1 /*-
2 * SPDX-License-Identifier: BSD-4-Clause
3 *
4 * Copyright (c) 1997 Christopher G. Demetriou. All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * 3. All advertising materials mentioning features or use of this software
15 * must display the following acknowledgement:
16 * This product includes software developed by Christopher G. Demetriou
17 * for the NetBSD Project.
18 * 4. The name of the author may not be used to endorse or promote products
19 * derived from this software without specific prior written permission
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
22 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
23 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
24 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
25 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
26 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
30 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31 */
32
33 #include <sys/cdefs.h>
34 #ifndef lint
35 #if 0
36 __RCSID("$NetBSD: exec_elf32.c,v 1.6 1999/09/20 04:12:16 christos Exp $");
37 #endif
38 #endif
39 __FBSDID("$FreeBSD$");
40
41 #ifndef ELFSIZE
42 #define ELFSIZE 32
43 #endif
44
45 #include <sys/types.h>
46 #include <sys/endian.h>
47 #include <sys/stat.h>
48
49 #include <errno.h>
50 #include <limits.h>
51 #include <stddef.h>
52 #include <stdio.h>
53 #include <stdlib.h>
54 #include <string.h>
55 #include <unistd.h>
56
57 #include "extern.h"
58
59 #if (defined(NLIST_ELF32) && (ELFSIZE == 32)) || \
60 (defined(NLIST_ELF64) && (ELFSIZE == 64))
61
62 #define __ELF_WORD_SIZE ELFSIZE
63 #if (ELFSIZE == 32)
64 #include <sys/elf32.h>
65 #define xewtoh(x) ((data == ELFDATA2MSB) ? be32toh(x) : le32toh(x))
66 #define htoxew(x) ((data == ELFDATA2MSB) ? htobe32(x) : htole32(x))
67 #define wewtoh(x) ((data == ELFDATA2MSB) ? be32toh(x) : le32toh(x))
68 #define htowew(x) ((data == ELFDATA2MSB) ? htobe32(x) : htole32(x))
69 #elif (ELFSIZE == 64)
70 #include <sys/elf64.h>
71 #define xewtoh(x) ((data == ELFDATA2MSB) ? be64toh(x) : le64toh(x))
72 #define htoxew(x) ((data == ELFDATA2MSB) ? htobe64(x) : htole64(x))
73 /* elf64 Elf64_Word are 32 bits */
74 #define wewtoh(x) ((data == ELFDATA2MSB) ? be32toh(x) : le32toh(x))
75 #define htowew(x) ((data == ELFDATA2MSB) ? htobe32(x) : htole32(x))
76 #endif
77 #include <sys/elf_generic.h>
78
79 #define CONCAT(x,y) __CONCAT(x,y)
80 #define ELFNAME(x) CONCAT(elf,CONCAT(ELFSIZE,CONCAT(_,x)))
81 #define ELFNAME2(x,y) CONCAT(x,CONCAT(_elf,CONCAT(ELFSIZE,CONCAT(_,y))))
82 #define ELFNAMEEND(x) CONCAT(x,CONCAT(_elf,ELFSIZE))
83 #define ELFDEFNNAME(x) CONCAT(ELF,CONCAT(ELFSIZE,CONCAT(_,x)))
84 #ifndef ELFCLASS
85 #define ELFCLASS CONCAT(ELFCLASS,ELFSIZE)
86 #endif
87
88 #define xe16toh(x) ((data == ELFDATA2MSB) ? be16toh(x) : le16toh(x))
89 #define xe32toh(x) ((data == ELFDATA2MSB) ? be32toh(x) : le32toh(x))
90 #define htoxe32(x) ((data == ELFDATA2MSB) ? htobe32(x) : htole32(x))
91
92 struct shlayout {
93 Elf_Shdr *shdr;
94 void *bufp;
95 };
96
97 static ssize_t
xreadatoff(int fd,void * buf,off_t off,size_t size,const char * fn)98 xreadatoff(int fd, void *buf, off_t off, size_t size, const char *fn)
99 {
100 ssize_t rv;
101
102 if (lseek(fd, off, SEEK_SET) != off) {
103 perror(fn);
