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 37 #include <dlfcn.h> 38 #include <err.h> 39 #include <errno.h> 40 #include <fcntl.h> 41 #include <stdarg.h> 42 #include <stdio.h> 43 #include <stdlib.h> 44 #include <string.h> 45 #include <unistd.h> 46 47 #include "debug.h" 48 #include "rtld.h" 49 50 /* 51 * Process the special R_X86_64_COPY relocations in the main program. These 52 * copy data from a shared object into a region in the main program's BSS 53 * segment. 54 * 55 * Returns 0 on success, -1 on failure. 56 */ 57 int 58 do_copy_relocations(Obj_Entry *dstobj) 59 { 60 const Elf_Rela *relalim; 61 const Elf_Rela *rela; 62 63 assert(dstobj->mainprog); /* COPY relocations are invalid elsewhere */ 64 65 relalim = (const Elf_Rela *) ((caddr_t) dstobj->rela + dstobj->relasize); 66 for (rela = dstobj->rela; rela < relalim; rela++) { 67 if (ELF_R_TYPE(rela->r_info) == R_X86_64_COPY) { 68 void *dstaddr; 69 const Elf_Sym *dstsym; 70 const char *name; 71 unsigned long hash; 72 size_t size; 73 const void *srcaddr; 74 const Elf_Sym *srcsym; 75 Obj_Entry *srcobj; 76 77 dstaddr = (void *) (dstobj->relocbase + rela->r_offset); 78 dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info); 79 name = dstobj->strtab + dstsym->st_name; 80 hash = elf_hash(name); 81 size = dstsym->st_size; 82 83 for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next) 84 if ((srcsym = symlook_obj(name, hash, srcobj, false)) != NULL) 85 break; 86 87 if (srcobj == NULL) { 88 _rtld_error("Undefined symbol \"%s\" referenced from COPY" 89 " relocation in %s", name, dstobj->path); 90 return -1; 91 } 92 93 srcaddr = (const void *) (srcobj->relocbase + srcsym->st_value); 94 memcpy(dstaddr, srcaddr, size); 95 } 96 } 97 98 return 0; 99 } 100 101 /* Initialize the special GOT entries. */ 102 void 103 init_pltgot(Obj_Entry *obj) 104 { 105 if (obj->pltgot != NULL) { 106 obj->pltgot[1] = (Elf_Addr) obj; 107 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start; 108 } 109 } 110 111 /* Process the non-PLT relocations. */ 112 int 113 reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld) 114 { 115 const Elf_Rela *relalim; 116 const Elf_Rela *rela; 117 SymCache *cache; 118 int bytes = obj->nchains * sizeof(SymCache); 119 int r = -1; 120 121 /* 122 * The dynamic loader may be called from a thread, we have 123 * limited amounts of stack available so we cannot use alloca(). 124 */ 125 cache = mmap(NULL, bytes, PROT_READ|PROT_WRITE, MAP_ANON, -1, 0); 126 if (cache == MAP_FAILED) 127 cache = NULL; 128 129 relalim = (const Elf_Rela *) ((caddr_t) obj->rela + obj->relasize); 130 for (rela = obj->rela; rela < relalim; rela++) { 131 Elf_Addr *where = (Elf_Addr *) (obj->relocbase + rela->r_offset); 132 Elf32_Addr *where32 = (Elf32_Addr *)where; 133 134 switch (ELF_R_TYPE(rela->r_info)) { 135 136 case R_X86_64_NONE: 137 break; 138 139 case R_X86_64_64: 140 { 141 const Elf_Sym *def; 142 const Obj_Entry *defobj; 143 144 def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, 145 false, cache); 146 if (def == NULL) 147 goto done; 148 149 *where = (Elf_Addr) (defobj->relocbase + def->st_value + rela->r_addend); 150 } 151 break; 152 153 case R_X86_64_PC32: 154 /* 155 * I don't think the dynamic linker should ever see this 156 * type of relocation. But the binutils-2.6 tools sometimes 157 * generate it. 158 */ 159 { 160 const Elf_Sym *def; 161 const Obj_Entry *defobj; 162 163 def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, 164 false, cache); 165 if (def == NULL) 166 goto done; 167 168 *where32 = (Elf32_Addr) (unsigned long) (defobj->relocbase + 169 def->st_value + rela->r_addend - (Elf_Addr) where); 170 } 171 break; 172 /* missing: R_X86_64_GOT32 R_X86_64_PLT32 */ 173 174 case R_X86_64_COPY: 175 /* 176 * These are deferred until all other relocations have 177 * been done. All we do here is make sure that the COPY 178 * relocation is not in a shared library. They are allowed 179 * only in executable files. 180 */ 181 if (!obj->mainprog) { 182 _rtld_error("%s: Unexpected R_X86_64_COPY relocation" 183 " in shared library", obj->path); 184 goto done; 185 } 186 break; 187 188 case R_X86_64_GLOB_DAT: 189 { 190 const Elf_Sym *def; 191 const Obj_Entry *defobj; 192 193 def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, 194 false, cache); 195 if (def == NULL) 196 goto done; 197 198 *where = (Elf_Addr) (defobj->relocbase + def->st_value); 199 } 200 break; 201 202 case R_X86_64_RELATIVE: 203 *where = (Elf_Addr)(obj->relocbase + rela->r_addend); 204 break; 205 206 /* missing: R_X86_64_GOTPCREL, R_X86_64_32, R_X86_64_32S, R_X86_64_16, R_X86_64_PC16, R_X86_64_8, R_X86_64_PC8 */ 207 208 default: 209 _rtld_error("%s: Unsupported relocation type %d" 210 " in non-PLT relocations\n", obj->path, 211 ELF_R_TYPE(rela->r_info)); 212 goto done; 213 } 214 } 215 r = 0; 216 done: 217 if (cache) 218 munmap(cache, bytes); 219 return(r); 220 } 221 222 /* Process the PLT relocations. */ 223 int 224 reloc_plt(Obj_Entry *obj) 225 { 226 const Elf_Rela *relalim; 227 const Elf_Rela *rela; 228 229 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize); 230 for (rela = obj->pltrela; rela < relalim; rela++) { 231 Elf_Addr *where; 232 233 assert(ELF_R_TYPE(rela->r_info) == R_X86_64_JMP_SLOT); 234 235 /* Relocate the GOT slot pointing into the PLT. */ 236 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 237 *where += (Elf_Addr)obj->relocbase; 238 } 239 return 0; 240 } 241 242 /* Relocate the jump slots in an object. */ 243 int 244 reloc_jmpslots(Obj_Entry *obj) 245 { 246 const Elf_Rela *relalim; 247 const Elf_Rela *rela; 248 249 if (obj->jmpslots_done) 250 return 0; 251 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize); 252 for (rela = obj->pltrela; rela < relalim; rela++) { 253 Elf_Addr *where, target; 254 const Elf_Sym *def; 255 const Obj_Entry *defobj; 256 257 assert(ELF_R_TYPE(rela->r_info) == R_X86_64_JMP_SLOT); 258 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 259 def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, true, NULL); 260 if (def == NULL) 261 return -1; 262 target = (Elf_Addr)(defobj->relocbase + def->st_value + rela->r_addend); 263 reloc_jmpslot(where, target, defobj, obj, (const Elf_Rel *)rela); 264 } 265 obj->jmpslots_done = true; 266 return 0; 267 } 268