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/bytealg" 9 "internal/goarch" 10 "runtime/internal/atomic" 11 "runtime/internal/sys" 12 "unsafe" 13 ) 14 15 // The code in this file implements stack trace walking for all architectures. 16 // The most important fact about a given architecture is whether it uses a link register. 17 // On systems with link registers, the prologue for a non-leaf function stores the 18 // incoming value of LR at the bottom of the newly allocated stack frame. 19 // On systems without link registers (x86), the architecture pushes a return PC during 20 // the call instruction, so the return PC ends up above the stack frame. 21 // In this file, the return PC is always called LR, no matter how it was found. 22 23 const usesLR = sys.MinFrameSize > 0 24 25 // Generic traceback. Handles runtime stack prints (pcbuf == nil), 26 // the runtime.Callers function (pcbuf != nil), as well as the garbage 27 // collector (callback != nil). A little clunky to merge these, but avoids 28 // duplicating the code and all its subtlety. 29 // 30 // The skip argument is only valid with pcbuf != nil and counts the number 31 // of logical frames to skip rather than physical frames (with inlining, a 32 // PC in pcbuf can represent multiple calls). 33 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 { 34 if skip > 0 && callback != nil { 35 throw("gentraceback callback cannot be used with non-zero skip") 36 } 37 38 // Don't call this "g"; it's too easy get "g" and "gp" confused. 39 if ourg := getg(); ourg == gp && ourg == ourg.m.curg { 40 // The starting sp has been passed in as a uintptr, and the caller may 41 // have other uintptr-typed stack references as well. 42 // If during one of the calls that got us here or during one of the 43 // callbacks below the stack must be grown, all these uintptr references 44 // to the stack will not be updated, and gentraceback will continue 45 // to inspect the old stack memory, which may no longer be valid. 46 // Even if all the variables were updated correctly, it is not clear that 47 // we want to expose a traceback that begins on one stack and ends 48 // on another stack. That could confuse callers quite a bit. 49 // Instead, we require that gentraceback and any other function that 50 // accepts an sp for the current goroutine (typically obtained by 51 // calling getcallersp) must not run on that goroutine's stack but 52 // instead on the g0 stack. 53 throw("gentraceback cannot trace user goroutine on its own stack") 54 } 55 level, _, _ := gotraceback() 56 57 var ctxt *funcval // Context pointer for unstarted goroutines. See issue #25897. 58 59 if pc0 == ^uintptr(0) && sp0 == ^uintptr(0) { // Signal to fetch saved values from gp. 60 if gp.syscallsp != 0 { 61 pc0 = gp.syscallpc 62 sp0 = gp.syscallsp 63 if usesLR { 64 lr0 = 0 65 } 66 } else { 67 pc0 = gp.sched.pc 68 sp0 = gp.sched.sp 69 if usesLR { 70 lr0 = gp.sched.lr 71 } 72 ctxt = (*funcval)(gp.sched.ctxt) 73 } 74 } 75 76 nprint := 0 77 var frame stkframe 78 frame.pc = pc0 79 frame.sp = sp0 80 if usesLR { 81 frame.lr = lr0 82 } 83 waspanic := false 84 cgoCtxt := gp.cgoCtxt 85 stack := gp.stack 86 printing := pcbuf == nil && callback == nil 87 88 // If the PC is zero, it's likely a nil function call. 89 // Start in the caller's frame. 90 if frame.pc == 0 { 91 if usesLR { 92 frame.pc = *(*uintptr)(unsafe.Pointer(frame.sp)) 93 frame.lr = 0 94 } else { 95 frame.pc = uintptr(*(*uintptr)(unsafe.Pointer(frame.sp))) 96 frame.sp += goarch.PtrSize 97 } 98 } 99 100 // runtime/internal/atomic functions call into kernel helpers on 101 // arm < 7. See runtime/internal/atomic/sys_linux_arm.s. 102 // 103 // Start in the caller's frame. 104 if GOARCH == "arm" && goarm < 7 && GOOS == "linux" && frame.pc&0xffff0000 == 0xffff0000 { 105 // Note that the calls are simple BL without pushing the return 106 // address, so we use LR directly. 107 // 108 // The kernel helpers are frameless leaf functions, so SP and 109 // LR are not touched. 110 frame.pc = frame.lr 111 frame.lr = 0 112 } 113 114 f := findfunc(frame.pc) 115 if !f.valid() { 116 if callback != nil || printing { 117 print("runtime: g ", gp.goid, ": unknown pc ", hex(frame.pc), "\n") 118 tracebackHexdump(stack, &frame, 0) 119 } 120 if callback != nil { 121 throw("unknown pc") 122 } 123 return 0 124 } 125 frame.fn = f 126 127 var cache pcvalueCache 128 129 lastFuncID := funcID_normal 130 n := 0 131 for n < max { 132 // Typically: 133 // pc is the PC of the running function. 134 // sp is the stack pointer at that program counter. 135 // fp is the frame pointer (caller's stack pointer) at that program counter, or nil if unknown. 136 // stk is the stack containing sp. 137 // The caller's program counter is lr, unless lr is zero, in which case it is *(uintptr*)sp. 138 f = frame.fn 139 if f.pcsp == 0 { 140 // No frame information, must be external function, like race support. 141 // See golang.org/issue/13568. 142 break 143 } 144 145 // Compute function info flags. 146 flag := f.flag 147 if f.funcID == funcID_cgocallback { 148 // cgocallback does write SP to switch from the g0 to the curg stack, 149 // but it carefully arranges that during the transition BOTH stacks 150 // have cgocallback frame valid for unwinding through. 151 // So we don't need to exclude it with the other SP-writing functions. 152 flag &^= funcFlag_SPWRITE 153 } 154 if frame.pc == pc0 && frame.sp == sp0 && pc0 == gp.syscallpc && sp0 == gp.syscallsp { 155 // Some Syscall functions write to SP, but they do so only after 156 // saving the entry PC/SP using entersyscall. 157 // Since we are using the entry PC/SP, the later SP write doesn't matter. 158 flag &^= funcFlag_SPWRITE 159 } 160 161 // Found an actual function. 162 // Derive frame pointer and link register. 163 if frame.fp == 0 { 164 // Jump over system stack transitions. If we're on g0 and there's a user 165 // goroutine, try to jump. Otherwise this is a regular call. 166 if flags&_TraceJumpStack != 0 && gp == gp.m.g0 && gp.m.curg != nil { 167 switch f.funcID { 168 case funcID_morestack: 169 // morestack does not return normally -- newstack() 170 // gogo's to curg.sched. Match that. 171 // This keeps morestack() from showing up in the backtrace, 172 // but that makes some sense since it'll never be returned 173 // to. 174 frame.pc = gp.m.curg.sched.pc 175 frame.fn = findfunc(frame.pc) 176 f = frame.fn 177 flag = f.flag 178 frame.lr = gp.m.curg.sched.lr 179 frame.sp = gp.m.curg.sched.sp 180 stack = gp.m.curg.stack 181 cgoCtxt = gp.m.curg.cgoCtxt 182 case funcID_systemstack: 183 // systemstack returns normally, so just follow the 184 // stack transition. 