2 * Copyright (c) 2011 The Native Client Authors. All rights reserved.
3 * Use of this source code is governed by a BSD-style license that can be
4 * found in the LICENSE file.
6 * This is a trivial program to edit an ELF file in place, making
7 * one crucial modification to a program header. It's invoked:
8 * bootstrap_phdr_hacker FILENAME SEGMENT_NUMBER
9 * where SEGMENT_NUMBER is the zero-origin index of the program header
10 * we'll touch. This is a PT_LOAD with p_filesz of zero. We change its
11 * p_filesz to match its p_memsz value.
22 int main(int argc, char **argv) {
31 error(1, 0, "Usage: %s FILENAME SEGMENT_NUMBER", argv[0]);
34 segment = atoi(argv[2]);
36 fd = open(file, O_RDWR);
38 error(2, errno, "Cannot open %s for read/write", file);
40 if (elf_version(EV_CURRENT) == EV_NONE)
41 error(2, 0, "elf_version: %s", elf_errmsg(-1));
43 elf = elf_begin(fd, ELF_C_RDWR, NULL);
45 error(2, 0, "elf_begin: %s", elf_errmsg(-1));
47 if (elf_flagelf(elf, ELF_C_SET, ELF_F_LAYOUT) == 0)
48 error(2, 0, "elf_flagelf: %s", elf_errmsg(-1));
50 ph = gelf_getphdr(elf, segment, &phdr);
52 error(2, 0, "gelf_getphdr: %s", elf_errmsg(-1));
54 if (ph->p_type != PT_LOAD)
55 error(3, 0, "Program header %d is %u, not PT_LOAD",
56 segment, (unsigned int) ph->p_type);
57 if (ph->p_filesz != 0)
58 error(3, 0, "Program header %d has nonzero p_filesz", segment);
60 ph->p_filesz = ph->p_memsz;
61 if (gelf_update_phdr(elf, segment, ph) == 0)
62 error(2, 0, "gelf_update_phdr: %s", elf_errmsg(-1));
64 if (elf_flagphdr(elf, ELF_C_SET, ELF_F_DIRTY) == 0)
65 error(2, 0, "elf_flagphdr: %s", elf_errmsg(-1));
67 if (elf_update(elf, ELF_C_WRITE) < 0)
68 error(2, 0, "elf_update: %s", elf_errmsg(-1));