1 /*- 2 * Copyright 1996, 1997, 1998, 1999 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 /* 29 * Dynamic linker for ELF. 30 * 31 * John Polstra <jdp@polstra.com>. 32 */ 33 34 #include <sys/param.h> 35 #include <sys/mman.h> 36 #include <machine/segments.h> 37 #include <machine/sysarch.h> 38 39 #include <dlfcn.h> 40 #include <err.h> 41 #include <errno.h> 42 #include <fcntl.h> 43 #include <stdarg.h> 44 #include <stdio.h> 45 #include <stdlib.h> 46 #include <string.h> 47 #include <unistd.h> 48 49 #include "debug.h" 50 #include "rtld.h" 51 52 /* 53 * Process the special R_386_COPY relocations in the main program. These 54 * copy data from a shared object into a region in the main program's BSS 55 * segment. 56 * 57 * Returns 0 on success, -1 on failure. 58 */ 59 int 60 do_copy_relocations(Obj_Entry *dstobj) 61 { 62 const Elf_Rel *rellim; 63 const Elf_Rel *rel; 64 65 assert(dstobj->mainprog); /* COPY relocations are invalid elsewhere */ 66 67 rellim = (const Elf_Rel *) ((caddr_t) dstobj->rel + dstobj->relsize); 68 for (rel = dstobj->rel; rel < rellim; rel++) { 69 if (ELF_R_TYPE(rel->r_info) == R_386_COPY) { 70 void *dstaddr; 71 const Elf_Sym *dstsym; 72 const char *name; 73 unsigned long hash; 74 size_t size; 75 const void *srcaddr; 76 const Elf_Sym *srcsym; 77 const Ver_Entry *ve; 78 Obj_Entry *srcobj; 79 80 dstaddr = (void *) (dstobj->relocbase + rel->r_offset); 81 dstsym = dstobj->symtab + ELF_R_SYM(rel->r_info); 82 name = dstobj->strtab + dstsym->st_name; 83 hash = elf_hash(name); 84 size = dstsym->st_size; 85 ve = fetch_ventry(dstobj, ELF_R_SYM(rel->r_info)); 86 87 for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next) 88 if ((srcsym = symlook_obj(name, hash, srcobj, ve, 0)) != NULL) 89 break; 90 91 if (srcobj == NULL) { 92 _rtld_error("Undefined symbol \"%s\" referenced from COPY" 93 " relocation in %s", name, dstobj->path); 94 return -1; 95 } 96 97 srcaddr = (const void *) (srcobj->relocbase + srcsym->st_value); 98 memcpy(dstaddr, srcaddr, size); 99 } 100 } 101 102 return 0; 103 } 104 105 /* Initialize the special GOT entries. */ 106 void 107 init_pltgot(Obj_Entry *obj) 108 { 109 if (obj->pltgot != NULL) { 110 obj->pltgot[1] = (Elf_Addr) obj; 111 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start; 112 } 113 } 114 115 /* Process the non-PLT relocations. */ 116 int 117 reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld) 118 { 119 const Elf_Rel *rellim; 120 const Elf_Rel *rel; 121 SymCache *cache; 122 int bytes = obj->nchains * sizeof(SymCache); 123 int r = -1; 124 125 /* 126 * The dynamic loader may be called from a thread, we have 127 * limited amounts of stack available so we cannot use alloca(). 128 */ 129 cache = mmap(NULL, bytes, PROT_READ|PROT_WRITE, MAP_ANON, -1, 0); 130 if (cache == MAP_FAILED) 131 cache = NULL; 132 133 rellim = (const Elf_Rel *) ((caddr_t) obj->rel + obj->relsize); 134 for (rel = obj->rel; rel < rellim; rel++) { 135 Elf_Addr *where = (Elf_Addr *) (obj->relocbase + rel->r_offset); 136 137 switch (ELF_R_TYPE(rel->r_info)) { 138 139 case R_386_NONE: 140 break; 141 142 case R_386_32: 143 { 144 const Elf_Sym *def; 145 const Obj_Entry *defobj; 146 147 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 148 false, cache); 149 if (def == NULL) 150 goto done; 151 152 *where += (Elf_Addr) (defobj->relocbase + def->st_value); 153 } 154 break; 155 156 case R_386_PC32: 157 /* 158 * I don't think the dynamic linker should ever see this 159 * type of relocation. But the binutils-2.6 tools sometimes 160 * generate it. 161 */ 162 { 163 const Elf_Sym *def; 164 const Obj_Entry *defobj; 165 166 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 167 false, cache); 168 if (def == NULL) 169 goto done; 170 171 *where += 172 (Elf_Addr) (defobj->relocbase + def->st_value) - 173 (Elf_Addr) where; 174 } 175 break; 176 177 case R_386_COPY: 178 /* 179 * These are deferred until all other relocations have 180 * been done. All we do here is make sure that the COPY 181 * relocation is not in a shared library. They are allowed 182 * only in executable files. 