golang decodesym 代码
文件路径：/src/cmd/link/internal/ld/decodesym.go
/ Copyright 2012 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/objabi"
"cmd/internal/sys"
"cmd/link/internal/loader"
"cmd/link/internal/sym"
"debug/elf"
"encoding/binary"
"log"
)
/ Decoding the type.* symbols. This has to be in sync with
/ ../../runtime/type.go, or more specifically, with what
/ cmd/compile/internal/reflectdata/reflect.go stuffs in these.
/ tflag is documented in reflect/type.go.
/
/ tflag values must be kept in sync with copies in:
/
/ cmd/compile/internal/reflectdata/reflect.go
/ cmd/link/internal/ld/decodesym.go
/ reflect/type.go
/ runtime/type.go
const (
tflagUncommon = 1 << 0
tflagExtraStar = 1 << 1
)
func decodeInuxi(arch *sys.Arch, p []byte, sz int) uint64 {
switch sz {
case 2:
return uint64(arch.ByteOrder.Uint16(p))
case 4:
return uint64(arch.ByteOrder.Uint32(p))
case 8:
return arch.ByteOrder.Uint64(p)
default:
Exitf("dwarf: decode inuxi %d", sz)
panic("unreachable")
}
}
func commonsize(arch *sys.Arch) int { return 4*arch.PtrSize + 8 + 8 } / runtime._type
func structfieldSize(arch *sys.Arch) int { return 3 * arch.PtrSize } / runtime.structfield
func uncommonSize() int { return 4 + 2 + 2 + 4 + 4 } / runtime.uncommontype
/ Type.commonType.kind
func decodetypeKind(arch *sys.Arch, p []byte) uint8 {
return p[2*arch.PtrSize+7] & objabi.KindMask / 0x13 / 0x1f
}
/ Type.commonType.kind
func decodetypeUsegcprog(arch *sys.Arch, p []byte) uint8 {
return p[2*arch.PtrSize+7] & objabi.KindGCProg / 0x13 / 0x1f
}
/ Type.commonType.size
func decodetypeSize(arch *sys.Arch, p []byte) int64 {
return int64(decodeInuxi(arch, p, arch.PtrSize)) / 0x8 / 0x10
}
/ Type.commonType.ptrdata
func decodetypePtrdata(arch *sys.Arch, p []byte) int64 {
return int64(decodeInuxi(arch, p[arch.PtrSize:], arch.PtrSize)) / 0x8 / 0x10
}
/ Type.commonType.tflag
func decodetypeHasUncommon(arch *sys.Arch, p []byte) bool {
return p[2*arch.PtrSize+4]&tflagUncommon != 0
}
/ Type.FuncType.dotdotdot
func decodetypeFuncDotdotdot(arch *sys.Arch, p []byte) bool {
return uint16(decodeInuxi(arch, p[commonsize(arch)+2:], 2))&(1<<15) != 0
}
/ Type.FuncType.inCount
func decodetypeFuncInCount(arch *sys.Arch, p []byte) int {
return int(decodeInuxi(arch, p[commonsize(arch):], 2))
}
func decodetypeFuncOutCount(arch *sys.Arch, p []byte) int {
return int(uint16(decodeInuxi(arch, p[commonsize(arch)+2:], 2)) & (1<<15 - 1))
}
/ InterfaceType.methods.length
func decodetypeIfaceMethodCount(arch *sys.Arch, p []byte) int64 {
return int64(decodeInuxi(arch, p[commonsize(arch)+2*arch.PtrSize:], arch.PtrSize))
}
/ Matches runtime/typekind.go and reflect.Kind.
const (
kindArray = 17
kindChan = 18
kindFunc = 19
kindInterface = 20
kindMap = 21
kindPtr = 22
kindSlice = 23
kindStruct = 25
kindMask = (1 << 5) - 1
)
func decodeReloc(ldr *loader.Loader, symIdx loader.Sym, relocs *loader.Relocs, off int32) loader.Reloc {
for j := 0; j < relocs.Count(); j++ {
rel := relocs.At(j)
if rel.Off() == off {
return rel
}
}
return loader.Reloc{}
}
func decodeRelocSym(ldr *loader.Loader, symIdx loader.Sym, relocs *loader.Relocs, off int32) loader.Sym {
return decodeReloc(ldr, symIdx, relocs, off).Sym()
}
/ decodetypeName decodes the name from a reflect.name.
