1 /* $NetBSD: map_object.c,v 1.30 2003/07/24 10:12:25 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 <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(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(char *path, int fd, const struct stat *sb) 57 { 58 Obj_Entry *obj; 59 Elf_Ehdr *ehdr; 60 Elf_Phdr *phdr; 61 Elf_Phdr *phlimit; 62 Elf_Phdr *segs[2]; 63 int nsegs; 64 caddr_t mapbase = MAP_FAILED; 65 size_t mapsize; 66 int mapflags; 67 Elf_Off base_offset; 68 #ifdef MAP_ALIGNED 69 Elf_Addr base_alignment; 70 #endif 71 Elf_Addr base_vaddr; 72 Elf_Addr base_vlimit; 73 Elf_Addr text_vlimit; 74 int text_flags; 75 caddr_t base_addr; 76 Elf_Off data_offset; 77 Elf_Addr data_vaddr; 78 Elf_Addr data_vlimit; 79 int data_flags; 80 caddr_t data_addr; 81 caddr_t gap_addr; 82 size_t gap_size; 83 #ifdef RTLD_LOADER 84 Elf_Addr clear_vaddr; 85 caddr_t clear_addr; 86 size_t nclear; 87 #endif 88 89 if (sb != NULL && sb->st_size < sizeof (Elf_Ehdr)) { 90 _rtld_error("%s: unrecognized file format", path); 91 return NULL; 92 } 93 94 obj = _rtld_obj_new(); 95 obj->path = path; 96 obj->pathlen = strlen(path); 97 if (sb != NULL) { 98 obj->dev = sb->st_dev; 99 obj->ino = sb->st_ino; 100 } 101 102 ehdr = mmap(NULL, _rtld_pagesz, PROT_READ, MAP_FILE | MAP_SHARED, fd, 103 (off_t)0); 104 if (ehdr == MAP_FAILED) { 105 _rtld_error("%s: read error: %s", path, xstrerror(errno)); 106 goto bad; 107 } 108 /* Make sure the file is valid */ 109 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0 || 110 ehdr->e_ident[EI_CLASS] != ELFCLASS) { 111 _rtld_error("%s: unrecognized file format", path); 112 goto bad; 113 } 114 /* Elf_e_ident includes class */ 115 if (ehdr->e_ident[EI_VERSION] != EV_CURRENT || 116 ehdr->e_version != EV_CURRENT || 117 ehdr->e_ident[EI_DATA] != ELFDEFNNAME(MACHDEP_ENDIANNESS)) { 118 _rtld_error("%s: unsupported file version", path); 119 goto bad; 120 } 121 if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) { 122 _rtld_error("%s: unsupported file type", path); 123 goto bad; 124 } 125 switch (ehdr->e_machine) { 126 ELFDEFNNAME(MACHDEP_ID_CASES) 127 default: 128 _rtld_error("%s: unsupported machine", path); 129 goto bad; 130 } 131 132 /* 133 * We rely on the program header being in the first page. This is 134 * not strictly required by the ABI specification, but it seems to 135 * always true in practice. And, it simplifies things considerably. 136 */ 137 assert(ehdr->e_phentsize == sizeof(Elf_Phdr)); 138 assert(ehdr->e_phoff + ehdr->e_phnum * sizeof(Elf_Phdr) <= 139 _rtld_pagesz); 140 141 /* 142 * Scan the program header entries, and save key information. 143 * 144 * We rely on there being exactly two load segments, text and data, 145 * in that order. 146 */ 147 phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff); 148 phlimit = phdr + ehdr->e_phnum; 149 nsegs = 0; 150 while (phdr < phlimit) { 151 switch (phdr->p_type) { 152 case PT_INTERP: 153 obj->interp = (void *)phdr->p_vaddr; 154 break; 155 156 case PT_LOAD: 157 if (nsegs < 2) 158 segs[nsegs] = phdr; 159 ++nsegs; 160 break; 161 162 case PT_DYNAMIC: 163 obj->dynamic = (void *)phdr->p_vaddr; 164 break; 165 } 166 167 ++phdr; 168 } 169 obj->entry = (void *)ehdr->e_entry; 170 if (!obj->dynamic) { 171 _rtld_error("%s: not dynamically linked", path); 172 goto bad; 173 } 174 if (nsegs != 2) { 175 _rtld_error("%s: wrong number of segments (%d != 2)", path, 176 nsegs); 177 goto bad; 178 } 179 180 /* 181 * Map the entire address space of the object as a file 182 * region to stake out our contiguous region and establish a 183 * base for relocation. We use a file mapping so that 184 * the kernel will give us whatever alignment is appropriate 185 * for the platform we're running on. 186 * 187 * We map it using the text protection, map the data segment 188 * into the right place, then map an anon segment for the bss 189 * and unmap the gaps left by padding to alignment. 