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, *outf;
60 long total_len;
61 const char *prefix = "vdso";
62 const char *inf_name;
63 const char *outf_name = NULL;
64 unsigned char *buf;
65 bool need_bswap;
66
67 while (1) {
68 int opt = getopt(argc, argv, "o:p:r:s:");
69 if (opt < 0) {
70 break;
71 }
72 switch (opt) {
73 case 'o':
74 outf_name = optarg;
75 break;
76 case 'p':
77 prefix = optarg;
78 break;
79 case 'r':
80 rt_sigreturn_sym = optarg;
81 break;
82 case 's':
83 sigreturn_sym = optarg;
84 break;
85 default:
86 usage:
87 fprintf(stderr, "usage: [-p prefix] [-r rt-sigreturn-name] "
88 "[-s sigreturn-name] -o output-file input-file\n");
89 return EXIT_FAILURE;
90 }
91 }
92
93 if (optind >= argc || outf_name == NULL) {
94 goto usage;
95 }
96 inf_name = argv[optind];
97
98 /*
99 * Open the input and output files.
100 */
101 inf = fopen(inf_name, "rb");
102 if (inf == NULL) {
103 goto perror_inf;
104 }
105 outf = fopen(outf_name, "w");
106 if (outf == NULL) {
107 goto perror_outf;
108 }
109
110 /*
111 * Read the input file into a buffer.
112 * We expect the vdso to be small, on the order of one page,
113 * therefore we do not expect a partial read.
114 */
115 fseek(inf, 0, SEEK_END);
116 total_len = ftell(inf);
117 fseek(inf, 0, SEEK_SET);
118
119 buf = malloc(total_len);
120 if (buf == NULL) {
121 goto perror_inf;
122 }
123
124 errno = 0;
125 if (fread(buf, 1, total_len, inf) != total_len) {
126 if (errno) {
127 goto perror_inf;
128 }
129 fprintf(stderr, "%s: incomplete read\n", inf_name);
130 return EXIT_FAILURE;
131 }
132 fclose(inf);
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 /*
209 * Everything should have gone well.
210 */
211 if (fclose(outf)) {
212 goto perror_outf;
213 }
214 return EXIT_SUCCESS;
215
216 perror_inf:
217 perror(inf_name);
218 return EXIT_FAILURE;
219
220 perror_outf:
221 perror(outf_name);
222 return EXIT_FAILURE;
223 }
224