map_object.c revision 1.35
1 /* $NetBSD: map_object.c,v 1.35 2007/10/05 22:21:07 ad 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 1.35 2007/10/05 22:21:07 ad 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 < sizeof (Elf_Ehdr)) { 95 _rtld_error("%s: unrecognized file format", 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 if (ehdr == MAP_FAILED) { 110 _rtld_error("%s: read error: %s", path, xstrerror(errno)); 111 goto bad; 112 } 113 /* Make sure the file is valid */ 114 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0 || 115 ehdr->e_ident[EI_CLASS] != ELFCLASS) { 116 _rtld_error("%s: unrecognized file format", path); 117 goto bad; 118 } 119 /* Elf_e_ident includes class */ 120 if (ehdr->e_ident[EI_VERSION] != EV_CURRENT || 121 ehdr->e_version != EV_CURRENT || 122 ehdr->e_ident[EI_DATA] != ELFDEFNNAME(MACHDEP_ENDIANNESS)) { 123 _rtld_error("%s: unsupported file version", path); 124 goto bad; 125 } 126 if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) { 127 _rtld_error("%s: unsupported file type", path); 128 goto bad; 129 } 130 switch (ehdr->e_machine) { 131 ELFDEFNNAME(MACHDEP_ID_CASES) 132 default: 133 _rtld_error("%s: unsupported machine", path); 134 goto bad; 135 } 136 137 /* 138 * We rely on the program header being in the first page. This is 139 * not strictly required by the ABI specification, but it seems to 140 * always true in practice. And, it simplifies things considerably. 141 */ 142 assert(ehdr->e_phentsize == sizeof(Elf_Phdr)); 143 assert(ehdr->e_phoff + ehdr->e_phnum * sizeof(Elf_Phdr) <= 144 _rtld_pagesz); 145 146 /* 147 * Scan the program header entries, and save key information. 148 * 149 * We rely on there being exactly two load segments, text and data, 150 * in that order. 151 */ 152 phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff); 153 phlimit = phdr + ehdr->e_phnum; 154 nsegs = 0; 155 while (phdr < phlimit) { 156 switch (phdr->p_type) { 157 case PT_INTERP: 158 obj->interp = (void *)phdr->p_vaddr; 159 break; 160 161 case PT_LOAD: 162 if (nsegs < 2) 163 segs[nsegs] = phdr; 164 ++nsegs; 165 break; 166 167 case PT_DYNAMIC: 168 obj->dynamic = (void *)phdr->p_vaddr; 169 break; 170 } 171 172 ++phdr; 173 } 174 obj->entry = (void *)ehdr->e_entry; 175 if (!obj->dynamic) { 176 _rtld_error("%s: not dynamically linked", path); 177 goto bad; 178 } 179 if (nsegs != 2) { 180 _rtld_error("%s: wrong number of segments (%d != 2)", path, 181 nsegs); 182 goto bad; 183 } 184 185 /* 186 * Map the entire address space of the object as a file 187 * region to stake out our contiguous region and establish a 188 * base for relocation. We use a file mapping so that 189 * the kernel will give us whatever alignment is appropriate 190 * for the platform we're running on. 191 * 192 * We map it using the text protection, map the data segment 193 * into the right place, then map an anon segment for the bss 194 * and unmap the gaps left by padding to alignment. 195 */ 196 197 #ifdef MAP_ALIGNED 198 base_alignment = segs[0]->p_align; 199 #endif 200 base_offset = round_down(segs[0]->p_offset); 201 base_vaddr = round_down(segs[0]->p_vaddr); 202 base_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_memsz); 203 text_vlimit = round_up(segs[0]->p_vaddr + segs[0]->p_memsz); 204 text_flags = protflags(segs[0]->p_flags); 205 data_offset = round_down(segs[1]->p_offset); 206 data_vaddr = round_down(segs[1]->p_vaddr); 207 data_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_filesz); 208 data_flags = protflags(segs[1]->p_flags); 209 #ifdef RTLD_LOADER 210 clear_vaddr = segs[1]->p_vaddr + segs[1]->p_filesz; 211 #endif 212 213 obj->textsize = text_vlimit - base_vaddr; 214 obj->vaddrbase = base_vaddr; 215 obj->isdynamic = ehdr->e_type == ET_DYN; 216 217 munmap(ehdr, _rtld_pagesz); 218 ehdr = MAP_FAILED; 219 220 /* 221 * Calculate log2 of the base section alignment. 