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Diffstat (limited to '')
| -rw-r--r-- | src/runtime/traceback.go | 1648 |
1 files changed, 1648 insertions, 0 deletions
diff --git a/src/runtime/traceback.go b/src/runtime/traceback.go new file mode 100644 index 0000000..1e5afc6 --- /dev/null +++ b/src/runtime/traceback.go @@ -0,0 +1,1648 @@ +// 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/abi" + "internal/bytealg" + "internal/goarch" + "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 (x86), 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. + +const usesLR = sys.MinFrameSize > 0 + +const ( + // tracebackInnerFrames is the number of innermost frames to print in a + // stack trace. The total maximum frames is tracebackInnerFrames + + // tracebackOuterFrames. + tracebackInnerFrames = 50 + + // tracebackOuterFrames is the number of outermost frames to print in a + // stack trace. + tracebackOuterFrames = 50 +) + +// unwindFlags control the behavior of various unwinders. +type unwindFlags uint8 + +const ( + // unwindPrintErrors indicates that if unwinding encounters an error, it + // should print a message and stop without throwing. This is used for things + // like stack printing, where it's better to get incomplete information than + // to crash. This is also used in situations where everything may not be + // stopped nicely and the stack walk may not be able to complete, such as + // during profiling signals or during a crash. + // + // If neither unwindPrintErrors or unwindSilentErrors are set, unwinding + // performs extra consistency checks and throws on any error. + // + // Note that there are a small number of fatal situations that will throw + // regardless of unwindPrintErrors or unwindSilentErrors. + unwindPrintErrors unwindFlags = 1 << iota + + // unwindSilentErrors silently ignores errors during unwinding. + unwindSilentErrors + + // unwindTrap indicates that the initial PC and SP are from a trap, not a + // return PC from a call. + // + // The unwindTrap flag is updated during unwinding. If set, frame.pc is the + // address of a faulting instruction instead of the return address of a + // call. It also means the liveness at pc may not be known. + // + // TODO: Distinguish frame.continpc, which is really the stack map PC, from + // the actual continuation PC, which is computed differently depending on + // this flag and a few other things. + unwindTrap + + // unwindJumpStack indicates that, if the traceback is on a system stack, it + // should resume tracing at the user stack when the system stack is + // exhausted. + unwindJumpStack +) + +// An unwinder iterates the physical stack frames of a Go sack. +// +// Typical use of an unwinder looks like: +// +// var u unwinder +// for u.init(gp, 0); u.valid(); u.next() { +// // ... use frame info in u ... +// } +// +// Implementation note: This is carefully structured to be pointer-free because +// tracebacks happen in places that disallow write barriers (e.g., signals). +// Even if this is stack-allocated, its pointer-receiver methods don't know that +// their receiver is on the stack, so they still emit write barriers. Here we +// address that by carefully avoiding any pointers in this type. Another +// approach would be to split this into a mutable part that's passed by pointer +// but contains no pointers itself and an immutable part that's passed and +// returned by value and can contain pointers. We could potentially hide that +// we're doing that in trivial methods that are inlined into the caller that has +// the stack allocation, but that's fragile. +type unwinder struct { + // frame is the current physical stack frame, or all 0s if + // there is no frame. + frame stkframe + + // g is the G who's stack is being unwound. If the + // unwindJumpStack flag is set and the unwinder jumps stacks, + // this will be different from the initial G. + g guintptr + + // cgoCtxt is the index into g.cgoCtxt of the next frame on the cgo stack. + // The cgo stack is unwound in tandem with the Go stack as we find marker frames. + cgoCtxt int + + // calleeFuncID is the function ID of the caller of the current + // frame. + calleeFuncID abi.FuncID + + // flags are the flags to this unwind. Some of these are updated as we + // unwind (see the flags documentation). + flags unwindFlags +} + +// init initializes u to start