Source file src/runtime/traceback.go

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package runtime
     6  
     7  import (
     8  	"internal/abi"
     9  	"internal/bytealg"
    10  	"internal/goarch"
    11  	"internal/stringslite"
    12  	"runtime/internal/sys"
    13  	"unsafe"
    14  )
    15  
    16  // The code in this file implements stack trace walking for all architectures.
    17  // The most important fact about a given architecture is whether it uses a link register.
    18  // On systems with link registers, the prologue for a non-leaf function stores the
    19  // incoming value of LR at the bottom of the newly allocated stack frame.
    20  // On systems without link registers (x86), the architecture pushes a return PC during
    21  // the call instruction, so the return PC ends up above the stack frame.
    22  // In this file, the return PC is always called LR, no matter how it was found.
    23  
    24  const usesLR = sys.MinFrameSize > 0
    25  
    26  const (
    27  	// tracebackInnerFrames is the number of innermost frames to print in a
    28  	// stack trace. The total maximum frames is tracebackInnerFrames +
    29  	// tracebackOuterFrames.
    30  	tracebackInnerFrames = 50
    31  
    32  	// tracebackOuterFrames is the number of outermost frames to print in a
    33  	// stack trace.
    34  	tracebackOuterFrames = 50
    35  )
    36  
    37  // unwindFlags control the behavior of various unwinders.
    38  type unwindFlags uint8
    39  
    40  const (
    41  	// unwindPrintErrors indicates that if unwinding encounters an error, it
    42  	// should print a message and stop without throwing. This is used for things
    43  	// like stack printing, where it's better to get incomplete information than
    44  	// to crash. This is also used in situations where everything may not be
    45  	// stopped nicely and the stack walk may not be able to complete, such as
    46  	// during profiling signals or during a crash.
    47  	//
    48  	// If neither unwindPrintErrors or unwindSilentErrors are set, unwinding
    49  	// performs extra consistency checks and throws on any error.
    50  	//
    51  	// Note that there are a small number of fatal situations that will throw
    52  	// regardless of unwindPrintErrors or unwindSilentErrors.
    53  	unwindPrintErrors unwindFlags = 1 << iota
    54  
    55  	// unwindSilentErrors silently ignores errors during unwinding.
    56  	unwindSilentErrors
    57  
    58  	// unwindTrap indicates that the initial PC and SP are from a trap, not a
    59  	// return PC from a call.
    60  	//
    61  	// The unwindTrap flag is updated during unwinding. If set, frame.pc is the
    62  	// address of a faulting instruction instead of the return address of a
    63  	// call. It also means the liveness at pc may not be known.
    64  	//
    65  	// TODO: Distinguish frame.continpc, which is really the stack map PC, from
    66  	// the actual continuation PC, which is computed differently depending on
    67  	// this flag and a few other things.
    68  	unwindTrap
    69  
    70  	// unwindJumpStack indicates that, if the traceback is on a system stack, it
    71  	// should resume tracing at the user stack when the system stack is
    72  	// exhausted.
    73  	unwindJumpStack
    74  )
    75  
    76  // An unwinder iterates the physical stack frames of a Go sack.
    77  //
    78  // Typical use of an unwinder looks like:
    79  //
    80  //	var u unwinder
    81  //	for u.init(gp, 0); u.valid(); u.next() {
    82  //		// ... use frame info in u ...
    83  //	}
    84  //
    85  // Implementation note: This is carefully structured to be pointer-free because
    86  // tracebacks happen in places that disallow write barriers (e.g., signals).
    87  // Even if this is stack-allocated, its pointer-receiver methods don't know that
    88  // their receiver is on the stack, so they still emit write barriers. Here we
    89  // address that by carefully avoiding any pointers in this type. Another
    90  // approach would be to split this into a mutable part that's passed by pointer
    91  // but contains no pointers itself and an immutable part that's passed and
    92  // returned by value and can contain pointers. We could potentially hide that
    93  // we're doing that in trivial methods that are inlined into the caller that has
    94  // the stack allocation, but that's fragile.
    95  type unwinder struct {
    96  	// frame is the current physical stack frame, or all 0s if
    97  	// there is no frame.
    98  	frame stkframe
    99  
   100  	// g is the G who's stack is being unwound. If the
   101  	// unwindJumpStack flag is set and the unwinder jumps stacks,
   102  	// this will be different from the initial G.
   103  	g guintptr
   104  
   105  	// cgoCtxt is the index into g.cgoCtxt of the next frame on the cgo stack.
   106  	// The cgo stack is unwound in tandem with the Go stack as we find marker frames.
   107  	cgoCtxt int
   108  
   109  	// calleeFuncID is the function ID of the caller of the current
   110  	// frame.
   111  	calleeFuncID abi.FuncID
   112  
   113  	// flags are the flags to this unwind. Some of these are updated as we
   114  	// unwind (see the flags documentation).
   115  	flags unwindFlags
   116  }
   117  
   118  // init initializes u to start unwinding gp's stack and positions the
   119  // iterator on gp's innermost frame. gp must not be the current G.
   120  //
   121  // A single unwinder can be reused for multiple unwinds.
   122  func (u *unwinder) init(gp *g, flags unwindFlags) {
   123  	// Implementation note: This starts the iterator on the first frame and we
   124  	// provide a "valid" method. Alternatively, this could start in a "before
   125  	// the first frame" state and "next" could return whether it was able to
   126  	// move to the next frame, but that's both more awkward to use in a "for"
   127  	// loop and is harder to implement because we have to do things differently
   128  	// for the first frame.
   129  	u.initAt(^uintptr(0), ^uintptr(0), ^uintptr(0), gp, flags)
   130  }
   131  
   132  func (u *unwinder) initAt(pc0, sp0, lr0 uintptr, gp *g, flags unwindFlags) {
   133  	// Don't call this "g"; it's too easy get "g" and "gp" confused.
   134  	if ourg := getg(); ourg == gp && ourg == ourg.m.curg {
   135  		// The starting sp has been passed in as a uintptr, and the caller may
   136  		// have other uintptr-typed stack references as well.
   137  		// If during one of the calls that got us here or during one of the
   138  		// callbacks below the stack must be grown, all these uintptr references
   139  		// to the stack will not be updated, and traceback will continue
   140  		// to inspect the old stack memory, which may no longer be valid.
   141  		// Even if all the variables were updated correctly, it is not clear that
   142  		// we want to expose a traceback that begins on one stack and ends
   143  		// on another stack. That could confuse callers quite a bit.
   144  		// Instead, we require that initAt and any other function that
   145  		// accepts an sp for the current goroutine (typically obtained by
   146  		// calling getcallersp) must not run on that goroutine's stack but
   147  		// instead on the g0 stack.
   148  		throw("cannot trace user goroutine on its own stack")
   149  	}
   150  
   151  	if pc0 == ^uintptr(0) && sp0 == ^uintptr(0) { // Signal to fetch saved values from gp.
   152  		if gp.syscallsp != 0 {
   153  			pc0 = gp.syscallpc
   154  			sp0 = gp.syscallsp
   155  			if usesLR {
   156  				lr0 = 0
   157  			}
   158  		} else {
   159  			pc0 = gp.sched.pc
   160  			sp0 = gp.sched.sp
   161  			if usesLR {
   162  				lr0 = gp.sched.lr
   163  			}
   164  		}
   165  	}
   166  
   167  	var frame stkframe
   168  	frame.pc = pc0
   169  	frame.sp = sp0
   170  	if usesLR {
   171  		frame.lr = lr0
   172  	}
   173  
   174  	// If the PC is zero, it's likely a nil function call.
   175  	// Start in the caller's frame.
   176  	if frame.pc == 0 {
   177  		if usesLR {
   178  			frame.pc = *(*uintptr)(unsafe.Pointer(frame.sp))
   179  			frame.lr = 0
   180  		} else {
   181  			frame.pc = *(*uintptr)(unsafe.Pointer(frame.sp))
   182  			frame.sp += goarch.PtrSize
   183  		}
   184  	}
   185  
   186  	// internal/runtime/atomic functions call into kernel helpers on
   187  	// arm < 7. See internal/runtime/atomic/sys_linux_arm.s.
   188  	//
   189  	// Start in the caller's frame.
   190  	if GOARCH == "arm" && goarm < 7 && GOOS == "linux" && frame.pc&0xffff0000 == 0xffff0000 {
   191  		// Note that the calls are simple BL without pushing the return
   192  		// address, so we use LR directly.
   193  		//
   194  		// The kernel helpers are frameless leaf functions, so SP and
   195  		// LR are not touched.
   196  		frame.pc = frame.lr
   197  		frame.lr = 0
   198  	}
   199  
   200  	f := findfunc(frame.pc)
   201  	if !f.valid() {
   202  		if flags&unwindSilentErrors == 0 {
   203  			print("runtime: g ", gp.goid, " gp=", gp, ": unknown pc ", hex(frame.pc), "\n")
   204  			tracebackHexdump(gp.stack, &frame, 0)
   205  		}
   206  		if flags&(unwindPrintErrors|unwindSilentErrors) == 0 {
   207  			throw("unknown pc")
   208  		}
   209  		*u = unwinder{}
   210  		return
   211  	}
   212  	frame.fn = f
   213  
   214  	// Populate the unwinder.
