kernel/core/elf.c

   1 /*
   2  *  ZeX/OS
   3  *  Copyright (C) 2007  Tomas 'ZeXx86' Jedrzejek (zexx86@zexos.org)
   4  *  Copyright (C) 2008  Tomas 'ZeXx86' Jedrzejek (zexx86@zexos.org)
   5  *  Copyright (C) 2009  Tomas 'ZeXx86' Jedrzejek (zexx86@zexos.org)
   6  *  Copyright (C) 2010  Tomas 'ZeXx86' Jedrzejek (zexx86@zexos.org)
   7  *
   8  *  This program is free software: you can redistribute it and/or modify
   9  *  it under the terms of the GNU General Public License as published by
  10  *  the Free Software Foundation, either version 3 of the License, or
  11  *  (at your option) any later version.
  12  *
  13  *  This program is distributed in the hope that it will be useful,
  14  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  *  GNU General Public License for more details.
  17  *
  18  *  You should have received a copy of the GNU General Public License
  19  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  20  */
  21
  22
  23 #include <system.h>
  24 #include <string.h>
  25 #include <elf.h>
  26
  27 int exec_elf (unsigned char *image, unsigned *entry, unsigned *elf_data, unsigned *elf_data_off, unsigned *elf_bss)
  28 {
  29         unsigned s, r, reloc_size;
  30
  31         elf_reloc_t *reloc;
  32         elf_sect_t *sect;
  33         elf_file_t *file;
  34
  35         /* validate */
  36         file = (elf_file_t *) image;
  37
  38         if (!arch_elf_detect (file))
  39                 return -1;
  40
  41         /* find the BSS and allocate memory for it
  42                 This must be done BEFORE doing any relocations */
  43         for (s = 0; s < file->num_sects; s ++) {
  44                 sect = (elf_sect_t *) (image + file->shtab_offset + file->shtab_ent_size * s);
  45
  46                 if(sect->type != 8)     /* NOBITS */
  47                         continue;
  48
  49                 r = sect->size;
  50
  51                 if (r < 1) {
  52                         DPRINT (DBG_ELF, "ELF .bss section is too small (%d bytes)", r);
  53                         continue;
  54                 }
  55
  56                 *elf_bss = (unsigned) sect->virt_adr;
  57
  58                 if (!*elf_bss) {
  59                         DPRINT (DBG_ELF, "Section .bss obtain wrong address: 0x%x", *elf_bss);
  60                         continue;
  61                 }
  62
  63                 /* clean memory for bss section */
  64                 memset (image+sect->offset, 0, sect->size);
  65
  66                 break;
  67         }
  68
  69         elf_sect_t *rodata = 0;
  70
  71         /* for each section... */
  72         for (s = 0; s < file->num_sects; s ++) {
  73                 sect = (elf_sect_t *) (image + file->shtab_offset + file->shtab_ent_size * s);
  74
  75                 if (sect->type == 1) {
  76                         if (sect->sect_name == 0x17 || sect->sect_name == 0x27) {
  77                                 rodata = sect;
  78                                 break;
  79                         }
  80                 }
  81
  82                 /* is it a relocation section?
  83                 xxx - we don't handle the extra addend for RELA relocations */
  84                 if(sect->type == 4)     /* RELA */
  85                         reloc_size = 12;
  86                 else if(sect->type == 9)/* REL */
  87                         reloc_size = 8;
  88                 else
  89                         continue;
  90         }
  91
  92         /* rodata section is not required */
  93         if (!rodata)
  94                 DPRINT (DBG_ELF, "rodata section does not exist");
  95
  96         /* find start of .text and make it the entry point */
  97         (*entry) = 0;
  98
  99         for (s = 0; s < file->num_sects; s ++) {
 100                 sect = (elf_sect_t *) (image + file->shtab_offset + file->shtab_ent_size * s);
 101
 102                 if (sect->sect_name != 0x0b && sect->sect_name != 0x1b)
 103                         continue;
 104
 105                 (*entry) = (unsigned) sect->virt_adr;
 106
 107                 break;
 108         }
 109
 110         /* copy rodata section to our memory area section */
 111         if (rodata) {
 112                 *elf_data = (unsigned) rodata->virt_adr;
 113                 *elf_data_off = (unsigned) rodata->offset;
 114         } else {
 115                 *elf_data = (unsigned) 0;
 116                 *elf_data_off = (unsigned) 0;
 117         }
 118
 119         if (!(*entry)) {
 120                 printf ("ELF -> Can't find section .text, so entry point is unknown\n");
 121                 return -1;
 122         }
 123
 124         return 0;
 125 }