src/runtime/stkframe.go - go - Git at Google

 // Copyright 2022 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package runtime

 import (
 	"internal/abi"
 	"internal/goarch"
 	"runtime/internal/sys"
 	"unsafe"
 )

 // A stkframe holds information about a single physical stack frame.
 type stkframe struct {
 	// fn is the function being run in this frame. If there is
 	// inlining, this is the outermost function.
 	fn funcInfo

 	// pc is the program counter within fn.
 	//
 	// The meaning of this is subtle:
 	//
 	// - Typically, this frame performed a regular function call
 	//   and this is the return PC (just after the CALL
 	//   instruction). In this case, pc-1 reflects the CALL
 	//   instruction itself and is the correct source of symbolic
 	//   information.
 	//
 	// - If this frame "called" sigpanic, then pc is the
 	//   instruction that panicked, and pc is the correct address
 	//   to use for symbolic information.
 	//
 	// - If this is the innermost frame, then PC is where
 	//   execution will continue, but it may not be the
 	//   instruction following a CALL. This may be from
 	//   cooperative preemption, in which case this is the
 	//   instruction after the call to morestack. Or this may be
 	//   from a signal or an un-started goroutine, in which case
 	//   PC could be any instruction, including the first
 	//   instruction in a function. Conventionally, we use pc-1
 	//   for symbolic information, unless pc == fn.entry(), in
 	//   which case we use pc.
 	pc uintptr

 	// continpc is the PC where execution will continue in fn, or
 	// 0 if execution will not continue in this frame.
 	//
 	// This is usually the same as pc, unless this frame "called"
 	// sigpanic, in which case it's either the address of
 	// deferreturn or 0 if this frame will never execute again.
 	//
 	// This is the PC to use to look up GC liveness for this frame.
 	continpc uintptr

 	lr   uintptr // program counter at caller aka link register
 	sp   uintptr // stack pointer at pc
 	fp   uintptr // stack pointer at caller aka frame pointer
 	varp uintptr // top of local variables
 	argp uintptr // pointer to function arguments
 }

 // reflectMethodValue is a partial duplicate of reflect.makeFuncImpl
 // and reflect.methodValue.
 type reflectMethodValue struct {
 	fn     uintptr
 	stack  *bitvector // ptrmap for both args and results
 	argLen uintptr    // just args
 }

 // argBytes returns the argument frame size for a call to frame.fn.
 func (frame *stkframe) argBytes() uintptr {
 	if frame.fn.args != abi.ArgsSizeUnknown {
 		return uintptr(frame.fn.args)
 	}
 	// This is an uncommon and complicated case. Fall back to fully
 	// fetching the argument map to compute its size.
 	argMap, _ := frame.argMapInternal()
 	return uintptr(argMap.n) * goarch.PtrSize
 }

 // argMapInternal is used internally by stkframe to fetch special
 // argument maps.
 //
 // argMap.n is always populated with the size of the argument map.
 //
 // argMap.bytedata is only populated for dynamic argument maps (used
 // by reflect). If the caller requires the argument map, it should use
 // this if non-nil, and otherwise fetch the argument map using the
 // current PC.
 //
 // hasReflectStackObj indicates that this frame also has a reflect
 // function stack object, which the caller must synthesize.
 func (frame *stkframe) argMapInternal() (argMap bitvector, hasReflectStackObj bool) {
 	f := frame.fn
 	if f.args != abi.ArgsSizeUnknown {
 		argMap.n = f.args / goarch.PtrSize
 		return
 	}
 	// Extract argument bitmaps for reflect stubs from the calls they made to reflect.
 	switch funcname(f) {
 	case "reflect.makeFuncStub", "reflect.methodValueCall":
 		// These take a *reflect.methodValue as their
 		// context register and immediately save it to 0(SP).
 		// Get the methodValue from 0(SP).
 		arg0 := frame.sp + sys.MinFrameSize

