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