185 if usesLR && funcspdelta(f, frame.pc, &cache) == 0 { 186 // We're at the function prologue and the stack 187 // switch hasn't happened, or epilogue where we're 188 // about to return. Just unwind normally. 189 // Do this only on LR machines because on x86 190 // systemstack doesn't have an SP delta (the CALL 191 // instruction opens the frame), therefore no way 192 // to check. 193 flag &^= funcFlag_SPWRITE 194 break 195 } 196 frame.sp = gp.m.curg.sched.sp 197 stack = gp.m.curg.stack 198 cgoCtxt = gp.m.curg.cgoCtxt 199 flag &^= funcFlag_SPWRITE 200 } 201 } 202 frame.fp = frame.sp + uintptr(funcspdelta(f, frame.pc, &cache)) 203 if !usesLR { 204 // On x86, call instruction pushes return PC before entering new function. 205 frame.fp += goarch.PtrSize 206 } 207 } 208 var flr funcInfo 209 if flag&funcFlag_TOPFRAME != 0 { 210 // This function marks the top of the stack. Stop the traceback. 211 frame.lr = 0 212 flr = funcInfo{} 213 } else if flag&funcFlag_SPWRITE != 0 && (callback == nil || n > 0) { 214 // The function we are in does a write to SP that we don't know 215 // how to encode in the spdelta table. Examples include context 216 // switch routines like runtime.gogo but also any code that switches 217 // to the g0 stack to run host C code. Since we can't reliably unwind 218 // the SP (we might not even be on the stack we think we are), 219 // we stop the traceback here. 220 // This only applies for profiling signals (callback == nil). 221 // 222 // For a GC stack traversal (callback != nil), we should only see 223 // a function when it has voluntarily preempted itself on entry 224 // during the stack growth check. In that case, the function has 225 // not yet had a chance to do any writes to SP and is safe to unwind. 226 // isAsyncSafePoint does not allow assembly functions to be async preempted, 227 // and preemptPark double-checks that SPWRITE functions are not async preempted. 228 // So for GC stack traversal we leave things alone (this if body does not execute for n == 0) 229 // at the bottom frame of the stack. But farther up the stack we'd better not 230 // find any. 231 if callback != nil { 232 println("traceback: unexpected SPWRITE function", funcname(f)) 233 throw("traceback") 234 } 235 frame.lr = 0 236 flr = funcInfo{} 237 } else { 238 var lrPtr uintptr 239 if usesLR { 240 if n == 0 && frame.sp < frame.fp || frame.lr == 0 { 241 lrPtr = frame.sp 242 frame.lr = *(*uintptr)(unsafe.Pointer(lrPtr)) 243 } 244 } else { 245 if frame.lr == 0 { 246 lrPtr = frame.fp - goarch.PtrSize 247 frame.lr = uintptr(*(*uintptr)(unsafe.Pointer(lrPtr))) 248 } 249 } 250 flr = findfunc(frame.lr) 251 if !flr.valid() { 252 // This happens if you get a profiling interrupt at just the wrong time. 253 // In that context it is okay to stop early. 254 // But if callback is set, we're doing a garbage collection and must 255 // get everything, so crash loudly. 256 doPrint := printing 257 if doPrint && gp.m.incgo && f.funcID == funcID_sigpanic { 258 // We can inject sigpanic 259 // calls directly into C code, 260 // in which case we'll see a C 261 // return PC. Don't complain. 262 doPrint = false 263 } 264 if callback != nil || doPrint { 265 print("runtime: g ", gp.goid, ": unexpected return pc for ", funcname(f), " called from ", hex(frame.lr), "\n") 266 tracebackHexdump(stack, &frame, lrPtr) 267 } 268 if callback != nil { 269 throw("unknown caller pc") 270 } 271 } 272 } 273 274 frame.varp = frame.fp 275 if !usesLR { 276 // On x86, call instruction pushes return PC before entering new function. 277 frame.varp -= goarch.PtrSize 278 } 279 280 // For architectures with frame pointers, if there's 281 // a frame, then there's a saved frame pointer here. 282 // 283 // NOTE: This code is not as general as it looks. 284 // On x86, the ABI is to save the frame pointer word at the 285 // top of the stack frame, so we have to back down over it. 286 // On arm64, the frame pointer should be at the bottom of 287 // the stack (with R29 (aka FP) = RSP), in which case we would 288 // not want to do the subtraction here. But we started out without 289 // any frame pointer, and when we wanted to add it, we didn't 290 // want to break all the assembly doing direct writes to 8(RSP) 291 // to set the first parameter to a called function. 292 // So we decided to write the FP link *below* the stack pointer 293 // (with R29 = RSP - 8 in Go functions). 294 // This is technically ABI-compatible but not standard. 295 // And it happens to end up mimicking the x86 layout. 296 // Other architectures may make different decisions. 297 if frame.varp > frame.sp && framepointer_enabled { 298 frame.varp -= goarch.PtrSize 299 } 300 301 // Derive size of arguments. 302 // Most functions have a fixed-size argument block, 303 // so we can use metadata about the function f. 304 // Not all, though: there are some variadic functions 305 // in package runtime and reflect, and for those we use call-specific 306 // metadata recorded by f's caller. 307 if callback != nil || printing { 308 frame.argp = frame.fp + sys.MinFrameSize 309 var ok bool 310 frame.arglen, frame.argmap, ok = getArgInfoFast(f, callback != nil) 311 if !ok { 312 frame.arglen, frame.argmap = getArgInfo(&frame, f, callback != nil, ctxt) 313 } 314 } 315 ctxt = nil // ctxt is only needed to get arg maps for the topmost frame 316 317 // Determine frame's 'continuation PC', where it can continue. 318 // Normally this is the return address on the stack, but if sigpanic 319 // is immediately below this function on the stack, then the frame 320 // stopped executing due to a trap, and frame.pc is probably not 321 // a safe point for looking up liveness information. In this panicking case, 322 // the function either doesn't return at all (if it has no defers or if the 323 // defers do not recover) or it returns from one of the calls to 324 // deferproc a second time (if the corresponding deferred func recovers). 325 // In the latter case, use a deferreturn call site as the continuation pc. 326 frame.continpc = frame.pc 327 if waspanic { 328 if frame.fn.deferreturn != 0 { 329 frame.continpc = frame.fn.entry() + uintptr(frame.fn.deferreturn) + 1 330 // Note: this may perhaps keep return variables alive longer than 331 // strictly necessary, as we are using "function has a defer statement" 332 // as a proxy for "function actually deferred something". It seems 333 // to be a minor drawback. (We used to actually look through the 334 // gp._defer for a defer corresponding to this function, but that 335 // is hard to do with defer records on the stack during a stack copy.) 336 // Note: the +1 is to offset the -1 that 337 // stack.go:getStackMap does to back up a return 338 // address make sure the pc is in the CALL instruction. 