   215  	*u = unwinder{
   216  		frame:        frame,
   217  		g:            gp.guintptr(),
   218  		cgoCtxt:      len(gp.cgoCtxt) - 1,
   219  		calleeFuncID: abi.FuncIDNormal,
   220  		flags:        flags,
   221  	}
   222  
   223  	isSyscall := frame.pc == pc0 && frame.sp == sp0 && pc0 == gp.syscallpc && sp0 == gp.syscallsp
   224  	u.resolveInternal(true, isSyscall)
   225  }
   226  
   227  func (u *unwinder) valid() bool {
   228  	return u.frame.pc != 0
   229  }
   230  
   231  // resolveInternal fills in u.frame based on u.frame.fn, pc, and sp.
   232  //
   233  // innermost indicates that this is the first resolve on this stack. If
   234  // innermost is set, isSyscall indicates that the PC/SP was retrieved from
   235  // gp.syscall*; this is otherwise ignored.
   236  //
   237  // On entry, u.frame contains:
   238  //   - fn is the running function.
   239  //   - pc is the PC in the running function.
   240  //   - sp is the stack pointer at that program counter.
   241  //   - For the innermost frame on LR machines, lr is the program counter that called fn.
   242  //
   243  // On return, u.frame contains:
   244  //   - fp is the stack pointer of the caller.
   245  //   - lr is the program counter that called fn.
   246  //   - varp, argp, and continpc are populated for the current frame.
   247  //
   248  // If fn is a stack-jumping function, resolveInternal can change the entire
   249  // frame state to follow that stack jump.
   250  //
   251  // This is internal to unwinder.
   252  func (u *unwinder) resolveInternal(innermost, isSyscall bool) {
   253  	frame := &u.frame
   254  	gp := u.g.ptr()
   255  
   256  	f := frame.fn
   257  	if f.pcsp == 0 {
   258  		// No frame information, must be external function, like race support.
   259  		// See golang.org/issue/13568.
   260  		u.finishInternal()
   261  		return
   262  	}
   263  
   264  	// Compute function info flags.
   265  	flag := f.flag
   266  	if f.funcID == abi.FuncID_cgocallback {
   267  		// cgocallback does write SP to switch from the g0 to the curg stack,
   268  		// but it carefully arranges that during the transition BOTH stacks
   269  		// have cgocallback frame valid for unwinding through.
   270  		// So we don't need to exclude it with the other SP-writing functions.
   271  		flag &^= abi.FuncFlagSPWrite
   272  	}
   273  	if isSyscall {
   274  		// Some Syscall functions write to SP, but they do so only after
   275  		// saving the entry PC/SP using entersyscall.
   276  		// Since we are using the entry PC/SP, the later SP write doesn't matter.
   277  		flag &^= abi.FuncFlagSPWrite
   278  	}
   279  
   280  	// Found an actual function.
   281  	// Derive frame pointer.
   282  	if frame.fp == 0 {
   283  		// Jump over system stack transitions. If we're on g0 and there's a user
   284  		// goroutine, try to jump. Otherwise this is a regular call.
   285  		// We also defensively check that this won't switch M's on us,
   286  		// which could happen at critical points in the scheduler.
   287  		// This ensures gp.m doesn't change from a stack jump.
   288  		if u.flags&unwindJumpStack != 0 && gp == gp.m.g0 && gp.m.curg != nil && gp.m.curg.m == gp.m {
   289  			switch f.funcID {
   290  			case abi.FuncID_morestack:
   291  				// morestack does not return normally -- newstack()
   292  				// gogo's to curg.sched. Match that.
   293  				// This keeps morestack() from showing up in the backtrace,
   294  				// but that makes some sense since it'll never be returned
   295  				// to.
   296  				gp = gp.m.curg
   297  				u.g.set(gp)
   298  				frame.pc = gp.sched.pc
   299  				frame.fn = findfunc(frame.pc)
   300  				f = frame.fn
   301  				flag = f.flag
   302  				frame.lr = gp.sched.lr
   303  				frame.sp = gp.sched.sp
   304  				u.cgoCtxt = len(gp.cgoCtxt) - 1
   305  			case abi.FuncID_systemstack:
   306  				// systemstack returns normally, so just follow the
   307  				// stack transition.
   308  				if usesLR && funcspdelta(f, frame.pc) == 0 {
   309  					// We're at the function prologue and the stack
   310  					// switch hasn't happened, or epilogue where we're
   311  					// about to return. Just unwind normally.
   312  					// Do this only on LR machines because on x86
   313  					// systemstack doesn't have an SP delta (the CALL
   314  					// instruction opens the frame), therefore no way
   315  					// to check.
   316  					flag &^= abi.FuncFlagSPWrite
   317  					break
   318  				}
   319  				gp = gp.m.curg
   320  				u.g.set(gp)
   321  				frame.sp = gp.sched.sp
   322  				u.cgoCtxt = len(gp.cgoCtxt) - 1
   323  				flag &^= abi.FuncFlagSPWrite
   324  			}
   325  		}
   326  		frame.fp = frame.sp + uintptr(funcspdelta(f, frame.pc))
   327  		if !usesLR {
   328  			// On x86, call instruction pushes return PC before entering new function.
   329  			frame.fp += goarch.PtrSize
   330  		}
   331  	}
   332  
   333  	// Derive link register.
   334  	if flag&abi.FuncFlagTopFrame != 0 {
   335  		// This function marks the top of the stack. Stop the traceback.
   336  		frame.lr = 0
   337  	} else if flag&abi.FuncFlagSPWrite != 0 && (!innermost || u.flags&(unwindPrintErrors|unwindSilentErrors) != 0) {
   338  		// The function we are in does a write to SP that we don't know
   339  		// how to encode in the spdelta table. Examples include context
   340  		// switch routines like runtime.gogo but also any code that switches
   341  		// to the g0 stack to run host C code.
   342  		// We can't reliably unwind the SP (we might not even be on
   343  		// the stack we think we are), so stop the traceback here.
   344  		//
   345  		// The one exception (encoded in the complex condition above) is that
   346  		// we assume if we're doing a precise traceback, and this is the
   347  		// innermost frame, that the SPWRITE function voluntarily preempted itself on entry
   348  		// during the stack growth check. In that case, the function has
   349  		// not yet had a chance to do any writes to SP and is safe to unwind.
   350  		// isAsyncSafePoint does not allow assembly functions to be async preempted,
   351  		// and preemptPark double-checks that SPWRITE functions are not async preempted.
   352  		// So for GC stack traversal, we can safely ignore SPWRITE for the innermost frame,
   353  		// but farther up the stack we'd better not find any.
   354  		// This is somewhat imprecise because we're just guessing that we're in the stack
   355  		// growth check. It would be better if SPWRITE were encoded in the spdelta
   356  		// table so we would know for sure that we were still in safe code.
   357  		//
   358  		// uSE uPE inn | action
   359  		//  T   _   _  | frame.lr = 0
   360  		//  F   T   _  | frame.lr = 0
   361  		//  F   F   F  | print; panic
   362  		//  F   F   T  | ignore SPWrite
   363  		if u.flags&(unwindPrintErrors|unwindSilentErrors) == 0 && !innermost {
   364  			println("traceback: unexpected SPWRITE function", funcname(f))
   365  			throw("traceback")
   366  		}
   367  		frame.lr = 0
   368  	} else {
   369  		var lrPtr uintptr
   370  		if usesLR {
   371  			if innermost && frame.sp < frame.fp || frame.lr == 0 {
   372  				lrPtr = frame.sp
   373  				frame.lr = *(*uintptr)(unsafe.Pointer(lrPtr))
   374  			}
   375  		} else {
   376  			if frame.lr == 0 {
   377  				lrPtr = frame.fp - goarch.PtrSize
   378  				frame.lr = *(*uintptr)(unsafe.Pointer(lrPtr))
   379  			}
   380  		}
   381  	}
   382  
   383  	frame.varp = frame.fp
   384  	if !usesLR {
   385  		// On x86, call instruction pushes return PC before entering new function.
   386  		frame.varp -= goarch.PtrSize
   387  	}
   388  
   389  	// For architectures with frame pointers, if there's
   390  	// a frame, then there's a saved frame pointer here.
   391  	//
   392  	// NOTE: This code is not as general as it looks.
   393  	// On x86, the ABI is to save the frame pointer word at the
   394  	// top of the stack frame, so we have to back down over it.
   395  	// On arm64, the frame pointer should be at the bottom of
   396  	// the stack (with R29 (aka FP) = RSP), in which case we would
   397  	// not want to do the subtraction here. But we started out without
   398  	// any frame pointer, and when we wanted to add it, we didn't
   399  	// want to break all the assembly doing direct writes to 8(RSP)
   400  	// to set the first parameter to a called function.
   401  	// So we decided to write the FP link *below* the stack pointer
   402  	// (with R29 = RSP - 8 in Go functions).
   403  	// This is technically ABI-compatible but not standard.
   404  	// And it happens to end up mimicking the x86 layout.
   405  	// Other architectures may make different decisions.