183 */ 184 if (!obj->mainprog) { 185 _rtld_error("%s: Unexpected R_386_COPY relocation" 186 " in shared library", obj->path); 187 goto done; 188 } 189 break; 190 191 case R_386_GLOB_DAT: 192 { 193 const Elf_Sym *def; 194 const Obj_Entry *defobj; 195 196 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 197 false, cache); 198 if (def == NULL) 199 goto done; 200 201 *where = (Elf_Addr) (defobj->relocbase + def->st_value); 202 } 203 break; 204 205 case R_386_RELATIVE: 206 *where += (Elf_Addr) obj->relocbase; 207 break; 208 209 case R_386_TLS_TPOFF: 210 { 211 const Elf_Sym *def; 212 const Obj_Entry *defobj; 213 214 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 215 false, cache); 216 if (def == NULL) 217 goto done; 218 219 /* 220 * We lazily allocate offsets for static TLS as we 221 * see the first relocation that references the 222 * TLS block. This allows us to support (small 223 * amounts of) static TLS in dynamically loaded 224 * modules. If we run out of space, we generate an 225 * error. 226 */ 227 if (!defobj->tls_done) { 228 if (!allocate_tls_offset((Obj_Entry*) defobj)) { 229 _rtld_error("%s: No space available for static " 230 "Thread Local Storage", obj->path); 231 goto done; 232 } 233 } 234 235 *where += (Elf_Addr) (def->st_value - defobj->tlsoffset); 236 } 237 break; 238 239 case R_386_TLS_DTPMOD32: 240 { 241 const Elf_Sym *def; 242 const Obj_Entry *defobj; 243 244 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 245 false, cache); 246 if (def == NULL) 247 goto done; 248 249 *where += (Elf_Addr) defobj->tlsindex; 250 } 251 break; 252 253 case R_386_TLS_DTPOFF32: 254 { 255 const Elf_Sym *def; 256 const Obj_Entry *defobj; 257 258 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 259 false, cache); 260 if (def == NULL) 261 goto done; 262 263 *where += (Elf_Addr) def->st_value; 264 } 265 break; 266 267 default: 268 _rtld_error("%s: Unsupported relocation type %d" 269 " in non-PLT relocations\n", obj->path, 270 ELF_R_TYPE(rel->r_info)); 271 goto done; 272 } 273 } 274 r = 0; 275 done: 276 if (cache) 277 munmap(cache, bytes); 278 return(r); 279 } 280 281 /* Process the PLT relocations. */ 282 int 283 reloc_plt(Obj_Entry *obj) 284 { 285 const Elf_Rel *rellim; 286 const Elf_Rel *rel; 287 288 rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize); 289 for (rel = obj->pltrel; rel < rellim; rel++) { 290 Elf_Addr *where; 291 292 assert(ELF_R_TYPE(rel->r_info) == R_386_JMP_SLOT); 293 294 /* Relocate the GOT slot pointing into the PLT. */ 295 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 296 *where += (Elf_Addr)obj->relocbase; 297 } 298 return 0; 299 } 300 301 /* Relocate the jump slots in an object. */ 302 int 303 reloc_jmpslots(Obj_Entry *obj) 304 { 305 const Elf_Rel *rellim; 306 const Elf_Rel *rel; 307 308 if (obj->jmpslots_done) 309 return 0; 310 rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize); 311 for (rel = obj->pltrel; rel < rellim; rel++) { 312 Elf_Addr *where, target; 313 const Elf_Sym *def; 314 const Obj_Entry *defobj; 315 316 assert(ELF_R_TYPE(rel->r_info) == R_386_JMP_SLOT); 317 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 318 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true, NULL); 319 if (def == NULL) 320 return -1; 321 target = (Elf_Addr)(defobj->relocbase + def->st_value); 322 reloc_jmpslot(where, target, defobj, obj, rel); 323 } 324 obj->jmpslots_done = true; 325 return 0; 326 } 327 328 void 329 allocate_initial_tls(Obj_Entry *objs) 330 { 331 void* tls; 332 333 /* 334 * Fix the size of the static TLS block by using the maximum 335 * offset allocated so far and adding a bit for dynamic modules to 336 * use. 337 */ 338 tls_static_space = tls_last_offset + RTLD_STATIC_TLS_EXTRA; 339 tls = allocate_tls(objs, NULL, 3*sizeof(Elf_Addr), sizeof(Elf_Addr)); 340 i386_set_gsbase(tls); 341 } 342 343 /* GNU ABI */ 344 __attribute__((__regparm__(1))) 345 void *___tls_get_addr(tls_index *ti) 346 { 347 Elf_Addr** segbase; 348 Elf_Addr* dtv; 349 350 __asm __volatile("movl %%gs:0, %0" : "=r" (segbase)); 351 dtv = segbase[1]; 352 353 return tls_get_addr_common(&segbase[1], ti->ti_module, ti->ti_offset); 354 } 355 356 /* Sun ABI */ 357 void *__tls_get_addr(tls_index *ti) 358 { 359 Elf_Addr** segbase; 360 Elf_Addr* dtv; 361 362 __asm __volatile("movl %%gs:0, %0" : "=r" (segbase)); 363 dtv = segbase[1]; 364 365 return tls_get_addr_common(&segbase[1], ti->ti_module, ti->ti_offset); 366 } 367