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arm-loader.cpp

/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.

 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.

 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * $URL$
 * $Id$
 *
 */

#include "common/scummsys.h"

#if defined(DYNAMIC_MODULES) && defined(USE_ELF_LOADER) && defined(ARM_TARGET)

#include "backends/plugins/elf/arm-loader.h"

#include "common/debug.h"

bool ARMDLObject::relocate(Elf32_Off offset, Elf32_Word size, byte *relSegment) {
      Elf32_Rel *rel = 0; //relocation entry

      // Allocate memory for relocation table
      if (!(rel = (Elf32_Rel *)malloc(size))) {
            warning("elfloader: Out of memory.");
            return false;
      }

      // Read in our relocation table
      if (!_file->seek(offset, SEEK_SET) || _file->read(rel, size) != size) {
            warning("elfloader: Relocation table load failed.");
            free(rel);
            return false;
      }

      // Treat each relocation entry. Loop over all of them
      uint32 cnt = size / sizeof(*rel);

      debug(2, "elfloader: Loaded relocation table. %d entries. base address=%p", cnt, relSegment);

      int32 a = 0;
      uint32 relocation = 0;

      // Loop over relocation entries
      for (uint32 i = 0; i < cnt; i++) {
            // Get the symbol this relocation entry is referring to
            Elf32_Sym *sym = _symtab + (REL_INDEX(rel[i].r_info));

            // Get the target instruction in the code. TODO: repect _segmentVMA
            uint32 *target = (uint32 *)((byte *)relSegment + rel[i].r_offset);

            uint32 origTarget = *target;  //Save for debugging

            // Act differently based on the type of relocation
            switch (REL_TYPE(rel[i].r_info)) {
            case R_ARM_ABS32:
                  if (sym->st_shndx < SHN_LOPROC) {               // Only shift for plugin section.
                        a = *target;                                          // Get full 32 bits of addend
                        relocation = a + Elf32_Addr(_segment);    // Shift by main offset

                        *target = relocation;

                        debug(8, "elfloader: R_ARM_ABS32: i=%d, a=%x, origTarget=%x, target=%x", i, a, origTarget, *target);
                  }
                  break;

            case R_ARM_THM_CALL:
                  debug(8, "elfloader: R_ARM_THM_CALL: PC-relative jump, ld takes care of necessary relocation work for us.");
                  break;

            case R_ARM_CALL:
                  debug(8, "elfloader: R_ARM_CALL: PC-relative jump, ld takes care of necessary relocation work for us.");
                  break;

            case R_ARM_JUMP24:
                  debug(8, "elfloader: R_ARM_JUMP24: PC-relative jump, ld takes care of all relocation work for us.");
                  break;

            case R_ARM_V4BX:
                  debug(8, "elfloader: R_ARM_V4BX: No relocation calculation necessary.");
                  break;

            default:
                  warning("elfloader: Unknown relocation type %d.", REL_TYPE(rel[i].r_info));
                  free(rel);
                  return false;
            }
      }

      free(rel);
      return true;
}

bool ARMDLObject::relocateRels(Elf32_Ehdr *ehdr, Elf32_Shdr *shdr) {
      // Loop over sections, finding relocation sections
      for (uint32 i = 0; i < ehdr->e_shnum; i++) {
            Elf32_Shdr *curShdr = &(shdr[i]);

            if ((curShdr->sh_type == SHT_REL || curShdr->sh_type == SHT_RELA) &&          // Check for a relocation section
                        curShdr->sh_entsize == sizeof(Elf32_Rel) &&                 // Check for proper relocation size
                        int32(curShdr->sh_link) == _symtab_sect &&                  // Check that the sh_link connects to our symbol table
                        curShdr->sh_info < ehdr->e_shnum &&                         // Check that the relocated section exists
                        (shdr[curShdr->sh_info].sh_flags & SHF_ALLOC)) {      // Check if relocated section resides in memory

                  if (curShdr->sh_type == SHT_RELA) {
                        warning("elfloader: RELA entries not supported yet!");
                        return false;
                  }

                  if (!relocate(curShdr->sh_offset, curShdr->sh_size, _segment))
                        return false;
            }
      }

      return true;
}

#endif /* defined(DYNAMIC_MODULES) && defined(USE_ELF_LOADER) && defined(ARM_TARGET) */


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