339 } else { 340 frame.continpc = 0 341 } 342 } 343 344 if callback != nil { 345 if !callback((*stkframe)(noescape(unsafe.Pointer(&frame))), v) { 346 return n 347 } 348 } 349 350 if pcbuf != nil { 351 pc := frame.pc 352 // backup to CALL instruction to read inlining info (same logic as below) 353 tracepc := pc 354 // Normally, pc is a return address. In that case, we want to look up 355 // file/line information using pc-1, because that is the pc of the 356 // call instruction (more precisely, the last byte of the call instruction). 357 // Callers expect the pc buffer to contain return addresses and do the 358 // same -1 themselves, so we keep pc unchanged. 359 // When the pc is from a signal (e.g. profiler or segv) then we want 360 // to look up file/line information using pc, and we store pc+1 in the 361 // pc buffer so callers can unconditionally subtract 1 before looking up. 362 // See issue 34123. 363 // The pc can be at function entry when the frame is initialized without 364 // actually running code, like runtime.mstart. 365 if (n == 0 && flags&_TraceTrap != 0) || waspanic || pc == f.entry() { 366 pc++ 367 } else { 368 tracepc-- 369 } 370 371 // If there is inlining info, record the inner frames. 372 if inldata := funcdata(f, _FUNCDATA_InlTree); inldata != nil { 373 inltree := (*[1 << 20]inlinedCall)(inldata) 374 for { 375 ix := pcdatavalue(f, _PCDATA_InlTreeIndex, tracepc, &cache) 376 if ix < 0 { 377 break 378 } 379 if inltree[ix].funcID == funcID_wrapper && elideWrapperCalling(lastFuncID) { 380 // ignore wrappers 381 } else if skip > 0 { 382 skip-- 383 } else if n < max { 384 (*[1 << 20]uintptr)(unsafe.Pointer(pcbuf))[n] = pc 385 n++ 386 } 387 lastFuncID = inltree[ix].funcID 388 // Back up to an instruction in the "caller". 389 tracepc = frame.fn.entry() + uintptr(inltree[ix].parentPc) 390 pc = tracepc + 1 391 } 392 } 393 // Record the main frame. 394 if f.funcID == funcID_wrapper && elideWrapperCalling(lastFuncID) { 395 // Ignore wrapper functions (except when they trigger panics). 396 } else if skip > 0 { 397 skip-- 398 } else if n < max { 399 (*[1 << 20]uintptr)(unsafe.Pointer(pcbuf))[n] = pc 400 n++ 401 } 402 lastFuncID = f.funcID 403 n-- // offset n++ below 404 } 405 406 if printing { 407 // assume skip=0 for printing. 408 // 409 // Never elide wrappers if we haven't printed 410 // any frames. And don't elide wrappers that 411 // called panic rather than the wrapped 412 // function. Otherwise, leave them out. 413 414 // backup to CALL instruction to read inlining info (same logic as below) 415 tracepc := frame.pc 416 if (n > 0 || flags&_TraceTrap == 0) && frame.pc > f.entry() && !waspanic { 417 tracepc-- 418 } 419 // If there is inlining info, print the inner frames. 420 if inldata := funcdata(f, _FUNCDATA_InlTree); inldata != nil { 421 inltree := (*[1 << 20]inlinedCall)(inldata) 422 var inlFunc _func 423 inlFuncInfo := funcInfo{&inlFunc, f.datap} 424 for { 425 ix := pcdatavalue(f, _PCDATA_InlTreeIndex, tracepc, nil) 426 if ix < 0 { 427 break 428 } 429 430 // Create a fake _func for the 431 // inlined function. 432 inlFunc.nameoff = inltree[ix].func_ 433 inlFunc.funcID = inltree[ix].funcID 434 435 if (flags&_TraceRuntimeFrames) != 0 || showframe(inlFuncInfo, gp, nprint == 0, inlFuncInfo.funcID, lastFuncID) { 436 name := funcname(inlFuncInfo) 437 file, line := funcline(f, tracepc) 438 print(name, "(...)\n") 439 print("\t", file, ":", line, "\n") 440 nprint++ 441 } 442 lastFuncID = inltree[ix].funcID 443 // Back up to an instruction in the "caller". 444 tracepc = frame.fn.entry() + uintptr(inltree[ix].parentPc) 445 } 446 } 447 if (flags&_TraceRuntimeFrames) != 0 || showframe(f, gp, nprint == 0, f.funcID, lastFuncID) { 448 // Print during crash. 449 // main(0x1, 0x2, 0x3) 450 // /home/rsc/go/src/runtime/x.go:23 +0xf 451 // 452 name := funcname(f) 453 file, line := funcline(f, tracepc) 454 if name == "runtime.gopanic" { 455 name = "panic" 456 } 457 print(name, "(") 458 argp := unsafe.Pointer(frame.argp) 459 printArgs(f, argp, tracepc) 460 print(")\n") 461 print("\t", file, ":", line) 462 if frame.pc > f.entry() { 463 print(" +", hex(frame.pc-f.entry())) 464 } 465 if gp.m != nil && gp.m.throwing >= throwTypeRuntime && gp == gp.m.curg || level >= 2 { 466 print(" fp=", hex(frame.fp), " sp=", hex(frame.sp), " pc=", hex(frame.pc)) 467 } 468 print("\n") 469 nprint++ 470 } 471 lastFuncID = f.funcID 472 } 473 n++ 474 475 if f.funcID == funcID_cgocallback && len(cgoCtxt) > 0 { 476 ctxt := cgoCtxt[len(cgoCtxt)-1] 477 cgoCtxt = cgoCtxt[:len(cgoCtxt)-1] 478 479 // skip only applies to Go frames. 480 // callback != nil only used when we only care 481 // about Go frames. 482 if skip == 0 && callback == nil { 483 n = tracebackCgoContext(pcbuf, printing, ctxt, n, max) 484 } 485 } 486 487 waspanic = f.funcID == funcID_sigpanic 488 injectedCall := waspanic || f.funcID == funcID_asyncPreempt || f.funcID == funcID_debugCallV2 489 490 // Do not unwind past the bottom of the stack. 491 if !flr.valid() { 492 break 493 } 494 495 if frame.pc == frame.lr && frame.sp == frame.fp { 496 // If the next frame is identical to the current frame, we cannot make progress. 497 print("runtime: traceback stuck. pc=", hex(frame.pc), " sp=", hex(frame.sp), "\n") 498 tracebackHexdump(stack, &frame, frame.sp) 499 throw("traceback stuck") 500 } 501 502 // Unwind to next frame. 503 frame.fn = flr 504 frame.pc = frame.lr 505 frame.lr = 0 506 frame.sp = frame.fp 507 frame.fp = 0 508 frame.argmap = nil 509 510 // On link register architectures, sighandler saves the LR on stack 511 // before faking a call. 512 if usesLR && injectedCall { 513 x := *(*uintptr)(unsafe.Pointer(frame.sp)) 514 frame.sp += alignUp(sys.MinFrameSize, sys.StackAlign) 515 f = findfunc(frame.pc) 516 frame.fn = f 517 if !f.valid() { 518 frame.pc = x 519 } else if funcspdelta(f, frame.pc, &cache) == 0 { 520 frame.lr = x 521 } 522 } 523 } 524 525 if printing { 526 n = nprint 527 } 528 529 // Note that panic != nil is okay here: there can be leftover panics, 530 // because the defers on the panic stack do not nest in frame order as 531 // they do on the defer stack. If you have: 532 // 533 // frame 1 defers d1 534 // frame 2 defers d2 535 // frame 3 defers d3 536 // frame 4 panics 537 // frame 4's panic starts running defers 538 // frame 5, running d3, defers d4 539 // frame 5 panics 540 // frame 5's panic starts running defers 541 // frame 6, running d4, garbage collects 542 // frame 6, running d2, garbage collects 543 // 544 // During the execution of d4, the panic stack is d4 -> d3, which 545 // is nested properly, and we'll treat frame 3 as resumable, because we 546 // can find d3. (And in fact frame 3 is resumable. If d4 recovers 547 // and frame 5 continues running, d3, d3 can recover and we'll 548 // resume execution in (returning from) frame 3.) 