 		minSP := frame.fp
 		if !usesLR {
 			// The CALL itself pushes a word.
 			// Undo that adjustment.
 			minSP -= goarch.PtrSize
 		}
 		if arg0 >= minSP {
 			// The function hasn't started yet.
 			// This only happens if f was the
 			// start function of a new goroutine
 			// that hasn't run yet *and* f takes
 			// no arguments and has no results
 			// (otherwise it will get wrapped in a
 			// closure). In this case, we can't
 			// reach into its locals because it
 			// doesn't have locals yet, but we
 			// also know its argument map is
 			// empty.
 			if frame.pc != f.entry() {
 				print("runtime: confused by ", funcname(f), ": no frame (sp=", hex(frame.sp), " fp=", hex(frame.fp), ") at entry+", hex(frame.pc-f.entry()), "\n")
 				throw("reflect mismatch")
 			}
 			return bitvector{}, false // No locals, so also no stack objects
 		}
 		hasReflectStackObj = true
 		mv := *(**reflectMethodValue)(unsafe.Pointer(arg0))
 		// Figure out whether the return values are valid.
 		// Reflect will update this value after it copies
 		// in the return values.
 		retValid := *(*bool)(unsafe.Pointer(arg0 + 4*goarch.PtrSize))
 		if mv.fn != f.entry() {
 			print("runtime: confused by ", funcname(f), "\n")
 			throw("reflect mismatch")
 		}
 		argMap = *mv.stack
 		if !retValid {
 			// argMap.n includes the results, but
 			// those aren't valid, so drop them.
 			n := int32((mv.argLen &^ (goarch.PtrSize - 1)) / goarch.PtrSize)
 			if n < argMap.n {
 				argMap.n = n
 			}
 		}
 	}
 	return
 }

 // getStackMap returns the locals and arguments live pointer maps, and
 // stack object list for frame.
 func (frame *stkframe) getStackMap(debug bool) (locals, args bitvector, objs []stackObjectRecord) {
 	targetpc := frame.continpc
 	if targetpc == 0 {
 		// Frame is dead. Return empty bitvectors.
 		return
 	}

 	f := frame.fn
 	pcdata := int32(-1)
 	if targetpc != f.entry() {
 		// Back up to the CALL. If we're at the function entry
 		// point, we want to use the entry map (-1), even if
 		// the first instruction of the function changes the
 		// stack map.
 		targetpc--
 		pcdata = pcdatavalue(f, abi.PCDATA_StackMapIndex, targetpc)
 	}
 	if pcdata == -1 {
 		// We do not have a valid pcdata value but there might be a
 		// stackmap for this function. It is likely that we are looking
 		// at the function prologue, assume so and hope for the best.
 		pcdata = 0
 	}

 	// Local variables.
 	size := frame.varp - frame.sp
 	var minsize uintptr
 	switch goarch.ArchFamily {
 	case goarch.ARM64:
 		minsize = sys.StackAlign
 	default:
 		minsize = sys.MinFrameSize
 	}
 	if size > minsize {
 		stackid := pcdata
 		stkmap := (*stackmap)(funcdata(f, abi.FUNCDATA_LocalsPointerMaps))
 		if stkmap == nil || stkmap.n <= 0 {
 			print("runtime: frame ", funcname(f), " untyped locals ", hex(frame.varp-size), "+", hex(size), "\n")
 			throw("missing stackmap")
 		}
 		// If nbit == 0, there's no work to do.
 		if stkmap.nbit > 0 {
 			if stackid < 0 || stackid >= stkmap.n {
 				// don't know where we are
 				print("runtime: pcdata is ", stackid, " and ", stkmap.n, " locals stack map entries for ", funcname(f), " (targetpc=", hex(targetpc), ")\n")
 				throw("bad symbol table")
 			}
 			locals = stackmapdata(stkmap, stackid)
 			if stackDebug >= 3 && debug {
 				print("      locals ", stackid, "/", stkmap.n, " ", locals.n, " words ", locals.bytedata, "\n")
 			}
 		} else if stackDebug >= 3 && debug {
 			print("      no locals to adjust\n")
 		}
 	}

 	// Arguments. First fetch frame size and special-case argument maps.
 	var isReflect bool
 	args, isReflect = frame.argMapInternal()
 	if args.n > 0 && args.bytedata == nil {
 		// Non-empty argument frame, but not a special map.
 		// Fetch the argument map at pcdata.
 		stackmap := (*stackmap)(funcdata(f, abi.FUNCDATA_ArgsPointerMaps))
 		if stackmap == nil || stackmap.n <= 0 {
 			print("runtime: frame ", funcname(f), " untyped args ", hex(frame.argp), "+", hex(args.n*goarch.PtrSize), "\n")
 			throw("missing stackmap")
 		}
 		if pcdata < 0 || pcdata >= stackmap.n {
 			// don't know where we are
 			print("runtime: pcdata is ", pcdata, " and ", stackmap.n, " args stack map entries for ", funcname(f), " (targetpc=", hex(targetpc), ")\n")
 			throw("bad symbol table")
 		}
 		if stackmap.nbit == 0 {
 			args.n = 0
 		} else {
 			args = stackmapdata(stackmap, pcdata)
 		}
 	}

