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Diffstat (limited to 'src/runtime/traceback.go')
| -rw-r--r-- | src/runtime/traceback.go | 1346 |
1 files changed, 1346 insertions, 0 deletions
diff --git a/src/runtime/traceback.go b/src/runtime/traceback.go new file mode 100644 index 0000000..2601cd6 --- /dev/null +++ b/src/runtime/traceback.go @@ -0,0 +1,1346 @@ +// Copyright 2009 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package runtime + +import ( + "internal/bytealg" + "runtime/internal/atomic" + "runtime/internal/sys" + "unsafe" +) + +// The code in this file implements stack trace walking for all architectures. +// The most important fact about a given architecture is whether it uses a link register. +// On systems with link registers, the prologue for a non-leaf function stores the +// incoming value of LR at the bottom of the newly allocated stack frame. +// On systems without link registers, the architecture pushes a return PC during +// the call instruction, so the return PC ends up above the stack frame. +// In this file, the return PC is always called LR, no matter how it was found. +// +// To date, the opposite of a link register architecture is an x86 architecture. +// This code may need to change if some other kind of non-link-register +// architecture comes along. +// +// The other important fact is the size of a pointer: on 32-bit systems the LR +// takes up only 4 bytes on the stack, while on 64-bit systems it takes up 8 bytes. +// Typically this is ptrSize. +// +// As an exception, amd64p32 had ptrSize == 4 but the CALL instruction still +// stored an 8-byte return PC onto the stack. To accommodate this, we used regSize +// as the size of the architecture-pushed return PC. +// +// usesLR is defined below in terms of minFrameSize, which is defined in +// arch_$GOARCH.go. ptrSize and regSize are defined in stubs.go. + +const usesLR = sys.MinFrameSize > 0 + +// Traceback over the deferred function calls. +// Report them like calls that have been invoked but not started executing yet. +func tracebackdefers(gp *g, callback func(*stkframe, unsafe.Pointer) bool, v unsafe.Pointer) { + var frame stkframe + for d := gp._defer; d != nil; d = d.link { + fn := d.fn + if fn == nil { + // Defer of nil function. Args don't matter. + frame.pc = 0 + frame.fn = funcInfo{} + frame.argp = 0 + frame.arglen = 0 + frame.argmap = nil + } else { + frame.pc = fn.fn + f := findfunc(frame.pc) + if !f.valid() { + print("runtime: unknown pc in defer ", hex(frame.pc), "\n") + throw("unknown pc") + } + frame.fn = f + frame.argp = uintptr(deferArgs(d)) + var ok bool + frame.arglen, frame.argmap, ok = getArgInfoFast(f, true) + if !ok { + frame.arglen, frame.argmap = getArgInfo(&frame, f, true, fn) + } + } + frame.continpc = frame.pc + if !callback((*stkframe)(noescape(unsafe.Pointer(&frame))), v) { + return + } + } +} + +const sizeofSkipFunction = 256 + +// Generic traceback. Handles runtime stack prints (pcbuf == nil), +// the runtime.Callers function (pcbuf != nil), as well as the garbage +// collector (callback != nil). A little clunky to merge these, but avoids +// duplicating the code and all its subtlety. +// +// The skip argument is only valid with pcbuf != nil and counts the number +// of logical frames to skip rather than physical frames (with inlining, a +// PC in pcbuf can represent multiple calls). If a PC is partially skipped +// and max > 1, pcbuf[1] will be runtime.skipPleaseUseCallersFrames+N where +// N indicates the number of logical frames to skip in pcbuf[0]. +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 { + if skip > 0 && callback != nil { + throw("gentraceback callback cannot be used with non-zero skip") + } + + // Don't call this "g"; it's too easy get "g" and "gp" confused. + if ourg := getg(); ourg == gp && ourg == ourg.m.curg { + // The starting sp has been passed in as a uintptr, and the caller may + // have other uintptr-typed stack references as well. + // If during one of the calls that got us here or during one of the + // callbacks below the stack must be grown, all these uintptr references + // to the stack will not be updated, and gentraceback will continue + // to inspect the old stack memory, which may no longer be valid. + // Even if all the variables were updated correctly, it is not clear that + // we want to expose a traceback that begins on one stack and ends + // on another stack. That could confuse callers quite a bit. + // Instead, we require that gentraceback and any other function that + // accepts an sp for the current goroutine (typically obtained by + // calling getcallersp) must not run on that goroutine's stack but + // instead on the g0 stack. + throw("gentraceback cannot trace user goroutine on its own stack") + } + level, _, _ := gotraceback() + + var ctxt *funcval // Context pointer for unstarted goroutines. See issue #25897. + + if pc0 == ^uintptr(0) && sp0 == ^uintptr(0) { // Signal to fetch saved values from gp. + if gp.syscallsp != 0 { + pc0 = gp.syscallpc + sp0 = gp.syscallsp + if usesLR { + lr0 = 0 + } + } else { + pc0 = gp.sched.pc + sp0 = gp.sched.sp + if usesLR { + lr0 = gp.sched.lr + } + ctxt = (*funcval)(gp.sched.ctxt) + } + } + + nprint := 0 + var frame stkframe + frame.pc = pc0 + frame.sp = sp0 + if usesLR { + frame.lr = lr0 + } + waspanic := false + cgoCtxt := gp.cgoCtxt + printing := pcbuf == nil && callback == nil + + // If the PC is zero, it's likely a nil function call. + // Start in the caller's frame. + if frame.pc == 0 { + if usesLR { + frame.pc = *(*uintptr)(unsafe.Pointer(frame.sp)) + frame.lr = 0 + } else { + frame.pc = uintptr(*(*sys.Uintreg)(unsafe.Pointer(frame.sp))) + frame.sp += sys.RegSize + } + } + + f := findfunc(frame.pc) + if !f.valid() { + if callback != nil || printing { + print("runtime: unknown pc ", hex(frame.pc), "\n") + tracebackHexdump(gp.stack, &frame, 0) + } + if callback != nil { + throw("unknown pc") + } + return 0 + } + frame.fn = f + + var cache pcvalueCache + + lastFuncID := funcID_normal + n := 0 + for n < max { + // Typically: + // pc is the PC of the running function. + // sp is the stack pointer at that program counter. + // fp is the frame pointer (caller's stack pointer) at that program counter, or nil if unknown. + // stk is the stack containing sp. + // The caller's program counter is lr, unless lr is zero, in which case it is *(uintptr*)sp. + f = frame.fn + if f.pcsp == 0 { + // No frame information, must be external function, like race support. + // See golang.org/issue/13568. + break + } + + // Found an actual function. + // Derive frame pointer and link register. + if frame.fp == 0 { + // Jump over system stack transitions. If we're on g0 and there's a user + // goroutine, try to jump. Otherwise this is a regular call. + if flags&_TraceJumpStack != 0 && gp == gp.m.g0 && gp.m.curg != nil { + switch f.funcID { + case funcID_morestack: + // morestack does not return normally -- newstack() + // gogo's to curg.sched. Match that. + // This keeps morestack() from showing up in the backtrace, + // but that makes some sense since it'll never be returned + // to. + frame.pc = gp.m.curg.sched.pc + frame.fn = findfunc(frame.pc) + f = frame.fn + frame.sp = gp.m.curg.sched.sp + cgoCtxt = gp.m.curg.cgoCtxt + case funcID_systemstack: + // systemstack returns normally, so just follow the + // stack transition. + frame.sp = gp.m.curg.sched.sp + cgoCtxt = gp.m.curg.cgoCtxt + } + } + frame.fp = frame.sp + uintptr(funcspdelta(f, frame.pc, &cache)) + if !usesLR { + // On x86, call instruction pushes return PC before entering new function. + frame.fp += sys.RegSize + } + } + var flr funcInfo + if topofstack(f, gp.m != nil && gp == gp.m.g0) { + frame.lr = 0 + flr = funcInfo{} + } else if usesLR && f.funcID == funcID_jmpdefer { + // jmpdefer modifies SP/LR/PC non-atomically. + // If a profiling interrupt arrives during jmpdefer, + // the stack unwind may see a mismatched register set + // and get confused. Stop if we see PC within jmpdefer + // to avoid that confusion. + // See golang.org/issue/8153. + if callback != nil { + throw("traceback_arm: found jmpdefer when tracing with callback") + } + frame.lr = 0 + } else { + var lrPtr uintptr + if usesLR { + if n == 0 && frame.sp < frame.fp || frame.lr == 0 { + lrPtr = frame.sp + frame.lr = *(*uintptr)(unsafe.Pointer(lrPtr)) + } + } else { + if frame.lr == 0 { + lrPtr = frame.fp - sys.RegSize + frame.lr = uintptr(*(*sys.Uintreg)(unsafe.Pointer(lrPtr))) + } + } + flr = findfunc(frame.lr) + if !flr.valid() { + // This happens if you get a profiling interrupt at just the wrong time. + // In that context it is okay to stop early. + // But if callback is set, we're doing a garbage collection and must + // get everything, so crash loudly. + doPrint := printing + if doPrint && gp.m.incgo && f.funcID == funcID_sigpanic { + // We can inject sigpanic + // calls directly into C code, + // in which case we'll see a C + // return PC. Don't complain. + doPrint = false + } + if callback != nil || doPrint { + print("runtime: unexpected return pc for ", funcname(f), " called from ", hex(frame.lr), "\n") + tracebackHexdump(gp.stack, &frame, lrPtr) + } + if callback != nil { + throw("unknown caller pc") + } + } + } + + frame.varp = frame.fp + if !usesLR { + // On x86, call instruction pushes return PC before entering new function. + frame.varp -= sys.RegSize + } + + // For architectures with frame pointers, if there's + // a frame, then there's a saved frame pointer here. + if frame.varp > frame.sp && (GOARCH == "amd64" || GOARCH == "arm64") { + frame.varp -= sys.RegSize + } + + // Derive size of arguments. + // Most functions have a fixed-size argument block, + // so we can use metadata about the function f. + // Not all, though: there are some variadic functions + // in package runtime and reflect, and for those we use call-specific + // metadata recorded by f's caller. + if callback != nil || printing { + frame.argp = frame.fp + sys.MinFrameSize + var ok bool + frame.arglen, frame.argmap, ok = getArgInfoFast(f, callback != nil) + if !ok { + frame.arglen, frame.argmap = getArgInfo(&frame, f, callback != nil, ctxt) + } + } + ctxt = nil // ctxt is only needed to get arg maps for the topmost frame + + // Determine frame's 'continuation PC', where it can continue. + // Normally this is the return address on the stack, but if sigpanic + // is immediately below this function on the stack, then the frame + // stopped executing due to a trap, and frame.pc is probably not + // a safe point for looking up liveness information. In this panicking case, + // the function either doesn't return at all (if it has no defers or if the + // defers do not recover) or it returns from one of the calls to + // deferproc a second time (if the corresponding deferred func recovers). + // In the latter case, use a deferreturn call site as the continuation pc. + frame.continpc = frame.pc + if waspanic { + if frame.fn.deferreturn != 0 { + frame.continpc = frame.fn.entry + uintptr(frame.fn.deferreturn) + 1 + // Note: this may perhaps keep return variables alive longer than + // strictly necessary, as we are using "function has a defer statement" + // as a proxy for "function actually deferred something". It seems + // to be a minor drawback. (We used to actually look through the + // gp._defer for a defer corresponding to this function, but that + // is hard to do with defer records on