   406  	if frame.varp > frame.sp && framepointer_enabled {
   407  		frame.varp -= goarch.PtrSize
   408  	}
   409  
   410  	frame.argp = frame.fp + sys.MinFrameSize
   411  
   412  	// Determine frame's 'continuation PC', where it can continue.
   413  	// Normally this is the return address on the stack, but if sigpanic
   414  	// is immediately below this function on the stack, then the frame
   415  	// stopped executing due to a trap, and frame.pc is probably not
   416  	// a safe point for looking up liveness information. In this panicking case,
   417  	// the function either doesn't return at all (if it has no defers or if the
   418  	// defers do not recover) or it returns from one of the calls to
   419  	// deferproc a second time (if the corresponding deferred func recovers).
   420  	// In the latter case, use a deferreturn call site as the continuation pc.
   421  	frame.continpc = frame.pc
   422  	if u.calleeFuncID == abi.FuncID_sigpanic {
   423  		if frame.fn.deferreturn != 0 {
   424  			frame.continpc = frame.fn.entry() + uintptr(frame.fn.deferreturn) + 1
   425  			// Note: this may perhaps keep return variables alive longer than
   426  			// strictly necessary, as we are using "function has a defer statement"
   427  			// as a proxy for "function actually deferred something". It seems
   428  			// to be a minor drawback. (We used to actually look through the
   429  			// gp._defer for a defer corresponding to this function, but that
   430  			// is hard to do with defer records on the stack during a stack copy.)
   431  			// Note: the +1 is to offset the -1 that
   432  			// stack.go:getStackMap does to back up a return
   433  			// address make sure the pc is in the CALL instruction.
   434  		} else {
   435  			frame.continpc = 0
   436  		}
   437  	}
   438  }
   439  
   440  func (u *unwinder) next() {
   441  	frame := &u.frame
   442  	f := frame.fn
   443  	gp := u.g.ptr()
   444  
   445  	// Do not unwind past the bottom of the stack.
   446  	if frame.lr == 0 {
   447  		u.finishInternal()
   448  		return
   449  	}
   450  	flr := findfunc(frame.lr)
   451  	if !flr.valid() {
   452  		// This happens if you get a profiling interrupt at just the wrong time.
   453  		// In that context it is okay to stop early.
   454  		// But if no error flags are set, we're doing a garbage collection and must
   455  		// get everything, so crash loudly.
   456  		fail := u.flags&(unwindPrintErrors|unwindSilentErrors) == 0
   457  		doPrint := u.flags&unwindSilentErrors == 0
   458  		if doPrint && gp.m.incgo && f.funcID == abi.FuncID_sigpanic {
   459  			// We can inject sigpanic
   460  			// calls directly into C code,
   461  			// in which case we'll see a C
   462  			// return PC. Don't complain.
   463  			doPrint = false
   464  		}
   465  		if fail || doPrint {
   466  			print("runtime: g ", gp.goid, ": unexpected return pc for ", funcname(f), " called from ", hex(frame.lr), "\n")
   467  			tracebackHexdump(gp.stack, frame, 0)
   468  		}
   469  		if fail {
   470  			throw("unknown caller pc")
   471  		}
   472  		frame.lr = 0
   473  		u.finishInternal()
   474  		return
   475  	}
   476  
   477  	if frame.pc == frame.lr && frame.sp == frame.fp {
   478  		// If the next frame is identical to the current frame, we cannot make progress.
   479  		print("runtime: traceback stuck. pc=", hex(frame.pc), " sp=", hex(frame.sp), "\n")
   480  		tracebackHexdump(gp.stack, frame, frame.sp)
   481  		throw("traceback stuck")
   482  	}
   483  
   484  	injectedCall := f.funcID == abi.FuncID_sigpanic || f.funcID == abi.FuncID_asyncPreempt || f.funcID == abi.FuncID_debugCallV2
   485  	if injectedCall {
   486  		u.flags |= unwindTrap
   487  	} else {
   488  		u.flags &^= unwindTrap
   489  	}
   490  
   491  	// Unwind to next frame.
   492  	u.calleeFuncID = f.funcID
   493  	frame.fn = flr
   494  	frame.pc = frame.lr
   495  	frame.lr = 0
   496  	frame.sp = frame.fp
   497  	frame.fp = 0
   498  
   499  	// On link register architectures, sighandler saves the LR on stack
   500  	// before faking a call.
   501  	if usesLR && injectedCall {
   502  		x := *(*uintptr)(unsafe.Pointer(frame.sp))
   503  		frame.sp += alignUp(sys.MinFrameSize, sys.StackAlign)
   504  		f = findfunc(frame.pc)
   505  		frame.fn = f
   506  		if !f.valid() {
   507  			frame.pc = x
   508  		} else if funcspdelta(f, frame.pc) == 0 {
   509  			frame.lr = x
   510  		}
   511  	}
   512  
   513  	u.resolveInternal(false, false)
   514  }
   515  
   516  // finishInternal is an unwinder-internal helper called after the stack has been
   517  // exhausted. It sets the unwinder to an invalid state and checks that it
   518  // successfully unwound the entire stack.
   519  func (u *unwinder) finishInternal() {
   520  	u.frame.pc = 0
   521  
   522  	// Note that panic != nil is okay here: there can be leftover panics,
   523  	// because the defers on the panic stack do not nest in frame order as
   524  	// they do on the defer stack. If you have:
   525  	//
   526  	//	frame 1 defers d1
   527  	//	frame 2 defers d2
   528  	//	frame 3 defers d3
   529  	//	frame 4 panics
   530  	//	frame 4's panic starts running defers
   531  	//	frame 5, running d3, defers d4
   532  	//	frame 5 panics
   533  	//	frame 5's panic starts running defers
   534  	//	frame 6, running d4, garbage collects
   535  	//	frame 6, running d2, garbage collects
   536  	//
   537  	// During the execution of d4, the panic stack is d4 -> d3, which
   538  	// is nested properly, and we'll treat frame 3 as resumable, because we
   539  	// can find d3. (And in fact frame 3 is resumable. If d4 recovers
   540  	// and frame 5 continues running, d3, d3 can recover and we'll
   541  	// resume execution in (returning from) frame 3.)
   542  	//
   543  	// During the execution of d2, however, the panic stack is d2 -> d3,
   544  	// which is inverted. The scan will match d2 to frame 2 but having
   545  	// d2 on the stack until then means it will not match d3 to frame 3.
   546  	// This is okay: if we're running d2, then all the defers after d2 have
   547  	// completed and their corresponding frames are dead. Not finding d3
   548  	// for frame 3 means we'll set frame 3's continpc == 0, which is correct
   549  	// (frame 3 is dead). At the end of the walk the panic stack can thus
   550  	// contain defers (d3 in this case) for dead frames. The inversion here
   551  	// always indicates a dead frame, and the effect of the inversion on the
   552  	// scan is to hide those dead frames, so the scan is still okay:
   553  	// what's left on the panic stack are exactly (and only) the dead frames.
   554  	//
   555  	// We require callback != nil here because only when callback != nil
   556  	// do we know that gentraceback is being called in a "must be correct"
   557  	// context as opposed to a "best effort" context. The tracebacks with
   558  	// callbacks only happen when everything is stopped nicely.
   559  	// At other times, such as when gathering a stack for a profiling signal
   560  	// or when printing a traceback during a crash, everything may not be
   561  	// stopped nicely, and the stack walk may not be able to complete.
   562  	gp := u.g.ptr()
   563  	if u.flags&(unwindPrintErrors|unwindSilentErrors) == 0 && u.frame.sp != gp.stktopsp {
   564  		print("runtime: g", gp.goid, ": frame.sp=", hex(u.frame.sp), " top=", hex(gp.stktopsp), "\n")
   565  		print("\tstack=[", hex(gp.stack.lo), "-", hex(gp.stack.hi), "\n")
   566  		throw("traceback did not unwind completely")
   567  	}
   568  }
   569  
   570  // symPC returns the PC that should be used for symbolizing the current frame.
   571  // Specifically, this is the PC of the last instruction executed in this frame.
   572  //
   573  // If this frame did a normal call, then frame.pc is a return PC, so this will
   574  // return frame.pc-1, which points into the CALL instruction. If the frame was
   575  // interrupted by a signal (e.g., profiler, segv, etc) then frame.pc is for the
   576  // trapped instruction, so this returns frame.pc. See issue #34123. Finally,
   577  // frame.pc can be at function entry when the frame is initialized without
   578  // actually running code, like in runtime.mstart, in which case this returns
   579  // frame.pc because that's the best we can do.
   580  func (u *unwinder) symPC() uintptr {
   581  	if u.flags&unwindTrap == 0 && u.frame.pc > u.frame.fn.entry() {
   582  		// Regular call.
   583  		return u.frame.pc - 1
   584  	}
   585  	// Trapping instruction or we're at the function entry point.
   586  	return u.frame.pc
   587  }
   588  
   589  // cgoCallers populates pcBuf with the cgo callers of the current frame using
   590  // the registered cgo unwinder. It returns the number of PCs written to pcBuf.
   591  // If the current frame is not a cgo frame or if there's no registered cgo
   592  // unwinder, it returns 0.
