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 <fcntl.h>
18 #include <unistd.h>
19 #include <string.h>
20
21 char arch[] = "PowerPC";
22
23 #define N_DESCR 6
24 unsigned int descr[N_DESCR] = {
25 #if 1
26 /* values for IBM RS/6000 machines */
27 0xffffffff, /* real-mode = true */
28 0x00c00000, /* real-base, i.e. where we expect OF to be */
29 0xffffffff, /* real-size */
30 0xffffffff, /* virt-base */
31 0xffffffff, /* virt-size */
32 0x4000, /* load-base */
33 #else
34 /* values for longtrail CHRP */
35 0, /* real-mode = false */
36 0xffffffff, /* real-base */
37 0xffffffff, /* real-size */
38 0xffffffff, /* virt-base */
39 0xffffffff, /* virt-size */
40 0x00600000, /* load-base */
41 #endif
42 };
43
44 unsigned char buf[512];
45
46 #define GET_16BE(off) ((buf[off] << 8) + (buf[(off)+1]))
47 #define GET_32BE(off) ((GET_16BE(off) << 16) + GET_16BE((off)+2))
48
49 #define PUT_16BE(off, v) (buf[off] = ((v) >> 8) & 0xff, \
50 buf[(off) + 1] = (v) & 0xff)
51 #define PUT_32BE(off, v) (PUT_16BE((off), (v) >> 16), \
52 PUT_16BE((off) + 2, (v)))
53
54 /* Structure of an ELF file */
55 #define E_IDENT 0 /* ELF header */
56 #define E_PHOFF 28
57 #define E_PHENTSIZE 42
58 #define E_PHNUM 44
59 #define E_HSIZE 52 /* size of ELF header */
60
61 #define EI_MAGIC 0 /* offsets in E_IDENT area */
62 #define EI_CLASS 4
63 #define EI_DATA 5
64
65 #define PH_TYPE 0 /* ELF program header */
66 #define PH_OFFSET 4
67 #define PH_FILESZ 16
68 #define PH_HSIZE 32 /* size of program header */
69
70 #define PT_NOTE 4 /* Program header type = note */
71
72 #define ELFCLASS32 1
73 #define ELFDATA2MSB 2
74
75 unsigned char elf_magic[4] = { 0x7f, 'E', 'L', 'F' };
76
main(int ac,char ** av)77 int main(int ac, char **av)
78 {
79 int fd, n, i;
80 int ph, ps, np;
81 int nnote, ns;
82
83 if (ac != 2) {
84 fprintf(stderr, "Usage: %s elf-file\n", av[0]);
85 exit(1);
86 }
87 fd = open(av[1], O_RDWR);
88 if (fd < 0) {
89 perror(av[1]);
90 exit(1);
91 }
92
93 nnote = strlen(arch) + 1 + (N_DESCR + 3) * 4;
94
95 n = read(fd, buf, sizeof(buf));
96 if (n < 0) {
97 perror("read");
98 exit(1);
99 }
100
101 if (n < E_HSIZE || memcmp(&buf[E_IDENT+EI_MAGIC], elf_magic, 4) != 0)
102 goto notelf;
103
104 if (buf[E_IDENT+EI_CLASS] != ELFCLASS32
105 || buf[E_IDENT+EI_DATA] != ELFDATA2MSB) {
106 fprintf(stderr, "%s is not a big-endian 32-bit ELF image\n",
107 av[1]);
108 exit(1);
109 }
110
111 ph = GET_32BE(E_PHOFF);
112 ps = GET_16BE(E_PHENTSIZE);
113 np = GET_16BE(E_PHNUM);
114 if (ph < E_HSIZE || ps < PH_HSIZE || np < 1)
115 goto notelf;
116 if (ph + (np + 1) * ps + nnote > n)
117 goto nospace;
118
119 for (i = 0; i < np; ++i) {
120 if (GET_32BE(ph + PH_TYPE) == PT_NOTE) {
121 fprintf(stderr, "%s already has a note entry\n",
122 av[1]);
123 exit(0);
124 }
125 ph += ps;
126 }
127
128 /* XXX check that the area we want to use is all zeroes */
129 for (i = 0; i < ps + nnote; ++i)
130 if (buf[ph + i] != 0)
131 goto nospace;
132
133 /* fill in the program header entry */
134 ns = ph + ps;
135 PUT_32BE(ph + PH_TYPE, PT_NOTE);
136 PUT_32BE(ph + PH_OFFSET, ns);
137 PUT_32BE(ph + PH_FILESZ, nnote);
138
139 /* fill in the note area we point to */
140 /* XXX we should probably make this a proper section */
141 PUT_32BE(ns, strlen(arch) + 1);
142 PUT_32BE(ns + 4, N_DESCR * 4);
143 PUT_32BE(ns + 8, 0x1275);
144 strcpy(&buf[ns + 12], arch);
145 ns += 12 + strlen(arch) + 1;
146 for (i = 0; i < N_DESCR; ++i)
147 PUT_32BE(ns + i * 4, descr[i]);
148
149 /* Update the number of program headers */
150 PUT_16BE(E_PHNUM, np + 1);
151
152 /* write back */
153 lseek(fd, (long) 0, SEEK_SET);
154 i = write(fd, buf, n);
155 if (i < 0) {
156 perror("write");
157 exit(1);
158 }
159 if (i < n) {
160 fprintf(stderr, "%s: write truncated\n", av[1]);
161 exit(1);
162 }
163
164 exit(0);
165
166 notelf:
167 fprintf(stderr, "%s does not appear to be an ELF file\n", av[0]);
168 exit(1);
169
170 nospace:
171 fprintf(stderr, "sorry, I can't find space in %s to put the note\n",
172 av[0]);
173 exit(1);
174 }
175