runtime: convert traceback*.c to Go
The two converted files were nearly identical.
Instead of continuing that duplication, I merged them
into a single traceback.go.
Tested on arm, amd64, amd64p32, and 386.
LGTM=r
R=golang-codereviews, remyoudompheng, dave, r
CC=dvyukov, golang-codereviews, iant, khr
https://golang.org/cl/134200044
diff --git a/src/pkg/runtime/traceback.go b/src/pkg/runtime/traceback.go
new file mode 100644
index 0000000..c6a6c05
--- /dev/null
+++ b/src/pkg/runtime/traceback.go
@@ -0,0 +1,504 @@
+// 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 "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 has ptrSize == 4 but the CALL instruction still
+// stores an 8-byte return PC onto the stack. To accommodate this, we use regSize
+// as the size of the architecture-pushed return PC.
+//
+// usesLR is defined below. ptrSize and regSize are defined in stubs.go.
+
+const usesLR = GOARCH != "amd64" && GOARCH != "amd64p32" && GOARCH != "386"
+
+// jmpdeferPC is the PC at the beginning of the jmpdefer assembly function.
+// The traceback needs to recognize it on link register architectures.
+var jmpdeferPC uintptr
+
+func init() {
+ f := jmpdefer
+ jmpdeferPC = **(**uintptr)(unsafe.Pointer(&f))
+}
+
+// System-specific hook. See traceback_windows.go
+var systraceback func(*_func, *stkframe, *g, bool, func(*stkframe, unsafe.Pointer) bool, unsafe.Pointer) (changed, aborted bool)
+
+// 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.
+func gentraceback(pc0 uintptr, sp0 uintptr, lr0 uintptr, gp *g, skip int, pcbuf *uintptr, max int, callback func(*stkframe, unsafe.Pointer) bool, v unsafe.Pointer, printall bool) int {
+ g := getg()
+ gotraceback := gotraceback(nil)
+ if pc0 == ^uintptr(0) && sp0 == ^uintptr(0) { // Signal to fetch saved values from gp.
+ if gp.syscallstack != 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
+ }
+ }
+ }
+
+ nprint := 0
+ var frame stkframe
+ frame.pc = pc0
+ frame.sp = sp0
+ if usesLR {
+ frame.lr = lr0
+ }
+ waspanic := false
+ wasnewproc := false
+ printing := pcbuf == nil && callback == nil
+ panic := gp._panic
+ _defer := gp._defer
+
+ for _defer != nil && uintptr(_defer.argp) == _NoArgs {
+ _defer = _defer.link
+ }
+ for panic != nil && panic._defer == nil {
+ panic = panic.link
+ }
+
+ // 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(*(*uintreg)(unsafe.Pointer(frame.sp)))
+ frame.sp += regSize
+ }
+ }
+
+ f := findfunc(frame.pc)
+ if f == nil {
+ if callback != nil {
+ print("runtime: unknown pc ", hex(frame.pc), "\n")
+ gothrow("unknown pc")
+ }
+ return 0
+ }
+ frame.fn = f
+
+ n := 0
+ stk := (*stktop)(unsafe.Pointer(gp.stackbase))
+ 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.
+ if frame.pc == uintptr(unsafe.Pointer(&lessstack)) {
+ // Hit top of stack segment. Unwind to next segment.
+ frame.pc = stk.gobuf.pc
+ frame.sp = stk.gobuf.sp
+ frame.lr = 0
+ frame.fp = 0
+ if printing && showframe(nil, gp) {
+ print("----- stack segment boundary -----\n")
+ }
+ stk = (*stktop)(unsafe.Pointer(stk.stackbase))
+ f = findfunc(frame.pc)
+ if f == nil {
+ print("runtime: unknown pc ", hex(frame.pc), " after stack split\n")
+ if callback != nil {
+ gothrow("unknown pc")
+ }
+ }
+ frame.fn = f
+ continue
+ }
+ f = frame.fn
+
+ // Hook for handling Windows exception handlers. See traceback_windows.go.
+ if systraceback != nil {
+ changed, aborted := systraceback(f, (*stkframe)(noescape(unsafe.Pointer(&frame))), gp, printing, callback, v)
+ if aborted {
+ return n
+ }
+ if changed {
+ continue
+ }
+ }
+
+ // Found an actual function.
+ // Derive frame pointer and link register.
+ if frame.fp == 0 {
+ frame.fp = frame.sp + uintptr(funcspdelta(f, frame.pc))
+ if !usesLR {
+ // On x86, call instruction pushes return PC before entering new function.
