1 /* $NetBSD: map_object.c,v 1.53 2014/10/30 07:53:41 martin Exp $ */
2
3 /*
4 * Copyright 1996 John D. Polstra.
5 * Copyright 1996 Matt Thomas <matt@3am-software.com>
6 * Copyright 2002 Charles M. Hannum <root@ihack.net>
7 * All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 3. All advertising materials mentioning features or use of this software
18 * must display the following acknowledgement:
19 * This product includes software developed by John Polstra.
20 * 4. The name of the author may not be used to endorse or promote products
21 * derived from this software without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
24 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
25 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
26 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
27 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
28 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
29 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
30 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
31 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
32 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
33 */
34
35 #include <sys/cdefs.h>
36 #ifndef lint
37 __RCSID("$NetBSD: map_object.c,v 1.53 2014/10/30 07:53:41 martin Exp $");
38 #endif /* not lint */
39
40 #include <errno.h>
41 #include <stddef.h>
42 #include <stdlib.h>
43 #include <string.h>
44 #include <unistd.h>
45 #include <sys/stat.h>
46 #include <sys/types.h>
47 #include <sys/mman.h>
48
49 #include "debug.h"
50 #include "rtld.h"
51
52 static int protflags(int); /* Elf flags -> mmap protection */
53
54 #define EA_UNDEF (~(Elf_Addr)0)
55
56 /*
57 * Map a shared object into memory. The argument is a file descriptor,
58 * which must be open on the object and positioned at its beginning.
59 *
60 * The return value is a pointer to a newly-allocated Obj_Entry structure
61 * for the shared object. Returns NULL on failure.
62 */
63 Obj_Entry *
_rtld_map_object(const char * path,int fd,const struct stat * sb)64 _rtld_map_object(const char *path, int fd, const struct stat *sb)
65 {
66 Obj_Entry *obj;
67 Elf_Ehdr *ehdr;
68 Elf_Phdr *phdr;
69 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
70 Elf_Phdr *phtls;
71 #endif
72 size_t phsize;
73 Elf_Phdr *phlimit;
74 Elf_Phdr *segs[2];
75 int nsegs;
76 caddr_t mapbase = MAP_FAILED;
77 size_t mapsize = 0;
78 int mapflags;
79 Elf_Off base_offset;
80 #ifdef MAP_ALIGNED
81 Elf_Addr base_alignment;
82 #endif
83 Elf_Addr base_vaddr;
84 Elf_Addr base_vlimit;
85 Elf_Addr text_vlimit;
86 int text_flags;
87 caddr_t base_addr;
88 Elf_Off data_offset;
89 Elf_Addr data_vaddr;
90 Elf_Addr data_vlimit;
91 int data_flags;
92 caddr_t data_addr;
93 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
94 Elf_Addr tls_vaddr = 0; /* Noise GCC */
95 #endif
96 Elf_Addr phdr_vaddr;
97 size_t phdr_memsz;
98 #if defined(__minix) && (defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II))
99 caddr_t gap_addr;
100 size_t gap_size;
101 #endif /* defined(__minix) */
102 int i;
103 #ifdef RTLD_LOADER
104 Elf_Addr clear_vaddr;
105 caddr_t clear_addr;
106 size_t nclear;
107 #endif
108
109 if (sb != NULL && sb->st_size < (off_t)sizeof (Elf_Ehdr)) {
110 _rtld_error("%s: not ELF file (too short)", path);
111 return NULL;
112 }
113
114 obj = _rtld_obj_new();
115 obj->path = xstrdup(path);
116 obj->pathlen = strlen(path);
117 if (sb != NULL) {
118 obj->dev = sb->st_dev;
119 obj->ino = sb->st_ino;
120 }
121
122 ehdr = mmap(NULL, _rtld_pagesz, PROT_READ, MAP_FILE | MAP_SHARED, fd,
123 (off_t)0);
124 obj->ehdr = ehdr;
125 if (ehdr == MAP_FAILED) {
126 _rtld_error("%s: read error: %s", path, xstrerror(errno));
127 goto bad;
128 }
129 /* Make sure the file is valid */
130 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0) {
131 _rtld_error("%s: not ELF file (magic number bad)", path);
132 goto bad;
133 }
134 if (ehdr->e_ident[EI_CLASS] != ELFCLASS) {
135 _rtld_error("%s: invalid ELF class %x; expected %x", path,
136 ehdr->e_ident[EI_CLASS], ELFCLASS);
137 goto bad;
138 }
139 /* Elf_e_ident includes class */
140 if (ehdr->e_ident[EI_VERSION] != EV_CURRENT ||
141 ehdr->e_version != EV_CURRENT ||
142 ehdr->e_ident[EI_DATA] != ELFDEFNNAME(MACHDEP_ENDIANNESS)) {
143 _rtld_error("%s: unsupported file version", path);
144 goto bad;
145 }
146 if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) {
147 _rtld_error("%s: unsupported file type", path);
148 goto bad;
149 }
150 switch (ehdr->e_machine) {
151 ELFDEFNNAME(MACHDEP_ID_CASES)
152 default:
153 _rtld_error("%s: unsupported machine", path);
154 goto bad;
155 }
156
157 /*
158 * We rely on the program header being in the first page. This is
159 * not strictly required by the ABI specification, but it seems to
160 * always true in practice. And, it simplifies things considerably.
