headers.c revision 1.25
1 /* $NetBSD: headers.c,v 1.25 2007/12/28 19:36:21 christos 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 1.25 2007/12/28 19:36:21 christos 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 <dirent.h> 57 58 #include "debug.h" 59 #include "rtld.h" 60 61 /* 62 * Process a shared object's DYNAMIC section, and save the important 63 * information in its Obj_Entry structure. 64 */ 65 void 66 _rtld_digest_dynamic(const char *execname, Obj_Entry *obj) 67 { 68 Elf_Dyn *dynp; 69 Needed_Entry **needed_tail = &obj->needed; 70 const Elf_Dyn *dyn_rpath = NULL; 71 Elf_Sword plttype = DT_NULL; 72 Elf_Addr relsz = 0, relasz = 0; 73 Elf_Addr pltrel = 0, pltrelsz = 0; 74 Elf_Addr init = 0, fini = 0; 75 76 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; ++dynp) { 77 switch (dynp->d_tag) { 78 79 case DT_REL: 80 obj->rel = (const Elf_Rel *) 81 (obj->relocbase + dynp->d_un.d_ptr); 82 break; 83 84 case DT_RELSZ: 85 relsz = dynp->d_un.d_val; 86 break; 87 88 case DT_RELENT: 89 assert(dynp->d_un.d_val == sizeof(Elf_Rel)); 90 break; 91 92 case DT_JMPREL: 93 pltrel = dynp->d_un.d_ptr; 94 break; 95 96 case DT_PLTRELSZ: 97 pltrelsz = dynp->d_un.d_val; 98 break; 99 100 case DT_RELA: 101 obj->rela = (const Elf_Rela *) 102 (obj->relocbase + dynp->d_un.d_ptr); 103 break; 104 105 case DT_RELASZ: 106 relasz = dynp->d_un.d_val; 107 break; 108 109 case DT_RELAENT: 110 assert(dynp->d_un.d_val == sizeof(Elf_Rela)); 111 break; 112 113 case DT_PLTREL: 114 plttype = dynp->d_un.d_val; 115 assert(plttype == DT_REL || plttype == DT_RELA); 116 break; 117 118 case DT_SYMTAB: 119 obj->symtab = (const Elf_Sym *) 120 (obj->relocbase + dynp->d_un.d_ptr); 121 break; 122 123 case DT_SYMENT: 124 assert(dynp->d_un.d_val == sizeof(Elf_Sym)); 125 break; 126 127 case DT_STRTAB: 128 obj->strtab = (const char *) 129 (obj->relocbase + dynp->d_un.d_ptr); 130 break; 131 132 case DT_STRSZ: 133 obj->strsize = dynp->d_un.d_val; 134 break; 135 136 case DT_HASH: 137 { 138 const Elf_Word *hashtab = (const Elf_Word *) 139 (obj->relocbase + dynp->d_un.d_ptr); 140 141 obj->nbuckets = hashtab[0]; 142 obj->nchains = hashtab[1]; 143 obj->buckets = hashtab + 2; 144 obj->chains = obj->buckets + obj->nbuckets; 145 } 146 break; 147 148 case DT_NEEDED: 149 { 150 Needed_Entry *nep = NEW(Needed_Entry); 151 152 nep->name = dynp->d_un.d_val; 153 nep->obj = NULL; 154 nep->next = NULL; 155 156 *needed_tail = nep; 157 needed_tail = &nep->next; 158 } 159 break; 160 161 case DT_PLTGOT: 162 obj->pltgot = (Elf_Addr *) 163 (obj->relocbase + dynp->d_un.d_ptr); 164 break; 165 166 case DT_TEXTREL: 167 obj->textrel = true; 168 break; 169 170 case DT_SYMBOLIC: 171 obj->symbolic = true; 172 break; 173 174 case DT_RPATH: 175 /* 176 * We have to wait until later to process this, because 177 * we might not have gotten the address of the string 178 * table yet. 179 */ 180 dyn_rpath = dynp; 181 break; 182 183 case DT_SONAME: 184 /* Not used by the dynamic linker. */ 185 break; 186 187 case DT_INIT: 188 init = dynp->d_un.d_ptr; 189 break; 190 191 case DT_FINI: 192 fini = dynp->d_un.d_ptr; 193 break; 194 195 /* 196 * Don't process DT_DEBUG on MIPS as the dynamic section 197 * is mapped read-only. DT_MIPS_RLD_MAP is used instead. 