1 /* $NetBSD: map_object.c,v 1.41 2010/10/16 10:27:07 skrll 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 1.41 2010/10/16 10:27:07 skrll 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 * 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 size_t phsize; 70 Elf_Phdr *phlimit; 71 Elf_Phdr *segs[2]; 72 int nsegs; 73 caddr_t mapbase = MAP_FAILED; 74 size_t mapsize = 0; 75 int mapflags; 76 Elf_Off base_offset; 77 #ifdef MAP_ALIGNED 78 Elf_Addr base_alignment; 79 #endif 80 Elf_Addr base_vaddr; 81 Elf_Addr base_vlimit; 82 Elf_Addr text_vlimit; 83 int text_flags; 84 caddr_t base_addr; 85 Elf_Off data_offset; 86 Elf_Addr data_vaddr; 87 Elf_Addr data_vlimit; 88 int data_flags; 89 caddr_t data_addr; 90 Elf_Addr phdr_vaddr; 91 size_t phdr_memsz; 92 caddr_t gap_addr; 93 size_t gap_size; 94 int i; 95 #ifdef RTLD_LOADER 96 Elf_Addr clear_vaddr; 97 caddr_t clear_addr; 98 size_t nclear; 99 #endif 100 101 if (sb != NULL && sb->st_size < (off_t)sizeof (Elf_Ehdr)) { 102 _rtld_error("%s: unrecognized file format1", path); 103 return NULL; 104 } 105 106 obj = _rtld_obj_new(); 107 obj->path = xstrdup(path); 108 obj->pathlen = strlen(path); 109 if (sb != NULL) { 110 obj->dev = sb->st_dev; 111 obj->ino = sb->st_ino; 112 } 113 114 ehdr = mmap(NULL, _rtld_pagesz, PROT_READ, MAP_FILE | MAP_SHARED, fd, 115 (off_t)0); 116 obj->ehdr = ehdr; 117 if (ehdr == MAP_FAILED) { 118 _rtld_error("%s: read error: %s", path, xstrerror(errno)); 119 goto bad; 120 } 121 /* Make sure the file is valid */ 122 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0 || 123 ehdr->e_ident[EI_CLASS] != ELFCLASS) { 124 _rtld_error("%s: unrecognized file format2 [%x != %x]", path, 125 ehdr->e_ident[EI_CLASS], ELFCLASS); 126 goto bad; 127 } 128 /* Elf_e_ident includes class */ 129 if (ehdr->e_ident[EI_VERSION] != EV_CURRENT || 130 ehdr->e_version != EV_CURRENT || 131 ehdr->e_ident[EI_DATA] != ELFDEFNNAME(MACHDEP_ENDIANNESS)) { 132 _rtld_error("%s: unsupported file version", path); 133 goto bad; 134 } 135 if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) { 136 _rtld_error("%s: unsupported file type", path); 137 goto bad; 138 } 139 switch (ehdr->e_machine) { 140 ELFDEFNNAME(MACHDEP_ID_CASES) 141 default: 142 _rtld_error("%s: unsupported machine", path); 143 goto bad; 144 } 145 146 /* 147 * We rely on the program header being in the first page. This is 148 * not strictly required by the ABI specification, but it seems to 149 * always true in practice. And, it simplifies things considerably. 150 */ 151 assert(ehdr->e_phentsize == sizeof(Elf_Phdr)); 152 assert(ehdr->e_phoff + ehdr->e_phnum * sizeof(Elf_Phdr) <= 153 _rtld_pagesz); 154 155 /* 156 * Scan the program header entries, and save key information. 157 * 158 * We rely on there being exactly two load segments, text and data, 159 * in that order. 160 */ 161 phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff); 162 phsize = ehdr->e_phnum * sizeof(phdr[0]); 163 obj->phdr = NULL; 164 phdr_vaddr = EA_UNDEF; 165 phdr_memsz = 0; 166 phlimit = phdr + ehdr->e_phnum; 167 nsegs = 0; 168 while (phdr < phlimit) { 169 switch (phdr->p_type) { 170 case PT_INTERP: 171 obj->interp = (void *)(uintptr_t)phdr->p_vaddr; 172 dbg(("%s: PT_INTERP %p", obj->path, obj->interp)); 173 break; 174 175 case PT_LOAD: 176 if (nsegs < 2) 177 segs[nsegs] = phdr; 178 ++nsegs; 179 dbg(("%s: PT_LOAD %p", obj->path, phdr)); 180 break; 181 182 case PT_PHDR: 183 phdr_vaddr = phdr->p_vaddr; 184 phdr_memsz = phdr->p_memsz; 