190 */ 191 192 #ifdef MAP_ALIGNED 193 base_alignment = segs[0]->p_align; 194 #endif 195 base_offset = round_down(segs[0]->p_offset); 196 base_vaddr = round_down(segs[0]->p_vaddr); 197 base_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_memsz); 198 text_vlimit = round_up(segs[0]->p_vaddr + segs[0]->p_memsz); 199 text_flags = protflags(segs[0]->p_flags); 200 data_offset = round_down(segs[1]->p_offset); 201 data_vaddr = round_down(segs[1]->p_vaddr); 202 data_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_filesz); 203 data_flags = protflags(segs[1]->p_flags); 204 #ifdef RTLD_LOADER 205 clear_vaddr = segs[1]->p_vaddr + segs[1]->p_filesz; 206 #endif 207 208 obj->textsize = text_vlimit - base_vaddr; 209 obj->vaddrbase = base_vaddr; 210 obj->isdynamic = ehdr->e_type == ET_DYN; 211 212 munmap(ehdr, _rtld_pagesz); 213 ehdr = MAP_FAILED; 214 215 /* 216 * Calculate log2 of the base section alignment. 217 */ 218 mapflags = 0; 219 #ifdef MAP_ALIGNED 220 if (base_alignment > _rtld_pagesz) { 221 unsigned int log2 = 0; 222 for (; base_alignment > 1; base_alignment >>= 1) 223 log2++; 224 mapflags = MAP_ALIGNED(log2); 225 } 226 #endif 227 228 #ifdef RTLD_LOADER 229 base_addr = obj->isdynamic ? NULL : (caddr_t)base_vaddr; 230 #else 231 base_addr = NULL; 232 #endif 233 mapsize = base_vlimit - base_vaddr; 234 mapbase = mmap(base_addr, mapsize, text_flags, 235 mapflags | MAP_FILE | MAP_PRIVATE, fd, base_offset); 236 if (mapbase == MAP_FAILED) { 237 _rtld_error("mmap of entire address space failed: %s", 238 xstrerror(errno)); 239 goto bad; 240 } 241 242 /* Overlay the data segment onto the proper region. */ 243 data_addr = mapbase + (data_vaddr - base_vaddr); 244 if (mmap(data_addr, data_vlimit - data_vaddr, data_flags, 245 MAP_FILE | MAP_PRIVATE | MAP_FIXED, fd, data_offset) == 246 MAP_FAILED) { 247 _rtld_error("mmap of data failed: %s", xstrerror(errno)); 248 goto bad; 249 } 250 251 /* Overlay the bss segment onto the proper region. */ 252 if (mmap(mapbase + data_vlimit - base_vaddr, base_vlimit - data_vlimit, 253 data_flags, MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0) == 254 MAP_FAILED) { 255 _rtld_error("mmap of bss failed: %s", xstrerror(errno)); 256 goto bad; 257 } 258 259 /* Unmap the gap between the text and data. */ 260 gap_addr = mapbase + round_up(text_vlimit - base_vaddr); 261 gap_size = data_addr - gap_addr; 262 if (gap_size != 0 && mprotect(gap_addr, gap_size, PROT_NONE) == -1) { 263 _rtld_error("mprotect of text -> data gap failed: %s", 264 xstrerror(errno)); 265 goto bad; 266 } 267 268 #ifdef RTLD_LOADER 269 /* Clear any BSS in the last page of the data segment. */ 270 clear_addr = mapbase + (clear_vaddr - base_vaddr); 271 if ((nclear = data_vlimit - clear_vaddr) > 0) 272 memset(clear_addr, 0, nclear); 273 274 /* Non-file portion of BSS mapped above. */ 275 #endif 276 277 obj->mapbase = mapbase; 278 obj->mapsize = mapsize; 279 obj->relocbase = mapbase - base_vaddr; 280 281 if (obj->dynamic) 282 obj->dynamic = (void *)(obj->relocbase + (Elf_Addr)obj->dynamic); 283 if (obj->entry) 284 obj->entry = (void *)(obj->relocbase + (Elf_Addr)obj->entry); 285 if (obj->interp) 286 obj->interp = (void *)(obj->relocbase + (Elf_Addr)obj->interp); 287 288 return obj; 289 290 bad: 291 if (ehdr != MAP_FAILED) 292 munmap(ehdr, _rtld_pagesz); 293 if (mapbase != MAP_FAILED) 294 munmap(mapbase, mapsize); 295 _rtld_obj_free(obj); 296 return NULL; 297 } 298 299 void 300 _rtld_obj_free(Obj_Entry *obj) 301 { 302 Objlist_Entry *elm; 303 304 free(obj->path); 305 while (obj->needed != NULL) { 306 Needed_Entry *needed = obj->needed; 307 obj->needed = needed->next; 308 free(needed); 309 } 310 while ((elm = SIMPLEQ_FIRST(&obj->dldags)) != NULL) { 311 SIMPLEQ_REMOVE_HEAD(&obj->dldags, link); 312 free(elm); 313 } 314 while ((elm = SIMPLEQ_FIRST(&obj->dagmembers)) != NULL) { 315 SIMPLEQ_REMOVE_HEAD(&obj->dagmembers, link); 316 free(elm); 317 } 318 free(obj); 319 } 320 321 Obj_Entry * 322 _rtld_obj_new(void) 323 { 324 Obj_Entry *obj; 325 326 obj = CNEW(Obj_Entry); 327 SIMPLEQ_INIT(&obj->dldags); 328 SIMPLEQ_INIT(&obj->dagmembers); 329 return obj; 330 } 331 332 /* 333 * Given a set of ELF protection flags, return the corresponding protection 334 * flags for MMAP. 335 */ 336 static int 337 protflags(int elfflags) 338 { 339 int prot = 0; 340 341 if (elfflags & PF_R) 342 prot |= PROT_READ; 343 #ifdef RTLD_LOADER 344 if (elfflags & PF_W) 345 prot |= PROT_WRITE; 346 #endif 347 if (elfflags & PF_X) 348 prot |= PROT_EXEC; 349 return prot; 350 } 351