161 */
162 assert(ehdr->e_phentsize == sizeof(Elf_Phdr));
163 assert(ehdr->e_phoff + ehdr->e_phnum * sizeof(Elf_Phdr) <=
164 _rtld_pagesz);
165
166 /*
167 * Scan the program header entries, and save key information.
168 *
169 * We rely on there being exactly two load segments, text and data,
170 * in that order.
171 */
172 phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff);
173 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
174 phtls = NULL;
175 #endif
176 phsize = ehdr->e_phnum * sizeof(phdr[0]);
177 obj->phdr = NULL;
178 phdr_vaddr = EA_UNDEF;
179 phdr_memsz = 0;
180 phlimit = phdr + ehdr->e_phnum;
181 nsegs = 0;
182 while (phdr < phlimit) {
183 switch (phdr->p_type) {
184 case PT_INTERP:
185 obj->interp = (void *)(uintptr_t)phdr->p_vaddr;
186 dbg(("%s: PT_INTERP %p", obj->path, obj->interp));
187 break;
188
189 case PT_LOAD:
190 if (nsegs < 2)
191 segs[nsegs] = phdr;
192 ++nsegs;
193
194 dbg(("%s: %s %p phsize %" PRImemsz, obj->path, "PT_LOAD",
195 (void *)(uintptr_t)phdr->p_vaddr, phdr->p_memsz));
196 break;
197
198 case PT_PHDR:
199 phdr_vaddr = phdr->p_vaddr;
200 phdr_memsz = phdr->p_memsz;
201 dbg(("%s: %s %p phsize %" PRImemsz, obj->path, "PT_PHDR",
202 (void *)(uintptr_t)phdr->p_vaddr, phdr->p_memsz));
203 break;
204
205 case PT_DYNAMIC:
206 obj->dynamic = (void *)(uintptr_t)phdr->p_vaddr;
207 dbg(("%s: %s %p phsize %" PRImemsz, obj->path, "PT_DYNAMIC",
208 (void *)(uintptr_t)phdr->p_vaddr, phdr->p_memsz));
209 break;
210
211 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
212 case PT_TLS:
213 phtls = phdr;
214 dbg(("%s: %s %p phsize %" PRImemsz, obj->path, "PT_TLS",
215 (void *)(uintptr_t)phdr->p_vaddr, phdr->p_memsz));
216 break;
217 #endif
218 #ifdef __ARM_EABI__
219 case PT_ARM_EXIDX:
220 obj->exidx_start = (void *)(uintptr_t)phdr->p_vaddr;
221 obj->exidx_sz = phdr->p_memsz;
222 break;
223 #endif
224 }
225
226 ++phdr;
227 }
228 phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff);
229 obj->entry = (void *)(uintptr_t)ehdr->e_entry;
230 if (!obj->dynamic) {
231 _rtld_error("%s: not dynamically linked", path);
232 goto bad;
233 }
234 if (nsegs != 2) {
235 _rtld_error("%s: wrong number of segments (%d != 2)", path,
236 nsegs);
237 goto bad;
238 }
239
240 /*
241 * Map the entire address space of the object as a file
242 * region to stake out our contiguous region and establish a
243 * base for relocation. We use a file mapping so that
244 * the kernel will give us whatever alignment is appropriate
245 * for the platform we're running on.
246 *
247 * We map it using the text protection, map the data segment
248 * into the right place, then map an anon segment for the bss
249 * and unmap the gaps left by padding to alignment.