the stack during a stack copy.) + // Note: the +1 is to offset the -1 that + // stack.go:getStackMap does to back up a return + // address make sure the pc is in the CALL instruction. + } else { + frame.continpc = 0 + } + } + + if callback != nil { + if !callback((*stkframe)(noescape(unsafe.Pointer(&frame))), v) { + return n + } + } + + if pcbuf != nil { + pc := frame.pc + // backup to CALL instruction to read inlining info (same logic as below) + tracepc := pc + // Normally, pc is a return address. In that case, we want to look up + // file/line information using pc-1, because that is the pc of the + // call instruction (more precisely, the last byte of the call instruction). + // Callers expect the pc buffer to contain return addresses and do the + // same -1 themselves, so we keep pc unchanged. + // When the pc is from a signal (e.g. profiler or segv) then we want + // to look up file/line information using pc, and we store pc+1 in the + // pc buffer so callers can unconditionally subtract 1 before looking up. + // See issue 34123. + // The pc can be at function entry when the frame is initialized without + // actually running code, like runtime.mstart. + if (n == 0 && flags&_TraceTrap != 0) || waspanic || pc == f.entry { + pc++ + } else { + tracepc-- + } + + // If there is inlining info, record the inner frames. + if inldata := funcdata(f, _FUNCDATA_InlTree); inldata != nil { + inltree := (*[1 << 20]inlinedCall)(inldata) + for { + ix := pcdatavalue(f, _PCDATA_InlTreeIndex, tracepc, &cache) + if ix < 0 { + break + } + if inltree[ix].funcID == funcID_wrapper && elideWrapperCalling(lastFuncID) { + // ignore wrappers + } else if skip > 0 { + skip-- + } else if n < max { + (*[1 << 20]uintptr)(unsafe.Pointer(pcbuf))[n] = pc + n++ + } + lastFuncID = inltree[ix].funcID + // Back up to an instruction in the "caller". + tracepc = frame.fn.entry + uintptr(inltree[ix].parentPc) + pc = tracepc + 1 + } + } + // Record the main frame. + if f.funcID == funcID_wrapper && elideWrapperCalling(lastFuncID) { + // Ignore wrapper functions (except when they trigger panics). + } else if skip > 0 { + skip-- + } else if n < max { + (*[1 << 20]uintptr)(unsafe.Pointer(pcbuf))[n] = pc + n++ + } + lastFuncID = f.funcID + n-- // offset n++ below + } + + if printing { + // assume skip=0 for printing. + // + // Never elide wrappers if we haven't printed + // any frames. And don't elide wrappers that + // called panic rather than the wrapped + // function. Otherwise, leave them out. + + // backup to CALL instruction to read inlining info (same logic as below) + tracepc := frame.pc + if (n > 0 || flags&_TraceTrap == 0) && frame.pc > f.entry && !waspanic { + tracepc-- + } + // If there is inlining info, print the inner frames. + if inldata := funcdata(f, _FUNCDATA_InlTree); inldata != nil { + inltree := (*[1 << 20]inlinedCall)(inldata) + var inlFunc _func + inlFuncInfo := funcInfo{&inlFunc, f.datap} + for { + ix := pcdatavalue(f, _PCDATA_InlTreeIndex, tracepc, nil) + if ix < 0 { + break + } + + // Create a fake _func for the + // inlined function. + inlFunc.nameoff = inltree[ix].func_ + inlFunc.funcID = inltree[ix].funcID + + if (flags&_TraceRuntimeFrames) != 0 || showframe(inlFuncInfo, gp, nprint == 0, inlFuncInfo.funcID, lastFuncID) { + name := funcname(inlFuncInfo) + file, line := funcline(f, tracepc) + print(name, "(...)\n") + print("\t", file, ":", line, "\n") + nprint++ + } + lastFuncID = inltree[ix].funcID + // Back up to an instruction in the "caller". + tracepc = frame.fn.entry + uintptr(inltree[ix].parentPc) + } + } + if (flags&_TraceRuntimeFrames) != 0 || showframe(f, gp, nprint == 0, f.funcID, lastFuncID) { + // Print during crash. + // main(0x1, 0x2, 0x3) + // /home/rsc/go/src/runtime/x.go:23 +0xf + // + name := funcname(f) + file, line := funcline(f, tracepc) + if name == "runtime.gopanic" { + name = "panic" + } + print(name, "(") + argp := (*[100]uintptr)(unsafe.Pointer(frame.argp)) + for i := uintptr(0); i < frame.arglen/sys.PtrSize; i++ { + if i >= 10 { + print(", ...") + break + } + if i != 0 { + print(", ") + } + print(hex(argp[i])) + } + print(")\n") + print("\t", file, ":", line) + if frame.pc > f.entry { + print(" +", hex(frame.pc-f.entry)) + } + if gp.m != nil && gp.m.throwing > 0 && gp == gp.m.curg || level >= 2 { + print(" fp=", hex(frame.fp), " sp=", hex(frame.sp), " pc=", hex(frame.pc)) + } + print("\n") + nprint++ + } + lastFuncID = f.funcID + } + n++ + + if f.funcID == funcID_cgocallback && len(cgoCtxt) > 0 { + ctxt := cgoCtxt[len(cgoCtxt)-1] + cgoCtxt = cgoCtxt[:len(cgoCtxt)-1] + + // skip only applies to Go frames. + // callback != nil only used when we only care + // about Go frames. + if skip == 0 && callback == nil { + n = tracebackCgoContext(pcbuf, printing, ctxt, n, max) + } + } + + waspanic = f.funcID == funcID_sigpanic + injectedCall := waspanic || f.funcID == funcID_asyncPreempt + + // Do not unwind past the bottom of the stack. + if !flr.valid() { + break + } + + // Unwind to next frame. + frame.fn = flr + frame.pc = frame.lr + frame.lr = 0 + frame.sp = frame.fp + frame.fp = 0 + frame.argmap = nil + + // On link register architectures, sighandler saves the LR on stack + // before faking a call. + if usesLR && injectedCall { + x := *(*uintptr)(unsafe.Pointer(frame.sp)) + frame.sp += sys.MinFrameSize + if GOARCH == "arm64" { + // arm64 needs 16-byte aligned SP, always + frame.sp += sys.PtrSize + } + f = findfunc(frame.pc) + frame.fn = f + if !f.valid() { + frame.pc = x + } else if funcspdelta(f, frame.pc, &cache) == 0 { + frame.lr = x + } + } + } + + if printing { + n = nprint + } + + // Note that panic != nil is okay here: there can be leftover panics, + // because the defers on the panic