Adding upstream version 1.16.10.upstream/1.16.10upstream

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

1 files changed, 1041 insertions, 0 deletions

diff --git a/src/runtime/symtab.go b/src/runtime/symtab.go
new file mode 100644
index 0000000..3341fc4
--- /dev/null
+++ b/src/runtime/symtab.go
@@ -0,0 +1,1041 @@
+// Copyright 2014 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 (
+	"runtime/internal/atomic"
+	"runtime/internal/sys"
+	"unsafe"
+)
+
+// Frames may be used to get function/file/line information for a
+// slice of PC values returned by Callers.
+type Frames struct {
+	// callers is a slice of PCs that have not yet been expanded to frames.
+	callers []uintptr
+
+	// frames is a slice of Frames that have yet to be returned.
+	frames     []Frame
+	frameStore [2]Frame
+}
+
+// Frame is the information returned by Frames for each call frame.
+type Frame struct {
+	// PC is the program counter for the location in this frame.
+	// For a frame that calls another frame, this will be the
+	// program counter of a call instruction. Because of inlining,
+	// multiple frames may have the same PC value, but different
+	// symbolic information.
+	PC uintptr
+
+	// Func is the Func value of this call frame. This may be nil
+	// for non-Go code or fully inlined functions.
+	Func *Func
+
+	// Function is the package path-qualified function name of
+	// this call frame. If non-empty, this string uniquely
+	// identifies a single function in the program.
+	// This may be the empty string if not known.
+	// If Func is not nil then Function == Func.Name().
+	Function string
+
+	// File and Line are the file name and line number of the
+	// location in this frame. For non-leaf frames, this will be
+	// the location of a call. These may be the empty string and
+	// zero, respectively, if not known.
+	File string
+	Line int
+
+	// Entry point program counter for the function; may be zero
+	// if not known. If Func is not nil then Entry ==
+	// Func.Entry().
+	Entry uintptr
+
+	// The runtime's internal view of the function. This field
+	// is set (funcInfo.valid() returns true) only for Go functions,
+	// not for C functions.
+	funcInfo funcInfo
+}
+
+// CallersFrames takes a slice of PC values returned by Callers and
+// prepares to return function/file/line information.
+// Do not change the slice until you are done with the Frames.
+func CallersFrames(callers []uintptr) *Frames {
+	f := &Frames{callers: callers}
+	f.frames = f.frameStore[:0]
+	return f
+}
+
+// Next returns frame information for the next caller.
+// If more is false, there are no more callers (the Frame value is valid).
+func (ci *Frames) Next() (frame Frame, more bool) {
+	for len(ci.frames) < 2 {
+		// Find the next frame.
+		// We need to look for 2 frames so we know what
+		// to return for the "more" result.
+		if len(ci.callers) == 0 {
+			break
+		}
+		pc := ci.callers[0]
+		ci.callers = ci.callers[1:]
+		funcInfo := findfunc(pc)
+		if !funcInfo.valid() {
+			if cgoSymbolizer != nil {
+				// Pre-expand cgo frames. We could do this
+				// incrementally, too, but there's no way to
+				// avoid allocation in this case anyway.
+				ci.frames = append(ci.frames, expandCgoFrames(pc)...)
+			}
+			continue
+		}
+		f := funcInfo._Func()
+		entry := f.Entry()
+		if pc > entry {
+			// We store the pc of the start of the instruction following
+			// the instruction in question (the call or the inline mark).
+			// This is done for historical reasons, and to make FuncForPC
+			// work correctly for entries in the result of runtime.Callers.
+			pc--
+		}
+		name := funcname(funcInfo)
+		if inldata := funcdata(funcInfo, _FUNCDATA_InlTree); inldata != nil {
+			inltree := (*[1 << 20]inlinedCall)(inldata)
+			// Non-strict as cgoTraceback may have added bogus PCs
+			// with a valid funcInfo but invalid PCDATA.
+			ix := pcdatavalue1(funcInfo, _PCDATA_InlTreeIndex, pc, nil, false)
+			if ix >= 0 {
+				// Note: entry is not modified. It always refers to a real frame, not an inlined one.
+				f = nil
+				name = funcnameFromNameoff(funcInfo, inltree[ix].func_)
+				// File/line is already correct.
+				// TODO: remove file/line from InlinedCall?
+			}
+		}
+		ci.frames = append(ci.frames, Frame{
+			PC:       pc,
+			Func:     f,
+			Function: name,
+			Entry:    entry,
+			funcInfo: funcInfo,
+			// Note: File,Line set below
+		})
+	}
+
+	// Pop one frame from the frame list. Keep the rest.
+	// Avoid allocation in the common case, which is 1 or 2 frames.
+	switch len(ci.frames) {
+	case 0: // In the rare case when there are no frames at all, we return Frame{}.