104 return -1;
105 }
106 if ((size_t)(rv = read(fd, buf, size)) != size) {
107 fprintf(stderr, "%s: read error: %s\n", fn,
108 rv == -1 ? strerror(errno) : "short read");
109 return -1;
110 }
111 return size;
112 }
113
114 static ssize_t
xwriteatoff(int fd,void * buf,off_t off,size_t size,const char * fn)115 xwriteatoff(int fd, void *buf, off_t off, size_t size, const char *fn)
116 {
117 ssize_t rv;
118
119 if (lseek(fd, off, SEEK_SET) != off) {
120 perror(fn);
121 return -1;
122 }
123 if ((size_t)(rv = write(fd, buf, size)) != size) {
124 fprintf(stderr, "%s: write error: %s\n", fn,
125 rv == -1 ? strerror(errno) : "short write");
126 return -1;
127 }
128 return size;
129 }
130
131 static void *
xmalloc(size_t size,const char * fn,const char * use)132 xmalloc(size_t size, const char *fn, const char *use)
133 {
134 void *rv;
135
136 rv = malloc(size);
137 if (rv == NULL)
138 fprintf(stderr, "%s: out of memory (allocating for %s)\n",
139 fn, use);
140 return (rv);
141 }
142
143 static void *
xrealloc(void * ptr,size_t size,const char * fn,const char * use)144 xrealloc(void *ptr, size_t size, const char *fn, const char *use)
145 {
146 void *rv;
147
148 rv = realloc(ptr, size);
149 if (rv == NULL) {
150 free(ptr);
151 fprintf(stderr, "%s: out of memory (reallocating for %s)\n",
152 fn, use);
153 }
154 return (rv);
155 }
156
157 int
ELFNAMEEND(check)158 ELFNAMEEND(check)(int fd, const char *fn __unused)
159 {
160 Elf_Ehdr eh;
161 struct stat sb;
162 unsigned char data;
163
164 /*
165 * Check the header to maek sure it's an ELF file (of the
166 * appropriate size).
167 */
168 if (fstat(fd, &sb) == -1)
169 return 0;
170 if (sb.st_size < (off_t)(sizeof eh))
171 return 0;
172 if (read(fd, &eh, sizeof eh) != sizeof eh)
173 return 0;
174
175 if (IS_ELF(eh) == 0 || eh.e_ident[EI_CLASS] != ELFCLASS)
176 return 0;
177
178 data = eh.e_ident[EI_DATA];
179
180 switch (xe16toh(eh.e_machine)) {
181 case EM_386: break;
182 case EM_ALPHA: break;
183 #ifndef EM_AARCH64
184 #define EM_AARCH64 183
185 #endif
186 case EM_AARCH64: break;
187 case EM_ARM: break;
188 case EM_MIPS: break;
189 case /* EM_MIPS_RS3_LE */ EM_MIPS_RS4_BE: break;
190 case EM_PPC: break;
191 case EM_PPC64: break;
192 #ifndef EM_RISCV
193 #define EM_RISCV 243
194 #endif
195 case EM_RISCV: break;
196 case EM_S390: break;
197 case EM_SPARCV9: break;
198 case EM_X86_64: break;
199 /* ELFDEFNNAME(MACHDEP_ID_CASES) */
200
201 default:
202 return 0;
203 }
204
205 return 1;
206 }
207
208 /*
209 * This function 'hides' (some of) ELF executable file's symbols.
210 * It hides them by renaming them to "_$$hide$$ <filename> <symbolname>".
211 * Symbols in the global keep list, or which are marked as being undefined,
212 * are left alone.
213 *
214 * An old version of this code shuffled various tables around, turning
215 * global symbols to be hidden into local symbols. That lost on the
216 * mips, because CALL16 relocs must reference global symbols, and, if
217 * those symbols were being hidden, they were no longer global.
218 *
219 * The new renaming behaviour doesn't take global symbols out of the
220 * namespace. However, it's ... unlikely that there will ever be
221 * any collisions in practice because of the new method.
