map_object.c revision 1.25
1 /* $NetBSD: map_object.c,v 1.25 2002/12/05 04:56:57 junyoung 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 Elf_Off base_offset; 70 Elf_Addr base_vaddr; 71 Elf_Addr base_vlimit; 72 Elf_Addr text_vlimit; 73 int text_flags; 74 caddr_t base_addr; 75 Elf_Off data_offset; 76 Elf_Addr data_vaddr; 77 Elf_Addr data_vlimit; 78 int data_flags; 79 caddr_t data_addr; 80 caddr_t gap_addr; 81 size_t gap_size; 82 #ifdef RTLD_LOADER 83 Elf_Addr clear_vaddr; 84 caddr_t clear_addr; 85 size_t nclear; 86 #endif 87 88 obj = _rtld_obj_new(); 89 obj->path = path; 90 obj->pathlen = strlen(path); 91 if (sb != NULL) { 92 obj->dev = sb->st_dev; 93 obj->ino = sb->st_ino; 94 } 95 96 ehdr = mmap(NULL, _rtld_pagesz, PROT_READ, MAP_FILE | MAP_SHARED, fd, 97 (off_t)0); 98 if (ehdr == MAP_FAILED) { 99 _rtld_error("%s: read error: %s", path, xstrerror(errno)); 100 goto bad; 101 } 102 /* Make sure the file is valid */ 103 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0 || 104 ehdr->e_ident[EI_CLASS] != ELFCLASS) { 105 _rtld_error("%s: unrecognized file format", path); 106 goto bad; 107 } 108 /* Elf_e_ident includes class */ 109 if (ehdr->e_ident[EI_VERSION] != EV_CURRENT || 110 ehdr->e_version != EV_CURRENT || 111 ehdr->e_ident[EI_DATA] != ELFDEFNNAME(MACHDEP_ENDIANNESS)) { 112 _rtld_error("%s: unsupported file version", path); 113 goto bad; 114 } 115 if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) { 116 _rtld_error("%s: unsupported file type", path); 117 goto bad; 118 } 119 switch (ehdr->e_machine) { 120 ELFDEFNNAME(MACHDEP_ID_CASES) 121 default: 122 _rtld_error("%s: unsupported machine", path); 123 goto bad; 124 } 125 126 /* 127 * We rely on the program header being in the first page. This is 128 * not strictly required by the ABI specification, but it seems to 129 * always true in practice. And, it simplifies things considerably. 130 */ 131 assert(ehdr->e_phentsize == sizeof(Elf_Phdr)); 132 assert(ehdr->e_phoff + ehdr->e_phnum * sizeof(Elf_Phdr) <= 133 _rtld_pagesz); 134 135 /* 136 * Scan the program header entries, and save key information. 137 * 138 * We rely on there being exactly two load segments, text and data, 139 * in that order. 140 */ 141 phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff); 142 phlimit = phdr + ehdr->e_phnum; 143 nsegs = 0; 144 while (phdr < phlimit) { 145 switch (phdr->p_type) { 146 case PT_INTERP: 147 obj->interp = (void *)phdr->p_vaddr; 148 break; 149 150 case PT_LOAD: 151 if (nsegs < 2) 152 segs[nsegs] = phdr; 153 ++nsegs; 154 break; 155 156 case PT_DYNAMIC: 157 obj->dynamic = (void *)phdr->p_vaddr; 158 break; 159 } 160 161 ++phdr; 162 } 163 obj->entry = (void *)ehdr->e_entry; 164 if (!obj->dynamic) { 165 _rtld_error("%s: not dynamically linked", path); 166 goto bad; 167 } 168 if (nsegs != 2) { 169 _rtld_error("%s: wrong number of segments (%d != 2)", path, 170 nsegs); 171 goto bad; 172 } 173 174 /* 175 * Map the entire address space of the object as a file 176 * region to stake out our contiguous region and establish a 177 * base for relocation. We use a file mapping so that 178 * the kernel will give us whatever alignment is appropriate 179 * for the platform we're running on. 180 * 181 * We map it using the text protection, map the data segment 182 * into the right place, then map an anon segment for the bss 183 * and unmap the gaps left by padding to alignment. 