185 dbg(("%s: PT_PHDR %p phsize %zu", obj->path, 186 (void *)(uintptr_t)phdr_vaddr, phdr_memsz)); 187 break; 188 189 case PT_DYNAMIC: 190 obj->dynamic = (void *)(uintptr_t)phdr->p_vaddr; 191 dbg(("%s: PT_DYNAMIC %p", obj->path, obj->dynamic)); 192 break; 193 } 194 195 ++phdr; 196 } 197 phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff); 198 obj->entry = (void *)(uintptr_t)ehdr->e_entry; 199 if (!obj->dynamic) { 200 _rtld_error("%s: not dynamically linked", path); 201 goto bad; 202 } 203 if (nsegs != 2) { 204 _rtld_error("%s: wrong number of segments (%d != 2)", path, 205 nsegs); 206 goto bad; 207 } 208 209 /* 210 * Map the entire address space of the object as a file 211 * region to stake out our contiguous region and establish a 212 * base for relocation. We use a file mapping so that 213 * the kernel will give us whatever alignment is appropriate 214 * for the platform we're running on. 215 * 216 * We map it using the text protection, map the data segment 217 * into the right place, then map an anon segment for the bss 218 * and unmap the gaps left by padding to alignment. 219 */ 220 221 #ifdef MAP_ALIGNED 222 base_alignment = segs[0]->p_align; 223 #endif 224 base_offset = round_down(segs[0]->p_offset); 225 base_vaddr = round_down(segs[0]->p_vaddr); 226 base_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_memsz); 227 text_vlimit = round_up(segs[0]->p_vaddr + segs[0]->p_memsz); 228 text_flags = protflags(segs[0]->p_flags); 229 data_offset = round_down(segs[1]->p_offset); 230 data_vaddr = round_down(segs[1]->p_vaddr); 231 data_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_filesz); 232 data_flags = protflags(segs[1]->p_flags); 233 #ifdef RTLD_LOADER 234 clear_vaddr = segs[1]->p_vaddr + segs[1]->p_filesz; 235 #endif 236 237 obj->textsize = text_vlimit - base_vaddr; 238 obj->vaddrbase = base_vaddr; 239 obj->isdynamic = ehdr->e_type == ET_DYN; 240 241 obj->phdr_loaded = false; 242 for (i = 0; i < nsegs; i++) { 243 if (phdr_vaddr != EA_UNDEF && 244 segs[i]->p_vaddr <= phdr_vaddr && 245 segs[i]->p_memsz >= phdr_memsz) { 246 obj->phdr_loaded = true; 247 break; 248 } 249 if (segs[i]->p_offset <= ehdr->e_phoff && 250 segs[i]->p_memsz >= phsize) { 251 phdr_vaddr = segs[i]->p_vaddr + ehdr->e_phoff; 252 phdr_memsz = phsize; 253 obj->phdr_loaded = true; 254 break; 255 } 256 } 257 if (obj->phdr_loaded) { 258 obj->phdr = (void *)(uintptr_t)phdr_vaddr; 259 obj->phsize = phdr_memsz; 260 } else { 261 Elf_Phdr *buf; 262 buf = xmalloc(phsize); 263 if (buf == NULL) { 264 _rtld_error("%s: cannot allocate program header", path); 265 goto bad; 266 } 267 memcpy(buf, phdr, phsize); 268 obj->phdr = buf; 269 obj->phsize = phsize; 270 } 271 dbg(("%s: phdr %p phsize %zu (%s)", obj->path, obj->phdr, obj->phsize, 272 obj->phdr_loaded ? "loaded" : "allocated")); 273 274 /* Unmap header if it overlaps the first load section. */ 275 if (base_offset < _rtld_pagesz) { 276 munmap(ehdr, _rtld_pagesz); 277 obj->ehdr = MAP_FAILED; 278 } 279 280 /* 281 * Calculate log2 of the base section alignment. 