549 // 550 // During the execution of d2, however, the panic stack is d2 -> d3, 551 // which is inverted. The scan will match d2 to frame 2 but having 552 // d2 on the stack until then means it will not match d3 to frame 3. 553 // This is okay: if we're running d2, then all the defers after d2 have 554 // completed and their corresponding frames are dead. Not finding d3 555 // for frame 3 means we'll set frame 3's continpc == 0, which is correct 556 // (frame 3 is dead). At the end of the walk the panic stack can thus 557 // contain defers (d3 in this case) for dead frames. The inversion here 558 // always indicates a dead frame, and the effect of the inversion on the 559 // scan is to hide those dead frames, so the scan is still okay: 560 // what's left on the panic stack are exactly (and only) the dead frames. 561 // 562 // We require callback != nil here because only when callback != nil 563 // do we know that gentraceback is being called in a "must be correct" 564 // context as opposed to a "best effort" context. The tracebacks with 565 // callbacks only happen when everything is stopped nicely. 566 // At other times, such as when gathering a stack for a profiling signal 567 // or when printing a traceback during a crash, everything may not be 568 // stopped nicely, and the stack walk may not be able to complete. 569 if callback != nil && n < max && frame.sp != gp.stktopsp { 570 print("runtime: g", gp.goid, ": frame.sp=", hex(frame.sp), " top=", hex(gp.stktopsp), "\n") 571 print("\tstack=[", hex(gp.stack.lo), "-", hex(gp.stack.hi), "] n=", n, " max=", max, "\n") 572 throw("traceback did not unwind completely") 573 } 574 575 return n 576 } 577 578 // printArgs prints function arguments in traceback. 579 func printArgs(f funcInfo, argp unsafe.Pointer, pc uintptr) { 580 // The "instruction" of argument printing is encoded in _FUNCDATA_ArgInfo. 581 // See cmd/compile/internal/ssagen.emitArgInfo for the description of the 582 // encoding. 583 // These constants need to be in sync with the compiler. 584 const ( 585 _endSeq = 0xff 586 _startAgg = 0xfe 587 _endAgg = 0xfd 588 _dotdotdot = 0xfc 589 _offsetTooLarge = 0xfb 590 ) 591 592 const ( 593 limit = 10 // print no more than 10 args/components 594 maxDepth = 5 // no more than 5 layers of nesting 595 maxLen = (maxDepth*3+2)*limit + 1 // max length of _FUNCDATA_ArgInfo (see the compiler side for reasoning) 596 ) 597 598 p := (*[maxLen]uint8)(funcdata(f, _FUNCDATA_ArgInfo)) 599 if p == nil { 600 return 601 } 602 603 liveInfo := funcdata(f, _FUNCDATA_ArgLiveInfo) 604 liveIdx := pcdatavalue(f, _PCDATA_ArgLiveIndex, pc, nil) 605 startOffset := uint8(0xff) // smallest offset that needs liveness info (slots with a lower offset is always live) 606 if liveInfo != nil { 607 startOffset = *(*uint8)(liveInfo) 608 } 609 610 isLive := func(off, slotIdx uint8) bool { 611 if liveInfo == nil || liveIdx <= 0 { 612 return true // no liveness info, always live 613 } 614 if off < startOffset { 615 return true 616 } 617 bits := *(*uint8)(add(liveInfo, uintptr(liveIdx)+uintptr(slotIdx/8))) 618 return bits&(1<<(slotIdx%8)) != 0 619 } 620 621 print1 := func(off, sz, slotIdx uint8) { 622 x := readUnaligned64(add(argp, uintptr(off))) 623 // mask out irrelevant bits 624 if sz < 8 { 625 shift := 64 - sz*8 626 if goarch.BigEndian { 627 x = x >> shift 628 } else { 629 x = x << shift >> shift 630 } 631 } 632 print(hex(x)) 633 if !isLive(off, slotIdx) { 634 print("?") 635 } 636 } 637 638 start := true 639 printcomma := func() { 640 if !start { 641 print(", ") 642 } 643 } 644 pi := 0 645 slotIdx := uint8(0) // register arg spill slot index 646 printloop: 647 for { 648 o := p[pi] 649 pi++ 650 switch o { 651 case _endSeq: 652 break printloop 653 case _startAgg: 654 printcomma() 655 print("{") 656 start = true 657 continue 658 case _endAgg: 659 print("}") 660 case _dotdotdot: 661 printcomma() 662 print("...") 663 case _offsetTooLarge: 664 printcomma() 665 print("_") 666 default: 667 printcomma() 668 sz := p[pi] 669 pi++ 670 print1(o, sz, slotIdx) 671 if o >= startOffset { 672 slotIdx++ 673 } 674 } 675 start = false 676 } 677 } 678 679 // reflectMethodValue is a partial duplicate of reflect.makeFuncImpl 680 // and reflect.methodValue. 681 type reflectMethodValue struct { 682 fn uintptr 683 stack *bitvector // ptrmap for both args and results 684 argLen uintptr // just args 685 } 686 687 // getArgInfoFast returns the argument frame information for a call to f. 688 // It is short and inlineable. However, it does not handle all functions. 689 // If ok reports false, you must call getArgInfo instead. 690 // TODO(josharian): once we do mid-stack inlining, 691 // call getArgInfo directly from getArgInfoFast and stop returning an ok bool. 692 func getArgInfoFast(f funcInfo, needArgMap bool) (arglen uintptr, argmap *bitvector, ok bool) { 693 return uintptr(f.args), nil, !(needArgMap && f.args == _ArgsSizeUnknown) 694 } 695 696 // getArgInfo returns the argument frame information for a call to f 697 // with call frame frame. 698 // 699 // This is used for both actual calls with active stack frames and for 700 // deferred calls or goroutines that are not yet executing. If this is an actual 701 // call, ctxt must be nil (getArgInfo will retrieve what it needs from 702 // the active stack frame). If this is a deferred call or unstarted goroutine, 703 // ctxt must be the function object that was deferred or go'd. 704 func getArgInfo(frame *stkframe, f funcInfo, needArgMap bool, ctxt *funcval) (arglen uintptr, argmap *bitvector) { 705 arglen = uintptr(f.args) 706 if needArgMap && f.args == _ArgsSizeUnknown { 707 // Extract argument bitmaps for reflect stubs from the calls they made to reflect. 708 switch funcname(f) { 709 case "reflect.makeFuncStub", "reflect.methodValueCall": 710 // These take a *reflect.methodValue as their 711 // context register. 712 var mv *reflectMethodValue 713 var retValid bool 714 if ctxt != nil { 715 // This is not an actual call, but a 716 // deferred call or an unstarted goroutine. 717 // The function value is itself the *reflect.methodValue. 