ext/libelf/libelf_ehdr.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  * $FreeBSD: src/lib/libelf/libelf_ehdr.c,v 1.2 2006/12/25 02:22:22 jkoshy Exp $
  27  */
  28
  29 #include <assert.h>
  30 #include "gelf.h"
  31 #include "libelf.h"
  32 #include <stdlib.h>
  33
  34 #include "_libelf.h"
  35
  36 /*
  37  * Retrieve counts for sections, phdrs and the section string table index
  38  * from section header #0 of the ELF object.
  39  */
  40 static int
  41 _libelf_load_extended(Elf *e, int ec, uint64_t shoff, uint16_t phnum,
  42     uint16_t strndx)
  43 {
  44         Elf_Scn *scn;
  45         size_t fsz;
  46         void (*xlator)(char *_d, char *_s, size_t _c, int _swap);
  47         uint32_t shtype;
  48
  49         assert(STAILQ_EMPTY(&e->e_u.e_elf.e_scn));
  50
  51         fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, 1);
  52         assert(fsz > 0);
  53
  54         if (e->e_rawsize < shoff + fsz) { /* raw file too small */
  55                 LIBELF_SET_ERROR(HEADER, 0);
  56                 return (0);
  57         }
  58
  59         if ((scn = _libelf_allocate_scn(e, (size_t) 0)) == NULL)
  60                 return (0);
  61
  62         xlator = _libelf_get_translator(ELF_T_SHDR, ELF_TOMEMORY, ec);
  63         (*xlator)((char *) &scn->s_shdr, e->e_rawfile + shoff, (size_t) 1,
  64             e->e_byteorder != LIBELF_PRIVATE(byteorder));
  65
  66 #define GET_SHDR_MEMBER(M) ((ec == ELFCLASS32) ? scn->s_shdr.s_shdr32.M : \
  67                 scn->s_shdr.s_shdr64.M)
  68
  69         if ((shtype = GET_SHDR_MEMBER(sh_type)) != SHT_NULL) {
  70                 LIBELF_SET_ERROR(SECTION, 0);
  71                 return (0);
  72         }
  73
  74         e->e_u.e_elf.e_nscn = GET_SHDR_MEMBER(sh_size);
  75         e->e_u.e_elf.e_nphdr = (phnum != PN_XNUM) ? phnum :
  76             GET_SHDR_MEMBER(sh_info);
  77         e->e_u.e_elf.e_strndx = (strndx != SHN_XINDEX) ? strndx :
  78             GET_SHDR_MEMBER(sh_link);
  79 #undef  GET_SHDR_MEMBER
  80
  81         return (1);
  82 }
  83
  84 #define EHDR_INIT(E,SZ)  do {                                           \
  85                 Elf##SZ##_Ehdr *eh = (E);                               \
  86                 eh->e_ident[EI_MAG0] = ELFMAG0;                         \
  87                 eh->e_ident[EI_MAG1] = ELFMAG1;                         \
  88                 eh->e_ident[EI_MAG2] = ELFMAG2;                         \
  89                 eh->e_ident[EI_MAG3] = ELFMAG3;                         \
  90                 eh->e_ident[EI_CLASS] = ELFCLASS##SZ;                   \
  91                 eh->e_ident[EI_DATA]  = ELFDATANONE;                    \
  92                 eh->e_ident[EI_VERSION] = LIBELF_PRIVATE(version);      \
  93                 eh->e_machine = EM_NONE;                                \
  94                 eh->e_type    = ELF_K_NONE;                             \
  95                 eh->e_version = LIBELF_PRIVATE(version);                \
  96         } while (0)
  97
  98 void *
  99 _libelf_ehdr(Elf *e, int ec, int allocate)
 100 {
 101         void *ehdr;
 102         size_t fsz, msz;
 103         uint16_t phnum, shnum, strndx;
 104         uint64_t shoff;
 105         void (*xlator)(char *_d, char *_s, size_t _c, int _swap);
 106
 107         assert(ec == ELFCLASS32 || ec == ELFCLASS64);
 108
 109         if (e == NULL || e->e_kind != ELF_K_ELF) {
