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