+ frame.fp += regSize
+ }
+ }
+ var flr *_func
+ if topofstack(f) {
+ frame.lr = 0
+ flr = nil
+ } else if usesLR && f.entry == jmpdeferPC {
+ // 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 {
+ gothrow("traceback_arm: found jmpdefer when tracing with callback")
+ }
+ frame.lr = 0
+ } else {
+ if usesLR {
+ if n == 0 && frame.sp < frame.fp || frame.lr == 0 {
+ frame.lr = *(*uintptr)(unsafe.Pointer(frame.sp))
+ }
+ } else {
+ if frame.lr == 0 {
+ frame.lr = uintptr(*(*uintreg)(unsafe.Pointer(frame.fp - regSize)))
+ }
+ }
+ flr = findfunc(frame.lr)
+ if flr == nil {
+ // 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.
+ if callback != nil {
+ print("runtime: unexpected return pc for ", gofuncname(f), " called from ", hex(frame.lr), "\n")
+ gothrow("unknown caller pc")
+ }
+ }
+ }
+
+ frame.varp = frame.fp
+ if !usesLR {
+ // On x86, call instruction pushes return PC before entering new function.
+ frame.varp -= 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
+ if usesLR {
+ frame.argp += ptrSize
+ }
+ if f.args != _ArgsSizeUnknown {
+ frame.arglen = uintptr(f.args)
+ } else if flr == nil {
+ frame.arglen = 0
+ } else if frame.lr == uintptr(unsafe.Pointer(&lessstack)) {
+ frame.arglen = uintptr(stk.argsize)
+ } else {
+ i := funcarglen(flr, frame.lr)
+ if i >= 0 {
+ frame.arglen = uintptr(i)
+ } else {
+ var tmp string
+ if flr != nil {
+ tmp = gofuncname(flr)
+ } else {
+ tmp = "?"
+ }
+ print("runtime: unknown argument frame size for ", gofuncname(f), " called from ", hex(frame.lr), " [", tmp, "]\n")
+ if callback != nil {
+ gothrow("invalid stack")
+ }
+ frame.arglen = 0
+ }
+ }
+ }
+
+ // Determine function SP where deferproc would find its arguments.
+ var sparg uintptr
+ if usesLR {
+ // On link register architectures, that's the standard bottom-of-stack plus 1 word
+ // for the saved LR. If the previous frame was a direct call to newproc/deferproc,
+ // however, the SP is three words lower than normal.
+ // If the function has no frame at all - perhaps it just started, or perhaps
+ // it is a leaf with no local variables - then we cannot possibly find its
+ // SP in a defer, and we might confuse its SP for its caller's SP, so
+ // leave sparg=0 in that case.
+ if frame.fp != frame.sp {
+ sparg = frame.sp + regSize
+ if wasnewproc {
+ sparg += 3 * regSize
+ }
+ }
+ } else {
+ // On x86 that's the standard bottom-of-stack, so SP exactly.
+ // If the previous frame was a direct call to newproc/deferproc, however,
+ // the SP is two words lower than normal.
+ sparg = frame.sp
+ if wasnewproc {
+ sparg += 2 * ptrSize
+ }
+ }
+
+ // 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).
+ // It suffices to assume that the most recent deferproc is the one that
+ // returns; everything live at earlier deferprocs is still live at that one.
+ frame.continpc = frame.pc
+ if waspanic {
+ if panic != nil && panic._defer.argp == sparg {
+ frame.continpc = panic._defer.pc
+ } else if _defer != nil && _defer.argp == sparg {
+ frame.continpc = _defer.pc
+ } else {
+ frame.continpc = 0
+ }
+ }
+
+ // Unwind our local panic & defer stacks past this frame.
+ for panic != nil && (panic._defer == nil || panic._defer.argp == sparg || panic._defer.argp == _NoArgs) {
+ panic = panic.link
+ }
+ for _defer != nil && (_defer.argp == sparg || _defer.argp == _NoArgs) {
+ _defer = _defer.link
+ }
+
+ if skip > 0 {
+ skip--
+ goto skipped
+ }
+
+ if pcbuf != nil {
+ (*[1 << 20]uintptr)(unsafe.Pointer(pcbuf))[n] = frame.pc
+ }
+ if callback != nil {
+ if !callback((*stkframe)(noescape(unsafe.Pointer(&frame))), v) {
+ return n
+ }
+ }
+ if printing {
+ if printall || showframe(f, gp) {
+ // Print during crash.
+ // main(0x1, 0x2, 0x3)
+ // /home/rsc/go/src/runtime/x.go:23 +0xf
+ //
+ tracepc := frame.pc // back up to CALL instruction for funcline.
+ if n > 0 && frame.pc > f.entry && !waspanic {
+ tracepc--
+ }
+ print(gofuncname(f), "(")
+ argp := (*[100]uintptr)(unsafe.Pointer(frame.argp))
+ for i := uintptr(0); i < frame.arglen/ptrSize; i++ {
+ if i >= 10 {
+ print(", ...")