184 */ 185 186 base_offset = round_down(segs[0]->p_offset); 187 base_vaddr = round_down(segs[0]->p_vaddr); 188 base_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_memsz); 189 text_vlimit = round_up(segs[0]->p_vaddr + segs[0]->p_memsz); 190 text_flags = protflags(segs[0]->p_flags); 191 data_offset = round_down(segs[1]->p_offset); 192 data_vaddr = round_down(segs[1]->p_vaddr); 193 data_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_filesz); 194 data_flags = protflags(segs[1]->p_flags); 195 #ifdef RTLD_LOADER 196 clear_vaddr = segs[1]->p_vaddr + segs[1]->p_filesz; 197 #endif 198 199 obj->textsize = text_vlimit - base_vaddr; 200 obj->vaddrbase = base_vaddr; 201 obj->isdynamic = ehdr->e_type == ET_DYN; 202 203 munmap(ehdr, _rtld_pagesz); 204 ehdr = MAP_FAILED; 205 206 #ifdef RTLD_LOADER 207 base_addr = obj->isdynamic ? NULL : (caddr_t)base_vaddr; 208 #else 209 base_addr = NULL; 210 #endif 211 mapsize = base_vlimit - base_vaddr; 212 mapbase = mmap(base_addr, mapsize, text_flags, MAP_FILE | MAP_PRIVATE, 213 fd, base_offset); 214 if (mapbase == MAP_FAILED) { 215 _rtld_error("mmap of entire address space failed: %s", 216 xstrerror(errno)); 217 goto bad; 218 } 219 220 /* Overlay the data segment onto the proper region. */ 221 data_addr = mapbase + (data_vaddr - base_vaddr); 222 if (mmap(data_addr, data_vlimit - data_vaddr, data_flags, 223 MAP_FILE | MAP_PRIVATE | MAP_FIXED, fd, data_offset) == 224 MAP_FAILED) { 225 _rtld_error("mmap of data failed: %s", xstrerror(errno)); 226 goto bad; 227 } 228 229 /* Overlay the bss segment onto the proper region. */ 230 if (mmap(mapbase + data_vlimit - base_vaddr, base_vlimit - data_vlimit, 231 data_flags, MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0) == 232 MAP_FAILED) { 233 _rtld_error("mmap of bss failed: %s", xstrerror(errno)); 234 goto bad; 235 } 236 237 /* Unmap the gap between the text and data. */ 238 gap_addr = mapbase + round_up(text_vlimit - base_vaddr); 239 gap_size = data_addr - gap_addr; 240 if (gap_size != 0 && mprotect(gap_addr, gap_size, PROT_NONE) == -1) { 241 _rtld_error("mprotect of text -> data gap failed: %s", 242 xstrerror(errno)); 243 goto bad; 244 } 245 246 #ifdef RTLD_LOADER 247 /* Clear any BSS in the last page of the data segment. */ 248 clear_addr = mapbase + (clear_vaddr - base_vaddr); 249 if ((nclear = data_vlimit - clear_vaddr) > 0) 250 memset(clear_addr, 0, nclear); 251 252 /* Non-file portion of BSS mapped above. */ 253 #endif 254 255 obj->mapbase = mapbase; 256 obj->mapsize = mapsize; 257 obj->relocbase = mapbase - base_vaddr; 258 259 if (obj->dynamic) 260 obj->dynamic = (void *)(obj->relocbase + (Elf_Addr)obj->dynamic); 261 if (obj->entry) 262 obj->entry = (void *)(obj->relocbase + (Elf_Addr)obj->entry); 263 if (obj->interp) 264 obj->interp = (void *)(obj->relocbase + (Elf_Addr)obj->interp); 265 266 return obj; 267 268 bad: 269 if (ehdr != MAP_FAILED) 270 munmap(ehdr, _rtld_pagesz); 271 if (mapbase != MAP_FAILED) 272 munmap(mapbase, mapsize); 273 _rtld_obj_free(obj); 274 return NULL; 275 } 276 277 void 278 _rtld_obj_free(obj) 279 Obj_Entry *obj; 280 { 281 Objlist_Entry *elm; 282 283 free(obj->path); 284 while (obj->needed != NULL) { 285 Needed_Entry *needed = obj->needed; 286 obj->needed = needed->next; 287 free(needed); 288 } 289 while ((elm = SIMPLEQ_FIRST(&obj->dldags)) != NULL) { 290 SIMPLEQ_REMOVE_HEAD(&obj->dldags, link); 291 free(elm); 292 } 293 while ((elm = SIMPLEQ_FIRST(&obj->dagmembers)) != NULL) { 294 SIMPLEQ_REMOVE_HEAD(&obj->dagmembers, link); 295 free(elm); 296 } 297 free(obj); 298 } 299 300 Obj_Entry * 301 _rtld_obj_new(void) 302 { 303 Obj_Entry *obj; 304 305 obj = CNEW(Obj_Entry); 306 SIMPLEQ_INIT(&obj->dldags); 307 SIMPLEQ_INIT(&obj->dagmembers); 308 return obj; 309 } 310 311 /* 312 * Given a set of ELF protection flags, return the corresponding protection 313 * flags for MMAP. 314 */ 315 static int 316 protflags(elfflags) 317 int elfflags; 318 { 319 int prot = 0; 320 if (elfflags & PF_R) 321 prot |= PROT_READ; 322 #ifdef RTLD_LOADER 323 if (elfflags & PF_W) 324 prot |= PROT_WRITE; 325 #endif 326 if (elfflags & PF_X) 327 prot |= PROT_EXEC; 328 return prot; 329 } 330
Indexes created Sun Sep 28 16:09:52 GMT 2025