// 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)))
}
 |
The pages are generated with Golds v0.4.2. (GOOS=darwin GOARCH=amd64)
Golds is a Go 101 project developed by Tapir Liu.
PR and bug reports are welcome and can be submitted to the issue list.
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