mirror of
https://github.com/RGBCube/serenity
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69 lines
2.4 KiB
C++
69 lines
2.4 KiB
C++
/*
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* Copyright (c) 2021, Gunnar Beutner <gbeutner@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <LibC/elf.h>
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#include <LibELF/Relocation.h>
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namespace ELF {
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bool perform_relative_relocations(FlatPtr base_address)
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{
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ElfW(Ehdr)* header = (ElfW(Ehdr)*)(base_address);
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ElfW(Phdr)* pheader = (ElfW(Phdr)*)(base_address + header->e_phoff);
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FlatPtr dynamic_section_addr = 0;
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for (size_t i = 0; i < (size_t)header->e_phnum; ++i, ++pheader) {
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if (pheader->p_type != PT_DYNAMIC)
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continue;
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dynamic_section_addr = pheader->p_vaddr + base_address;
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}
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if (!dynamic_section_addr)
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return false;
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FlatPtr relocation_section_addr = 0;
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size_t relocation_table_size = 0;
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size_t relocation_count = 0;
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bool use_addend = false;
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auto* dyns = reinterpret_cast<const ElfW(Dyn)*>(dynamic_section_addr);
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for (unsigned i = 0;; ++i) {
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auto& dyn = dyns[i];
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if (dyn.d_tag == DT_NULL)
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break;
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if (dyn.d_tag == DT_RELA)
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use_addend = true;
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if (dyn.d_tag == DT_REL || dyn.d_tag == DT_RELA)
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relocation_section_addr = base_address + dyn.d_un.d_ptr;
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else if (dyn.d_tag == DT_RELCOUNT || dyn.d_tag == DT_RELACOUNT)
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relocation_count = dyn.d_un.d_val;
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else if (dyn.d_tag == DT_RELSZ || dyn.d_tag == DT_RELASZ)
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relocation_table_size = dyn.d_un.d_val;
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}
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if (!relocation_section_addr || !relocation_table_size || !relocation_count)
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return false;
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auto relocation_entry_size = relocation_table_size / relocation_count;
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for (unsigned i = 0; i < relocation_count; ++i) {
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size_t offset_in_section = i * relocation_entry_size;
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auto* relocation = (ElfW(Rela)*)(relocation_section_addr + offset_in_section);
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#if ARCH(I386)
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VERIFY(ELF32_R_TYPE(relocation->r_info) == R_386_RELATIVE);
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#else
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VERIFY(ELF64_R_TYPE(relocation->r_info) == R_X86_64_RELATIVE);
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#endif
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auto* patch_address = (FlatPtr*)(base_address + relocation->r_offset);
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FlatPtr relocated_address;
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if (use_addend) {
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relocated_address = base_address + relocation->r_addend;
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} else {
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__builtin_memcpy(&relocated_address, patch_address, sizeof(relocated_address));
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relocated_address += base_address;
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}
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__builtin_memcpy(patch_address, &relocated_address, sizeof(relocated_address));
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}
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return true;
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}
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}
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