   593  func (u *unwinder) cgoCallers(pcBuf []uintptr) int {
   594  	if cgoTraceback == nil || u.frame.fn.funcID != abi.FuncID_cgocallback || u.cgoCtxt < 0 {
   595  		// We don't have a cgo unwinder (typical case), or we do but we're not
   596  		// in a cgo frame or we're out of cgo context.
   597  		return 0
   598  	}
   599  
   600  	ctxt := u.g.ptr().cgoCtxt[u.cgoCtxt]
   601  	u.cgoCtxt--
   602  	cgoContextPCs(ctxt, pcBuf)
   603  	for i, pc := range pcBuf {
   604  		if pc == 0 {
   605  			return i
   606  		}
   607  	}
   608  	return len(pcBuf)
   609  }
   610  
   611  // tracebackPCs populates pcBuf with the return addresses for each frame from u
   612  // and returns the number of PCs written to pcBuf. The returned PCs correspond
   613  // to "logical frames" rather than "physical frames"; that is if A is inlined
   614  // into B, this will still return a PCs for both A and B. This also includes PCs
   615  // generated by the cgo unwinder, if one is registered.
   616  //
   617  // If skip != 0, this skips this many logical frames.
   618  //
   619  // Callers should set the unwindSilentErrors flag on u.
   620  func tracebackPCs(u *unwinder, skip int, pcBuf []uintptr) int {
   621  	var cgoBuf [32]uintptr
   622  	n := 0
   623  	for ; n < len(pcBuf) && u.valid(); u.next() {
   624  		f := u.frame.fn
   625  		cgoN := u.cgoCallers(cgoBuf[:])
   626  
   627  		// TODO: Why does &u.cache cause u to escape? (Same in traceback2)
   628  		for iu, uf := newInlineUnwinder(f, u.symPC()); n < len(pcBuf) && uf.valid(); uf = iu.next(uf) {
   629  			sf := iu.srcFunc(uf)
   630  			if sf.funcID == abi.FuncIDWrapper && elideWrapperCalling(u.calleeFuncID) {
   631  				// ignore wrappers
   632  			} else if skip > 0 {
   633  				skip--
   634  			} else {
   635  				// Callers expect the pc buffer to contain return addresses
   636  				// and do the -1 themselves, so we add 1 to the call pc to
   637  				// create a "return pc". Since there is no actual call, here
   638  				// "return pc" just means a pc you subtract 1 from to get
   639  				// the pc of the "call". The actual no-op we insert may or
   640  				// may not be 1 byte.
   641  				pcBuf[n] = uf.pc + 1
   642  				n++
   643  			}
   644  			u.calleeFuncID = sf.funcID
   645  		}
   646  		// Add cgo frames (if we're done skipping over the requested number of
   647  		// Go frames).
   648  		if skip == 0 {
   649  			n += copy(pcBuf[n:], cgoBuf[:cgoN])
   650  		}
   651  	}
   652  	return n
   653  }
   654  
   655  // printArgs prints function arguments in traceback.
   656  func printArgs(f funcInfo, argp unsafe.Pointer, pc uintptr) {
   657  	p := (*[abi.TraceArgsMaxLen]uint8)(funcdata(f, abi.FUNCDATA_ArgInfo))
   658  	if p == nil {
   659  		return
   660  	}
   661  
   662  	liveInfo := funcdata(f, abi.FUNCDATA_ArgLiveInfo)
   663  	liveIdx := pcdatavalue(f, abi.PCDATA_ArgLiveIndex, pc)
   664  	startOffset := uint8(0xff) // smallest offset that needs liveness info (slots with a lower offset is always live)
   665  	if liveInfo != nil {
   666  		startOffset = *(*uint8)(liveInfo)
   667  	}
   668  
   669  	isLive := func(off, slotIdx uint8) bool {
   670  		if liveInfo == nil || liveIdx <= 0 {
   671  			return true // no liveness info, always live
   672  		}
   673  		if off < startOffset {
   674  			return true
   675  		}
   676  		bits := *(*uint8)(add(liveInfo, uintptr(liveIdx)+uintptr(slotIdx/8)))
   677  		return bits&(1<<(slotIdx%8)) != 0
   678  	}
   679  
   680  	print1 := func(off, sz, slotIdx uint8) {
   681  		x := readUnaligned64(add(argp, uintptr(off)))
   682  		// mask out irrelevant bits
   683  		if sz < 8 {
   684  			shift := 64 - sz*8
   685  			if goarch.BigEndian {
   686  				x = x >> shift
   687  			} else {
   688  				x = x << shift >> shift
   689  			}
   690  		}
   691  		print(hex(x))
   692  		if !isLive(off, slotIdx) {
   693  			print("?")
   694  		}
   695  	}
   696  
   697  	start := true
   698  	printcomma := func() {
   699  		if !start {
   700  			print(", ")
   701  		}
   702  	}
   703  	pi := 0
   704  	slotIdx := uint8(0) // register arg spill slot index
   705  printloop:
   706  	for {
   707  		o := p[pi]
   708  		pi++
   709  		switch o {
   710  		case abi.TraceArgsEndSeq:
   711  			break printloop
   712  		case abi.TraceArgsStartAgg:
   713  			printcomma()
   714  			print("{")
   715  			start = true
   716  			continue
   717  		case abi.TraceArgsEndAgg:
   718  			print("}")
   719  		case abi.TraceArgsDotdotdot:
   720  			printcomma()
   721  			print("...")
   722  		case abi.TraceArgsOffsetTooLarge:
   723  			printcomma()
   724  			print("_")
   725  		default:
   726  			printcomma()
   727  			sz := p[pi]
   728  			pi++
   729  			print1(o, sz, slotIdx)
   730  			if o >= startOffset {
   731  				slotIdx++
   732  			}
   733  		}
   734  		start = false
   735  	}
   736  }
   737  
   738  // funcNamePiecesForPrint returns the function name for printing to the user.
   739  // It returns three pieces so it doesn't need an allocation for string
   740  // concatenation.
   741  func funcNamePiecesForPrint(name string) (string, string, string) {
   742  	// Replace the shape name in generic function with "...".
   743  	i := bytealg.IndexByteString(name, '[')
   744  	if i < 0 {
   745  		return name, "", ""
   746  	}
   747  	j := len(name) - 1
   748  	for name[j] != ']' {
   749  		j--
   750  	}
   751  	if j <= i {
   752  		return name, "", ""
   753  	}
   754  	return name[:i], "[...]", name[j+1:]
   755  }
   756  
   757  // funcNameForPrint returns the function name for printing to the user.
   758  func funcNameForPrint(name string) string {
   759  	a, b, c := funcNamePiecesForPrint(name)
   760  	return a + b + c
   761  }
   762  
   763  // printFuncName prints a function name. name is the function name in
   764  // the binary's func data table.
   765  func printFuncName(name string) {
   766  	if name == "runtime.gopanic" {
   767  		print("panic")
   768  		return
   769  	}
   770  	a, b, c := funcNamePiecesForPrint(name)
   771  	print(a, b, c)
   772  }
   773  
   774  func printcreatedby(gp *g) {
   775  	// Show what created goroutine, except main goroutine (goid 1).
   776  	pc := gp.gopc
   777  	f := findfunc(pc)
   778  	if f.valid() && showframe(f.srcFunc(), gp, false, abi.FuncIDNormal) && gp.goid != 1 {
   779  		printcreatedby1(f, pc, gp.parentGoid)
   780  	}
   781  }
   782  
   783  func printcreatedby1(f funcInfo, pc uintptr, goid uint64) {
   784  	print("created by ")
   785  	printFuncName(funcname(f))
   786  	if goid != 0 {
   787  		print(" in goroutine ", goid)
   788  	}
   789  	print("\n")
   790  	tracepc := pc // back up to CALL instruction for funcline.
   791  	if pc > f.entry() {
   792  		tracepc -= sys.PCQuantum
   793  	}
   794  	file, line := funcline(f, tracepc)
   795  	print("\t", file, ":", line)
   796  	if pc > f.entry() {
   797  		print(" +", hex(pc-f.entry()))
   798  	}
   799  	print("\n")
   800  }
   801  
   802  func traceback(pc, sp, lr uintptr, gp *g) {
   803  	traceback1(pc, sp, lr, gp, 0)
   804  }
   805  
   806  // tracebacktrap is like traceback but expects that the PC and SP were obtained
   807  // from a trap, not from gp->sched or gp->syscallpc/gp->syscallsp or getcallerpc/getcallersp.
   808  // Because they are from a trap instead of from a saved pair,
   809  // the initial PC must not be rewound to the previous instruction.
   810  // (All the saved pairs record a PC that is a return address, so we
   811  // rewind it into the CALL instruction.)
   812  // If gp.m.libcall{g,pc,sp} information is available, it uses that information in preference to
   813  // the pc/sp/lr passed in.
   814  func tracebacktrap(pc, sp, lr uintptr, gp *g) {
   815  	if gp.m.libcallsp != 0 {
   816  		// We're in C code somewhere, traceback from the saved position.
   817  		traceback1(gp.m.libcallpc, gp.m.libcallsp, 0, gp.m.libcallg.ptr(), 0)
   818  		return
   819  	}
   820  	traceback1(pc, sp, lr, gp, unwindTrap)
   821  }
   822  
   823  func traceback1(pc, sp, lr uintptr, gp *g, flags unwindFlags) {
   824  	// If the goroutine is in cgo, and we have a cgo traceback, print that.