+		return
+	case 1:
+		frame = ci.frames[0]
+		ci.frames = ci.frameStore[:0]
+	case 2:
+		frame = ci.frames[0]
+		ci.frameStore[0] = ci.frames[1]
+		ci.frames = ci.frameStore[:1]
+	default:
+		frame = ci.frames[0]
+		ci.frames = ci.frames[1:]
+	}
+	more = len(ci.frames) > 0
+	if frame.funcInfo.valid() {
+		// Compute file/line just before we need to return it,
+		// as it can be expensive. This avoids computing file/line
+		// for the Frame we find but don't return. See issue 32093.
+		file, line := funcline1(frame.funcInfo, frame.PC, false)
+		frame.File, frame.Line = file, int(line)
+	}
+	return
+}
+
+// runtime_expandFinalInlineFrame expands the final pc in stk to include all
+// "callers" if pc is inline.
+//
+//go:linkname runtime_expandFinalInlineFrame runtime/pprof.runtime_expandFinalInlineFrame
+func runtime_expandFinalInlineFrame(stk []uintptr) []uintptr {
+	if len(stk) == 0 {
+		return stk
+	}
+	pc := stk[len(stk)-1]
+	tracepc := pc - 1
+
+	f := findfunc(tracepc)
+	if !f.valid() {
+		// Not a Go function.
+		return stk
+	}
+
+	inldata := funcdata(f, _FUNCDATA_InlTree)
+	if inldata == nil {
+		// Nothing inline in f.
+		return stk
+	}
+
+	// Treat the previous func as normal. We haven't actually checked, but
+	// since this pc was included in the stack, we know it shouldn't be
+	// elided.
+	lastFuncID := funcID_normal
+
+	// Remove pc from stk; we'll re-add it below.
+	stk = stk[:len(stk)-1]
+
+	// See inline expansion in gentraceback.
+	var cache pcvalueCache
+	inltree := (*[1 << 20]inlinedCall)(inldata)
+	for {
+		// Non-strict as cgoTraceback may have added bogus PCs
+		// with a valid funcInfo but invalid PCDATA.
+		ix := pcdatavalue1(f, _PCDATA_InlTreeIndex, tracepc, &cache, false)
+		if ix < 0 {
+			break
+		}
+		if inltree[ix].funcID == funcID_wrapper && elideWrapperCalling(lastFuncID) {
+			// ignore wrappers
+		} else {
+			stk = append(stk, pc)
+		}
+		lastFuncID = inltree[ix].funcID
+		// Back up to an instruction in the "caller".
+		tracepc = f.entry + uintptr(inltree[ix].parentPc)
+		pc = tracepc + 1
+	}
+
+	// N.B. we want to keep the last parentPC which is not inline.
+	stk = append(stk, pc)
+
+	return stk
+}
+
+// expandCgoFrames expands frame information for pc, known to be
+// a non-Go function, using the cgoSymbolizer hook. expandCgoFrames
+// returns nil if pc could not be expanded.
+func expandCgoFrames(pc uintptr) []Frame {
+	arg := cgoSymbolizerArg{pc: pc}
+	callCgoSymbolizer(&arg)
+
+	if arg.file == nil && arg.funcName == nil {
+		// No useful information from symbolizer.
+		return nil
+	}
+
+	var frames []Frame
+	for {
+		frames = append(frames, Frame{
+			PC:       pc,
+			Func:     nil,
+			Function: gostring(arg.funcName),
+			File:     gostring(arg.file),
+			Line:     int(arg.lineno),
+			Entry:    arg.entry,
+			// funcInfo is zero, which implies !funcInfo.valid().
+			// That ensures that we use the File/Line info given here.
+		})
+		if arg.more == 0 {
+			break
+		}
+		callCgoSymbolizer(&arg)
+	}
+
+	// No more frames for this PC. Tell the symbolizer we are done.
+	// We don't try to maintain a single cgoSymbolizerArg for the
+	// whole use of Frames, because there would be no good way to tell
+	// the symbolizer when we are done.
+	arg.pc = 0
+	callCgoSymbolizer(&arg)
+
+	return frames
+}
+
+// NOTE: Func does not expose the actual unexported fields, because we return *Func
+// values to users, and we want to keep them from being able to overwrite the data
+// with (say) *f = Func{}.
+// All code operating on a *Func must call raw() to get the *_func
+// or funcInfo() to get the funcInfo instead.
+
+// A Func represents a Go function in the running binary.
+type Func struct {
+	opaque struct{} // unexported field to disallow conversions
+}
+
+func (f *Func) raw() *_func {
+	return (*_func)(unsafe.Pointer(f))
+}
+
+func (f *Func) funcInfo() funcInfo {
+	fn := f.raw()
+	return funcInfo{fn, findmoduledatap(fn.entry)}
+}
+
+// PCDATA and FUNCDATA table indexes.
