Current File : //usr/local/go119/src/cmd/link/internal/ld/pcln.go
// Copyright 2013 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 ld
import (
"cmd/internal/goobj"
"cmd/internal/objabi"
"cmd/internal/sys"
"cmd/link/internal/loader"
"cmd/link/internal/sym"
"fmt"
"internal/buildcfg"
"os"
"path/filepath"
"strings"
)
const funcSize = 10 * 4 // funcSize is the size of the _func object in runtime/runtime2.go
// pclntab holds the state needed for pclntab generation.
type pclntab struct {
// The first and last functions found.
firstFunc, lastFunc loader.Sym
// Running total size of pclntab.
size int64
// runtime.pclntab's symbols
carrier loader.Sym
pclntab loader.Sym
pcheader loader.Sym
funcnametab loader.Sym
findfunctab loader.Sym
cutab loader.Sym
filetab loader.Sym
pctab loader.Sym
// The number of functions + number of TEXT sections - 1. This is such an
// unexpected value because platforms that have more than one TEXT section
// get a dummy function inserted between because the external linker can place
// functions in those areas. We mark those areas as not covered by the Go
// runtime.
//
// On most platforms this is the number of reachable functions.
nfunc int32
// The number of filenames in runtime.filetab.
nfiles uint32
}
// addGeneratedSym adds a generator symbol to pclntab, returning the new Sym.
// It is the caller's responsibility to save the symbol in state.
func (state *pclntab) addGeneratedSym(ctxt *Link, name string, size int64, f generatorFunc) loader.Sym {
size = Rnd(size, int64(ctxt.Arch.PtrSize))
state.size += size
s := ctxt.createGeneratorSymbol(name, 0, sym.SPCLNTAB, size, f)
ctxt.loader.SetAttrReachable(s, true)
ctxt.loader.SetCarrierSym(s, state.carrier)
ctxt.loader.SetAttrNotInSymbolTable(s, true)
return s
}
// makePclntab makes a pclntab object, and assembles all the compilation units
// we'll need to write pclntab. Returns the pclntab structure, a slice of the
// CompilationUnits we need, and a slice of the function symbols we need to
// generate pclntab.
func makePclntab(ctxt *Link, container loader.Bitmap) (*pclntab, []*sym.CompilationUnit, []loader.Sym) {
ldr := ctxt.loader
state := new(pclntab)
// Gather some basic stats and info.
seenCUs := make(map[*sym.CompilationUnit]struct{})
compUnits := []*sym.CompilationUnit{}
funcs := []loader.Sym{}
for _, s := range ctxt.Textp {
if !emitPcln(ctxt, s, container) {
continue
}
funcs = append(funcs, s)
state.nfunc++
if state.firstFunc == 0 {
state.firstFunc = s
}
state.lastFunc = s
// We need to keep track of all compilation units we see. Some symbols
// (eg, go.buildid, _cgoexp_, etc) won't have a compilation unit.
cu := ldr.SymUnit(s)
if _, ok := seenCUs[cu]; cu != nil && !ok {
seenCUs[cu] = struct{}{}
cu.PclnIndex = len(compUnits)
compUnits = append(compUnits, cu)
}
}
return state, compUnits, funcs
}
func emitPcln(ctxt *Link, s loader.Sym, container loader.Bitmap) bool {
// We want to generate func table entries only for the "lowest
// level" symbols, not containers of subsymbols.
return !container.Has(s)
}
func computeDeferReturn(ctxt *Link, deferReturnSym, s loader.Sym) uint32 {
ldr := ctxt.loader
target := ctxt.Target
deferreturn := uint32(0)
lastWasmAddr := uint32(0)
relocs := ldr.Relocs(s)
for ri := 0; ri < relocs.Count(); ri++ {
r := relocs.At(ri)
if target.IsWasm() && r.Type() == objabi.R_ADDR {
// wasm/ssa.go generates an ARESUMEPOINT just
// before the deferreturn call. The "PC" of
// the deferreturn call is stored in the
// R_ADDR relocation on the ARESUMEPOINT.
lastWasmAddr = uint32(r.Add())
}
if r.Type().IsDirectCall() && (r.Sym() == deferReturnSym || ldr.IsDeferReturnTramp(r.Sym())) {
if target.IsWasm() {
deferreturn = lastWasmAddr - 1
} else {
// Note: the relocation target is in the call instruction, but
// is not necessarily the whole instruction (for instance, on
// x86 the relocation applies to bytes [1:5] of the 5 byte call
// instruction).
