5498f8548b
Test: symbol_inject -i a.out -o a.out2 -s symbol -v value Change-Id: I16cd8facbae754f679bef07ab0ba23638286e1d7
76 lines
2.5 KiB
Go
76 lines
2.5 KiB
Go
// Copyright 2018 Google Inc. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package main
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import (
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"debug/elf"
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"fmt"
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"io"
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)
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func findElfSymbol(r io.ReaderAt, symbol string) (uint64, uint64, error) {
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elfFile, err := elf.NewFile(r)
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if err != nil {
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return maxUint64, maxUint64, cantParseError{err}
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}
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symbols, err := elfFile.Symbols()
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if err != nil {
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return maxUint64, maxUint64, err
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}
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for _, s := range symbols {
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if elf.ST_TYPE(s.Info) != elf.STT_OBJECT {
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continue
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}
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if s.Name == symbol {
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offset, err := calculateElfSymbolOffset(elfFile, s)
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if err != nil {
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return maxUint64, maxUint64, err
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}
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return offset, s.Size, nil
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}
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}
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return maxUint64, maxUint64, fmt.Errorf("symbol not found")
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}
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func calculateElfSymbolOffset(file *elf.File, symbol elf.Symbol) (uint64, error) {
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if symbol.Section == elf.SHN_UNDEF || int(symbol.Section) >= len(file.Sections) {
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return maxUint64, fmt.Errorf("invalid section index %d", symbol.Section)
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}
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section := file.Sections[symbol.Section]
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switch file.Type {
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case elf.ET_REL:
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// "In relocatable files, st_value holds a section offset for a defined symbol.
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// That is, st_value is an offset from the beginning of the section that st_shndx identifies."
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return file.Sections[symbol.Section].Addr + symbol.Value, nil
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case elf.ET_EXEC, elf.ET_DYN:
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// "In executable and shared object files, st_value holds a virtual address. To make these
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// files’ symbols more useful for the dynamic linker, the section offset (file interpretation)
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// gives way to a virtual address (memory interpretation) for which the section number is
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// irrelevant."
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if symbol.Value < section.Addr {
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return maxUint64, fmt.Errorf("symbol starts before the start of its section")
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}
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section_offset := symbol.Value - section.Addr
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if section_offset+symbol.Size > section.Size {
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return maxUint64, fmt.Errorf("symbol extends past the end of its section")
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}
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return section.Offset + section_offset, nil
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default:
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return maxUint64, fmt.Errorf("unsupported elf file type %d", file.Type)
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}
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}
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