1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright 1996-1998 John D. Polstra.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 */
27
28 #define _WANT_P_OSREL
29 #include <sys/param.h>
30 #include <sys/mman.h>
31 #include <sys/stat.h>
32
33 #include <errno.h>
34 #include <stddef.h>
35 #include <stdlib.h>
36 #include <string.h>
37 #include <unistd.h>
38
39 #include "debug.h"
40 #include "rtld.h"
41
42 static Elf_Ehdr *get_elf_header(int, const char *, const struct stat *,
43 Elf_Phdr **phdr);
44 static int convert_flags(int); /* Elf flags -> mmap flags */
45
46 int __getosreldate(void);
47
48 static bool
phdr_in_zero_page(const Elf_Ehdr * hdr)49 phdr_in_zero_page(const Elf_Ehdr *hdr)
50 {
51 return (hdr->e_phoff + hdr->e_phnum * sizeof(Elf_Phdr) <= page_size);
52 }
53
54 /*
55 * Map a shared object into memory. The "fd" argument is a file descriptor,
56 * which must be open on the object and positioned at its beginning.
57 * The "path" argument is a pathname that is used only for error messages.
58 *
59 * The return value is a pointer to a newly-allocated Obj_Entry structure
60 * for the shared object. Returns NULL on failure.
61 */
62 Obj_Entry *
map_object(int fd,const char * path,const struct stat * sb)63 map_object(int fd, const char *path, const struct stat *sb)
64 {
65 Obj_Entry *obj;
66 Elf_Ehdr *hdr;
67 int i;
68 Elf_Phdr *phdr;
69 Elf_Phdr *phlimit;
70 Elf_Phdr **segs;
71 int nsegs;
72 Elf_Phdr *phdyn;
73 Elf_Phdr *phinterp;
74 Elf_Phdr *phtls;
75 caddr_t mapbase;
76 size_t mapsize;
77 Elf_Addr base_vaddr;
78 Elf_Addr base_vlimit;
79 caddr_t base_addr;
80 int base_flags;
81 Elf_Off data_offset;
82 Elf_Addr data_vaddr;
83 Elf_Addr data_vlimit;
84 caddr_t data_addr;
85 int data_prot;
86 int data_flags;
87 Elf_Addr clear_vaddr;
88 caddr_t clear_addr;
89 caddr_t clear_page;
90 Elf_Addr phdr_vaddr;
91 size_t nclear, phsize;
92 Elf_Addr bss_vaddr;
93 Elf_Addr bss_vlimit;
94 caddr_t bss_addr;
95 Elf_Word stack_flags;
96 Elf_Addr note_start;
97 Elf_Addr note_end;
98 char *note_map;
99 size_t note_map_len;
100 Elf_Addr text_end;
101
102 hdr = get_elf_header(fd, path, sb, &phdr);
103 if (hdr == NULL)
104 return (NULL);
105
106 /*
107 * Scan the program header entries, and save key information.
108 * We expect that the loadable segments are ordered by load address.
109 */
110 phsize = hdr->e_phnum * sizeof(phdr[0]);
111 phlimit = phdr + hdr->e_phnum;
112 nsegs = -1;
113 phdyn = phinterp = phtls = NULL;
114 phdr_vaddr = 0;
115 note_start = 0;
116 note_end = 0;
117 note_map = NULL;
118 note_map_len = 0;
119 segs = alloca(sizeof(segs[0]) * hdr->e_phnum);
120 stack_flags = PF_X | PF_R | PF_W;
121 text_end = 0;
122 while (phdr < phlimit) {
123 switch (phdr->p_type) {
124 case PT_INTERP:
125 phinterp = phdr;
126 break;
127
128 case PT_LOAD:
129 segs[++nsegs] = phdr;
130 if ((segs[nsegs]->p_align & (page_size - 1)) != 0) {
131 _rtld_error(
132 "%s: PT_LOAD segment %d not page-aligned",
133 path, nsegs);
134 goto error;
135 }
136 if ((segs[nsegs]->p_flags & PF_X) == PF_X) {
137 text_end = MAX(text_end,
138 rtld_round_page(segs[nsegs]->p_vaddr +
139 segs[nsegs]->p_memsz));
140 }
141 break;
142
143 case PT_PHDR:
144 phdr_vaddr = phdr->p_vaddr;
145 phsize = phdr->p_memsz;
146 break;
147
148 case PT_DYNAMIC:
149 phdyn = phdr;
150 break;
151
152 case PT_TLS:
153 phtls = phdr;
154 break;
155
156 case PT_GNU_STACK:
157 stack_flags = phdr->p_flags;
158 break;
159
160 case PT_NOTE:
161 if (phdr->p_offset > page_size ||
162 phdr->p_offset + phdr->p_filesz > page_size) {
163 note_map_len = rtld_round_page(phdr->p_offset +
164 phdr->p_filesz) -
165 rtld_trunc_page(phdr->p_offset);
166 note_map = mmap(NULL, note_map_len, PROT_READ,
167 MAP_PRIVATE, fd,
168 rtld_trunc_page(phdr->p_offset));
169 if (note_map == MAP_FAILED) {
170 _rtld_error(
171 "%s: error mapping PT_NOTE (%d)",
172 path, errno);
173 goto error;
174 }
175 note_start = (Elf_Addr)(note_map +
176 phdr->p_offset -
177 rtld_trunc_page(phdr->p_offset));
178 } else {
179 note_start = (Elf_Addr)(char *)hdr +
180 phdr->p_offset;
181 }
182 note_end = note_start + phdr->p_filesz;
183 break;
184 }
185
186 ++phdr;
187 }
188 if (phdyn == NULL) {
189 _rtld_error("%s: object is not dynamically-linked", path);
190 goto error;
191 }
192
193 if (nsegs < 0) {
194 _rtld_error("%s: too few PT_LOAD segments", path);
195 goto error;
196 }
197
198 /*
199 * Map the entire address space of the object, to stake out our
200 * contiguous region, and to establish the base address for relocation.