 	// stack objects.
 	if (GOARCH == "amd64" || GOARCH == "arm64" || GOARCH == "loong64" || GOARCH == "ppc64" || GOARCH == "ppc64le" || GOARCH == "riscv64") &&
 		unsafe.Sizeof(abi.RegArgs{}) > 0 && isReflect {
 		// For reflect.makeFuncStub and reflect.methodValueCall,
 		// we need to fake the stack object record.
 		// These frames contain an internal/abi.RegArgs at a hard-coded offset.
 		// This offset matches the assembly code on amd64 and arm64.
 		objs = methodValueCallFrameObjs[:]
 	} else {
 		p := funcdata(f, abi.FUNCDATA_StackObjects)
 		if p != nil {
 			n := *(*uintptr)(p)
 			p = add(p, goarch.PtrSize)
 			r0 := (*stackObjectRecord)(noescape(p))
 			objs = unsafe.Slice(r0, int(n))
 			// Note: the noescape above is needed to keep
 			// getStackMap from "leaking param content:
 			// frame".  That leak propagates up to getgcmask, then
 			// GCMask, then verifyGCInfo, which converts the stack
 			// gcinfo tests into heap gcinfo tests :(
 		}
 	}

 	return
 }

 var methodValueCallFrameObjs [1]stackObjectRecord // initialized in stackobjectinit

 func stkobjinit() {
 	var abiRegArgsEface any = abi.RegArgs{}
 	abiRegArgsType := efaceOf(&abiRegArgsEface)._type
 	if abiRegArgsType.Kind_&abi.KindGCProg != 0 {
 		throw("abiRegArgsType needs GC Prog, update methodValueCallFrameObjs")
 	}
 	// Set methodValueCallFrameObjs[0].gcdataoff so that
 	// stackObjectRecord.gcdata() will work correctly with it.
 	ptr := uintptr(unsafe.Pointer(&methodValueCallFrameObjs[0]))
 	var mod *moduledata
 	for datap := &firstmoduledata; datap != nil; datap = datap.next {
 		if datap.gofunc <= ptr && ptr < datap.end {
 			mod = datap
 			break
 		}
 	}
 	if mod == nil {
 		throw("methodValueCallFrameObjs is not in a module")
 	}
 	methodValueCallFrameObjs[0] = stackObjectRecord{
 		off:       -int32(alignUp(abiRegArgsType.Size_, 8)), // It's always the highest address local.
 		size:      int32(abiRegArgsType.Size_),
 		_ptrdata:  int32(abiRegArgsType.PtrBytes),
 		gcdataoff: uint32(uintptr(unsafe.Pointer(abiRegArgsType.GCData)) - mod.rodata),
 	}
 }
	// Copyright 2022 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	package runtime

	import (
	"internal/abi"
	"internal/goarch"
	"runtime/internal/sys"
	"unsafe"
	)

	// A stkframe holds information about a single physical stack frame.
	type stkframe struct {
	// fn is the function being run in this frame. If there is
	// inlining, this is the outermost function.
	fn funcInfo

	// pc is the program counter within fn.
	//
	// The meaning of this is subtle:
	//
	// - Typically, this frame performed a regular function call
	// and this is the return PC (just after the CALL
	// instruction). In this case, pc-1 reflects the CALL
	// instruction itself and is the correct source of symbolic
	// information.
	//
	// - If this frame "called" sigpanic, then pc is the
	// instruction that panicked, and pc is the correct address
	// to use for symbolic information.
	//
	// - If this is the innermost frame, then PC is where
	// execution will continue, but it may not be the
	// instruction following a CALL. This may be from
	// cooperative preemption, in which case this is the
	// instruction after the call to morestack. Or this may be
	// from a signal or an un-started goroutine, in which case
	// PC could be any instruction, including the first
	// instruction in a function. Conventionally, we use pc-1
	// for symbolic information, unless pc == fn.entry(), in
	// which case we use pc.
	pc uintptr

	// continpc is the PC where execution will continue in fn, or
	// 0 if execution will not continue in this frame.
	//
	// This is usually the same as pc, unless this frame "called"
	// sigpanic, in which case it's either the address of
	// deferreturn or 0 if this frame will never execute again.
	//
	// This is the PC to use to look up GC liveness for this frame.
	continpc uintptr

	lr uintptr // program counter at caller aka link register
	sp uintptr // stack pointer at pc
	fp uintptr // stack pointer at caller aka frame pointer
	varp uintptr // top of local variables
	argp uintptr // pointer to function arguments
	}

	// reflectMethodValue is a partial duplicate of reflect.makeFuncImpl
	// and reflect.methodValue.
	type reflectMethodValue struct {
	fn uintptr
	stack *bitvector // ptrmap for both args and results
	argLen uintptr // just args
	}

