File size: 3,770 Bytes
d7a5f2f | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 | // 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.
// Parsing of ELF executables (Linux, FreeBSD, and so on).
package objfile
import (
"debug/dwarf"
"debug/elf"
"encoding/binary"
"fmt"
"io"
)
type elfFile struct {
elf *elf.File
}
func openElf(r io.ReaderAt) (rawFile, error) {
f, err := elf.NewFile(r)
if err != nil {
return nil, err
}
return &elfFile{f}, nil
}
func (f *elfFile) symbols() ([]Sym, error) {
elfSyms, err := f.elf.Symbols()
if err != nil {
return nil, err
}
var syms []Sym
for _, s := range elfSyms {
sym := Sym{Addr: s.Value, Name: s.Name, Size: int64(s.Size), Code: '?'}
switch s.Section {
case elf.SHN_UNDEF:
sym.Code = 'U'
case elf.SHN_COMMON:
sym.Code = 'B'
default:
i := int(s.Section)
if i < 0 || i >= len(f.elf.Sections) {
break
}
sect := f.elf.Sections[i]
switch sect.Flags & (elf.SHF_WRITE | elf.SHF_ALLOC | elf.SHF_EXECINSTR) {
case elf.SHF_ALLOC | elf.SHF_EXECINSTR:
sym.Code = 'T'
case elf.SHF_ALLOC:
sym.Code = 'R'
case elf.SHF_ALLOC | elf.SHF_WRITE:
sym.Code = 'D'
}
}
if elf.ST_BIND(s.Info) == elf.STB_LOCAL {
sym.Code += 'a' - 'A'
}
syms = append(syms, sym)
}
return syms, nil
}
func (f *elfFile) pcln() (textStart uint64, pclntab []byte, err error) {
if sect := f.elf.Section(".text"); sect != nil {
textStart = sect.Addr
}
sect := f.elf.Section(".gopclntab")
if sect == nil {
// try .data.rel.ro.gopclntab, for PIE binaries
sect = f.elf.Section(".data.rel.ro.gopclntab")
}
if sect != nil {
if pclntab, err = sect.Data(); err != nil {
return 0, nil, err
}
} else {
// if both sections failed, try the symbol
pclntab = f.symbolData("runtime.pclntab", "runtime.epclntab")
}
return textStart, pclntab, nil
}
func (f *elfFile) text() (textStart uint64, text []byte, err error) {
sect := f.elf.Section(".text")
if sect == nil {
return 0, nil, fmt.Errorf("text section not found")
}
textStart = sect.Addr
text, err = sect.Data()
return
}
func (f *elfFile) goarch() string {
switch f.elf.Machine {
case elf.EM_386:
return "386"
case elf.EM_X86_64:
return "amd64"
case elf.EM_ARM:
return "arm"
case elf.EM_AARCH64:
return "arm64"
case elf.EM_LOONGARCH:
return "loong64"
case elf.EM_PPC64:
if f.elf.ByteOrder == binary.LittleEndian {
return "ppc64le"
}
return "ppc64"
case elf.EM_RISCV:
if f.elf.Class == elf.ELFCLASS64 {
return "riscv64"
}
case elf.EM_S390:
return "s390x"
}
return ""
}
func (f *elfFile) loadAddress() (uint64, error) {
for _, p := range f.elf.Progs {
if p.Type == elf.PT_LOAD && p.Flags&elf.PF_X != 0 {
// The memory mapping that contains the segment
// starts at an aligned address. Apparently this
// is what pprof expects, as it uses this and the
// start address of the mapping to compute PC
// delta.
return p.Vaddr - p.Vaddr%p.Align, nil
}
}
return 0, fmt.Errorf("unknown load address")
}
func (f *elfFile) dwarf() (*dwarf.Data, error) {
return f.elf.DWARF()
}
func (f *elfFile) symbolData(start, end string) []byte {
elfSyms, err := f.elf.Symbols()
if err != nil {
return nil
}
var addr, eaddr uint64
for _, s := range elfSyms {
if s.Name == start {
addr = s.Value
} else if s.Name == end {
eaddr = s.Value
}
if addr != 0 && eaddr != 0 {
break
}
}
if addr == 0 || eaddr < addr {
return nil
}
size := eaddr - addr
data := make([]byte, size)
for _, prog := range f.elf.Progs {
if prog.Vaddr <= addr && addr+size-1 <= prog.Vaddr+prog.Filesz-1 {
if _, err := prog.ReadAt(data, int64(addr-prog.Vaddr)); err != nil {
return nil
}
return data
}
}
return nil
}
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