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 #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 __unused)
157 {
158 Elf_Ehdr eh;
159 struct stat sb;
160 unsigned char data;
161
162 /*
163 * Check the header to make 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_S390: break;
195 case EM_SPARCV9: break;
196 case EM_X86_64: break;
197 /* ELFDEFNNAME(MACHDEP_ID_CASES) */
198
199 default:
200 return 0;
201 }
202
203 return 1;
204 }
205
206 /*
207 * This function 'hides' (some of) ELF executable file's symbols.
208 * It hides them by renaming them to "_$$hide$$ <filename> <symbolname>".
209 * Symbols in the global keep list, or which are marked as being undefined,
210 * are left alone.
211 *
212 * An old version of this code shuffled various tables around, turning
213 * global symbols to be hidden into local symbols. That lost on the
214 * mips, because CALL16 relocs must reference global symbols, and, if
215 * those symbols were being hidden, they were no longer global.
216 *
217 * The new renaming behaviour doesn't take global symbols out of the
218 * namespace. However, it's ... unlikely that there will ever be
219 * any collisions in practice because of the new method.
220 */
221 int
ELFNAMEEND(hide)222 ELFNAMEEND(hide)(int fd, const char *fn)
223 {
224 Elf_Ehdr ehdr;
225 struct shlayout *layoutp = NULL;
226 Elf_Shdr *shdrp = NULL, *symtabshdr, *strtabshdr, *shstrtabshdr;
227 Elf_Shdr shdrshdr;
228 Elf_Sym *symtabp = NULL;
229 char *shstrtabp = NULL, *strtabp = NULL;
230 Elf_Size nsyms, ewi;
231 Elf_Off off;
232 ssize_t shdrsize;
233 int rv, i, weird, l, m, r, strtabidx;
234 size_t nstrtab_size, nstrtab_nextoff, fn_size, size;
235 char *nstrtabp = NULL;
236 unsigned char data;
237 const char *weirdreason = NULL;
238 void *buf;
239 Elf_Half shnum;
240
241 rv = 0;
242 if (xreadatoff(fd, &ehdr, 0, sizeof ehdr, fn) != sizeof ehdr)
243 goto bad;
244
245 data = ehdr.e_ident[EI_DATA];
246 shnum = xe16toh(ehdr.e_shnum);
247
248 shdrsize = shnum * xe16toh(ehdr.e_shentsize);
249 if ((shdrp = xmalloc(shdrsize, fn, "section header table")) == NULL)
250 goto bad;
251 if (xreadatoff(fd, shdrp, xewtoh(ehdr.e_shoff), shdrsize, fn) !=
252 shdrsize)
253 goto bad;
254
255 symtabshdr = strtabshdr = shstrtabshdr = NULL;
256 weird = 0;
257 for (i = 0; i < shnum; i++) {
258 switch (xe32toh(shdrp[i].sh_type)) {
259 case SHT_SYMTAB:
260 if (symtabshdr != NULL) {
261 weird = 1;
262 weirdreason = "multiple symbol tables";
263 }
264 symtabshdr = &shdrp[i];
265 strtabshdr = &shdrp[xe32toh(shdrp[i].sh_link)];
266 break;
267 case SHT_STRTAB:
268 if (i == xe16toh(ehdr.e_shstrndx))
269 shstrtabshdr = &shdrp[i];
270 break;
271 }
272 }
273 if (symtabshdr == NULL)
274 goto out;
275 if (strtabshdr == NULL) {
276 weird = 1;
277 weirdreason = "string table does not exist";
278 }
279 if (shstrtabshdr == NULL) {
280 weird = 1;
281 weirdreason = "section header string table does not exist";
282 }
283 if (strtabshdr == shstrtabshdr) {
284 weird = 1;
285 weirdreason = "combined strtab and shstrtab not supported";
286 }
287 if (weirdreason == NULL)
288 weirdreason = "unsupported";
289 if (weird) {