+//
+// See funcdata.h and ../cmd/internal/objabi/funcdata.go.
+const (
+	_PCDATA_UnsafePoint   = 0
+	_PCDATA_StackMapIndex = 1
+	_PCDATA_InlTreeIndex  = 2
+
+	_FUNCDATA_ArgsPointerMaps    = 0
+	_FUNCDATA_LocalsPointerMaps  = 1
+	_FUNCDATA_StackObjects       = 2
+	_FUNCDATA_InlTree            = 3
+	_FUNCDATA_OpenCodedDeferInfo = 4
+
+	_ArgsSizeUnknown = -0x80000000
+)
+
+const (
+	// PCDATA_UnsafePoint values.
+	_PCDATA_UnsafePointSafe   = -1 // Safe for async preemption
+	_PCDATA_UnsafePointUnsafe = -2 // Unsafe for async preemption
+
+	// _PCDATA_Restart1(2) apply on a sequence of instructions, within
+	// which if an async preemption happens, we should back off the PC
+	// to the start of the sequence when resume.
+	// We need two so we can distinguish the start/end of the sequence
+	// in case that two sequences are next to each other.
+	_PCDATA_Restart1 = -3
+	_PCDATA_Restart2 = -4
+
+	// Like _PCDATA_RestartAtEntry, but back to function entry if async
+	// preempted.
+	_PCDATA_RestartAtEntry = -5
+)
+
+// A FuncID identifies particular functions that need to be treated
+// specially by the runtime.
+// Note that in some situations involving plugins, there may be multiple
+// copies of a particular special runtime function.
+// Note: this list must match the list in cmd/internal/objabi/funcid.go.
+type funcID uint8
+
+const (
+	funcID_normal funcID = iota // not a special function
+	funcID_runtime_main
+	funcID_goexit
+	funcID_jmpdefer
+	funcID_mcall
+	funcID_morestack
+	funcID_mstart
+	funcID_rt0_go
+	funcID_asmcgocall
+	funcID_sigpanic
+	funcID_runfinq
+	funcID_gcBgMarkWorker
+	funcID_systemstack_switch
+	funcID_systemstack
+	funcID_cgocallback
+	funcID_gogo
+	funcID_externalthreadhandler
+	funcID_debugCallV1
+	funcID_gopanic
+	funcID_panicwrap
+	funcID_handleAsyncEvent
+	funcID_asyncPreempt
+	funcID_wrapper // any autogenerated code (hash/eq algorithms, method wrappers, etc.)
+)
+
+// pcHeader holds data used by the pclntab lookups.
+type pcHeader struct {
+	magic          uint32  // 0xFFFFFFFA
+	pad1, pad2     uint8   // 0,0
+	minLC          uint8   // min instruction size
+	ptrSize        uint8   // size of a ptr in bytes
+	nfunc          int     // number of functions in the module
+	nfiles         uint    // number of entries in the file tab.
+	funcnameOffset uintptr // offset to the funcnametab variable from pcHeader
+	cuOffset       uintptr // offset to the cutab variable from pcHeader
+	filetabOffset  uintptr // offset to the filetab variable from pcHeader
+	pctabOffset    uintptr // offset to the pctab varible from pcHeader
+	pclnOffset     uintptr // offset to the pclntab variable from pcHeader
+}
+
+// moduledata records information about the layout of the executable
+// image. It is written by the linker. Any changes here must be
+// matched changes to the code in cmd/internal/ld/symtab.go:symtab.
+// moduledata is stored in statically allocated non-pointer memory;
+// none of the pointers here are visible to the garbage collector.
+type moduledata struct {
+	pcHeader     *pcHeader
+	funcnametab  []byte
+	cutab        []uint32
+	filetab      []byte
+	pctab        []byte
+	pclntable    []byte
+	ftab         []functab
+	findfunctab  uintptr
+	minpc, maxpc uintptr
+
+	text, etext           uintptr
+	noptrdata, enoptrdata uintptr
+	data, edata           uintptr
+	bss, ebss             uintptr
+	noptrbss, enoptrbss   uintptr
+	end, gcdata, gcbss    uintptr
+	types, etypes         uintptr
+
+	textsectmap []textsect
+	typelinks   []int32 // offsets from types
+	itablinks   []*itab
+
+	ptab []ptabEntry
+
+	pluginpath string
+	pkghashes  []modulehash
+
+	modulename   string
+	modulehashes []modulehash
+
+	hasmain uint8 // 1 if module contains the main function, 0 otherwise
+
+	gcdatamask, gcbssmask bitvector
+
+	typemap map[typeOff]*_type // offset to *_rtype in previous module
+
+	bad bool // module failed to load and should be ignored
+
+	next *moduledata
+}
+
+// A modulehash is used to compare the ABI of a new module or a
+// package in a new module with the loaded program.
