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