stack do not nest in frame order as + // they do on the defer stack. If you have: + // + // frame 1 defers d1 + // frame 2 defers d2 + // frame 3 defers d3 + // frame 4 panics + // frame 4's panic starts running defers + // frame 5, running d3, defers d4 + // frame 5 panics + // frame 5's panic starts running defers + // frame 6, running d4, garbage collects + // frame 6, running d2, garbage collects + // + // During the execution of d4, the panic stack is d4 -> d3, which + // is nested properly, and we'll treat frame 3 as resumable, because we + // can find d3. (And in fact frame 3 is resumable. If d4 recovers + // and frame 5 continues running, d3, d3 can recover and we'll + // resume execution in (returning from) frame 3.) + // + // During the execution of d2, however, the panic stack is d2 -> d3, + // which is inverted. The scan will match d2 to frame 2 but having + // d2 on the stack until then means it will not match d3 to frame 3. + // This is okay: if we're running d2, then all the defers after d2 have + // completed and their corresponding frames are dead. Not finding d3 + // for frame 3 means we'll set frame 3's continpc == 0, which is correct + // (frame 3 is dead). At the end of the walk the panic stack can thus + // contain defers (d3 in this case) for dead frames. The inversion here + // always indicates a dead frame, and the effect of the inversion on the + // scan is to hide those dead frames, so the scan is still okay: + // what's left on the panic stack are exactly (and only) the dead frames. + // + // We require callback != nil here because only when callback != nil + // do we know that gentraceback is being called in a "must be correct" + // context as opposed to a "best effort" context. The tracebacks with + // callbacks only happen when everything is stopped nicely. + // At other times, such as when gathering a stack for a profiling signal + // or when printing a traceback during a crash, everything may not be + // stopped nicely, and the stack walk may not be able to complete. + if callback != nil && n < max && frame.sp != gp.stktopsp { + print("runtime: g", gp.goid, ": frame.sp=", hex(frame.sp), " top=", hex(gp.stktopsp), "\n") + print("\tstack=[", hex(gp.stack.lo), "-", hex(gp.stack.hi), "] n=", n, " max=", max, "\n") + throw("traceback did not unwind completely") + } + + return n +} + +// reflectMethodValue is a partial duplicate of reflect.makeFuncImpl +// and reflect.methodValue. +type reflectMethodValue struct { + fn uintptr + stack *bitvector // ptrmap for both args and results + argLen uintptr // just args +} + +// getArgInfoFast returns the argument frame information for a call to f. +// It is short and inlineable. However, it does not handle all functions. +// If ok reports false, you must call getArgInfo instead. +// TODO(josharian): once we do mid-stack inlining, +// call getArgInfo directly from getArgInfoFast and stop returning an ok bool. +func getArgInfoFast(f funcInfo, needArgMap bool) (arglen uintptr, argmap *bitvector, ok bool) { + return uintptr(f.args), nil, !(needArgMap && f.args == _ArgsSizeUnknown) +} + +// getArgInfo returns the argument frame information for a call to f +// with call frame frame. +// +// This is used for both actual calls with active stack frames and for +// deferred calls or goroutines that are not yet executing. If this is an actual +// call, ctxt must be nil (getArgInfo will retrieve what it needs from +// the active stack frame). If this is a deferred call or unstarted goroutine, +// ctxt must be the function object that was deferred or go'd. +func getArgInfo(frame *stkframe, f funcInfo, needArgMap bool, ctxt *funcval) (arglen uintptr, argmap *bitvector) { + arglen = uintptr(f.args) + if needArgMap && f.args == _ArgsSizeUnknown { + // Extract argument bitmaps for reflect stubs from the calls they made to reflect. + switch funcname(f) { + case "reflect.makeFuncStub", "reflect.methodValueCall": + // These take a *reflect.methodValue as their + // context register. + var mv *reflectMethodValue + var retValid bool + if ctxt != nil { + // This is not an actual call, but a + // deferred call or an unstarted goroutine. + // The function value is itself the *reflect.methodValue. + mv = (*reflectMethodValue)(unsafe.Pointer(ctxt)) + } else { + // This is a real call that took the + // *reflect.methodValue as its context + // register and immediately saved it + // to 0(SP). Get the methodValue from + // 0(SP). + arg0 := frame.sp + sys.MinFrameSize + mv = *(**reflectMethodValue)(unsafe.Pointer(arg0)) + // Figure out whether the return values are valid. + // Reflect will update this value after it copies + // in the return values. + retValid = *(*bool)(unsafe.Pointer(arg0 + 3*sys.PtrSize)) + } + if mv.fn != f.entry { + print("runtime: confused by ", funcname(f), "\n") + throw("reflect mismatch") + } + bv := mv.stack + arglen = uintptr(bv.n * sys.PtrSize) + if !retValid { + arglen = uintptr(mv.argLen) &^ (sys.PtrSize - 1) + } + argmap = bv + } + } + return +} + +// tracebackCgoContext handles tracing back a cgo context value, from +// the context argument to setCgoTraceback, for the gentraceback +// function. It returns the new value of n. +func tracebackCgoContext(pcbuf *uintptr, printing bool, ctxt uintptr, n, max int) int { + var cgoPCs [32]uintptr + cgoContextPCs(ctxt, cgoPCs[:]) + var arg cgoSymbolizerArg + anySymbolized := false + for _, pc := range cgoPCs { + if pc == 0 || n >= max { + break + } + if pcbuf != nil { + (*[1 << 20]uintptr)(unsafe.Pointer(pcbuf))[n] = pc + } + if printing { + if cgoSymbolizer == nil { + print("non-Go function at pc=", hex(pc), "\n") + } else { + c := printOneCgoTraceback(pc, max-n, &arg) + n += c - 1 // +1 a few lines down + anySymbolized = true + } + } + n++ + } + if anySymbolized { + arg.pc = 0 + callCgoSymbolizer(&arg) + } + return n +} + +func printcreatedby(gp *g) { + // Show what created goroutine, except main goroutine (goid 1). + pc := gp.gopc + f := findfunc(pc) + if f.valid() && showframe(f, gp, false, funcID_normal, funcID_normal) && gp.goid != 1 { + printcreatedby1(f, pc) + } +} + +func printcreatedby1(f funcInfo, pc uintptr) { + print("created by ", funcname(f), "\n") + tracepc := pc // back up to CALL instruction for funcline. + if pc > f.entry { + tracepc -= sys.PCQuantum + } + file, line := funcline(f, tracepc) + print("\t", file, ":", line) + if pc > f.entry { + print(" +", hex(pc-f.entry)) + } + print("\n") +} + +func traceback(pc, sp, lr uintptr, gp *g) { + traceback1(pc, sp, lr, gp, 0) +} + +// tracebacktrap is like traceback but expects that the PC and SP were obtained +// from a trap, not from gp->sched or gp->syscallpc/gp->syscallsp or getcallerpc/getcallersp. +// Because they are from a trap instead of from a saved pair, +// the initial PC must not be rewound to the previous instruction. +// (All the saved pairs record a PC that is a return address, so we +// rewind it into the CALL instruction.) +// If gp.m.libcall{g,pc,sp} information is available, it uses that information in preference to +// the pc/sp/lr passed in. +func tracebacktrap(pc, sp, lr uintptr, gp *g) { + if gp.m.libcallsp != 0 { + // We're in C code somewhere, traceback from the saved position. + traceback1(gp.m.libcallpc, gp.m.libcallsp, 0, gp.m.libcallg.ptr(), 0) + return + } + traceback1(pc, sp, lr, gp, _TraceTrap) +} + +func traceback1(pc, sp, lr uintptr, gp *g, flags uint) { + // If the goroutine is in cgo, and we have a cgo traceback, print that. + if iscgo && gp.m != nil && gp.m.ncgo > 0 && gp.syscallsp != 0 && gp.m.cgoCallers != nil && gp.m.cgoCallers[0] != 0 { + // Lock cgoCallers so that a signal handler won't + // change it, copy the array, reset it, unlock it. + // We are locked to the thread and are not running + // concurrently with a signal handler. + // We just have to stop a signal handler from interrupting + // in the middle of our copy. + atomic.Store(&gp.m.cgoCallersUse, 1) + cgoCallers := *gp.m.cgoCallers + gp.m.cgoCallers[0] = 0 + atomic.Store(&gp.m.cgoCallersUse, 0) + + printCgoTraceback(&cgoCallers) + } + + var n int + if readgstatus(gp)&^_Gscan == _Gsyscall { + // Override registers if blocked in system call. + pc = gp.syscallpc + sp = gp.syscallsp + flags &^= _TraceTrap + } + // Print traceback. By default, omits runtime frames. + // If that means we print nothing at all, repeat forcing all frames printed. + n = gentraceback(pc, sp, lr, gp, 0, nil, _TracebackMaxFrames, nil, nil, flags) + if n == 0 && (flags&_TraceRuntimeFrames) == 0 { + n = gentraceback(pc, sp, lr, gp, 0, nil, _TracebackMaxFrames, nil, nil, flags|_TraceRuntimeFrames) + } + if n == _TracebackMaxFrames { + print("...additional frames elided...\n") + } + printcreatedby(gp) + + if gp.ancestors == nil { + return + } + for _, ancestor := range *gp.ancestors { + printAncestorTraceback(ancestor) + } +} + +// printAncestorTraceback prints the traceback of the given ancestor. +// TODO: Unify this with gentraceback and CallersFrames. +func printAncestorTraceback(ancestor ancestorInfo) { + print("[originating from goroutine ", ancestor.goid, "]:\n") + for fidx, pc := range ancestor.pcs { + f := findfunc(pc) // f previously validated + if showfuncinfo(f, fidx == 0, funcID_normal, funcID_normal) { + printAncestorTracebackFuncInfo(f, pc) + } + } + if len(ancestor.pcs) == _TracebackMaxFrames { + print("...additional frames elided...\n") + } + // Show what created goroutine, except main goroutine (goid 1). + f := findfunc(ancestor.gopc) + if f.valid() && showfuncinfo(f, false, funcID_normal, funcID_normal) && ancestor.goid != 1 { + printcreatedby1(f, ancestor.gopc) + } +} + +// printAncestorTraceback prints the given function info at a given pc +// within an ancestor traceback. The precision of this info is reduced +// due to only have access to the pcs at the time of the caller +// goroutine being created. +func printAncestorTracebackFuncInfo(f funcInfo, pc uintptr) { + name := funcname(f) + if inldata := funcdata(f, _FUNCDATA_InlTree); inldata != nil { + inltree := (*[1 << 20]inlinedCall)(inldata) + ix := pcdatavalue(f, _PCDATA_InlTreeIndex, pc, nil) + if ix >= 0 { + name = funcnameFromNameoff(f, inltree[ix].func_) + } + } + file, line := funcline(f, pc) + if name == "runtime.gopanic" { + name = "panic" + } + print(name, "(...)\n") + print("\t", file, ":", line) + if pc > f.entry { + print(" +", hex(pc-f.entry)) + } + print("\n") +} + +func callers(skip int, pcbuf []uintptr) int { + sp := getcallersp() + pc := getcallerpc() + gp := getg() + var n int + systemstack(func() { + n = gentraceback(pc, sp, 0, gp, skip, &pcbuf[0], len(pcbuf), nil, nil, 0) + }) + return n +} + +func gcallers(gp *g, skip int, pcbuf []uintptr) int { + return gentraceback(^uintptr(0), ^uintptr(0), 0, gp, skip, &pcbuf[0], len(pcbuf), nil, nil, 0) +} + +// showframe reports whether the frame with the given characteristics should +// be printed during a traceback. +func showframe(f funcInfo, gp *g, firstFrame bool, funcID, childID funcID) bool { + g := getg() + if g.m.throwing > 0 && gp != nil && (gp == g.m.curg || gp == g.m.caughtsig.ptr()) { + return true + } + return showfuncinfo(f, firstFrame, funcID, childID) +} + +// showfuncinfo reports whether a function with the given characteristics should +// be printed during a traceback. +func showfuncinfo(f funcInfo, firstFrame bool, funcID, childID funcID) bool { + // Note that f may be a synthesized funcInfo