1 /* $NetBSD: reloc.c,v 1.95 2006/03/04 08:58:46 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 1.95 2006/03/04 08:58:46 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 <dirent.h> 56 57 #include "debug.h" 58 #include "rtld.h" 59 60 #ifndef RTLD_INHIBIT_COPY_RELOCS 61 static int _rtld_do_copy_relocation(const Obj_Entry *, const Elf_Rela *); 62 63 static int 64 _rtld_do_copy_relocation(const Obj_Entry *dstobj, const Elf_Rela *rela) 65 { 66 void *dstaddr = (void *)(dstobj->relocbase + rela->r_offset); 67 const Elf_Sym *dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info); 68 const char *name = dstobj->strtab + dstsym->st_name; 69 unsigned long hash = _rtld_elf_hash(name); 70 size_t size = dstsym->st_size; 71 const void *srcaddr; 72 const Elf_Sym *srcsym = NULL; 73 Obj_Entry *srcobj; 74 75 for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next) 76 if ((srcsym = _rtld_symlook_obj(name, hash, srcobj, false)) != NULL) 77 break; 78 79 if (srcobj == NULL) { 80 _rtld_error("Undefined symbol \"%s\" referenced from COPY" 81 " relocation in %s", name, dstobj->path); 82 return (-1); 83 } 84 srcaddr = (const void *)(srcobj->relocbase + srcsym->st_value); 85 (void)memcpy(dstaddr, srcaddr, size); 86 rdbg(("COPY %s %s %s --> src=%p dst=%p size %ld", 87 dstobj->path, srcobj->path, name, (void *)srcaddr, 88 (void *)dstaddr, (long)size)); 89 return (0); 90 } 91 #endif /* RTLD_INHIBIT_COPY_RELOCS */ 92 93 94 /* 95 * Process the special R_xxx_COPY relocations in the main program. These 96 * copy data from a shared object into a region in the main program's BSS 97 * segment. 98 * 99 * Returns 0 on success, -1 on failure. 100 */ 101 int 102 _rtld_do_copy_relocations(const Obj_Entry *dstobj) 103 { 104 #ifndef RTLD_INHIBIT_COPY_RELOCS 105 106 /* COPY relocations are invalid elsewhere */ 107 assert(!dstobj->isdynamic); 108 109 if (dstobj->rel != NULL) { 110 const Elf_Rel *rel; 111 for (rel = dstobj->rel; rel < dstobj->rellim; ++rel) { 112 if (ELF_R_TYPE(rel->r_info) == R_TYPE(COPY)) { 113 Elf_Rela ourrela; 114 ourrela.r_info = rel->r_info; 115 ourrela.r_offset = rel->r_offset; 116 ourrela.r_addend = 0; 117 if (_rtld_do_copy_relocation(dstobj, 118 &ourrela) < 0) 119 return (-1); 120 } 121 } 122 } 123 if (dstobj->rela != NULL) { 124 const Elf_Rela *rela; 125 for (rela = dstobj->rela; rela < dstobj->relalim; ++rela) { 126 if (ELF_R_TYPE(rela->r_info) == R_TYPE(COPY)) { 127 if (_rtld_do_copy_relocation(dstobj, rela) < 0) 128 return (-1); 129 } 130 } 131 } 132 #endif /* RTLD_INHIBIT_COPY_RELOCS */ 133 134 return (0); 135 } 136 137 /* 138 * Relocate newly-loaded shared objects. The argument is a pointer to 139 * the Obj_Entry for the first such object. All objects from the first 140 * to the end of the list of objects are relocated. Returns 0 on success, 141 * or -1 on failure. 142 */ 143 int 144 _rtld_relocate_objects(Obj_Entry *first, bool bind_now) 145 { 146 Obj_Entry *obj; 147 int ok = 1; 148 149 for (obj = first; obj != NULL; obj = obj->next) { 150 if (obj->nbuckets == 0 || obj->nchains == 0 || 151 obj->buckets == NULL || obj->symtab == NULL || 152 obj->strtab == NULL) { 153 _rtld_error("%s: Shared object has no run-time" 154 " symbol table", obj->path); 155 return -1; 156 } 157 rdbg((" relocating %s (%ld/%ld rel/rela, %ld/%ld plt rel/rela)", 158 obj->path, 159 (long)(obj->rellim - obj->rel), 160 (long)(obj->relalim - obj->rela), 161 (long)(obj->pltrellim - obj->pltrel), 162 (long)(obj->pltrelalim - obj->pltrela))); 163 164 if (obj->textrel) { 165 /* 166 * There are relocations to the write-protected text 167 * segment. 168 */ 169 if (mprotect(obj->mapbase, obj->textsize, 170 PROT_READ | PROT_WRITE | PROT_EXEC) == -1) { 171 _rtld_error("%s: Cannot write-enable text " 172 "segment: %s", obj->path, xstrerror(errno)); 173 return -1; 174 } 175 } 176 dbg(("doing non-PLT relocations")); 177 if (_rtld_relocate_nonplt_objects(obj) < 0) 178 ok = 0; 179 if (obj->textrel) { /* Re-protected the text segment. */ 180 if (mprotect(obj->mapbase, obj->textsize, 181 PROT_READ | PROT_EXEC) == -1) { 182 _rtld_error("%s: Cannot write-protect text " 183 "segment: %s", obj->path, xstrerror(errno)); 184 return -1; 185 } 186 } 187 dbg(("doing lazy PLT binding")); 188 if (_rtld_relocate_plt_lazy(obj) < 0) 189 ok = 0; 190 #if defined(__hppa__) 191 bind_now = 1; 192 #endif 193 if (bind_now) { 194 dbg(("doing immediate PLT binding")); 195 if (_rtld_relocate_plt_objects(obj) < 0) 196 ok = 0; 197 } 198 if (!ok) 199 return -1; 200 201 202 /* Set some sanity-checking numbers in the Obj_Entry. */ 203 obj->magic = RTLD_MAGIC; 204 obj->version = RTLD_VERSION; 205 206 /* Fill in the dynamic linker entry points. */ 207 obj->dlopen = dlopen; 208 obj->dlsym = dlsym; 209 obj->dlerror = dlerror; 210 obj->dlclose = dlclose; 211 obj->dladdr = dladdr; 212 213 dbg(("fixing up PLTGOT")); 214 /* Set the special PLTGOT entries. */ 215 if (obj->pltgot != NULL) 216 _rtld_setup_pltgot(obj); 217 } 218 219 return 0; 220 } 221