizerAvailable() { 1097 if pr, stop := commitFrame(); stop { 1098 break 1099 } else if pr { 1100 print("non-Go function at pc=", hex(pc), "\n") 1101 } 1102 } else { 1103 stop = printOneCgoTraceback(pc, commitFrame, &arg) 1104 anySymbolized = true 1105 if stop { 1106 break 1107 } 1108 } 1109 } 1110 if anySymbolized { 1111 // Free symbolization state. 1112 arg.pc = 0 1113 callCgoSymbolizer(&arg) 1114 } 1115 if stop { 1116 return 1117 } 1118 } 1119 } 1120 return n, 0 1121 } 1122 1123 // printAncestorTraceback prints the traceback of the given ancestor. 1124 // TODO: Unify this with gentraceback and CallersFrames. 1125 func printAncestorTraceback(ancestor ancestorInfo) { 1126 print("[originating from goroutine ", ancestor.goid, "]:\n") 1127 for fidx, pc := range ancestor.pcs { 1128 f := findfunc(pc) // f previously validated 1129 if showfuncinfo(f.srcFunc(), fidx == 0, abi.FuncIDNormal) { 1130 printAncestorTracebackFuncInfo(f, pc) 1131 } 1132 } 1133 if len(ancestor.pcs) == tracebackInnerFrames { 1134 print("...additional frames elided...\n") 1135 } 1136 // Show what created goroutine, except main goroutine (goid 1). 1137 f := findfunc(ancestor.gopc) 1138 if f.valid() && showfuncinfo(f.srcFunc(), false, abi.FuncIDNormal) && ancestor.goid != 1 { 1139 // In ancestor mode, we'll already print the goroutine ancestor. 1140 // Pass 0 for the goid parameter so we don't print it again. 1141 printcreatedby1(f, ancestor.gopc, 0) 1142 } 1143 } 1144 1145 // printAncestorTracebackFuncInfo prints the given function info at a given pc 1146 // within an ancestor traceback. The precision of this info is reduced 1147 // due to only have access to the pcs at the time of the caller 1148 // goroutine being created. 1149 func printAncestorTracebackFuncInfo(f funcInfo, pc uintptr) { 1150 u, uf := newInlineUnwinder(f, pc) 1151 file, line := u.fileLine(uf) 1152 printFuncName(u.srcFunc(uf).name()) 1153 print("(...)\n") 1154 print("\t", file, ":", line) 1155 if pc > f.entry() { 1156 print(" +", hex(pc-f.entry())) 1157 } 1158 print("\n") 1159 } 1160 1161 // callers should be an internal detail, 1162 // (and is almost identical to Callers), 1163 // but widely used packages access it using linkname. 1164 // Notable members of the hall of shame include: 1165 // - github.com/phuslu/log 1166 // 1167 // Do not remove or change the type signature. 1168 // See go.dev/issue/67401. 1169 // 1170 //go:linkname callers 1171 func callers(skip int, pcbuf []uintptr) int { 1172 sp := sys.GetCallerSP() 1173 pc := sys.GetCallerPC() 1174 gp := getg() 1175 var n int 1176 systemstack(func() { 1177 var u unwinder 1178 u.initAt(pc, sp, 0, gp, unwindSilentErrors) 1179 n = tracebackPCs(&u, skip, pcbuf) 1180 }) 1181 return n 1182 } 1183 1184 func gcallers(gp *g, skip int, pcbuf []uintptr) int { 1185 var u unwinder 1186 u.init(gp, unwindSilentErrors) 1187 return tracebackPCs(&u, skip, pcbuf) 1188 } 1189 1190 // showframe reports whether the frame with the given characteristics should 1191 // be printed during a traceback. 1192 func showframe(sf srcFunc, gp *g, firstFrame bool, calleeID abi.FuncID) bool { 1193 mp := getg().m 1194 if mp.throwing >= throwTypeRuntime && gp != nil && (gp == mp.curg || gp == mp.caughtsig.ptr()) { 1195 return true 1196 } 1197 return showfuncinfo(sf, firstFrame, calleeID) 1198 } 1199 1200 // showfuncinfo reports whether a function with the given characteristics should 1201 // be printed during a traceback. 1202 func showfuncinfo(sf srcFunc, firstFrame bool, calleeID abi.FuncID) bool { 1203 level, _, _ := gotraceback() 1204 if level > 1 { 1205 // Show all frames. 1206 return true 1207 } 1208 1209 if sf.funcID == abi.FuncIDWrapper && elideWrapperCalling(calleeID) { 1210 return false 1211 } 1212 1213 // Always show runtime.runFinalizers and runtime.runCleanups as 1214 // context that this goroutine is running finalizers or cleanups, 1215 // otherwise there is no obvious indicator. 