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62 lines
1.7 KiB
C++
62 lines
1.7 KiB
C++
/**
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* @file elf_load.cpp
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* @brief Loads ELF binary data into memory for execution.
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*
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* Copyright (C) 2020 Clyne Sullivan
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*
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* Distributed under the GNU GPL v3 or later. You should have received a copy of
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* the GNU General Public License along with this program.
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* If not, see <https://www.gnu.org/licenses/>.
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*/
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#include "elf_load.hpp"
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#include "elf_format.hpp"
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#include <algorithm>
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#include <cstring>
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static const unsigned char elf_header[] = { '\177', 'E', 'L', 'F' };
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template<typename T>
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constexpr static auto ptr_from_offset(void *base, uint32_t offset)
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{
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return reinterpret_cast<T>(reinterpret_cast<uint8_t *>(base) + offset);
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}
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namespace ELF {
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Entry load(void *elf_data)
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{
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// Check the ELF's header signature
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auto ehdr = reinterpret_cast<Elf32_Ehdr *>(elf_data);
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if (!std::equal(ehdr->e_ident, ehdr->e_ident + 4, elf_header))
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return nullptr;
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// Iterate through program header LOAD sections
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bool loaded = false;
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auto phdr = ptr_from_offset<Elf32_Phdr *>(elf_data, ehdr->e_phoff);
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for (Elf32_Half i = 0; i < ehdr->e_phnum; i++) {
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if (phdr->p_type == PT_LOAD) {
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if (phdr->p_filesz == 0) {
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std::memset(reinterpret_cast<void *>(phdr->p_vaddr),
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0,
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phdr->p_memsz);
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} else {
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std::memcpy(reinterpret_cast<void *>(phdr->p_vaddr),
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ptr_from_offset<void *>(elf_data, phdr->p_offset),
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phdr->p_filesz);
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if (!loaded)
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loaded = true;
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}
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}
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phdr = ptr_from_offset<Elf32_Phdr *>(phdr, ehdr->e_phentsize);
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}
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return loaded ? reinterpret_cast<Entry>(ehdr->e_entry) : nullptr;
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}
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} // namespace ELF
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