201 */
202 base_vaddr = rtld_trunc_page(segs[0]->p_vaddr);
203 base_vlimit = rtld_round_page(segs[nsegs]->p_vaddr +
204 segs[nsegs]->p_memsz);
205 mapsize = base_vlimit - base_vaddr;
206 base_addr = (caddr_t)base_vaddr;
207 base_flags = __getosreldate() >= P_OSREL_MAP_GUARD ?
208 MAP_GUARD : MAP_PRIVATE | MAP_ANON | MAP_NOCORE;
209 if (npagesizes > 1 && rtld_round_page(segs[0]->p_filesz) >=
210 pagesizes[1])
211 base_flags |= MAP_ALIGNED_SUPER;
212 if (base_vaddr != 0)
213 base_flags |= MAP_FIXED | MAP_EXCL;
214
215 mapbase = mmap(base_addr, mapsize, PROT_NONE, base_flags, -1, 0);
216 if (mapbase == MAP_FAILED) {
217 _rtld_error("%s: mmap of entire address space failed: %s",
218 path, rtld_strerror(errno));
219 goto error;
220 }
221 if (base_addr != NULL && mapbase != base_addr) {
222 _rtld_error(
223 "%s: mmap returned wrong address: wanted %p, got %p",
224 path, base_addr, mapbase);
225 goto error1;
226 }
227
228 for (i = 0; i <= nsegs; i++) {
229 /* Overlay the segment onto the proper region. */
230 data_offset = rtld_trunc_page(segs[i]->p_offset);
231 data_vaddr = rtld_trunc_page(segs[i]->p_vaddr);
232 data_vlimit = rtld_round_page(segs[i]->p_vaddr +
233 segs[i]->p_filesz);
234 data_addr = mapbase + (data_vaddr - base_vaddr);
235 data_prot = convert_prot(segs[i]->p_flags);
236 data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED;
237 if (data_vlimit != data_vaddr && mmap(data_addr,
238 data_vlimit - data_vaddr, data_prot, data_flags |
239 MAP_PREFAULT_READ, fd, data_offset) == MAP_FAILED) {
240 _rtld_error("%s: mmap of data failed: %s",
241 path, rtld_strerror(errno));
242 goto error1;
243 }
244
245 /* Do BSS setup */
246 if (segs[i]->p_filesz != segs[i]->p_memsz) {
247 /* Clear any BSS in the last page of the segment. */
248 clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz;
249 clear_addr = mapbase + (clear_vaddr - base_vaddr);
250 clear_page = mapbase + (rtld_trunc_page(clear_vaddr) -
251 base_vaddr);
252
253 if ((nclear = data_vlimit - clear_vaddr) > 0) {
254 /*
255 * Make sure the end of the segment is
256 * writable.