1216 // 1217 // TODO(prattmic): A more general approach would be to always show the 1218 // outermost frame (besides runtime.goexit), even if it is a runtime. 1219 // Hiding the outermost frame allows the apparent outermost frame to 1220 // change across different traces, which seems impossible. 1221 // 1222 // Unfortunately, implementing this requires looking ahead at the next 1223 // frame, which goes against traceback's incremental approach (see big 1224 // comment in traceback1). 1225 if sf.funcID == abi.FuncID_runFinalizers || sf.funcID == abi.FuncID_runCleanups { 1226 return true 1227 } 1228 1229 name := sf.name() 1230 1231 // Special case: always show runtime.gopanic frame 1232 // in the middle of a stack trace, so that we can 1233 // see the boundary between ordinary code and 1234 // panic-induced deferred code. 1235 // See golang.org/issue/5832. 1236 if name == "runtime.gopanic" && !firstFrame { 1237 return true 1238 } 1239 1240 return bytealg.IndexByteString(name, '.') >= 0 && (!stringslite.HasPrefix(name, "runtime.") || isExportedRuntime(name)) 1241 } 1242 1243 // isExportedRuntime reports whether name is an exported runtime function. 1244 // It is only for runtime functions, so ASCII A-Z is fine. 1245 func isExportedRuntime(name string) bool { 1246 // Check and remove package qualifier. 1247 name, found := stringslite.CutPrefix(name, "runtime.") 1248 if !found { 1249 return false 1250 } 1251 rcvr := "" 1252 1253 // Extract receiver type, if any. 1254 // For example, runtime.(*Func).Entry 1255 i := len(name) - 1 1256 for i >= 0 && name[i] != '.' { 1257 i-- 1258 } 1259 if i >= 0 { 1260 rcvr = name[:i] 1261 name = name[i+1:] 1262 // Remove parentheses and star for pointer receivers. 1263 if len(rcvr) >= 3 && rcvr[0] == '(' && rcvr[1] == '*' && rcvr[len(rcvr)-1] == ')' { 1264 rcvr = rcvr[2 : len(rcvr)-1] 1265 } 1266 } 1267 1268 // Exported functions and exported methods on exported types. 1269 return len(name) > 0 && 'A' <= name[0] && name[0] <= 'Z' && (len(rcvr) == 0 || 'A' <= rcvr[0] && rcvr[0] <= 'Z') 1270 } 1271 1272 // elideWrapperCalling reports whether a wrapper function that called 1273 // function id should be elided from stack traces. 1274 func elideWrapperCalling(id abi.FuncID) bool { 1275 // If the wrapper called a panic function instead of the 1276 // wrapped function, we want to include it in stacks. 1277 return !(id == abi.FuncID_gopanic || id == abi.FuncID_sigpanic || id == abi.FuncID_panicwrap) 1278 } 1279 1280 var gStatusStrings = [...]string{ 1281 _Gidle: "idle", 1282 _Grunnable: "runnable", 1283 _Grunning: "running", 1284 _Gsyscall: "syscall", 1285 _Gwaiting: "waiting", 1286 _Gdead: "dead", 1287 _Gcopystack: "copystack", 1288 _Gleaked: "leaked", 1289 _Gpreempted: "preempted", 1290 _Gdeadextra: "waiting for cgo callback", 1291 } 1292 1293 func goroutineheader(gp *g) { 1294 level, _, _ := gotraceback() 1295 1296 gpstatus := readgstatus(gp) 1297 1298 isScan := gpstatus&_Gscan != 0 1299 gpstatus &^= _Gscan // drop the scan bit 1300 1301 // Basic string status 1302 var status string 1303 if 0 <= gpstatus && gpstatus < uint32(len(gStatusStrings)) { 1304 status = gStatusStrings[gpstatus] 1305 } else { 1306 status = "???" 1307 } 1308 1309 // Override. 1310 if (gpstatus == _Gwaiting || gpstatus == _Gleaked) && gp.waitreason != waitReasonZero { 1311 status = gp.waitreason.String() 1312 } 1313 1314 // approx time the G is blocked, in minutes 1315 var waitfor int64 1316 if (gpstatus == _Gwaiting || gpstatus == _Gsyscall) && gp.waitsince != 0 { 1317 waitfor = (nanotime() - gp.waitsince) / 60e9 1318 } 1319 print("goroutine ", gp.goid) 1320 if gp.m != nil && gp.m.throwing >= throwTypeRuntime && gp == gp.m.curg || level >= 2 { 1321 print(" gp=", gp) 1322 if gp.m != nil { 1323 print(" m=", gp.m.id, " mp=", gp.m) 1324 } else { 1325 print(" m=nil") 1326 } 1327 } 1328 print(" [", status) 1329 if gpstatus == _Gleaked { 1330 