   825  	if iscgo && gp.m != nil && gp.m.ncgo > 0 && gp.syscallsp != 0 && gp.m.cgoCallers != nil && gp.m.cgoCallers[0] != 0 {
   826  		// Lock cgoCallers so that a signal handler won't
   827  		// change it, copy the array, reset it, unlock it.
   828  		// We are locked to the thread and are not running
   829  		// concurrently with a signal handler.
   830  		// We just have to stop a signal handler from interrupting
   831  		// in the middle of our copy.
   832  		gp.m.cgoCallersUse.Store(1)
   833  		cgoCallers := *gp.m.cgoCallers
   834  		gp.m.cgoCallers[0] = 0
   835  		gp.m.cgoCallersUse.Store(0)
   836  
   837  		printCgoTraceback(&cgoCallers)
   838  	}
   839  
   840  	if readgstatus(gp)&^_Gscan == _Gsyscall {
   841  		// Override registers if blocked in system call.
   842  		pc = gp.syscallpc
   843  		sp = gp.syscallsp
   844  		flags &^= unwindTrap
   845  	}
   846  	if gp.m != nil && gp.m.vdsoSP != 0 {
   847  		// Override registers if running in VDSO. This comes after the
   848  		// _Gsyscall check to cover VDSO calls after entersyscall.
   849  		pc = gp.m.vdsoPC
   850  		sp = gp.m.vdsoSP
   851  		flags &^= unwindTrap
   852  	}
   853  
   854  	// Print traceback.
   855  	//
   856  	// We print the first tracebackInnerFrames frames, and the last
   857  	// tracebackOuterFrames frames. There are many possible approaches to this.
   858  	// There are various complications to this:
   859  	//
   860  	// - We'd prefer to walk the stack once because in really bad situations
   861  	//   traceback may crash (and we want as much output as possible) or the stack
   862  	//   may be changing.
   863  	//
   864  	// - Each physical frame can represent several logical frames, so we might
   865  	//   have to pause in the middle of a physical frame and pick up in the middle
   866  	//   of a physical frame.
   867  	//
   868  	// - The cgo symbolizer can expand a cgo PC to more than one logical frame,
   869  	//   and involves juggling state on the C side that we don't manage. Since its
   870  	//   expansion state is managed on the C side, we can't capture the expansion
   871  	//   state part way through, and because the output strings are managed on the
   872  	//   C side, we can't capture the output. Thus, our only choice is to replay a
   873  	//   whole expansion, potentially discarding some of it.
   874  	//
   875  	// Rejected approaches:
   876  	//
   877  	// - Do two passes where the first pass just counts and the second pass does
   878  	//   all the printing. This is undesirable if the stack is corrupted or changing
   879  	//   because we won't see a partial stack if we panic.
   880  	//
   881  	// - Keep a ring buffer of the last N logical frames and use this to print
   882  	//   the bottom frames once we reach the end of the stack. This works, but
   883  	//   requires keeping a surprising amount of state on the stack, and we have
   884  	//   to run the cgo symbolizer twice—once to count frames, and a second to
   885  	//   print them—since we can't retain the strings it returns.
   886  	//
   887  	// Instead, we print the outer frames, and if we reach that limit, we clone
   888  	// the unwinder, count the remaining frames, and then skip forward and
   889  	// finish printing from the clone. This makes two passes over the outer part
   890  	// of the stack, but the single pass over the inner part ensures that's
   891  	// printed immediately and not revisited. It keeps minimal state on the
   892  	// stack. And through a combination of skip counts and limits, we can do all
   893  	// of the steps we need with a single traceback printer implementation.
   894  	//
   895  	// We could be more lax about exactly how many frames we print, for example
   896  	// always stopping and resuming on physical frame boundaries, or at least
   897  	// cgo expansion boundaries. It's not clear that's much simpler.
   898  	flags |= unwindPrintErrors
   899  	var u unwinder
   900  	tracebackWithRuntime := func(showRuntime bool) int {
   901  		const maxInt int = 0x7fffffff
   902  		u.initAt(pc, sp, lr, gp, flags)
   903  		n, lastN := traceback2(&u, showRuntime, 0, tracebackInnerFrames)
   904  		if n < tracebackInnerFrames {
   905  			// We printed the whole stack.
   906  			return n
   907  		}
   908  		// Clone the unwinder and figure out how many frames are left. This
   909  		// count will include any logical frames already printed for u's current
   910  		// physical frame.
   911  		u2 := u
   912  		remaining, _ := traceback2(&u, showRuntime, maxInt, 0)
   913  		elide := remaining - lastN - tracebackOuterFrames
   914  		if elide > 0 {
   915  			print("...", elide, " frames elided...\n")
   916  			traceback2(&u2, showRuntime, lastN+elide, tracebackOuterFrames)
   917  		} else if elide <= 0 {
   918  			// There are tracebackOuterFrames or fewer frames left to print.
   919  			// Just print the rest of the stack.
   920  			traceback2(&u2, showRuntime, lastN, tracebackOuterFrames)
   921  		}
   922  		return n
   923  	}
   924  	// By default, omits runtime frames. If that means we print nothing at all,
   925  	// repeat forcing all frames printed.
   926  	if tracebackWithRuntime(false) == 0 {
   927  		tracebackWithRuntime(true)
   928  	}
   929  	printcreatedby(gp)
   930  
   931  	if gp.ancestors == nil {
   932  		return
   933  	}
   934  	for _, ancestor := range *gp.ancestors {
   935  		printAncestorTraceback(ancestor)
   936  	}
   937  }
   938  
   939  // traceback2 prints a stack trace starting at u. It skips the first "skip"
   940  // logical frames, after which it prints at most "max" logical frames. It
   941  // returns n, which is the number of logical frames skipped and printed, and
   942  // lastN, which is the number of logical frames skipped or printed just in the
   943  // physical frame that u references.
   944  func traceback2(u *unwinder, showRuntime bool, skip, max int) (n, lastN int) {
   945  	// commitFrame commits to a logical frame and returns whether this frame
   946  	// should be printed and whether iteration should stop.
   947  	commitFrame := func() (pr, stop bool) {
   948  		if skip == 0 && max == 0 {
   949  			// Stop
   950  			return false, true
   951  		}
   952  		n++
   953  		lastN++
   954  		if skip > 0 {
   955  			// Skip
   956  			skip--
   957  			return false, false
   958  		}
   959  		// Print
   960  		max--
   961  		return true, false
   962  	}
   963  
   964  	gp := u.g.ptr()
   965  	level, _, _ := gotraceback()
   966  	var cgoBuf [32]uintptr
   967  	for ; u.valid(); u.next() {
   968  		lastN = 0
   969  		f := u.frame.fn
   970  		for iu, uf := newInlineUnwinder(f, u.symPC()); uf.valid(); uf = iu.next(uf) {
   971  			sf := iu.srcFunc(uf)
   972  			callee := u.calleeFuncID
   973  			u.calleeFuncID = sf.funcID
   974  			if !(showRuntime || showframe(sf, gp, n == 0, callee)) {
   975  				continue
   976  			}
   977  
   978  			if pr, stop := commitFrame(); stop {
   979  				return
   980  			} else if !pr {
   981  				continue
   982  			}
   983  
   984  			name := sf.name()
   985  			file, line := iu.fileLine(uf)
   986  			// Print during crash.
   987  			//	main(0x1, 0x2, 0x3)
   988  			//		/home/rsc/go/src/runtime/x.go:23 +0xf
   989  			//
   990  			printFuncName(name)
   991  			print("(")
   992  			if iu.isInlined(uf) {
   993  				print("...")
   994  			} else {
   995  				argp := unsafe.Pointer(u.frame.argp)
   996  				printArgs(f, argp, u.symPC())
   997  			}
   998  			print(")\n")
   999  			print("\t", file, ":", line)
  1000  			if !iu.isInlined(uf) {
  1001  				if u.frame.pc > f.entry() {
  1002  					print(" +", hex(u.frame.pc-f.entry()))
  1003  				}
  1004  				if gp.m != nil && gp.m.throwing >= throwTypeRuntime && gp == gp.m.curg || level >= 2 {
  1005  					print(" fp=", hex(u.frame.fp), " sp=", hex(u.frame.sp), " pc=", hex(u.frame.pc))
  1006  				}
  1007  			}
  1008  			print("\n")
  1009  		}
  1010  
  1011  		// Print cgo frames.
  1012  		if cgoN := u.cgoCallers(cgoBuf[:]); cgoN > 0 {
  1013  			var arg cgoSymbolizerArg
  1014  			anySymbolized := false
  1015  			stop := false
  1016  			for _, pc := range cgoBuf[:cgoN] {
  1017  				if cgoSymbolizer == nil {
  1018  					if pr, stop := commitFrame(); stop {
  1019  						break
  1020  					} else if pr {
  1021  						print("non-Go function at pc=", hex(pc), "\n")
  1022  					}
  1023  				} else {
  1024  					stop = printOneCgoTraceback(pc, commitFrame, &arg)
  1025  					anySymbolized = true
  1026  					if stop {
  1027  						break
  1028  					}
  1029  				}
  1030  			}
  1031  			if anySymbolized {
  1032  				// Free symbolization state.
