headers.c revision 1.14
1 /* $NetBSD: headers.c,v 1.14 2002/09/25 06:43:46 mycroft Exp $ */ 2 3 /* 4 * Copyright 1996 John D. Polstra. 5 * Copyright 1996 Matt Thomas <matt (at) 3am-software.com> 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by John Polstra. 19 * 4. The name of the author may not be used to endorse or promote products 20 * derived from this software without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 23 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 24 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 25 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 26 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 27 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 28 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 29 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 30 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 31 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 32 */ 33 34 /* 35 * Dynamic linker for ELF. 36 * 37 * John Polstra <jdp (at) polstra.com>. 38 */ 39 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 #include <sys/types.h> 49 #include <sys/mman.h> 50 #include <dirent.h> 51 52 #include "debug.h" 53 #include "rtld.h" 54 55 /* 56 * Process a shared object's DYNAMIC section, and save the important 57 * information in its Obj_Entry structure. 58 */ 59 void 60 _rtld_digest_dynamic(obj) 61 Obj_Entry *obj; 62 { 63 Elf_Dyn *dynp; 64 Needed_Entry **needed_tail = &obj->needed; 65 const Elf_Dyn *dyn_rpath = NULL; 66 Elf_Sword plttype = DT_REL; 67 Elf_Addr relsz = 0, relasz = 0; 68 Elf_Addr pltrel = 0, pltrelsz = 0; 69 Elf_Addr init = 0, fini = 0; 70 71 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; ++dynp) { 72 switch (dynp->d_tag) { 73 74 case DT_REL: 75 obj->rel = (const Elf_Rel *) 76 (obj->relocbase + dynp->d_un.d_ptr); 77 break; 78 79 case DT_RELSZ: 80 relsz = dynp->d_un.d_val; 81 break; 82 83 case DT_RELENT: 84 assert(dynp->d_un.d_val == sizeof(Elf_Rel)); 85 break; 86 87 case DT_JMPREL: 88 pltrel = dynp->d_un.d_ptr; 89 break; 90 91 case DT_PLTRELSZ: 92 pltrelsz = dynp->d_un.d_val; 93 break; 94 95 case DT_RELA: 96 obj->rela = (const Elf_Rela *) 97 (obj->relocbase + dynp->d_un.d_ptr); 98 break; 99 100 case DT_RELASZ: 101 relasz = dynp->d_un.d_val; 102 break; 103 104 case DT_RELAENT: 105 assert(dynp->d_un.d_val == sizeof(Elf_Rela)); 106 break; 107 108 case DT_PLTREL: 109 plttype = dynp->d_un.d_val; 110 assert(plttype == DT_REL || plttype == DT_RELA); 111 break; 112 113 case DT_SYMTAB: 114 obj->symtab = (const Elf_Sym *) 115 (obj->relocbase + dynp->d_un.d_ptr); 116 break; 117 118 case DT_SYMENT: 119 assert(dynp->d_un.d_val == sizeof(Elf_Sym)); 120 break; 121 122 case DT_STRTAB: 123 obj->strtab = (const char *) 124 (obj->relocbase + dynp->d_un.d_ptr); 125 break; 126 127 case DT_STRSZ: 128 obj->strsize = dynp->d_un.d_val; 129 break; 130 131 case DT_HASH: 132 { 133 const Elf_Word *hashtab = (const Elf_Word *) 134 (obj->relocbase + dynp->d_un.d_ptr); 135 136 obj->nbuckets = hashtab[0]; 137 obj->nchains = hashtab[1]; 138 obj->buckets = hashtab + 2; 139 obj->chains = obj->buckets + obj->nbuckets; 140 } 141 break; 142 143 case DT_NEEDED: 144 assert(!obj->rtld); 145 { 146 Needed_Entry *nep = NEW(Needed_Entry); 147 148 nep->name = dynp->d_un.d_val; 149 nep->obj = NULL; 150 nep->next = NULL; 151 152 *needed_tail = nep; 153 needed_tail = &nep->next; 154 } 155 break; 156 157 case DT_PLTGOT: 158 obj->pltgot = (Elf_Addr *) 159 (obj->relocbase + dynp->d_un.d_ptr); 160 break; 161 162 case DT_TEXTREL: 163 obj->textrel = true; 164 break; 165 166 case DT_SYMBOLIC: 167 obj->symbolic = true; 168 break; 169 170 case DT_RPATH: 171 /* 172 * We have to wait until later to process this, because 173 * we might not have gotten the address of the string 174 * table yet. 175 */ 176 dyn_rpath = dynp; 177 break; 178 179 case DT_SONAME: 