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/**
* @file elfload.cpp
* @brief Loads ELF binary data into memory for execution.
*
* Copyright (C) 2021 Clyne Sullivan
*
* Distributed under the GNU GPL v3 or later. You should have received a copy of
* the GNU General Public License along with this program.
* If not, see <https://www.gnu.org/licenses/>.
*/
#include "elfload.hpp"
#include "elf.h"
#include <algorithm>
#include <cstring>
__attribute__((section(".convdata")))
ELFManager::EntryFunc ELFManager::m_entry = nullptr;
std::array<unsigned char, MAX_ELF_FILE_SIZE> ELFManager::m_file_buffer = {};
static const unsigned char elf_header[] = { '\177', 'E', 'L', 'F' };
__attribute__((section(".convcode")))
ELFManager::EntryFunc ELFManager::loadedElf()
{
return m_entry;
}
unsigned char *ELFManager::fileBuffer()
{
return m_file_buffer.data();
}
void ELFManager::unload()
{
m_entry = nullptr;
}
template<typename T>
constexpr static auto ptr_from_offset(void *base, uint32_t offset)
{
return reinterpret_cast<T>(reinterpret_cast<uint8_t *>(base) + offset);
}
ELFManager::EntryFunc ELFManager::loadFromInternalBuffer()
{
auto elf_data = m_file_buffer.data();
// Check the ELF's header signature
auto ehdr = reinterpret_cast<Elf32_Ehdr *>(elf_data);
if (!std::equal(ehdr->e_ident, ehdr->e_ident + 4, elf_header))
return nullptr;
// Iterate through program header LOAD sections
bool loaded = false;
auto phdr = ptr_from_offset<Elf32_Phdr *>(elf_data, ehdr->e_phoff);
for (Elf32_Half i = 0; i < ehdr->e_phnum; i++) {
if (phdr->p_type == PT_LOAD) {
if (phdr->p_filesz == 0) {
std::memset(reinterpret_cast<void *>(phdr->p_vaddr),
0,
phdr->p_memsz);
} else {
std::memcpy(reinterpret_cast<void *>(phdr->p_vaddr),
ptr_from_offset<void *>(elf_data, phdr->p_offset),
phdr->p_filesz);
if (!loaded)
loaded = true;
}
}
phdr = ptr_from_offset<Elf32_Phdr *>(phdr, ehdr->e_phentsize);
}
return loaded ? reinterpret_cast<ELFManager::EntryFunc>(ehdr->e_entry) : nullptr;
}
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