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 size_t size; 74 const void *srcaddr; 75 const Elf_Sym *srcsym; 76 const Obj_Entry *srcobj, *defobj; 77 SymLook req; 78 int res; 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 size = dstsym->st_size; 84 symlook_init(&req, name); 85 req.ventry = fetch_ventry(dstobj, ELF_R_SYM(rel->r_info)); 86 87 for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next) { 88 res = symlook_obj(&req, srcobj); 89 if (res == 0) { 90 srcsym = req.sym_out; 91 defobj = req.defobj_out; 92 break; 93 } 94 } 95 96 if (srcobj == NULL) { 97 _rtld_error("Undefined symbol \"%s\" referenced from COPY" 98 " relocation in %s", name, dstobj->path); 99 return -1; 100 } 101 102 srcaddr = (const void *) (defobj->relocbase + srcsym->st_value); 103 memcpy(dstaddr, srcaddr, size); 104 } 105 } 106 107 return 0; 108 } 109 110 /* Initialize the special GOT entries. */ 111 void 112 init_pltgot(Obj_Entry *obj) 113 { 114 if (obj->pltgot != NULL) { 115 obj->pltgot[1] = (Elf_Addr) obj; 116 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start; 117 } 118 } 119 120 /* Process the non-PLT relocations. */ 121 int 122 reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld, RtldLockState *lockstate) 123 { 124 const Elf_Rel *rellim; 125 const Elf_Rel *rel; 126 SymCache *cache; 127 int r = -1; 128 129 /* 130 * The dynamic loader may be called from a thread, we have 131 * limited amounts of stack available so we cannot use alloca(). 132 */ 133 if (obj != obj_rtld) { 134 cache = calloc(obj->nchains, sizeof(SymCache)); 135 /* No need to check for NULL here */ 136 } else 137 cache = NULL; 138 139 rellim = (const Elf_Rel *) ((caddr_t) obj->rel + obj->relsize); 140 for (rel = obj->rel; rel < rellim; rel++) { 141 Elf_Addr *where = (Elf_Addr *) (obj->relocbase + rel->r_offset); 142 143 switch (ELF_R_TYPE(rel->r_info)) { 144 145 case R_386_NONE: 146 break; 147 148 case R_386_32: 149 { 150 const Elf_Sym *def; 151 const Obj_Entry *defobj; 152 153 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 154 false, cache, lockstate); 155 if (def == NULL) 156 goto done; 157 158 *where += (Elf_Addr) (defobj->relocbase + def->st_value); 159 } 160 break; 161 162 case R_386_PC32: 163 /* 164 * I don't think the dynamic linker should ever see this 165 * type of relocation. But the binutils-2.6 tools sometimes 166 * generate it. 167 */ 168 { 169 const Elf_Sym *def; 170 const Obj_Entry *defobj; 171 172 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 173 false, cache, lockstate); 174 if (def == NULL) 175 goto done; 176 177 *where += 178 (Elf_Addr) (defobj->relocbase + def->st_value) - 179 (Elf_Addr) where; 180 } 181 break; 182 183 case R_386_COPY: 184 /* 185 * These are deferred until all other relocations have 186 * been done. All we do here is make sure that the COPY 187 * relocation is not in a shared library. They are allowed 188 * only in executable files. 189 */ 190 if (!obj->mainprog) { 191 _rtld_error("%s: Unexpected R_386_COPY relocation" 192 " in shared library", obj->path); 193 goto done; 194 } 195 break; 196 197 case R_386_GLOB_DAT: 198 { 199 const Elf_Sym *def; 200 const Obj_Entry *defobj; 201 202 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 203 false, cache, lockstate); 204 if (def == NULL) 205 goto done; 206 207 *where = (Elf_Addr) (defobj->relocbase + def->st_value); 208 } 209 break; 210 211 case R_386_RELATIVE: 212 *where += (Elf_Addr) obj->relocbase; 213 break; 214 215 case R_386_TLS_TPOFF: 216 case R_386_TLS_TPOFF32: 217 { 218 const Elf_Sym *def; 219 const Obj_Entry *defobj; 220 Elf_Addr add; 221 222 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 223 false, cache, lockstate); 224 if (def == NULL) 225 goto done; 226 227 /* 228 * We lazily allocate offsets for static TLS as we 229 * see the first relocation that references the 230 * TLS block. This allows us to support (small 231 * amounts of) static TLS in dynamically loaded 232 * modules. If we run out of space, we generate an 233 * error. 