for an inlined + // function, in which case only nameoff and funcID are set. + + level, _, _ := gotraceback() + if level > 1 { + // Show all frames. + return true + } + + if !f.valid() { + return false + } + + if funcID == funcID_wrapper && elideWrapperCalling(childID) { + return false + } + + name := funcname(f) + + // Special case: always show runtime.gopanic frame + // in the middle of a stack trace, so that we can + // see the boundary between ordinary code and + // panic-induced deferred code. + // See golang.org/issue/5832. + if name == "runtime.gopanic" && !firstFrame { + return true + } + + return bytealg.IndexByteString(name, '.') >= 0 && (!hasPrefix(name, "runtime.") || isExportedRuntime(name)) +} + +// isExportedRuntime reports whether name is an exported runtime function. +// It is only for runtime functions, so ASCII A-Z is fine. +func isExportedRuntime(name string) bool { + const n = len("runtime.") + return len(name) > n && name[:n] == "runtime." && 'A' <= name[n] && name[n] <= 'Z' +} + +// elideWrapperCalling reports whether a wrapper function that called +// function id should be elided from stack traces. +func elideWrapperCalling(id funcID) bool { + // If the wrapper called a panic function instead of the + // wrapped function, we want to include it in stacks. + return !(id == funcID_gopanic || id == funcID_sigpanic || id == funcID_panicwrap) +} + +var gStatusStrings = [...]string{ + _Gidle: "idle", + _Grunnable: "runnable", + _Grunning: "running", + _Gsyscall: "syscall", + _Gwaiting: "waiting", + _Gdead: "dead", + _Gcopystack: "copystack", + _Gpreempted: "preempted", +} + +func goroutineheader(gp *g) { + gpstatus := readgstatus(gp) + + isScan := gpstatus&_Gscan != 0 + gpstatus &^= _Gscan // drop the scan bit + + // Basic string status + var status string + if 0 <= gpstatus && gpstatus < uint32(len(gStatusStrings)) { + status = gStatusStrings[gpstatus] + } else { + status = "???" + } + + // Override. + if gpstatus == _Gwaiting && gp.waitreason != waitReasonZero { + status = gp.waitreason.String() + } + + // approx time the G is blocked, in minutes + var waitfor int64 + if (gpstatus == _Gwaiting || gpstatus == _Gsyscall) && gp.waitsince != 0 { + waitfor = (nanotime() - gp.waitsince) / 60e9 + } + print("goroutine ", gp.goid, " [", status) + if isScan { + print(" (scan)") + } + if waitfor >= 1 { + print(", ", waitfor, " minutes") + } + if gp.lockedm != 0 { + print(", locked to thread") + } + print("]:\n") +} + +func tracebackothers(me *g) { + level, _, _ := gotraceback() + + // Show the current goroutine first, if we haven't already. + curgp := getg().m.curg + if curgp != nil && curgp != me { + print("\n") + goroutineheader(curgp) + traceback(^uintptr(0), ^uintptr(0), 0, curgp) + } + + // We can't take allglock here because this may be during fatal + // throw/panic, where locking allglock could be out-of-order or a + // direct deadlock. + // + // Instead, use atomic access to allgs which requires no locking. We + // don't lock against concurrent creation of new Gs, but even with + // allglock we may miss Gs created after this loop. + ptr, length := atomicAllG() + for i := uintptr(0); i < length; i++ { + gp := atomicAllGIndex(ptr, i) + + if gp == me || gp == curgp || readgstatus(gp) == _Gdead || isSystemGoroutine(gp, false) && level < 2 { + continue + } + print("\n") + goroutineheader(gp) + // Note: gp.m == g.m occurs when tracebackothers is + // called from a signal handler initiated during a + // systemstack call. The original G is still in the + // running state, and we want to print its stack. + if gp.m != getg().m && readgstatus(gp)&^_Gscan == _Grunning { + print("\tgoroutine running on other thread; stack unavailable\n") + printcreatedby(gp) + } else { + traceback(^uintptr(0), ^uintptr(0), 0, gp) + } + } +} + +// tracebackHexdump hexdumps part of stk around frame.sp and frame.fp +// for debugging purposes. If the address bad is included in the +// hexdumped range, it will mark it as well. +func tracebackHexdump(stk stack, frame *stkframe, bad uintptr) { + const expand = 32 * sys.PtrSize + const maxExpand = 256 * sys.PtrSize + // Start around frame.sp. + lo, hi := frame.sp, frame.sp + // Expand to include frame.fp. + if frame.fp != 0 && frame.fp < lo { + lo = frame.fp + } + if frame.fp != 0 && frame.fp > hi { + hi = frame.fp + } + // Expand a bit more. + lo, hi = lo-expand, hi+expand + // But don't go too far from frame.sp. + if lo < frame.sp-maxExpand { + lo = frame.sp - maxExpand + } + if hi > frame.sp+maxExpand { + hi = frame.sp + maxExpand + } + // And don't go outside the stack bounds. + if lo < stk.lo { + lo = stk.lo + } + if hi > stk.hi { + hi = stk.hi + } + + // Print the hex dump. + print("stack: frame={sp:", hex(frame.sp), ", fp:", hex(frame.fp), "} stack=[", hex(stk.lo), ",", hex(stk.hi), ")\n") + hexdumpWords(lo, hi, func(p uintptr) byte { + switch p { + case frame.fp: + return '>' + case frame.sp: + return '<' + case bad: + return '!' + } + return 0 + }) +} + +// Does f mark the top of a goroutine stack? +func topofstack(f funcInfo, g0 bool) bool { + return f.funcID == funcID_goexit || + f.funcID == funcID_mstart || + f.funcID == funcID_mcall || + f.funcID == funcID_morestack || + f.funcID == funcID_rt0_go || + f.funcID == funcID_externalthreadhandler || + // asmcgocall is TOS on the system stack because it + // switches to the system stack, but in this case we + // can come back to the regular stack and still want + // to be able to unwind through the call that appeared + // on the regular stack. + (g0 && f.funcID == funcID_asmcgocall) +} + +// isSystemGoroutine reports whether the goroutine g must be omitted +// in stack dumps and deadlock detector. This is any goroutine that +// starts at a runtime.