deferreturn = uint32(r.Off())
switch target.Arch.Family {
case sys.AMD64, sys.I386:
deferreturn--
case sys.ARM, sys.ARM64, sys.Loong64, sys.MIPS, sys.MIPS64, sys.PPC64, sys.RISCV64:
// no change
case sys.S390X:
deferreturn -= 2
default:
panic(fmt.Sprint("Unhandled architecture:", target.Arch.Family))
}
}
break // only need one
}
}
return deferreturn
}
// genInlTreeSym generates the InlTree sym for a function with the
// specified FuncInfo.
func genInlTreeSym(ctxt *Link, cu *sym.CompilationUnit, fi loader.FuncInfo, arch *sys.Arch, nameOffsets map[loader.Sym]uint32) loader.Sym {
ldr := ctxt.loader
its := ldr.CreateExtSym("", 0)
inlTreeSym := ldr.MakeSymbolUpdater(its)
// Note: the generated symbol is given a type of sym.SGOFUNC, as a
// signal to the symtab() phase that it needs to be grouped in with
// other similar symbols (gcdata, etc); the dodata() phase will
// eventually switch the type back to SRODATA.
inlTreeSym.SetType(sym.SGOFUNC)
ldr.SetAttrReachable(its, true)
ldr.SetSymAlign(its, 4) // it has 32-bit fields
ninl := fi.NumInlTree()
for i := 0; i < int(ninl); i++ {
call := fi.InlTree(i)
val := call.File
nameoff, ok := nameOffsets[call.Func]
if !ok {
panic("couldn't find function name offset")
}
inlTreeSym.SetUint16(arch, int64(i*20+0), uint16(call.Parent))
inlFunc := ldr.FuncInfo(call.Func)
var funcID objabi.FuncID
if inlFunc.Valid() {
funcID = inlFunc.FuncID()
}
inlTreeSym.SetUint8(arch, int64(i*20+2), uint8(funcID))
// byte 3 is unused
inlTreeSym.SetUint32(arch, int64(i*20+4), uint32(val))
inlTreeSym.SetUint32(arch, int64(i*20+8), uint32(call.Line))
inlTreeSym.SetUint32(arch, int64(i*20+12), uint32(nameoff))
inlTreeSym.SetUint32(arch, int64(i*20+16), uint32(call.ParentPC))
}
return its
}
// makeInlSyms returns a map of loader.Sym that are created inlSyms.
func makeInlSyms(ctxt *Link, funcs []loader.Sym, nameOffsets map[loader.Sym]uint32) map[loader.Sym]loader.Sym {
ldr := ctxt.loader
// Create the inline symbols we need.
inlSyms := make(map[loader.Sym]loader.Sym)
for _, s := range funcs {
if fi := ldr.FuncInfo(s); fi.Valid() {
fi.Preload()
if fi.NumInlTree() > 0 {
inlSyms[s] = genInlTreeSym(ctxt, ldr.SymUnit(s), fi, ctxt.Arch, nameOffsets)
}
}
}
return inlSyms
}
// generatePCHeader creates the runtime.pcheader symbol, setting it up as a
// generator to fill in its data later.
func (state *pclntab) generatePCHeader(ctxt *Link) {
ldr := ctxt.loader
textStartOff := int64(8 + 2*ctxt.Arch.PtrSize)
size := int64(8 + 8*ctxt.Arch.PtrSize)
writeHeader := func(ctxt *Link, s loader.Sym) {
header := ctxt.loader.MakeSymbolUpdater(s)
writeSymOffset := func(off int64, ws loader.Sym) int64 {
diff := ldr.SymValue(ws) - ldr.SymValue(s)
if diff <= 0 {
name := ldr.SymName(ws)
panic(fmt.Sprintf("expected runtime.pcheader(%x) to be placed before %s(%x)", ldr.SymValue(s), name, ldr.SymValue(ws)))
}
return header.SetUintptr(ctxt.Arch, off, uintptr(diff))
}
// Write header.
