map_object.c revision 1.24
1 /* $NetBSD: map_object.c,v 1.24 2002/10/05 11:59:04 mycroft 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 if (sb != NULL) { 91 obj->dev = sb->st_dev; 92 obj->ino = sb->st_ino; 93 } 94 95 ehdr = mmap(NULL, _rtld_pagesz, PROT_READ, MAP_FILE | MAP_SHARED, fd, 96 (off_t)0); 97 if (ehdr == MAP_FAILED) { 98 _rtld_error("%s: read error: %s", path, xstrerror(errno)); 99 goto bad; 100 } 101 /* Make sure the file is valid */ 102 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0 || 103 ehdr->e_ident[EI_CLASS] != ELFCLASS) { 104 _rtld_error("%s: unrecognized file format", path); 105 goto bad; 106 } 107 /* Elf_e_ident includes class */ 108 if (ehdr->e_ident[EI_VERSION] != EV_CURRENT || 109 ehdr->e_version != EV_CURRENT || 110 ehdr->e_ident[EI_DATA] != ELFDEFNNAME(MACHDEP_ENDIANNESS)) { 111 _rtld_error("%s: unsupported file version", path); 112 goto bad; 113 } 114 if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) { 115 _rtld_error("%s: unsupported file type", path); 116 goto bad; 117 } 118 switch (ehdr->e_machine) { 119 ELFDEFNNAME(MACHDEP_ID_CASES) 120 default: 121 _rtld_error("%s: unsupported machine", path); 122 goto bad; 123 } 124 125 /* 126 * We rely on the program header being in the first page. This is 127 * not strictly required by the ABI specification, but it seems to 128 * always true in practice. And, it simplifies things considerably. 129 */ 130 assert(ehdr->e_phentsize == sizeof(Elf_Phdr)); 131 assert(ehdr->e_phoff + ehdr->e_phnum * sizeof(Elf_Phdr) <= 132 _rtld_pagesz); 133 134 /* 135 * Scan the program header entries, and save key information. 136 * 137 * We rely on there being exactly two load segments, text and data, 138 * in that order. 139 */ 140 phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff); 141 phlimit = phdr + ehdr->e_phnum; 142 nsegs = 0; 143 while (phdr < phlimit) { 144 switch (phdr->p_type) { 145 case PT_INTERP: 146 obj->interp = (void *)phdr->p_vaddr; 147 break; 148 149 case PT_LOAD: 150 if (nsegs < 2) 151 segs[nsegs] = phdr; 152 ++nsegs; 153 break; 154 155 case PT_DYNAMIC: 156 obj->dynamic = (void *)phdr->p_vaddr; 157 break; 158 } 159 160 ++phdr; 161 } 162 obj->entry = (void *)ehdr->e_entry; 163 if (!obj->dynamic) { 164 _rtld_error("%s: not dynamically linked", path); 165 goto bad; 166 } 167 if (nsegs != 2) { 168 _rtld_error("%s: wrong number of segments (%d != 2)", path, 169 nsegs); 170 goto bad; 171 } 172 173 /* 174 * Map the entire address space of the object as a file 175 * region to stake out our contiguous region and establish a 176 * base for relocation. We use a file mapping so that 177 * the kernel will give us whatever alignment is appropriate 178 * for the platform we're running on. 179 * 180 * We map it using the text protection, map the data segment 181 * into the right place, then map an anon segment for the bss 182 * and unmap the gaps left by padding to alignment. 183 */ 184 185 base_offset = round_down(segs[0]->p_offset); 186 base_vaddr = round_down(segs[0]->p_vaddr); 187 base_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_memsz); 188 text_vlimit = round_up(segs[0]->p_vaddr + segs[0]->p_memsz); 189 text_flags = protflags(segs[0]->p_flags); 190 data_offset = round_down(segs[1]->p_offset); 191 data_vaddr = round_down(segs[1]->p_vaddr); 192 data_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_filesz); 193 data_flags = protflags(segs[1]->p_flags); 194 #ifdef RTLD_LOADER 195 clear_vaddr = segs[1]->p_vaddr + segs[1]->p_filesz; 196 #endif 197 198 obj->textsize = text_vlimit - base_vaddr; 