* entry point, except for runtime.main, +// runtime.handleAsyncEvent (wasm only) and sometimes runtime.runfinq. +// +// If fixed is true, any goroutine that can vary between user and +// system (that is, the finalizer goroutine) is considered a user +// goroutine. +func isSystemGoroutine(gp *g, fixed bool) bool { + // Keep this in sync with cmd/trace/trace.go:isSystemGoroutine. + f := findfunc(gp.startpc) + if !f.valid() { + return false + } + if f.funcID == funcID_runtime_main || f.funcID == funcID_handleAsyncEvent { + return false + } + if f.funcID == funcID_runfinq { + // We include the finalizer goroutine if it's calling + // back into user code. + if fixed { + // This goroutine can vary. In fixed mode, + // always consider it a user goroutine. + return false + } + return !fingRunning + } + return hasPrefix(funcname(f), "runtime.") +} + +// SetCgoTraceback records three C functions to use to gather +// traceback information from C code and to convert that traceback +// information into symbolic information. These are used when printing +// stack traces for a program that uses cgo. +// +// The traceback and context functions may be called from a signal +// handler, and must therefore use only async-signal safe functions. +// The symbolizer function may be called while the program is +// crashing, and so must be cautious about using memory. None of the +// functions may call back into Go. +// +// The context function will be called with a single argument, a +// pointer to a struct: +// +// struct { +// Context uintptr +// } +// +// In C syntax, this struct will be +// +// struct { +// uintptr_t Context; +// }; +// +// If the Context field is 0, the context function is being called to +// record the current traceback context. It should record in the +// Context field whatever information is needed about the current +// point of execution to later produce a stack trace, probably the +// stack pointer and PC. In this case the context function will be +// called from C code. +// +// If the Context field is not 0, then it is a value returned by a +// previous call to the context function. This case is called when the +// context is no longer needed; that is, when the Go code is returning +// to its C code caller. This permits the context function to release +// any associated resources. +// +// While it would be correct for the context function to record a +// complete a stack trace whenever it is called, and simply copy that +// out in the traceback function, in a typical program the context +// function will be called many times without ever recording a +// traceback for that context. Recording a complete stack trace in a +// call to the context function is likely to be inefficient. +// +// The traceback function will be called with a single argument, a +// pointer to a struct: +// +// struct { +// Context uintptr +// SigContext uintptr +// Buf *uintptr +// Max uintptr +// } +// +// In C syntax, this struct will be +// +// struct { +// uintptr_t Context; +// uintptr_t SigContext; +// uintptr_t* Buf; +// uintptr_t Max; +// }; +// +// The Context field will be zero to gather a traceback from the +// current program execution point. In this case, the traceback +// function will be called from C code. +// +// Otherwise Context will be a value previously returned by a call to +// the context function. The traceback function should gather a stack +// trace from that saved point in the program execution. The traceback +// function may be called from an execution thread other than the one +// that recorded the context, but only when the context is known to be +// valid and unchanging. The traceback function may also be called +// deeper in the call stack on the same thread that recorded the +// context. The traceback function may be called multiple times with +// the same Context value; it will usually be appropriate to cache the +// result, if possible, the first time this is called for a specific +// context value. +// +// If the traceback function is called from a signal handler on a Unix +// system, SigContext will be the signal context argument passed to +// the signal handler (a C ucontext_t* cast to uintptr_t). This may be +// used to start tracing at the point where the signal occurred. If +// the traceback function is not called from a signal handler, +// SigContext will be zero. +// +// Buf is where the traceback information should be stored. It should +// be PC values, such that Buf[0] is the PC of the caller, Buf[1] is +// the PC of that function's caller, and so on. Max is the maximum +// number of entries to store. The function should store a zero to +// indicate the top of the stack, or that the caller is on a different +// stack, presumably a Go stack. +// +// Unlike runtime.Callers, the PC values returned should, when passed +// to the symbolizer function, return the file/line of the call +// instruction. No additional subtraction is required or appropriate. +// +// On all platforms, the traceback function is invoked when a call from +// Go to C to Go requests a stack trace. On linux/amd64, linux/ppc64le, +// and freebsd/amd64, the traceback function is also invoked when a +// signal is received by a thread that is executing a cgo call. The +// traceback function should not make assumptions about when it is +// called, as future versions of Go may make additional calls. +// +// The symbolizer function will be called with a single argument, a +// pointer to a struct: +// +// struct { +// PC uintptr // program counter to fetch information for +// File *byte // file name (NUL terminated) +// Lineno uintptr // line number +// Func *byte // function