718 mv = (*reflectMethodValue)(unsafe.Pointer(ctxt)) 719 } else { 720 // This is a real call that took the 721 // *reflect.methodValue as its context 722 // register and immediately saved it 723 // to 0(SP). Get the methodValue from 724 // 0(SP). 725 arg0 := frame.sp + sys.MinFrameSize 726 mv = *(**reflectMethodValue)(unsafe.Pointer(arg0)) 727 // Figure out whether the return values are valid. 728 // Reflect will update this value after it copies 729 // in the return values. 730 retValid = *(*bool)(unsafe.Pointer(arg0 + 4*goarch.PtrSize)) 731 } 732 if mv.fn != f.entry() { 733 print("runtime: confused by ", funcname(f), "\n") 734 throw("reflect mismatch") 735 } 736 bv := mv.stack 737 arglen = uintptr(bv.n * goarch.PtrSize) 738 if !retValid { 739 arglen = uintptr(mv.argLen) &^ (goarch.PtrSize - 1) 740 } 741 argmap = bv 742 } 743 } 744 return 745 } 746 747 // tracebackCgoContext handles tracing back a cgo context value, from 748 // the context argument to setCgoTraceback, for the gentraceback 749 // function. It returns the new value of n. 750 func tracebackCgoContext(pcbuf *uintptr, printing bool, ctxt uintptr, n, max int) int { 751 var cgoPCs [32]uintptr 752 cgoContextPCs(ctxt, cgoPCs[:]) 753 var arg cgoSymbolizerArg 754 anySymbolized := false 755 for _, pc := range cgoPCs { 756 if pc == 0 || n >= max { 757 break 758 } 759 if pcbuf != nil { 760 (*[1 << 20]uintptr)(unsafe.Pointer(pcbuf))[n] = pc 761 } 762 if printing { 763 if cgoSymbolizer == nil { 764 print("non-Go function at pc=", hex(pc), "\n") 765 } else { 766 c := printOneCgoTraceback(pc, max-n, &arg) 767 n += c - 1 // +1 a few lines down 768 anySymbolized = true 769 } 770 } 771 n++ 772 } 773 if anySymbolized { 774 arg.pc = 0 775 callCgoSymbolizer(&arg) 776 } 777 return n 778 } 779 780 func printcreatedby(gp *g) { 781 // Show what created goroutine, except main goroutine (goid 1). 782 pc := gp.gopc 783 f := findfunc(pc) 784 if f.valid() && showframe(f, gp, false, funcID_normal, funcID_normal) && gp.goid != 1 { 785 printcreatedby1(f, pc) 786 } 787 } 788 789 func printcreatedby1(f funcInfo, pc uintptr) { 790 print("created by ", funcname(f), "\n") 791 tracepc := pc // back up to CALL instruction for funcline. 792 if pc > f.entry() { 793 tracepc -= sys.PCQuantum 794 } 795 file, line := funcline(f, tracepc) 796 print("\t", file, ":", line) 797 if pc > f.entry() { 798 print(" +", hex(pc-f.entry())) 799 } 800 print("\n") 801 } 802 803 func traceback(pc, sp, lr uintptr, gp *g) { 804 traceback1(pc, sp, lr, gp, 0) 805 } 806 807 // tracebacktrap is like traceback but expects that the PC and SP were obtained 808 // from a trap, not from gp->sched or gp->syscallpc/gp->syscallsp or getcallerpc/getcallersp. 809 // Because they are from a trap instead of from a saved pair, 810 // the initial PC must not be rewound to the previous instruction. 811 // (All the saved pairs record a PC that is a return address, so we 812 // rewind it into the CALL instruction.) 813 // If gp.m.libcall{g,pc,sp} information is available, it uses that information in preference to 814 // the pc/sp/lr passed in. 815 func tracebacktrap(pc, sp, lr uintptr, gp *g) { 816 if gp.m.libcallsp != 0 { 817 // We're in C code somewhere, traceback from the saved position. 818 traceback1(gp.m.libcallpc, gp.m.libcallsp, 0, gp.m.libcallg.ptr(), 0) 819 return 820 } 821 traceback1(pc, sp, lr, gp, _TraceTrap) 822 } 823 824 func traceback1(pc, sp, lr uintptr, gp *g, flags uint) { 825 // If the goroutine is in cgo, and we have a cgo traceback, print that. 826 if iscgo && gp.m != nil && gp.m.ncgo > 0 && gp.syscallsp != 0 && gp.m.cgoCallers != nil && gp.m.cgoCallers[0] != 0 { 827 // Lock cgoCallers so that a signal handler won't 828 // change it, copy the array, reset it, unlock it. 829 // We are locked to the thread and are not running 830 // concurrently with a signal handler. 831 // We just have to stop a signal handler from interrupting 832 // in the middle of our copy. 833 atomic.Store(&gp.m.cgoCallersUse, 1) 834 cgoCallers := *gp.m.cgoCallers 835 gp.m.cgoCallers[0] = 0 836 atomic.Store(&gp.m.cgoCallersUse, 0) 837 838 printCgoTraceback(&cgoCallers) 839 } 840 841 if readgstatus(gp)&^_Gscan == _Gsyscall { 842 // Override registers if blocked in system call. 843 pc = gp.syscallpc 844 sp = gp.syscallsp 845 flags &^= _TraceTrap 846 } 847 if gp.m != nil && gp.m.vdsoSP != 0 { 848 // Override registers if running in VDSO. This comes after the 849 // _Gsyscall check to cover VDSO calls after entersyscall. 850 pc = gp.m.vdsoPC 851 sp = gp.m.vdsoSP 852 flags &^= _TraceTrap 853 } 854 855 // Print traceback. By default, omits runtime frames. 856 // If that means we print nothing at all, repeat forcing all frames printed. 857 n := gentraceback(pc, sp, lr, gp, 0, nil, _TracebackMaxFrames, nil, nil, flags) 858 if n == 0 && (flags&_TraceRuntimeFrames) == 0 { 859 n = gentraceback(pc, sp, lr, gp, 0, nil, _TracebackMaxFrames, nil, nil, flags|_TraceRuntimeFrames) 860 } 861 if n == _TracebackMaxFrames { 862 print("...additional frames elided...\n") 863 } 864 printcreatedby(gp) 865 866 if gp.ancestors == nil { 867 return 868 } 869 for _, ancestor := range *gp.ancestors { 870 printAncestorTraceback(ancestor) 871 } 872 } 873 874 // printAncestorTraceback prints the traceback of the given ancestor. 875 // TODO: Unify this with gentraceback and CallersFrames. 876 func printAncestorTraceback(ancestor ancestorInfo) { 877 print("[originating from goroutine ", ancestor.goid, "]:\n") 878 for fidx, pc := range ancestor.pcs { 879 f := findfunc(pc) // f previously validated 880 if showfuncinfo(f, fidx == 0, funcID_normal, funcID_normal) { 881 printAncestorTracebackFuncInfo(f, pc) 882 } 883 } 884 if len(ancestor.pcs) == _TracebackMaxFrames { 885 print("...additional frames elided...\n") 886 } 887 // Show what created goroutine, except main goroutine (goid 1). 888 f := findfunc(ancestor.gopc) 889 if f.valid() && showfuncinfo(f, false, funcID_normal, funcID_normal) && ancestor.goid != 1 { 890 printcreatedby1(f, ancestor.gopc) 891 } 892 } 893 894 // printAncestorTraceback prints the given function info at a given pc 895 // within an ancestor traceback. The precision of this info is reduced 896 // due to only have access to the pcs at the time of the caller 897 // goroutine being created. 898 func printAncestorTracebackFuncInfo(f funcInfo, pc uintptr) { 899 name := funcname(f) 900 if inldata := funcdata(f, _FUNCDATA_InlTree); inldata != nil { 901 inltree := (*[1 << 20]inlinedCall)(inldata) 902 ix := pcdatavalue(f, _PCDATA_InlTreeIndex, pc, nil) 903 if ix >= 0 { 904 name = funcnameFromNameoff(f, inltree[ix].func_) 905 } 906 } 907 file, line := funcline(f, pc) 908 if name == "runtime.gopanic" { 909 name = "panic" 910 } 911 print(name, "(...)