257 */
258 if ((data_prot & PROT_WRITE) == 0 &&
259 mprotect(clear_page, page_size,
260 data_prot | PROT_WRITE) == -1) {
261 _rtld_error("%s: mprotect failed: %s",
262 path, rtld_strerror(errno));
263 goto error1;
264 }
265
266 memset(clear_addr, 0, nclear);
267
268 /* Reset the data protection back */
269 if ((data_prot & PROT_WRITE) == 0)
270 mprotect(clear_page, page_size,
271 data_prot);
272 }
273
274 /* Overlay the BSS segment onto the proper region. */
275 bss_vaddr = data_vlimit;
276 bss_vlimit = rtld_round_page(segs[i]->p_vaddr +
277 segs[i]->p_memsz);
278 bss_addr = mapbase + (bss_vaddr - base_vaddr);
279 if (bss_vlimit > bss_vaddr) {
280 /* There is something to do */
281 if (mmap(bss_addr, bss_vlimit - bss_vaddr,
282 data_prot, data_flags | MAP_ANON, -1,
283 0) == MAP_FAILED) {
284 _rtld_error(
285 "%s: mmap of bss failed: %s",
286 path, rtld_strerror(errno));
287 goto error1;
288 }
289 }
290 }
291
292 if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff &&
293 data_vlimit - data_vaddr + data_offset >=
294 hdr->e_phoff + hdr->e_phnum * sizeof(Elf_Phdr)) {
295 phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset;
296 }
297 }
298
299 obj = obj_new();
300 if (sb != NULL) {
301 obj->dev = sb->st_dev;
302 obj->ino = sb->st_ino;
303 }
304 obj->mapbase = mapbase;
305 obj->mapsize = mapsize;
306 obj->vaddrbase = base_vaddr;
307 obj->relocbase = mapbase - base_vaddr;
308 obj->dynamic = (const Elf_Dyn *)(obj->relocbase + phdyn->p_vaddr);
309 if (hdr->e_entry != 0)
310 obj->entry = (caddr_t)(obj->relocbase + hdr->e_entry);
311 if (phdr_vaddr != 0) {
312 obj->phdr = (const Elf_Phdr *)(obj->relocbase + phdr_vaddr);
313 } else {
314 obj->phdr = malloc(phsize);
315 if (obj->phdr == NULL) {
316 obj_free(obj);
317 _rtld_error("%s: cannot allocate program header",
318 path);
319 goto error1;
320 }
321 memcpy(__DECONST(char *, obj->phdr), (char *)hdr + hdr->e_phoff,
322 phsize);
323 obj->phdr_alloc = true;
324 }
325 obj->phsize = phsize;
326 if (phinterp != NULL)
327 obj->interp = (const char *)(obj->relocbase +
328 phinterp->p_vaddr);
329 if (phtls != NULL) {
330 tls_dtv_generation++;
331 obj->tlsindex = ++tls_max_index;
332 obj->tlssize = phtls->p_memsz;
333 obj->tlsalign = phtls->p_align;
334 obj->tlspoffset = phtls->p_offset;
335 obj->tlsinitsize = phtls->p_filesz;
336 obj->tlsinit = mapbase + phtls->p_vaddr;
337 }
338 obj->stack_flags = stack_flags;
339 if (note_start < note_end)
340 digest_notes(obj, note_start, note_end);
341 if (note_map != NULL)
342 munmap(note_map, note_map_len);
343 munmap(hdr, page_size);
344 return (obj);
345
346 error1:
347 munmap(mapbase, mapsize);
348 error:
349 if (note_map != NULL && note_map != MAP_FAILED)
350 munmap(note_map, note_map_len);
351 if (!phdr_in_zero_page(hdr))
352 munmap(phdr, hdr->e_phnum * sizeof(phdr[0]));
353 munmap(hdr, page_size);
354 return (NULL);
355 }
356
357 bool
check_elf_headers(const Elf_Ehdr * hdr,const char * path)358 check_elf_headers(const Elf_Ehdr *hdr, const char *path)
359 {
360 if (!IS_ELF(*hdr)) {
361 _rtld_error("%s: invalid file format", path);
362 return (false);
363 }
364 if (hdr->e_ident[EI_CLASS] != ELF_TARG_CLASS ||
365 hdr->e_ident[EI_DATA] != ELF_TARG_DATA) {
366 _rtld_error("%s: unsupported file layout", path);
367 return (false);
368 }
369 if (hdr->e_ident[EI_VERSION] != EV_CURRENT ||
370 hdr->e_version != EV_CURRENT) {
371 _rtld_error("%s: unsupported file version", path);
372 return (false);
373 }
374 if (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN) {
375 _rtld_error("%s: unsupported file type", path);
376 return (false);
377 }
378 if (hdr->e_machine != ELF_TARG_MACH) {
379 _rtld_error("%s: unsupported machine", path);
380 return (false);
381 }
382 if (hdr->e_phentsize != sizeof(Elf_Phdr)) {
383 _rtld_error(
384 "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)",
385 path);
386 return (false);
387 }
388 return (true);
389 }
390
391 static Elf_Ehdr *
get_elf_header(int fd,const char * path,const struct stat * sbp,Elf_Phdr ** phdr_p)392 get_elf_header(int fd, const char *path, const struct stat *sbp,
393 Elf_Phdr **phdr_p)
394 {
395 Elf_Ehdr *hdr;
396 Elf_Phdr *phdr;
397
398 /* Make sure file has enough data for the ELF header */
399 if (sbp != NULL && sbp->st_size < (off_t)sizeof(Elf_Ehdr)) {
400 _rtld_error("%s: invalid file format", path);
401 return (NULL);
402 }
403
404 hdr = mmap(NULL, page_size, PROT_READ, MAP_PRIVATE | MAP_PREFAULT_READ,
405 fd, 0);
406 if (hdr == MAP_FAILED) {
407 _rtld_error("%s: read error: %s", path, rtld_strerror(errno));
408 return (NULL);
409 }
410
411 /* Make sure the file is valid */
412 if (!check_elf_headers(hdr, path))
413 goto error;
414
415 /*
416 * We rely on the program header being in the first page. This is
417 * not strictly required by the ABI specification, but it seems to
418 * always true in practice. And, it simplifies things considerably.
