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// Copyright 2016 syzkaller project authors. All rights reserved.
// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
package symbolizer
import (
"debug/elf"
"fmt"
"sort"
)
type Symbol struct {
Addr uint64
Size int
}
// ReadTextSymbols returns list of text symbols in the binary bin.
func ReadTextSymbols(bin string) (map[string][]Symbol, error) {
return read(bin, true)
}
// ReadRodataSymbols returns list of rodata symbols in the binary bin.
func ReadRodataSymbols(bin string) (map[string][]Symbol, error) {
return read(bin, false)
}
func read(bin string, text bool) (map[string][]Symbol, error) {
raw, err := load(bin, text)
if err != nil {
return nil, err
}
sort.Slice(raw, func(i, j int) bool {
return raw[i].Value > raw[j].Value
})
symbols := make(map[string][]Symbol)
// Function sizes reported by the Linux kernel do not match symbol tables.
// The kernel computes size of a symbol based on the start of the next symbol.
// We need to do the same to match kernel sizes to be able to find the right
// symbol across multiple symbols with the same name.
var prevAddr uint64
var prevSize int
for _, symb := range raw {
size := int(symb.Size)
if text {
if symb.Value == prevAddr {
size = prevSize
} else if prevAddr != 0 {
size = int(prevAddr - symb.Value)
}
prevAddr, prevSize = symb.Value, size
}
symbols[symb.Name] = append(symbols[symb.Name], Symbol{symb.Value, size})
}
return symbols, nil
}
func load(bin string, text bool) ([]elf.Symbol, error) {
file, err := elf.Open(bin)
if err != nil {
return nil, fmt.Errorf("failed to open ELF file %v: %w", bin, err)
}
allSymbols, err := file.Symbols()
if err != nil {
return nil, fmt.Errorf("failed to read ELF symbols: %w", err)
}
var symbols []elf.Symbol
for _, symb := range allSymbols {
if symb.Size == 0 || symb.Section < 0 || int(symb.Section) >= len(file.Sections) {
continue
}
sect := file.Sections[symb.Section]
isText := sect.Type == elf.SHT_PROGBITS &&
sect.Flags&elf.SHF_ALLOC != 0 &&
sect.Flags&elf.SHF_EXECINSTR != 0
// Note: x86_64 vmlinux .rodata is marked as writable and according to flags it looks like .data,
// so we look at the name.
if text && !isText || !text && sect.Name != ".rodata" {
continue
}
symbols = append(symbols, symb)
}
return symbols, nil
}
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