// Keep in sync with runtime/symtab.go:pcHeader and package debug/gosym.
header.SetUint32(ctxt.Arch, 0, 0xfffffff0)
header.SetUint8(ctxt.Arch, 6, uint8(ctxt.Arch.MinLC))
header.SetUint8(ctxt.Arch, 7, uint8(ctxt.Arch.PtrSize))
off := header.SetUint(ctxt.Arch, 8, uint64(state.nfunc))
off = header.SetUint(ctxt.Arch, off, uint64(state.nfiles))
if off != textStartOff {
panic(fmt.Sprintf("pcHeader textStartOff: %d != %d", off, textStartOff))
}
off += int64(ctxt.Arch.PtrSize) // skip runtimeText relocation
off = writeSymOffset(off, state.funcnametab)
off = writeSymOffset(off, state.cutab)
off = writeSymOffset(off, state.filetab)
off = writeSymOffset(off, state.pctab)
off = writeSymOffset(off, state.pclntab)
if off != size {
panic(fmt.Sprintf("pcHeader size: %d != %d", off, size))
}
}
state.pcheader = state.addGeneratedSym(ctxt, "runtime.pcheader", size, writeHeader)
// Create the runtimeText relocation.
sb := ldr.MakeSymbolUpdater(state.pcheader)
sb.SetAddr(ctxt.Arch, textStartOff, ldr.Lookup("runtime.text", 0))
}
// walkFuncs iterates over the funcs, calling a function for each unique
// function and inlined function.
func walkFuncs(ctxt *Link, funcs []loader.Sym, f func(loader.Sym)) {
ldr := ctxt.loader
seen := make(map[loader.Sym]struct{})
for _, s := range funcs {
if _, ok := seen[s]; !ok {
f(s)
seen[s] = struct{}{}
}
fi := ldr.FuncInfo(s)
if !fi.Valid() {
continue
}
fi.Preload()
for i, ni := 0, fi.NumInlTree(); i < int(ni); i++ {
call := fi.InlTree(i).Func
if _, ok := seen[call]; !ok {
f(call)
seen[call] = struct{}{}
}
}
}
}
// generateFuncnametab creates the function name table. Returns a map of
// func symbol to the name offset in runtime.funcnamtab.
func (state *pclntab) generateFuncnametab(ctxt *Link, funcs []loader.Sym) map[loader.Sym]uint32 {
nameOffsets := make(map[loader.Sym]uint32, state.nfunc)
// The name used by the runtime is the concatenation of the 3 returned strings.
// For regular functions, only one returned string is nonempty.
// For generic functions, we use three parts so that we can print everything
// within the outermost "[]" as "...".
nameParts := func(name string) (string, string, string) {
i := strings.IndexByte(name, '[')
if i < 0 {
return name, "", ""
}
// TODO: use LastIndexByte once the bootstrap compiler is >= Go 1.5.
j := len(name) - 1
for j > i && name[j] != ']' {
j--
}
if j <= i {
return name, "", ""
}
return name[:i], "[...]", name[j+1:]
}
// Write the null terminated strings.
writeFuncNameTab := func(ctxt *Link, s loader.Sym) {
symtab := ctxt.loader.MakeSymbolUpdater(s)
for s, off := range nameOffsets {
a, b, c := nameParts(ctxt.loader.SymName(s))
o := int64(off)
o = symtab.AddStringAt(o, a)
o = symtab.AddStringAt(o, b)
_ = symtab.AddCStringAt(o, c)
}
}
// Loop through the CUs, and calculate the size needed.
var size int64
walkFuncs(ctxt, funcs, func(s loader.Sym) {
nameOffsets[s] = uint32(size)
a, b, c := nameParts(ctxt.loader.SymName(s))
size += int64(len(a) + len(b) + len(c) + 1) // NULL terminate
})
state.funcnametab = state.addGeneratedSym(ctxt, "runtime.funcnametab", size, writeFuncNameTab)
return nameOffsets
}
// walkFilenames walks funcs, calling a function for each filename used in each
// function's line table.
func walkFilenames(ctxt *Link, funcs []loader.Sym, f func(*sym.CompilationUnit, goobj.CUFileIndex)) {
ldr := ctxt.loader
// Loop through all functions, finding the filenames we need.
for _, s := range funcs {
fi := ldr.FuncInfo(s)
if !fi.Valid() {
continue
}
fi.Preload()
cu := ldr.SymUnit(s)
for i, nf := 0, int(fi.NumFile()); i < nf; i++ {
f(cu, fi.File(i))
}
for i, ninl := 0, int(fi.NumInlTree()); i < ninl; i++ {
call := fi.InlTree(i)
f(cu, call.File)
}
}
}
// generateFilenameTabs creates LUTs needed for filename lookup. Returns a slice
// of the index at which each CU begins in runtime.cutab.
