1/* $NetBSD: reloc.c,v 1.105 2011/12/02 09:06:49 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 1.105 2011/12/02 09:06:49 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 62static int _rtld_do_copy_relocation(const Obj_Entry *, const Elf_Rela *); 63 64static 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 srcsym = _rtld_symlook_obj(name, hash, srcobj, 0, 78 _rtld_fetch_ventry(dstobj, ELF_R_SYM(rela->r_info))); 79 if (srcsym != NULL) 80 break; 81 } 82 83 if (srcobj == NULL) { 84 _rtld_error("Undefined symbol \"%s\" referenced from COPY" 85 " relocation in %s", name, dstobj->path); 86 return (-1); 87 } 88 srcaddr = (const void *)(srcobj->relocbase + srcsym->st_value); 89 (void)memcpy(dstaddr, srcaddr, size); 90 rdbg(("COPY %s %s %s --> src=%p dst=%p size %ld", 91 dstobj->path, srcobj->path, name, srcaddr, 92 (void *)dstaddr, (long)size)); 93 return (0); 94} 95#endif /* RTLD_INHIBIT_COPY_RELOCS */ 96 97 98/* 99 * Process the special R_xxx_COPY relocations in the main program. These 100 * copy data from a shared object into a region in the main program's BSS 101 * segment. 102 * 103 * Returns 0 on success, -1 on failure. 104 */ 105int 106_rtld_do_copy_relocations(const Obj_Entry *dstobj) 107{ 108#ifndef RTLD_INHIBIT_COPY_RELOCS 109 110 /* COPY relocations are invalid elsewhere */ 111 assert(!dstobj->isdynamic); 112 113 if (dstobj->rel != NULL) { 114 const Elf_Rel *rel; 115 for (rel = dstobj->rel; rel < dstobj->rellim; ++rel) { 116 if (ELF_R_TYPE(rel->r_info) == R_TYPE(COPY)) { 117 Elf_Rela ourrela; 118 ourrela.r_info = rel->r_info; 119 ourrela.r_offset = rel->r_offset; 120 ourrela.r_addend = 0; 121 if (_rtld_do_copy_relocation(dstobj, 122 &ourrela) < 0) 123 return (-1); 124 } 125 } 126 } 127 if (dstobj->rela != NULL) { 128 const Elf_Rela *rela; 129 for (rela = dstobj->rela; rela < dstobj->relalim; ++rela) { 130 if (ELF_R_TYPE(rela->r_info) == R_TYPE(COPY)) { 131 if (_rtld_do_copy_relocation(dstobj, rela) < 0) 132 return (-1); 133 } 134 } 135 } 136#endif /* RTLD_INHIBIT_COPY_RELOCS */ 137 138 return (0); 139} 140 141/* 142 * Relocate newly-loaded shared objects. The argument is a pointer to 143 * the Obj_Entry for the first such object. All objects from the first 144 * to the end of the list of objects are relocated. Returns 0 on success, 145 * or -1 on failure. 146 */ 147int 148_rtld_relocate_objects(Obj_Entry *first, bool bind_now) 149{ 150 Obj_Entry *obj; 151 int ok = 1; 152 153 for (obj = first; obj != NULL; obj = obj->next) { 154 if (obj->nbuckets == 0 || obj->nchains == 0 || 155 obj->buckets == NULL || obj->symtab == NULL || 156 obj->strtab == NULL) { 157 _rtld_error("%s: Shared object has no run-time" 158 " symbol table", obj->path); 159 return -1; 160 } 161 if (obj->nbuckets == UINT32_MAX) { 162 _rtld_error("%s: Symbol table too large", obj->path); 163 return -1; 164 } 165 rdbg((" relocating %s (%ld/%ld rel/rela, %ld/%ld plt rel/rela)", 166 obj->path, 167 (long)(obj->rellim - obj->rel), 168 (long)(obj->relalim - obj->rela), 169 (long)(obj->pltrellim - obj->pltrel), 170 (long)(obj->pltrelalim - obj->pltrela))); 171 172 if (obj->textrel) { 173 /* 174 * There are relocations to the write-protected text 175 * segment. 176 */ 177 if (mprotect(obj->mapbase, obj->textsize, 178 PROT_READ | PROT_WRITE | PROT_EXEC) == -1) { 179 _rtld_error("%s: Cannot write-enable text " 180 "segment: %s", obj->path, xstrerror(errno)); 181 return -1; 182 } 183 } 184 dbg(("doing non-PLT relocations")); 185 if (_rtld_relocate_nonplt_objects(obj) < 0) 186 ok = 0; 187 if (obj->textrel) { /* Re-protected the text segment. */ 188 if (mprotect(obj->mapbase, obj->textsize, 189 PROT_READ | PROT_EXEC) == -1) { 190 _rtld_error("%s: Cannot write-protect text " 191 "segment: %s", obj->path, xstrerror(errno)); 192 return -1; 193 } 194 } 195 dbg(("doing lazy PLT binding")); 196 if (_rtld_relocate_plt_lazy(obj) < 0) 197 ok = 0; 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 /* 211 * Fill in the backwards compatibility dynamic linker entry points. 212 * 213 * DO NOT ADD TO THIS LIST 214 */ 215 obj->dlopen = dlopen; 216 obj->dlsym = dlsym; 217 obj->dlerror = dlerror; 218 obj->dlclose = dlclose; 219 obj->dladdr = dladdr; 220 221 dbg(("fixing up PLTGOT")); 222 /* Set the special PLTGOT entries. */ 223 if (obj->pltgot != NULL) 224 _rtld_setup_pltgot(obj); 225 } 226 227 return 0; 228} 229