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