//
// Function objects keep track of the files they reference to print the stack.
// This function creates a per-CU list of filenames if CU[M] references
// files[1-N], the following is generated:
//
// runtime.cutab:
// CU[M]
// offsetToFilename[0]
// offsetToFilename[1]
// ..
//
// runtime.filetab
// filename[0]
// filename[1]
//
// Looking up a filename then becomes:
// 0. Given a func, and filename index [K]
// 1. Get Func.CUIndex: M := func.cuOffset
// 2. Find filename offset: fileOffset := runtime.cutab[M+K]
// 3. Get the filename: getcstring(runtime.filetab[fileOffset])
func (state *pclntab) generateFilenameTabs(ctxt *Link, compUnits []*sym.CompilationUnit, funcs []loader.Sym) []uint32 {
// On a per-CU basis, keep track of all the filenames we need.
//
// Note, that we store the filenames in a separate section in the object
// files, and deduplicate based on the actual value. It would be better to
// store the filenames as symbols, using content addressable symbols (and
// then not loading extra filenames), and just use the hash value of the
// symbol name to do this cataloging.
//
// TODO: Store filenames as symbols. (Note this would be easiest if you
// also move strings to ALWAYS using the larger content addressable hash
// function, and use that hash value for uniqueness testing.)
cuEntries := make([]goobj.CUFileIndex, len(compUnits))
fileOffsets := make(map[string]uint32)
// Walk the filenames.
// We store the total filename string length we need to load, and the max
// file index we've seen per CU so we can calculate how large the
// CU->global table needs to be.
var fileSize int64
walkFilenames(ctxt, funcs, func(cu *sym.CompilationUnit, i goobj.CUFileIndex) {
// Note we use the raw filename for lookup, but use the expanded filename
// when we save the size.
filename := cu.FileTable[i]
if _, ok := fileOffsets[filename]; !ok {
fileOffsets[filename] = uint32(fileSize)
fileSize += int64(len(expandFile(filename)) + 1) // NULL terminate
}
// Find the maximum file index we've seen.
if cuEntries[cu.PclnIndex] < i+1 {
cuEntries[cu.PclnIndex] = i + 1 // Store max + 1
}
})
// Calculate the size of the runtime.cutab variable.
var totalEntries uint32
cuOffsets := make([]uint32, len(cuEntries))
for i, entries := range cuEntries {
// Note, cutab is a slice of uint32, so an offset to a cu's entry is just the
// running total of all cu indices we've needed to store so far, not the
// number of bytes we've stored so far.
cuOffsets[i] = totalEntries
totalEntries += uint32(entries)
}
// Write cutab.
writeCutab := func(ctxt *Link, s loader.Sym) {
sb := ctxt.loader.MakeSymbolUpdater(s)
var off int64
for i, max := range cuEntries {
// Write the per CU LUT.
cu := compUnits[i]
for j := goobj.CUFileIndex(0); j < max; j++ {
fileOffset, ok := fileOffsets[cu.FileTable[j]]
if !ok {
// We're looping through all possible file indices. It's possible a file's
// been deadcode eliminated, and although it's a valid file in the CU, it's
// not needed in this binary. When that happens, use an invalid offset.
fileOffset = ^uint32(0)
}
off = sb.SetUint32(ctxt.Arch, off, fileOffset)
}
}
}
state.cutab = state.addGeneratedSym(ctxt, "runtime.cutab", int64(totalEntries*4), writeCutab)
// Write filetab.
writeFiletab := func(ctxt *Link, s loader.Sym) {
sb := ctxt.loader.MakeSymbolUpdater(s)
// Write the strings.
for filename, loc := range fileOffsets {
sb.AddStringAt(int64(loc), expandFile(filename))
}
}
state.nfiles = uint32(len(fileOffsets))
state.filetab = state.addGeneratedSym(ctxt, "runtime.filetab", fileSize, writeFiletab)
return cuOffsets
}
// generatePctab creates the runtime.pctab variable, holding all the
// deduplicated pcdata.
func (state *pclntab) generatePctab(ctxt *Link, funcs []loader.Sym) {
ldr := ctxt.loader
// Pctab offsets of 0 are considered invalid in the runtime. We respect
// that by just padding a single byte at the beginning of runtime.pctab,
// that way no real offsets can be zero.
size := int64(1)
// Walk the functions, finding offset to store each pcdata.