print(" (leaked)") 1331 } 1332 if isScan { 1333 print(" (scan)") 1334 } 1335 if bubble := gp.bubble; bubble != nil && 1336 gpstatus == _Gwaiting && 1337 gp.waitreason.isIdleInSynctest() && 1338 !stringslite.HasSuffix(status, "(durable)") { 1339 // If this isn't a status where the name includes a (durable) 1340 // suffix to distinguish it from the non-durable form, add it here. 1341 print(" (durable)") 1342 } 1343 if waitfor >= 1 { 1344 print(", ", waitfor, " minutes") 1345 } 1346 if gp.lockedm != 0 { 1347 print(", locked to thread") 1348 } 1349 if bubble := gp.bubble; bubble != nil { 1350 print(", synctest bubble ", bubble.id) 1351 } 1352 print("]") 1353 if gp.labels != nil && debug.tracebacklabels.Load() == 1 { 1354 labels := (*label.Set)(gp.labels).List 1355 if len(labels) > 0 { 1356 print(" {") 1357 for i, kv := range labels { 1358 // Try to be nice and only quote the keys/values if one of them has characters that need quoting or escaping. 1359 printq := func(s string) { 1360 if tracebackStringNeedsQuoting(s) { 1361 print(quoted(s)) 1362 } else { 1363 print(s) 1364 } 1365 } 1366 printq(kv.Key) 1367 print(": ") 1368 printq(kv.Value) 1369 if i < len(labels)-1 { 1370 print(", ") 1371 } 1372 } 1373 print("}") 1374 } 1375 } 1376 print(":\n") 1377 } 1378 1379 func tracebackStringNeedsQuoting(s string) bool { 1380 for _, r := range s { 1381 if !('a' <= r && r <= 'z' || 1382 'A' <= r && r <= 'Z' || 1383 '0' <= r && r <= '9' || 1384 r == '.' || r == '/' || r == '_') { 1385 return true 1386 } 1387 } 1388 return false 1389 } 1390 1391 func tracebackothers(me *g) { 1392 tracebacksomeothers(me, func(*g) bool { return true }) 1393 } 1394 1395 func tracebacksomeothers(me *g, showf func(*g) bool) { 1396 level, _, _ := gotraceback() 1397 1398 // Show the current goroutine first, if we haven't already. 1399 curgp := getg().m.curg 1400 if curgp != nil && curgp != me { 1401 print("\n") 1402 goroutineheader(curgp) 1403 traceback(^uintptr(0), ^uintptr(0), 0, curgp) 1404 } 1405 1406 // We can't call locking forEachG here because this may be during fatal 1407 // throw/panic, where locking could be out-of-order or a direct 1408 // deadlock. 1409 // 1410 // Instead, use forEachGRace, which requires no locking. We don't lock 1411 // against concurrent creation of new Gs, but even with allglock we may 1412 // miss Gs created after this loop. 1413 forEachGRace(func(gp *g) { 1414 if gp == me || gp == curgp { 1415 return 1416 } 1417 if status := readgstatus(gp); status == _Gdead || status == _Gdeadextra { 1418 return 1419 } 1420 if !showf(gp) { 1421 return 1422 } 1423 if isSystemGoroutine(gp, false) && level < 2 { 1424 return 1425 } 1426 print("\n") 1427 goroutineheader(gp) 1428 // Note: gp.m == getg().m occurs when tracebackothers is called 1429 // from a signal handler initiated during a systemstack call. 1430 // The original G is still in the running state, and we want to 1431 // print its stack. 1432 // 1433 // There's a small window of time in exitsyscall where a goroutine could be 1434 // in _Grunning as it's exiting a syscall. This could be the case even if the 1435 // world is stopped or frozen. 1436 // 1437 // This is OK because the goroutine will not exit the syscall while the world 1438 // is stopped or frozen. This is also why it's safe to check syscallsp here, 1439 // and safe to take the goroutine's stack trace. The syscall path mutates 1440 // syscallsp only just before exiting the syscall. 