lib/libelf/elf_scn.c

   1 /*-
   2  * Copyright (c) 2006,2008-2010 Joseph Koshy
   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 AND CONTRIBUTORS ``AS IS'' AND
  15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  24  * SUCH DAMAGE.
  25  */
  26
  27 #include <sys/cdefs.h>
  28 #include <sys/queue.h>
  29
  30 #include <assert.h>
  31 #include <errno.h>
  32 #include <gelf.h>
  33 #include <libelf.h>
  34 #include <stddef.h>
  35 #include <stdlib.h>
  36
  37 #include "_libelf.h"
  38
  39 LIBELF_VCSID("$Id$");
  40
  41 /*
  42  * Load an ELF section table and create a list of Elf_Scn structures.
  43  */
  44 int
  45 _libelf_load_section_headers(Elf *e, void *ehdr)
  46 {
  47         int ec, swapbytes;
  48         size_t fsz, i, shnum;
  49         uint64_t shoff;
  50         char *src;
  51         Elf32_Ehdr *eh32;
  52         Elf64_Ehdr *eh64;
  53         Elf_Scn *scn;
  54         int (*xlator)(char *_d, size_t _dsz, char *_s, size_t _c, int _swap);
  55
  56         assert(e != NULL);
  57         assert(ehdr != NULL);
  58         assert((e->e_flags & LIBELF_F_SHDRS_LOADED) == 0);
  59
  60 #define CHECK_EHDR(E,EH)        do {                            \
  61                 if (fsz != (EH)->e_shentsize ||                 \
  62                     shoff + fsz * shnum > e->e_rawsize) {       \
  63                         LIBELF_SET_ERROR(HEADER, 0);            \
  64                         return (0);                             \
  65                 }                                               \
  66         } while (0)
  67
  68         ec = e->e_class;
  69         fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, (size_t) 1);
  70         assert(fsz > 0);
  71
  72         shnum = e->e_u.e_elf.e_nscn;
  73
  74         if (ec == ELFCLASS32) {
  75                 eh32 = (Elf32_Ehdr *) ehdr;
  76                 shoff = (uint64_t) eh32->e_shoff;
  77                 CHECK_EHDR(e, eh32);
  78         } else {
  79                 eh64 = (Elf64_Ehdr *) ehdr;
  80                 shoff = eh64->e_shoff;
  81                 CHECK_EHDR(e, eh64);
  82         }
  83
  84         xlator = _libelf_get_translator(ELF_T_SHDR, ELF_TOMEMORY, ec);
  85
  86         swapbytes = e->e_byteorder != LIBELF_PRIVATE(byteorder);
  87         src = e->e_rawfile + shoff;
  88
  89         /*
  90          * If the file is using extended numbering then section #0
  91          * would have already been read in.