seen := make(map[loader.Sym]struct{})
saveOffset := func(pcSym loader.Sym) {
if _, ok := seen[pcSym]; !ok {
datSize := ldr.SymSize(pcSym)
if datSize != 0 {
ldr.SetSymValue(pcSym, size)
} else {
// Invalid PC data, record as zero.
ldr.SetSymValue(pcSym, 0)
}
size += datSize
seen[pcSym] = struct{}{}
}
}
var pcsp, pcline, pcfile, pcinline loader.Sym
var pcdata []loader.Sym
for _, s := range funcs {
fi := ldr.FuncInfo(s)
if !fi.Valid() {
continue
}
fi.Preload()
pcsp, pcfile, pcline, pcinline, pcdata = ldr.PcdataAuxs(s, pcdata)
pcSyms := []loader.Sym{pcsp, pcfile, pcline}
for _, pcSym := range pcSyms {
saveOffset(pcSym)
}
for _, pcSym := range pcdata {
saveOffset(pcSym)
}
if fi.NumInlTree() > 0 {
saveOffset(pcinline)
}
}
// TODO: There is no reason we need a generator for this variable, and it
// could be moved to a carrier symbol. However, carrier symbols containing
// carrier symbols don't work yet (as of Aug 2020). Once this is fixed,
// runtime.pctab could just be a carrier sym.
writePctab := func(ctxt *Link, s loader.Sym) {
ldr := ctxt.loader
sb := ldr.MakeSymbolUpdater(s)
for sym := range seen {
sb.SetBytesAt(ldr.SymValue(sym), ldr.Data(sym))
}
}
state.pctab = state.addGeneratedSym(ctxt, "runtime.pctab", size, writePctab)
}
// numPCData returns the number of PCData syms for the FuncInfo.
// NB: Preload must be called on valid FuncInfos before calling this function.
func numPCData(ldr *loader.Loader, s loader.Sym, fi loader.FuncInfo) uint32 {
if !fi.Valid() {
return 0
}
numPCData := uint32(ldr.NumPcdata(s))
if fi.NumInlTree() > 0 {
if numPCData < objabi.PCDATA_InlTreeIndex+1 {
numPCData = objabi.PCDATA_InlTreeIndex + 1
}
}
return numPCData
}
// generateFunctab creates the runtime.functab
//
// runtime.functab contains two things:
//
// - pc->func look up table.
// - array of func objects, interleaved with pcdata and funcdata
func (state *pclntab) generateFunctab(ctxt *Link, funcs []loader.Sym, inlSyms map[loader.Sym]loader.Sym, cuOffsets []uint32, nameOffsets map[loader.Sym]uint32) {
// Calculate the size of the table.
size, startLocations := state.calculateFunctabSize(ctxt, funcs)
writePcln := func(ctxt *Link, s loader.Sym) {
ldr := ctxt.loader
sb := ldr.MakeSymbolUpdater(s)
// Write the data.
writePCToFunc(ctxt, sb, funcs, startLocations)
writeFuncs(ctxt, sb, funcs, inlSyms, startLocations, cuOffsets, nameOffsets)
}
state.pclntab = state.addGeneratedSym(ctxt, "runtime.functab", size, writePcln)
}
// funcData returns the funcdata and offsets for the FuncInfo.
// The funcdata are written into runtime.functab after each func
// object. This is a helper function to make querying the FuncInfo object
// cleaner.
//
// NB: Preload must be called on the FuncInfo before calling.
// NB: fdSyms is used as scratch space.
func funcData(ldr *loader.Loader, s loader.Sym, fi loader.FuncInfo, inlSym loader.Sym, fdSyms []loader.Sym) []loader.Sym {
fdSyms = fdSyms[:0]
if fi.Valid() {
fdSyms = ldr.Funcdata(s, fdSyms)
if fi.NumInlTree() > 0 {
if len(fdSyms) < objabi.FUNCDATA_InlTree+1 {
fdSyms = append(fdSyms, make([]loader.Sym, objabi.FUNCDATA_InlTree+1-len(fdSyms))...)
