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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.
*
*/
#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:
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;
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:
case R_ARM_JUMP24:
if (sym->st_shndx == SHN_ABS) { // Absolute symbols used in PC-relative instructions need to be relocated
// Extract the PC offset from the instruction
int32 pcOffset = *target;
pcOffset = (pcOffset & 0x00ffffff) << 2;
if (pcOffset & 0x02000000)
pcOffset -= 0x04000000;
// Shift by the segment offset
pcOffset -= Elf32_Addr(_segment);
// Check the relocated offset is valid for the instruction
if (pcOffset <= (int32)0xfe000000 ||
pcOffset >= (int32)0x02000000) {
warning("elfloader: R_ARM_CALL/R_ARM_JUMP24: Out of range relocation i=%d, target=%p, pcOffset=%d", i, target, pcOffset);
free(rel);
return false;
}
// Put the relocated offset back in the instruction
pcOffset >>= 2;
pcOffset &= 0x00ffffff;
*target &= (uint32)0xff000000;
*target |= (uint32)pcOffset;
debug(8, "elfloader: R_ARM_CALL/R_ARM_JUMP24: i=%d, origTarget=%x, target=%x", i, origTarget, *target);
}
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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