250 */
251
252 #ifdef MAP_ALIGNED
253 base_alignment = segs[0]->p_align;
254 #endif
255 base_offset = round_down(segs[0]->p_offset);
256 base_vaddr = round_down(segs[0]->p_vaddr);
257 base_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_memsz);
258 text_vlimit = round_up(segs[0]->p_vaddr + segs[0]->p_memsz);
259 text_flags = protflags(segs[0]->p_flags);
260 data_offset = round_down(segs[1]->p_offset);
261 data_vaddr = round_down(segs[1]->p_vaddr);
262 data_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_filesz);
263 data_flags = protflags(segs[1]->p_flags);
264 #ifdef RTLD_LOADER
265 clear_vaddr = segs[1]->p_vaddr + segs[1]->p_filesz;
266 #endif
267
268 obj->textsize = text_vlimit - base_vaddr;
269 obj->vaddrbase = base_vaddr;
270 obj->isdynamic = ehdr->e_type == ET_DYN;
271
272 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
273 if (phtls != NULL) {
274 ++_rtld_tls_dtv_generation;
275 obj->tlsindex = ++_rtld_tls_max_index;
276 obj->tlssize = phtls->p_memsz;
277 obj->tlsalign = phtls->p_align;
278 obj->tlsinitsize = phtls->p_filesz;
279 tls_vaddr = phtls->p_vaddr;
280 }
281 #endif
282
283 obj->phdr_loaded = false;
284 for (i = 0; i < nsegs; i++) {
285 if (phdr_vaddr != EA_UNDEF &&
286 segs[i]->p_vaddr <= phdr_vaddr &&
287 segs[i]->p_memsz >= phdr_memsz) {
288 obj->phdr_loaded = true;
289 break;
290 }
291 if (segs[i]->p_offset <= ehdr->e_phoff &&
292 segs[i]->p_memsz >= phsize) {
293 phdr_vaddr = segs[i]->p_vaddr + ehdr->e_phoff;
294 phdr_memsz = phsize;
295 obj->phdr_loaded = true;
296 break;
297 }
298 }
299 if (obj->phdr_loaded) {
300 obj->phdr = (void *)(uintptr_t)phdr_vaddr;
301 obj->phsize = phdr_memsz;
302 } else {
303 Elf_Phdr *buf;
304 buf = xmalloc(phsize);
305 if (buf == NULL) {
306 _rtld_error("%s: cannot allocate program header", path);
307 goto bad;
308 }
309 memcpy(buf, phdr, phsize);
310 obj->phdr = buf;
311 obj->phsize = phsize;
312 }
313 dbg(("%s: phdr %p phsize %zu (%s)", obj->path, obj->phdr, obj->phsize,
314 obj->phdr_loaded ? "loaded" : "allocated"));
315
316 /* Unmap header if it overlaps the first load section. */
317 if (base_offset < _rtld_pagesz) {
318 munmap(ehdr, _rtld_pagesz);
319 obj->ehdr = MAP_FAILED;
320 }
321
322 /*
323 * Calculate log2 of the base section alignment.
324 */
325 mapflags = 0;
326 #ifdef MAP_ALIGNED
327 if (base_alignment > _rtld_pagesz) {
328 unsigned int log2 = 0;
329 for (; base_alignment > 1; base_alignment >>= 1)
330 log2++;
331 mapflags = MAP_ALIGNED(log2);
332 }
333 #endif
334
335 #ifdef RTLD_LOADER
336 base_addr = obj->isdynamic ? NULL : (caddr_t)base_vaddr;
337 #else
338 base_addr = NULL;
339 #endif
340 mapsize = base_vlimit - base_vaddr;
341 mapbase = mmap(base_addr, mapsize, text_flags,
342 mapflags | MAP_FILE | MAP_PRIVATE, fd, base_offset);
343 if (mapbase == MAP_FAILED) {
344 _rtld_error("mmap of entire address space failed: %s",
345 xstrerror(errno));
346 goto bad;
347 }
348
349 /* Overlay the data segment onto the proper region. */
350 data_addr = mapbase + (data_vaddr - base_vaddr);
351 if (mmap(data_addr, data_vlimit - data_vaddr, data_flags,
352 MAP_FILE | MAP_PRIVATE | MAP_FIXED, fd, data_offset) ==
353 MAP_FAILED) {
354 _rtld_error("mmap of data failed: %s", xstrerror(errno));
355 goto bad;
356 }
357
358 /* Overlay the bss segment onto the proper region. */
359 #if defined(__minix)
360 /* MINIX's mmap is strict and refuses 0-bytes mappings. */
361 if (0 < base_vlimit - data_vlimit)
362 #endif /*defined(__minix) */
363 if (mmap(mapbase + data_vlimit - base_vaddr, base_vlimit - data_vlimit,
364 data_flags, MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0) ==
