1 /*- 2 * Copyright 1996-1998 John D. Polstra. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 * 25 * $FreeBSD: src/libexec/rtld-elf/map_object.c,v 1.7.2.2 2002/12/28 19:49:41 dillon Exp $ 26 * $DragonFly: src/libexec/rtld-elf/map_object.c,v 1.6 2005/03/22 22:56:36 davidxu Exp $ 27 */ 28 29 #include <sys/param.h> 30 #include <sys/mman.h> 31 #include <sys/stat.h> 32 33 #include <errno.h> 34 #include <stddef.h> 35 #include <stdlib.h> 36 #include <string.h> 37 #include <unistd.h> 38 39 #include "rtld.h" 40 41 static Elf_Ehdr *get_elf_header (int, const char *); 42 static int convert_prot(int); /* Elf flags -> mmap protection */ 43 static int convert_flags(int); /* Elf flags -> mmap flags */ 44 45 /* 46 * Map a shared object into memory. The "fd" argument is a file descriptor, 47 * which must be open on the object and positioned at its beginning. 48 * The "path" argument is a pathname that is used only for error messages. 49 * 50 * The return value is a pointer to a newly-allocated Obj_Entry structure 51 * for the shared object. Returns NULL on failure. 52 */ 53 Obj_Entry * 54 map_object(int fd, const char *path, const struct stat *sb) 55 { 56 Obj_Entry *obj; 57 Elf_Ehdr *hdr; 58 int i; 59 Elf_Phdr *phdr; 60 Elf_Phdr *phlimit; 61 Elf_Phdr **segs; 62 int nsegs; 63 Elf_Phdr *phdyn; 64 Elf_Phdr *phphdr; 65 Elf_Phdr *phinterp; 66 Elf_Phdr *phtls; 67 caddr_t mapbase; 68 size_t mapsize; 69 Elf_Off base_offset; 70 Elf_Addr base_vaddr; 71 Elf_Addr base_vlimit; 72 caddr_t base_addr; 73 Elf_Off data_offset; 74 Elf_Addr data_vaddr; 75 Elf_Addr data_vlimit; 76 caddr_t data_addr; 77 int data_prot; 78 int data_flags; 79 Elf_Addr clear_vaddr; 80 caddr_t clear_addr; 81 caddr_t clear_page; 82 size_t nclear; 83 Elf_Addr bss_vaddr; 84 Elf_Addr bss_vlimit; 85 caddr_t bss_addr; 86 87 hdr = get_elf_header(fd, path); 88 if (hdr == NULL) 89 return NULL; 90 91 /* 92 * Scan the program header entries, and save key information. 93 * 94 * We rely on there being exactly two load segments, text and data, 95 * in that order. 96 */ 97 phdr = (Elf_Phdr *) ((char *)hdr + hdr->e_phoff); 98 phlimit = phdr + hdr->e_phnum; 99 nsegs = -1; 100 phdyn = phphdr = phinterp = phtls = NULL; 101 segs = alloca(sizeof(segs[0]) * hdr->e_phnum); 102 while (phdr < phlimit) { 103 switch (phdr->p_type) { 104 105 case PT_INTERP: 106 phinterp = phdr; 107 break; 108 109 case PT_LOAD: 110 segs[++nsegs] = phdr; 111 if (segs[nsegs]->p_align < PAGE_SIZE) { 112 _rtld_error("%s: PT_LOAD segment %d not page-aligned", 113 path, nsegs); 114 return NULL; 115 } 116 break; 117 118 case PT_PHDR: 119 phphdr = phdr; 120 break; 121 122 case PT_DYNAMIC: 123 phdyn = phdr; 124 break; 125 case PT_TLS: 126 phtls = phdr; 127 break; 128 } 129 130 ++phdr; 131 } 132 if (phdyn == NULL) { 133 _rtld_error("%s: object is not dynamically-linked", path); 134 return NULL; 135 } 136 137 if (nsegs < 0) { 138 _rtld_error("%s: too few PT_LOAD segments", path); 139 return NULL; 140 } 141 142 /* 143 * Map the entire address space of the object, to stake out our 144 * contiguous region, and to establish the base address for relocation. 