290 fprintf(stderr, "%s: weird executable (%s)\n", fn, weirdreason);
291 goto bad;
292 }
293
294 /*
295 * sort section layout table by offset
296 */
297 layoutp = xmalloc((shnum + 1) * sizeof(struct shlayout),
298 fn, "layout table");
299 if (layoutp == NULL)
300 goto bad;
301
302 /* add a pseudo entry to represent the section header table */
303 shdrshdr.sh_offset = ehdr.e_shoff;
304 shdrshdr.sh_size = htoxew(shdrsize);
305 shdrshdr.sh_addralign = htoxew(ELFSIZE / 8);
306 layoutp[shnum].shdr = &shdrshdr;
307
308 /* insert and sort normal section headers */
309 for (i = shnum; i-- != 0;) {
310 l = i + 1;
311 r = shnum;
312 while (l <= r) {
313 m = ( l + r) / 2;
314 if (xewtoh(shdrp[i].sh_offset) >
315 xewtoh(layoutp[m].shdr->sh_offset))
316 l = m + 1;
317 else
318 r = m - 1;
319 }
320
321 if (r != i) {
322 memmove(&layoutp[i], &layoutp[i + 1],
323 sizeof(struct shlayout) * (r - i));
324 }
325
326 layoutp[r].shdr = &shdrp[i];
327 layoutp[r].bufp = NULL;
328 }
329 ++shnum;
330
331 /*
332 * load up everything we need
333 */
334
335 /* load section string table for debug use */
336 if ((size = xewtoh(shstrtabshdr->sh_size)) == 0)
337 goto bad;
338 if ((shstrtabp = xmalloc(size, fn, "section string table")) == NULL)
339 goto bad;
340 if ((size_t)xreadatoff(fd, shstrtabp, xewtoh(shstrtabshdr->sh_offset),
341 size, fn) != size)
342 goto bad;
343 if (shstrtabp[size - 1] != '\0')
344 goto bad;
345
346 /* we need symtab, strtab, and everything behind strtab */
347 strtabidx = INT_MAX;
348 for (i = 0; i < shnum; i++) {
349 if (layoutp[i].shdr == &shdrshdr) {
350 /* not load section header again */
351 layoutp[i].bufp = shdrp;
352 continue;
353 }
354 if (layoutp[i].shdr == shstrtabshdr) {
355 /* not load section string table again */
356 layoutp[i].bufp = shstrtabp;
357 continue;
358 }
359
360 if (layoutp[i].shdr == strtabshdr)
361 strtabidx = i;
362 if (layoutp[i].shdr == symtabshdr || i >= strtabidx) {
363 off = xewtoh(layoutp[i].shdr->sh_offset);
364 if ((size = xewtoh(layoutp[i].shdr->sh_size)) == 0)
365 goto bad;
366 layoutp[i].bufp = xmalloc(size, fn,
367 shstrtabp + xewtoh(layoutp[i].shdr->sh_name));
368 if (layoutp[i].bufp == NULL)
369 goto bad;
370 if ((size_t)xreadatoff(fd, layoutp[i].bufp, off, size, fn) !=
371 size)
372 goto bad;
373
374 /* set symbol table and string table */
375 if (layoutp[i].shdr == symtabshdr) {
376 symtabp = layoutp[i].bufp;
377 } else if (layoutp[i].shdr == strtabshdr) {
378 strtabp = layoutp[i].bufp;
379 if (strtabp[size - 1] != '\0')
380 goto bad;
381 }
382 }
383 }
384
385 nstrtab_size = 256;
386 nstrtabp = xmalloc(nstrtab_size, fn, "new string table");
387 if (nstrtabp == NULL)
388 goto bad;
389 nstrtab_nextoff = 0;
390
391 fn_size = strlen(fn);
392
393 /* Prepare data structures for symbol movement. */
394 nsyms = xewtoh(symtabshdr->sh_size) / xewtoh(symtabshdr->sh_entsize);
395
396 /* move symbols, making them local */
397 for (ewi = 0; ewi < nsyms; ewi++) {
398 Elf_Sym *sp = &symtabp[ewi];
399 const char *symname = strtabp + xe32toh(sp->st_name);
400 size_t newent_len;
401 /*
402 * make sure there's size for the next entry, even if it's
403 * as large as it can be.
