blob: 86df1155b5c114bdcf3588039b1109e675b1d07b [file] [log] [blame]
// 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
// cache is used to cache pcvalue lookups.
cache pcvalueCache
}
// 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(*(*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, ": 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, &u.cache) == 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, &u.cache))
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 {
// 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.
if u.flags&(unwindPrintErrors|unwindSilentErrors) != 0 {
// We can't reliably unwind the SP (we might
// not even be on the stack we think we are),
// so stop the traceback here.
frame.lr = 0
} else {
// For a GC stack traversal, we should only see
// an SPWRITE function when it has 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.
if !innermost {
println("traceback: unexpected SPWRITE function", funcname(f))
throw("traceback")
}
}
} 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, &u.cache) == 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(), noEscapePtr(&u.cache)); 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, nil)
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(), noEscapePtr(&u.cache)); 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, nil)
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) {
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 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_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)))
}