199 obj->vaddrbase = base_vaddr; 200 obj->isdynamic = ehdr->e_type == ET_DYN; 201 202 munmap(ehdr, _rtld_pagesz); 203 ehdr = MAP_FAILED; 204 205 #ifdef RTLD_LOADER 206 base_addr = obj->isdynamic ? NULL : (caddr_t)base_vaddr; 207 #else 208 base_addr = NULL; 209 #endif 210 mapsize = base_vlimit - base_vaddr; 211 mapbase = mmap(base_addr, mapsize, text_flags, MAP_FILE | MAP_PRIVATE, 212 fd, base_offset); 213 if (mapbase == MAP_FAILED) { 214 _rtld_error("mmap of entire address space failed: %s", 215 xstrerror(errno)); 216 goto bad; 217 } 218 219 /* Overlay the data segment onto the proper region. */ 220 data_addr = mapbase + (data_vaddr - base_vaddr); 221 if (mmap(data_addr, data_vlimit - data_vaddr, data_flags, 222 MAP_FILE | MAP_PRIVATE | MAP_FIXED, fd, data_offset) == 223 MAP_FAILED) { 224 _rtld_error("mmap of data failed: %s", xstrerror(errno)); 225 goto bad; 226 } 227 228 /* Overlay the bss segment onto the proper region. */ 229 if (mmap(mapbase + data_vlimit - base_vaddr, base_vlimit - data_vlimit, 230 data_flags, MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0) == 231 MAP_FAILED) { 232 _rtld_error("mmap of bss failed: %s", xstrerror(errno)); 233 goto bad; 234 } 235 236 /* Unmap the gap between the text and data. */ 237 gap_addr = mapbase + round_up(text_vlimit - base_vaddr); 238 gap_size = data_addr - gap_addr; 239 if (gap_size != 0 && mprotect(gap_addr, gap_size, PROT_NONE) == -1) { 240 _rtld_error("mprotect of text -> data gap failed: %s", 241 xstrerror(errno)); 242 goto bad; 243 } 244 245 #ifdef RTLD_LOADER 246 /* Clear any BSS in the last page of the data segment. */ 247 clear_addr = mapbase + (clear_vaddr - base_vaddr); 248 if ((nclear = data_vlimit - clear_vaddr) > 0) 249 memset(clear_addr, 0, nclear); 250 251 /* Non-file portion of BSS mapped above. */ 252 #endif 253 254 obj->mapbase = mapbase; 255 obj->mapsize = mapsize; 256 obj->relocbase = mapbase - base_vaddr; 257 258 if (obj->dynamic) 259 obj->dynamic = (void *)(obj->relocbase + (Elf_Addr)obj->dynamic); 260 if (obj->entry) 261 obj->entry = (void *)(obj->relocbase + (Elf_Addr)obj->entry); 262 if (obj->interp) 263 obj->interp = (void *)(obj->relocbase + (Elf_Addr)obj->interp); 264 265 return obj; 266 267 bad: 268 if (ehdr != MAP_FAILED) 269 munmap(ehdr, _rtld_pagesz); 270 if (mapbase != MAP_FAILED) 271 munmap(mapbase, mapsize); 272 _rtld_obj_free(obj); 273 return NULL; 274 } 275 276 void 277 _rtld_obj_free(obj) 278 Obj_Entry *obj; 279 { 280 Objlist_Entry *elm; 281 282 free(obj->path); 283 while (obj->needed != NULL) { 284 Needed_Entry *needed = obj->needed; 285 obj->needed = needed->next; 286 free(needed); 287 } 288 while ((elm = SIMPLEQ_FIRST(&obj->dldags)) != NULL) { 289 SIMPLEQ_REMOVE_HEAD(&obj->dldags, link); 290 free(elm); 291 } 292 while ((elm = SIMPLEQ_FIRST(&obj->dagmembers)) != NULL) { 293 SIMPLEQ_REMOVE_HEAD(&obj->dagmembers, link); 294 free(elm); 295 } 296 free(obj); 297 } 298 299 Obj_Entry * 300 _rtld_obj_new(void) 301 { 302 Obj_Entry *obj; 303 304 obj = CNEW(Obj_Entry); 305 SIMPLEQ_INIT(&obj->dldags); 306 SIMPLEQ_INIT(&obj->dagmembers); 307 return obj; 308 } 309 310 /* 311 * Given a set of ELF protection flags, return the corresponding protection 312 * flags for MMAP. 313 */ 314 static int 315 protflags(elfflags) 316 int elfflags; 317 { 318 int prot = 0; 319 if (elfflags & PF_R) 320 prot |= PROT_READ; 321 #ifdef RTLD_LOADER 322 if (elfflags & PF_W) 323 prot |= PROT_WRITE; 324 #endif 325 if (elfflags & PF_X) 326 prot |= PROT_EXEC; 327 return prot; 328 } 329
Indexes created Sat Sep 27 14:09:57 GMT 2025