+//
+// For each shared library a module links against, the linker creates an entry in the
+// moduledata.modulehashes slice containing the name of the module, the abi hash seen
+// at link time and a pointer to the runtime abi hash. These are checked in
+// moduledataverify1 below.
+//
+// For each loaded plugin, the pkghashes slice has a modulehash of the
+// newly loaded package that can be used to check the plugin's version of
+// a package against any previously loaded version of the package.
+// This is done in plugin.lastmoduleinit.
+type modulehash struct {
+	modulename   string
+	linktimehash string
+	runtimehash  *string
+}
+
+// pinnedTypemaps are the map[typeOff]*_type from the moduledata objects.
+//
+// These typemap objects are allocated at run time on the heap, but the
+// only direct reference to them is in the moduledata, created by the
+// linker and marked SNOPTRDATA so it is ignored by the GC.
+//
+// To make sure the map isn't collected, we keep a second reference here.
+var pinnedTypemaps []map[typeOff]*_type
+
+var firstmoduledata moduledata  // linker symbol
+var lastmoduledatap *moduledata // linker symbol
+var modulesSlice *[]*moduledata // see activeModules
+
+// activeModules returns a slice of active modules.
+//
+// A module is active once its gcdatamask and gcbssmask have been
+// assembled and it is usable by the GC.
+//
+// This is nosplit/nowritebarrier because it is called by the
+// cgo pointer checking code.
+//go:nosplit
+//go:nowritebarrier
+func activeModules() []*moduledata {
+	p := (*[]*moduledata)(atomic.Loadp(unsafe.Pointer(&modulesSlice)))
+	if p == nil {
+		return nil
+	}
+	return *p
+}
+
+// modulesinit creates the active modules slice out of all loaded modules.
+//
+// When a module is first loaded by the dynamic linker, an .init_array
+// function (written by cmd/link) is invoked to call addmoduledata,
+// appending to the module to the linked list that starts with
+// firstmoduledata.
+//
+// There are two times this can happen in the lifecycle of a Go
+// program. First, if compiled with -linkshared, a number of modules
+// built with -buildmode=shared can be loaded at program initialization.
+// Second, a Go program can load a module while running that was built
+// with -buildmode=plugin.
+//
+// After loading, this function is called which initializes the
+// moduledata so it is usable by the GC and creates a new activeModules
+// list.
+//
+// Only one goroutine may call modulesinit at a time.
+func modulesinit() {
+	modules := new([]*moduledata)
+	for md := &firstmoduledata; md != nil; md = md.next {
+		if md.bad {
+			continue
+		}
+		*modules = append(*modules, md)
+		if md.gcdatamask == (bitvector{}) {
+			md.gcdatamask = progToPointerMask((*byte)(unsafe.Pointer(md.gcdata)), md.edata-md.data)
+			md.gcbssmask = progToPointerMask((*byte)(unsafe.Pointer(md.gcbss)), md.ebss-md.bss)
+		}
+	}
+
+	// Modules appear in the moduledata linked list in the order they are
+	// loaded by the dynamic loader, with one exception: the
+	// firstmoduledata itself the module that contains the runtime. This
+	// is not always the first module (when using -buildmode=shared, it
+	// is typically libstd.so, the second module). The order matters for
+	// typelinksinit, so we swap the first module with whatever module
+	// contains the main function.
+	//
+	// See Issue #18729.
+	for i, md := range *modules {
+		if md.hasmain != 0 {
+			(*modules)[0] = md
+			(*modules)[i] = &firstmoduledata
+			break
+		}
+	}
+
+	atomicstorep(unsafe.Pointer(&modulesSlice), unsafe.Pointer(modules))
+}
+
+type functab struct {
+	entry   uintptr
+	funcoff uintptr
+}
+
+// Mapping information for secondary text sections
+
+type textsect struct {
+	vaddr    uintptr // prelinked section vaddr
+	length   uintptr // section length
+	baseaddr uintptr // relocated section address
+}
+
+const minfunc = 16                 // minimum function size
+const pcbucketsize = 256 * minfunc // size of bucket in the pc->func lookup table
+
+// findfunctab is an array of these structures.
+// Each bucket represents 4096 bytes of the text segment.
+// Each subbucket represents 256 bytes of the text segment.
+// To find a function given a pc, locate the bucket and subbucket for
+// that pc. Add together the idx and subbucket value to obtain a
+// function index. Then scan the functab array starting at that
+// index to find the target function.
+// This table uses 20 bytes for every 4096 bytes of code, or ~0.5% overhead.
