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package builder
import (
"debug/elf"
"fmt"
"os"
)
func getElfSectionData(executable string, sectionName string) ([]byte, elf.FileHeader, error) {
elfFile, err := elf.Open(executable)
if err != nil {
return nil, elf.FileHeader{}, err
}
defer elfFile.Close()
section := elfFile.Section(sectionName)
if section == nil {
return nil, elf.FileHeader{}, fmt.Errorf("could not find %s section", sectionName)
}
data, err := section.Data()
return data, elfFile.FileHeader, err
}
func replaceElfSection(executable string, sectionName string, data []byte) error {
fp, err := os.OpenFile(executable, os.O_RDWR, 0)
if err != nil {
return err
}
defer fp.Close()
elfFile, err := elf.Open(executable)
if err != nil {
return err
}
defer elfFile.Close()
section := elfFile.Section(sectionName)
if section == nil {
return fmt.Errorf("could not find %s section", sectionName)
}
// Implicitly check for compressed sections
if section.Size != section.FileSize {
return fmt.Errorf("expected section %s to have identical size and file size, got %d and %d", sectionName, section.Size, section.FileSize)
}
// Only permit complete replacement of section
if section.Size != uint64(len(data)) {
return fmt.Errorf("expected section %s to have size %d, was actually %d", sectionName, len(data), section.Size)
}
// Write the replacement section data
_, err = fp.WriteAt(data, int64(section.Offset))
return err
}
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