  92          */
  93
  94         i = 0;
  95         if (!STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) {
  96                 assert(STAILQ_FIRST(&e->e_u.e_elf.e_scn) ==
  97                     STAILQ_LAST(&e->e_u.e_elf.e_scn, _Elf_Scn, s_next));
  98
  99                 i = 1;
 100                 src += fsz;
 101         }
 102
 103         for (; i < shnum; i++, src += fsz) {
 104                 if ((scn = _libelf_allocate_scn(e, i)) == NULL)
 105                         return (0);
 106
 107                 (*xlator)((char *) &scn->s_shdr, sizeof(scn->s_shdr), src,
 108                     (size_t) 1, swapbytes);
 109
 110                 if (ec == ELFCLASS32) {
 111                         scn->s_offset = scn->s_rawoff =
 112                             scn->s_shdr.s_shdr32.sh_offset;
 113                         scn->s_size = scn->s_shdr.s_shdr32.sh_size;
 114                 } else {
 115                         scn->s_offset = scn->s_rawoff =
 116                             scn->s_shdr.s_shdr64.sh_offset;
 117                         scn->s_size = scn->s_shdr.s_shdr64.sh_size;
 118                 }
 119         }
 120
 121         e->e_flags |= LIBELF_F_SHDRS_LOADED;
 122
 123         return (1);
 124 }
 125
 126
 127 Elf_Scn *
 128 elf_getscn(Elf *e, size_t index)
 129 {
 130         int ec;
 131         void *ehdr;
 132         Elf_Scn *s;
 133
 134         if (e == NULL || e->e_kind != ELF_K_ELF ||
 135             ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64)) {
 136                 LIBELF_SET_ERROR(ARGUMENT, 0);
 137                 return (NULL);
 138         }
 139
 140         if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL)
 141                 return (NULL);
 142
 143         if (e->e_cmd != ELF_C_WRITE &&
 144             (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 &&
 145             _libelf_load_section_headers(e, ehdr) == 0)
 146                 return (NULL);
 147
 148         STAILQ_FOREACH(s, &e->e_u.e_elf.e_scn, s_next)
 149                 if (s->s_ndx == index)
 150                         return (s);
 151
 152         LIBELF_SET_ERROR(ARGUMENT, 0);
 153         return (NULL);
 154 }
 155
 156 size_t
 157 elf_ndxscn(Elf_Scn *s)
 158 {
 159         if (s == NULL) {
 160                 LIBELF_SET_ERROR(ARGUMENT, 0);
 161                 return (SHN_UNDEF);
 162         }
 163         return (s->s_ndx);
 164 }
 165
 166 Elf_Scn *
 167 elf_newscn(Elf *e)
 168 {
 169         int ec;
 170         void *ehdr;
 171         Elf_Scn *scn;
 172
 173         if (e == NULL || e->e_kind != ELF_K_ELF) {
 174                 LIBELF_SET_ERROR(ARGUMENT, 0);
 175                 return (NULL);
 176         }
 177
 178         if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) {
 179                 LIBELF_SET_ERROR(CLASS, 0);
 180                 return (NULL);
 181         }
 182
 183         if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL)
 184                 return (NULL);
 185
 186         /*
 187          * The application may be asking for a new section descriptor
 188          * on an ELF object opened with ELF_C_RDWR or ELF_C_READ.  We
 189          * need to bring in the existing section information before
 190          * appending a new one to the list.
 191          *
 192          * Per the ELF(3) API, an application is allowed to open a
 193          * file using ELF_C_READ, mess with its internal structure and
 194          * use elf_update(...,ELF_C_NULL) to compute its new layout.
 195          */
 196         if (e->e_cmd != ELF_C_WRITE &&
 197             (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 &&
 198             _libelf_load_section_headers(e, ehdr) == 0)
 199                 return (NULL);
 200
 201         if (STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) {
 202                 assert(e->e_u.e_elf.e_nscn == 0);
 203                 if ((scn = _libelf_allocate_scn(e, (size_t) SHN_UNDEF)) ==
 204                     NULL)
 205                         return (NULL);
 206                 e->e_u.e_elf.e_nscn++;
 207         }
 208
 209         assert(e->e_u.e_elf.e_nscn > 0);
 210
 211         if ((scn = _libelf_allocate_scn(e, e->e_u.e_elf.e_nscn)) == NULL)
 212                 return (NULL);
 213
 214         e->e_u.e_elf.e_nscn++;
 215
 216         (void) elf_flagscn(scn, ELF_C_SET, ELF_F_DIRTY);
 217
 218         return (scn);
 219 }
 220
 221 Elf_Scn *
 222 elf_nextscn(Elf *e, Elf_Scn *s)
 223 {
 224         if (e == NULL || (e->e_kind != ELF_K_ELF) ||
 225             (s && s->s_elf != e)) {
 226                 LIBELF_SET_ERROR(ARGUMENT, 0);
 227                 return (NULL);
 228         }
 229
 230         return (s == NULL ? elf_getscn(e, (size_t) 1) :
 231             STAILQ_NEXT(s, s_next));
 232 }