map_object.c revision 1.22
1 /* $NetBSD: map_object.c,v 1.22 2002/10/04 18:50:43 mycroft Exp $ */ 2 3 /* 4 * Copyright 1996 John D. Polstra. 5 * Copyright 1996 Matt Thomas <matt (at) 3am-software.com> 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by John Polstra. 19 * 4. The name of the author may not be used to endorse or promote products 20 * derived from this software without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 23 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 24 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 25 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 26 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 27 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 28 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 29 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 30 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 31 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 32 */ 33 34 #include <errno.h> 35 #include <stddef.h> 36 #include <stdlib.h> 37 #include <string.h> 38 #include <unistd.h> 39 #include <sys/stat.h> 40 #include <sys/types.h> 41 #include <sys/mman.h> 42 43 #include "rtld.h" 44 45 static int protflags __P((int)); /* Elf flags -> mmap protection */ 46 47 /* 48 * Map a shared object into memory. The argument is a file descriptor, 49 * which must be open on the object and positioned at its beginning. 50 * 51 * The return value is a pointer to a newly-allocated Obj_Entry structure 52 * for the shared object. Returns NULL on failure. 53 */ 54 Obj_Entry * 55 _rtld_map_object(path, fd, sb) 56 char *path; 57 int fd; 58 const struct stat *sb; 59 { 60 Obj_Entry *obj; 61 Elf_Ehdr *ehdr; 62 Elf_Phdr *phdr; 63 Elf_Phdr *phlimit; 64 Elf_Phdr *segs[2]; 65 int nsegs; 66 caddr_t mapbase = MAP_FAILED; 67 size_t mapsize; 68 Elf_Off base_offset; 69 Elf_Addr base_vaddr; 70 Elf_Addr base_vlimit; 71 Elf_Addr text_vlimit; 72 int text_flags; 73 caddr_t base_addr; 74 Elf_Off data_offset; 75 Elf_Addr data_vaddr; 76 Elf_Addr data_vlimit; 77 int data_flags; 78 caddr_t data_addr; 79 caddr_t gap_addr; 80 size_t gap_size; 81 #ifdef RTLD_LOADER 82 Elf_Addr clear_vaddr; 83 caddr_t clear_addr; 84 size_t nclear; 85 #endif 86 87 obj = _rtld_obj_new(); 88 obj->path = path; 89 if (sb != NULL) { 90 obj->dev = sb->st_dev; 91 obj->ino = sb->st_ino; 92 } 93 94 ehdr = mmap(NULL, _rtld_pagesz, PROT_READ, MAP_FILE | MAP_SHARED, fd, 95 (off_t)0); 96 if (ehdr == MAP_FAILED) { 97 _rtld_error("%s: read error: %s", path, xstrerror(errno)); 98 goto bad; 99 } 100 /* Make sure the file is valid */ 101 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0 || 102 ehdr->e_ident[EI_CLASS] != ELFCLASS) { 103 _rtld_error("%s: unrecognized file format", path); 104 goto bad; 105 } 106 /* Elf_e_ident includes class */ 107 if (ehdr->e_ident[EI_VERSION] != EV_CURRENT || 108 ehdr->e_version != EV_CURRENT || 109 ehdr->e_ident[EI_DATA] != ELFDEFNNAME(MACHDEP_ENDIANNESS)) { 110 _rtld_error("%s: unsupported file version", path); 111 goto bad; 112 } 113 if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) { 114 _rtld_error("%s: unsupported file type", path); 115 goto bad; 116 } 117 switch (ehdr->e_machine) { 118 ELFDEFNNAME(MACHDEP_ID_CASES) 119 default: 120 _rtld_error("%s: unsupported machine", path); 121 goto bad; 122 } 123 124 /* 125 * We rely on the program header being in the first page. This is 126 * not strictly required by the ABI specification, but it seems to 127 * always true in practice. And, it simplifies things considerably. 128 */ 129 assert(ehdr->e_phentsize == sizeof(Elf_Phdr)); 130 assert(ehdr->e_phoff + ehdr->e_phnum * sizeof(Elf_Phdr) <= 131 _rtld_pagesz); 132 133 /* 134 * Scan the program header entries, and save key information. 135 * 136 * We rely on there being exactly two load segments, text and data, 137 * in that order. 138 */ 139 phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff); 140 phlimit = phdr + ehdr->e_phnum; 141 nsegs = 0; 142 while (phdr < phlimit) { 143 switch (phdr->p_type) { 144 case PT_INTERP: 145 obj->interp = (void *)phdr->p_vaddr; 146 break; 147 148 case PT_LOAD: 149 if (nsegs < 2) 150 segs[nsegs] = phdr; 151 ++nsegs; 152 break; 153 154 case PT_DYNAMIC: 155 obj->dynamic = (void *)phdr->p_vaddr; 156 break; 157 } 158 159 ++phdr; 160 } 161 obj->entry = (void *)ehdr->e_entry; 162 if (!obj->dynamic) { 163 _rtld_error("%s: not dynamically linked", path); 164 goto bad; 165 } 166 if (nsegs != 2) { 167 _rtld_error("%s: wrong number of segments (%d != 2)", path, 168 nsegs); 169 goto bad; 170 } 171 172 /* 173 * Map the entire address space of the object as a file 174 * region to stake out our contiguous region and establish a 175 * base for relocation. We use a file mapping so that 176 * the kernel will give us whatever alignment is appropriate 177 * for the platform we're running on. 178 * 179 * We map it using the text protection, map the data segment 180 * into the right place, then map an anon segment for the bss 181 * and unmap the gaps left by padding to alignment. 