234 */ 235 if (!defobj->tls_done) { 236 if (!allocate_tls_offset((Obj_Entry*) defobj)) { 237 _rtld_error("%s: No space available for static " 238 "Thread Local Storage", obj->path); 239 goto done; 240 } 241 } 242 add = (Elf_Addr) (def->st_value - defobj->tlsoffset); 243 if (ELF_R_TYPE(rel->r_info) == R_386_TLS_TPOFF) 244 *where += add; 245 else 246 *where -= add; 247 } 248 break; 249 250 case R_386_TLS_DTPMOD32: 251 { 252 const Elf_Sym *def; 253 const Obj_Entry *defobj; 254 255 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 256 false, cache, lockstate); 257 if (def == NULL) 258 goto done; 259 260 *where += (Elf_Addr) defobj->tlsindex; 261 } 262 break; 263 264 case R_386_TLS_DTPOFF32: 265 { 266 const Elf_Sym *def; 267 const Obj_Entry *defobj; 268 269 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 270 false, cache, lockstate); 271 if (def == NULL) 272 goto done; 273 274 *where += (Elf_Addr) def->st_value; 275 } 276 break; 277 278 default: 279 _rtld_error("%s: Unsupported relocation type %d" 280 " in non-PLT relocations\n", obj->path, 281 ELF_R_TYPE(rel->r_info)); 282 goto done; 283 } 284 } 285 r = 0; 286 done: 287 if (cache != NULL) 288 free(cache); 289 return(r); 290 } 291 292 /* Process the PLT relocations. */ 293 int 294 reloc_plt(Obj_Entry *obj) 295 { 296 const Elf_Rel *rellim; 297 const Elf_Rel *rel; 298 299 rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize); 300 for (rel = obj->pltrel; rel < rellim; rel++) { 301 Elf_Addr *where; 302 303 assert(ELF_R_TYPE(rel->r_info) == R_386_JMP_SLOT); 304 305 /* Relocate the GOT slot pointing into the PLT. */ 306 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 307 *where += (Elf_Addr)obj->relocbase; 308 } 309 return 0; 310 } 311 312 /* Relocate the jump slots in an object. */ 313 int 314 reloc_jmpslots(Obj_Entry *obj, RtldLockState *lockstate) 315 { 316 const Elf_Rel *rellim; 317 const Elf_Rel *rel; 318 319 if (obj->jmpslots_done) 320 return 0; 321 rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize); 322 for (rel = obj->pltrel; rel < rellim; rel++) { 323 Elf_Addr *where, target; 324 const Elf_Sym *def; 325 const Obj_Entry *defobj; 326 327 assert(ELF_R_TYPE(rel->r_info) == R_386_JMP_SLOT); 328 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 329 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true, NULL, 330 lockstate); 331 if (def == NULL) 332 return -1; 333 target = (Elf_Addr)(defobj->relocbase + def->st_value); 334 reloc_jmpslot(where, target, defobj, obj, rel); 335 } 336 obj->jmpslots_done = true; 337 return 0; 338 } 339 340 void 341 allocate_initial_tls(Obj_Entry *objs) 342 { 343 void* tls; 344 345 /* 346 * Fix the size of the static TLS block by using the maximum 347 * offset allocated so far and adding a bit for dynamic modules to 348 * use. 349 */ 350 tls_static_space = tls_last_offset + RTLD_STATIC_TLS_EXTRA; 351 tls = allocate_tls(objs, NULL, 3*sizeof(Elf_Addr), sizeof(Elf_Addr)); 352 i386_set_gsbase(tls); 353 } 354 355 /* GNU ABI */ 356 __attribute__((__regparm__(1))) 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 } 367 368 /* Sun ABI */ 369 void *__tls_get_addr(tls_index *ti) 370 { 371 Elf_Addr** segbase; 372 Elf_Addr* dtv; 373 374 __asm __volatile("movl %%gs:0, %0" : "=r" (segbase)); 375 dtv = segbase[1]; 376 377 return tls_get_addr_common(&segbase[1], ti->ti_module, ti->ti_offset); 378 } 379