222 */
223 int
ELFNAMEEND(hide)224 ELFNAMEEND(hide)(int fd, const char *fn)
225 {
226 Elf_Ehdr ehdr;
227 struct shlayout *layoutp = NULL;
228 Elf_Shdr *shdrp = NULL, *symtabshdr, *strtabshdr, *shstrtabshdr;
229 Elf_Shdr shdrshdr;
230 Elf_Sym *symtabp = NULL;
231 char *shstrtabp = NULL, *strtabp = NULL;
232 Elf_Size nsyms, ewi;
233 Elf_Off off;
234 ssize_t shdrsize;
235 int rv, i, weird, l, m, r, strtabidx;
236 size_t nstrtab_size, nstrtab_nextoff, fn_size, size;
237 char *nstrtabp = NULL;
238 unsigned char data;
239 const char *weirdreason = NULL;
240 void *buf;
241 Elf_Half shnum;
242
243 rv = 0;
244 if (xreadatoff(fd, &ehdr, 0, sizeof ehdr, fn) != sizeof ehdr)
245 goto bad;
246
247 data = ehdr.e_ident[EI_DATA];
248 shnum = xe16toh(ehdr.e_shnum);
249
250 shdrsize = shnum * xe16toh(ehdr.e_shentsize);
251 if ((shdrp = xmalloc(shdrsize, fn, "section header table")) == NULL)
252 goto bad;
253 if (xreadatoff(fd, shdrp, xewtoh(ehdr.e_shoff), shdrsize, fn) !=
254 shdrsize)
255 goto bad;
256
257 symtabshdr = strtabshdr = shstrtabshdr = NULL;
258 weird = 0;
259 for (i = 0; i < shnum; i++) {
260 switch (xe32toh(shdrp[i].sh_type)) {
261 case SHT_SYMTAB:
262 if (symtabshdr != NULL) {
263 weird = 1;
264 weirdreason = "multiple symbol tables";
265 }
266 symtabshdr = &shdrp[i];
267 strtabshdr = &shdrp[xe32toh(shdrp[i].sh_link)];
268 break;
269 case SHT_STRTAB:
270 if (i == xe16toh(ehdr.e_shstrndx))
271 shstrtabshdr = &shdrp[i];
272 break;
273 }
274 }
275 if (symtabshdr == NULL)
276 goto out;
277 if (strtabshdr == NULL) {
278 weird = 1;
279 weirdreason = "string table does not exist";
280 }
281 if (shstrtabshdr == NULL) {
282 weird = 1;
283 weirdreason = "section header string table does not exist";
284 }
285 if (strtabshdr == shstrtabshdr) {
286 weird = 1;
287 weirdreason = "combined strtab and shstrtab not supported";
288 }
289 if (weirdreason == NULL)
290 weirdreason = "unsupported";
291 if (weird) {
292 fprintf(stderr, "%s: weird executable (%s)\n", fn, weirdreason);
293 goto bad;
294 }
295
296 /*
297 * sort section layout table by offset
298 */
299 layoutp = xmalloc((shnum + 1) * sizeof(struct shlayout),
300 fn, "layout table");
301 if (layoutp == NULL)
302 goto bad;
303
304 /* add a pseudo entry to represent the section header table */
305 shdrshdr.sh_offset = ehdr.e_shoff;
306 shdrshdr.sh_size = htoxew(shdrsize);
307 shdrshdr.sh_addralign = htoxew(ELFSIZE / 8);
308 layoutp[shnum].shdr = &shdrshdr;
309
310 /* insert and sort normal section headers */
311 for (i = shnum; i-- != 0;) {
312 l = i + 1;
313 r = shnum;
314 while (l <= r) {
315 m = ( l + r) / 2;
316 if (xewtoh(shdrp[i].sh_offset) >
317 xewtoh(layoutp[m].shdr->sh_offset))
318 l = m + 1;
319 else
320 r = m - 1;
321 }
322
323 if (r != i) {
324 memmove(&layoutp[i], &layoutp[i + 1],
325 sizeof(struct shlayout) * (r - i));
326 }
327
328 layoutp[r].shdr = &shdrp[i];
329 layoutp[r].bufp = NULL;
330 }
331 ++shnum;
332
333 /*
334 * load up everything we need
335 */
336
337 /* load section string table for debug use */
338 if ((size = xewtoh(shstrtabshdr->sh_size)) == 0)
339 goto bad;
340 if ((shstrtabp = xmalloc(size, fn, "section string table")) == NULL)
341 goto bad;
342 if ((size_t)xreadatoff(fd, shstrtabp, xewtoh(shstrtabshdr->sh_offset),
343 size, fn) != size)
344 goto bad;
345 if (shstrtabp[size - 1] != '\0')
346 goto bad;
347
348 /* we need symtab, strtab, and everything behind strtab */
349 strtabidx = INT_MAX;
350 for (i = 0; i < shnum; i++) {
351 if (layoutp[i].shdr == &shdrshdr) {
352 /* not load section header again */
353 layoutp[i].bufp = shdrp;
354 continue;
355 }
356 if (layoutp[i].shdr == shstrtabshdr) {
357 /* not load section string table again */
358 layoutp[i].bufp = shstrtabp;
359 continue;
360 }
361
362 if (layoutp[i].shdr == strtabshdr)
363 strtabidx = i;
364 if (layoutp[i].shdr == symtabshdr || i >= strtabidx) {
365 off = xewtoh(layoutp[i].shdr->sh_offset);
366 if ((size = xewtoh(layoutp[i].shdr->sh_size)) == 0)
367 goto bad;
368 layoutp[i].bufp = xmalloc(size, fn,
369 shstrtabp + xewtoh(layoutp[i].shdr->sh_name));
370 if (layoutp[i].bufp == NULL)
371 goto bad;
372 if ((size_t)xreadatoff(fd, layoutp[i].bufp, off, size, fn) !=
373 size)
374 goto bad;
375
376 /* set symbol table and string table */
377 if (layoutp[i].shdr == symtabshdr) {
378 symtabp = layoutp[i].bufp;
379 } else if (layoutp[i].shdr == strtabshdr) {
380 strtabp = layoutp[i].bufp;
381 if (strtabp[size - 1] != '\0')
382 goto bad;
383 }
384 }
385 }
386
387 nstrtab_size = 256;
388 nstrtabp = xmalloc(nstrtab_size, fn, "new string table");
389 if (nstrtabp == NULL)
390 goto bad;
391 nstrtab_nextoff = 0;
392
393 fn_size = strlen(fn);
394
395 /* Prepare data structures for symbol movement. */
396 nsyms = xewtoh(symtabshdr->sh_size) / xewtoh(symtabshdr->sh_entsize);
397
398 /* move symbols, making them local */
399 for (ewi = 0; ewi < nsyms; ewi++) {
400 Elf_Sym *sp = &symtabp[ewi];
401 const char *symname = strtabp + xe32toh(sp->st_name);
402 size_t newent_len;
403 /*
404 * make sure there's size for the next entry, even if it's
405 * as large as it can be.