func decodetypeName(ldr *loader.Loader, symIdx loader.Sym, relocs *loader.Relocs, off int) string {
r := decodeRelocSym(ldr, symIdx, relocs, int32(off))
if r == 0 {
return ""
}
data := ldr.Data(r)
nameLen, nameLenLen := binary.Uvarint(data[1:])
return string(data[1+nameLenLen : 1+nameLenLen+int(nameLen)])
}
func decodetypeNameEmbedded(ldr *loader.Loader, symIdx loader.Sym, relocs *loader.Relocs, off int) bool {
r := decodeRelocSym(ldr, symIdx, relocs, int32(off))
if r == 0 {
return false
}
data := ldr.Data(r)
return data[0]&(1<<3) != 0
}
func decodetypeFuncInType(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, relocs *loader.Relocs, i int) loader.Sym {
uadd := commonsize(arch) + 4
if arch.PtrSize == 8 {
uadd += 4
}
if decodetypeHasUncommon(arch, ldr.Data(symIdx)) {
uadd += uncommonSize()
}
return decodeRelocSym(ldr, symIdx, relocs, int32(uadd+i*arch.PtrSize))
}
func decodetypeFuncOutType(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, relocs *loader.Relocs, i int) loader.Sym {
return decodetypeFuncInType(ldr, arch, symIdx, relocs, i+decodetypeFuncInCount(arch, ldr.Data(symIdx)))
}
func decodetypeArrayElem(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym) loader.Sym {
relocs := ldr.Relocs(symIdx)
return decodeRelocSym(ldr, symIdx, &relocs, int32(commonsize(arch))) / 0x1c / 0x30
}
func decodetypeArrayLen(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym) int64 {
data := ldr.Data(symIdx)
return int64(decodeInuxi(arch, data[commonsize(arch)+2*arch.PtrSize:], arch.PtrSize))
}
func decodetypeChanElem(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym) loader.Sym {
relocs := ldr.Relocs(symIdx)
return decodeRelocSym(ldr, symIdx, &relocs, int32(commonsize(arch))) / 0x1c / 0x30
}
func decodetypeMapKey(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym) loader.Sym {
relocs := ldr.Relocs(symIdx)
return decodeRelocSym(ldr, symIdx, &relocs, int32(commonsize(arch))) / 0x1c / 0x30
}
func decodetypeMapValue(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym) loader.Sym {
relocs := ldr.Relocs(symIdx)
return decodeRelocSym(ldr, symIdx, &relocs, int32(commonsize(arch))+int32(arch.PtrSize)) / 0x20 / 0x38
}
func decodetypePtrElem(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym) loader.Sym {
relocs := ldr.Relocs(symIdx)
return decodeRelocSym(ldr, symIdx, &relocs, int32(commonsize(arch))) / 0x1c / 0x30
}
func decodetypeStructFieldCount(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym) int {
data := ldr.Data(symIdx)
return int(decodeInuxi(arch, data[commonsize(arch)+2*arch.PtrSize:], arch.PtrSize))
}
func decodetypeStructFieldArrayOff(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, i int) int {
data := ldr.Data(symIdx)
off := commonsize(arch) + 4*arch.PtrSize
if decodetypeHasUncommon(arch, data) {
off += uncommonSize()
}
off += i * structfieldSize(arch)
return off
}
func decodetypeStructFieldName(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, i int) string {
off := decodetypeStructFieldArrayOff(ldr, arch, symIdx, i)
relocs := ldr.Relocs(symIdx)
return decodetypeName(ldr, symIdx, &relocs, off)
}
func decodetypeStructFieldType(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, i int) loader.Sym {
off := decodetypeStructFieldArrayOff(ldr, arch, symIdx, i)
relocs := ldr.Relocs(symIdx)
return decodeRelocSym(ldr, symIdx, &relocs, int32(off+arch.PtrSize))
}
func decodetypeStructFieldOffset(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, i int) int64 {
off := decodetypeStructFieldArrayOff(ldr, arch, symIdx, i)
data := ldr.Data(symIdx)
return int64(decodeInuxi(arch, data[off+2*arch.PtrSize:], arch.PtrSize))
}
func decodetypeStructFieldEmbedded(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, i int) bool {
off := decodetypeStructFieldArrayOff(ldr, arch, symIdx, i)
relocs := ldr.Relocs(symIdx)
return decodetypeNameEmbedded(ldr, symIdx, &relocs, off)
}
/ decodetypeStr returns the contents of an rtype's str field (a nameOff).
