2 * Program to hack in a PT_NOTE program header entry in an ELF file.
3 * This is needed for OF on RS/6000s to load an image correctly.
4 * Note that OF needs a program header entry for the note, not an
7 * Copyright 2000 Paul Mackerras.
9 * This program is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU General Public License
11 * as published by the Free Software Foundation; either version
12 * 2 of the License, or (at your option) any later version.
14 * Usage: addnote zImage
22 char arch[] = "PowerPC";
25 unsigned int descr[N_DESCR] = {
26 0xffffffff, /* real-mode = true */
27 0x00c00000, /* real-base, i.e. where we expect OF to be */
28 0xffffffff, /* real-size */
29 0xffffffff, /* virt-base */
30 0xffffffff, /* virt-size */
31 0x4000, /* load-base */
34 unsigned char buf[512];
36 #define GET_16BE(off) ((buf[off] << 8) + (buf[(off)+1]))
37 #define GET_32BE(off) ((GET_16BE(off) << 16) + GET_16BE((off)+2))
38 #define PUT_16BE(off, v) (buf[off] = ((v) >> 8) & 0xff, \
39 buf[(off) + 1] = (v) & 0xff)
40 #define PUT_32BE(off, v) (PUT_16BE((off), (v) >> 16), \
41 PUT_16BE((off) + 2, (v)))
43 /* Structure of an ELF file */
44 #define E_IDENT 0 /* ELF header */
46 #define E_PHENTSIZE 42
48 #define E_HSIZE 52 /* size of ELF header */
50 #define EI_MAGIC 0 /* offsets in E_IDENT area */
54 #define PH_TYPE 0 /* ELF program header */
57 #define PH_HSIZE 32 /* size of program header */
59 #define PT_NOTE 4 /* Program header type = note */
64 unsigned char elf_magic[4] = { 0x7f, 'E', 'L', 'F' };
67 main(int ac, char **av)
74 fprintf(stderr, "Usage: %s elf-file\n", av[0]);
77 fd = open(av[1], O_RDWR);
83 nnote = strlen(arch) + 1 + (N_DESCR + 3) * 4;
85 n = read(fd, buf, sizeof(buf));
91 if (n < E_HSIZE || memcmp(&buf[E_IDENT+EI_MAGIC], elf_magic, 4) != 0)
94 if (buf[E_IDENT+EI_CLASS] != ELFCLASS32
95 || buf[E_IDENT+EI_DATA] != ELFDATA2MSB) {
96 fprintf(stderr, "%s is not a big-endian 32-bit ELF image\n",
101 ph = GET_32BE(E_PHOFF);
102 ps = GET_16BE(E_PHENTSIZE);
103 np = GET_16BE(E_PHNUM);
104 if (ph < E_HSIZE || ps < PH_HSIZE || np < 1)
106 if (ph + (np + 1) * ps + nnote > n)
109 for (i = 0; i < np; ++i) {
110 if (GET_32BE(ph + PH_TYPE) == PT_NOTE) {
111 fprintf(stderr, "%s already has a note entry\n",
118 /* XXX check that the area we want to use is all zeroes */
119 for (i = 0; i < ps + nnote; ++i)
120 if (buf[ph + i] != 0)
123 /* fill in the program header entry */
125 PUT_32BE(ph + PH_TYPE, PT_NOTE);
126 PUT_32BE(ph + PH_OFFSET, ns);
127 PUT_32BE(ph + PH_FILESZ, nnote);
129 /* fill in the note area we point to */
130 /* XXX we should probably make this a proper section */
131 PUT_32BE(ns, strlen(arch) + 1);
132 PUT_32BE(ns + 4, N_DESCR * 4);
133 PUT_32BE(ns + 8, 0x1275);
134 strcpy(&buf[ns + 12], arch);
135 ns += 12 + strlen(arch) + 1;
136 for (i = 0; i < N_DESCR; ++i)
137 PUT_32BE(ns + i * 4, descr[i]);
139 /* Update the number of program headers */
140 PUT_16BE(E_PHNUM, np + 1);
143 lseek(fd, (long) 0, SEEK_SET);
144 i = write(fd, buf, n);
150 fprintf(stderr, "%s: write truncated\n", av[1]);
157 fprintf(stderr, "%s does not appear to be an ELF file\n", av[1]);
161 fprintf(stderr, "sorry, I can't find space in %s to put the note\n",
168 * c-file-style: "k&r"