map_object.c revision 1.27
1 /* $NetBSD: map_object.c,v 1.27 2003/03/06 07:34:56 matt 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 <errno.h> 36 #include <stddef.h> 37 #include <stdlib.h> 38 #include <string.h> 39 #include <unistd.h> 40 #include <sys/stat.h> 41 #include <sys/types.h> 42 #include <sys/mman.h> 43 44 #include "rtld.h" 45 46 static int protflags __P((int)); /* Elf flags -> mmap protection */ 47 48 /* 49 * Map a shared object into memory. The argument is a file descriptor, 50 * which must be open on the object and positioned at its beginning. 51 * 52 * The return value is a pointer to a newly-allocated Obj_Entry structure 53 * for the shared object. Returns NULL on failure. 54 */ 55 Obj_Entry * 56 _rtld_map_object(path, fd, sb) 57 char *path; 58 int fd; 59 const struct stat *sb; 60 { 61 Obj_Entry *obj; 62 Elf_Ehdr *ehdr; 63 Elf_Phdr *phdr; 64 Elf_Phdr *phlimit; 65 Elf_Phdr *segs[2]; 66 int nsegs; 67 caddr_t mapbase = MAP_FAILED; 68 size_t mapsize; 69 int mapflags; 70 Elf_Off base_offset; 71 Elf_Addr base_alignment; 72 Elf_Addr base_vaddr; 73 Elf_Addr base_vlimit; 74 Elf_Addr text_vlimit; 75 int text_flags; 76 caddr_t base_addr; 77 Elf_Off data_offset; 78 Elf_Addr data_vaddr; 79 Elf_Addr data_vlimit; 80 int data_flags; 81 caddr_t data_addr; 82 caddr_t gap_addr; 83 size_t gap_size; 84 #ifdef RTLD_LOADER 85 Elf_Addr clear_vaddr; 86 caddr_t clear_addr; 87 size_t nclear; 88 #endif 89 90 if (sb != NULL && sb->st_size < sizeof (Elf_Ehdr)) { 91 _rtld_error("%s: unrecognized file format", path); 92 return NULL; 93 } 94 95 obj = _rtld_obj_new(); 96 obj->path = path; 97 obj->pathlen = strlen(path); 98 if (sb != NULL) { 99 obj->dev = sb->st_dev; 100 obj->ino = sb->st_ino; 101 } 102 103 ehdr = mmap(NULL, _rtld_pagesz, PROT_READ, MAP_FILE | MAP_SHARED, fd, 104 (off_t)0); 105 if (ehdr == MAP_FAILED) { 106 _rtld_error("%s: read error: %s", path, xstrerror(errno)); 107 goto bad; 108 } 109 /* Make sure the file is valid */ 110 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0 || 111 ehdr->e_ident[EI_CLASS] != ELFCLASS) { 112 _rtld_error("%s: unrecognized file format", path); 113 goto bad; 114 } 115 /* Elf_e_ident includes class */ 116 if (ehdr->e_ident[EI_VERSION] != EV_CURRENT || 117 ehdr->e_version != EV_CURRENT || 118 ehdr->e_ident[EI_DATA] != ELFDEFNNAME(MACHDEP_ENDIANNESS)) { 119 _rtld_error("%s: unsupported file version", path); 120 goto bad; 121 } 122 if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) { 123 _rtld_error("%s: unsupported file type", path); 124 goto bad; 125 } 126 switch (ehdr->e_machine) { 127 ELFDEFNNAME(MACHDEP_ID_CASES) 128 default: 129 _rtld_error("%s: unsupported machine", path); 130 goto bad; 131 } 132 133 /* 134 * We rely on the program header being in the first page. This is 135 * not strictly required by the ABI specification, but it seems to 136 * always true in practice. And, it simplifies things considerably. 