365 MAP_FAILED) {
366 _rtld_error("mmap of bss failed: %s", xstrerror(errno));
367 goto bad;
368 }
369
370 /* Unmap the gap between the text and data. */
371 #if !defined(__minix)
372 gap_addr = mapbase + round_up(text_vlimit - base_vaddr);
373 gap_size = data_addr - gap_addr;
374 if (gap_size != 0 && mprotect(gap_addr, gap_size, PROT_NONE) == -1) {
375 _rtld_error("mprotect of text -> data gap failed: %s",
376 xstrerror(errno));
377 goto bad;
378 }
379 #endif /* !defined(__minix) */
380
381 #ifdef RTLD_LOADER
382 /* Clear any BSS in the last page of the data segment. */
383 clear_addr = mapbase + (clear_vaddr - base_vaddr);
384 if ((nclear = data_vlimit - clear_vaddr) > 0)
385 memset(clear_addr, 0, nclear);
386
387 /* Non-file portion of BSS mapped above. */
388 #endif
389
390 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
391 if (phtls != NULL)
392 obj->tlsinit = mapbase + tls_vaddr;
393 #endif
394
395 obj->mapbase = mapbase;
396 obj->mapsize = mapsize;
397 obj->relocbase = mapbase - base_vaddr;
398
399 if (obj->dynamic)
400 obj->dynamic = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->dynamic);
401 if (obj->entry)
402 obj->entry = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->entry);
403 if (obj->interp)
404 obj->interp = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->interp);
405 if (obj->phdr_loaded)
406 obj->phdr = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->phdr);
407 #ifdef __ARM_EABI__
408 if (obj->exidx_start)
409 obj->exidx_start = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->exidx_start);
410 #endif
411
412 return obj;
413
414 bad:
415 if (obj->ehdr != MAP_FAILED)
416 munmap(obj->ehdr, _rtld_pagesz);
417 if (mapbase != MAP_FAILED)
418 munmap(mapbase, mapsize);
419 _rtld_obj_free(obj);
420 return NULL;
421 }
422
423 void
_rtld_obj_free(Obj_Entry * obj)424 _rtld_obj_free(Obj_Entry *obj)
425 {
426 Objlist_Entry *elm;
427 Name_Entry *entry;
428
429 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
430 if (obj->tls_done)
431 _rtld_tls_offset_free(obj);
432 #endif
433 xfree(obj->path);
434 while (obj->needed != NULL) {
435 Needed_Entry *needed = obj->needed;
436 obj->needed = needed->next;
437 xfree(needed);
438 }
439 while ((entry = SIMPLEQ_FIRST(&obj->names)) != NULL) {
440 SIMPLEQ_REMOVE_HEAD(&obj->names, link);
441 xfree(entry);
442 }
443 while ((elm = SIMPLEQ_FIRST(&obj->dldags)) != NULL) {
444 SIMPLEQ_REMOVE_HEAD(&obj->dldags, link);
445 xfree(elm);
446 }
447 while ((elm = SIMPLEQ_FIRST(&obj->dagmembers)) != NULL) {
448 SIMPLEQ_REMOVE_HEAD(&obj->dagmembers, link);
449 xfree(elm);
450 }
451 if (!obj->phdr_loaded)
452 xfree((void *)(uintptr_t)obj->phdr);
453 #ifdef COMBRELOC
454 _rtld_combreloc_reset(obj);
455 #endif
456 xfree(obj);
457 }
458
459 Obj_Entry *
_rtld_obj_new(void)460 _rtld_obj_new(void)
461 {
462 Obj_Entry *obj;
463
464 obj = CNEW(Obj_Entry);
465 SIMPLEQ_INIT(&obj->names);
466 SIMPLEQ_INIT(&obj->dldags);
467 SIMPLEQ_INIT(&obj->dagmembers);
468 return obj;
469 }
470
471 /*
472 * Given a set of ELF protection flags, return the corresponding protection
473 * flags for MMAP.
474 */
475 static int
protflags(int elfflags)476 protflags(int elfflags)
477 {
478 int prot = 0;
479
480 if (elfflags & PF_R)
481 prot |= PROT_READ;
482 #ifdef RTLD_LOADER
483 if (elfflags & PF_W)
484 prot |= PROT_WRITE;
485 #endif
486 if (elfflags & PF_X)
487 prot |= PROT_EXEC;
488 #if defined(__minix)
489 /* Minix has to map it writable so we can do relocations
490 * as we don't have mprotect() yet.
491 */
492 prot |= PROT_WRITE;
493 #endif /* defined(__minix) */
494 return prot;
495 }
496