222 */ 223 mapflags = 0; 224 #ifdef MAP_ALIGNED 225 if (base_alignment > _rtld_pagesz) { 226 unsigned int log2 = 0; 227 for (; base_alignment > 1; base_alignment >>= 1) 228 log2++; 229 mapflags = MAP_ALIGNED(log2); 230 } 231 #endif 232 233 #ifdef RTLD_LOADER 234 base_addr = obj->isdynamic ? NULL : (caddr_t)base_vaddr; 235 #else 236 base_addr = NULL; 237 #endif 238 mapsize = base_vlimit - base_vaddr; 239 mapbase = mmap(base_addr, mapsize, text_flags, 240 mapflags | MAP_FILE | MAP_PRIVATE, fd, base_offset); 241 if (mapbase == MAP_FAILED) { 242 _rtld_error("mmap of entire address space failed: %s", 243 xstrerror(errno)); 244 goto bad; 245 } 246 247 /* Overlay the data segment onto the proper region. */ 248 data_addr = mapbase + (data_vaddr - base_vaddr); 249 if (mmap(data_addr, data_vlimit - data_vaddr, data_flags, 250 MAP_FILE | MAP_PRIVATE | MAP_FIXED, fd, data_offset) == 251 MAP_FAILED) { 252 _rtld_error("mmap of data failed: %s", xstrerror(errno)); 253 goto bad; 254 } 255 256 /* Overlay the bss segment onto the proper region. */ 257 if (mmap(mapbase + data_vlimit - base_vaddr, base_vlimit - data_vlimit, 258 data_flags, MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0) == 259 MAP_FAILED) { 260 _rtld_error("mmap of bss failed: %s", xstrerror(errno)); 261 goto bad; 262 } 263 264 /* Unmap the gap between the text and data. */ 265 gap_addr = mapbase + round_up(text_vlimit - base_vaddr); 266 gap_size = data_addr - gap_addr; 267 if (gap_size != 0 && mprotect(gap_addr, gap_size, PROT_NONE) == -1) { 268 _rtld_error("mprotect of text -> data gap failed: %s", 269 xstrerror(errno)); 270 goto bad; 271 } 272 273 #ifdef RTLD_LOADER 274 /* Clear any BSS in the last page of the data segment. */ 275 clear_addr = mapbase + (clear_vaddr - base_vaddr); 276 if ((nclear = data_vlimit - clear_vaddr) > 0) 277 memset(clear_addr, 0, nclear); 278 279 /* Non-file portion of BSS mapped above. */ 280 #endif 281 282 obj->mapbase = mapbase; 283 obj->mapsize = mapsize; 284 obj->relocbase = mapbase - base_vaddr; 285 286 if (obj->dynamic) 287 obj->dynamic = (void *)(obj->relocbase + (Elf_Addr)obj->dynamic); 288 if (obj->entry) 289 obj->entry = (void *)(obj->relocbase + (Elf_Addr)obj->entry); 290 if (obj->interp) 291 obj->interp = (void *)(obj->relocbase + (Elf_Addr)obj->interp); 292 293 return obj; 294 295 bad: 296 if (ehdr != MAP_FAILED) 297 munmap(ehdr, _rtld_pagesz); 298 if (mapbase != MAP_FAILED) 299 munmap(mapbase, mapsize); 300 _rtld_obj_free(obj); 301 return NULL; 302 } 303 304 void 305 _rtld_obj_free(Obj_Entry *obj) 306 { 307 Objlist_Entry *elm; 308 309 xfree(obj->path); 310 while (obj->needed != NULL) { 311 Needed_Entry *needed = obj->needed; 312 obj->needed = needed->next; 313 xfree(needed); 314 } 315 while ((elm = SIMPLEQ_FIRST(&obj->dldags)) != NULL) { 316 SIMPLEQ_REMOVE_HEAD(&obj->dldags, link); 317 xfree(elm); 318 } 319 while ((elm = SIMPLEQ_FIRST(&obj->dagmembers)) != NULL) { 320 SIMPLEQ_REMOVE_HEAD(&obj->dagmembers, link); 321 xfree(elm); 322 } 323 xfree(obj); 324 } 325 326 Obj_Entry * 327 _rtld_obj_new(void) 328 { 329 Obj_Entry *obj; 330 331 obj = CNEW(Obj_Entry); 332 SIMPLEQ_INIT(&obj->dldags); 333 SIMPLEQ_INIT(&obj->dagmembers); 334 return obj; 335 } 336 337 /* 338 * Given a set of ELF protection flags, return the corresponding protection 339 * flags for MMAP. 340 */ 341 static int 342 protflags(int elfflags) 343 { 344 int prot = 0; 345 346 if (elfflags & PF_R) 347 prot |= PROT_READ; 348 #ifdef RTLD_LOADER 349 if (elfflags & PF_W) 350 prot |= PROT_WRITE; 351 #endif 352 if (elfflags & PF_X) 353 prot |= PROT_EXEC; 354 return prot; 355 } 356
Indexes created Thu Sep 25 16:09:42 GMT 2025