1441 if gp.m != getg().m && readgstatus(gp)&^_Gscan == _Grunning && gp.syscallsp == 0 { 1442 print("\tgoroutine running on other thread; stack unavailable\n") 1443 printcreatedby(gp) 1444 } else { 1445 traceback(^uintptr(0), ^uintptr(0), 0, gp) 1446 } 1447 }) 1448 } 1449 1450 // tracebackHexdump hexdumps part of stk around frame.sp and frame.fp 1451 // for debugging purposes. If the address bad is included in the 1452 // hexdumped range, it will mark it as well. 1453 func tracebackHexdump(stk stack, frame *stkframe, bad uintptr) { 1454 const expand = 32 * goarch.PtrSize 1455 const maxExpand = 256 * goarch.PtrSize 1456 // Start around frame.sp. 1457 lo, hi := frame.sp, frame.sp 1458 // Expand to include frame.fp. 1459 if frame.fp != 0 && frame.fp < lo { 1460 lo = frame.fp 1461 } 1462 if frame.fp != 0 && frame.fp > hi { 1463 hi = frame.fp 1464 } 1465 // Expand a bit more. 1466 lo, hi = lo-expand, hi+expand 1467 // But don't go too far from frame.sp. 1468 if lo < frame.sp-maxExpand { 1469 lo = frame.sp - maxExpand 1470 } 1471 if hi > frame.sp+maxExpand { 1472 hi = frame.sp + maxExpand 1473 } 1474 // And don't go outside the stack bounds. 1475 if lo < stk.lo { 1476 lo = stk.lo 1477 } 1478 if hi > stk.hi { 1479 hi = stk.hi 1480 } 1481 1482 // Print the hex dump. 1483 print("stack: frame={sp:", hex(frame.sp), ", fp:", hex(frame.fp), "} stack=[", hex(stk.lo), ",", hex(stk.hi), ")\n") 1484 hexdumpWords(lo, hi-lo, func(p uintptr, m hexdumpMarker) { 1485 if p == frame.fp { 1486 m.start() 1487 println("FP") 1488 } 1489 if p == frame.sp { 1490 m.start() 1491 println("SP") 1492 } 1493 if p == bad { 1494 m.start() 1495 println("bad") 1496 } 1497 }) 1498 } 1499 1500 // isSystemGoroutine reports whether the goroutine g must be omitted 1501 // in stack dumps and deadlock detector. This is any goroutine that 1502 // starts at a runtime.* entry point, except for runtime.main, 1503 // runtime.handleAsyncEvent (wasm only) and sometimes 1504 // runtime.runFinalizers/runtime.runCleanups. 1505 // 1506 // If fixed is true, any goroutine that can vary between user and 1507 // system (that is, the finalizer goroutine) is considered a user 1508 // goroutine. 1509 func isSystemGoroutine(gp *g, fixed bool) bool { 1510 // Keep this in sync with internal/trace.IsSystemGoroutine. 1511 f := findfunc(gp.startpc) 1512 if !f.valid() { 1513 return false 1514 } 1515 if f.funcID == abi.FuncID_runtime_main || f.funcID == abi.FuncID_corostart || f.funcID == abi.FuncID_handleAsyncEvent { 1516 return false 1517 } 1518 if f.funcID == abi.FuncID_runFinalizers { 1519 // We include the finalizer goroutine if it's calling 1520 // back into user code. 1521 if fixed { 1522 // This goroutine can vary. In fixed mode, 1523 // always consider it a user goroutine. 1524 return false 1525 } 1526 return fingStatus.Load()&fingRunningFinalizer == 0 1527 } 1528 if f.funcID == abi.FuncID_runCleanups { 1529 // We include the cleanup goroutines if they're calling 1530 // back into user code. 1531 if fixed { 1532 // This goroutine can vary. In fixed mode, 1533 // always consider it a user goroutine. 1534 return false 1535 } 1536 return !gp.runningCleanups.Load() 1537 } 1538 return stringslite.HasPrefix(funcname(f), "runtime.") 1539 } 1540 1541 // SetCgoTraceback records three C functions to use to gather 1542 // traceback information from C code and to convert that traceback 1543 // information into symbolic information. These are used when printing 1544 // stack traces for a program that uses cgo. 1545 // 1546 // The traceback and context functions may be called from a signal 1547 // handler, and must therefore use only async-signal safe functions. 1548 // The symbolizer function may be called while the program is 1549 // crashing, and so must be cautious about using memory. None of the 1550 // functions may call back into Go. 1551 // 1552 // The context function will be called with a single argument, a 1553 // pointer to a struct: 1554 // 1555 // struct { 1556 // Context uintptr 1557 // } 1558 // 1559 // In C syntax, this struct will be 1560 // 1561 // struct { 1562 // uintptr_t Context; 1563 // }; 1564 // 1565 // If the Context field is 0, the context function is being called to 1566 // record the current traceback context. It should record in the 1567 // Context field whatever information is needed about the current 1568 // point of execution to later produce a stack trace, probably the 1569 // stack pointer and PC. In this case the context function will be 1570 // called from C code. 1571 // 1572 // If the Context field is not 0, then it is a value returned by a 1573 // previous call to the context function. This case is called when the 1574 // context is no longer needed; that is, when the Go code is returning 1575 // to its C code caller. This permits the context function to release 1576 // any associated resources. 