1 /*
2 * Post-process a vdso elf image for inclusion into qemu.
3 *
4 * Copyright 2023 Linaro, Ltd.
5 *
6 * SPDX-License-Identifier: GPL-2.0-or-later
7 */
8
9 #include <stdlib.h>
10 #include <stdbool.h>
11 #include <stdint.h>
12 #include <stdio.h>
13 #include <string.h>
14 #include <errno.h>
15 #include <endian.h>
16 #include <unistd.h>
17 #include "elf.h"
18
19
20 #define bswap_(p) _Generic(*(p), \
21 uint16_t: __builtin_bswap16, \
22 uint32_t: __builtin_bswap32, \
23 uint64_t: __builtin_bswap64, \
24 int16_t: __builtin_bswap16, \
25 int32_t: __builtin_bswap32, \
26 int64_t: __builtin_bswap64)
27 #define bswaps(p) (*(p) = bswap_(p)(*(p)))
28
output_reloc(FILE * outf,void * buf,void * loc)29 static void output_reloc(FILE *outf, void *buf, void *loc)
30 {
31 fprintf(outf, " 0x%08tx,\n", loc - buf);
32 }
33
34 static const char *sigreturn_sym;
35 static const char *rt_sigreturn_sym;
36
37 static unsigned sigreturn_addr;
38 static unsigned rt_sigreturn_addr;
39
40 #define N 32
41 #define elfN(x) elf32_##x
42 #define ElfN(x) Elf32_##x
43 #include "gen-vdso-elfn.c.inc"
44 #undef N
45 #undef elfN
46 #undef ElfN
47
48 #define N 64
49 #define elfN(x) elf64_##x
50 #define ElfN(x) Elf64_##x
51 #include "gen-vdso-elfn.c.inc"
52 #undef N
53 #undef elfN
54 #undef ElfN
55
56
main(int argc,char ** argv)57 int main(int argc, char **argv)
58 {
59 FILE *inf = NULL, *outf = NULL;
60 long total_len;
61 const char *prefix = "vdso";
62 const char *inf_name;
63 const char *outf_name = NULL;
64 unsigned char *buf = NULL;
65 bool need_bswap;
66 int ret = EXIT_FAILURE;
67
68 while (1) {
69 int opt = getopt(argc, argv, "o:p:r:s:");
70 if (opt < 0) {
71 break;
72 }
73 switch (opt) {
74 case 'o':
75 outf_name = optarg;
76 break;
77 case 'p':
78 prefix = optarg;
79 break;
80 case 'r':
81 rt_sigreturn_sym = optarg;
82 break;
83 case 's':
84 sigreturn_sym = optarg;
85 break;
86 default:
87 usage:
88 fprintf(stderr, "usage: [-p prefix] [-r rt-sigreturn-name] "
89 "[-s sigreturn-name] -o output-file input-file\n");
90 return EXIT_FAILURE;
91 }
92 }
93
94 if (optind >= argc || outf_name == NULL) {
95 goto usage;
96 }
97 inf_name = argv[optind];
98
99 /*
100 * Open the input and output files.
101 */
102 inf = fopen(inf_name, "rb");
103 if (inf == NULL) {
104 goto perror_inf;
105 }
106 outf = fopen(outf_name, "w");
107 if (outf == NULL) {
108 goto perror_outf;
109 }
110
111 /*
112 * Read the input file into a buffer.
113 * We expect the vdso to be small, on the order of one page,
114 * therefore we do not expect a partial read.
115 */
116 fseek(inf, 0, SEEK_END);
117 total_len = ftell(inf);
118 fseek(inf, 0, SEEK_SET);
119
120 buf = malloc(total_len);
121 if (buf == NULL) {
122 goto perror_inf;
123 }
124
125 errno = 0;
126 if (fread(buf, 1, total_len, inf) != total_len) {
127 if (errno) {
128 goto perror_inf;
129 }
130 fprintf(stderr, "%s: incomplete read\n", inf_name);
131 return EXIT_FAILURE;
132 }
133
134 /*
135 * Identify which elf flavor we're processing.
136 * The first 16 bytes of the file are e_ident.
137 */
138
139 if (buf[EI_MAG0] != ELFMAG0 || buf[EI_MAG1] != ELFMAG1 ||
140 buf[EI_MAG2] != ELFMAG2 || buf[EI_MAG3] != ELFMAG3) {
141 fprintf(stderr, "%s: not an elf file\n", inf_name);
142 return EXIT_FAILURE;
143 }
144 switch (buf[EI_DATA]) {
145 case ELFDATA2LSB:
146 need_bswap = BYTE_ORDER != LITTLE_ENDIAN;
147 break;
148 case ELFDATA2MSB:
149 need_bswap = BYTE_ORDER != BIG_ENDIAN;
150 break;
151 default:
152 fprintf(stderr, "%s: invalid elf EI_DATA (%u)\n",
153 inf_name, buf[EI_DATA]);
154 return EXIT_FAILURE;
155 }
156
157 /*
158 * We need to relocate the VDSO image. The one built into the kernel
159 * is built for a fixed address. The one we built for QEMU is not,
160 * since that requires close control of the guest address space.
161 *
162 * Output relocation addresses as we go.
163 */
164
165 fprintf(outf,
166 "/* Automatically generated by linux-user/gen-vdso.c. */\n"
167 "\n"
168 "static const unsigned %s_relocs[] = {\n", prefix);
169
170 switch (buf[EI_CLASS]) {
171 case ELFCLASS32:
172 elf32_process(outf, buf, total_len, need_bswap);
173 break;
174 case ELFCLASS64:
175 elf64_process(outf, buf, total_len, need_bswap);
176 break;
177 default:
178 fprintf(stderr, "%s: invalid elf EI_CLASS (%u)\n",
179 inf_name, buf[EI_CLASS]);
180 return EXIT_FAILURE;
181 }
182
183 fprintf(outf, "};\n\n"); /* end vdso_relocs. */
184
185 /*
186 * Write out the vdso image now, after we made local changes.
187 */
188 fprintf(outf,
189 "static const uint8_t %s_image[] = {",
190 prefix);
191 for (long i = 0; i < total_len; ++i) {
192 if (i % 12 == 0) {
193 fputs("\n ", outf);
194 }
195 fprintf(outf, " 0x%02x,", buf[i]);
196 }
197 fprintf(outf, "\n};\n\n");
198
199 fprintf(outf, "static const VdsoImageInfo %s_image_info = {\n", prefix);
200 fprintf(outf, " .image = %s_image,\n", prefix);
201 fprintf(outf, " .relocs = %s_relocs,\n", prefix);
202 fprintf(outf, " .image_size = sizeof(%s_image),\n", prefix);
203 fprintf(outf, " .reloc_count = ARRAY_SIZE(%s_relocs),\n", prefix);
204 fprintf(outf, " .sigreturn_ofs = 0x%x,\n", sigreturn_addr);
205 fprintf(outf, " .rt_sigreturn_ofs = 0x%x,\n", rt_sigreturn_addr);
206 fprintf(outf, "};\n");
207
208 ret = EXIT_SUCCESS;
209
210 cleanup:
211 free(buf);
212
213 if (outf && fclose(outf) != 0) {
214 ret = EXIT_FAILURE;
215 }
216 if (inf && fclose(inf) != 0) {
217 ret = EXIT_FAILURE;
218 }
219 return ret;
220
221 perror_inf:
222 perror(inf_name);
223 goto cleanup;
224
225 perror_outf:
226 perror(outf_name);
227 goto cleanup;
228 }
229