55db1210eb
Setting the base address for the plugin elf files high in memory forces the linker to generate veneers to turn relative jumps to the main binary into absolute jumps. This removes the need to allocate the plugins near the the main binary in the program address space. This also removes the need to handle the R_ARM_CALL and R_ARM_JUMP24 relocation types. Fixes #11555.
126 lines
4.2 KiB
C++
126 lines
4.2 KiB
C++
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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*/
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#include "common/scummsys.h"
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#if defined(DYNAMIC_MODULES) && defined(USE_ELF_LOADER) && defined(ARM_TARGET)
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#include "backends/plugins/elf/arm-loader.h"
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#include "common/debug.h"
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bool ARMDLObject::relocate(Elf32_Off offset, Elf32_Word size, byte *relSegment) {
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Elf32_Rel *rel = 0; //relocation entry
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// Allocate memory for relocation table
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if (!(rel = (Elf32_Rel *)malloc(size))) {
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warning("elfloader: Out of memory.");
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return false;
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}
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// Read in our relocation table
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if (!_file->seek(offset, SEEK_SET) || _file->read(rel, size) != size) {
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warning("elfloader: Relocation table load failed.");
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free(rel);
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return false;
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}
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// Treat each relocation entry. Loop over all of them
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uint32 cnt = size / sizeof(*rel);
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debug(2, "elfloader: Loaded relocation table. %d entries. base address=%p", cnt, relSegment);
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int32 a = 0;
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uint32 relocation = 0;
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// Loop over relocation entries
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for (uint32 i = 0; i < cnt; i++) {
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// Get the symbol this relocation entry is referring to
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Elf32_Sym *sym = _symtab + (REL_INDEX(rel[i].r_info));
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// Get the target instruction in the code.
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uint32 *target = (uint32 *)((byte *)relSegment + rel[i].r_offset - _segmentVMA);
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// uint32 origTarget = *target; //Save for debugging
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// Act differently based on the type of relocation
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switch (REL_TYPE(rel[i].r_info)) {
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case R_ARM_ABS32:
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case R_ARM_TARGET1:
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if (sym->st_shndx < SHN_LOPROC) { // Only shift for plugin section.
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a = *target; // Get full 32 bits of addend
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relocation = a - _segmentVMA + Elf32_Addr(_segment); // Shift by main offset
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*target = relocation;
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// debug(8, "elfloader: R_ARM_ABS32: i=%d, a=%x, origTarget=%x, target=%x", i, a, origTarget, *target);
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}
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break;
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case R_ARM_THM_CALL:
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// debug(8, "elfloader: R_ARM_THM_CALL: PC-relative jump, ld takes care of necessary relocation work for us.");
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break;
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case R_ARM_CALL:
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case R_ARM_JUMP24:
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// debug(8, "elfloader: R_ARM_CALL/R_ARM_JUMP24: PC-relative jump, ld takes care of necessary relocation work for us.");
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break;
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case R_ARM_V4BX:
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// debug(8, "elfloader: R_ARM_V4BX: No relocation calculation necessary.");
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break;
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default:
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warning("elfloader: Unknown relocation type %d.", REL_TYPE(rel[i].r_info));
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free(rel);
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return false;
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}
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}
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free(rel);
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return true;
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}
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bool ARMDLObject::relocateRels(Elf32_Ehdr *ehdr, Elf32_Shdr *shdr) {
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// Loop over sections, finding relocation sections
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for (uint32 i = 0; i < ehdr->e_shnum; i++) {
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Elf32_Shdr *curShdr = &(shdr[i]);
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if ((curShdr->sh_type == SHT_REL || curShdr->sh_type == SHT_RELA) && // Check for a relocation section
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curShdr->sh_entsize == sizeof(Elf32_Rel) && // Check for proper relocation size
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int32(curShdr->sh_link) == _symtab_sect && // Check that the sh_link connects to our symbol table
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curShdr->sh_info < ehdr->e_shnum && // Check that the relocated section exists
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(shdr[curShdr->sh_info].sh_flags & SHF_ALLOC)) { // Check if relocated section resides in memory
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if (curShdr->sh_type == SHT_RELA) {
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warning("elfloader: RELA entries not supported yet!");
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return false;
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}
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if (!relocate(curShdr->sh_offset, curShdr->sh_size, _segment))
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return false;
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}
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}
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return true;
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}
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#endif /* defined(DYNAMIC_MODULES) && defined(USE_ELF_LOADER) && defined(ARM_TARGET) */
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