145 */ 146 base_offset = trunc_page(segs[0]->p_offset); 147 base_vaddr = trunc_page(segs[0]->p_vaddr); 148 base_vlimit = round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz); 149 mapsize = base_vlimit - base_vaddr; 150 base_addr = hdr->e_type == ET_EXEC ? (caddr_t) base_vaddr : NULL; 151 152 mapbase = mmap(base_addr, mapsize, convert_prot(segs[0]->p_flags), 153 convert_flags(segs[0]->p_flags), fd, base_offset); 154 if (mapbase == (caddr_t) -1) { 155 _rtld_error("%s: mmap of entire address space failed: %s", 156 path, strerror(errno)); 157 return NULL; 158 } 159 if (base_addr != NULL && mapbase != base_addr) { 160 _rtld_error("%s: mmap returned wrong address: wanted %p, got %p", 161 path, base_addr, mapbase); 162 munmap(mapbase, mapsize); 163 return NULL; 164 } 165 166 for (i = 0; i <= nsegs; i++) { 167 /* Overlay the segment onto the proper region. */ 168 data_offset = trunc_page(segs[i]->p_offset); 169 data_vaddr = trunc_page(segs[i]->p_vaddr); 170 data_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_filesz); 171 data_addr = mapbase + (data_vaddr - base_vaddr); 172 data_prot = convert_prot(segs[i]->p_flags); 173 data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED; 174 /* Do not call mmap on the first segment - this is redundant */ 175 if (i && mmap(data_addr, data_vlimit - data_vaddr, data_prot, 176 data_flags, fd, data_offset) == (caddr_t) -1) { 177 _rtld_error("%s: mmap of data failed: %s", path, strerror(errno)); 178 return NULL; 179 } 180 181 /* Clear any BSS in the last page of the segment. */ 182 clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz; 183 clear_addr = mapbase + (clear_vaddr - base_vaddr); 184 clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr); 185 if ((nclear = data_vlimit - clear_vaddr) > 0) { 186 /* Make sure the end of the segment is writable */ 187 if ((data_prot & PROT_WRITE) == 0) { 188 if (mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE) < 0) { 189 _rtld_error("%s: mprotect failed: %s", path, 190 strerror(errno)); 191 return NULL; 192 } 193 } 194 195 memset(clear_addr, 0, nclear); 196 197 /* 198 * reset the data protection back, enable the segment to be 199 * coredumped since we modified it. 200 */ 201 if ((data_prot & PROT_WRITE) == 0) { 202 madvise(clear_page, PAGE_SIZE, MADV_CORE); 203 mprotect(clear_page, PAGE_SIZE, data_prot); 204 } 205 } 206 207 /* Overlay the BSS segment onto the proper region. */ 208 bss_vaddr = data_vlimit; 209 bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz); 210 bss_addr = mapbase + (bss_vaddr - base_vaddr); 211 if (bss_vlimit > bss_vaddr) { /* There is something to do */ 212 if (mmap(bss_addr, bss_vlimit - bss_vaddr, data_prot, 213 MAP_PRIVATE|MAP_FIXED|MAP_ANON, -1, 0) == (caddr_t) -1) { 214 _rtld_error("%s: mmap of bss failed: %s", path, 215 strerror(errno)); 216 return NULL; 217 } 218 } 219 } 220 221 obj = obj_new(); 222 if (sb != NULL) { 223 obj->dev = sb->st_dev; 224 obj->ino = sb->st_ino; 225 } 226 obj->mapbase = mapbase; 227 obj->mapsize = mapsize; 228 obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) - 229 base_vaddr; 230 obj->vaddrbase = base_vaddr; 231 obj->relocbase = mapbase - base_vaddr; 232 obj->dynamic = (const Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr); 233 if (hdr->e_entry != 0) 234 obj->entry = (caddr_t) (obj->relocbase + hdr->e_entry); 235 if (phphdr != NULL) { 236 obj->phdr = (const Elf_Phdr *) (obj->relocbase + phphdr->p_vaddr); 237 obj->phsize = phphdr->p_memsz; 238 } 239 if (phinterp != NULL) 240 obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr); 241 if (phtls != NULL) { 242 tls_dtv_generation++; 243 