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