+type findfuncbucket struct {
+	idx        uint32
+	subbuckets [16]byte
+}
+
+func moduledataverify() {
+	for datap := &firstmoduledata; datap != nil; datap = datap.next {
+		moduledataverify1(datap)
+	}
+}
+
+const debugPcln = false
+
+func moduledataverify1(datap *moduledata) {
+	// Check that the pclntab's format is valid.
+	hdr := datap.pcHeader
+	if hdr.magic != 0xfffffffa || hdr.pad1 != 0 || hdr.pad2 != 0 || hdr.minLC != sys.PCQuantum || hdr.ptrSize != sys.PtrSize {
+		println("runtime: function symbol table header:", hex(hdr.magic), hex(hdr.pad1), hex(hdr.pad2), hex(hdr.minLC), hex(hdr.ptrSize))
+		throw("invalid function symbol table\n")
+	}
+
+	// ftab is lookup table for function by program counter.
+	nftab := len(datap.ftab) - 1
+	for i := 0; i < nftab; i++ {
+		// NOTE: ftab[nftab].entry is legal; it is the address beyond the final function.
+		if datap.ftab[i].entry > datap.ftab[i+1].entry {
+			f1 := funcInfo{(*_func)(unsafe.Pointer(&datap.pclntable[datap.ftab[i].funcoff])), datap}
+			f2 := funcInfo{(*_func)(unsafe.Pointer(&datap.pclntable[datap.ftab[i+1].funcoff])), datap}
+			f2name := "end"
+			if i+1 < nftab {
+				f2name = funcname(f2)
+			}
+			println("function symbol table not sorted by program counter:", hex(datap.ftab[i].entry), funcname(f1), ">", hex(datap.ftab[i+1].entry), f2name)
+			for j := 0; j <= i; j++ {
+				print("\t", hex(datap.ftab[j].entry), " ", funcname(funcInfo{(*_func)(unsafe.Pointer(&datap.pclntable[datap.ftab[j].funcoff])), datap}), "\n")
+			}
+			if GOOS == "aix" && isarchive {
+				println("-Wl,-bnoobjreorder is mandatory on aix/ppc64 with c-archive")
+			}
+			throw("invalid runtime symbol table")
+		}
+	}
+
+	if datap.minpc != datap.ftab[0].entry ||
+		datap.maxpc != datap.ftab[nftab].entry {
+		throw("minpc or maxpc invalid")
+	}
+
+	for _, modulehash := range datap.modulehashes {
+		if modulehash.linktimehash != *modulehash.runtimehash {
+			println("abi mismatch detected between", datap.modulename, "and", modulehash.modulename)
+			throw("abi mismatch")
+		}
+	}
+}
+
+// FuncForPC returns a *Func describing the function that contains the
+// given program counter address, or else nil.
+//
+// If pc represents multiple functions because of inlining, it returns
+// the *Func describing the innermost function, but with an entry of
+// the outermost function.
+func FuncForPC(pc uintptr) *Func {
+	f := findfunc(pc)
+	if !f.valid() {
+		return nil
+	}
+	if inldata := funcdata(f, _FUNCDATA_InlTree); inldata != nil {
+		// Note: strict=false so bad PCs (those between functions) don't crash the runtime.
+		// We just report the preceding function in that situation. See issue 29735.
+		// TODO: Perhaps we should report no function at all in that case.
+		// The runtime currently doesn't have function end info, alas.
+		if ix := pcdatavalue1(f, _PCDATA_InlTreeIndex, pc, nil, false); ix >= 0 {
+			inltree := (*[1 << 20]inlinedCall)(inldata)
+			name := funcnameFromNameoff(f, inltree[ix].func_)
+			file, line := funcline(f, pc)
+			fi := &funcinl{
+				entry: f.entry, // entry of the real (the outermost) function.
+				name:  name,
+				file:  file,
+				line:  int(line),
+			}
+			return (*Func)(unsafe.Pointer(fi))
+		}
+	}
+	return f._Func()
+}
+
+// Name returns the name of the function.
+func (f *Func) Name() string {
+	if f == nil {
+		return ""
+	}
+	fn := f.raw()
+	if fn.entry == 0 { // inlined version
+		fi := (*funcinl)(unsafe.Pointer(fn))
+		return fi.name
+	}
+	return funcname(f.funcInfo())
+}
+
+// Entry returns the entry address of the function.
+func (f *Func) Entry() uintptr {
+	fn := f.raw()
+	if fn.entry == 0 { // inlined version
+		fi := (*funcinl)(unsafe.Pointer(fn))
+		return fi.entry
+	}
+	return fn.entry
+}
+
+// FileLine returns the file name and line number of the
+// source code corresponding to the program counter pc.
+// The result will not be accurate if pc is not a program
+// counter within f.
