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 +
  45                                 file->shtab_ent_size * s);
  46
  47                 if(sect->type != 8)     /* NOBITS */
  48                         continue;
  49
  50                 r = sect->size;
  51
  52                 if (r < 1) {
  53                         DPRINT (DBG_ELF, "ELF .bss section is too small (%d bytes)", r);
  54                         continue;
  55                 }
  56
  57                 *elf_bss = (unsigned) sect->virt_adr;
  58
  59                 if (!*elf_bss) {
  60                         DPRINT (DBG_ELF, "Section .bss obtain wrong address: 0x%x", *elf_bss);
  61                         continue;
  62                 }
  63
  64                 /* clean memory for bss section */
  65                 memset (image+sect->offset, 0, sect->size);
  66
  67                 break;
  68         }
  69
  70         elf_sect_t *rodata = 0;
  71
  72         /* for each section... */
  73         for (s = 0; s < file->num_sects; s ++) {
  74                 sect = (elf_sect_t *)(image + file->shtab_offset + file->shtab_ent_size * s);
  75
  76                 if (sect->type == 1) {
  77                         if (sect->sect_name == 0x17 || sect->sect_name == 0x27) {
  78                                 rodata = sect;
  79                                 break;
  80                         }
  81                 }
  82
  83                 /* is it a relocation section?
  84                 xxx - we don't handle the extra addend for RELA relocations */
  85                 if(sect->type == 4)     /* RELA */
  86                         reloc_size = 12;
  87                 else if(sect->type == 9)/* REL */
  88                         reloc_size = 8;
  89                 else
  90                         continue;
  91         }
  92
  93         /* rodata section is not required */
  94         if (!rodata)
  95                 DPRINT (DBG_ELF, "rodata section does not exist");
  96
  97         /* find start of .text and make it the entry point */
  98         (*entry) = 0;
  99
 100         for (s = 0; s < file->num_sects; s ++) {
 101                 sect = (elf_sect_t *) (image + file->shtab_offset + file->shtab_ent_size * s);
 102
 103                 if (sect->sect_name != 0x0b && sect->sect_name != 0x1b)
 104                         continue;
 105
 106                 (*entry) = (unsigned) sect->virt_adr;
 107
 108                 break;
 109         }
 110
 111         /* copy rodata section to our memory area section */
 112         if (rodata) {
 113                 *elf_data = (unsigned) rodata->virt_adr;
 114                 *elf_data_off = (unsigned) rodata->offset;
 115         } else {
 116                 *elf_data = (unsigned) 0;
 117                 *elf_data_off = (unsigned) 0;
 118         }
 119
 120         if (!(*entry)) {
 121                 printf ("ELF -> Can't find section .text, so entry point is unknown\n");
 122                 return -1;
 123         }
 124
 125         return 0;
 126 }