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