unwinding gp's stack and positions the +// iterator on gp's innermost frame. gp must not be the current G. +// +// A single unwinder can be reused for multiple unwinds. +func (u *unwinder) init(gp *g, flags unwindFlags) { + // Implementation note: This starts the iterator on the first frame and we + // provide a "valid" method. Alternatively, this could start in a "before + // the first frame" state and "next" could return whether it was able to + // move to the next frame, but that's both more awkward to use in a "for" + // loop and is harder to implement because we have to do things differently + // for the first frame. + u.initAt(^uintptr(0), ^uintptr(0), ^uintptr(0), gp, flags) +} + +func (u *unwinder) initAt(pc0, sp0, lr0 uintptr, gp *g, flags unwindFlags) { + // 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 traceback 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 initAt 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("cannot trace user goroutine on its own stack") + } + + 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 + } + } + } + + var frame stkframe + frame.pc = pc0 + frame.sp = sp0 + if usesLR { + frame.lr = lr0 + } + + // 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)(unsafe.Pointer(frame.sp)) + frame.sp += goarch.PtrSize + } + } + + // runtime/internal/atomic functions call into kernel helpers on + // arm < 7. See runtime/internal/atomic/sys_linux_arm.s. + // + // Start in the caller's frame. + if GOARCH == "arm" && goarm < 7 && GOOS == "linux" && frame.pc&0xffff0000 == 0xffff0000 { + // Note that the calls are simple BL without pushing the return + // address, so we use LR directly. + // + // The kernel helpers are frameless leaf functions, so SP and + // LR are not touched. + frame.pc = frame.lr + frame.lr = 0 + } + + f := findfunc(frame.pc) + if !f.valid() { + if flags&unwindSilentErrors == 0 { + print("runtime: g ", gp.goid, " gp=", gp, ": unknown pc ", hex(frame.pc), "\n") + tracebackHexdump(gp.stack, &frame, 0) + } + if flags&(unwindPrintErrors|unwindSilentErrors) == 0 { + throw("unknown pc") + } + *u = unwinder{} + return + } + frame.fn = f + + // Populate the unwinder. + *u = unwinder{ + frame: frame, + g: gp.guintptr(), + cgoCtxt: len(gp.cgoCtxt) - 1, + calleeFuncID: abi.FuncIDNormal, + flags: flags, + } + + isSyscall := frame.pc == pc0 && frame.sp == sp0 && pc0 == gp.syscallpc && sp0 == gp.syscallsp + u.resolveInternal(true, isSyscall) +} + +func (u *unwinder) valid() bool { + return u.frame.pc != 0 +} + +// resolveInternal fills in u.frame based on u.frame.fn, pc, and sp. +// +// innermost indicates that this is the first resolve on this stack. If +// innermost is set, isSyscall indicates that the PC/SP was retrieved from +// gp.syscall*; this is otherwise ignored. +// +// On entry, u.frame contains: +// - fn is the running function. +// - pc is the PC in the running function. +// - sp is the stack pointer at that program counter. +// - For the innermost frame on LR machines, lr is the program counter that called fn. +// +// On return, u.frame contains: +// - fp is the stack pointer of the caller. +// - lr is the program counter that called fn. +// - varp, argp, and continpc are populated for the current frame. +// +// If fn is a stack-jumping function, resolveInternal can change the entire +// frame state to follow that stack jump. +// +// This is internal to unwinder. +func (u *unwinder) resolveInternal(innermost, isSyscall bool) { + frame := &u.frame + gp := u.g.ptr() + + f := frame.fn + if f.pcsp == 0 { + // No frame information, must be external function, like race support. + // See golang.org/issue/13568. + u.finishInternal() + return + } + + // Compute function info flags. + flag := f.flag + if f.funcID == abi.FuncID_cgocallback { + // cgocallback does write SP to switch from the g0 to the curg stack, + // but it carefully arranges that during the transition BOTH stacks + // have cgocallback frame valid for unwinding through. + // So we don't need to exclude it with the other SP-writing functions. + flag &^= abi.FuncFlagSPWrite + } + if isSyscall { + // Some Syscall functions write to SP, but they do so only after + // saving the entry PC/SP using entersyscall. + // Since we are using the entry PC/SP, the later SP write doesn't matter. + flag &^= abi.FuncFlagSPWrite + } + + // Found an actual function. + // Derive frame pointer. + 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. + // We also defensively check that this won't switch M's on us, + // which could happen at critical points in the scheduler. + // This ensures gp.m doesn't change from a stack jump. + if u.flags&unwindJumpStack != 0 && gp == gp.m.g0 && gp.m.curg != nil && gp.m.curg.m == gp.m { + switch f.funcID { + case abi.