1/*
2 * BK Id: SCCS/s.addnote.c 1.7 05/18/01 15:17:23 cort
3 */
4/*
5 * Program to hack in a PT_NOTE program header entry in an ELF file.
6 * This is needed for OF on RS/6000s to load an image correctly.
7 * Note that OF needs a program header entry for the note, not an
8 * ELF section.
9 *
10 * Copyright 2000 Paul Mackerras.
11 *
12 * This program is free software; you can redistribute it and/or
13 * modify it under the terms of the GNU General Public License
14 * as published by the Free Software Foundation; either version
15 * 2 of the License, or (at your option) any later version.
16 *
17 * Usage: addnote zImage
18 */
19#include <stdio.h>
20#include <fcntl.h>
21#include <unistd.h>
22#include <string.h>
23
24char arch[] = "PowerPC";
25
26#define N_DESCR	6
27unsigned int descr[N_DESCR] = {
28	/* values for IBM RS/6000 machines */
29	0xffffffff,		/* real-mode = true */
30	0x00c00000,		/* real-base, i.e. where we expect OF to be */
31	0xffffffff,		/* real-size */
32	0xffffffff,		/* virt-base */
33	0xffffffff,		/* virt-size */
34	0x4000,			/* load-base */
35};
36
37unsigned char buf[512];
38
39#define GET_16BE(off)	((buf[off] << 8) + (buf[(off)+1]))
40#define GET_32BE(off)	((GET_16BE(off) << 16) + GET_16BE((off)+2))
41
42#define PUT_16BE(off, v)	(buf[off] = ((v) >> 8) & 0xff, \
43				 buf[(off) + 1] = (v) & 0xff)
44#define PUT_32BE(off, v)	(PUT_16BE((off), (v) >> 16), \
45				 PUT_16BE((off) + 2, (v)))
46
47/* Structure of an ELF file */
48#define E_IDENT		0	/* ELF header */
49#define	E_PHOFF		28
50#define E_PHENTSIZE	42
51#define E_PHNUM		44
52#define E_HSIZE		52	/* size of ELF header */
53
54#define EI_MAGIC	0	/* offsets in E_IDENT area */
55#define EI_CLASS	4
56#define EI_DATA		5
57
58#define PH_TYPE		0	/* ELF program header */
59#define PH_OFFSET	4
60#define PH_FILESZ	16
61#define PH_HSIZE	32	/* size of program header */
62
63#define PT_NOTE		4	/* Program header type = note */
64
65#define ELFCLASS32	1
66#define ELFDATA2MSB	2
67
68unsigned char elf_magic[4] = { 0x7f, 'E', 'L', 'F' };
69
70int main(int ac, char **av)
71{
72	int fd, n, i;
73	int ph, ps, np;
74	int nnote, ns;
75
76	if (ac != 2) {
77		fprintf(stderr, "Usage: %s elf-file\n", av[0]);
78		exit(1);
79	}
80	fd = open(av[1], O_RDWR);
81	if (fd < 0) {
82		perror(av[1]);
83		exit(1);
84	}
85
86	nnote = strlen(arch) + 1 + (N_DESCR + 3) * 4;
87
88	n = read(fd, buf, sizeof(buf));
89	if (n < 0) {
90		perror("read");
91		exit(1);
92	}
93
94	if (n < E_HSIZE || memcmp(&buf[E_IDENT+EI_MAGIC], elf_magic, 4) != 0)
95		goto notelf;
96
97	if (buf[E_IDENT+EI_CLASS] != ELFCLASS32
98	    || buf[E_IDENT+EI_DATA] != ELFDATA2MSB) {
99		fprintf(stderr, "%s is not a big-endian 32-bit ELF image\n",
100			av[1]);
101		exit(1);
102	}
103
104	ph = GET_32BE(E_PHOFF);
105	ps = GET_16BE(E_PHENTSIZE);
106	np = GET_16BE(E_PHNUM);
107	if (ph < E_HSIZE || ps < PH_HSIZE || np < 1)
108		goto notelf;
109	if (ph + (np + 1) * ps + nnote > n)
110		goto nospace;
111
112	for (i = 0; i < np; ++i) {
113		if (GET_32BE(ph + PH_TYPE) == PT_NOTE) {
114			fprintf(stderr, "%s already has a note entry\n",
115				av[1]);
116			exit(0);
117		}
118		ph += ps;
119	}
120
121	for (i = 0; i < ps + nnote; ++i)
122		if (buf[ph + i] != 0)
123			goto nospace;
124
125	/* fill in the program header entry */
126	ns = ph + ps;
127	PUT_32BE(ph + PH_TYPE, PT_NOTE);
128	PUT_32BE(ph + PH_OFFSET, ns);
129	PUT_32BE(ph + PH_FILESZ, nnote);
130
131	/* fill in the note area we point to */
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