headers.c revision 1.33
1 /* $NetBSD: headers.c,v 1.33 2010/09/30 19:45:24 skrll 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 /* 36 * Dynamic linker for ELF. 37 * 38 * John Polstra <jdp (at) polstra.com>. 39 */ 40 41 #include <sys/cdefs.h> 42 #ifndef lint 43 __RCSID("$NetBSD: headers.c,v 1.33 2010/09/30 19:45:24 skrll Exp $"); 44 #endif /* not lint */ 45 46 #include <err.h> 47 #include <errno.h> 48 #include <fcntl.h> 49 #include <stdarg.h> 50 #include <stdio.h> 51 #include <stdlib.h> 52 #include <string.h> 53 #include <unistd.h> 54 #include <sys/types.h> 55 #include <sys/mman.h> 56 #include <sys/bitops.h> 57 #include <dirent.h> 58 59 #include "debug.h" 60 #include "rtld.h" 61 62 /* 63 * Process a shared object's DYNAMIC section, and save the important 64 * information in its Obj_Entry structure. 65 */ 66 void 67 _rtld_digest_dynamic(const char *execname, Obj_Entry *obj) 68 { 69 Elf_Dyn *dynp; 70 Needed_Entry **needed_tail = &obj->needed; 71 const Elf_Dyn *dyn_rpath = NULL; 72 bool use_pltrel = false; 73 bool use_pltrela = false; 74 Elf_Addr relsz = 0, relasz = 0; 75 Elf_Addr pltrel = 0, pltrelsz = 0; 76 Elf_Addr init = 0, fini = 0; 77 78 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; ++dynp) { 79 switch (dynp->d_tag) { 80 81 case DT_REL: 82 obj->rel = (const Elf_Rel *) 83 (obj->relocbase + dynp->d_un.d_ptr); 84 break; 85 86 case DT_RELSZ: 87 relsz = dynp->d_un.d_val; 88 break; 89 90 case DT_RELENT: 91 assert(dynp->d_un.d_val == sizeof(Elf_Rel)); 92 break; 93 94 case DT_JMPREL: 95 pltrel = dynp->d_un.d_ptr; 96 break; 97 98 case DT_PLTRELSZ: 99 pltrelsz = dynp->d_un.d_val; 100 break; 101 102 case DT_RELA: 103 obj->rela = (const Elf_Rela *) 104 (obj->relocbase + dynp->d_un.d_ptr); 105 break; 106 107 case DT_RELASZ: 108 relasz = dynp->d_un.d_val; 109 break; 110 111 case DT_RELAENT: 112 assert(dynp->d_un.d_val == sizeof(Elf_Rela)); 113 break; 114 115 case DT_PLTREL: 116 use_pltrel = dynp->d_un.d_val == DT_REL; 117 use_pltrela = dynp->d_un.d_val == DT_RELA; 118 assert(use_pltrel || use_pltrela); 119 break; 120 121 case DT_SYMTAB: 122 obj->symtab = (const Elf_Sym *) 123 (obj->relocbase + dynp->d_un.d_ptr); 124 break; 125 126 case DT_SYMENT: 127 assert(dynp->d_un.d_val == sizeof(Elf_Sym)); 128 break; 129 130 case DT_STRTAB: 131 obj->strtab = (const char *) 132 (obj->relocbase + dynp->d_un.d_ptr); 133 break; 134 135 case DT_STRSZ: 136 obj->strsize = dynp->d_un.d_val; 137 break; 138 139 case DT_HASH: 140 { 141 const Elf_Symindx *hashtab = (const Elf_Symindx *) 142 (obj->relocbase + dynp->d_un.d_ptr); 143 144 if (hashtab[0] > UINT32_MAX) 145 obj->nbuckets = UINT32_MAX; 146 else 147 obj->nbuckets = hashtab[0]; 148 obj->nchains = hashtab[1]; 149 obj->buckets = hashtab + 2; 150 obj->chains = obj->buckets + obj->nbuckets; 151 /* 152 * Should really be in _rtld_relocate_objects, 153 * but _rtld_symlook_obj might be used before. 154 */ 155 if (obj->nbuckets) { 156 fast_divide32_prepare(obj->nbuckets, 157 &obj->nbuckets_m, 158 &obj->nbuckets_s1, 159 &obj->nbuckets_s2); 160 } 161 } 162 break; 163 164 case DT_NEEDED: 165 { 166 Needed_Entry *nep = NEW(Needed_Entry); 167 168 nep->name = dynp->d_un.d_val; 169 nep->obj = NULL; 170 nep->next = NULL; 171 172 *needed_tail = nep; 173 needed_tail = &nep->next; 174 } 175 break; 176 177 case DT_PLTGOT: 178 obj->pltgot = (Elf_Addr *) 179 (obj->relocbase + dynp->d_un.d_ptr); 180 break; 181 182 case DT_TEXTREL: 183 obj->textrel = true; 184 break; 185 186 case DT_SYMBOLIC: 187 obj->symbolic = true; 188 break; 189 190 case DT_RPATH: 191 /* 192 * We have to wait until later to process this, because 193 * we might not have gotten the address of the string 194 * table yet. 195 */ 196 dyn_rpath = dynp; 197 break; 198 199 case DT_SONAME: 200 /* Not used by the dynamic linker. */ 201 break; 202 203 case DT_INIT: 204 init = dynp->d_un.d_ptr; 205 break; 206 207 case DT_FINI: 208 fini = dynp->d_un.d_ptr; 209 break; 210 211 /* 212 * Don't process DT_DEBUG on MIPS as the dynamic section 213 * is mapped read-only. DT_MIPS_RLD_MAP is used instead. 