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. + gp = gp.m.curg + u.g.set(gp) + frame.pc = gp.sched.pc + frame.fn = findfunc(frame.pc) + f = frame.fn + flag = f.flag + frame.lr = gp.sched.lr + frame.sp = gp.sched.sp + u.cgoCtxt = len(gp.cgoCtxt) - 1 + case abi.FuncID_systemstack: + // systemstack returns normally, so just follow the + // stack transition. + if usesLR && funcspdelta(f, frame.pc) == 0 { + // We're at the function prologue and the stack + // switch hasn't happened, or epilogue where we're + // about to return. Just unwind normally. + // Do this only on LR machines because on x86 + // systemstack doesn't have an SP delta (the CALL + // instruction opens the frame), therefore no way + // to check. + flag &^= abi.FuncFlagSPWrite + break + } + gp = gp.m.curg + u.g.set(gp) + frame.sp = gp.sched.sp + u.cgoCtxt = len(gp.cgoCtxt) - 1 + flag &^= abi.FuncFlagSPWrite + } + } + frame.fp = frame.sp + uintptr(funcspdelta(f, frame.pc)) + if !usesLR { + // On x86, call instruction pushes return PC before entering new function. + frame.fp += goarch.PtrSize + } + } + + // Derive link register. + if flag&abi.FuncFlagTopFrame != 0 { + // This function marks the top of the stack. Stop the traceback. + frame.lr = 0 + } else if flag&abi.FuncFlagSPWrite != 0 && (!innermost || u.flags&(unwindPrintErrors|unwindSilentErrors) != 0) { + // The function we are in does a write to SP that we don't know + // how to encode in the spdelta table. Examples include context + // switch routines like runtime.gogo but also any code that switches + // to the g0 stack to run host C code. + // We can't reliably unwind the SP (we might not even be on + // the stack we think we are), so stop the traceback here. + // + // The one exception (encoded in the complex condition above) is that + // we assume if we're doing a precise traceback, and this is the + // innermost frame, that the SPWRITE function voluntarily preempted itself on entry + // during the stack growth check. In that case, the function has + // not yet had a chance to do any writes to SP and is safe to unwind. + // isAsyncSafePoint does not allow assembly functions to be async preempted, + // and preemptPark double-checks that SPWRITE functions are not async preempted. + // So for GC stack traversal, we can safely ignore SPWRITE for the innermost frame, + // but farther up the stack we'd better not find any. + // This is somewhat imprecise because we're just guessing that we're in the stack + // growth check. It would be better if SPWRITE were encoded in the spdelta + // table so we would know for sure that we were still in safe code. + // + // uSE uPE inn | action + // T _ _ | frame.lr = 0 + // F T _ | frame.lr = 0 + // F F F | print; panic + // F F T | ignore SPWrite + if u.flags&(unwindPrintErrors|unwindSilentErrors) == 0 && !innermost { + println("traceback: unexpected SPWRITE function", funcname(f)) + throw("traceback") + } + frame.lr = 0 + } else { + var lrPtr uintptr + if usesLR { + if innermost && frame.sp < frame.fp || frame.lr == 0 { + lrPtr = frame.sp + frame.lr = *(*uintptr)(unsafe.Pointer(lrPtr)) + } + } else { + if frame.lr == 0 { + lrPtr = frame.fp - goarch.PtrSize + frame.lr = *(*uintptr)(unsafe.Pointer(lrPtr)) + } + } + } + + frame.varp = frame.fp + if !usesLR { + // On x86, call instruction pushes return PC before entering new function. + frame.varp -= goarch.PtrSize + } + + // For architectures with frame pointers, if there's + // a frame, then there's a saved frame pointer here. + // + // NOTE: This code is not as general as it looks. + // On x86, the ABI is to save the frame pointer word at the + // top of the stack frame, so we have to back down over it. + // On arm64, the frame pointer should be at the bottom of + // the stack (with R29 (aka FP) = RSP), in which case we would + // not want to do the subtraction here. But we started out without + // any frame pointer, and when we wanted to add it, we didn't + // want to break all the assembly doing direct