182 */ 183 184 base_offset = round_down(segs[0]->p_offset); 185 base_vaddr = round_down(segs[0]->p_vaddr); 186 base_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_memsz); 187 text_vlimit = round_up(segs[0]->p_vaddr + segs[0]->p_memsz); 188 text_flags = protflags(segs[0]->p_flags); 189 data_offset = round_down(segs[1]->p_offset); 190 data_vaddr = round_down(segs[1]->p_vaddr); 191 data_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_filesz); 192 data_flags = protflags(segs[1]->p_flags); 193 clear_vaddr = segs[1]->p_vaddr + segs[1]->p_filesz; 194 195 obj->textsize = text_vlimit - base_vaddr; 196 obj->vaddrbase = base_vaddr; 197 obj->isdynamic = ehdr->e_type == ET_DYN; 198 199 munmap(ehdr, _rtld_pagesz); 200 ehdr = MAP_FAILED; 201 202 #ifdef RTLD_LOADER 203 base_addr = obj->isdynamic ? NULL : (caddr_t)base_vaddr; 204 #else 205 base_addr = NULL; 206 #endif 207 mapsize = base_vlimit - base_vaddr; 208 mapbase = mmap(base_addr, mapsize, text_flags, MAP_FILE | MAP_PRIVATE, 209 fd, base_offset); 210 if (mapbase == MAP_FAILED) { 211 _rtld_error("mmap of entire address space failed: %s", 212 xstrerror(errno)); 213 goto bad; 214 } 215 216 /* Overlay the data segment onto the proper region. */ 217 data_addr = mapbase + (data_vaddr - base_vaddr); 218 if (mmap(data_addr, data_vlimit - data_vaddr, data_flags, 219 MAP_FILE | MAP_PRIVATE | MAP_FIXED, fd, data_offset) == 220 MAP_FAILED) { 221 _rtld_error("mmap of data failed: %s", xstrerror(errno)); 222 goto bad; 223 } 224 225 /* Overlay the bss segment onto the proper region. */ 226 if (mmap(mapbase + data_vlimit - base_vaddr, base_vlimit - data_vlimit, 227 data_flags, MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0) == 228 MAP_FAILED) { 229 _rtld_error("mmap of bss failed: %s", xstrerror(errno)); 230 goto bad; 231 } 232 233 /* Unmap the gap between the text and data. */ 234 gap_addr = mapbase + round_up(text_vlimit - base_vaddr); 235 gap_size = data_addr - gap_addr; 236 if (gap_size != 0 && mprotect(gap_addr, gap_size, PROT_NONE) == -1) { 237 _rtld_error("mprotect of text -> data gap failed: %s", 238 xstrerror(errno)); 239 goto bad; 240 } 241 242 #ifdef RTLD_LOADER 243 /* Clear any BSS in the last page of the data segment. */ 244 clear_addr = mapbase + (clear_vaddr - base_vaddr); 245 if ((nclear = data_vlimit - clear_vaddr) > 0) 246 memset(clear_addr, 0, nclear); 247 248 /* Non-file portion of BSS mapped above. */ 249 #endif 250 251 obj->mapbase = mapbase; 252 obj->mapsize = mapsize; 253 obj->relocbase = mapbase - base_vaddr; 254 255 if (obj->dynamic) 256 obj->dynamic = (void *)(obj->relocbase + (Elf_Addr)obj->dynamic); 257 if (obj->entry) 258 obj->entry = (void *)(obj->relocbase + (Elf_Addr)obj->entry); 259 if (obj->interp) 260 obj->interp = (void *)(obj->relocbase + (Elf_Addr)obj->interp); 261 262 return obj; 263 264 bad: 265 if (ehdr != MAP_FAILED) 266 munmap(ehdr, _rtld_pagesz); 267 if (mapbase != MAP_FAILED) 268 munmap(mapbase, mapsize); 269 _rtld_obj_free(obj); 270 return NULL; 271 } 272 273 void 274 _rtld_obj_free(obj) 275 Obj_Entry *obj; 276 { 277 Objlist_Entry *elm; 278 279 free(obj->path); 280 while (obj->needed != NULL) { 281 Needed_Entry *needed = obj->needed; 282 obj->needed = needed->next; 283 free(needed); 284 } 285 while ((elm = SIMPLEQ_FIRST(&obj->dldags)) != NULL) { 286 SIMPLEQ_REMOVE_HEAD(&obj->dldags, link); 287 free(elm); 288 } 289 while ((elm = SIMPLEQ_FIRST(&obj->dagmembers)) != NULL) { 290 SIMPLEQ_REMOVE_HEAD(&obj->dagmembers, link); 291 free(elm); 292 } 293 free(obj); 294 } 295 296 Obj_Entry * 297 _rtld_obj_new(void) 298 { 299 Obj_Entry *obj; 300 301 obj = CNEW(Obj_Entry); 302 SIMPLEQ_INIT(&obj->dldags); 303 SIMPLEQ_INIT(&obj->dagmembers); 304 return obj; 305 } 306 307 /* 308 * Given a set of ELF protection flags, return the corresponding protection 309 * flags for MMAP. 310 */ 311 static int 312 protflags(elfflags) 313 int elfflags; 314 { 315 int prot = 0; 316 if (elfflags & PF_R) 317 prot |= PROT_READ; 318 #ifdef RTLD_LOADER 319 if (elfflags & PF_W) 320 prot |= PROT_WRITE; 321 #endif 322 if (elfflags & PF_X) 323 prot |= PROT_EXEC; 324 return prot; 325 } 326
Indexes created Fri Sep 26 08:10:20 GMT 2025