+func (f *Func) FileLine(pc uintptr) (file string, line int) {
+	fn := f.raw()
+	if fn.entry == 0 { // inlined version
+		fi := (*funcinl)(unsafe.Pointer(fn))
+		return fi.file, fi.line
+	}
+	// Pass strict=false here, because anyone can call this function,
+	// and they might just be wrong about targetpc belonging to f.
+	file, line32 := funcline1(f.funcInfo(), pc, false)
+	return file, int(line32)
+}
+
+func findmoduledatap(pc uintptr) *moduledata {
+	for datap := &firstmoduledata; datap != nil; datap = datap.next {
+		if datap.minpc <= pc && pc < datap.maxpc {
+			return datap
+		}
+	}
+	return nil
+}
+
+type funcInfo struct {
+	*_func
+	datap *moduledata
+}
+
+func (f funcInfo) valid() bool {
+	return f._func != nil
+}
+
+func (f funcInfo) _Func() *Func {
+	return (*Func)(unsafe.Pointer(f._func))
+}
+
+func findfunc(pc uintptr) funcInfo {
+	datap := findmoduledatap(pc)
+	if datap == nil {
+		return funcInfo{}
+	}
+	const nsub = uintptr(len(findfuncbucket{}.subbuckets))
+
+	x := pc - datap.minpc
+	b := x / pcbucketsize
+	i := x % pcbucketsize / (pcbucketsize / nsub)
+
+	ffb := (*findfuncbucket)(add(unsafe.Pointer(datap.findfunctab), b*unsafe.Sizeof(findfuncbucket{})))
+	idx := ffb.idx + uint32(ffb.subbuckets[i])
+
+	// If the idx is beyond the end of the ftab, set it to the end of the table and search backward.
+	// This situation can occur if multiple text sections are generated to handle large text sections
+	// and the linker has inserted jump tables between them.
+
+	if idx >= uint32(len(datap.ftab)) {
+		idx = uint32(len(datap.ftab) - 1)
+	}
+	if pc < datap.ftab[idx].entry {
+		// With multiple text sections, the idx might reference a function address that
+		// is higher than the pc being searched, so search backward until the matching address is found.
+
+		for datap.ftab[idx].entry > pc && idx > 0 {
+			idx--
+		}
+		if idx == 0 {
+			throw("findfunc: bad findfunctab entry idx")
+		}
+	} else {
+		// linear search to find func with pc >= entry.
+		for datap.ftab[idx+1].entry <= pc {
+			idx++
+		}
+	}
+	funcoff := datap.ftab[idx].funcoff
+	if funcoff == ^uintptr(0) {
+		// With multiple text sections, there may be functions inserted by the external
+		// linker that are not known by Go. This means there may be holes in the PC
+		// range covered by the func table. The invalid funcoff value indicates a hole.
+		// See also cmd/link/internal/ld/pcln.go:pclntab
+		return funcInfo{}
+	}
+	return funcInfo{(*_func)(unsafe.Pointer(&datap.pclntable[funcoff])), datap}
+}
+
+type pcvalueCache struct {
+	entries [2][8]pcvalueCacheEnt
+}
+
+type pcvalueCacheEnt struct {
+	// targetpc and off together are the key of this cache entry.
+	targetpc uintptr
+	off      uint32
+	// val is the value of this cached pcvalue entry.
+	val int32
+}
+
+// pcvalueCacheKey returns the outermost index in a pcvalueCache to use for targetpc.
+// It must be very cheap to calculate.
+// For now, align to sys.PtrSize and reduce mod the number of entries.
+// In practice, this appears to be fairly randomly and evenly distributed.
+func pcvalueCacheKey(targetpc uintptr) uintptr {
+	return (targetpc / sys.PtrSize) % uintptr(len(pcvalueCache{}.entries))
+}
+
+// Returns the PCData value, and the PC where this value starts.
+// TODO: the start PC is returned only when cache is nil.
+func pcvalue(f funcInfo, off uint32, targetpc uintptr, cache *pcvalueCache, strict bool) (int32, uintptr) {
+	if off == 0 {
+		return -1, 0
+	}
+
+	// Check the cache. This speeds up walks of deep stacks, which
+	// tend to have the same recursive functions over and over.
+	//
+	// This cache is small enough that full associativity is
+	// cheaper than doing the hashing for a less associative
+	// cache.
+	if cache != nil {
+		x := pcvalueCacheKey(targetpc)
+		for i := range cache.entries[x] {
+			// We check off first because we're more
+			// likely to have multiple entries with
+			// different offsets for the same targetpc
+			// than the other way around, so we'll usually
+			// fail in the first clause.