}
fdSyms[objabi.FUNCDATA_InlTree] = inlSym
}
}
return fdSyms
}
// calculateFunctabSize calculates the size of the pclntab, and the offsets in
// the output buffer for individual func entries.
func (state pclntab) calculateFunctabSize(ctxt *Link, funcs []loader.Sym) (int64, []uint32) {
ldr := ctxt.loader
startLocations := make([]uint32, len(funcs))
// Allocate space for the pc->func table. This structure consists of a pc offset
// and an offset to the func structure. After that, we have a single pc
// value that marks the end of the last function in the binary.
size := int64(int(state.nfunc)*2*4 + 4)
// Now find the space for the func objects. We do this in a running manner,
// so that we can find individual starting locations.
for i, s := range funcs {
size = Rnd(size, int64(ctxt.Arch.PtrSize))
startLocations[i] = uint32(size)
fi := ldr.FuncInfo(s)
size += funcSize
if fi.Valid() {
fi.Preload()
numFuncData := ldr.NumFuncdata(s)
if fi.NumInlTree() > 0 {
if numFuncData < objabi.FUNCDATA_InlTree+1 {
numFuncData = objabi.FUNCDATA_InlTree + 1
}
}
size += int64(numPCData(ldr, s, fi) * 4)
size += int64(numFuncData * 4)
}
}
return size, startLocations
}
// writePCToFunc writes the PC->func lookup table.
func writePCToFunc(ctxt *Link, sb *loader.SymbolBuilder, funcs []loader.Sym, startLocations []uint32) {
ldr := ctxt.loader
textStart := ldr.SymValue(ldr.Lookup("runtime.text", 0))
pcOff := func(s loader.Sym) uint32 {
off := ldr.SymValue(s) - textStart
if off < 0 {
panic(fmt.Sprintf("expected func %s(%x) to be placed at or after textStart (%x)", ldr.SymName(s), ldr.SymValue(s), textStart))
}
return uint32(off)
}
for i, s := range funcs {
sb.SetUint32(ctxt.Arch, int64(i*2*4), pcOff(s))
sb.SetUint32(ctxt.Arch, int64((i*2+1)*4), startLocations[i])
}
// Final entry of table is just end pc offset.
lastFunc := funcs[len(funcs)-1]
sb.SetUint32(ctxt.Arch, int64(len(funcs))*2*4, pcOff(lastFunc)+uint32(ldr.SymSize(lastFunc)))
}
// writeFuncs writes the func structures and pcdata to runtime.functab.
func writeFuncs(ctxt *Link, sb *loader.SymbolBuilder, funcs []loader.Sym, inlSyms map[loader.Sym]loader.Sym, startLocations, cuOffsets []uint32, nameOffsets map[loader.Sym]uint32) {
ldr := ctxt.loader
deferReturnSym := ldr.Lookup("runtime.deferreturn", abiInternalVer)
gofunc := ldr.Lookup("go.func.*", 0)
gofuncBase := ldr.SymValue(gofunc)
textStart := ldr.SymValue(ldr.Lookup("runtime.text", 0))
funcdata := []loader.Sym{}
var pcsp, pcfile, pcline, pcinline loader.Sym
var pcdata []loader.Sym
// Write the individual func objects.
for i, s := range funcs {
fi := ldr.FuncInfo(s)
if fi.Valid() {
fi.Preload()
pcsp, pcfile, pcline, pcinline, pcdata = ldr.PcdataAuxs(s, pcdata)
}
off := int64(startLocations[i])
// entry uintptr (offset of func entry PC from textStart)
entryOff := ldr.SymValue(s) - textStart
if entryOff < 0 {
panic(fmt.Sprintf("expected func %s(%x) to be placed before or at textStart (%x)", ldr.SymName(s), ldr.SymValue(s), textStart))
}
off = sb.SetUint32(ctxt.Arch, off, uint32(entryOff))
// name int32
nameoff, ok := nameOffsets[s]
if !ok {
panic("couldn't find function name offset")
}
off = sb.SetUint32(ctxt.Arch, off, uint32(nameoff))
// args int32
// TODO: Move into funcinfo.
args := uint32(0)
if fi.Valid() {
args = uint32(fi.Args())
}
off = sb.SetUint32(ctxt.Arch, off, args)
// deferreturn
deferreturn := computeDeferReturn(ctxt, deferReturnSym, s)
off = sb.SetUint32(ctxt.Arch, off, deferreturn)
// pcdata
if fi.Valid() {
off = sb.SetUint32(ctxt.Arch, off, uint32(ldr.SymValue(pcsp)))
off = sb.SetUint32(ctxt.Arch, off, uint32(ldr.SymValue(pcfile)))
off = sb.SetUint32(ctxt.Arch, off, uint32(ldr.SymValue(pcline)))
} else {
off += 12
}
off = sb.SetUint32(ctxt.Arch, off, uint32(numPCData(ldr, s, fi)))
// Store the offset to compilation unit's file table.
