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/* CHRP note section */
 23static const char arch[] = "PowerPC";
 24
 25#define N_DESCR	6
 26unsigned int descr[N_DESCR] = {
 27	0xffffffff,		/* real-mode = true */
 28	0x02000000,		/* 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};
 34
 35/* RPA note section */
 36static const char rpaname[] = "IBM,RPA-Client-Config";
 37
 38/*
 39 * Note: setting ignore_my_client_config *should* mean that OF ignores
 40 * all the other fields, but there is a firmware bug which means that
 41 * it looks at the splpar field at least.  So these values need to be
 42 * reasonable.
 43 */
 44#define N_RPA_DESCR	8
 45unsigned int rpanote[N_RPA_DESCR] = {
 46	0,			/* lparaffinity */
 47	64,			/* min_rmo_size */
 48	0,			/* min_rmo_percent */
 49	40,			/* max_pft_size */
 50	1,			/* splpar */
 51	-1,			/* min_load */
 52	0,			/* new_mem_def */
 53	1,			/* ignore_my_client_config */
 54};
 55
 56#define ROUNDUP(len)	(((len) + 3) & ~3)
 57
 58unsigned char buf[512];
 59
 60#define GET_16BE(off)	((buf[off] << 8) + (buf[(off)+1]))
 61#define GET_32BE(off)	((GET_16BE(off) << 16) + GET_16BE((off)+2))
 62
 63#define PUT_16BE(off, v)	(buf[off] = ((v) >> 8) & 0xff, \
 64				 buf[(off) + 1] = (v) & 0xff)
 65#define PUT_32BE(off, v)	(PUT_16BE((off), (v) >> 16), \
 66				 PUT_16BE((off) + 2, (v)))
 67
 68/* Structure of an ELF file */
 69#define E_IDENT		0	/* ELF header */
 70#define	E_PHOFF		28
 71#define E_PHENTSIZE	42
 72#define E_PHNUM		44
 73#define E_HSIZE		52	/* size of ELF header */
 74
 75#define EI_MAGIC	0	/* offsets in E_IDENT area */
 76#define EI_CLASS	4
 77#define EI_DATA		5
 78
 79#define PH_TYPE		0	/* ELF program header */
 80#define PH_OFFSET	4
 81#define PH_FILESZ	16
 82#define PH_HSIZE	32	/* size of program header */
 83
 84#define PT_NOTE		4	/* Program header type = note */
 85
 86#define ELFCLASS32	1
 87#define ELFDATA2MSB	2
 88
 89unsigned char elf_magic[4] = { 0x7f, 'E', 'L', 'F' };
 90
 91int
 92main(int ac, char **av)
 93{
 94	int fd, n, i;
 95	int ph, ps, np;
 96	int nnote, nnote2, ns;
 97
 98	if (ac != 2) {
 99		fprintf(stderr, "Usage: %s elf-file\n", av[0]);
100		exit(1);
101	}
102	fd = open(av[1], O_RDWR);
103	if (fd < 0) {
104		perror(av[1]);
105		exit(1);
106	}
107
108	nnote = 12 + ROUNDUP(strlen(arch) + 1) + sizeof(descr);
109	nnote2 = 12 + ROUNDUP(strlen(rpaname) + 1) + sizeof(rpanote);
110
111	n = read(fd, buf, sizeof(buf));
112	if (n < 0) {
113		perror("read");
114		exit(1);
115	}
116
117	if (n < E_HSIZE || memcmp(&buf[E_IDENT+EI_MAGIC], elf_magic, 4) != 0)
118		goto notelf;
119
120	if (buf[E_IDENT+EI_CLASS] != ELFCLASS32
121	    || buf[E_IDENT+EI_DATA] != ELFDATA2MSB) {
122		fprintf(stderr, "%s is not a big-endian 32-bit ELF image\n",
123			av[1]);
124		exit(1);
125	}
126
127	ph = GET_32BE(E_PHOFF);
128	ps = GET_16BE(E_PHENTSIZE);
129	np = GET_16BE(E_PHNUM);
130	if (ph < E_HSIZE || ps < PH_HSIZE || np < 1)
131		goto notelf;
132	if (ph + (np + 2) * ps + nnote + nnote2 > n)
133		goto nospace;
134
135	for (i = 0; i < np; ++i) {
136		if (GET_32BE(ph + PH_TYPE) == PT_NOTE) {
137			fprintf(stderr, "%s already has a note entry\n",
138				av[1]);
139			exit(0);
140		}
141		ph += ps;
142	}
143
144	/* XXX check that the area we want to use is all zeroes */
145	for (i = 0; i < 2 * ps + nnote + nnote2; ++i)
146		if (buf[ph + i] != 0)
147			goto nospace;
148
149	/* fill in the program header entry */
150	ns = ph + 2 * ps;
151	PUT_32BE(ph + PH_TYPE, PT_NOTE);
152	PUT_32BE(ph + PH_OFFSET, ns);
153	PUT_32BE(ph + PH_FILESZ, nnote);
154
155	/* fill in the note area we point to */
156	/* XXX we should probably make this a proper section */
157	PUT_32BE(ns, strlen(arch) + 1);
158	PUT_32BE(ns + 4, N_DESCR * 4);
159	PUT_32BE(ns + 8, 0x1275);
160	strcpy((char *) &buf[ns + 12], arch);
161	ns += 12 + strlen(arch) + 1;
162	for (i = 0; i < N_DESCR; ++i, ns += 4)
163		PUT_32BE(ns, descr[i]);
164
165	/* fill in the second program header entry and the RPA note area */
166	ph += ps;
167	PUT_32BE(ph + PH_TYPE, PT_NOTE);
168	PUT_32BE(ph + PH_OFFSET, ns);
169	PUT_32BE(ph + PH_FILESZ, nnote2);
170
171	/* fill in the note area we point to */
172	PUT_32BE(ns, strlen(rpaname) + 1);
173	PUT_32BE(ns + 4, sizeof(rpanote));
174	PUT_32BE(ns + 8, 0x12759999);
175	strcpy((char *) &buf[ns + 12], rpaname);
176	ns += 12 + ROUNDUP(strlen(rpaname) + 1);
177	for (i = 0; i < N_RPA_DESCR; ++i, ns += 4)
178		PUT_32BE(ns, rpanote[i]);
179
180	/* Update the number of program headers */
181	PUT_16BE(E_PHNUM, np + 2);
182
183	/* write back */
184	lseek(fd, (long) 0, SEEK_SET);
185	i = write(fd, buf, n);
186	if (i < 0) {
187		perror("write");
188		exit(1);
189	}
190	if (i < n) {
191		fprintf(stderr, "%s: write truncated\n", av[1]);
192		exit(1);
193	}
194
195	exit(0);
196
197 notelf:
198	fprintf(stderr, "%s does not appear to be an ELF file\n", av[1]);
199	exit(1);
200
201 nospace:
202	fprintf(stderr, "sorry, I can't find space in %s to put the note\n",
203		av[1]);
204	exit(1);
205}