+			ent := &cache.entries[x][i]
+			if ent.off == off && ent.targetpc == targetpc {
+				return ent.val, 0
+			}
+		}
+	}
+
+	if !f.valid() {
+		if strict && panicking == 0 {
+			print("runtime: no module data for ", hex(f.entry), "\n")
+			throw("no module data")
+		}
+		return -1, 0
+	}
+	datap := f.datap
+	p := datap.pctab[off:]
+	pc := f.entry
+	prevpc := pc
+	val := int32(-1)
+	for {
+		var ok bool
+		p, ok = step(p, &pc, &val, pc == f.entry)
+		if !ok {
+			break
+		}
+		if targetpc < pc {
+			// Replace a random entry in the cache. Random
+			// replacement prevents a performance cliff if
+			// a recursive stack's cycle is slightly
+			// larger than the cache.
+			// Put the new element at the beginning,
+			// since it is the most likely to be newly used.
+			if cache != nil {
+				x := pcvalueCacheKey(targetpc)
+				e := &cache.entries[x]
+				ci := fastrand() % uint32(len(cache.entries[x]))
+				e[ci] = e[0]
+				e[0] = pcvalueCacheEnt{
+					targetpc: targetpc,
+					off:      off,
+					val:      val,
+				}
+			}
+
+			return val, prevpc
+		}
+		prevpc = pc
+	}
+
+	// If there was a table, it should have covered all program counters.
+	// If not, something is wrong.
+	if panicking != 0 || !strict {
+		return -1, 0
+	}
+
+	print("runtime: invalid pc-encoded table f=", funcname(f), " pc=", hex(pc), " targetpc=", hex(targetpc), " tab=", p, "\n")
+
+	p = datap.pctab[off:]
+	pc = f.entry
+	val = -1
+	for {
+		var ok bool
+		p, ok = step(p, &pc, &val, pc == f.entry)
+		if !ok {
+			break
+		}
+		print("\tvalue=", val, " until pc=", hex(pc), "\n")
+	}
+
+	throw("invalid runtime symbol table")
+	return -1, 0
+}
+
+func cfuncname(f funcInfo) *byte {
+	if !f.valid() || f.nameoff == 0 {
+		return nil
+	}
+	return &f.datap.funcnametab[f.nameoff]
+}
+
+func funcname(f funcInfo) string {
+	return gostringnocopy(cfuncname(f))
+}
+
+func funcpkgpath(f funcInfo) string {
+	name := funcname(f)
+	i := len(name) - 1
+	for ; i > 0; i-- {
+		if name[i] == '/' {
+			break
+		}
+	}
+	for ; i < len(name); i++ {
+		if name[i] == '.' {
+			break
+		}
+	}
+	return name[:i]
+}
+
+func cfuncnameFromNameoff(f funcInfo, nameoff int32) *byte {
+	if !f.valid() {
+		return nil
+	}
+	return &f.datap.funcnametab[nameoff]
+}
+
+func funcnameFromNameoff(f funcInfo, nameoff int32) string {
+	return gostringnocopy(cfuncnameFromNameoff(f, nameoff))
+}
+
+func funcfile(f funcInfo, fileno int32) string {
+	datap := f.datap
+	if !f.valid() {
+		return "?"
+	}
+	// Make sure the cu index and file offset are valid
+	if fileoff := datap.cutab[f.cuOffset+uint32(fileno)]; fileoff != ^uint32(0) {
+		return gostringnocopy(&datap.filetab[fileoff])
+	}
+	// pcln section is corrupt.
+	return "?"
+}
+
+func funcline1(f funcInfo, targetpc uintptr, strict bool) (file string, line int32) {
+	datap := f.datap
+	if !f.valid() {
+		return "?", 0
+	}
+	fileno, _ := pcvalue(f, f.pcfile, targetpc, nil, strict)
+	line, _ = pcvalue(f, f.pcln, targetpc, nil, strict)
+	if fileno == -1 || line == -1 || int(fileno) >= len(datap.filetab) {
+		// print("looking for ", hex(targetpc), " in ", funcname(f), " got file=", fileno, " line=", lineno, "\n")
+		return "?", 0
+	}
+	file = funcfile(f, fileno)
+	return
+}
+
+func funcline(f funcInfo, targetpc uintptr) (file string, line int32) {
+	return funcline1(f, targetpc, true)
+}
+
+func funcspdelta(f funcInfo, targetpc uintptr, cache *pcvalueCache) int32 {
+	x, _ := pcvalue(f, f.pcsp, targetpc, cache, true)
+	if x&(sys.PtrSize-1) != 0 {
+		print("invalid spdelta ", funcname(f), " ", hex(f.entry), " ", hex(targetpc), " ", hex(f.pcsp), " ", x, "\n")
+	}
+	return x
+}
+
+// funcMaxSPDelta returns the maximum spdelta at any point in f.