1577 // 1578 // While it would be correct for the context function to record a 1579 // complete a stack trace whenever it is called, and simply copy that 1580 // out in the traceback function, in a typical program the context 1581 // function will be called many times without ever recording a 1582 // traceback for that context. Recording a complete stack trace in a 1583 // call to the context function is likely to be inefficient. 1584 // 1585 // The traceback function will be called with a single argument, a 1586 // pointer to a struct: 1587 // 1588 // struct { 1589 // Context uintptr 1590 // SigContext uintptr 1591 // Buf *uintptr 1592 // Max uintptr 1593 // } 1594 // 1595 // In C syntax, this struct will be 1596 // 1597 // struct { 1598 // uintptr_t Context; 1599 // uintptr_t SigContext; 1600 // uintptr_t* Buf; 1601 // uintptr_t Max; 1602 // }; 1603 // 1604 // The Context field will be zero to gather a traceback from the 1605 // current program execution point. In this case, the traceback 1606 // function will be called from C code. 1607 // 1608 // Otherwise Context will be a value previously returned by a call to 1609 // the context function. The traceback function should gather a stack 1610 // trace from that saved point in the program execution. The traceback 1611 // function may be called from an execution thread other than the one 1612 // that recorded the context, but only when the context is known to be 1613 // valid and unchanging. The traceback function may also be called 1614 // deeper in the call stack on the same thread that recorded the 1615 // context. The traceback function may be called multiple times with 1616 // the same Context value; it will usually be appropriate to cache the 1617 // result, if possible, the first time this is called for a specific 1618 // context value. 1619 // 1620 // If the traceback function is called from a signal handler on a Unix 1621 // system, SigContext will be the signal context argument passed to 1622 // the signal handler (a C ucontext_t* cast to uintptr_t). This may be 1623 // used to start tracing at the point where the signal occurred. If 1624 // the traceback function is not called from a signal handler, 1625 // SigContext will be zero. 1626 // 1627 // Buf is where the traceback information should be stored. It should 1628 // be PC values, such that Buf[0] is the PC of the caller, Buf[1] is 1629 // the PC of that function's caller, and so on. Max is the maximum 1630 // number of entries to store. The function should store a zero to 1631 // indicate the top of the stack, or that the caller is on a different 1632 // stack, presumably a Go stack. 1633 // 1634 // Unlike runtime.Callers, the PC values returned should, when passed 1635 // to the symbolizer function, return the file/line of the call 1636 // instruction. No additional subtraction is required or appropriate. 1637 // 1638 // On all platforms, the traceback function is invoked when a call from 1639 // Go to C to Go requests a stack trace. On linux/amd64, linux/ppc64le, 1640 // linux/arm64, and freebsd/amd64, the traceback function is also invoked 1641 // when a signal is received by a thread that is executing a cgo call. 1642 // The traceback function should not make assumptions about when it is 1643 // called, as future versions of Go may make additional calls. 