\n") 912 print("\t", file, ":", line) 913 if pc > f.entry() { 914 print(" +", hex(pc-f.entry())) 915 } 916 print("\n") 917 } 918 919 func callers(skip int, pcbuf []uintptr) int { 920 sp := getcallersp() 921 pc := getcallerpc() 922 gp := getg() 923 var n int 924 systemstack(func() { 925 n = gentraceback(pc, sp, 0, gp, skip, &pcbuf[0], len(pcbuf), nil, nil, 0) 926 }) 927 return n 928 } 929 930 func gcallers(gp *g, skip int, pcbuf []uintptr) int { 931 return gentraceback(^uintptr(0), ^uintptr(0), 0, gp, skip, &pcbuf[0], len(pcbuf), nil, nil, 0) 932 } 933 934 // showframe reports whether the frame with the given characteristics should 935 // be printed during a traceback. 936 func showframe(f funcInfo, gp *g, firstFrame bool, funcID, childID funcID) bool { 937 g := getg() 938 if g.m.throwing >= throwTypeRuntime && gp != nil && (gp == g.m.curg || gp == g.m.caughtsig.ptr()) { 939 return true 940 } 941 return showfuncinfo(f, firstFrame, funcID, childID) 942 } 943 944 // showfuncinfo reports whether a function with the given characteristics should 945 // be printed during a traceback. 946 func showfuncinfo(f funcInfo, firstFrame bool, funcID, childID funcID) bool { 947 // Note that f may be a synthesized funcInfo for an inlined 948 // function, in which case only nameoff and funcID are set. 949 950 level, _, _ := gotraceback() 951 if level > 1 { 952 // Show all frames. 953 return true 954 } 955 956 if !f.valid() { 957 return false 958 } 959 960 if funcID == funcID_wrapper && elideWrapperCalling(childID) { 961 return false 962 } 963 964 name := funcname(f) 965 966 // Special case: always show runtime.gopanic frame 967 // in the middle of a stack trace, so that we can 968 // see the boundary between ordinary code and 969 // panic-induced deferred code. 970 // See golang.org/issue/5832. 971 if name == "runtime.gopanic" && !firstFrame { 972 return true 973 } 974 975 return bytealg.IndexByteString(name, '.') >= 0 && (!hasPrefix(name, "runtime.") || isExportedRuntime(name)) 976 } 977 978 // isExportedRuntime reports whether name is an exported runtime function. 979 // It is only for runtime functions, so ASCII A-Z is fine. 980 func isExportedRuntime(name string) bool { 981 const n = len("runtime.") 982 return len(name) > n && name[:n] == "runtime." && 'A' <= name[n] && name[n] <= 'Z' 983 } 984 985 // elideWrapperCalling reports whether a wrapper function that called 986 // function id should be elided from stack traces. 987 func elideWrapperCalling(id funcID) bool { 988 // If the wrapper called a panic function instead of the 989 // wrapped function, we want to include it in stacks. 990 return !(id == funcID_gopanic || id == funcID_sigpanic || id == funcID_panicwrap) 991 } 992 993 var gStatusStrings = [...]string{ 994 _Gidle: "idle", 995 _Grunnable: "runnable", 996 _Grunning: "running", 997 _Gsyscall: "syscall", 998 _Gwaiting: "waiting", 999 _Gdead: "dead", 1000 _Gcopystack: "copystack", 1001 _Gpreempted: "preempted", 1002 } 1003 1004 func goroutineheader(gp *g) { 1005 gpstatus := readgstatus(gp) 1006 1007 isScan := gpstatus&_Gscan != 0 1008 gpstatus &^= _Gscan // drop the scan bit 1009 1010 // Basic string status 1011 var status string 1012 if 0 <= gpstatus && gpstatus < uint32(len(gStatusStrings)) { 1013 status = gStatusStrings[gpstatus] 1014 } else { 1015 status = "???" 1016 } 1017 1018 // Override. 1019 if gpstatus == _Gwaiting && gp.waitreason != waitReasonZero { 1020 status = gp.waitreason.String() 1021 } 1022 1023 // approx time the G is blocked, in minutes 1024 var waitfor int64 1025 if (gpstatus == _Gwaiting || gpstatus == _Gsyscall) && gp.waitsince != 0 { 1026 waitfor = (nanotime() - gp.waitsince) / 60e9 1027 } 1028 print("goroutine ", gp.goid, " [", status) 1029 if isScan { 1030 print(" (scan)") 1031 } 1032 if waitfor >= 1 { 1033 print(", ", waitfor, " minutes") 1034 } 1035 if gp.lockedm != 0 { 1036 print(", locked to thread") 1037 } 1038 print("]:\n") 1039 } 1040 1041 func tracebackothers(me *g) { 1042 level, _, _ := gotraceback() 1043 1044 // Show the current goroutine first, if we haven't already. 1045 curgp := getg().m.curg 1046 if curgp != nil && curgp != me { 1047 print("\n") 1048 goroutineheader(curgp) 1049 traceback(^uintptr(0), ^uintptr(0), 0, curgp) 1050 } 1051 1052 // We can't call locking forEachG here because this may be during fatal 1053 // throw/panic, where locking could be out-of-order or a direct 1054 // deadlock. 1055 // 1056 // Instead, use forEachGRace, which requires no locking. We don't lock 1057 // against concurrent creation of new Gs, but even with allglock we may 1058 // miss Gs created after this loop. 1059 forEachGRace(func(gp *g) { 1060 if gp == me || gp == curgp || readgstatus(gp) == _Gdead || isSystemGoroutine(gp, false) && level < 2 { 1061 return 1062 } 1063 print("\n") 1064 goroutineheader(gp) 1065 // Note: gp.m == g.m occurs when tracebackothers is 1066 // called from a signal handler initiated during a 1067 // systemstack call. The original G is still in the 1068 // running state, and we want to print its stack. 1069 if gp.m != getg().m && readgstatus(gp)&^_Gscan == _Grunning { 1070 print("\tgoroutine running on other thread; stack unavailable\n") 1071 printcreatedby(gp) 1072 } else { 1073 traceback(^uintptr(0), ^uintptr(0), 0, gp) 1074 } 1075 }) 1076 } 1077 1078 // tracebackHexdump hexdumps part of stk around frame.sp and frame.fp 1079 // for debugging purposes. If the address bad is included in the 1080 // hexdumped range, it will mark it as well. 1081 func tracebackHexdump(stk stack, frame *stkframe, bad uintptr) { 1082 const expand = 32 * goarch.PtrSize 1083 const maxExpand = 256 * goarch.PtrSize 1084 // Start around frame.sp. 1085 lo, hi := frame.sp, frame.sp 1086 // Expand to include frame.fp. 1087 if frame.fp != 0 && frame.fp < lo { 1088 lo = frame.fp 1089 } 1090 if frame.fp != 0 && frame.fp > hi { 1091 hi = frame.fp 1092 } 1093 // Expand a bit more. 1094 lo, hi = lo-expand, hi+expand 1095 // But don't go too far from frame.sp. 1096 if lo < frame.sp-maxExpand { 1097 lo = frame.sp - maxExpand 1098 } 1099 if hi > frame.sp+maxExpand { 1100 hi = frame.sp + maxExpand 1101 } 1102 // And don't go outside the stack bounds. 1103 if lo < stk.lo { 1104 lo = stk.lo 1105 } 1106 if hi > stk.hi { 1107 hi = stk.hi 1108 } 1109 1110 // Print the hex dump. 1111 print("stack: frame={sp:", hex(frame.sp), ", fp:", hex(frame.fp), "} stack=[", hex(stk.lo), ",", hex(stk.hi), ")\n") 1112 hexdumpWords(lo, hi, func(p uintptr) byte { 1113 switch p { 1114 case frame.fp: 1115 return '>' 1116 case frame.sp: 1117 return '<' 1118 case bad: 1119 return '!' 