writes to 8(RSP) + // to set the first parameter to a called function. + // So we decided to write the FP link *below* the stack pointer + // (with R29 = RSP - 8 in Go functions). + // This is technically ABI-compatible but not standard. + // And it happens to end up mimicking the x86 layout. + // Other architectures may make different decisions. + if frame.varp > frame.sp && framepointer_enabled { + frame.varp -= goarch.PtrSize + } + + frame.argp = frame.fp + sys.MinFrameSize + + // 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 u.calleeFuncID == abi.FuncID_sigpanic { + 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 + } + } +} + +func (u *unwinder) next() { + frame := &u.frame + f := frame.fn + gp := u.g.ptr() + + // Do not unwind past the bottom of the stack. + if frame.lr == 0 { + u.finishInternal() + return + } + 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 no error flags are set, we're doing a garbage collection and must + // get everything, so crash loudly. + fail := u.flags&(unwindPrintErrors|unwindSilentErrors) == 0 + doPrint := u.flags&unwindSilentErrors == 0 + if doPrint && gp.m.incgo && f.funcID == abi.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 fail || doPrint { + print("runtime: g ", gp.goid, ": unexpected return pc for ", funcname(f), " called from ", hex(frame.lr), "\n") + tracebackHexdump(gp.stack, frame, 0) + } + if fail { + throw("unknown caller pc") + } + frame.lr = 0 + u.finishInternal() + return + } + + if frame.pc == frame.lr && frame.sp == frame.fp { + // If the next frame is identical to the current frame, we cannot make progress. + print("runtime: traceback stuck. pc=", hex(frame.pc), " sp=", hex(frame.sp), "\n") + tracebackHexdump(gp.stack, frame, frame.sp) + throw("traceback stuck") + } + + injectedCall := f.funcID == abi.FuncID_sigpanic || f.funcID == abi.FuncID_asyncPreempt || f.funcID == abi.FuncID_debugCallV2 + if injectedCall { + u.flags |= unwindTrap + } else { + u.flags &^= unwindTrap + } + + // Unwind to next frame. + u.calleeFuncID = f.funcID + frame.fn = flr + frame.pc = frame.lr + frame.lr = 0 + frame.sp = frame.fp + frame.fp = 0 + + // 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 += alignUp(sys.MinFrameSize, sys.StackAlign) + f = findfunc(frame.pc) + frame.fn = f + if !f.valid() { + frame.pc = x + } else if funcspdelta(f, frame.pc) == 0 { + frame.lr = x + } + } + + u.resolveInternal(false, false) +} + +// finishInternal is an unwinder-internal helper called after the stack has been +// exhausted. It sets the unwinder to an invalid state and checks that it +// successfully unwound the entire stack. +func (u *unwinder) finishInternal() { + u.frame.pc = 0 + + // 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. + gp := u.g.ptr() + if u.flags&(unwindPrintErrors|unwindSilentErrors) == 0 && u.frame.sp != gp.stktopsp { + print("runtime: g", gp.goid, ": frame.sp=", hex(u.frame.sp), " top=", hex(gp.stktopsp), "\n") + print("\tstack=[", hex(gp.stack.lo), "-", hex(gp.stack.hi), "\n") + throw("traceback did not unwind completely") + } +} + +// symPC returns the PC that should be used for symbolizing the current frame. +// Specifically, this is the PC of the last instruction executed in this frame. +// +// If this frame did a normal call, then frame.pc is a return PC, so this will +// return frame.pc-1, which points into the CALL instruction. If the frame was +// interrupted by a signal (e.g., profiler, segv, etc) then frame.pc is for the +// trapped instruction, so this returns frame.pc. See issue #34123. Finally, +// frame.pc can be at function entry when the frame is initialized without +// actually running code, like in runtime.mstart, in which case this returns +// frame.pc because that's the best we can do. +func (u *unwinder) symPC() uintptr { + if u.flags&unwindTrap == 0 && u.frame.pc > u.frame.fn.entry() { + // Regular call. + return u.frame.pc - 1 + } + // Trapping instruction or we're at the function entry point. + return u.frame.pc +} + +// cgoCallers populates pcBuf with the cgo callers of the current frame using +// the registered cgo unwinder. It returns the number of PCs written to pcBuf. +// If the current frame is not a cgo frame or if there's no registered cgo +// unwinder, it returns 0. +func (u *unwinder) cgoCallers(pcBuf []uintptr) int { + if cgoTraceback == nil || u.frame.fn.funcID != abi.FuncID_cgocallback || u.cgoCtxt < 0 { + // We don't have a cgo unwinder (typical case), or we do but we're not + // in a cgo frame or we're out of cgo context. + return 0 + } + + ctxt := u.g.ptr().cgoCtxt[u.cgoCtxt] + u.cgoCtxt-- + cgoContextPCs(ctxt, pcBuf) + for i, pc := range pcBuf { + if pc == 0 { + return i + } + } + return len(pcBuf) +} + +// tracebackPCs populates pcBuf with the return addresses for each frame from u +// and returns the number of PCs written to pcBuf. The returned PCs correspond +// to "logical frames" rather than "physical frames"; that is if A is inlined +// into B, this will still return a PCs for both A and B. This also includes PCs +// generated by the cgo unwinder, if one is registered. +// +// If skip != 0, this skips this many logical frames. +// +// Callers should set the unwindSilentErrors flag on u. +func tracebackPCs(u *unwinder, skip int, pcBuf []uintptr) int { + var cgoBuf [32]uintptr + n := 0 + for ; n < len(pcBuf) && u.valid(); u.next() { + f := u.frame.fn + cgoN := u.cgoCallers(cgoBuf[:]) + + // TODO: Why does &u.cache cause u to escape? (Same in traceback2) + for iu, uf := newInlineUnwinder(f, u.symPC()); n < len(pcBuf) && uf.valid(); uf = iu.next(uf) { + sf := iu.srcFunc(uf) + if sf.funcID == abi.FuncIDWrapper && elideWrapperCalling(u.calleeFuncID) { + // ignore wrappers + } else if skip > 0 { + skip-- + } else { + // Callers expect the pc buffer to contain return addresses + // and do the -1 themselves, so we add 1 to the call PC to + // create a return PC. + pcBuf[n] = uf.pc + 1 + n++ + } + u.calleeFuncID = sf.funcID + } + // Add cgo frames (if we're done skipping over the requested number of + // Go frames). + if skip == 0 { + n += copy(pcBuf[n:], cgoBuf[:cgoN]) + } + } + return n +} + +// printArgs prints function arguments in traceback. +func printArgs(f funcInfo, argp unsafe.Pointer, pc uintptr) { + // The "instruction" of argument printing is encoded in _FUNCDATA_ArgInfo. + // See cmd/compile/internal/ssagen.emitArgInfo for the description of the + // encoding. + // These constants need to be in sync with the compiler. + const ( + _endSeq = 0xff + _startAgg = 0xfe + _endAgg = 0xfd + _dotdotdot = 0xfc + _offsetTooLarge = 0xfb + ) + + const ( + limit = 10 // print no more than 10 args/components + maxDepth = 5 // no more than 5 layers of nesting + maxLen = (maxDepth*3+2)*limit + 1 // max length of _FUNCDATA_ArgInfo (see the compiler side for reasoning) + ) + + p := (*[maxLen]uint8)(funcdata(f, abi.FUNCDATA_ArgInfo)) + if p == nil { + return + } + + liveInfo := funcdata(f, abi.FUNCDATA_ArgLiveInfo) + liveIdx := pcdatavalue(f, abi.PCDATA_ArgLiveIndex, pc) + startOffset := uint8(0xff) // smallest offset that needs liveness info (slots with a lower offset is always live) + if liveInfo != nil { + startOffset = *(*uint8)(liveInfo) + } + + isLive := func(off, slotIdx uint8) bool { + if liveInfo == nil || liveIdx <= 0 { + return true // no liveness info, always live + } + if off < startOffset { + return true + } + bits := *(*uint8)(add(liveInfo, uintptr(liveIdx)+uintptr(slotIdx/8))) + return bits&(1<<(slotIdx%8)) != 0 + } + + print1 := func(off, sz, slotIdx uint8) { + x := readUnaligned64(add(argp, uintptr(off))) + // mask out irrelevant bits + if sz < 8 { + shift := 64 - sz*8 + if goarch.BigEndian { + x = x >> shift + } else { + x = x << shift >> shift + } + } + print(hex(x)) + if !isLive(off, slotIdx) { + print("?") + } + } + + start := true + printcomma := func() { + if !start { + print(", ") + } + } + pi := 0 + slotIdx := uint8(0) // register arg spill slot index +printloop: + for { + o := p[pi] + pi++ + switch o { + case _endSeq: + break printloop + case _startAgg: + printcomma() + print("{") + start = true + continue + case _endAgg: + print("}") + case _dotdotdot: + printcomma() + print("...") + case _offsetTooLarge: + printcomma() + print("_") + default: + printcomma() + sz := p[pi] + pi++ + print1(o, sz, slotIdx) + if o >= startOffset { + slotIdx++ + } + } + start = false + } +} + +// funcNamePiecesForPrint returns the function name for printing to the user. +// It returns three pieces so it doesn't need an allocation for string +// concatenation. +func funcNamePiecesForPrint(name string) (string, string, string) { + // Replace the shape name in generic function with "...". + i := bytealg.IndexByteString(name, '[') + if i < 0 { + return