214 * XXX: n32/n64 may use DT_DEBUG, not sure yet. 215 */ 216 #ifndef __mips__ 217 case DT_DEBUG: 218 #ifdef RTLD_LOADER 219 dynp->d_un.d_ptr = (Elf_Addr)&_rtld_debug; 220 #endif 221 break; 222 #endif 223 224 #ifdef __mips__ 225 case DT_MIPS_LOCAL_GOTNO: 226 obj->local_gotno = dynp->d_un.d_val; 227 break; 228 229 case DT_MIPS_SYMTABNO: 230 obj->symtabno = dynp->d_un.d_val; 231 break; 232 233 case DT_MIPS_GOTSYM: 234 obj->gotsym = dynp->d_un.d_val; 235 break; 236 237 case DT_MIPS_RLD_MAP: 238 #ifdef RTLD_LOADER 239 *((Elf_Addr *)(dynp->d_un.d_ptr)) = (Elf_Addr) 240 &_rtld_debug; 241 #endif 242 break; 243 #endif 244 case DT_FLAGS_1: 245 obj->initfirst = 246 ((dynp->d_un.d_val & DF_1_INITFIRST) != 0); 247 break; 248 } 249 } 250 251 obj->rellim = (const Elf_Rel *)((const uint8_t *)obj->rel + relsz); 252 obj->relalim = (const Elf_Rela *)((const uint8_t *)obj->rela + relasz); 253 if (use_pltrel) { 254 obj->pltrel = (const Elf_Rel *)(obj->relocbase + pltrel); 255 obj->pltrellim = (const Elf_Rel *)(obj->relocbase + pltrel + pltrelsz); 256 obj->pltrelalim = 0; 257 /* On PPC and SPARC, at least, REL(A)SZ may include JMPREL. 258 Trim rel(a)lim to save time later. */ 259 if (obj->rellim && obj->pltrel && 260 obj->rellim > obj->pltrel && 261 obj->rellim <= obj->pltrellim) 262 obj->rellim = obj->pltrel; 263 } else if (use_pltrela) { 264 obj->pltrela = (const Elf_Rela *)(obj->relocbase + pltrel); 265 obj->pltrellim = 0; 266 obj->pltrelalim = (const Elf_Rela *)(obj->relocbase + pltrel + pltrelsz); 267 /* On PPC and SPARC, at least, REL(A)SZ may include JMPREL. 268 Trim rel(a)lim to save time later. */ 269 if (obj->relalim && obj->pltrela && 270 obj->relalim > obj->pltrela && 271 obj->relalim <= obj->pltrelalim) 272 obj->relalim = obj->pltrela; 273 } 274 275 #if defined(RTLD_LOADER) && defined(__HAVE_FUNCTION_DESCRIPTORS) 276 if (init != 0) 277 obj->init = (void (*)(void)) 278 _rtld_function_descriptor_alloc(obj, NULL, init); 279 if (fini != 0) 280 obj->fini = (void (*)(void)) 281 _rtld_function_descriptor_alloc(obj, NULL, fini); 282 #else 283 if (init != 0) 284 obj->init = (void (*)(void)) 285 (obj->relocbase + init); 286 if (fini != 0) 287 obj->fini = (void (*)(void)) 288 (obj->relocbase + fini); 289 #endif 290 291 if (dyn_rpath != NULL) { 292 _rtld_add_paths(execname, &obj->rpaths, obj->strtab + 293 dyn_rpath->d_un.d_val); 294 } 295 } 296 297 /* 298 * Process a shared object's program header. This is used only for the 299 * main program, when the kernel has already loaded the main program 300 * into memory before calling the dynamic linker. It creates and 301 * returns an Obj_Entry structure. 302 */ 303 Obj_Entry * 304 _rtld_digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry) 305 { 306 Obj_Entry *obj; 307 const Elf_Phdr *phlimit = phdr + phnum; 308 const Elf_Phdr *ph; 309 int nsegs = 0; 310 ptrdiff_t relocoffs = 0; 311 Elf_Addr vaddr; 312 313 obj = _rtld_obj_new(); 314 for (ph = phdr; ph < phlimit; ++ph) { 315 vaddr = ph->p_vaddr + relocoffs; 316 switch (ph->p_type) { 317 318 case PT_PHDR: 319 relocoffs = (uintptr_t)phdr - (uintptr_t)ph->p_vaddr; 320 dbg(("headers: phdr %p phsize %zu relocoffs %lx", obj->phdr, 321 obj->phsize, (long)relocoffs)); 322 break; 323 324 case PT_INTERP: 325 obj->interp = (const char *)(uintptr_t)vaddr; 326 break; 327 328 case PT_LOAD: 329 assert(nsegs < 2); 330 if (nsegs == 0) { /* First load segment */ 331 obj->vaddrbase = round_down(vaddr); 332 obj->mapbase = (caddr_t)(uintptr_t)obj->vaddrbase; 333 obj->relocbase = (void *)relocoffs; 334 obj->textsize = round_up(vaddr + ph->p_memsz) - 335 obj->vaddrbase; 336 } else { /* Last load segment */ 337 obj->mapsize = round_up(vaddr + ph->p_memsz) - 338 obj->vaddrbase; 339 } 340 ++nsegs; 341 break; 342 343 case PT_DYNAMIC: 344 obj->dynamic = (Elf_Dyn *)(uintptr_t)vaddr; 345 break; 346 } 347 } 348 assert(nsegs == 2); 349 350 obj->entry = entry; 351 return obj; 352 } 353
Indexes created Wed Oct 15 16:09:53 GMT 2025