  1033  				arg.pc = 0
  1034  				callCgoSymbolizer(&arg)
  1035  			}
  1036  			if stop {
  1037  				return
  1038  			}
  1039  		}
  1040  	}
  1041  	return n, 0
  1042  }
  1043  
  1044  // printAncestorTraceback prints the traceback of the given ancestor.
  1045  // TODO: Unify this with gentraceback and CallersFrames.
  1046  func printAncestorTraceback(ancestor ancestorInfo) {
  1047  	print("[originating from goroutine ", ancestor.goid, "]:\n")
  1048  	for fidx, pc := range ancestor.pcs {
  1049  		f := findfunc(pc) // f previously validated
  1050  		if showfuncinfo(f.srcFunc(), fidx == 0, abi.FuncIDNormal) {
  1051  			printAncestorTracebackFuncInfo(f, pc)
  1052  		}
  1053  	}
  1054  	if len(ancestor.pcs) == tracebackInnerFrames {
  1055  		print("...additional frames elided...\n")
  1056  	}
  1057  	// Show what created goroutine, except main goroutine (goid 1).
  1058  	f := findfunc(ancestor.gopc)
  1059  	if f.valid() && showfuncinfo(f.srcFunc(), false, abi.FuncIDNormal) && ancestor.goid != 1 {
  1060  		// In ancestor mode, we'll already print the goroutine ancestor.
  1061  		// Pass 0 for the goid parameter so we don't print it again.
  1062  		printcreatedby1(f, ancestor.gopc, 0)
  1063  	}
  1064  }
  1065  
  1066  // printAncestorTracebackFuncInfo prints the given function info at a given pc
  1067  // within an ancestor traceback. The precision of this info is reduced
  1068  // due to only have access to the pcs at the time of the caller
  1069  // goroutine being created.
  1070  func printAncestorTracebackFuncInfo(f funcInfo, pc uintptr) {
  1071  	u, uf := newInlineUnwinder(f, pc)
  1072  	file, line := u.fileLine(uf)
  1073  	printFuncName(u.srcFunc(uf).name())
  1074  	print("(...)\n")
  1075  	print("\t", file, ":", line)
  1076  	if pc > f.entry() {
  1077  		print(" +", hex(pc-f.entry()))
  1078  	}
  1079  	print("\n")
  1080  }
  1081  
  1082  // callers should be an internal detail,
  1083  // (and is almost identical to Callers),
  1084  // but widely used packages access it using linkname.
  1085  // Notable members of the hall of shame include:
  1086  //   - github.com/phuslu/log
  1087  //
  1088  // Do not remove or change the type signature.
  1089  // See go.dev/issue/67401.
  1090  //
  1091  //go:linkname callers
  1092  func callers(skip int, pcbuf []uintptr) int {
  1093  	sp := getcallersp()
  1094  	pc := getcallerpc()
  1095  	gp := getg()
  1096  	var n int
  1097  	systemstack(func() {
  1098  		var u unwinder
  1099  		u.initAt(pc, sp, 0, gp, unwindSilentErrors)
  1100  		n = tracebackPCs(&u, skip, pcbuf)
  1101  	})
  1102  	return n
  1103  }
  1104  
  1105  func gcallers(gp *g, skip int, pcbuf []uintptr) int {
  1106  	var u unwinder
  1107  	u.init(gp, unwindSilentErrors)
  1108  	return tracebackPCs(&u, skip, pcbuf)
  1109  }
  1110  
  1111  // showframe reports whether the frame with the given characteristics should
  1112  // be printed during a traceback.
  1113  func showframe(sf srcFunc, gp *g, firstFrame bool, calleeID abi.FuncID) bool {
  1114  	mp := getg().m
  1115  	if mp.throwing >= throwTypeRuntime && gp != nil && (gp == mp.curg || gp == mp.caughtsig.ptr()) {
  1116  		return true
  1117  	}
  1118  	return showfuncinfo(sf, firstFrame, calleeID)
  1119  }
  1120  
  1121  // showfuncinfo reports whether a function with the given characteristics should
  1122  // be printed during a traceback.
  1123  func showfuncinfo(sf srcFunc, firstFrame bool, calleeID abi.FuncID) bool {
  1124  	level, _, _ := gotraceback()
  1125  	if level > 1 {
  1126  		// Show all frames.
  1127  		return true
  1128  	}
  1129  
  1130  	if sf.funcID == abi.FuncIDWrapper && elideWrapperCalling(calleeID) {
  1131  		return false
  1132  	}
  1133  
  1134  	name := sf.name()
  1135  
  1136  	// Special case: always show runtime.gopanic frame
  1137  	// in the middle of a stack trace, so that we can
  1138  	// see the boundary between ordinary code and
  1139  	// panic-induced deferred code.
  1140  	// See golang.org/issue/5832.
  1141  	if name == "runtime.gopanic" && !firstFrame {
  1142  		return true
  1143  	}
  1144  
  1145  	return bytealg.IndexByteString(name, '.') >= 0 && (!stringslite.HasPrefix(name, "runtime.") || isExportedRuntime(name))
  1146  }
  1147  
  1148  // isExportedRuntime reports whether name is an exported runtime function.
  1149  // It is only for runtime functions, so ASCII A-Z is fine.
  1150  func isExportedRuntime(name string) bool {
  1151  	// Check and remove package qualifier.
  1152  	n := len("runtime.")
  1153  	if len(name) <= n || name[:n] != "runtime." {
  1154  		return false
  1155  	}
  1156  	name = name[n:]
  1157  	rcvr := ""
  1158  
  1159  	// Extract receiver type, if any.
  1160  	// For example, runtime.(*Func).Entry
  1161  	i := len(name) - 1
  1162  	for i >= 0 && name[i] != '.' {
  1163  		i--
  1164  	}
  1165  	if i >= 0 {
  1166  		rcvr = name[:i]
  1167  		name = name[i+1:]
  1168  		// Remove parentheses and star for pointer receivers.
  1169  		if len(rcvr) >= 3 && rcvr[0] == '(' && rcvr[1] == '*' && rcvr[len(rcvr)-1] == ')' {
  1170  			rcvr = rcvr[2 : len(rcvr)-1]
  1171  		}
  1172  	}
  1173  
  1174  	// Exported functions and exported methods on exported types.
  1175  	return len(name) > 0 && 'A' <= name[0] && name[0] <= 'Z' && (len(rcvr) == 0 || 'A' <= rcvr[0] && rcvr[0] <= 'Z')
  1176  }
  1177  
  1178  // elideWrapperCalling reports whether a wrapper function that called
  1179  // function id should be elided from stack traces.
  1180  func elideWrapperCalling(id abi.FuncID) bool {
  1181  	// If the wrapper called a panic function instead of the
  1182  	// wrapped function, we want to include it in stacks.
  1183  	return !(id == abi.FuncID_gopanic || id == abi.FuncID_sigpanic || id == abi.FuncID_panicwrap)
  1184  }
  1185  
  1186  var gStatusStrings = [...]string{
  1187  	_Gidle:      "idle",
  1188  	_Grunnable:  "runnable",
  1189  	_Grunning:   "running",
  1190  	_Gsyscall:   "syscall",
  1191  	_Gwaiting:   "waiting",
  1192  	_Gdead:      "dead",
  1193  	_Gcopystack: "copystack",
  1194  	_Gpreempted: "preempted",
  1195  }
  1196  
  1197  func goroutineheader(gp *g) {
  1198  	level, _, _ := gotraceback()
  1199  
  1200  	gpstatus := readgstatus(gp)
  1201  
  1202  	isScan := gpstatus&_Gscan != 0
  1203  	gpstatus &^= _Gscan // drop the scan bit
  1204  
  1205  	// Basic string status
  1206  	var status string
  1207  	if 0 <= gpstatus && gpstatus < uint32(len(gStatusStrings)) {
  1208  		status = gStatusStrings[gpstatus]
  1209  	} else {
  1210  		status = "???"
  1211  	}
  1212  
  1213  	// Override.
  1214  	if gpstatus == _Gwaiting && gp.waitreason != waitReasonZero {
  1215  		status = gp.waitreason.String()
  1216  	}
  1217  
  1218  	// approx time the G is blocked, in minutes
  1219  	var waitfor int64
  1220  	if (gpstatus == _Gwaiting || gpstatus == _Gsyscall) && gp.waitsince != 0 {
  1221  		waitfor = (nanotime() - gp.waitsince) / 60e9
  1222  	}
  1223  	print("goroutine ", gp.goid)
  1224  	if gp.m != nil && gp.m.throwing >= throwTypeRuntime && gp == gp.m.curg || level >= 2 {
  1225  		print(" gp=", gp)
  1226  		if gp.m != nil {
  1227  			print(" m=", gp.m.id, " mp=", gp.m)
  1228  		} else {
  1229  			print(" m=nil")
  1230  		}
  1231  	}
  1232  	print(" [", status)
  1233  	if isScan {
  1234  		print(" (scan)")
  1235  	}
  1236  	if waitfor >= 1 {
  1237  		print(", ", waitfor, " minutes")
  1238  	}
  1239  	if gp.lockedm != 0 {
  1240  		print(", locked to thread")
  1241  	}
  1242  	print("]:\n")
  1243  }
  1244  
  1245  func tracebackothers(me *g) {
  1246  	level, _, _ := gotraceback()
  1247  
  1248  	// Show the current goroutine first, if we haven't already.