1120 } 1121 return 0 1122 }) 1123 } 1124 1125 // isSystemGoroutine reports whether the goroutine g must be omitted 1126 // in stack dumps and deadlock detector. This is any goroutine that 1127 // starts at a runtime.* entry point, except for runtime.main, 1128 // runtime.handleAsyncEvent (wasm only) and sometimes runtime.runfinq. 1129 // 1130 // If fixed is true, any goroutine that can vary between user and 1131 // system (that is, the finalizer goroutine) is considered a user 1132 // goroutine. 1133 func isSystemGoroutine(gp *g, fixed bool) bool { 1134 // Keep this in sync with internal/trace.IsSystemGoroutine. 1135 f := findfunc(gp.startpc) 1136 if !f.valid() { 1137 return false 1138 } 1139 if f.funcID == funcID_runtime_main || f.funcID == funcID_handleAsyncEvent { 1140 return false 1141 } 1142 if f.funcID == funcID_runfinq { 1143 // We include the finalizer goroutine if it's calling 1144 // back into user code. 1145 if fixed { 1146 // This goroutine can vary. In fixed mode, 1147 // always consider it a user goroutine. 1148 return false 1149 } 1150 return !fingRunning 1151 } 1152 return hasPrefix(funcname(f), "runtime.") 1153 } 1154 1155 // SetCgoTraceback records three C functions to use to gather 1156 // traceback information from C code and to convert that traceback 1157 // information into symbolic information. These are used when printing 1158 // stack traces for a program that uses cgo. 1159 // 1160 // The traceback and context functions may be called from a signal 1161 // handler, and must therefore use only async-signal safe functions. 1162 // The symbolizer function may be called while the program is 1163 // crashing, and so must be cautious about using memory. None of the 1164 // functions may call back into Go. 1165 // 1166 // The context function will be called with a single argument, a 1167 // pointer to a struct: 1168 // 1169 // struct { 1170 // Context uintptr 1171 // } 1172 // 1173 // In C syntax, this struct will be 1174 // 1175 // struct { 1176 // uintptr_t Context; 1177 // }; 1178 // 1179 // If the Context field is 0, the context function is being called to 1180 // record the current traceback context. It should record in the 1181 // Context field whatever information is needed about the current 1182 // point of execution to later produce a stack trace, probably the 1183 // stack pointer and PC. In this case the context function will be 1184 // called from C code. 1185 // 1186 // If the Context field is not 0, then it is a value returned by a 1187 // previous call to the context function. This case is called when the 1188 // context is no longer needed; that is, when the Go code is returning 1189 // to its C code caller. This permits the context function to release 1190 // any associated resources. 1191 // 1192 // While it would be correct for the context function to record a 1193 // complete a stack trace whenever it is called, and simply copy that 1194 // out in the traceback function, in a typical program the context 1195 // function will be called many times without ever recording a 1196 // traceback for that context. Recording a complete stack trace in a 1197 // call to the context function is likely to be inefficient. 1198 // 1199 // The traceback function will be called with a single argument, a 1200 // pointer to a struct: 1201 // 1202 // struct { 1203 // Context uintptr 1204 // SigContext uintptr 1205 // Buf *uintptr 1206 // Max uintptr 1207 // } 1208 // 1209 // In C syntax, this struct will be 1210 // 1211 // struct { 1212 // uintptr_t Context; 1213 // uintptr_t SigContext; 1214 // uintptr_t* Buf; 1215 // uintptr_t Max; 1216 // }; 1217 // 1218 // The Context field will be zero to gather a traceback from the 1219 // current program execution point. In this case, the traceback 1220 // function will be called from C code. 1221 // 1222 // Otherwise Context will be a value previously returned by a call to 1223 // the context function. The traceback function should gather a stack 1224 // trace from that saved point in the program execution. The traceback 1225 // function may be called from an execution thread other than the one 1226 // that recorded the context, but only when the context is known to be 1227 // valid and unchanging. The traceback function may also be called 1228 // deeper in the call stack on the same thread that recorded the 1229 // context. The traceback function may be called multiple times with 1230 // the same Context value; it will usually be appropriate to cache the 1231 // result, if possible, the first time this is called for a specific 1232 // context value. 1233 // 1234 // If the traceback function is called from a signal handler on a Unix 1235 // system, SigContext will be the signal context argument passed to 1236 // the signal handler (a C ucontext_t* cast to uintptr_t). This may be 1237 // used to start tracing at the point where the signal occurred. If 1238 // the traceback function is not called from a signal handler, 1239 // SigContext will be zero. 1240 // 1241 // Buf is where the traceback information should be stored. It should 1242 // be PC values, such that Buf[0] is the PC of the caller, Buf[1] is 1243 // the PC of that function's caller, and so on. Max is the maximum 1244 // number of entries to store. The function should store a zero to 1245 // indicate the top of the stack, or that the caller is on a different 1246 // stack, presumably a Go stack. 1247 // 1248 // Unlike runtime.Callers, the PC values returned should, when passed 1249 // to the symbolizer function, return the file/line of the call 1250 // instruction. No additional subtraction is required or appropriate. 1251 // 1252 // On all platforms, the traceback function is invoked when a call from 1253 // Go to C to Go requests a stack trace. On linux/amd64, linux/ppc64le, 1254 // linux/arm64, and freebsd/amd64, the traceback function is also invoked 1255 // when a signal is received by a thread that is executing a cgo call. 1256 // The traceback function should not make assumptions about when it is 1257 // called, as future versions of Go may make additional calls. 