	// argBytes returns the argument frame size for a call to frame.fn.
	func (frame *stkframe) argBytes() uintptr {
	if frame.fn.args != abi.ArgsSizeUnknown {
	return uintptr(frame.fn.args)
	}
	// This is an uncommon and complicated case. Fall back to fully
	// fetching the argument map to compute its size.
	argMap, _ := frame.argMapInternal()
	return uintptr(argMap.n) * goarch.PtrSize
	}

	// argMapInternal is used internally by stkframe to fetch special
	// argument maps.
	//
	// argMap.n is always populated with the size of the argument map.
	//
	// argMap.bytedata is only populated for dynamic argument maps (used
	// by reflect). If the caller requires the argument map, it should use
	// this if non-nil, and otherwise fetch the argument map using the
	// current PC.
	//
	// hasReflectStackObj indicates that this frame also has a reflect
	// function stack object, which the caller must synthesize.
	func (frame *stkframe) argMapInternal() (argMap bitvector, hasReflectStackObj bool) {
	f := frame.fn
	if f.args != abi.ArgsSizeUnknown {
	argMap.n = f.args / goarch.PtrSize
	return
	}
	// Extract argument bitmaps for reflect stubs from the calls they made to reflect.
	switch funcname(f) {
	case "reflect.makeFuncStub", "reflect.methodValueCall":
	// These take a *reflect.methodValue as their
	// context register and immediately save it to 0(SP).
	// Get the methodValue from 0(SP).
	arg0 := frame.sp + sys.MinFrameSize

	minSP := frame.fp
	if !usesLR {
	// The CALL itself pushes a word.
	// Undo that adjustment.
	minSP -= goarch.PtrSize
	}
	if arg0 >= minSP {
	// The function hasn't started yet.
	// This only happens if f was the
	// start function of a new goroutine
	// that hasn't run yet and f takes
	// no arguments and has no results
	// (otherwise it will get wrapped in a
	// closure). In this case, we can't
	// reach into its locals because it
	// doesn't have locals yet, but we
	// also know its argument map is
	// empty.
	if frame.pc != f.entry() {
	print("runtime: confused by ", funcname(f), ": no frame (sp=", hex(frame.sp), " fp=", hex(frame.fp), ") at entry+", hex(frame.pc-f.entry()), "\n")
	throw("reflect mismatch")
	}
	return bitvector{}, false // No locals, so also no stack objects
	}
	hasReflectStackObj = true
	mv := (*reflectMethodValue)(unsafe.Pointer(arg0))
	// Figure out whether the return values are valid.
	// Reflect will update this value after it copies
	// in the return values.
	retValid := (bool)(unsafe.Pointer(arg0 + 4*goarch.PtrSize))
	if mv.fn != f.entry() {
	print("runtime: confused by ", funcname(f), "\n")
	throw("reflect mismatch")
	}
	argMap = *mv.stack
	if !retValid {
	// argMap.n includes the results, but
	// those aren't valid, so drop them.
	n := int32((mv.argLen &^ (goarch.PtrSize - 1)) / goarch.PtrSize)
	if n < argMap.n {
	argMap.n = n
	}
	}
	}
	return
	}

	// getStackMap returns the locals and arguments live pointer maps, and
	// stack object list for frame.
	func (frame *stkframe) getStackMap(debug bool) (locals, args bitvector, objs []stackObjectRecord) {
	targetpc := frame.continpc
	if targetpc == 0 {
	// Frame is dead. Return empty bitvectors.
	return
	}

	f := frame.fn
	pcdata := int32(-1)
	if targetpc != f.entry() {
	// Back up to the CALL. If we're at the function entry
	// point, we want to use the entry map (-1), even if
	// the first instruction of the function changes the
	// stack map.
	targetpc--
	pcdata = pcdatavalue(f, abi.PCDATA_StackMapIndex, targetpc)
	}
	if pcdata == -1 {
	// We do not have a valid pcdata value but there might be a
	// stackmap for this function. It is likely that we are looking
	// at the function prologue, assume so and hope for the best.
	pcdata = 0
	}