+ break
+ }
+ if i != 0 {
+ print(", ")
+ }
+ print(hex(argp[i]))
+ }
+ print(")\n")
+ var file string
+ line := funcline(f, tracepc, &file)
+ print("\t", file, ":", line)
+ if frame.pc > f.entry {
+ print(" +", hex(frame.pc-f.entry))
+ }
+ if g.m.throwing > 0 && gp == g.m.curg || gotraceback >= 2 {
+ print(" fp=", hex(frame.fp), " sp=", hex(frame.sp))
+ }
+ print("\n")
+ nprint++
+ }
+ }
+ n++
+
+ skipped:
+ waspanic = f.entry == uintptr(unsafe.Pointer(&sigpanic))
+ wasnewproc = f.entry == uintptr(unsafe.Pointer(&newproc)) || f.entry == uintptr(unsafe.Pointer(&deferproc))
+
+ // Do not unwind past the bottom of the stack.
+ if flr == nil {
+ break
+ }
+
+ // Unwind to next frame.
+ 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 to sigpanic.
+ if usesLR && waspanic {
+ x := *(*uintptr)(unsafe.Pointer(frame.sp))
+ frame.sp += ptrSize
+ f = findfunc(frame.pc)
+ frame.fn = f
+ if f == nil {
+ frame.pc = x
+ } else if f.frame == 0 {
+ frame.lr = x
+ }
+ }
+ }
+
+ if pcbuf == nil && callback == nil {
+ n = nprint
+ }
+
+ // If callback != nil, we're being called to gather stack information during
+ // garbage collection or stack growth. In that context, require that we used
+ // up the entire defer stack. If not, then there is a bug somewhere and the
+ // garbage collection or stack growth may not have seen the correct picture
+ // of the stack. Crash now instead of silently executing the garbage collection
+ // or stack copy incorrectly and setting up for a mysterious crash later.
+ //
+ // 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.
+ // It's okay in those situations not to use up the entire defer stack:
+ // incomplete information then is still better than nothing.
+ if callback != nil && n < max && _defer != nil {
+ if _defer != nil {
+ print("runtime: g", gp.goid, ": leftover defer argp=", hex(_defer.argp), " pc=", hex(_defer.pc), "\n")
+ }
+ if panic != nil {
+ print("runtime: g", gp.goid, ": leftover panic argp=", hex(panic._defer.argp), " pc=", hex(panic._defer.pc), "\n")
+ }
+ for _defer = gp._defer; _defer != nil; _defer = _defer.link {
+ print("\tdefer ", _defer, " argp=", hex(_defer.argp), " pc=", hex(_defer.pc), "\n")
+ }
+ for panic = gp._panic; panic != nil; panic = panic.link {
+ print("\tpanic ", panic, " defer ", panic._defer)
+ if panic._defer != nil {
+ print(" argp=", hex(panic._defer.argp), " pc=", hex(panic._defer.pc))
+ }
+ print("\n")
+ }
+ gothrow("traceback has leftover defers or panics")
+ }
+
+ return n
+}
+
+func showframe(*_func, *g) bool
+
+func printcreatedby(gp *g) {
+ // Show what created goroutine, except main goroutine (goid 1).
+ pc := gp.gopc
+ f := findfunc(pc)
+ if f != nil && showframe(f, gp) && gp.goid != 1 {
+ print("created by ", gofuncname(f), "\n")
+ tracepc := pc // back up to CALL instruction for funcline.
+ if pc > f.entry {
+ tracepc -= _PCQuantum
+ }
+ var file string
+ line := funcline(f, tracepc, &file)
+ print("\t", file, ":", line)
+ if pc > f.entry {
+ print(" +", hex(pc-f.entry))
+ }
+ print("\n")
+ }
+}
+
+func traceback(pc uintptr, sp uintptr, lr uintptr, gp *g) {
+ var n int
+ if readgstatus(gp)&^_Gscan == _Gsyscall {
+ // Override signal registers if blocked in system call.
+ pc = gp.syscallpc
+ sp = gp.syscallsp
+ }
+ // Print traceback. By default, omits runtime frames.
+ // If that means we print nothing at all, repeat forcing all frames printed.
+ n = gentraceback(pc, sp, 0, gp, 0, nil, _TracebackMaxFrames, nil, nil, false)
+ if n == 0 {
+ n = gentraceback(pc, sp, 0, gp, 0, nil, _TracebackMaxFrames, nil, nil, true)
+ }
+ if n == _TracebackMaxFrames {
+ print("...additional frames elided...\n")
+ }
+ printcreatedby(gp)
+}
+
+func callers(skip int, pcbuf *uintptr, m int) int {
+ sp := getcallersp(unsafe.Pointer(&skip))
+ pc := uintptr(getcallerpc(unsafe.Pointer(&skip)))
+ return gentraceback(pc, sp, 0, getg(), skip, pcbuf, m, nil, nil, false)
+}
+
+func gcallers(gp *g, skip int, pcbuf *uintptr, m int) int {
+ return gentraceback(^uintptr(0), ^uintptr(0), 0, gp, skip, pcbuf, m, nil, nil, false)
+}