282 */ 283 mapflags = 0; 284 #ifdef MAP_ALIGNED 285 if (base_alignment > _rtld_pagesz) { 286 unsigned int log2 = 0; 287 for (; base_alignment > 1; base_alignment >>= 1) 288 log2++; 289 mapflags = MAP_ALIGNED(log2); 290 } 291 #endif 292 293 #ifdef RTLD_LOADER 294 base_addr = obj->isdynamic ? NULL : (caddr_t)base_vaddr; 295 #else 296 base_addr = NULL; 297 #endif 298 mapsize = base_vlimit - base_vaddr; 299 mapbase = mmap(base_addr, mapsize, text_flags, 300 mapflags | MAP_FILE | MAP_PRIVATE, fd, base_offset); 301 if (mapbase == MAP_FAILED) { 302 _rtld_error("mmap of entire address space failed: %s", 303 xstrerror(errno)); 304 goto bad; 305 } 306 307 /* Overlay the data segment onto the proper region. */ 308 data_addr = mapbase + (data_vaddr - base_vaddr); 309 if (mmap(data_addr, data_vlimit - data_vaddr, data_flags, 310 MAP_FILE | MAP_PRIVATE | MAP_FIXED, fd, data_offset) == 311 MAP_FAILED) { 312 _rtld_error("mmap of data failed: %s", xstrerror(errno)); 313 goto bad; 314 } 315 316 /* Overlay the bss segment onto the proper region. */ 317 if (mmap(mapbase + data_vlimit - base_vaddr, base_vlimit - data_vlimit, 318 data_flags, MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0) == 319 MAP_FAILED) { 320 _rtld_error("mmap of bss failed: %s", xstrerror(errno)); 321 goto bad; 322 } 323 324 /* Unmap the gap between the text and data. */ 325 gap_addr = mapbase + round_up(text_vlimit - base_vaddr); 326 gap_size = data_addr - gap_addr; 327 if (gap_size != 0 && mprotect(gap_addr, gap_size, PROT_NONE) == -1) { 328 _rtld_error("mprotect of text -> data gap failed: %s", 329 xstrerror(errno)); 330 goto bad; 331 } 332 333 #ifdef RTLD_LOADER 334 /* Clear any BSS in the last page of the data segment. */ 335 clear_addr = mapbase + (clear_vaddr - base_vaddr); 336 if ((nclear = data_vlimit - clear_vaddr) > 0) 337 memset(clear_addr, 0, nclear); 338 339 /* Non-file portion of BSS mapped above. */ 340 #endif 341 342 obj->mapbase = mapbase; 343 obj->mapsize = mapsize; 344 obj->relocbase = mapbase - base_vaddr; 345 346 if (obj->dynamic) 347 obj->dynamic = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->dynamic); 348 if (obj->entry) 349 obj->entry = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->entry); 350 if (obj->interp) 351 obj->interp = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->interp); 352 if (obj->phdr_loaded) 353 obj->phdr = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->phdr); 354 355 return obj; 356 357 bad: 358 if (obj->ehdr != MAP_FAILED) 359 munmap(obj->ehdr, _rtld_pagesz); 360 if (mapbase != MAP_FAILED) 361 munmap(mapbase, mapsize); 362 _rtld_obj_free(obj); 363 return NULL; 364 } 365 366 void 367 _rtld_obj_free(Obj_Entry *obj) 368 { 369 Objlist_Entry *elm; 370 371 xfree(obj->path); 372 while (obj->needed != NULL) { 373 Needed_Entry *needed = obj->needed; 374 obj->needed = needed->next; 375 xfree(needed); 376 } 377 while ((elm = SIMPLEQ_FIRST(&obj->dldags)) != NULL) { 378 SIMPLEQ_REMOVE_HEAD(&obj->dldags, link); 379 xfree(elm); 380 } 381 while ((elm = SIMPLEQ_FIRST(&obj->dagmembers)) != NULL) { 382 SIMPLEQ_REMOVE_HEAD(&obj->dagmembers, link); 383 xfree(elm); 384 } 385 if (!obj->phdr_loaded) 386 xfree((void *)(uintptr_t)obj->phdr); 387 xfree(obj); 388 #ifdef COMBRELOC 389 _rtld_combreloc_reset(obj); 390 #endif 391 } 392 393 Obj_Entry * 394 _rtld_obj_new(void) 395 { 396 Obj_Entry *obj; 397 398 obj = CNEW(Obj_Entry); 399 SIMPLEQ_INIT(&obj->dldags); 400 SIMPLEQ_INIT(&obj->dagmembers); 401 return obj; 402 } 403 404 /* 405 * Given a set of ELF protection flags, return the corresponding protection 406 * flags for MMAP. 407 */ 408 static int 409 protflags(int elfflags) 410 { 411 int prot = 0; 412 413 if (elfflags & PF_R) 414 prot |= PROT_READ; 415 #ifdef RTLD_LOADER 416 if (elfflags & PF_W) 417 prot |= PROT_WRITE; 418 #endif 419 if (elfflags & PF_X) 420 prot |= PROT_EXEC; 421 return prot; 422 } 423