ext/libelf/elf_scn.c

   1 /*-
   2  * Copyright (c) 2006 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
  28 #include <assert.h>
  29 #include <errno.h>
  30 #include <stddef.h>
  31 #include <stdlib.h>
  32
  33 #include "gelf.h"
  34 #include "libelf.h"
  35 #include "_libelf.h"
  36
  37 /*
  38  * Load an ELF section table and create a list of Elf_Scn structures.
  39  */
  40 static int
  41 _libelf_load_scn(Elf *e, void *ehdr)
  42 {
  43         int ec, swapbytes;
  44         size_t fsz, i, shnum;
  45         uint64_t shoff;
  46         char *src;
  47         Elf32_Ehdr *eh32;
  48         Elf64_Ehdr *eh64;
  49         Elf_Scn *scn;
  50         void (*xlator)(char *_d, char *_s, size_t _c, int _swap);
  51
  52         assert(e != NULL);
  53         assert(ehdr != NULL);
  54         assert((e->e_flags & LIBELF_F_SHDRS_LOADED) == 0);
  55
  56 #define CHECK_EHDR(E,EH)        do {                            \
  57                 if (fsz != (EH)->e_shentsize ||                 \
  58                     shoff + fsz * shnum > e->e_rawsize) {       \
  59                         LIBELF_SET_ERROR(HEADER, 0);            \
  60                         return (0);                             \
  61                 }                                               \
  62         } while (0)
  63
  64         ec = e->e_class;
  65         fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, (size_t) 1);
  66         assert(fsz > 0);
  67
  68         shnum = e->e_u.e_elf.e_nscn;
  69
  70         if (ec == ELFCLASS32) {
  71                 eh32 = (Elf32_Ehdr *) ehdr;
  72                 shoff = (uint64_t) eh32->e_shoff;
  73                 CHECK_EHDR(e, eh32);
  74         } else {
  75                 eh64 = (Elf64_Ehdr *) ehdr;
  76                 shoff = eh64->e_shoff;
  77                 CHECK_EHDR(e, eh64);
  78         }
  79
  80         xlator = _libelf_get_translator(ELF_T_SHDR, ELF_TOMEMORY, ec);
  81
  82         swapbytes = e->e_byteorder != LIBELF_PRIVATE(byteorder);
  83         src = e->e_rawfile + shoff;
  84
  85         /*
  86          * If the file is using extended numbering then section #0
  87          * would have already been read in.
  88          */
  89
  90         i = 0;
  91         if (!STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) {
  92                 assert(STAILQ_FIRST(&e->e_u.e_elf.e_scn) ==
  93                     STAILQ_LAST(&e->e_u.e_elf.e_scn, _Elf_Scn, s_next));
  94
  95                 i = 1;
  96                 src += fsz;
  97         }
  98
  99         for (; i < shnum; i++, src += fsz) {
 100                 if ((scn = _libelf_allocate_scn(e, i)) == NULL)
 101                         return (0);
 102
 103                 (*xlator)((char *) &scn->s_shdr, src, (size_t) 1, swapbytes);
 104
 105                 if (ec == ELFCLASS32) {
 106                         scn->s_offset = scn->s_rawoff =
 107                             scn->s_shdr.s_shdr32.sh_offset;
 108                         scn->s_size = scn->s_shdr.s_shdr32.sh_size;
 109                 } else {
 110                         scn->s_offset = scn->s_rawoff =
 111                             scn->s_shdr.s_shdr64.sh_offset;
 112                         scn->s_size = scn->s_shdr.s_shdr64.sh_size;
 113                 }
 114         }
 115
 116         e->e_flags |= LIBELF_F_SHDRS_LOADED;
 117
 118         return (1);
 119 }
 120
 121
 122 Elf_Scn *
 123 elf_getscn(Elf *e, size_t index)
 124 {
 125         int ec;
 126         void *ehdr;
 127         Elf_Scn *s;
 128
 129         if (e == NULL || e->e_kind != ELF_K_ELF ||
 130             ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64)) {
 131                 LIBELF_SET_ERROR(ARGUMENT, 0);
 132                 return (NULL);
 133         }
 134
 135         if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL)
 136                 return (NULL);
 137
 138         if (e->e_cmd != ELF_C_WRITE &&
 139             (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 &&
 140             _libelf_load_scn(e, ehdr) == 0)
 141                 return (NULL);
 142
 143         STAILQ_FOREACH(s, &e->e_u.e_elf.e_scn, s_next)
 144                 if (s->s_ndx == index)
 145                         return (s);
 146
 147         LIBELF_SET_ERROR(ARGUMENT, 0);
 148         return (NULL);
 149 }
 150
 151 size_t
 152 elf_ndxscn(Elf_Scn *s)
 153 {
 154         if (s == NULL) {
 155                 LIBELF_SET_ERROR(ARGUMENT, 0);
 156                 return (SHN_UNDEF);
 157         }
 158         return (s->s_ndx);
 159 }
 160
 161 Elf_Scn *
 162 elf_newscn(Elf *e)
 163 {
 164         int ec;
 165         void *ehdr;
 166         Elf_Scn *scn;
 167
 168         if (e == NULL || e->e_kind != ELF_K_ELF) {
 169                 LIBELF_SET_ERROR(ARGUMENT, 0);
 170                 return (NULL);
 171         }
 172
 173         if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) {
 174                 LIBELF_SET_ERROR(CLASS, 0);
 175                 return (NULL);
 176         }
 177
 178         if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL)
 179                 return (NULL);
 180
 181         /*
 182          * The application may be asking for a new section descriptor
 183          * on an ELF object opened with ELF_C_RDWR or ELF_C_READ.  We
 184          * need to bring in the existing section information before
 185          * appending a new one to the list.
 186          *
 187          * Per the ELF(3) API, an application is allowed to open a
 188          * file using ELF_C_READ, mess with its internal structure and
 189          * use elf_update(...,ELF_C_NULL) to compute its new layout.
 190          */
 191         if (e->e_cmd != ELF_C_WRITE &&
 192             (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 &&
 193             _libelf_load_scn(e, ehdr) == 0)
 194                 return (NULL);
 195
 196         if (STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) {
 197                 assert(e->e_u.e_elf.e_nscn == 0);
 198                 if ((scn = _libelf_allocate_scn(e, (size_t) SHN_UNDEF)) ==
 199                     NULL)
 200                         return (NULL);
 201                 e->e_u.e_elf.e_nscn++;
 202         }
 203
 204         assert(e->e_u.e_elf.e_nscn > 0);
 205
 206         if ((scn = _libelf_allocate_scn(e, e->e_u.e_elf.e_nscn)) == NULL)
 207                 return (NULL);
 208
 209         e->e_u.e_elf.e_nscn++;
 210
 211         (void) elf_flagscn(scn, ELF_C_SET, ELF_F_DIRTY);
 212
 213         return (scn);
 214 }
 215
 216 Elf_Scn *
 217 elf_nextscn(Elf *e, Elf_Scn *s)
 218 {
 219         if (e == NULL || (e->e_kind != ELF_K_ELF) ||
 220             (s && s->s_elf != e)) {
 221                 LIBELF_SET_ERROR(ARGUMENT, 0);
 222                 return (NULL);
 223         }
 224
 225         return (s == NULL ? elf_getscn(e, (size_t) 1) :
 226             STAILQ_NEXT(s, s_next));
 227 }