180 /* Not used by the dynamic linker. */ 181 break; 182 183 case DT_INIT: 184 init = dynp->d_un.d_ptr; 185 break; 186 187 case DT_FINI: 188 fini = dynp->d_un.d_ptr; 189 break; 190 191 case DT_DEBUG: 192 #ifdef RTLD_LOADER 193 dynp->d_un.d_ptr = (Elf_Addr)&_rtld_debug; 194 #endif 195 break; 196 197 #ifdef __mips__ 198 case DT_MIPS_LOCAL_GOTNO: 199 obj->local_gotno = dynp->d_un.d_val; 200 break; 201 202 case DT_MIPS_SYMTABNO: 203 obj->symtabno = dynp->d_un.d_val; 204 break; 205 206 case DT_MIPS_GOTSYM: 207 obj->gotsym = dynp->d_un.d_val; 208 break; 209 210 case DT_MIPS_RLD_MAP: 211 #ifdef RTLD_LOADER 212 *((Elf_Addr *)(dynp->d_un.d_ptr)) = (Elf_Addr) 213 &_rtld_debug; 214 #endif 215 break; 216 #endif 217 } 218 } 219 220 obj->rellim = (const Elf_Rel *)((caddr_t)obj->rel + relsz); 221 obj->relalim = (const Elf_Rela *)((caddr_t)obj->rela + relasz); 222 if (plttype == DT_REL) { 223 obj->pltrel = (const Elf_Rel *)(obj->relocbase + pltrel); 224 obj->pltrellim = (const Elf_Rel *)(obj->relocbase + pltrel + pltrelsz); 225 obj->pltrelalim = 0; 226 /* On PPC and SPARC, at least, REL(A)SZ may include JMPREL. 227 Trim rel(a)lim to save time later. */ 228 if (obj->rellim && obj->pltrel && 229 obj->rellim > obj->pltrel && 230 obj->rellim <= obj->pltrellim) 231 obj->rellim = obj->pltrel; 232 } else { 233 obj->pltrela = (const Elf_Rela *)(obj->relocbase + pltrel); 234 obj->pltrellim = 0; 235 obj->pltrelalim = (const Elf_Rela *)(obj->relocbase + pltrel + pltrelsz); 236 /* On PPC and SPARC, at least, REL(A)SZ may include JMPREL. 237 Trim rel(a)lim to save time later. */ 238 if (obj->relalim && obj->pltrela && 239 obj->relalim > obj->pltrela && 240 obj->relalim <= obj->pltrelalim) 241 obj->relalim = obj->pltrela; 242 } 243 244 #if defined(RTLD_LOADER) && defined(__HAVE_FUNCTION_DESCRIPTORS) 245 if (init != 0) 246 obj->init = (void (*) __P((void))) 247 _rtld_function_descriptor_alloc(obj, NULL, init); 248 if (fini != 0) 249 obj->fini = (void (*) __P((void))) 250 _rtld_function_descriptor_alloc(obj, NULL, fini); 251 #else 252 if (init != 0) 253 obj->init = (void (*) __P((void))) 254 (obj->relocbase + init); 255 if (fini != 0) 256 obj->fini = (void (*) __P((void))) 257 (obj->relocbase + fini); 258 #endif 259 260 if (dyn_rpath != NULL) { 261 _rtld_add_paths(&obj->rpaths, obj->strtab + 262 dyn_rpath->d_un.d_val); 263 } 264 } 265 266 /* 267 * Process a shared object's program header. This is used only for the 268 * main program, when the kernel has already loaded the main program 269 * into memory before calling the dynamic linker. It creates and 270 * returns an Obj_Entry structure. 271 */ 272 Obj_Entry * 273 _rtld_digest_phdr(phdr, phnum, entry) 274 const Elf_Phdr *phdr; 275 int phnum; 276 caddr_t entry; 277 { 278 Obj_Entry *obj; 279 const Elf_Phdr *phlimit = phdr + phnum; 280 const Elf_Phdr *ph; 281 int nsegs = 0; 282 283 obj = _rtld_obj_new(); 284 for (ph = phdr; ph < phlimit; ++ph) { 285 switch (ph->p_type) { 286 287 case PT_PHDR: 288 assert((const Elf_Phdr *) ph->p_vaddr == phdr); 289 obj->phdr = (const Elf_Phdr *) ph->p_vaddr; 290 obj->phsize = ph->p_memsz; 291 break; 292 293 case PT_INTERP: 294 obj->interp = (const char *) ph->p_vaddr; 295 break; 296 297 case PT_LOAD: 298 assert(nsegs < 2); 299 if (nsegs == 0) { /* First load segment */ 300 obj->vaddrbase = round_down(ph->p_vaddr); 301 obj->mapbase = (caddr_t) obj->vaddrbase; 302 obj->relocbase = obj->mapbase - obj->vaddrbase; 303 obj->textsize = round_up(ph->p_vaddr + 304 ph->p_memsz) - obj->vaddrbase; 305 } else { /* Last load segment */ 306 obj->mapsize = round_up(ph->p_vaddr + 307 ph->p_memsz) - obj->vaddrbase; 308 } 309 ++nsegs; 310 break; 311 312 case PT_DYNAMIC: 313 obj->dynamic = (Elf_Dyn *) ph->p_vaddr; 314 break; 315 } 316 } 317 assert(nsegs == 2); 318 319 obj->entry = entry; 320 return obj; 321 } 322
Indexes created Wed Oct 15 14:09:57 GMT 2025