	// Local variables.
	size := frame.varp - frame.sp
	var minsize uintptr
	switch goarch.ArchFamily {
	case goarch.ARM64:
	minsize = sys.StackAlign
	default:
	minsize = sys.MinFrameSize
	}
	if size > minsize {
	stackid := pcdata
	stkmap := (*stackmap)(funcdata(f, abi.FUNCDATA_LocalsPointerMaps))
	if stkmap == nil \|\| stkmap.n <= 0 {
	print("runtime: frame ", funcname(f), " untyped locals ", hex(frame.varp-size), "+", hex(size), "\n")
	throw("missing stackmap")
	}
	// If nbit == 0, there's no work to do.
	if stkmap.nbit > 0 {
	if stackid < 0 \|\| stackid >= stkmap.n {
	// don't know where we are
	print("runtime: pcdata is ", stackid, " and ", stkmap.n, " locals stack map entries for ", funcname(f), " (targetpc=", hex(targetpc), ")\n")
	throw("bad symbol table")
	}
	locals = stackmapdata(stkmap, stackid)
	if stackDebug >= 3 && debug {
	print(" locals ", stackid, "/", stkmap.n, " ", locals.n, " words ", locals.bytedata, "\n")
	}
	} else if stackDebug >= 3 && debug {
	print(" no locals to adjust\n")
	}
	}

	// Arguments. First fetch frame size and special-case argument maps.
	var isReflect bool
	args, isReflect = frame.argMapInternal()
	if args.n > 0 && args.bytedata == nil {
	// Non-empty argument frame, but not a special map.
	// Fetch the argument map at pcdata.
	stackmap := (*stackmap)(funcdata(f, abi.FUNCDATA_ArgsPointerMaps))
	if stackmap == nil \|\| stackmap.n <= 0 {
	print("runtime: frame ", funcname(f), " untyped args ", hex(frame.argp), "+", hex(args.n*goarch.PtrSize), "\n")
	throw("missing stackmap")
	}
	if pcdata < 0 \|\| pcdata >= stackmap.n {
	// don't know where we are
	print("runtime: pcdata is ", pcdata, " and ", stackmap.n, " args stack map entries for ", funcname(f), " (targetpc=", hex(targetpc), ")\n")
	throw("bad symbol table")
	}
	if stackmap.nbit == 0 {
	args.n = 0
	} else {
	args = stackmapdata(stackmap, pcdata)
	}
	}

	// stack objects.
	if (GOARCH == "amd64" \|\| GOARCH == "arm64" \|\| GOARCH == "loong64" \|\| GOARCH == "ppc64" \|\| GOARCH == "ppc64le" \|\| GOARCH == "riscv64") &&
	unsafe.Sizeof(abi.RegArgs{}) > 0 && isReflect {
	// For reflect.makeFuncStub and reflect.methodValueCall,
	// we need to fake the stack object record.
	// These frames contain an internal/abi.RegArgs at a hard-coded offset.
	// This offset matches the assembly code on amd64 and arm64.
	objs = methodValueCallFrameObjs[:]
	} else {
	p := funcdata(f, abi.FUNCDATA_StackObjects)
	if p != nil {
	n := (uintptr)(p)
	p = add(p, goarch.PtrSize)
	r0 := (*stackObjectRecord)(noescape(p))
	objs = unsafe.Slice(r0, int(n))
	// Note: the noescape above is needed to keep
	// getStackMap from "leaking param content:
	// frame". That leak propagates up to getgcmask, then
	// GCMask, then verifyGCInfo, which converts the stack
	// gcinfo tests into heap gcinfo tests :(
	}
	}

	return
	}

	var methodValueCallFrameObjs [1]stackObjectRecord // initialized in stackobjectinit

	func stkobjinit() {
	var abiRegArgsEface any = abi.RegArgs{}
	abiRegArgsType := efaceOf(&abiRegArgsEface)._type
	if abiRegArgsType.Kind_&abi.KindGCProg != 0 {
	throw("abiRegArgsType needs GC Prog, update methodValueCallFrameObjs")
	}
	// Set methodValueCallFrameObjs[0].gcdataoff so that
	// stackObjectRecord.gcdata() will work correctly with it.
	ptr := uintptr(unsafe.Pointer(&methodValueCallFrameObjs[0]))
	var mod *moduledata
	for datap := &firstmoduledata; datap != nil; datap = datap.next {
	if datap.gofunc <= ptr && ptr < datap.end {
	mod = datap
	break
	}
	}
	if mod == nil {
	throw("methodValueCallFrameObjs is not in a module")
	}
	methodValueCallFrameObjs[0] = stackObjectRecord{
	off: -int32(alignUp(abiRegArgsType.Size_, 8)), // It's always the highest address local.
	size: int32(abiRegArgsType.Size_),
	_ptrdata: int32(abiRegArgsType.PtrBytes),
	gcdataoff: uint32(uintptr(unsafe.Pointer(abiRegArgsType.GCData)) - mod.rodata),
	}
	}