404 *
405 * "_$$hide$$ <filename> <symname><NUL>" ->
406 * 9 + 3 + sizes of fn and sym name
407 */
408 while ((nstrtab_size - nstrtab_nextoff) <
409 strlen(symname) + fn_size + 12) {
410 nstrtab_size *= 2;
411 nstrtabp = xrealloc(nstrtabp, nstrtab_size, fn,
412 "new string table");
413 if (nstrtabp == NULL)
414 goto bad;
415 }
416
417 sp->st_name = htowew(nstrtab_nextoff);
418
419 /* if it's a keeper or is undefined, don't rename it. */
420 if (in_keep_list(symname) ||
421 (xe16toh(sp->st_shndx) == SHN_UNDEF)) {
422 newent_len = sprintf(nstrtabp + nstrtab_nextoff,
423 "%s", symname) + 1;
424 } else {
425 newent_len = sprintf(nstrtabp + nstrtab_nextoff,
426 "_$$hide$$ %s %s", fn, symname) + 1;
427 }
428 nstrtab_nextoff += newent_len;
429 }
430 strtabshdr->sh_size = htoxew(nstrtab_nextoff);
431
432 /*
433 * update section header table in ascending order of offset
434 */
435 for (i = strtabidx + 1; i < shnum; i++) {
436 Elf_Off soff, align;
437 soff = xewtoh(layoutp[i - 1].shdr->sh_offset) +
438 xewtoh(layoutp[i - 1].shdr->sh_size);
439 align = xewtoh(layoutp[i].shdr->sh_addralign);
440 soff = (soff + (align - 1)) & ~(align - 1);
441 layoutp[i].shdr->sh_offset = htoxew(soff);
442 }
443
444 /*
445 * write data to the file in descending order of offset
446 */
447 for (i = shnum; i-- != 0;) {
448 if (layoutp[i].shdr == strtabshdr) {
449 /* new string table */
450 buf = nstrtabp;
451 } else
452 buf = layoutp[i].bufp;
453
454 if (layoutp[i].shdr == &shdrshdr ||
455 layoutp[i].shdr == symtabshdr || i >= strtabidx) {
456 if (buf == NULL)
457 goto bad;
458
459 /*
460 * update the offset of section header table in elf
461 * header if needed.
462 */
463 if (layoutp[i].shdr == &shdrshdr &&
464 ehdr.e_shoff != shdrshdr.sh_offset) {
465 ehdr.e_shoff = shdrshdr.sh_offset;
466 off = offsetof(Elf_Ehdr, e_shoff);
467 size = sizeof(Elf_Off);
468 if ((size_t)xwriteatoff(fd, &ehdr.e_shoff, off, size,
469 fn) != size)
470 goto bad;
471 }
472
473 off = xewtoh(layoutp[i].shdr->sh_offset);
474 size = xewtoh(layoutp[i].shdr->sh_size);
475 if ((size_t)xwriteatoff(fd, buf, off, size, fn) != size)
476 goto bad;
477 }
478 }
479
480 out:
481 if (layoutp != NULL) {
482 for (i = 0; i < shnum; i++) {
483 if (layoutp[i].bufp != NULL)
484 free(layoutp[i].bufp);
485 }
486 free(layoutp);
487 }
488 free(nstrtabp);
489 return (rv);
490
491 bad:
492 rv = 1;
493 goto out;
494 }
495
496 #endif /* include this size of ELF */
497