  1249  	curgp := getg().m.curg
  1250  	if curgp != nil && curgp != me {
  1251  		print("\n")
  1252  		goroutineheader(curgp)
  1253  		traceback(^uintptr(0), ^uintptr(0), 0, curgp)
  1254  	}
  1255  
  1256  	// We can't call locking forEachG here because this may be during fatal
  1257  	// throw/panic, where locking could be out-of-order or a direct
  1258  	// deadlock.
  1259  	//
  1260  	// Instead, use forEachGRace, which requires no locking. We don't lock
  1261  	// against concurrent creation of new Gs, but even with allglock we may
  1262  	// miss Gs created after this loop.
  1263  	forEachGRace(func(gp *g) {
  1264  		if gp == me || gp == curgp || readgstatus(gp) == _Gdead || isSystemGoroutine(gp, false) && level < 2 {
  1265  			return
  1266  		}
  1267  		print("\n")
  1268  		goroutineheader(gp)
  1269  		// Note: gp.m == getg().m occurs when tracebackothers is called
  1270  		// from a signal handler initiated during a systemstack call.
  1271  		// The original G is still in the running state, and we want to
  1272  		// print its stack.
  1273  		if gp.m != getg().m && readgstatus(gp)&^_Gscan == _Grunning {
  1274  			print("\tgoroutine running on other thread; stack unavailable\n")
  1275  			printcreatedby(gp)
  1276  		} else {
  1277  			traceback(^uintptr(0), ^uintptr(0), 0, gp)
  1278  		}
  1279  	})
  1280  }
  1281  
  1282  // tracebackHexdump hexdumps part of stk around frame.sp and frame.fp
  1283  // for debugging purposes. If the address bad is included in the
  1284  // hexdumped range, it will mark it as well.
  1285  func tracebackHexdump(stk stack, frame *stkframe, bad uintptr) {
  1286  	const expand = 32 * goarch.PtrSize
  1287  	const maxExpand = 256 * goarch.PtrSize
  1288  	// Start around frame.sp.
  1289  	lo, hi := frame.sp, frame.sp
  1290  	// Expand to include frame.fp.
  1291  	if frame.fp != 0 && frame.fp < lo {
  1292  		lo = frame.fp
  1293  	}
  1294  	if frame.fp != 0 && frame.fp > hi {
  1295  		hi = frame.fp
  1296  	}
  1297  	// Expand a bit more.
  1298  	lo, hi = lo-expand, hi+expand
  1299  	// But don't go too far from frame.sp.
  1300  	if lo < frame.sp-maxExpand {
  1301  		lo = frame.sp - maxExpand
  1302  	}
  1303  	if hi > frame.sp+maxExpand {
  1304  		hi = frame.sp + maxExpand
  1305  	}
  1306  	// And don't go outside the stack bounds.
  1307  	if lo < stk.lo {
  1308  		lo = stk.lo
  1309  	}
  1310  	if hi > stk.hi {
  1311  		hi = stk.hi
  1312  	}
  1313  
  1314  	// Print the hex dump.
  1315  	print("stack: frame={sp:", hex(frame.sp), ", fp:", hex(frame.fp), "} stack=[", hex(stk.lo), ",", hex(stk.hi), ")\n")
  1316  	hexdumpWords(lo, hi, func(p uintptr) byte {
  1317  		switch p {
  1318  		case frame.fp:
  1319  			return '>'
  1320  		case frame.sp:
  1321  			return '<'
  1322  		case bad:
  1323  			return '!'
  1324  		}
  1325  		return 0
  1326  	})
  1327  }
  1328  
  1329  // isSystemGoroutine reports whether the goroutine g must be omitted
  1330  // in stack dumps and deadlock detector. This is any goroutine that
  1331  // starts at a runtime.* entry point, except for runtime.main,
  1332  // runtime.handleAsyncEvent (wasm only) and sometimes runtime.runfinq.
  1333  //
  1334  // If fixed is true, any goroutine that can vary between user and
  1335  // system (that is, the finalizer goroutine) is considered a user
  1336  // goroutine.
  1337  func isSystemGoroutine(gp *g, fixed bool) bool {
  1338  	// Keep this in sync with internal/trace.IsSystemGoroutine.
  1339  	f := findfunc(gp.startpc)
  1340  	if !f.valid() {
  1341  		return false
  1342  	}
  1343  	if f.funcID == abi.FuncID_runtime_main || f.funcID == abi.FuncID_corostart || f.funcID == abi.FuncID_handleAsyncEvent {
  1344  		return false
  1345  	}
  1346  	if f.funcID == abi.FuncID_runfinq {
  1347  		// We include the finalizer goroutine if it's calling
  1348  		// back into user code.
  1349  		if fixed {
  1350  			// This goroutine can vary. In fixed mode,
  1351  			// always consider it a user goroutine.
  1352  			return false
  1353  		}
  1354  		return fingStatus.Load()&fingRunningFinalizer == 0
  1355  	}
  1356  	return stringslite.HasPrefix(funcname(f), "runtime.")
  1357  }
  1358  
  1359  // SetCgoTraceback records three C functions to use to gather
  1360  // traceback information from C code and to convert that traceback
  1361  // information into symbolic information. These are used when printing
  1362  // stack traces for a program that uses cgo.
  1363  //
  1364  // The traceback and context functions may be called from a signal
  1365  // handler, and must therefore use only async-signal safe functions.
  1366  // The symbolizer function may be called while the program is
  1367  // crashing, and so must be cautious about using memory.  None of the
  1368  // functions may call back into Go.
  1369  //
  1370  // The context function will be called with a single argument, a
  1371  // pointer to a struct:
  1372  //
  1373  //	struct {
  1374  //		Context uintptr
  1375  //	}
  1376  //
  1377  // In C syntax, this struct will be
  1378  //
  1379  //	struct {
  1380  //		uintptr_t Context;
  1381  //	};
  1382  //
  1383  // If the Context field is 0, the context function is being called to
  1384  // record the current traceback context. It should record in the
  1385  // Context field whatever information is needed about the current
  1386  // point of execution to later produce a stack trace, probably the
  1387  // stack pointer and PC. In this case the context function will be
  1388  // called from C code.
  1389  //
  1390  // If the Context field is not 0, then it is a value returned by a
  1391  // previous call to the context function. This case is called when the
  1392  // context is no longer needed; that is, when the Go code is returning
  1393  // to its C code caller. This permits the context function to release
  1394  // any associated resources.
  1395  //
  1396  // While it would be correct for the context function to record a
  1397  // complete a stack trace whenever it is called, and simply copy that
  1398  // out in the traceback function, in a typical program the context
  1399  // function will be called many times without ever recording a
  1400  // traceback for that context. Recording a complete stack trace in a
  1401  // call to the context function is likely to be inefficient.
  1402  //
  1403  // The traceback function will be called with a single argument, a
  1404  // pointer to a struct:
  1405  //
  1406  //	struct {
  1407  //		Context    uintptr
  1408  //		SigContext uintptr
  1409  //		Buf        *uintptr
  1410  //		Max        uintptr
  1411  //	}
  1412  //
  1413  // In C syntax, this struct will be
  1414  //
  1415  //	struct {
  1416  //		uintptr_t  Context;
  1417  //		uintptr_t  SigContext;
  1418  //		uintptr_t* Buf;
  1419  //		uintptr_t  Max;
  1420  //	};
  1421  //
  1422  // The Context field will be zero to gather a traceback from the
  1423  // current program execution point. In this case, the traceback
  1424  // function will be called from C code.
  1425  //
  1426  // Otherwise Context will be a value previously returned by a call to
  1427  // the context function. The traceback function should gather a stack
  1428  // trace from that saved point in the program execution. The traceback
  1429  // function may be called from an execution thread other than the one
  1430  // that recorded the context, but only when the context is known to be
  1431  // valid and unchanging. The traceback function may also be called
  1432  // deeper in the call stack on the same thread that recorded the
  1433  // context. The traceback function may be called multiple times with
  1434  // the same Context value; it will usually be appropriate to cache the
  1435  // result, if possible, the first time this is called for a specific
  1436  // context value.
  1437  //
  1438  // If the traceback function is called from a signal handler on a Unix
  1439  // system, SigContext will be the signal context argument passed to
  1440  // the signal handler (a C ucontext_t* cast to uintptr_t). This may be
  1441  // used to start tracing at the point where the signal occurred. If
  1442  // the traceback function is not called from a signal handler,
  1443  // SigContext will be zero.
  1444  //
  1445  // Buf is where the traceback information should be stored. It should
  1446  // be PC values, such that Buf[0] is the PC of the caller, Buf[1] is
  1447  // the PC of that function's caller, and so on.  Max is the maximum
  1448  // number of entries to store.  The function should store a zero to
  1449  // indicate the top of the stack, or that the caller is on a different
  1450  // stack, presumably a Go stack.