1644 // 1645 // The symbolizer function will be called with a single argument, a 1646 // pointer to a struct: 1647 // 1648 // struct { 1649 // PC uintptr // program counter to fetch information for 1650 // File *byte // file name (NUL terminated) 1651 // Lineno uintptr // line number 1652 // Func *byte // function name (NUL terminated) 1653 // Entry uintptr // function entry point 1654 // More uintptr // set non-zero if more info for this PC 1655 // Data uintptr // unused by runtime, available for function 1656 // } 1657 // 1658 // In C syntax, this struct will be 1659 // 1660 // struct { 1661 // uintptr_t PC; 1662 // char* File; 1663 // uintptr_t Lineno; 1664 // char* Func; 1665 // uintptr_t Entry; 1666 // uintptr_t More; 1667 // uintptr_t Data; 1668 // }; 1669 // 1670 // The PC field will be a value returned by a call to the traceback 1671 // function. 1672 // 1673 // The first time the function is called for a particular traceback, 1674 // all the fields except PC will be 0. The function should fill in the 1675 // other fields if possible, setting them to 0/nil if the information 1676 // is not available. The Data field may be used to store any useful 1677 // information across calls. The More field should be set to non-zero 1678 // if there is more information for this PC, zero otherwise. If More 1679 // is set non-zero, the function will be called again with the same 1680 // PC, and may return different information (this is intended for use 1681 // with inlined functions). If More is zero, the function will be 1682 // called with the next PC value in the traceback. When the traceback 1683 // is complete, the function will be called once more with PC set to 1684 // zero; this may be used to free any information. Each call will 1685 // leave the fields of the struct set to the same values they had upon 1686 // return, except for the PC field when the More field is zero. The 1687 // function must not keep a copy of the struct pointer between calls. 1688 // 1689 // When calling SetCgoTraceback, the version argument is the version 1690 // number of the structs that the functions expect to receive. 1691 // Currently this must be zero. 1692 // 1693 // The symbolizer function may be nil, in which case the results of 1694 // the traceback function will be displayed as numbers. If the 1695 // traceback function is nil, the symbolizer function will never be 1696 // called. The context function may be nil, in which case the 1697 // traceback function will only be called with the context field set 1698 // to zero. If the context function is nil, then calls from Go to C 1699 // to Go will not show a traceback for the C portion of the call stack. 1700 // 1701 // SetCgoTraceback should be called only once, ideally from an init function. 1702 func SetCgoTraceback(version int, traceback, context, symbolizer unsafe.Pointer) { 1703 if version != 0 { 1704 panic("unsupported version") 1705 } 1706 1707 if cgoTraceback != nil && cgoTraceback != traceback || 1708 cgoContext != nil && cgoContext != context || 1709 cgoSymbolizer != nil && cgoSymbolizer != symbolizer { 1710 panic("call SetCgoTraceback only once") 1711 } 1712 1713 cgoTraceback = traceback 1714 cgoContext = context 1715 cgoSymbolizer = symbolizer 1716 1717 if _cgo_set_traceback_functions != nil { 1718 type cgoSetTracebackFunctionsArg struct { 1719 traceback unsafe.Pointer 1720 context unsafe.Pointer 1721 symbolizer unsafe.Pointer 1722 } 1723 arg := cgoSetTracebackFunctionsArg{ 1724 traceback: traceback, 1725 context: context, 1726 symbolizer: symbolizer, 1727 } 1728 cgocall(_cgo_set_traceback_functions, noescape(unsafe.Pointer(&arg))) 1729 } 1730 } 1731 1732 var cgoTraceback unsafe.Pointer 1733 var cgoContext unsafe.Pointer 1734 var cgoSymbolizer unsafe.Pointer 1735 1736 func cgoTracebackAvailable() bool { 1737 // - The traceback function must be registered via SetCgoTraceback. 1738 // - This must be a cgo binary (providing _cgo_call_traceback_function). 