1 /* $NetBSD: reloc.c,v 1.103 2010/12/24 12:41:43 skrll Exp $ */ 2 3 /* 4 * Copyright 1996 John D. Polstra. 5 * Copyright 1996 Matt Thomas <matt@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@polstra.com>. 38 */ 39 40 #include <sys/cdefs.h> 41 #ifndef lint 42 __RCSID("$NetBSD: reloc.c,v 1.103 2010/12/24 12:41:43 skrll Exp $"); 43 #endif /* not lint */ 44 45 #include <err.h> 46 #include <errno.h> 47 #include <fcntl.h> 48 #include <stdarg.h> 49 #include <stdio.h> 50 #include <stdlib.h> 51 #include <string.h> 52 #include <unistd.h> 53 #include <sys/types.h> 54 #include <sys/mman.h> 55 #include <sys/bitops.h> 56 #include <dirent.h> 57 58 #include "debug.h" 59 #include "rtld.h" 60 61 #ifndef RTLD_INHIBIT_COPY_RELOCS 62 static int _rtld_do_copy_relocation(const Obj_Entry *, const Elf_Rela *); 63 64 static int 65 _rtld_do_copy_relocation(const Obj_Entry *dstobj, const Elf_Rela *rela) 66 { 67 void *dstaddr = (void *)(dstobj->relocbase + rela->r_offset); 68 const Elf_Sym *dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info); 69 const char *name = dstobj->strtab + dstsym->st_name; 70 unsigned long hash = _rtld_elf_hash(name); 71 size_t size = dstsym->st_size; 72 const void *srcaddr; 73 const Elf_Sym *srcsym = NULL; 74 Obj_Entry *srcobj; 75 76 for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next) 77 if ((srcsym = _rtld_symlook_obj(name, hash, srcobj, false)) != NULL) 78 break; 79 80 if (srcobj == NULL) { 81 _rtld_error("Undefined symbol \"%s\" referenced from COPY" 82 " relocation in %s", name, dstobj->path); 83 return (-1); 84 } 85 srcaddr = (const void *)(srcobj->relocbase + srcsym->st_value); 86 (void)memcpy(dstaddr, srcaddr, size); 87 rdbg(("COPY %s %s %s --> src=%p dst=%p size %ld", 88 dstobj->path, srcobj->path, name, srcaddr, 89 (void *)dstaddr, (long)size)); 90 return (0); 91 } 92 #endif /* RTLD_INHIBIT_COPY_RELOCS */ 93 94 95 /* 96 * Process the special R_xxx_COPY relocations in the main program. These 97 * copy data from a shared object into a region in the main program's BSS 98 * segment. 99 * 100 * Returns 0 on success, -1 on failure. 101 */ 102 int 103 _rtld_do_copy_relocations(const Obj_Entry *dstobj) 104 { 105 #ifndef RTLD_INHIBIT_COPY_RELOCS 106 107 /* COPY relocations are invalid elsewhere */ 108 assert(!dstobj->isdynamic); 109 110 if (dstobj->rel != NULL) { 111 const Elf_Rel *rel; 112 for (rel = dstobj->rel; rel < dstobj->rellim; ++rel) { 113 if (ELF_R_TYPE(rel->r_info) == R_TYPE(COPY)) { 114 Elf_Rela ourrela; 115 ourrela.r_info = rel->r_info; 116 ourrela.r_offset = rel->r_offset; 117 ourrela.r_addend = 0; 118 if (_rtld_do_copy_relocation(dstobj, 119 &ourrela) < 0) 120 return (-1); 121 } 122 } 123 } 124 if (dstobj->rela != NULL) { 125 const Elf_Rela *rela; 126 for (rela = dstobj->rela; rela < dstobj->relalim; ++rela) { 127 if (ELF_R_TYPE(rela->r_info) == R_TYPE(COPY)) { 128 if (_rtld_do_copy_relocation(dstobj, rela) < 0) 129 return (-1); 130 } 131 } 132 } 133 #endif /* RTLD_INHIBIT_COPY_RELOCS */ 134 135 return (0); 136 } 137 138 /* 139 * Relocate newly-loaded shared objects. The argument is a pointer to 140 * the Obj_Entry for the first such object. All objects from the first 141 * to the end of the list of objects are relocated. Returns 0 on success, 142 * or -1 on failure. 143 */ 144 int 145 _rtld_relocate_objects(Obj_Entry *first, bool bind_now) 146 { 147 Obj_Entry *obj; 148 int ok = 1; 149 150 for (obj = first; obj != NULL; obj = obj->next) { 151 if (obj->nbuckets == 0 || obj->nchains == 0 || 152 obj->buckets == NULL || obj->symtab == NULL || 153 obj->strtab == NULL) { 154 _rtld_error("%s: Shared object has no run-time" 155 " symbol table", obj->path); 156 return -1; 157 } 158 if (obj->nbuckets == UINT32_MAX) { 159 _rtld_error("%s: Symbol table too large", obj->path); 160 return -1; 161 } 162 rdbg((" relocating %s (%ld/%ld rel/rela, %ld/%ld plt rel/rela)", 163 obj->path, 164 (long)(obj->rellim - obj->rel), 165 (long)(obj->relalim - obj->rela), 166 (long)(obj->pltrellim - obj->pltrel), 167 (long)(obj->pltrelalim - obj->pltrela))); 168 169 if (obj->textrel) { 170 /* 171 * There are relocations to the write-protected text 172 * segment. 173 */ 174 if (mprotect(obj->mapbase, obj->textsize, 175 PROT_READ | PROT_WRITE | PROT_EXEC) == -1) { 176 _rtld_error("%s: Cannot write-enable text " 177 "segment: %s", obj->path, xstrerror(errno)); 178 return -1; 179 } 180 } 181 dbg(("doing non-PLT relocations")); 182 if (_rtld_relocate_nonplt_objects(obj) < 0) 183 ok = 0; 184 if (obj->textrel) { /* Re-protected the text segment. */ 185 if (mprotect(obj->mapbase, obj->textsize, 186 PROT_READ | PROT_EXEC) == -1) { 187 _rtld_error("%s: Cannot write-protect text " 188 "segment: %s", obj->path, xstrerror(errno)); 189 return -1; 190 } 191 } 192 dbg(("doing lazy PLT binding")); 193 if (_rtld_relocate_plt_lazy(obj) < 0) 194 ok = 0; 195 #if defined(__hppa__) 196 bind_now = 1; 197 #endif 198 if (obj->z_now || bind_now) { 199 dbg(("doing immediate PLT binding")); 200 if (_rtld_relocate_plt_objects(obj) < 0) 201 ok = 0; 202 } 203 if (!ok) 204 return -1; 205 206 /* Set some sanity-checking numbers in the Obj_Entry. */ 207 obj->magic = RTLD_MAGIC; 208 obj->version = RTLD_VERSION; 209 210 /* Fill in the dynamic linker entry points. */ 211 obj->dlopen = dlopen; 212 obj->dlsym = dlsym; 213 obj->dlerror = dlerror; 214 obj->dlclose = dlclose; 215 obj->dladdr = dladdr; 216 217 dbg(("fixing up PLTGOT")); 218 /* Set the special PLTGOT entries. */ 219 if (obj->pltgot != NULL) 220 _rtld_setup_pltgot(obj); 221 } 222 223 return 0; 224 } 225