137 */ 138 assert(ehdr->e_phentsize == sizeof(Elf_Phdr)); 139 assert(ehdr->e_phoff + ehdr->e_phnum * sizeof(Elf_Phdr) <= 140 _rtld_pagesz); 141 142 /* 143 * Scan the program header entries, and save key information. 144 * 145 * We rely on there being exactly two load segments, text and data, 146 * in that order. 147 */ 148 phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff); 149 phlimit = phdr + ehdr->e_phnum; 150 nsegs = 0; 151 while (phdr < phlimit) { 152 switch (phdr->p_type) { 153 case PT_INTERP: 154 obj->interp = (void *)phdr->p_vaddr; 155 break; 156 157 case PT_LOAD: 158 if (nsegs < 2) 159 segs[nsegs] = phdr; 160 ++nsegs; 161 break; 162 163 case PT_DYNAMIC: 164 obj->dynamic = (void *)phdr->p_vaddr; 165 break; 166 } 167 168 ++phdr; 169 } 170 obj->entry = (void *)ehdr->e_entry; 171 if (!obj->dynamic) { 172 _rtld_error("%s: not dynamically linked", path); 173 goto bad; 174 } 175 if (nsegs != 2) { 176 _rtld_error("%s: wrong number of segments (%d != 2)", path, 177 nsegs); 178 goto bad; 179 } 180 181 /* 182 * Map the entire address space of the object as a file 183 * region to stake out our contiguous region and establish a 184 * base for relocation. We use a file mapping so that 185 * the kernel will give us whatever alignment is appropriate 186 * for the platform we're running on. 187 * 188 * We map it using the text protection, map the data segment 189 * into the right place, then map an anon segment for the bss 190 * and unmap the gaps left by padding to alignment. 191 */ 192 193 #ifdef MAP_ALIGNED 194 base_alignment = segs[0]->p_align; 195 #endif 196 base_offset = round_down(segs[0]->p_offset); 197 base_vaddr = round_down(segs[0]->p_vaddr); 198 base_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_memsz); 199 text_vlimit = round_up(segs[0]->p_vaddr + segs[0]->p_memsz); 200 text_flags = protflags(segs[0]->p_flags); 201 data_offset = round_down(segs[1]->p_offset); 202 data_vaddr = round_down(segs[1]->p_vaddr); 203 data_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_filesz); 204 data_flags = protflags(segs[1]->p_flags); 205 #ifdef RTLD_LOADER 206 clear_vaddr = segs[1]->p_vaddr + segs[1]->p_filesz; 207 #endif 208 209 obj->textsize = text_vlimit - base_vaddr; 210 obj->vaddrbase = base_vaddr; 211 obj->isdynamic = ehdr->e_type == ET_DYN; 212 213 munmap(ehdr, _rtld_pagesz); 214 ehdr = MAP_FAILED; 215 216 /* 217 * Calculate log2 of the base section alignment. 218 */ 219 mapflags = 0; 220 #ifdef MAP_ALIGNED 221 if (base_alignment > _rtld_pagesz) { 222 unsigned int log2 = 0; 223 for (; base_alignment > 1; base_alignment >>= 1) 224 log2++; 225 mapflags = MAP_ALIGNED(log2); 226 } 227 #endif 228 229 #ifdef RTLD_LOADER 230 base_addr = obj->isdynamic ? NULL : (caddr_t)base_vaddr; 231 #else 232 base_addr = NULL; 233 #endif 234 mapsize = base_vlimit - base_vaddr; 235 mapbase = mmap(base_addr, mapsize, text_flags, 236 mapflags | MAP_FILE | MAP_PRIVATE, fd, base_offset); 237 if (mapbase == MAP_FAILED) { 238 _rtld_error("mmap of entire address space failed: %s", 239 xstrerror(errno)); 240 goto bad; 241 } 242 243 /* Overlay