1 /* $NetBSD: map_object.c,v 1.39 2010/01/10 07:29:47 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 1.39 2010/01/10 07:29:47 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 "rtld.h" 50 51 static int protflags(int); /* Elf flags -> mmap protection */ 52 53 /* 54 * Map a shared object into memory. The argument is a file descriptor, 55 * which must be open on the object and positioned at its beginning. 56 * 57 * The return value is a pointer to a newly-allocated Obj_Entry structure 58 * for the shared object. Returns NULL on failure. 59 */ 60 Obj_Entry * 61 _rtld_map_object(const char *path, int fd, const struct stat *sb) 62 { 63 Obj_Entry *obj; 64 Elf_Ehdr *ehdr; 65 Elf_Phdr *phdr; 66 Elf_Phdr *phlimit; 67 Elf_Phdr *segs[2]; 68 int nsegs; 69 caddr_t mapbase = MAP_FAILED; 70 size_t mapsize = 0; 71 int mapflags; 72 Elf_Off base_offset; 73 #ifdef MAP_ALIGNED 74 Elf_Addr base_alignment; 75 #endif 76 Elf_Addr base_vaddr; 77 Elf_Addr base_vlimit; 78 Elf_Addr text_vlimit; 79 int text_flags; 80 caddr_t base_addr; 81 Elf_Off data_offset; 82 Elf_Addr data_vaddr; 83 Elf_Addr data_vlimit; 84 int data_flags; 85 caddr_t data_addr; 86 caddr_t gap_addr; 87 size_t gap_size; 88 #ifdef RTLD_LOADER 89 Elf_Addr clear_vaddr; 90 caddr_t clear_addr; 91 size_t nclear; 92 #endif 93 94 if (sb != NULL && sb->st_size < (off_t)sizeof (Elf_Ehdr)) { 95 _rtld_error("%s: unrecognized file format1", path); 96 return NULL; 97 } 98 99 obj = _rtld_obj_new(); 100 obj->path = xstrdup(path); 101 obj->pathlen = strlen(path); 102 if (sb != NULL) { 103 obj->dev = sb->st_dev; 104 obj->ino = sb->st_ino; 105 } 106 107 ehdr = mmap(NULL, _rtld_pagesz, PROT_READ, MAP_FILE | MAP_SHARED, fd, 108 (off_t)0); 109 obj->ehdr = ehdr; 110 if (ehdr == MAP_FAILED) { 111 _rtld_error("%s: read error: %s", path, xstrerror(errno)); 112 goto bad; 113 } 114 /* Make sure the file is valid */ 115 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0 || 116 ehdr->e_ident[EI_CLASS] != ELFCLASS) { 117 _rtld_error("%s: unrecognized file format2 [%x != %x]", path, ehdr->e_ident[EI_CLASS], ELFCLASS); 118 goto bad; 119 } 120 /* Elf_e_ident includes class */ 121 if (ehdr->e_ident[EI_VERSION] != EV_CURRENT || 122 ehdr->e_version != EV_CURRENT || 123 ehdr->e_ident[EI_DATA] != ELFDEFNNAME(MACHDEP_ENDIANNESS)) { 124 _rtld_error("%s: unsupported file version", path); 125 goto bad; 126 } 127 if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) { 128 _rtld_error("%s: unsupported file type", path); 129 goto bad; 130 } 131 switch (ehdr->e_machine) { 132 ELFDEFNNAME(MACHDEP_ID_CASES) 133 default: 134 _rtld_error("%s: unsupported machine", path); 135 goto bad; 136 } 137 138 /* 139 * We rely on the program header being in the first page. This is 140 * not strictly required by the ABI specification, but it seems to 141 * always true in practice. And, it simplifies things considerably. 142 */ 143 assert(ehdr->e_phentsize == sizeof(Elf_Phdr)); 144 assert(ehdr->e_phoff + ehdr->e_phnum * sizeof(Elf_Phdr) <= 145 _rtld_pagesz); 146 147 /* 148 * Scan the program header entries, and save key information. 