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 * $FreeBSD$ 26 */ 27 28 #include <sys/param.h> 29 #include <sys/mman.h> 30 #include <sys/stat.h> 31 32 #include <errno.h> 33 #include <stddef.h> 34 #include <stdlib.h> 35 #include <string.h> 36 #include <unistd.h> 37 38 #include "debug.h" 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; 125 126 case PT_TLS: 127 phtls = phdr; 128 break; 129 } 130 131 ++phdr; 132 } 133 if (phdyn == NULL) { 134 _rtld_error("%s: object is not dynamically-linked", path); 135 return NULL; 136 } 137 138 if (nsegs < 0) { 139 _rtld_error("%s: too few PT_LOAD segments", path); 140 return NULL; 141 } 142 143 /* 144 * Map the entire address space of the object, to stake out our 145 * contiguous region, and to establish the base address for relocation. 146 */ 147 base_offset = trunc_page(segs[0]->p_offset); 148 base_vaddr = trunc_page(segs[0]->p_vaddr); 149 base_vlimit = round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz); 150 mapsize = base_vlimit - base_vaddr; 151 base_addr = hdr->e_type == ET_EXEC ? (caddr_t) base_vaddr : NULL; 152 153 mapbase = mmap(base_addr, mapsize, convert_prot(segs[0]->p_flags), 154 convert_flags(segs[0]->p_flags), fd, base_offset); 155 if (mapbase == (caddr_t) -1) { 156 _rtld_error("%s: mmap of entire address space failed: %s", 157 path, strerror(errno)); 158 return NULL; 159 } 160 if (base_addr != NULL && mapbase != base_addr) { 161 _rtld_error("%s: mmap returned wrong address: wanted %p, got %p", 162 path, base_addr, mapbase); 163 munmap(mapbase, mapsize); 164 return NULL; 165 } 166 167 for (i = 0; i <= nsegs; i++) { 168 /* Overlay the segment onto the proper region. */ 169 data_offset = trunc_page(segs[i]->p_offset); 170 data_vaddr = trunc_page(segs[i]->p_vaddr); 171 data_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_filesz); 172 data_addr = mapbase + (data_vaddr - base_vaddr); 173 data_prot = convert_prot(segs[i]->p_flags); 174 data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED; 175 /* Do not call mmap on the first segment - this is redundant */ 176 if (i && mmap(data_addr, data_vlimit - data_vaddr, data_prot, 177 data_flags, fd, data_offset) == (caddr_t) -1) { 178 _rtld_error("%s: mmap of data failed: %s", path, strerror(errno)); 179 return NULL; 180 } 181 182 /* Clear any BSS in the last page of the segment. */ 183 clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz; 184 clear_addr = mapbase + (clear_vaddr - base_vaddr); 185 clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr); 186 if ((nclear = data_vlimit - clear_vaddr) > 0) { 187 /* Make sure the end of the segment is writable */ 188 if ((data_prot & PROT_WRITE) == 0 && 189 -1 == mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) { 190 _rtld_error("%s: mprotect failed: %s", path, 191 strerror(errno)); 192 return NULL; 193 } 194 195 memset(clear_addr, 0, nclear); 196 197 /* Reset the data protection back */ 198 if ((data_prot & PROT_WRITE) == 0) 199 mprotect(clear_page, PAGE_SIZE, data_prot); 200 } 201 202 /* Overlay the BSS segment onto the proper region. */ 203 bss_vaddr = data_vlimit; 204 bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz); 205 bss_addr = mapbase + (bss_vaddr - base_vaddr); 206 if (bss_vlimit > bss_vaddr) { /* There is something to do */ 207 if (mmap(bss_addr, bss_vlimit - bss_vaddr, data_prot, 208 MAP_PRIVATE|MAP_FIXED|MAP_ANON, -1, 0) == (caddr_t) -1) { 209 _rtld_error("%s: mmap of bss failed: %s", path, 210 strerror(errno)); 211 return NULL; 212 } 213 } 214 } 215 216 obj = obj_new(); 217 if (sb != NULL) { 218 obj->dev = sb->st_dev; 219 obj->ino = sb->st_ino; 220 } 221 obj->mapbase = mapbase; 222 obj->mapsize = mapsize; 223 obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) - 224 base_vaddr; 225 obj->vaddrbase = base_vaddr; 226 obj->relocbase = mapbase - base_vaddr; 227 obj->dynamic = (const Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr); 228 if (hdr->e_entry != 0) 229 obj->entry = (caddr_t) (obj->relocbase + hdr->e_entry); 230 if (phphdr != NULL) { 231 obj->phdr = (const Elf_Phdr *) (obj->relocbase + phphdr->p_vaddr); 232 obj->phsize = phphdr->p_memsz; 233 } 234 if (phinterp != NULL) 235 obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr); 236 if (phtls != NULL) { 237 tls_dtv_generation++; 238 obj->tlsindex = ++tls_max_index; 239 obj->tlssize = phtls->p_memsz; 240 obj->tlsalign = phtls->p_align; 241 obj->tlsinitsize = phtls->p_filesz; 242 obj->tlsinit = mapbase + phtls->p_vaddr; 243 } 244 return obj; 245 } 246 247 static Elf_Ehdr * 248 get_elf_header (int fd, const char *path) 249 { 250 static union { 251 Elf_Ehdr hdr; 252 char buf[PAGE_SIZE]; 253 } u; 254 ssize_t nbytes; 255 256 if ((nbytes = read(fd, u.buf, PAGE_SIZE)) == -1) { 257 _rtld_error("%s: read error: %s", path, strerror(errno)); 258 return NULL; 259 } 260 261 /* Make sure the file is valid */ 262 if (nbytes < (ssize_t)sizeof(Elf_Ehdr) || !IS_ELF(u.hdr)) { 263 _rtld_error("%s: invalid file format", path); 264 return NULL; 265 } 266 if (u.hdr.e_ident[EI_CLASS] != ELF_TARG_CLASS 267 || u.hdr.e_ident[EI_DATA] != ELF_TARG_DATA) { 268 _rtld_error("%s: unsupported file layout", path); 269 return NULL; 270 } 271 if (u.hdr.e_ident[EI_VERSION] != EV_CURRENT 272 || u.hdr.e_version != EV_CURRENT) { 273 _rtld_error("%s: unsupported file version", path); 274 return NULL; 275 } 276 if (u.hdr.e_type != ET_EXEC && u.hdr.e_type != ET_DYN) { 277 _rtld_error("%s: unsupported file type", path); 278 return NULL; 279 } 280 if (u.hdr.e_machine != ELF_TARG_MACH) { 281 _rtld_error("%s: unsupported machine", path); 282 return NULL; 283 } 284 285 /* 286 * We rely on the program header being in the first page. This is 287 * not strictly required by the ABI specification, but it seems to 288 * always true in practice. And, it simplifies things considerably. 289 */ 290 if (u.hdr.e_phentsize != sizeof(Elf_Phdr)) { 291 _rtld_error( 292 "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path); 293 return NULL; 294 } 295 if (u.hdr.e_phoff + u.hdr.e_phnum * sizeof(Elf_Phdr) > (size_t)nbytes) { 296 _rtld_error("%s: program header too large", path); 297 return NULL; 298 } 299 300 return (&u.hdr); 301 } 302 303 void 304 obj_free(Obj_Entry *obj) 305 { 306 Objlist_Entry *elm; 307 308 free(obj->path); 309 while (obj->needed != NULL) { 310 Needed_Entry *needed = obj->needed; 311 obj->needed = needed->next; 312 free(needed); 313 } 314 while (!STAILQ_EMPTY(&obj->dldags)) { 315 elm = STAILQ_FIRST(&obj->dldags); 316 STAILQ_REMOVE_HEAD(&obj->dldags, link); 317 free(elm); 318 } 319 while (!STAILQ_EMPTY(&obj->dagmembers)) { 320 elm = STAILQ_FIRST(&obj->dagmembers); 321 STAILQ_REMOVE_HEAD(&obj->dagmembers, link); 322 free(elm); 323 } 324 free(obj->origin_path); 325 free(obj->priv); 326 free(obj); 327 } 328 329 Obj_Entry * 330 obj_new(void) 331 { 332 Obj_Entry *obj; 333 334 obj = CNEW(Obj_Entry); 335 STAILQ_INIT(&obj->dldags); 336 STAILQ_INIT(&obj->dagmembers); 337 return obj; 338 } 339 340 /* 341 * Given a set of ELF protection flags, return the corresponding protection 342 * flags for MMAP. 343 */ 344 static int 345 convert_prot(int elfflags) 346 { 347 int prot = 0; 348 if (elfflags & PF_R) 349 prot |= PROT_READ; 350 if (elfflags & PF_W) 351 prot |= PROT_WRITE; 352 if (elfflags & PF_X) 353 prot |= PROT_EXEC; 354 return prot; 355 } 356 357 static int 358 convert_flags(int elfflags) 359 { 360 int flags = MAP_PRIVATE; /* All mappings are private */ 361 362 /* 363 * Readonly mappings are marked "MAP_NOCORE", because they can be 364 * reconstructed by a debugger. 365 */ 366 if (!(elfflags & PF_W)) 367 flags |= MAP_NOCORE; 368 return flags; 369 } 370