the data segment onto the proper region. */ 244 data_addr = mapbase + (data_vaddr - base_vaddr); 245 if (mmap(data_addr, data_vlimit - data_vaddr, data_flags, 246 MAP_FILE | MAP_PRIVATE | MAP_FIXED, fd, data_offset) == 247 MAP_FAILED) { 248 _rtld_error("mmap of data failed: %s", xstrerror(errno)); 249 goto bad; 250 } 251 252 /* Overlay the bss segment onto the proper region. */ 253 if (mmap(mapbase + data_vlimit - base_vaddr, base_vlimit - data_vlimit, 254 data_flags, MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0) == 255 MAP_FAILED) { 256 _rtld_error("mmap of bss failed: %s", xstrerror(errno)); 257 goto bad; 258 } 259 260 /* Unmap the gap between the text and data. */ 261 gap_addr = mapbase + round_up(text_vlimit - base_vaddr); 262 gap_size = data_addr - gap_addr; 263 if (gap_size != 0 && mprotect(gap_addr, gap_size, PROT_NONE) == -1) { 264 _rtld_error("mprotect of text -> data gap failed: %s", 265 xstrerror(errno)); 266 goto bad; 267 } 268 269 #ifdef RTLD_LOADER 270 /* Clear any BSS in the last page of the data segment. */ 271 clear_addr = mapbase + (clear_vaddr - base_vaddr); 272 if ((nclear = data_vlimit - clear_vaddr) > 0) 273 memset(clear_addr, 0, nclear); 274 275 /* Non-file portion of BSS mapped above. */ 276 #endif 277 278 obj->mapbase = mapbase; 279 obj->mapsize = mapsize; 280 obj->relocbase = mapbase - base_vaddr; 281 282 if (obj->dynamic) 283 obj->dynamic = (void *)(obj->relocbase + (Elf_Addr)obj->dynamic); 284 if (obj->entry) 285 obj->entry = (void *)(obj->relocbase + (Elf_Addr)obj->entry); 286 if (obj->interp) 287 obj->interp = (void *)(obj->relocbase + (Elf_Addr)obj->interp); 288 289 return obj; 290 291 bad: 292 if (ehdr != MAP_FAILED) 293 munmap(ehdr, _rtld_pagesz); 294 if (mapbase != MAP_FAILED) 295 munmap(mapbase, mapsize); 296 _rtld_obj_free(obj); 297 return NULL; 298 } 299 300 void 301 _rtld_obj_free(obj) 302 Obj_Entry *obj; 303 { 304 Objlist_Entry *elm; 305 306 free(obj->path); 307 while (obj->needed != NULL) { 308 Needed_Entry *needed = obj->needed; 309 obj->needed = needed->next; 310 free(needed); 311 } 312 while ((elm = SIMPLEQ_FIRST(&obj->dldags)) != NULL) { 313 SIMPLEQ_REMOVE_HEAD(&obj->dldags, link); 314 free(elm); 315 } 316 while ((elm = SIMPLEQ_FIRST(&obj->dagmembers)) != NULL) { 317 SIMPLEQ_REMOVE_HEAD(&obj->dagmembers, link); 318 free(elm); 319 } 320 free(obj); 321 } 322 323 Obj_Entry * 324 _rtld_obj_new(void) 325 { 326 Obj_Entry *obj; 327 328 obj = CNEW(Obj_Entry); 329 SIMPLEQ_INIT(&obj->dldags); 330 SIMPLEQ_INIT(&obj->dagmembers); 331 return obj; 332 } 333 334 /* 335 * Given a set of ELF protection flags, return the corresponding protection 336 * flags for MMAP. 337 */ 338 static int 339 protflags(elfflags) 340 int elfflags; 341 { 342 int prot = 0; 343 if (elfflags & PF_R) 344 prot |= PROT_READ; 345 #ifdef RTLD_LOADER 346 if (elfflags & PF_W) 347 prot |= PROT_WRITE; 348 #endif 349 if (elfflags & PF_X) 350 prot |= PROT_EXEC; 351 return prot; 352 } 353
Indexes created Fri Sep 26 08:10:20 GMT 2025