1739 return cgoTraceback != nil && _cgo_call_traceback_function != nil 1740 } 1741 1742 func cgoSymbolizerAvailable() bool { 1743 // - The symbolizer function must be registered via SetCgoTraceback. 1744 // - This must be a cgo binary (providing _cgo_call_symbolizer_function). 1745 return cgoSymbolizer != nil && _cgo_call_symbolizer_function != nil 1746 } 1747 1748 // cgoTracebackArg is the type passed to cgoTraceback. 1749 type cgoTracebackArg struct { 1750 context uintptr 1751 sigContext uintptr 1752 buf *uintptr 1753 max uintptr 1754 } 1755 1756 // cgoContextArg is the type passed to the context function. 1757 type cgoContextArg struct { 1758 context uintptr 1759 } 1760 1761 // cgoSymbolizerArg is the type passed to cgoSymbolizer. 1762 type cgoSymbolizerArg struct { 1763 pc uintptr 1764 file *byte 1765 lineno uintptr 1766 funcName *byte 1767 entry uintptr 1768 more uintptr 1769 data uintptr 1770 } 1771 1772 // printCgoTraceback prints a traceback of callers. 1773 func printCgoTraceback(callers *cgoCallers) { 1774 if !cgoSymbolizerAvailable() { 1775 for _, c := range callers { 1776 if c == 0 { 1777 break 1778 } 1779 print("non-Go function at pc=", hex(c), "\n") 1780 } 1781 return 1782 } 1783 1784 commitFrame := func() (pr, stop bool) { return true, false } 1785 var arg cgoSymbolizerArg 1786 for _, c := range callers { 1787 if c == 0 { 1788 break 1789 } 1790 printOneCgoTraceback(c, commitFrame, &arg) 1791 } 1792 arg.pc = 0 1793 callCgoSymbolizer(&arg) 1794 } 1795 1796 // printOneCgoTraceback prints the traceback of a single cgo caller. 1797 // This can print more than one line because of inlining. 1798 // It returns the "stop" result of commitFrame. 1799 // 1800 // Preconditions: cgoSymbolizerAvailable returns true. 1801 func printOneCgoTraceback(pc uintptr, commitFrame func() (pr, stop bool), arg *cgoSymbolizerArg) bool { 1802 arg.pc = pc 1803 for { 1804 if pr, stop := commitFrame(); stop { 1805 return true 1806 } else if !pr { 1807 continue 1808 } 1809 1810 callCgoSymbolizer(arg) 1811 if arg.funcName != nil { 1812 // Note that we don't print any argument 1813 // information here, not even parentheses. 1814 // The symbolizer must add that if appropriate. 1815 println(gostringnocopy(arg.funcName)) 1816 } else { 1817 println("non-Go function") 1818 } 1819 print("\t") 1820 if arg.file != nil { 1821 print(gostringnocopy(arg.file), ":", arg.lineno, " ") 1822 } 1823 print("pc=", hex(pc), "\n") 1824 if arg.more == 0 { 1825 return false 1826 } 1827 } 1828 } 1829 1830 // callCgoSymbolizer calls the cgoSymbolizer function. 1831 // 1832 // Preconditions: cgoSymbolizerAvailable returns true. 1833 func callCgoSymbolizer(arg *cgoSymbolizerArg) { 1834 call := cgocall 1835 if panicking.Load() > 0 || getg().m.curg != getg() { 1836 // We do not want to call into the scheduler when panicking 1837 // or when on the system stack. 1838 call = asmcgocall 1839 } 1840 if msanenabled { 1841 msanwrite(unsafe.Pointer(arg), unsafe.Sizeof(cgoSymbolizerArg{})) 1842 } 1843 if asanenabled { 1844 asanwrite(unsafe.Pointer(arg), unsafe.Sizeof(cgoSymbolizerArg{})) 1845 } 1846 call(_cgo_call_symbolizer_function, noescape(unsafe.Pointer(arg))) 1847 } 1848 1849 // cgoContextPCs gets the PC values from a cgo traceback. 1850 // 1851 // Preconditions: cgoTracebackAvailable returns true. 1852 func cgoContextPCs(ctxt uintptr, buf []uintptr) { 1853 call := cgocall 1854 if panicking.Load() > 0 || getg().m.curg != getg() { 1855 // We do not want to call into the scheduler when panicking 1856 // or when on the system stack. 1857 call = asmcgocall 1858 } 1859 arg := cgoTracebackArg{ 1860 context: ctxt, 1861 buf: (*uintptr)(noescape(unsafe.Pointer(&buf[0]))), 1862 max: uintptr(len(buf)), 1863 } 1864 if msanenabled { 1865 msanwrite(unsafe.Pointer(&arg), unsafe.Sizeof(arg)) 1866 } 1867 if asanenabled { 1868 asanwrite(unsafe.Pointer(&arg), unsafe.Sizeof(arg)) 1869 } 1870 call(_cgo_call_traceback_function, noescape(unsafe.Pointer(&arg))) 1871 } 1872