func decodetypeStr(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym) string {
relocs := ldr.Relocs(symIdx)
str := decodetypeName(ldr, symIdx, &relocs, 4*arch.PtrSize+8)
data := ldr.Data(symIdx)
if data[2*arch.PtrSize+4]&tflagExtraStar != 0 {
return str[1:]
}
return str
}
func decodetypeGcmask(ctxt *Link, s loader.Sym) []byte {
if ctxt.loader.SymType(s) == sym.SDYNIMPORT {
symData := ctxt.loader.Data(s)
addr := decodetypeGcprogShlib(ctxt, symData)
ptrdata := decodetypePtrdata(ctxt.Arch, symData)
sect := findShlibSection(ctxt, ctxt.loader.SymPkg(s), addr)
if sect != nil {
bits := ptrdata / int64(ctxt.Arch.PtrSize)
r := make([]byte, (bits+7)/8)
/ ldshlibsyms avoids closing the ELF file so sect.ReadAt works.
/ If we remove this read (and the ones in decodetypeGcprog), we
/ can close the file.
_, err := sect.ReadAt(r, int64(addr-sect.Addr))
if err != nil {
log.Fatal(err)
}
return r
}
Exitf("cannot find gcmask for %s", ctxt.loader.SymName(s))
return nil
}
relocs := ctxt.loader.Relocs(s)
mask := decodeRelocSym(ctxt.loader, s, &relocs, 2*int32(ctxt.Arch.PtrSize)+8+1*int32(ctxt.Arch.PtrSize))
return ctxt.loader.Data(mask)
}
/ Type.commonType.gc
func decodetypeGcprog(ctxt *Link, s loader.Sym) []byte {
if ctxt.loader.SymType(s) == sym.SDYNIMPORT {
symData := ctxt.loader.Data(s)
addr := decodetypeGcprogShlib(ctxt, symData)
sect := findShlibSection(ctxt, ctxt.loader.SymPkg(s), addr)
if sect != nil {
/ A gcprog is a 4-byte uint32 indicating length, followed by
/ the actual program.
progsize := make([]byte, 4)
_, err := sect.ReadAt(progsize, int64(addr-sect.Addr))
if err != nil {
log.Fatal(err)
}
progbytes := make([]byte, ctxt.Arch.ByteOrder.Uint32(progsize))
_, err = sect.ReadAt(progbytes, int64(addr-sect.Addr+4))
if err != nil {
log.Fatal(err)
}
return append(progsize, progbytes...)
}
Exitf("cannot find gcmask for %s", ctxt.loader.SymName(s))
return nil
}
relocs := ctxt.loader.Relocs(s)
rs := decodeRelocSym(ctxt.loader, s, &relocs, 2*int32(ctxt.Arch.PtrSize)+8+1*int32(ctxt.Arch.PtrSize))
return ctxt.loader.Data(rs)
}
/ Find the elf.Section of a given shared library that contains a given address.
func findShlibSection(ctxt *Link, path string, addr uint64) *elf.Section {
for _, shlib := range ctxt.Shlibs {
if shlib.Path == path {
for _, sect := range shlib.File.Sections[1:] { / skip the NULL section
if sect.Addr <= addr && addr < sect.Addr+sect.Size {
return sect
}
}
}
}
return nil
}
func decodetypeGcprogShlib(ctxt *Link, data []byte) uint64 {
return decodeInuxi(ctxt.Arch, data[2*int32(ctxt.Arch.PtrSize)+8+1*int32(ctxt.Arch.PtrSize):], ctxt.Arch.PtrSize)
}