libexec/ld.elf_so/reloc.c

   1 /*      $NetBSD: reloc.c,v 1.106 2012/01/06 10:38:56 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 1.106 2012/01/06 10:38:56 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                 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  */
 105 int
 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  */
 147 int
 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 #ifndef __minix
 173                 if (obj->textrel) {
 174                         /*
 175                          * There are relocations to the write-protected text
 176                          * segment.
 177                          */
 178                         if (mprotect(obj->mapbase, obj->textsize,
 179                                 PROT_READ | PROT_WRITE | PROT_EXEC) == -1) {
 180                                 _rtld_error("%s: Cannot write-enable text "
 181                                     "segment: %s", obj->path, xstrerror(errno));
 182                                 return -1;
 183                         }
 184                 }
 185 #endif
 186
 187                 dbg(("doing non-PLT relocations"));
 188                 if (_rtld_relocate_nonplt_objects(obj) < 0)
 189                         ok = 0;
 190
 191 #ifndef __minix
 192                 if (obj->textrel) {     /* Re-protected the text segment. */
 193                         if (mprotect(obj->mapbase, obj->textsize,
 194                                      PROT_READ | PROT_EXEC) == -1) {
 195                                 _rtld_error("%s: Cannot write-protect text "
 196                                     "segment: %s", obj->path, xstrerror(errno));
 197                                 return -1;
 198                         }
 199                 }
 200 #endif
 201
 202                 dbg(("doing lazy PLT binding"));
 203                 if (_rtld_relocate_plt_lazy(obj) < 0)
 204                         ok = 0;
 205                 if (obj->z_now || bind_now) {
 206                         dbg(("doing immediate PLT binding"));
 207                         if (_rtld_relocate_plt_objects(obj) < 0)
 208                                 ok = 0;
 209                 }
 210                 if (!ok)
 211                         return -1;
 212
 213                 /* Set some sanity-checking numbers in the Obj_Entry. */
 214                 obj->magic = RTLD_MAGIC;
 215                 obj->version = RTLD_VERSION;
 216
 217                 /*
 218                  * Fill in the backwards compatibility dynamic linker entry points.
 219                  *
 220                  * DO NOT ADD TO THIS LIST
 221                  */
 222                 obj->dlopen = dlopen;
 223                 obj->dlsym = dlsym;
 224                 obj->dlerror = dlerror;
 225                 obj->dlclose = dlclose;
 226                 obj->dladdr = dladdr;
 227
 228                 dbg(("fixing up PLTGOT"));
 229                 /* Set the special PLTGOT entries. */
 230                 if (obj->pltgot != NULL)
 231                         _rtld_setup_pltgot(obj);
 232         }
 233
 234         return 0;
 235 }