obj->tlsindex = ++tls_max_index; 244 obj->tlssize = phtls->p_memsz; 245 obj->tlsalign = phtls->p_align; 246 obj->tlsinitsize = phtls->p_filesz; 247 obj->tlsinit = mapbase + phtls->p_vaddr; 248 } 249 return obj; 250 } 251 252 static Elf_Ehdr * 253 get_elf_header (int fd, const char *path) 254 { 255 static union { 256 Elf_Ehdr hdr; 257 char buf[PAGE_SIZE]; 258 } u; 259 ssize_t nbytes; 260 261 if ((nbytes = read(fd, u.buf, PAGE_SIZE)) == -1) { 262 _rtld_error("%s: read error: %s", path, strerror(errno)); 263 return NULL; 264 } 265 266 /* Make sure the file is valid */ 267 if (nbytes < (ssize_t)sizeof(Elf_Ehdr) || !IS_ELF(u.hdr)) { 268 _rtld_error("%s: invalid file format", path); 269 return NULL; 270 } 271 if (u.hdr.e_ident[EI_CLASS] != ELF_TARG_CLASS 272 || u.hdr.e_ident[EI_DATA] != ELF_TARG_DATA) { 273 _rtld_error("%s: unsupported file layout", path); 274 return NULL; 275 } 276 if (u.hdr.e_ident[EI_VERSION] != EV_CURRENT 277 || u.hdr.e_version != EV_CURRENT) { 278 _rtld_error("%s: unsupported file version", path); 279 return NULL; 280 } 281 if (u.hdr.e_type != ET_EXEC && u.hdr.e_type != ET_DYN) { 282 _rtld_error("%s: unsupported file type", path); 283 return NULL; 284 } 285 if (u.hdr.e_machine != ELF_TARG_MACH) { 286 _rtld_error("%s: unsupported machine", path); 287 return NULL; 288 } 289 290 /* 291 * We rely on the program header being in the first page. This is 292 * not strictly required by the ABI specification, but it seems to 293 * always true in practice. And, it simplifies things considerably. 294 */ 295 if (u.hdr.e_phentsize != sizeof(Elf_Phdr)) { 296 _rtld_error( 297 "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path); 298 return NULL; 299 } 300 if (u.hdr.e_phoff + u.hdr.e_phnum * sizeof(Elf_Phdr) > (size_t)nbytes) { 301 _rtld_error("%s: program header too large", path); 302 return NULL; 303 } 304 305 return (&u.hdr); 306 } 307 308 void 309 obj_free(Obj_Entry *obj) 310 { 311 Objlist_Entry *elm; 312 313 if (obj->tls_done) { 314 free_tls_offset(obj); 315 } 316 free(obj->origin_path); 317 free(obj->path); 318 while (obj->needed != NULL) { 319 Needed_Entry *needed = obj->needed; 320 obj->needed = needed->next; 321 free(needed); 322 } 323 while (!STAILQ_EMPTY(&obj->dldags)) { 324 elm = STAILQ_FIRST(&obj->dldags); 325 STAILQ_REMOVE_HEAD(&obj->dldags, link); 326 free(elm); 327 } 328 while (!STAILQ_EMPTY(&obj->dagmembers)) { 329 elm = STAILQ_FIRST(&obj->dagmembers); 330 STAILQ_REMOVE_HEAD(&obj->dagmembers, link); 331 free(elm); 332 } 333 free(obj); 334 } 335 336 Obj_Entry * 337 obj_new(void) 338 { 339 Obj_Entry *obj; 340 341 obj = CNEW(Obj_Entry); 342 STAILQ_INIT(&obj->dldags); 343 STAILQ_INIT(&obj->dagmembers); 344 return obj; 345 } 346 347 /* 348 * Given a set of ELF protection flags, return the corresponding protection 349 * flags for MMAP. 350 */ 351 static int 352 convert_prot(int elfflags) 353 { 354 int prot = 0; 355 if (elfflags & PF_R) 356 prot |= PROT_READ; 357 if (elfflags & PF_W) 358 prot |= PROT_WRITE; 359 if (elfflags & PF_X) 360 prot |= PROT_EXEC; 361 return prot; 362 } 363 364 static int 365 convert_flags(int elfflags) 366 { 367 int flags = MAP_PRIVATE; /* All mappings are private */ 368 369 /* 370 * Readonly mappings are marked "MAP_NOCORE", because they can be 371 * reconstructed by a debugger. 372 */ 373 if (!(elfflags & PF_W)) 374 flags |= MAP_NOCORE; 375 return flags; 376 } 377