map_object.c revision 1.40
1 /* $NetBSD: map_object.c,v 1.40 2010/09/11 11:11:52 skrll Exp $ */ 2 3 /* 4 * Copyright 1996 John D. Polstra. 5 * Copyright 1996 Matt Thomas <matt (at) 3am-software.com> 6 * Copyright 2002 Charles M. Hannum <root (at) 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 1.40 2010/09/11 11:11:52 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, 118 ehdr->e_ident[EI_CLASS], ELFCLASS); 119 goto bad; 120 } 121 /* Elf_e_ident includes class */ 122 if (ehdr->e_ident[EI_VERSION] != EV_CURRENT || 123 ehdr->e_version != EV_CURRENT || 124 ehdr->e_ident[EI_DATA] != ELFDEFNNAME(MACHDEP_ENDIANNESS)) { 125 _rtld_error("%s: unsupported file version", path); 126 goto bad; 127 } 128 if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) { 129 _rtld_error("%s: unsupported file type", path); 130 goto bad; 131 } 132 switch (ehdr->e_machine) { 133 ELFDEFNNAME(MACHDEP_ID_CASES) 134 default: 135 _rtld_error("%s: unsupported machine", path); 136 goto bad; 137 } 138 139 /* 140 * We rely on the program header being in the first page. This is 141 * not strictly required by the ABI specification, but it seems to 142 * always true in practice. And, it simplifies things considerably. 143 */ 144 assert(ehdr->e_phentsize == sizeof(Elf_Phdr)); 145 assert(ehdr->e_phoff + ehdr->e_phnum * sizeof(Elf_Phdr) <= 146 _rtld_pagesz); 147 148 /* 149 * Scan the program header entries, and save key information. 150 * 151 * We rely on there being exactly two load segments, text and data, 152 * in that order. 153 */ 154 phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff); 155 phlimit = phdr + ehdr->e_phnum; 156 nsegs = 0; 157 while (phdr < phlimit) { 158 switch (phdr->p_type) { 159 case PT_INTERP: 160 obj->interp = (void *)(uintptr_t)phdr->p_vaddr; 161 break; 162 163 case PT_LOAD: 164 if (nsegs < 2) 165 segs[nsegs] = phdr; 166 ++nsegs; 167 break; 168 169 case PT_DYNAMIC: 170 obj->dynamic = (void *)(uintptr_t)phdr->p_vaddr; 171 break; 172 } 173 174 ++phdr; 175 } 176 obj->entry = (void *)(uintptr_t)ehdr->e_entry; 177 if (!obj->dynamic) { 178 _rtld_error("%s: not dynamically linked", path); 179 goto bad; 180 } 181 if (nsegs != 2) { 182 _rtld_error("%s: wrong number of segments (%d != 2)", path, 183 nsegs); 184 goto bad; 185 } 186 187 /* 188 * Map the entire address space of the object as a file 189 * region to stake out our contiguous region and establish a 190 * base for relocation. We use a file mapping so that 191 * the kernel will give us whatever alignment is appropriate 192 * for the platform we're running on. 193 * 194 * We map it using the text protection, map the data segment 195 * into the right place, then map an anon segment for the bss 196 * and unmap the gaps left by padding to alignment. 197 */ 198 199 #ifdef MAP_ALIGNED 200 base_alignment = segs[0]->p_align; 201 #endif 202 base_offset = round_down(segs[0]->p_offset); 203 base_vaddr = round_down(segs[0]->p_vaddr); 204 base_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_memsz); 205 text_vlimit = round_up(segs[0]->p_vaddr + segs[0]->p_memsz); 206 text_flags = protflags(segs[0]->p_flags); 207 data_offset = round_down(segs[1]->p_offset); 208 data_vaddr = round_down(segs[1]->p_vaddr); 209 data_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_filesz); 210 data_flags = protflags(segs[1]->p_flags); 211 #ifdef RTLD_LOADER 212 clear_vaddr = segs[1]->p_vaddr + segs[1]->p_filesz; 213 #endif 214 215 obj->textsize = text_vlimit - base_vaddr; 216 obj->vaddrbase = base_vaddr; 217 obj->isdynamic = ehdr->e_type == ET_DYN; 218 219 /* Unmap header if it overlaps the first load section. */ 220 if (base_offset < _rtld_pagesz) { 221 munmap(ehdr, _rtld_pagesz); 222 obj->ehdr = MAP_FAILED; 223 } 224 225 /* 226 * Calculate log2 of the base section alignment. 