headers.c revision 1.20
1 /* $NetBSD: headers.c,v 1.20 2005/01/09 12:43:23 simonb 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 1.20 2005/01/09 12:43:23 simonb 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(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 } 229 } 230 231 obj->rellim = (const Elf_Rel *)((caddr_t)obj->rel + relsz); 232 obj->relalim = (const Elf_Rela *)((caddr_t)obj->rela + relasz); 233 if (plttype == DT_REL) { 234 obj->pltrel = (const Elf_Rel *)(obj->relocbase + pltrel); 235 obj->pltrellim = (const Elf_Rel *)(obj->relocbase + pltrel + pltrelsz); 236 obj->pltrelalim = 0; 237 /* On PPC and SPARC, at least, REL(A)SZ may include JMPREL. 238 Trim rel(a)lim to save time later. */ 239 if (obj->rellim && obj->pltrel && 240 obj->rellim > obj->pltrel && 241 obj->rellim <= obj->pltrellim) 242 obj->rellim = obj->pltrel; 243 } else if (plttype == DT_RELA) { 244 obj->pltrela = (const Elf_Rela *)(obj->relocbase + pltrel); 245 obj->pltrellim = 0; 246 obj->pltrelalim = (const Elf_Rela *)(obj->relocbase + pltrel + pltrelsz); 247 /* On PPC and SPARC, at least, REL(A)SZ may include JMPREL. 248 Trim rel(a)lim to save time later. */ 249 if (obj->relalim && obj->pltrela && 250 obj->relalim > obj->pltrela && 251 obj->relalim <= obj->pltrelalim) 252 obj->relalim = obj->pltrela; 253 } 254 255 #if defined(RTLD_LOADER) && defined(__HAVE_FUNCTION_DESCRIPTORS) 256 if (init != 0) 257 obj->init = (void (*)(void)) 258 _rtld_function_descriptor_alloc(obj, NULL, init); 259 if (fini != 0) 260 obj->fini = (void (*)(void)) 261 _rtld_function_descriptor_alloc(obj, NULL, fini); 262 #else 263 if (init != 0) 264 obj->init = (void (*)(void)) 265 (obj->relocbase + init); 266 if (fini != 0) 267 obj->fini = (void (*)(void)) 268 (obj->relocbase + fini); 269 #endif 270 271 if (dyn_rpath != NULL) { 272 _rtld_add_paths(&obj->rpaths, obj->strtab + 273 dyn_rpath->d_un.d_val); 274 } 275 } 276 277 /* 278 * Process a shared object's program header. This is used only for the 279 * main program, when the kernel has already loaded the main program 280 * into memory before calling the dynamic linker. It creates and 281 * returns an Obj_Entry structure. 282 */ 283 Obj_Entry * 284 _rtld_digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry) 285 { 286 Obj_Entry *obj; 287 const Elf_Phdr *phlimit = phdr + phnum; 288 const Elf_Phdr *ph; 289 int nsegs = 0; 290 291 obj = _rtld_obj_new(); 292 for (ph = phdr; ph < phlimit; ++ph) { 293 switch (ph->p_type) { 294 295 case PT_PHDR: 296 assert((const Elf_Phdr *) ph->p_vaddr == phdr); 297 break; 298 299 case PT_INTERP: 300 obj->interp = (const char *) ph->p_vaddr; 301 break; 302 303 case PT_LOAD: 304 assert(nsegs < 2); 305 if (nsegs == 0) { /* First load segment */ 306 obj->vaddrbase = round_down(ph->p_vaddr); 307 obj->mapbase = (caddr_t) obj->vaddrbase; 308 obj->relocbase = obj->mapbase - obj->vaddrbase; 309 obj->textsize = round_up(ph->p_vaddr + 310 ph->p_memsz) - obj->vaddrbase; 311 } else { /* Last load segment */ 312 obj->mapsize = round_up(ph->p_vaddr + 313 ph->p_memsz) - obj->vaddrbase; 314 } 315 ++nsegs; 316 break; 317 318 case PT_DYNAMIC: 319 obj->dynamic = (Elf_Dyn *) ph->p_vaddr; 320 break; 321 } 322 } 323 assert(nsegs == 2); 324 325 obj->entry = entry; 326 return obj; 327 } 328
Indexes created Wed Oct 15 16:09:53 GMT 2025