149 * 150 * We rely on there being exactly two load segments, text and data, 151 * in that order. 152 */ 153 phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff); 154 phlimit = phdr + ehdr->e_phnum; 155 nsegs = 0; 156 while (phdr < phlimit) { 157 switch (phdr->p_type) { 158 case PT_INTERP: 159 obj->interp = (void *)(uintptr_t)phdr->p_vaddr; 160 break; 161 162 case PT_LOAD: 163 if (nsegs < 2) 164 segs[nsegs] = phdr; 165 ++nsegs; 166 break; 167 168 case PT_DYNAMIC: 169 obj->dynamic = (void *)(uintptr_t)phdr->p_vaddr; 170 break; 171 } 172 173 ++phdr; 174 } 175 obj->entry = (void *)(uintptr_t)ehdr->e_entry; 176 if (!obj->dynamic) { 177 _rtld_error("%s: not dynamically linked", path); 178 goto bad; 179 } 180 if (nsegs != 2) { 181 _rtld_error("%s: wrong number of segments (%d != 2)", path, 182 nsegs); 183 goto bad; 184 } 185 186 /* 187 * Map the entire address space of the object as a file 188 * region to stake out our contiguous region and establish a 189 * base for relocation. We use a file mapping so that 190 * the kernel will give us whatever alignment is appropriate 191 * for the platform we're running on. 192 * 193 * We map it using the text protection, map the data segment 194 * into the right place, then map an anon segment for the bss 195 * and unmap the gaps left by padding to alignment. 196 */ 197 198 #ifdef MAP_ALIGNED 199 base_alignment = segs[0]->p_align; 200 #endif 201 base_offset = round_down(segs[0]->p_offset); 202 base_vaddr = round_down(segs[0]->p_vaddr); 203 base_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_memsz); 204 text_vlimit = round_up(segs[0]->p_vaddr + segs[0]->p_memsz); 205 text_flags = protflags(segs[0]->p_flags); 206 data_offset = round_down(segs[1]->p_offset); 207 data_vaddr = round_down(segs[1]->p_vaddr); 208 data_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_filesz); 209 data_flags = protflags(segs[1]->p_flags); 210 #ifdef RTLD_LOADER 211 clear_vaddr = segs[1]->p_vaddr + segs[1]->p_filesz; 212 #endif 213 214 obj->textsize = text_vlimit - base_vaddr; 215 obj->vaddrbase = base_vaddr; 216 obj->isdynamic = ehdr->e_type == ET_DYN; 217 218 /* Unmap header if it overlaps the first load section. */ 219 if (base_offset < _rtld_pagesz) { 220 munmap(ehdr, _rtld_pagesz); 221 obj->ehdr = MAP_FAILED; 222 } 223 224 /* 225 * Calculate log2 of the base section alignment. 226 */ 227 mapflags = 0; 228 #ifdef MAP_ALIGNED 229 if (base_alignment > _rtld_pagesz) { 230 unsigned int log2 = 0; 231 for (; base_alignment > 1; base_alignment >>= 1) 232 log2++; 233 mapflags = MAP_ALIGNED(log2); 234 } 235 #endif 236 237 #ifdef RTLD_LOADER 238 base_addr = obj->isdynamic ? NULL : (caddr_t)base_vaddr; 239 #else 240 base_addr = NULL; 241 #endif 242 mapsize = base_vlimit - base_vaddr; 243 mapbase = mmap(base_addr, mapsize, text_flags, 244 mapflags | MAP_FILE | MAP_PRIVATE, fd, base_offset); 245 if (mapbase == MAP_FAILED) { 246 _rtld_error("mmap of entire address space failed: %s", 247 xstrerror(errno)); 248 goto bad; 249 } 250 251 /* Overlay