406 *
407 * "_$$hide$$ <filename> <symname><NUL>" ->
408 * 9 + 3 + sizes of fn and sym name
409 */
410 while ((nstrtab_size - nstrtab_nextoff) <
411 strlen(symname) + fn_size + 12) {
412 nstrtab_size *= 2;
413 nstrtabp = xrealloc(nstrtabp, nstrtab_size, fn,
414 "new string table");
415 if (nstrtabp == NULL)
416 goto bad;
417 }
418
419 sp->st_name = htowew(nstrtab_nextoff);
420
421 /* if it's a keeper or is undefined, don't rename it. */
422 if (in_keep_list(symname) ||
423 (xe16toh(sp->st_shndx) == SHN_UNDEF)) {
424 newent_len = sprintf(nstrtabp + nstrtab_nextoff,
425 "%s", symname) + 1;
426 } else {
427 newent_len = sprintf(nstrtabp + nstrtab_nextoff,
428 "_$$hide$$ %s %s", fn, symname) + 1;
429 }
430 nstrtab_nextoff += newent_len;
431 }
432 strtabshdr->sh_size = htoxew(nstrtab_nextoff);
433
434 /*
435 * update section header table in ascending order of offset
436 */
437 for (i = strtabidx + 1; i < shnum; i++) {
438 Elf_Off soff, align;
439 soff = xewtoh(layoutp[i - 1].shdr->sh_offset) +
440 xewtoh(layoutp[i - 1].shdr->sh_size);
441 align = xewtoh(layoutp[i].shdr->sh_addralign);
442 soff = (soff + (align - 1)) & ~(align - 1);
443 layoutp[i].shdr->sh_offset = htoxew(soff);
444 }
445
446 /*
447 * write data to the file in descending order of offset
448 */
449 for (i = shnum; i-- != 0;) {
450 if (layoutp[i].shdr == strtabshdr) {
451 /* new string table */
452 buf = nstrtabp;
453 } else
454 buf = layoutp[i].bufp;
455
456 if (layoutp[i].shdr == &shdrshdr ||
457 layoutp[i].shdr == symtabshdr || i >= strtabidx) {
458 if (buf == NULL)
459 goto bad;
460
461 /*
462 * update the offset of section header table in elf
463 * header if needed.
464 */
465 if (layoutp[i].shdr == &shdrshdr &&
466 ehdr.e_shoff != shdrshdr.sh_offset) {
467 ehdr.e_shoff = shdrshdr.sh_offset;
468 off = offsetof(Elf_Ehdr, e_shoff);
469 size = sizeof(Elf_Off);
470 if ((size_t)xwriteatoff(fd, &ehdr.e_shoff, off, size,
471 fn) != size)
472 goto bad;
473 }
474
475 off = xewtoh(layoutp[i].shdr->sh_offset);
476 size = xewtoh(layoutp[i].shdr->sh_size);
477 if ((size_t)xwriteatoff(fd, buf, off, size, fn) != size)
478 goto bad;
479 }
480 }
481
482 out:
483 if (layoutp != NULL) {
484 for (i = 0; i < shnum; i++) {
485 if (layoutp[i].bufp != NULL)
486 free(layoutp[i].bufp);
487 }
488 free(layoutp);
489 }
490 free(nstrtabp);
491 return (rv);
492
493 bad:
494 rv = 1;
495 goto out;
496 }
497
498 #endif /* include this size of ELF */
499