Adding upstream version 1.20.14.upstream/1.20.14upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1377 insertions, 0 deletions

diff --git a/src/runtime/traceback.go b/src/runtime/traceback.go
new file mode 100644
index 0000000..37f35d5
--- /dev/null
+++ b/src/runtime/traceback.go
@@ -0,0 +1,1377 @@
+// 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"
+	"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
+
+// 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).
+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()
+
+	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
+			}
+		}
+	}
+
+	nprint := 0
+	var frame stkframe
+	frame.pc = pc0
+	frame.sp = sp0
+	if usesLR {
+		frame.lr = lr0
+	}
+	waspanic := false
+	cgoCtxt := gp.cgoCtxt
+	stack := gp.stack
+	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(*(*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 callback != nil || printing {
+			print("runtime: g ", gp.goid, ": unknown pc ", hex(frame.pc), "\n")
+			tracebackHexdump(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
+		}
+
+		// Compute function info flags.
+		flag := f.flag
+		if f.funcID == 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 &^= funcFlag_SPWRITE
+		}
+		if frame.pc == pc0 && frame.sp == sp0 && pc0 == gp.syscallpc && sp0 == gp.syscallsp {
+			// 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 &^= funcFlag_SPWRITE
+		}
+
+		// 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.
+			// 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 flags&_TraceJumpStack != 0 && gp == gp.m.g0 && gp.m.curg != nil && gp.m.curg.m == gp.m {
+				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.
+					gp = gp.m.curg
+					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
+					stack = gp.stack
+					cgoCtxt = gp.cgoCtxt
+				case funcID_systemstack:
+					// systemstack returns normally, so just follow the
+					// stack transition.
+					if usesLR && funcspdelta(f, frame.pc, &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 &^= funcFlag_SPWRITE
+						break
+					}
+					gp = gp.m.curg
+					frame.sp = gp.sched.sp
+					stack = gp.stack
+					cgoCtxt = gp.cgoCtxt
+					flag &^= funcFlag_SPWRITE
+				}
+			}
+			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 += goarch.PtrSize
+			}
+		}
+		var flr funcInfo
+		if flag&funcFlag_TOPFRAME != 0 {
+			// This function marks the top of the stack. Stop the traceback.
+			frame.lr = 0
+			flr = funcInfo{}
+		} else if flag&funcFlag_SPWRITE != 0 && (callback == nil || n > 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. Since we can't reliably unwind
+			// the SP (we might not even be on the stack we think we are),
+			// we stop the traceback here.
+			// This only applies for profiling signals (callback == nil).
+			//
+			// For a GC stack traversal (callback != nil), we should only see
+			// a 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 leave things alone (this if body does not execute for n == 0)
+			// at the bottom frame of the stack. But farther up the stack we'd better not
+			// find any.
+			if callback != nil {
+				println("traceback: unexpected SPWRITE function", funcname(f))
+				throw("traceback")
+			}
+			frame.lr = 0
+			flr = funcInfo{}
+		} 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 - goarch.PtrSize
+					frame.lr = uintptr(*(*uintptr)(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: g ", gp.goid, ": unexpected return pc for ", funcname(f), " called from ", hex(frame.lr), "\n")
+					tracebackHexdump(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 -= 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 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].nameOff
+					inlFunc.funcID = inltree[ix].funcID
+					inlFunc.startLine = inltree[ix].startLine
+
+					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 := unsafe.Pointer(frame.argp)
+				printArgs(f, argp, tracepc)
+				print(")\n")
+				print("\t", file, ":", line)
+				if frame.pc > f.entry() {
+					print(" +", hex(frame.pc-f.entry()))
+				}
+				if gp.m != nil && gp.m.throwing >= throwTypeRuntime && 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 || f.funcID == funcID_debugCallV2
+
+		// Do not unwind past the bottom of the stack.
+		if !flr.valid() {
+			break
+		}
+
+		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(stack, &frame, frame.sp)
+			throw("traceback stuck")
+		}
+
+		// 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.
+		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, &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
+}
+
+// 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, _FUNCDATA_ArgInfo))
+	if p == nil {
+		return
+	}
+
+	liveInfo := funcdata(f, _FUNCDATA_ArgLiveInfo)
+	liveIdx := pcdatavalue(f, _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
+	}
+}
+
+// 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.
+		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 &^= _TraceTrap
+	}
+	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 &^= _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)
+	}
+}
+
+// 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) {
+	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].nameOff)
+		}
+	}
+	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 {
+	mp := getg().m
+	if mp.throwing >= throwTypeRuntime && gp != nil && (gp == mp.curg || gp == mp.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 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 == 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 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
+	}
+
+	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.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)))
+}