198 * XXX: n32/n64 may use DT_DEBUG, not sure yet. 199 */ 200 #ifndef __mips__ 201 case DT_DEBUG: 202 #ifdef RTLD_LOADER 203 dynp->d_un.d_ptr = (Elf_Addr)&_rtld_debug; 204 #endif 205 break; 206 #endif 207 208 #ifdef __mips__ 209 case DT_MIPS_LOCAL_GOTNO: 210 obj->local_gotno = dynp->d_un.d_val; 211 break; 212 213 case DT_MIPS_SYMTABNO: 214 obj->symtabno = dynp->d_un.d_val; 215 break; 216 217 case DT_MIPS_GOTSYM: 218 obj->gotsym = dynp->d_un.d_val; 219 break; 220 221 case DT_MIPS_RLD_MAP: 222 #ifdef RTLD_LOADER 223 *((Elf_Addr *)(dynp->d_un.d_ptr)) = (Elf_Addr) 224 &_rtld_debug; 225 #endif 226 break; 227 #endif 228 case DT_FLAGS_1: 229 obj->initfirst = 230 ((dynp->d_un.d_val & DF_1_INITFIRST) != 0); 231 break; 232 } 233 } 234 235 obj->rellim = (const Elf_Rel *)((caddr_t)obj->rel + relsz); 236 obj->relalim = (const Elf_Rela *)((caddr_t)obj->rela + relasz); 237 if (plttype == DT_REL) { 238 obj->pltrel = (const Elf_Rel *)(obj->relocbase + pltrel); 239 obj->pltrellim = (const Elf_Rel *)(obj->relocbase + pltrel + pltrelsz); 240 obj->pltrelalim = 0; 241 /* On PPC and SPARC, at least, REL(A)SZ may include JMPREL. 242 Trim rel(a)lim to save time later. */ 243 if (obj->rellim && obj->pltrel && 244 obj->rellim > obj->pltrel && 245 obj->rellim <= obj->pltrellim) 246 obj->rellim = obj->pltrel; 247 } else if (plttype == DT_RELA) { 248 obj->pltrela = (const Elf_Rela *)(obj->relocbase + pltrel); 249 obj->pltrellim = 0; 250 obj->pltrelalim = (const Elf_Rela *)(obj->relocbase + pltrel + pltrelsz); 251 /* On PPC and SPARC, at least, REL(A)SZ may include JMPREL. 252 Trim rel(a)lim to save time later. */ 253 if (obj->relalim && obj->pltrela && 254 obj->relalim > obj->pltrela && 255 obj->relalim <= obj->pltrelalim) 256 obj->relalim = obj->pltrela; 257 } 258 259 #if defined(RTLD_LOADER) && defined(__HAVE_FUNCTION_DESCRIPTORS) 260 if (init != 0) 261 obj->init = (void (*)(void)) 262 _rtld_function_descriptor_alloc(obj, NULL, init); 263 if (fini != 0) 264 obj->fini = (void (*)(void)) 265 _rtld_function_descriptor_alloc(obj, NULL, fini); 266 #else 267 if (init != 0) 268 obj->init = (void (*)(void)) 269 (obj->relocbase + init); 270 if (fini != 0) 271 obj->fini = (void (*)(void)) 272 (obj->relocbase + fini); 273 #endif 274 275 if (dyn_rpath != NULL) { 276 _rtld_add_paths(execname, &obj->rpaths, obj->strtab + 277 dyn_rpath->d_un.d_val); 278 } 279 } 280 281 /* 282 * Process a shared object's program header. This is used only for the 283 * main program, when the kernel has already loaded the main program 284 * into memory before calling the dynamic linker. It creates and 285 * returns an Obj_Entry structure. 286 */ 287 Obj_Entry * 288 _rtld_digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry) 289 { 290 Obj_Entry *obj; 291 const Elf_Phdr *phlimit = phdr + phnum; 292 const Elf_Phdr *ph; 293 int nsegs = 0; 294 ptrdiff_t relocoffs = 0; 295 Elf_Addr vaddr; 296 297 obj = _rtld_obj_new(); 298 for (ph = phdr; ph < phlimit; ++ph) { 299 vaddr = ph->p_vaddr + relocoffs; 300 dbg(("headers: relocoffs = %lx\n", (long)relocoffs)); 301 switch (ph->p_type) { 302 303 case PT_PHDR: 304 relocoffs = (char *)phdr - (char *)ph->p_vaddr; 305 break; 306 307 case PT_INTERP: 308 obj->interp = (const char *)vaddr; 309 break; 310 311 case PT_LOAD: 312 assert(nsegs < 2); 313 if (nsegs == 0) { /* First load segment */ 314 obj->vaddrbase = round_down(vaddr); 315 obj->mapbase = (caddr_t)obj->vaddrbase; 316 obj->relocbase = relocoffs; 317 obj->textsize = round_up(vaddr + ph->p_memsz) - 318 obj->vaddrbase; 319 } else { /* Last load segment */ 320 obj->mapsize = round_up(vaddr + ph->p_memsz) - 321 obj->vaddrbase; 322 } 323 ++nsegs; 324 break; 325 326 case PT_DYNAMIC: 327 obj->dynamic = (Elf_Dyn *)vaddr; 328 break; 329 } 330 } 331 assert(nsegs == 2); 332 333 obj->entry = entry; 334 return obj; 335 } 336
Indexes created Wed Oct 15 16:09:53 GMT 2025