name, "", "" + } + j := len(name) - 1 + for name[j] != ']' { + j-- + } + if j <= i { + return name, "", "" + } + return name[:i], "[...]", name[j+1:] +} + +// funcNameForPrint returns the function name for printing to the user. +func funcNameForPrint(name string) string { + a, b, c := funcNamePiecesForPrint(name) + return a + b + c +} + +// printFuncName prints a function name. name is the function name in +// the binary's func data table. +func printFuncName(name string) { + if name == "runtime.gopanic" { + print("panic") + return + } + a, b, c := funcNamePiecesForPrint(name) + print(a, b, c) +} + +func printcreatedby(gp *g) { + // Show what created goroutine, except main goroutine (goid 1). + pc := gp.gopc + f := findfunc(pc) + if f.valid() && showframe(f.srcFunc(), gp, false, abi.FuncIDNormal) && gp.goid != 1 { + printcreatedby1(f, pc, gp.parentGoid) + } +} + +func printcreatedby1(f funcInfo, pc uintptr, goid uint64) { + print("created by ") + printFuncName(funcname(f)) + if goid != 0 { + print(" in goroutine ", goid) + } + print("\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, unwindTrap) +} + +func traceback1(pc, sp, lr uintptr, gp *g, flags unwindFlags) { + // 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. + gp.m.cgoCallersUse.Store(1) + cgoCallers := *gp.m.cgoCallers + gp.m.cgoCallers[0] = 0 + gp.m.cgoCallersUse.Store(0) + + printCgoTraceback(&cgoCallers) + } + + if readgstatus(gp)&^_Gscan == _Gsyscall { + // Override registers if blocked in system call. + pc = gp.syscallpc + sp = gp.syscallsp + flags &^= unwindTrap + } + if gp.m != nil && gp.m.vdsoSP != 0 { + // Override registers if running in VDSO. This comes after the + // _Gsyscall check to cover VDSO calls after entersyscall. + pc = gp.m.vdsoPC + sp = gp.m.vdsoSP + flags &^= unwindTrap + } + + // Print traceback. + // + // We print the first tracebackInnerFrames frames, and the last + // tracebackOuterFrames frames. There are many possible approaches to this. + // There are various complications to this: + // + // - We'd prefer to walk the stack once because in really bad situations + // traceback may crash (and we want as much output as possible) or the stack + // may be changing. + // + // - Each physical frame can represent several logical frames, so we might + // have to pause in the middle of a physical frame and pick up in the middle + // of a physical frame. + // + // - The cgo symbolizer can expand a cgo PC to more than one logical frame, + // and involves juggling state on the C side that we don't manage. Since its + // expansion state is managed on the C side, we can't capture the expansion + // state part way through, and because the output strings are managed on the + // C side, we can't capture the output. Thus, our only choice is to replay a + // whole expansion, potentially discarding some of it. + // + // Rejected approaches: + // + // - Do two passes where the first pass just counts and the second pass does + // all the printing. This is undesirable if the stack is corrupted or changing + // because we won't see a partial stack if we panic. + // + // - Keep a ring buffer of the last N logical frames and use this to print + // the bottom frames once we reach the end of the stack. This works, but + // requires keeping a surprising amount of state on the stack, and we have + // to run the cgo symbolizer twice—once to count frames, and a second to + // print them—since we can't retain the strings it returns. + // + // Instead, we print the outer frames, and if we reach that limit, we clone + // the unwinder, count the remaining frames, and then skip forward and + // finish printing from the clone. This makes two passes over the outer part + // of the stack, but the single pass over the inner part ensures that's + // printed immediately and not revisited. It keeps minimal state on the + // stack. And through a combination of skip counts and limits, we can do all + // of the steps we need with a single traceback printer implementation. + // + // We could be more lax about exactly how many frames we print, for example + // always stopping and resuming on physical frame boundaries, or at least + // cgo expansion boundaries. It's not clear that's much simpler. + flags |= unwindPrintErrors + var u unwinder + tracebackWithRuntime := func(showRuntime bool) int { + const maxInt int = 0x7fffffff + u.initAt(pc, sp, lr, gp, flags) + n, lastN := traceback2(&u, showRuntime, 0, tracebackInnerFrames) + if n < tracebackInnerFrames { + // We printed the whole stack. + return n + } + // Clone the unwinder and figure out how many frames are left. This + // count will include any logical frames already printed for u's current + // physical frame. + u2 := u + remaining, _ := traceback2(&u, showRuntime, maxInt, 0) + elide := remaining - lastN - tracebackOuterFrames + if elide > 0 { + print("...", elide, " frames elided...