1258 // 1259 // The symbolizer function will be called with a single argument, a 1260 // pointer to a struct: 1261 // 1262 // struct { 1263 // PC uintptr // program counter to fetch information for 1264 // File *byte // file name (NUL terminated) 1265 // Lineno uintptr // line number 1266 // Func *byte // function name (NUL terminated) 1267 // Entry uintptr // function entry point 1268 // More uintptr // set non-zero if more info for this PC 1269 // Data uintptr // unused by runtime, available for function 1270 // } 1271 // 1272 // In C syntax, this struct will be 1273 // 1274 // struct { 1275 // uintptr_t PC; 1276 // char* File; 1277 // uintptr_t Lineno; 1278 // char* Func; 1279 // uintptr_t Entry; 1280 // uintptr_t More; 1281 // uintptr_t Data; 1282 // }; 1283 // 1284 // The PC field will be a value returned by a call to the traceback 1285 // function. 1286 // 1287 // The first time the function is called for a particular traceback, 1288 // all the fields except PC will be 0. The function should fill in the 1289 // other fields if possible, setting them to 0/nil if the information 1290 // is not available. The Data field may be used to store any useful 1291 // information across calls. The More field should be set to non-zero 1292 // if there is more information for this PC, zero otherwise. If More 1293 // is set non-zero, the function will be called again with the same 1294 // PC, and may return different information (this is intended for use 1295 // with inlined functions). If More is zero, the function will be 1296 // called with the next PC value in the traceback. When the traceback 1297 // is complete, the function will be called once more with PC set to 1298 // zero; this may be used to free any information. Each call will 1299 // leave the fields of the struct set to the same values they had upon 1300 // return, except for the PC field when the More field is zero. The 1301 // function must not keep a copy of the struct pointer between calls. 1302 // 1303 // When calling SetCgoTraceback, the version argument is the version 1304 // number of the structs that the functions expect to receive. 1305 // Currently this must be zero. 1306 // 1307 // The symbolizer function may be nil, in which case the results of 1308 // the traceback function will be displayed as numbers. If the 1309 // traceback function is nil, the symbolizer function will never be 1310 // called. The context function may be nil, in which case the 1311 // traceback function will only be called with the context field set 1312 // to zero. If the context function is nil, then calls from Go to C 1313 // to Go will not show a traceback for the C portion of the call stack. 1314 // 1315 // SetCgoTraceback should be called only once, ideally from an init function. 1316 func SetCgoTraceback(version int, traceback, context, symbolizer unsafe.Pointer) { 1317 if version != 0 { 1318 panic("unsupported version") 1319 } 1320 1321 if cgoTraceback != nil && cgoTraceback != traceback || 1322 cgoContext != nil && cgoContext != context || 1323 cgoSymbolizer != nil && cgoSymbolizer != symbolizer { 1324 panic("call SetCgoTraceback only once") 1325 } 1326 1327 cgoTraceback = traceback 1328 cgoContext = context 1329 cgoSymbolizer = symbolizer 1330 1331 // The context function is called when a C function calls a Go 1332 // function. As such it is only called by C code in runtime/cgo. 1333 if _cgo_set_context_function != nil { 1334 cgocall(_cgo_set_context_function, context) 1335 } 1336 } 1337 1338 var cgoTraceback unsafe.Pointer 1339 var cgoContext unsafe.Pointer 1340 var cgoSymbolizer unsafe.Pointer 1341 1342 // cgoTracebackArg is the type passed to cgoTraceback. 1343 type cgoTracebackArg struct { 1344 context uintptr 1345 sigContext uintptr 1346 buf *uintptr 1347 max uintptr 1348 } 1349 1350 // cgoContextArg is the type passed to the context function. 1351 type cgoContextArg struct { 1352 context uintptr 1353 } 1354 1355 // cgoSymbolizerArg is the type passed to cgoSymbolizer. 1356 type cgoSymbolizerArg struct { 1357 pc uintptr 1358 file *byte 1359 lineno uintptr 1360 funcName *byte 1361 entry uintptr 1362 more uintptr 1363 data uintptr 1364 } 1365 1366 // cgoTraceback prints a traceback of callers. 1367 func printCgoTraceback(callers *cgoCallers) { 1368 if cgoSymbolizer == nil { 1369 for _, c := range callers { 1370 if c == 0 { 1371 break 1372 } 1373 print("non-Go function at pc=", hex(c), "\n") 1374 } 1375 return 1376 } 1377 1378 var arg cgoSymbolizerArg 1379 for _, c := range callers { 1380 if c == 0 { 1381 break 1382 } 1383 printOneCgoTraceback(c, 0x7fffffff, &arg) 1384 } 1385 arg.pc = 0 1386 callCgoSymbolizer(&arg) 1387 } 1388 1389 // printOneCgoTraceback prints the traceback of a single cgo caller. 1390 // This can print more than one line because of inlining. 1391 // Returns the number of frames printed. 1392 func printOneCgoTraceback(pc uintptr, max int, arg *cgoSymbolizerArg) int { 1393 c := 0 1394 arg.pc = pc 1395 for c <= max { 1396 callCgoSymbolizer(arg) 1397 if arg.funcName != nil { 1398 // Note that we don't print any argument 1399 // information here, not even parentheses. 1400 // The symbolizer must add that if appropriate. 1401 println(gostringnocopy(arg.funcName)) 1402 } else { 1403 println("non-Go function") 1404 } 1405 print("\t") 1406 if arg.file != nil { 1407 print(gostringnocopy(arg.file), ":", arg.lineno, " ") 1408 } 1409 print("pc=", hex(pc), "\n") 1410 c++ 1411 if arg.more == 0 { 1412 break 1413 } 1414 } 1415 return c 1416 } 1417 1418 // callCgoSymbolizer calls the cgoSymbolizer function. 1419 func callCgoSymbolizer(arg *cgoSymbolizerArg) { 1420 call := cgocall 1421 if panicking > 0 || getg().m.curg != getg() { 1422 // We do not want to call into the scheduler when panicking 1423 // or when on the system stack. 1424 call = asmcgocall 1425 } 1426 if msanenabled { 1427 msanwrite(unsafe.Pointer(arg), unsafe.Sizeof(cgoSymbolizerArg{})) 1428 } 1429 if asanenabled { 1430 asanwrite(unsafe.Pointer(arg), unsafe.Sizeof(cgoSymbolizerArg{})) 1431 } 1432 call(cgoSymbolizer, noescape(unsafe.Pointer(arg))) 1433 } 1434 1435 // cgoContextPCs gets the PC values from a cgo traceback. 1436 func cgoContextPCs(ctxt uintptr, buf []uintptr) { 1437 if cgoTraceback == nil { 1438 return 1439 } 1440 call := cgocall 1441 if panicking > 0 || getg().m.curg != getg() { 1442 // We do not want to call into the scheduler when panicking 1443 // or when on the system stack. 1444 call = asmcgocall 1445 } 1446 arg := cgoTracebackArg{ 1447 context: ctxt, 1448 buf: (*uintptr)(noescape(unsafe.Pointer(&buf[0]))), 1449 max: uintptr(len(buf)), 1450 } 1451 if msanenabled { 1452 msanwrite(unsafe.Pointer(&arg), unsafe.Sizeof(arg)) 1453 } 1454 if asanenabled { 1455 asanwrite(unsafe.Pointer(&arg), unsafe.Sizeof(arg)) 1456 } 1457 call(cgoTraceback, noescape(unsafe.Pointer(&arg))) 1458 } 1459