arch/common/boot/grub2/kern/i386/dl.c

   1 /* dl-386.c - arch-dependent part of loadable module support */
   2 /*
   3  *  GRUB  --  GRand Unified Bootloader
   4  *  Copyright (C) 2002,2005,2007  Free Software Foundation, Inc.
   5  *
   6  *  GRUB is free software: you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation, either version 3 of the License, or
   9  *  (at your option) any later version.
  10  *
  11  *  GRUB is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License
  17  *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <grub/dl.h>
  21 #include <grub/elf.h>
  22 #include <grub/misc.h>
  23 #include <grub/err.h>
  24
  25 /* Check if EHDR is a valid ELF header.  */
  26 grub_err_t
  27 grub_arch_dl_check_header (void *ehdr)
  28 {
  29   Elf32_Ehdr *e = ehdr;
  30
  31   /* Check the magic numbers.  */
  32   if (e->e_ident[EI_CLASS] != ELFCLASS32
  33       || e->e_ident[EI_DATA] != ELFDATA2LSB
  34       || e->e_machine != EM_386)
  35     return grub_error (GRUB_ERR_BAD_OS, "invalid arch specific ELF magic");
  36
  37   return GRUB_ERR_NONE;
  38 }
  39
  40 /* Relocate symbols.  */
  41 grub_err_t
  42 grub_arch_dl_relocate_symbols (grub_dl_t mod, void *ehdr)
  43 {
  44   Elf32_Ehdr *e = ehdr;
  45   Elf32_Shdr *s;
  46   Elf32_Sym *symtab;
  47   Elf32_Word entsize;
  48   unsigned i;
  49
  50   /* Find a symbol table.  */
  51   for (i = 0, s = (Elf32_Shdr *) ((char *) e + e->e_shoff);
  52        i < e->e_shnum;
  53        i++, s = (Elf32_Shdr *) ((char *) s + e->e_shentsize))
  54     if (s->sh_type == SHT_SYMTAB)
  55       break;
  56
  57   if (i == e->e_shnum)
  58     return grub_error (GRUB_ERR_BAD_MODULE, "no symtab found");
  59
  60   symtab = (Elf32_Sym *) ((char *) e + s->sh_offset);
  61   entsize = s->sh_entsize;
  62
  63   for (i = 0, s = (Elf32_Shdr *) ((char *) e + e->e_shoff);
  64        i < e->e_shnum;
  65        i++, s = (Elf32_Shdr *) ((char *) s + e->e_shentsize))
  66     if (s->sh_type == SHT_REL)
  67       {
  68         grub_dl_segment_t seg;
  69
  70         /* Find the target segment.  */
  71         for (seg = mod->segment; seg; seg = seg->next)
  72           if (seg->section == s->sh_info)
  73             break;
  74
  75         if (seg)
  76           {
  77             Elf32_Rel *rel, *max;
  78
  79             for (rel = (Elf32_Rel *) ((char *) e + s->sh_offset),
  80                    max = rel + s->sh_size / s->sh_entsize;
  81                  rel < max;
  82                  rel++)
  83               {
  84                 Elf32_Word *addr;
  85                 Elf32_Sym *sym;
  86
  87                 if (seg->size < rel->r_offset)
  88                   return grub_error (GRUB_ERR_BAD_MODULE,
  89                                      "reloc offset is out of the segment");
  90
  91                 addr = (Elf32_Word *) ((char *) seg->addr + rel->r_offset);
  92                 sym = (Elf32_Sym *) ((char *) symtab
  93                                      + entsize * ELF32_R_SYM (rel->r_info));
  94
  95                 switch (ELF32_R_TYPE (rel->r_info))
  96                   {
  97                   case R_386_32:
  98                     *addr += sym->st_value;
  99                     break;
 100
 101                   case R_386_PC32:
 102                     *addr += (sym->st_value - (Elf32_Word) seg->addr
 103                               - rel->r_offset);
 104                     break;
 105                   }
 106               }
 107           }
 108       }
 109
 110   return GRUB_ERR_NONE;
 111 }