 110                 LIBELF_SET_ERROR(ARGUMENT, 0);
 111                 return (NULL);
 112         }
 113
 114         if (e->e_class != ELFCLASSNONE && e->e_class != ec) {
 115                 LIBELF_SET_ERROR(CLASS, 0);
 116                 return (NULL);
 117         }
 118
 119         if (e->e_version != EV_CURRENT) {
 120                 LIBELF_SET_ERROR(VERSION, 0);
 121                 return (NULL);
 122         }
 123
 124         if (e->e_class == ELFCLASSNONE)
 125                 e->e_class = ec;
 126
 127         if (ec == ELFCLASS32)
 128                 ehdr = (void *) e->e_u.e_elf.e_ehdr.e_ehdr32;
 129         else
 130                 ehdr = (void *) e->e_u.e_elf.e_ehdr.e_ehdr64;
 131
 132         if (ehdr != NULL)       /* already have a translated ehdr */
 133                 return (ehdr);
 134
 135         fsz = _libelf_fsize(ELF_T_EHDR, ec, e->e_version, (size_t) 1);
 136         assert(fsz > 0);
 137
 138         if (e->e_cmd != ELF_C_WRITE && e->e_rawsize < fsz) {
 139                 LIBELF_SET_ERROR(HEADER, 0);
 140                 return (NULL);
 141         }
 142
 143         msz = _libelf_msize(ELF_T_EHDR, ec, EV_CURRENT);
 144
 145         assert(msz > 0);
 146
 147         if ((ehdr = calloc((size_t) 1, msz)) == NULL) {
 148                 LIBELF_SET_ERROR(RESOURCE, 0);
 149                 return (NULL);
 150         }
 151
 152         if (ec == ELFCLASS32) {
 153                 e->e_u.e_elf.e_ehdr.e_ehdr32 = ehdr;
 154                 EHDR_INIT(ehdr,32);
 155         } else {
 156                 e->e_u.e_elf.e_ehdr.e_ehdr64 = ehdr;
 157                 EHDR_INIT(ehdr,64);
 158         }
 159
 160         if (allocate)
 161                 e->e_flags |= ELF_F_DIRTY;
 162
 163         if (e->e_cmd == ELF_C_WRITE)
 164                 return (ehdr);
 165
 166         xlator = _libelf_get_translator(ELF_T_EHDR, ELF_TOMEMORY, ec);
 167         (*xlator)(ehdr, e->e_rawfile, (size_t) 1,
 168             e->e_byteorder != LIBELF_PRIVATE(byteorder));
 169
 170         /*
 171          * If extended numbering is being used, read the correct
 172          * number of sections and program header entries.
 173          */
 174         if (ec == ELFCLASS32) {
 175                 phnum = ((Elf32_Ehdr *) ehdr)->e_phnum;
 176                 shnum = ((Elf32_Ehdr *) ehdr)->e_shnum;
 177                 shoff = ((Elf32_Ehdr *) ehdr)->e_shoff;
 178                 strndx = ((Elf32_Ehdr *) ehdr)->e_shstrndx;
 179         } else {
 180                 phnum = ((Elf64_Ehdr *) ehdr)->e_phnum;
 181                 shnum = ((Elf64_Ehdr *) ehdr)->e_shnum;
 182                 shoff = ((Elf64_Ehdr *) ehdr)->e_shoff;
 183                 strndx = ((Elf64_Ehdr *) ehdr)->e_shstrndx;
 184         }
 185
 186         if (shnum >= SHN_LORESERVE ||
 187             (shoff == 0LL && (shnum != 0 || phnum == PN_XNUM ||
 188                 strndx == SHN_XINDEX))) {
 189                 LIBELF_SET_ERROR(HEADER, 0);
 190                 return (NULL);
 191         }
 192
 193         if (shnum != 0 || shoff == 0LL) { /* not using extended numbering */
 194                 e->e_u.e_elf.e_nphdr = phnum;
 195                 e->e_u.e_elf.e_nscn = shnum;
 196                 e->e_u.e_elf.e_strndx = strndx;
 197         } else if (_libelf_load_extended(e, ec, shoff, phnum, strndx) == 0)
 198                 return (NULL);
 199
 200         return (ehdr);
 201 }