419 */
420 if (phdr_in_zero_page(hdr)) {
421 phdr = (Elf_Phdr *)((char *)hdr + hdr->e_phoff);
422 } else {
423 phdr = mmap(NULL, hdr->e_phnum * sizeof(phdr[0]), PROT_READ,
424 MAP_PRIVATE | MAP_PREFAULT_READ, fd, hdr->e_phoff);
425 if (phdr == MAP_FAILED) {
426 _rtld_error("%s: error mapping phdr: %s", path,
427 rtld_strerror(errno));
428 goto error;
429 }
430 }
431 *phdr_p = phdr;
432 return (hdr);
433
434 error:
435 munmap(hdr, page_size);
436 return (NULL);
437 }
438
439 void
obj_free(Obj_Entry * obj)440 obj_free(Obj_Entry *obj)
441 {
442 Objlist_Entry *elm;
443
444 if (obj->tls_static)
445 free_tls_offset(obj);
446 while (obj->needed != NULL) {
447 Needed_Entry *needed = obj->needed;
448
449 obj->needed = needed->next;
450 free(needed);
451 }
452 while (!STAILQ_EMPTY(&obj->names)) {
453 Name_Entry *entry = STAILQ_FIRST(&obj->names);
454
455 STAILQ_REMOVE_HEAD(&obj->names, link);
456 free(entry);
457 }
458 while (!STAILQ_EMPTY(&obj->dldags)) {
459 elm = STAILQ_FIRST(&obj->dldags);
460 STAILQ_REMOVE_HEAD(&obj->dldags, link);
461 free(elm);
462 }
463 while (!STAILQ_EMPTY(&obj->dagmembers)) {
464 elm = STAILQ_FIRST(&obj->dagmembers);
465 STAILQ_REMOVE_HEAD(&obj->dagmembers, link);
466 free(elm);
467 }
468 if (obj->vertab)
469 free(obj->vertab);
470 if (obj->origin_path)
471 free(obj->origin_path);
472 if (obj->z_origin)
473 free(__DECONST(void *, obj->rpath));
474 if (obj->priv)
475 free(obj->priv);
476 if (obj->path)
477 free(obj->path);
478 if (obj->phdr_alloc)
479 free(__DECONST(void *, obj->phdr));
480 free(obj);
481 }
482
483 Obj_Entry *
obj_new(void)484 obj_new(void)
485 {
486 Obj_Entry *obj;
487
488 obj = CNEW(Obj_Entry);
489 STAILQ_INIT(&obj->dldags);
490 STAILQ_INIT(&obj->dagmembers);
491 STAILQ_INIT(&obj->names);
492 return (obj);
493 }
494
495 /*
496 * Given a set of ELF protection flags, return the corresponding protection
497 * flags for MMAP.
498 */
499 int
convert_prot(int elfflags)500 convert_prot(int elfflags)
501 {
502 int prot = 0;
503
504 if ((elfflags & PF_R) != 0)
505 prot |= PROT_READ;
506 if ((elfflags & PF_W) != 0)
507 prot |= PROT_WRITE;
508 if ((elfflags & PF_X) != 0)
509 prot |= PROT_EXEC;
510 return (prot);
511 }
512
513 static int
convert_flags(int elfflags)514 convert_flags(int elfflags)
515 {
516 int flags = MAP_PRIVATE; /* All mappings are private */
517
518 /*
519 * Readonly mappings are marked "MAP_NOCORE", because they can be
520 * reconstructed by a debugger.
521 */
522 if ((elfflags & PF_W) == 0)
523 flags |= MAP_NOCORE;
524 return (flags);
525 }
526