1 /*
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
5 * ELF section.
6 *
7 * Copyright 2000 Paul Mackerras.
8 *
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.
13 *
14 * Usage: addnote zImage
15 */
16 #include <stdio.h>
17 #include <stdlib.h>
18 #include <fcntl.h>
19 #include <unistd.h>
20 #include <string.h>
21
22 char arch[] = "PowerPC";
23
24 #define N_DESCR 6
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 */
32 };
33
34 unsigned char buf[512];
35
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
39 #define PUT_16BE(off, v) (buf[off] = ((v) >> 8) & 0xff, \
40 buf[(off) + 1] = (v) & 0xff)
41 #define PUT_32BE(off, v) (PUT_16BE((off), (v) >> 16), \
42 PUT_16BE((off) + 2, (v)))
43
44 /* Structure of an ELF file */
45 #define E_IDENT 0 /* ELF header */
46 #define E_PHOFF 28
47 #define E_PHENTSIZE 42
48 #define E_PHNUM 44
49 #define E_HSIZE 52 /* size of ELF header */
50
51 #define EI_MAGIC 0 /* offsets in E_IDENT area */
52 #define EI_CLASS 4
53 #define EI_DATA 5
54
55 #define PH_TYPE 0 /* ELF program header */
56 #define PH_OFFSET 4
57 #define PH_FILESZ 16
58 #define PH_HSIZE 32 /* size of program header */
59
60 #define PT_NOTE 4 /* Program header type = note */
61
62 #define ELFCLASS32 1
63 #define ELFDATA2MSB 2
64
65 unsigned char elf_magic[4] = { 0x7f, 'E', 'L', 'F' };
66
67 int
main(int ac,char ** av)68 main(int ac, char **av)
69 {
70 int fd, n, i;
71 int ph, ps, np;
72 int nnote, ns;
73
74 if (ac != 2) {
75 fprintf(stderr, "Usage: %s elf-file\n", av[0]);
76 exit(1);
77 }
78 fd = open(av[1], O_RDWR);
79 if (fd < 0) {
80 perror(av[1]);
81 exit(1);
82 }
83
84 nnote = strlen(arch) + 1 + (N_DESCR + 3) * 4;
85
86 n = read(fd, buf, sizeof(buf));
87 if (n < 0) {
88 perror("read");
89 exit(1);
90 }
91
92 if (n < E_HSIZE || memcmp(&buf[E_IDENT+EI_MAGIC], elf_magic, 4) != 0)
93 goto notelf;
94
95 if (buf[E_IDENT+EI_CLASS] != ELFCLASS32
96 || buf[E_IDENT+EI_DATA] != ELFDATA2MSB) {
97 fprintf(stderr, "%s is not a big-endian 32-bit ELF image\n",
98 av[1]);
99 exit(1);
100 }
101
102 ph = GET_32BE(E_PHOFF);
103 ps = GET_16BE(E_PHENTSIZE);
104 np = GET_16BE(E_PHNUM);
105 if (ph < E_HSIZE || ps < PH_HSIZE || np < 1)
106 goto notelf;
107 if (ph + (np + 1) * ps + nnote > n)
108 goto nospace;
109
110 for (i = 0; i < np; ++i) {
111 if (GET_32BE(ph + PH_TYPE) == PT_NOTE) {
112 fprintf(stderr, "%s already has a note entry\n",
113 av[1]);
114 exit(0);
115 }
116 ph += ps;
117 }
118
119 /* XXX check that the area we want to use is all zeroes */
120 for (i = 0; i < ps + nnote; ++i)
121 if (buf[ph + i] != 0)
122 goto nospace;
123
124 /* fill in the program header entry */
125 ns = ph + ps;
126 PUT_32BE(ph + PH_TYPE, PT_NOTE);
127 PUT_32BE(ph + PH_OFFSET, ns);
128 PUT_32BE(ph + PH_FILESZ, nnote);
129
130 /* fill in the note area we point to */
131 /* XXX we should probably make this a proper section */
132 PUT_32BE(ns, strlen(arch) + 1);
133 PUT_32BE(ns + 4, N_DESCR * 4);
134 PUT_32BE(ns + 8, 0x1275);
135 strcpy(&buf[ns + 12], arch);
136 ns += 12 + strlen(arch) + 1;
137 for (i = 0; i < N_DESCR; ++i)
138 PUT_32BE(ns + i * 4, descr[i]);
139
140 /* Update the number of program headers */
141 PUT_16BE(E_PHNUM, np + 1);
142
143 /* write back */
144 lseek(fd, (long) 0, SEEK_SET);
145 i = write(fd, buf, n);
146 if (i < 0) {
147 perror("write");
148 exit(1);
149 }
150 if (i < n) {
151 fprintf(stderr, "%s: write truncated\n", av[1]);
152 exit(1);
153 }
154
155 exit(0);
156
157 notelf:
158 fprintf(stderr, "%s does not appear to be an ELF file\n", av[0]);
159 exit(1);
160
161 nospace:
162 fprintf(stderr, "sorry, I can't find space in %s to put the note\n",
163 av[0]);
164 exit(1);
165 }
166