\n") + traceback2(&u2, showRuntime, lastN+elide, tracebackOuterFrames) + } else if elide <= 0 { + // There are tracebackOuterFrames or fewer frames left to print. + // Just print the rest of the stack. + traceback2(&u2, showRuntime, lastN, tracebackOuterFrames) + } + return n + } + // By default, omits runtime frames. If that means we print nothing at all, + // repeat forcing all frames printed. + if tracebackWithRuntime(false) == 0 { + tracebackWithRuntime(true) + } + printcreatedby(gp) + + if gp.ancestors == nil { + return + } + for _, ancestor := range *gp.ancestors { + printAncestorTraceback(ancestor) + } +} + +// traceback2 prints a stack trace starting at u. It skips the first "skip" +// logical frames, after which it prints at most "max" logical frames. It +// returns n, which is the number of logical frames skipped and printed, and +// lastN, which is the number of logical frames skipped or printed just in the +// physical frame that u references. +func traceback2(u *unwinder, showRuntime bool, skip, max int) (n, lastN int) { + // commitFrame commits to a logical frame and returns whether this frame + // should be printed and whether iteration should stop. + commitFrame := func() (pr, stop bool) { + if skip == 0 && max == 0 { + // Stop + return false, true + } + n++ + lastN++ + if skip > 0 { + // Skip + skip-- + return false, false + } + // Print + max-- + return true, false + } + + gp := u.g.ptr() + level, _, _ := gotraceback() + var cgoBuf [32]uintptr + for ; u.valid(); u.next() { + lastN = 0 + f := u.frame.fn + for iu, uf := newInlineUnwinder(f, u.symPC()); uf.valid(); uf = iu.next(uf) { + sf := iu.srcFunc(uf) + callee := u.calleeFuncID + u.calleeFuncID = sf.funcID + if !(showRuntime || showframe(sf, gp, n == 0, callee)) { + continue + } + + if pr, stop := commitFrame(); stop { + return + } else if !pr { + continue + } + + name := sf.name() + file, line := iu.fileLine(uf) + // Print during crash. + // main(0x1, 0x2, 0x3) + // /home/rsc/go/src/runtime/x.go:23 +0xf + // + printFuncName(name) + print("(") + if iu.isInlined(uf) { + print("...") + } else { + argp := unsafe.Pointer(u.frame.argp) + printArgs(f, argp, u.symPC()) + } + print(")\n") + print("\t", file, ":", line) + if !iu.isInlined(uf) { + if u.frame.pc > f.entry() { + print(" +", hex(u.frame.pc-f.entry())) + } + if gp.m != nil && gp.m.throwing >= throwTypeRuntime && gp == gp.m.curg || level >= 2 { + print(" fp=", hex(u.frame.fp), " sp=", hex(u.frame.sp), " pc=", hex(u.frame.pc)) + } + } + print("\n") + } + + // Print cgo frames. + if cgoN := u.cgoCallers(cgoBuf[:]); cgoN > 0 { + var arg cgoSymbolizerArg + anySymbolized := false + stop := false + for _, pc := range cgoBuf[:cgoN] { + if cgoSymbolizer == nil { + if pr, stop := commitFrame(); stop { + break + } else if pr { + print("non-Go function at pc=", hex(pc), "\n") + } + } else { + stop = printOneCgoTraceback(pc, commitFrame, &arg) + anySymbolized = true + if stop { + break + } + } + } + if anySymbolized { + // Free symbolization state. + arg.pc = 0 + callCgoSymbolizer(&arg) + } + if stop { + return + } + } + } + return n, 0 +} + +// 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.srcFunc(), fidx == 0, abi.FuncIDNormal) { + printAncestorTracebackFuncInfo(f, pc) + } + } + if len(ancestor.pcs) == tracebackInnerFrames { + print("...additional frames elided...\n") + } + // Show what created goroutine, except main goroutine (goid 1). + f := findfunc(ancestor.gopc) + if f.valid() && showfuncinfo(f.srcFunc(), false, abi.FuncIDNormal) && ancestor.goid != 1 { + // In ancestor mode, we'll already print the goroutine ancestor. + // Pass 0 for the goid parameter so we don't print it again. + printcreatedby1(f, ancestor.gopc, 0) + } +} + +// printAncestorTracebackFuncInfo 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) { + u, uf := newInlineUnwinder(f, pc) + file, line := u.fileLine(uf) + printFuncName(u.srcFunc(uf).name()) + print("(...)