  1451  //
  1452  // Unlike runtime.Callers, the PC values returned should, when passed
  1453  // to the symbolizer function, return the file/line of the call
  1454  // instruction.  No additional subtraction is required or appropriate.
  1455  //
  1456  // On all platforms, the traceback function is invoked when a call from
  1457  // Go to C to Go requests a stack trace. On linux/amd64, linux/ppc64le,
  1458  // linux/arm64, and freebsd/amd64, the traceback function is also invoked
  1459  // when a signal is received by a thread that is executing a cgo call.
  1460  // The traceback function should not make assumptions about when it is
  1461  // called, as future versions of Go may make additional calls.
  1462  //
  1463  // The symbolizer function will be called with a single argument, a
  1464  // pointer to a struct:
  1465  //
  1466  //	struct {
  1467  //		PC      uintptr // program counter to fetch information for
  1468  //		File    *byte   // file name (NUL terminated)
  1469  //		Lineno  uintptr // line number
  1470  //		Func    *byte   // function name (NUL terminated)
  1471  //		Entry   uintptr // function entry point
  1472  //		More    uintptr // set non-zero if more info for this PC
  1473  //		Data    uintptr // unused by runtime, available for function
  1474  //	}
  1475  //
  1476  // In C syntax, this struct will be
  1477  //
  1478  //	struct {
  1479  //		uintptr_t PC;
  1480  //		char*     File;
  1481  //		uintptr_t Lineno;
  1482  //		char*     Func;
  1483  //		uintptr_t Entry;
  1484  //		uintptr_t More;
  1485  //		uintptr_t Data;
  1486  //	};
  1487  //
  1488  // The PC field will be a value returned by a call to the traceback
  1489  // function.
  1490  //
  1491  // The first time the function is called for a particular traceback,
  1492  // all the fields except PC will be 0. The function should fill in the
  1493  // other fields if possible, setting them to 0/nil if the information
  1494  // is not available. The Data field may be used to store any useful
  1495  // information across calls. The More field should be set to non-zero
  1496  // if there is more information for this PC, zero otherwise. If More
  1497  // is set non-zero, the function will be called again with the same
  1498  // PC, and may return different information (this is intended for use
  1499  // with inlined functions). If More is zero, the function will be
  1500  // called with the next PC value in the traceback. When the traceback
  1501  // is complete, the function will be called once more with PC set to
  1502  // zero; this may be used to free any information. Each call will
  1503  // leave the fields of the struct set to the same values they had upon
  1504  // return, except for the PC field when the More field is zero. The
  1505  // function must not keep a copy of the struct pointer between calls.
  1506  //
  1507  // When calling SetCgoTraceback, the version argument is the version
  1508  // number of the structs that the functions expect to receive.
  1509  // Currently this must be zero.
  1510  //
  1511  // The symbolizer function may be nil, in which case the results of
  1512  // the traceback function will be displayed as numbers. If the
  1513  // traceback function is nil, the symbolizer function will never be
  1514  // called. The context function may be nil, in which case the
  1515  // traceback function will only be called with the context field set
  1516  // to zero.  If the context function is nil, then calls from Go to C
  1517  // to Go will not show a traceback for the C portion of the call stack.
  1518  //
  1519  // SetCgoTraceback should be called only once, ideally from an init function.
  1520  func SetCgoTraceback(version int, traceback, context, symbolizer unsafe.Pointer) {
  1521  	if version != 0 {
  1522  		panic("unsupported version")
  1523  	}
  1524  
  1525  	if cgoTraceback != nil && cgoTraceback != traceback ||
  1526  		cgoContext != nil && cgoContext != context ||
  1527  		cgoSymbolizer != nil && cgoSymbolizer != symbolizer {
  1528  		panic("call SetCgoTraceback only once")
  1529  	}
  1530  
  1531  	cgoTraceback = traceback
  1532  	cgoContext = context
  1533  	cgoSymbolizer = symbolizer
  1534  
  1535  	// The context function is called when a C function calls a Go
  1536  	// function. As such it is only called by C code in runtime/cgo.
  1537  	if _cgo_set_context_function != nil {
  1538  		cgocall(_cgo_set_context_function, context)
  1539  	}
  1540  }
  1541  
  1542  var cgoTraceback unsafe.Pointer
  1543  var cgoContext unsafe.Pointer
  1544  var cgoSymbolizer unsafe.Pointer
  1545  
  1546  // cgoTracebackArg is the type passed to cgoTraceback.
  1547  type cgoTracebackArg struct {
  1548  	context    uintptr
  1549  	sigContext uintptr
  1550  	buf        *uintptr
  1551  	max        uintptr
  1552  }
  1553  
  1554  // cgoContextArg is the type passed to the context function.
  1555  type cgoContextArg struct {
  1556  	context uintptr
  1557  }
  1558  
  1559  // cgoSymbolizerArg is the type passed to cgoSymbolizer.
  1560  type cgoSymbolizerArg struct {
  1561  	pc       uintptr
  1562  	file     *byte
  1563  	lineno   uintptr
  1564  	funcName *byte
  1565  	entry    uintptr
  1566  	more     uintptr
  1567  	data     uintptr
  1568  }
  1569  
  1570  // printCgoTraceback prints a traceback of callers.
  1571  func printCgoTraceback(callers *cgoCallers) {
  1572  	if cgoSymbolizer == nil {
  1573  		for _, c := range callers {
  1574  			if c == 0 {
  1575  				break
  1576  			}
  1577  			print("non-Go function at pc=", hex(c), "\n")
  1578  		}
  1579  		return
  1580  	}
  1581  
  1582  	commitFrame := func() (pr, stop bool) { return true, false }
  1583  	var arg cgoSymbolizerArg
  1584  	for _, c := range callers {
  1585  		if c == 0 {
  1586  			break
  1587  		}
  1588  		printOneCgoTraceback(c, commitFrame, &arg)
  1589  	}
  1590  	arg.pc = 0
  1591  	callCgoSymbolizer(&arg)
  1592  }
  1593  
  1594  // printOneCgoTraceback prints the traceback of a single cgo caller.
  1595  // This can print more than one line because of inlining.
  1596  // It returns the "stop" result of commitFrame.
  1597  func printOneCgoTraceback(pc uintptr, commitFrame func() (pr, stop bool), arg *cgoSymbolizerArg) bool {
  1598  	arg.pc = pc
  1599  	for {
  1600  		if pr, stop := commitFrame(); stop {
  1601  			return true
  1602  		} else if !pr {
  1603  			continue
  1604  		}
  1605  
  1606  		callCgoSymbolizer(arg)
  1607  		if arg.funcName != nil {
  1608  			// Note that we don't print any argument
  1609  			// information here, not even parentheses.
  1610  			// The symbolizer must add that if appropriate.
  1611  			println(gostringnocopy(arg.funcName))
  1612  		} else {
  1613  			println("non-Go function")
  1614  		}
  1615  		print("\t")
  1616  		if arg.file != nil {
  1617  			print(gostringnocopy(arg.file), ":", arg.lineno, " ")
  1618  		}
  1619  		print("pc=", hex(pc), "\n")
  1620  		if arg.more == 0 {
  1621  			return false
  1622  		}
  1623  	}
  1624  }
  1625  
  1626  // callCgoSymbolizer calls the cgoSymbolizer function.
  1627  func callCgoSymbolizer(arg *cgoSymbolizerArg) {
  1628  	call := cgocall
  1629  	if panicking.Load() > 0 || getg().m.curg != getg() {
  1630  		// We do not want to call into the scheduler when panicking
  1631  		// or when on the system stack.
  1632  		call = asmcgocall
  1633  	}
  1634  	if msanenabled {
  1635  		msanwrite(unsafe.Pointer(arg), unsafe.Sizeof(cgoSymbolizerArg{}))
  1636  	}
  1637  	if asanenabled {
  1638  		asanwrite(unsafe.Pointer(arg), unsafe.Sizeof(cgoSymbolizerArg{}))
  1639  	}
  1640  	call(cgoSymbolizer, noescape(unsafe.Pointer(arg)))
  1641  }
  1642  
  1643  // cgoContextPCs gets the PC values from a cgo traceback.
  1644  func cgoContextPCs(ctxt uintptr, buf []uintptr) {
  1645  	if cgoTraceback == nil {
  1646  		return
  1647  	}
  1648  	call := cgocall
  1649  	if panicking.Load() > 0 || getg().m.curg != getg() {
  1650  		// We do not want to call into the scheduler when panicking
  1651  		// or when on the system stack.
  1652  		call = asmcgocall
  1653  	}
  1654  	arg := cgoTracebackArg{
  1655  		context: ctxt,
  1656  		buf:     (*uintptr)(noescape(unsafe.Pointer(&buf[0]))),
  1657  		max:     uintptr(len(buf)),
  1658  	}
  1659  	if msanenabled {
  1660  		msanwrite(unsafe.Pointer(&arg), unsafe.Sizeof(arg))
  1661  	}
  1662  	if asanenabled {
  1663  		asanwrite(unsafe.Pointer(&arg), unsafe.Sizeof(arg))
  1664  	}
  1665  	call(cgoTraceback, noescape(unsafe.Pointer(&arg)))
  1666  }
  1667  

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