227 */ 228 mapflags = 0; 229 #ifdef MAP_ALIGNED 230 if (base_alignment > _rtld_pagesz) { 231 unsigned int log2 = 0; 232 for (; base_alignment > 1; base_alignment >>= 1) 233 log2++; 234 mapflags = MAP_ALIGNED(log2); 235 } 236 #endif 237 238 #ifdef RTLD_LOADER 239 base_addr = obj->isdynamic ? NULL : (caddr_t)base_vaddr; 240 #else 241 base_addr = NULL; 242 #endif 243 mapsize = base_vlimit - base_vaddr; 244 mapbase = mmap(base_addr, mapsize, text_flags, 245 mapflags | MAP_FILE | MAP_PRIVATE, fd, base_offset); 246 if (mapbase == MAP_FAILED) { 247 _rtld_error("mmap of entire address space failed: %s", 248 xstrerror(errno)); 249 goto bad; 250 } 251 252 /* Overlay the data segment onto the proper region. */ 253 data_addr = mapbase + (data_vaddr - base_vaddr); 254 if (mmap(data_addr, data_vlimit - data_vaddr, data_flags, 255 MAP_FILE | MAP_PRIVATE | MAP_FIXED, fd, data_offset) == 256 MAP_FAILED) { 257 _rtld_error("mmap of data failed: %s", xstrerror(errno)); 258 goto bad; 259 } 260 261 /* Overlay the bss segment onto the proper region. */ 262 if (mmap(mapbase + data_vlimit - base_vaddr, base_vlimit - data_vlimit, 263 data_flags, MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0) == 264 MAP_FAILED) { 265 _rtld_error("mmap of bss failed: %s", xstrerror(errno)); 266 goto bad; 267 } 268 269 /* Unmap the gap between the text and data. */ 270 gap_addr = mapbase + round_up(text_vlimit - base_vaddr); 271 gap_size = data_addr - gap_addr; 272 if (gap_size != 0 && mprotect(gap_addr, gap_size, PROT_NONE) == -1) { 273 _rtld_error("mprotect of text -> data gap failed: %s", 274 xstrerror(errno)); 275 goto bad; 276 } 277 278 #ifdef RTLD_LOADER 279 /* Clear any BSS in the last page of the data segment. */ 280 clear_addr = mapbase + (clear_vaddr - base_vaddr); 281 if ((nclear = data_vlimit - clear_vaddr) > 0) 282 memset(clear_addr, 0, nclear); 283 284 /* Non-file portion of BSS mapped above. */ 285 #endif 286 287 obj->mapbase = mapbase; 288 obj->mapsize = mapsize; 289 obj->relocbase = mapbase - base_vaddr; 290 291 if (obj->dynamic) 292 obj->dynamic = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->dynamic); 293 if (obj->entry) 294 obj->entry = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->entry); 295 if (obj->interp) 296 obj->interp = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->interp); 297 298 return obj; 299 300 bad: 301 if (obj->ehdr != MAP_FAILED) 302 munmap(obj->ehdr, _rtld_pagesz); 303 if (mapbase != MAP_FAILED) 304 munmap(mapbase, mapsize); 305 _rtld_obj_free(obj); 306 return NULL; 307 } 308 309 void 310 _rtld_obj_free(Obj_Entry *obj) 311 { 312 Objlist_Entry *elm; 313 314 xfree(obj->path); 315 while (obj->needed != NULL) { 316 Needed_Entry *needed = obj->needed; 317 obj->needed = needed->next; 318 xfree(needed); 319 } 320 while ((elm = SIMPLEQ_FIRST(&obj->dldags)) != NULL) { 321 SIMPLEQ_REMOVE_HEAD(&obj->dldags, link); 322 xfree(elm); 323 } 324 while ((elm = SIMPLEQ_FIRST(&obj->dagmembers)) != NULL) { 325 SIMPLEQ_REMOVE_HEAD(&obj->dagmembers, link); 326 xfree(elm); 327 } 328 xfree(obj); 329 #ifdef COMBRELOC 330 _rtld_combreloc_reset(obj); 331 #endif 332 } 333 334 Obj_Entry * 335 _rtld_obj_new(void) 336 { 337 Obj_Entry *obj; 338 339 obj = CNEW(Obj_Entry); 340 SIMPLEQ_INIT(&obj->dldags); 341 SIMPLEQ_INIT(&obj->dagmembers); 342 return obj; 343 } 344 345 /* 346 * Given a set of ELF protection flags, return the corresponding protection 347 * flags for MMAP. 348 */ 349 static int 350 protflags(int elfflags) 351 { 352 int prot = 0; 353 354 if (elfflags & PF_R) 355 prot |= PROT_READ; 356 #ifdef RTLD_LOADER 357 if (elfflags & PF_W) 358 prot |= PROT_WRITE; 359 #endif 360 if (elfflags & PF_X) 361 prot |= PROT_EXEC; 362 return prot; 363 } 364
Indexes created Fri Sep 26 20:09:58 GMT 2025