+func funcMaxSPDelta(f funcInfo) int32 {
+	datap := f.datap
+	p := datap.pctab[f.pcsp:]
+	pc := f.entry
+	val := int32(-1)
+	max := int32(0)
+	for {
+		var ok bool
+		p, ok = step(p, &pc, &val, pc == f.entry)
+		if !ok {
+			return max
+		}
+		if val > max {
+			max = val
+		}
+	}
+}
+
+func pcdatastart(f funcInfo, table uint32) uint32 {
+	return *(*uint32)(add(unsafe.Pointer(&f.nfuncdata), unsafe.Sizeof(f.nfuncdata)+uintptr(table)*4))
+}
+
+func pcdatavalue(f funcInfo, table uint32, targetpc uintptr, cache *pcvalueCache) int32 {
+	if table >= f.npcdata {
+		return -1
+	}
+	r, _ := pcvalue(f, pcdatastart(f, table), targetpc, cache, true)
+	return r
+}
+
+func pcdatavalue1(f funcInfo, table uint32, targetpc uintptr, cache *pcvalueCache, strict bool) int32 {
+	if table >= f.npcdata {
+		return -1
+	}
+	r, _ := pcvalue(f, pcdatastart(f, table), targetpc, cache, strict)
+	return r
+}
+
+// Like pcdatavalue, but also return the start PC of this PCData value.
+// It doesn't take a cache.
+func pcdatavalue2(f funcInfo, table uint32, targetpc uintptr) (int32, uintptr) {
+	if table >= f.npcdata {
+		return -1, 0
+	}
+	return pcvalue(f, pcdatastart(f, table), targetpc, nil, true)
+}
+
+func funcdata(f funcInfo, i uint8) unsafe.Pointer {
+	if i < 0 || i >= f.nfuncdata {
+		return nil
+	}
+	p := add(unsafe.Pointer(&f.nfuncdata), unsafe.Sizeof(f.nfuncdata)+uintptr(f.npcdata)*4)
+	if sys.PtrSize == 8 && uintptr(p)&4 != 0 {
+		if uintptr(unsafe.Pointer(f._func))&4 != 0 {
+			println("runtime: misaligned func", f._func)
+		}
+		p = add(p, 4)
+	}
+	return *(*unsafe.Pointer)(add(p, uintptr(i)*sys.PtrSize))
+}
+
+// step advances to the next pc, value pair in the encoded table.
+func step(p []byte, pc *uintptr, val *int32, first bool) (newp []byte, ok bool) {
+	// For both uvdelta and pcdelta, the common case (~70%)
+	// is that they are a single byte. If so, avoid calling readvarint.
+	uvdelta := uint32(p[0])
+	if uvdelta == 0 && !first {
+		return nil, false
+	}
+	n := uint32(1)
+	if uvdelta&0x80 != 0 {
+		n, uvdelta = readvarint(p)
+	}
+	*val += int32(-(uvdelta & 1) ^ (uvdelta >> 1))
+	p = p[n:]
+
+	pcdelta := uint32(p[0])
+	n = 1
+	if pcdelta&0x80 != 0 {
+		n, pcdelta = readvarint(p)
+	}
+	p = p[n:]
+	*pc += uintptr(pcdelta * sys.PCQuantum)
+	return p, true
+}
+
+// readvarint reads a varint from p.
+func readvarint(p []byte) (read uint32, val uint32) {
+	var v, shift, n uint32
+	for {
+		b := p[n]
+		n++
+		v |= uint32(b&0x7F) << (shift & 31)
+		if b&0x80 == 0 {
+			break
+		}
+		shift += 7
+	}
+	return n, v
+}
+
+type stackmap struct {
+	n        int32   // number of bitmaps
+	nbit     int32   // number of bits in each bitmap
+	bytedata [1]byte // bitmaps, each starting on a byte boundary
+}
+
+//go:nowritebarrier
+func stackmapdata(stkmap *stackmap, n int32) bitvector {
+	// Check this invariant only when stackDebug is on at all.
+	// The invariant is already checked by many of stackmapdata's callers,
+	// and disabling it by default allows stackmapdata to be inlined.
+	if stackDebug > 0 && (n < 0 || n >= stkmap.n) {
+		throw("stackmapdata: index out of range")
+	}
+	return bitvector{stkmap.nbit, addb(&stkmap.bytedata[0], uintptr(n*((stkmap.nbit+7)>>3)))}
+}
+
+// inlinedCall is the encoding of entries in the FUNCDATA_InlTree table.
+type inlinedCall struct {
+	parent   int16  // index of parent in the inltree, or < 0
+	funcID   funcID // type of the called function
+	_        byte
+	file     int32 // perCU file index for inlined call. See cmd/link:pcln.go
+	line     int32 // line number of the call site
+	func_    int32 // offset into pclntab for name of called function
+	parentPc int32 // position of an instruction whose source position is the call site (offset from entry)
+}