name (NUL terminated) +// Entry uintptr // function entry point +// More uintptr // set non-zero if more info for this PC +// Data uintptr // unused by runtime, available for function +// } +// +// In C syntax, this struct will be +// +// struct { +// uintptr_t PC; +// char* File; +// uintptr_t Lineno; +// char* Func; +// uintptr_t Entry; +// uintptr_t More; +// uintptr_t Data; +// }; +// +// The PC field will be a value returned by a call to the traceback +// function. +// +// The first time the function is called for a particular traceback, +// all the fields except PC will be 0. The function should fill in the +// other fields if possible, setting them to 0/nil if the information +// is not available. The Data field may be used to store any useful +// information across calls. The More field should be set to non-zero +// if there is more information for this PC, zero otherwise. If More +// is set non-zero, the function will be called again with the same +// PC, and may return different information (this is intended for use +// with inlined functions). If More is zero, the function will be +// called with the next PC value in the traceback. When the traceback +// is complete, the function will be called once more with PC set to +// zero; this may be used to free any information. Each call will +// leave the fields of the struct set to the same values they had upon +// return, except for the PC field when the More field is zero. The +// function must not keep a copy of the struct pointer between calls. +// +// When calling SetCgoTraceback, the version argument is the version +// number of the structs that the functions expect to receive. +// Currently this must be zero. +// +// The symbolizer function may be nil, in which case the results of +// the traceback function will be displayed as numbers. If the +// traceback function is nil, the symbolizer function will never be +// called. The context function may be nil, in which case the +// traceback function will only be called with the context field set +// to zero. If the context function is nil, then calls from Go to C +// to Go will not show a traceback for the C portion of the call stack. +// +// SetCgoTraceback should be called only once, ideally from an init function. +func SetCgoTraceback(version int, traceback, context, symbolizer unsafe.Pointer) { + if version != 0 { + panic("unsupported version") + } + + if cgoTraceback != nil && cgoTraceback != traceback || + cgoContext != nil && cgoContext != context || + cgoSymbolizer != nil && cgoSymbolizer != symbolizer { + panic("call SetCgoTraceback only once") + } + + cgoTraceback = traceback + cgoContext = context + cgoSymbolizer = symbolizer + + // The context function is called when a C function calls a Go + // function. As such it is only called by C code in runtime/cgo. + if _cgo_set_context_function != nil { + cgocall(_cgo_set_context_function, context) + } +} + +var cgoTraceback unsafe.Pointer +var cgoContext unsafe.Pointer +var cgoSymbolizer unsafe.Pointer + +// cgoTracebackArg is the type passed to cgoTraceback. +type cgoTracebackArg struct { + context uintptr + sigContext uintptr + buf *uintptr + max uintptr +} + +// cgoContextArg is the type passed to the context function. +type cgoContextArg struct { + context uintptr +} + +// cgoSymbolizerArg is the type passed to cgoSymbolizer. +type cgoSymbolizerArg struct { + pc uintptr + file *byte + lineno uintptr + funcName *byte + entry uintptr + more uintptr + data uintptr +} + +// cgoTraceback prints a traceback of callers. +func printCgoTraceback(callers *cgoCallers) { + if cgoSymbolizer == nil { + for _, c := range callers { + if c == 0 { + break + } + print("non-Go function at pc=", hex(c), "\n") + } + return + } + + var arg cgoSymbolizerArg + for _, c := range callers { + if c == 0 { + break + } + printOneCgoTraceback(c, 0x7fffffff, &arg) + } + arg.pc = 0 + callCgoSymbolizer(&arg) +} + +// printOneCgoTraceback prints the traceback of a single cgo caller. +// This can print more than one line because of inlining. +// Returns the number of frames printed. +func printOneCgoTraceback(pc uintptr, max int, arg *cgoSymbolizerArg) int { + c := 0 + arg.pc = pc + for c <= max { + callCgoSymbolizer(arg) + if arg.funcName != nil { + // Note that we don't print any argument + // information here, not even parentheses. + // The symbolizer must add that if appropriate. + println(gostringnocopy(arg.funcName)) + } else { + println("non-Go function") + } + print("\t") + if arg.file != nil { + print(gostringnocopy(arg.file), ":", arg.lineno, " ") + } + print("pc=", hex(pc), "\n") + c++ + if arg.more == 0 { + break + } + } + return c +} + +// callCgoSymbolizer calls the cgoSymbolizer function. +func callCgoSymbolizer(arg *cgoSymbolizerArg) { + call := cgocall + if panicking > 0 || getg().m.curg != getg() { + // We do not want to call into the scheduler when panicking + // or when on the system stack. + call = asmcgocall + } + if msanenabled { + msanwrite(unsafe.Pointer(arg), unsafe.Sizeof(cgoSymbolizerArg{})) + } + call(cgoSymbolizer, noescape(unsafe.Pointer(arg))) +} + +// cgoContextPCs gets the PC values from a cgo traceback. +func cgoContextPCs(ctxt uintptr, buf []uintptr) { + if cgoTraceback == nil { + return + } + call := cgocall + if panicking > 0 || getg().m.curg != getg() { + // We do not want to call into the scheduler when panicking + // or when on the system stack. + call = asmcgocall + } + arg := cgoTracebackArg{ + context: ctxt, + buf: (*uintptr)(noescape(unsafe.Pointer(&buf[0]))), + max: uintptr(len(buf)), + } + if msanenabled { + msanwrite(unsafe.Pointer(&arg), unsafe.Sizeof(arg)) + } + call(cgoTraceback, noescape(unsafe.Pointer(&arg))) +} |