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/* 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 "backends/fs/ds/ds-fs.h"
#include "elf-loader.h"
#include "dsmain.h"
#define __DEBUG_PLUGINS__
#ifdef __DEBUG_PLUGINS__
#define DBG(x,...) consolePrintf(x, ## __VA_ARGS__)
#else
#define DBG(x,...)
#endif
#define seterror(x,...) consolePrintf(x, ## __VA_ARGS__)
/**
* Follow the instruction of a relocation section.
*
* @param DLFile SeekableReadStream of File
* @param offset Offset into the File
* @param size Size of relocation section
*
*/
bool DLObject::relocate(Common::SeekableReadStream* DLFile, unsigned long offset, unsigned long size, void *relSegment) {
Elf32_Rel *rel = NULL; //relocation entry
// Allocate memory for relocation table
if (!(rel = (Elf32_Rel *)malloc(size))) {
seterror("Out of memory.");
return false;
}
// Read in our relocation table
if (DLFile->seek(offset, SEEK_SET) < 0 ||
DLFile->read(rel, size) != (ssize_t)size) {
seterror("Relocation table load failed.");
free(rel);
return false;
}
// Treat each relocation entry. Loop over all of them
int cnt = size / sizeof(*rel);
DBG("Loaded relocation table. %d entries. base address=%p\n", cnt, relSegment);
int a = 0;
unsigned int relocation = 0;
// Loop over relocation entries
for (int i = 0; i < cnt; i++) {
// Get the symbol this relocation entry is referring to
Elf32_Sym *sym = (Elf32_Sym *)(_symtab) + (REL_INDEX(rel[i].r_info));
// Get the target instruction in the code
unsigned int *target = (unsigned int *)((char *)relSegment + rel[i].r_offset);
unsigned int 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;
DBG("R_ARM_ABS32: i=%d, a=%x, origTarget=%x, target=%x\n", i, a, origTarget, *target);
}
break;
case R_ARM_THM_CALL:
DBG("R_ARM_THM_CALL: PC-relative jump, ld takes care of necessary relocation work for us.\n");
break;
case R_ARM_CALL:
DBG("R_ARM_CALL: PC-relative jump, ld takes care of necessary relocation work for us.\n");
break;
case R_ARM_JUMP24:
DBG("R_ARM_JUMP24: PC-relative jump, ld takes care of all relocation work for us.\n");
break;
case R_ARM_TARGET1:
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;
DBG("R_ARM_TARGET1: i=%d, a=%x, origTarget=%x, target=%x\n", i, a, origTarget, *target);
DBG("Make sure --target1-abs is a flag to LD!\n");
}
break;
case R_ARM_V4BX:
DBG("R_ARM_V4BX: No relocation calculation necessary.\n");
break;
default:
seterror("Unknown relocation type %d.", REL_TYPE(rel[i].r_info));
free(rel);
return false;
}
}
free(rel);
return true;
}
bool DLObject::relocateRels(Common::SeekableReadStream* DLFile, Elf32_Ehdr *ehdr, Elf32_Shdr *shdr) {
// Loop over sections, finding relocation sections
for (int 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
(int)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) {
seterror("RELA entries not supported yet!\n");
return false;
}
if (!relocate(DLFile, curShdr->sh_offset, curShdr->sh_size, _segment)) {
return false;
}
}
}
return true;
}
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