the data segment onto the proper region. */ 252 data_addr = mapbase + (data_vaddr - base_vaddr); 253 if (mmap(data_addr, data_vlimit - data_vaddr, data_flags, 254 MAP_FILE | MAP_PRIVATE | MAP_FIXED, fd, data_offset) == 255 MAP_FAILED) { 256 _rtld_error("mmap of data failed: %s", xstrerror(errno)); 257 goto bad; 258 } 259 260 /* Overlay the bss segment onto the proper region. */ 261 if (mmap(mapbase + data_vlimit - base_vaddr, base_vlimit - data_vlimit, 262 data_flags, MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0) == 263 MAP_FAILED) { 264 _rtld_error("mmap of bss failed: %s", xstrerror(errno)); 265 goto bad; 266 } 267 268 /* Unmap the gap between the text and data. */ 269 gap_addr = mapbase + round_up(text_vlimit - base_vaddr); 270 gap_size = data_addr - gap_addr; 271 if (gap_size != 0 && mprotect(gap_addr, gap_size, PROT_NONE) == -1) { 272 _rtld_error("mprotect of text -> data gap failed: %s", 273 xstrerror(errno)); 274 goto bad; 275 } 276 277 #ifdef RTLD_LOADER 278 /* Clear any BSS in the last page of the data segment. */ 279 clear_addr = mapbase + (clear_vaddr - base_vaddr); 280 if ((nclear = data_vlimit - clear_vaddr) > 0) 281 memset(clear_addr, 0, nclear); 282 283 /* Non-file portion of BSS mapped above. */ 284 #endif 285 286 obj->mapbase = mapbase; 287 obj->mapsize = mapsize; 288 obj->relocbase = mapbase - base_vaddr; 289 290 if (obj->dynamic) 291 obj->dynamic = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->dynamic); 292 if (obj->entry) 293 obj->entry = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->entry); 294 if (obj->interp) 295 obj->interp = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->interp); 296 297 return obj; 298 299 bad: 300 if (obj->ehdr != MAP_FAILED) 301 munmap(obj->ehdr, _rtld_pagesz); 302 if (mapbase != MAP_FAILED) 303 munmap(mapbase, mapsize); 304 _rtld_obj_free(obj); 305 return NULL; 306 } 307 308 void 309 _rtld_obj_free(Obj_Entry *obj) 310 { 311 Objlist_Entry *elm; 312 313 xfree(obj->path); 314 while (obj->needed != NULL) { 315 Needed_Entry *needed = obj->needed; 316 obj->needed = needed->next; 317 xfree(needed); 318 } 319 while ((elm = SIMPLEQ_FIRST(&obj->dldags)) != NULL) { 320 SIMPLEQ_REMOVE_HEAD(&obj->dldags, link); 321 xfree(elm); 322 } 323 while ((elm = SIMPLEQ_FIRST(&obj->dagmembers)) != NULL) { 324 SIMPLEQ_REMOVE_HEAD(&obj->dagmembers, link); 325 xfree(elm); 326 } 327 xfree(obj); 328 #ifdef COMBRELOC 329 _rtld_combreloc_reset(obj); 330 #endif 331 } 332 333 Obj_Entry * 334 _rtld_obj_new(void) 335 { 336 Obj_Entry *obj; 337 338 obj = CNEW(Obj_Entry); 339 SIMPLEQ_INIT(&obj->dldags); 340 SIMPLEQ_INIT(&obj->dagmembers); 341 return obj; 342 } 343 344 /* 345 * Given a set of ELF protection flags, return the corresponding protection 346 * flags for MMAP. 347 */ 348 static int 349 protflags(int elfflags) 350 { 351 int prot = 0; 352 353 if (elfflags & PF_R) 354 prot |= PROT_READ; 355 #ifdef RTLD_LOADER 356 if (elfflags & PF_W) 357 prot |= PROT_WRITE; 358 #endif 359 if (elfflags & PF_X) 360 prot |= PROT_EXEC; 361 return prot; 362 } 363