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/*
* Program to hack in a PT_NOTE program header entry in an ELF file.
* This is needed for OF on RS/6000s to load an image correctly.
* Note that OF needs a program header entry for the note, not an
* ELF section.
*
* Copyright 2000 Paul Mackerras.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* Usage: addnote zImage
*/
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
char arch[] = "PowerPC";
#define N_DESCR 6
unsigned int descr[N_DESCR] = {
0xffffffff, /* real-mode = true */
0x00c00000, /* real-base, i.e. where we expect OF to be */
0xffffffff, /* real-size */
0xffffffff, /* virt-base */
0xffffffff, /* virt-size */
0x4000, /* load-base */
};
unsigned char buf[512];
#define GET_16BE(off) ((buf[off] << 8) + (buf[(off)+1]))
#define GET_32BE(off) ((GET_16BE(off) << 16) + GET_16BE((off)+2))
#define PUT_16BE(off, v) (buf[off] = ((v) >> 8) & 0xff, \
buf[(off) + 1] = (v) & 0xff)
#define PUT_32BE(off, v) (PUT_16BE((off), (v) >> 16), \
PUT_16BE((off) + 2, (v)))
/* Structure of an ELF file */
#define E_IDENT 0 /* ELF header */
#define E_PHOFF 28
#define E_PHENTSIZE 42
#define E_PHNUM 44
#define E_HSIZE 52 /* size of ELF header */
#define EI_MAGIC 0 /* offsets in E_IDENT area */
#define EI_CLASS 4
#define EI_DATA 5
#define PH_TYPE 0 /* ELF program header */
#define PH_OFFSET 4
#define PH_FILESZ 16
#define PH_HSIZE 32 /* size of program header */
#define PT_NOTE 4 /* Program header type = note */
#define ELFCLASS32 1
#define ELFDATA2MSB 2
unsigned char elf_magic[4] = { 0x7f, 'E', 'L', 'F' };
main(int ac, char **av)
{
int fd, n, i;
int ph, ps, np;
int nnote, ns;
if (ac != 2) {
fprintf(stderr, "Usage: %s elf-file\n", av[0]);
exit(1);
}
fd = open(av[1], O_RDWR);
if (fd < 0) {
perror(av[1]);
exit(1);
}
nnote = strlen(arch) + 1 + (N_DESCR + 3) * 4;
n = read(fd, buf, sizeof(buf));
if (n < 0) {
perror("read");
exit(1);
}
if (n < E_HSIZE || memcmp(&buf[E_IDENT+EI_MAGIC], elf_magic, 4) != 0)
goto notelf;
if (buf[E_IDENT+EI_CLASS] != ELFCLASS32
|| buf[E_IDENT+EI_DATA] != ELFDATA2MSB) {
fprintf(stderr, "%s is not a big-endian 32-bit ELF image\n",
av[1]);
exit(1);
}
ph = GET_32BE(E_PHOFF);
ps = GET_16BE(E_PHENTSIZE);
np = GET_16BE(E_PHNUM);
if (ph < E_HSIZE || ps < PH_HSIZE || np < 1)
goto notelf;
if (ph + (np + 1) * ps + nnote > n)
goto nospace;
for (i = 0; i < np; ++i) {
if (GET_32BE(ph + PH_TYPE) == PT_NOTE) {
fprintf(stderr, "%s already has a note entry\n",
av[1]);
exit(0);
}
ph += ps;
}
/* XXX check that the area we want to use is all zeroes */
for (i = 0; i < ps + nnote; ++i)
if (buf[ph + i] != 0)
goto nospace;
/* fill in the program header entry */
ns = ph + ps;
PUT_32BE(ph + PH_TYPE, PT_NOTE);
PUT_32BE(ph + PH_OFFSET, ns);
PUT_32BE(ph + PH_FILESZ, nnote);
/* fill in the note area we point to */
/* XXX we should probably make this a proper section */
PUT_32BE(ns, strlen(arch) + 1);
PUT_32BE(ns + 4, N_DESCR * 4);
PUT_32BE(ns + 8, 0x1275);
strcpy(&buf[ns + 12], arch);
ns += 12 + strlen(arch) + 1;
for (i = 0; i < N_DESCR; ++i)
PUT_32BE(ns + i * 4, descr[i]);
/* Update the number of program headers */
PUT_16BE(E_PHNUM, np + 1);
/* write back */
lseek(fd, (long) 0, SEEK_SET);
i = write(fd, buf, n);
if (i < 0) {
perror("write");
exit(1);
}
if (i < n) {
fprintf(stderr, "%s: write truncated\n", av[1]);
exit(1);
}
exit(0);
notelf:
fprintf(stderr, "%s does not appear to be an ELF file\n", av[0]);
exit(1);
nospace:
fprintf(stderr, "sorry, I can't find space in %s to put the note\n",
av[0]);
exit(1);
}
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