cuIdx := ^uint32(0)
if cu := ldr.SymUnit(s); cu != nil {
cuIdx = cuOffsets[cu.PclnIndex]
}
off = sb.SetUint32(ctxt.Arch, off, cuIdx)
// funcID uint8
var funcID objabi.FuncID
if fi.Valid() {
funcID = fi.FuncID()
}
off = sb.SetUint8(ctxt.Arch, off, uint8(funcID))
// flag uint8
var flag objabi.FuncFlag
if fi.Valid() {
flag = fi.FuncFlag()
}
off = sb.SetUint8(ctxt.Arch, off, uint8(flag))
off += 1 // pad
// nfuncdata must be the final entry.
funcdata = funcData(ldr, s, fi, 0, funcdata)
off = sb.SetUint8(ctxt.Arch, off, uint8(len(funcdata)))
// Output the pcdata.
if fi.Valid() {
for j, pcSym := range pcdata {
sb.SetUint32(ctxt.Arch, off+int64(j*4), uint32(ldr.SymValue(pcSym)))
}
if fi.NumInlTree() > 0 {
sb.SetUint32(ctxt.Arch, off+objabi.PCDATA_InlTreeIndex*4, uint32(ldr.SymValue(pcinline)))
}
}
// Write funcdata refs as offsets from go.func.* and go.funcrel.*.
funcdata = funcData(ldr, s, fi, inlSyms[s], funcdata)
// Missing funcdata will be ^0. See runtime/symtab.go:funcdata.
off = int64(startLocations[i] + funcSize + numPCData(ldr, s, fi)*4)
for j := range funcdata {
dataoff := off + int64(4*j)
fdsym := funcdata[j]
if fdsym == 0 {
sb.SetUint32(ctxt.Arch, dataoff, ^uint32(0)) // ^0 is a sentinel for "no value"
continue
}
if outer := ldr.OuterSym(fdsym); outer != gofunc {
panic(fmt.Sprintf("bad carrier sym for symbol %s (funcdata %s#%d), want go.func.* got %s", ldr.SymName(fdsym), ldr.SymName(s), j, ldr.SymName(outer)))
}
sb.SetUint32(ctxt.Arch, dataoff, uint32(ldr.SymValue(fdsym)-gofuncBase))
}
}
}
// pclntab initializes the pclntab symbol with
// runtime function and file name information.
// pclntab generates the pcln table for the link output.
func (ctxt *Link) pclntab(container loader.Bitmap) *pclntab {
// Go 1.2's symtab layout is documented in golang.org/s/go12symtab, but the
// layout and data has changed since that time.
//
// As of August 2020, here's the layout of pclntab:
//
// .gopclntab/__gopclntab [elf/macho section]
// runtime.pclntab
// Carrier symbol for the entire pclntab section.
//
// runtime.pcheader (see: runtime/symtab.go:pcHeader)
// 8-byte magic
// nfunc [thearch.ptrsize bytes]
// offset to runtime.funcnametab from the beginning of runtime.pcheader
// offset to runtime.pclntab_old from beginning of runtime.pcheader
//
// runtime.funcnametab
// []list of null terminated function names
//
// runtime.cutab
// for i=0..#CUs
// for j=0..#max used file index in CU[i]
// uint32 offset into runtime.filetab for the filename[j]
//
// runtime.filetab
// []null terminated filename strings
//
// runtime.pctab
// []byte of deduplicated pc data.
//
// runtime.functab
// function table, alternating PC and offset to func struct [each entry thearch.ptrsize bytes]
// end PC [thearch.ptrsize bytes]
// func structures, pcdata offsets, func data.