\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() { + var u unwinder + u.initAt(pc, sp, 0, gp, unwindSilentErrors) + n = tracebackPCs(&u, skip, pcbuf) + }) + return n +} + +func gcallers(gp *g, skip int, pcbuf []uintptr) int { + var u unwinder + u.init(gp, unwindSilentErrors) + return tracebackPCs(&u, skip, pcbuf) +} + +// showframe reports whether the frame with the given characteristics should +// be printed during a traceback. +func showframe(sf srcFunc, gp *g, firstFrame bool, calleeID abi.FuncID) bool { + mp := getg().m + if mp.throwing >= throwTypeRuntime && gp != nil && (gp == mp.curg || gp == mp.caughtsig.ptr()) { + return true + } + return showfuncinfo(sf, firstFrame, calleeID) +} + +// showfuncinfo reports whether a function with the given characteristics should +// be printed during a traceback. +func showfuncinfo(sf srcFunc, firstFrame bool, calleeID abi.FuncID) bool { + level, _, _ := gotraceback() + if level > 1 { + // Show all frames. + return true + } + + if sf.funcID == abi.FuncIDWrapper && elideWrapperCalling(calleeID) { + return false + } + + name := sf.name() + + // 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. +// TODO: this handles exported functions but not exported methods. +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 abi.FuncID) bool { + // If the wrapper called a panic function instead of the + // wrapped function, we want to include it in stacks. + return !(id == abi.FuncID_gopanic || id == abi.FuncID_sigpanic || id == abi.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) { + level, _, _ := gotraceback() + + 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) + if gp.m != nil && gp.m.throwing >= throwTypeRuntime && gp == gp.m.curg || level >= 2 { + print(" gp=", gp) + if gp.m != nil { + print(" m=", gp.m.id, " mp=", gp.m) + } else { + print(" m=nil") + } + } + print(" [", 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 call locking forEachG here because this may be during fatal + // throw/panic, where locking could be out-of-order or a direct + // deadlock. + // + // Instead, use forEachGRace, 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. + forEachGRace(func(gp *g) { + if gp == me || gp == curgp || readgstatus(gp) == _Gdead || isSystemGoroutine(gp, false) && level < 2 { + return + } + print("\n") + goroutineheader(gp) + // Note: gp.m == getg().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 * goarch.PtrSize + const maxExpand = 256 * goarch.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 + }) +} + +// 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 internal/trace.IsSystemGoroutine. + f := findfunc(gp.startpc) + if !f.valid() { + return false + } + if f.funcID == abi.FuncID_runtime_main || f.funcID == abi.FuncID_corostart || f.funcID == abi.FuncID_handleAsyncEvent { + return false + } + if f.funcID == abi.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 fingStatus.Load()&fingRunningFinalizer == 0 + } + 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, +// linux/arm64, 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 +} + +// printCgoTraceback 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 + } + + commitFrame := func() (pr, stop bool) { return true, false } + var arg cgoSymbolizerArg + for _, c := range callers { + if c == 0 { + break + } + printOneCgoTraceback(c, commitFrame, &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. +// It returns the "stop" result of commitFrame. +func printOneCgoTraceback(pc uintptr, commitFrame func() (pr, stop bool), arg *cgoSymbolizerArg) bool { + arg.pc = pc + for { + if pr, stop := commitFrame(); stop { + return true + } else if !pr { + continue + } + + 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") + if arg.more == 0 { + return false + } + } +} + +// callCgoSymbolizer calls the cgoSymbolizer function. +func callCgoSymbolizer(arg *cgoSymbolizerArg) { + call := cgocall + if panicking.Load() > 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{})) + } + if asanenabled { + asanwrite(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.Load() > 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)) + } + if asanenabled { + asanwrite(unsafe.Pointer(&arg), unsafe.Sizeof(arg)) + } + call(cgoTraceback, noescape(unsafe.Pointer(&arg))) +} |