state, compUnits, funcs := makePclntab(ctxt, container)
ldr := ctxt.loader
state.carrier = ldr.LookupOrCreateSym("runtime.pclntab", 0)
ldr.MakeSymbolUpdater(state.carrier).SetType(sym.SPCLNTAB)
ldr.SetAttrReachable(state.carrier, true)
setCarrierSym(sym.SPCLNTAB, state.carrier)
state.generatePCHeader(ctxt)
nameOffsets := state.generateFuncnametab(ctxt, funcs)
cuOffsets := state.generateFilenameTabs(ctxt, compUnits, funcs)
state.generatePctab(ctxt, funcs)
inlSyms := makeInlSyms(ctxt, funcs, nameOffsets)
state.generateFunctab(ctxt, funcs, inlSyms, cuOffsets, nameOffsets)
return state
}
func gorootFinal() string {
root := buildcfg.GOROOT
if final := os.Getenv("GOROOT_FINAL"); final != "" {
root = final
}
return root
}
func expandGoroot(s string) string {
const n = len("$GOROOT")
if len(s) >= n+1 && s[:n] == "$GOROOT" && (s[n] == '/' || s[n] == '\\') {
if final := gorootFinal(); final != "" {
return filepath.ToSlash(filepath.Join(final, s[n:]))
}
}
return s
}
const (
BUCKETSIZE = 256 * MINFUNC
SUBBUCKETS = 16
SUBBUCKETSIZE = BUCKETSIZE / SUBBUCKETS
NOIDX = 0x7fffffff
)
// findfunctab generates a lookup table to quickly find the containing
// function for a pc. See src/runtime/symtab.go:findfunc for details.
func (ctxt *Link) findfunctab(state *pclntab, container loader.Bitmap) {
ldr := ctxt.loader
// find min and max address
min := ldr.SymValue(ctxt.Textp[0])
lastp := ctxt.Textp[len(ctxt.Textp)-1]
max := ldr.SymValue(lastp) + ldr.SymSize(lastp)
// for each subbucket, compute the minimum of all symbol indexes
// that map to that subbucket.
n := int32((max - min + SUBBUCKETSIZE - 1) / SUBBUCKETSIZE)
nbuckets := int32((max - min + BUCKETSIZE - 1) / BUCKETSIZE)
size := 4*int64(nbuckets) + int64(n)
writeFindFuncTab := func(_ *Link, s loader.Sym) {
t := ldr.MakeSymbolUpdater(s)
indexes := make([]int32, n)
for i := int32(0); i < n; i++ {
indexes[i] = NOIDX
}
idx := int32(0)
for i, s := range ctxt.Textp {
if !emitPcln(ctxt, s, container) {
continue
}
p := ldr.SymValue(s)
var e loader.Sym
i++
if i < len(ctxt.Textp) {
e = ctxt.Textp[i]
}
for e != 0 && !emitPcln(ctxt, e, container) && i < len(ctxt.Textp) {
e = ctxt.Textp[i]
i++
}
q := max
if e != 0 {
q = ldr.SymValue(e)
}
//print("%d: [%lld %lld] %s\n", idx, p, q, s->name);
for ; p < q; p += SUBBUCKETSIZE {
i = int((p - min) / SUBBUCKETSIZE)
if indexes[i] > idx {
indexes[i] = idx
}
}
i = int((q - 1 - min) / SUBBUCKETSIZE)
if indexes[i] > idx {
indexes[i] = idx
}
idx++
}
// fill in table
for i := int32(0); i < nbuckets; i++ {
base := indexes[i*SUBBUCKETS]
if base == NOIDX {
Errorf(nil, "hole in findfunctab")
}
t.SetUint32(ctxt.Arch, int64(i)*(4+SUBBUCKETS), uint32(base))
for j := int32(0); j < SUBBUCKETS && i*SUBBUCKETS+j < n; j++ {
idx = indexes[i*SUBBUCKETS+j]
if idx == NOIDX {
Errorf(nil, "hole in findfunctab")
}
if idx-base >= 256 {
Errorf(nil, "too many functions in a findfunc bucket! %d/%d %d %d", i, nbuckets, j, idx-base)
}
t.SetUint8(ctxt.Arch, int64(i)*(4+SUBBUCKETS)+4+int64(j), uint8(idx-base))
}
}
}
state.findfunctab = ctxt.createGeneratorSymbol("runtime.findfunctab", 0, sym.SRODATA, size, writeFindFuncTab)
ldr.SetAttrReachable(state.findfunctab, true)
ldr.SetAttrLocal(state.findfunctab, true)
}
// findContainerSyms returns a bitmap, indexed by symbol number, where there's
// a 1 for every container symbol.
func (ctxt *Link) findContainerSyms() loader.Bitmap {
ldr := ctxt.loader
container := loader.MakeBitmap(ldr.NSym())
// Find container symbols and mark them as such.
for _, s := range ctxt.Textp {
outer := ldr.OuterSym(s)
if outer != 0 {
container.Set(outer)
}
}
return container
}
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