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#include "elf.h"
#include "file.h"
#include "minicc.h"
#include <iostream>
// TODO
//#include <boost/endian/conversion.hpp>
#include <cstring>
#define PAD
// Helper Functions
namespace {
// On amd64, we need at least 4096 bytes aligment. Otherwise we get segfaults at startup
const size_t PAGE_SIZE = 0x1000;
// Helper function: returns size with full pages: 0, 4096, ...
size_t paged_size(const std::vector<uint8_t>& data)
{
return (data.size() + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1);
}
void AddFileHeader(std::vector<uint8_t>& elf, const std::vector<uint8_t>& code, const std::vector<uint8_t>& data)
{
Elf::FileHeader fh;
#ifdef PAD
fh.e_shoff = PAGE_SIZE + paged_size(code) + data.size() + 23;
#else
fh.e_shoff = sizeof(fh) + sizeof(Elf::ProgramHeader) * 2 + code.size() + data.size() + 23;
#endif
size_t old_size {elf.size()};
elf.resize(old_size + sizeof(fh));
std::memcpy(elf.data() + old_size, reinterpret_cast<void*>(&fh), sizeof(fh));
}
void AddProgramHeaderCode(std::vector<uint8_t>& elf, const std::vector<uint8_t>& code, const std::vector<uint8_t>& data)
{
Elf::ProgramHeader ph;
#ifdef PAD
ph.p_offset = PAGE_SIZE;
ph.p_align = PAGE_SIZE;
#else
ph.p_offset = sizeof(Elf::FileHeader) + sizeof(Elf::ProgramHeader) * 2;
#endif
ph.p_filesz = code.size();
ph.p_memsz = code.size();
size_t old_size {elf.size()};
elf.resize(old_size + sizeof(ph));
std::memcpy(elf.data() + old_size, reinterpret_cast<void*>(&ph), sizeof(ph));
}
void AddProgramHeaderData(std::vector<uint8_t>& elf, const std::vector<uint8_t>& code, const std::vector<uint8_t>& data)
{
Elf::ProgramHeader ph;
#ifdef PAD
ph.p_offset = PAGE_SIZE + paged_size(code);
ph.p_align = PAGE_SIZE;
#else
ph.p_offset = sizeof(Elf::FileHeader) + sizeof(Elf::ProgramHeader) * 2 + code.size();
#endif
ph.p_filesz = data.size();
ph.p_memsz = data.size();
ph.p_vaddr = 0x401000 + paged_size(code);
ph.p_paddr = 0x401000 + paged_size(code);
ph.p_flags = 6; // RW
size_t old_size {elf.size()};
elf.resize(old_size + sizeof(ph));
std::memcpy(elf.data() + old_size, reinterpret_cast<void*>(&ph), sizeof(ph));
}
void AddSectionHeaderNull(std::vector<uint8_t>& elf, const std::vector<uint8_t>& code, const std::vector<uint8_t>& data)
{
Elf::SectionHeader sh;
sh.sh_name = 0; // offset in section
sh.sh_size = 0;
sh.sh_type = 0; // <null>
sh.sh_flags = 0;
sh.sh_addr = 0;
sh.sh_offset = 0;
size_t old_size {elf.size()};
elf.resize(old_size + sizeof(sh));
std::memcpy(elf.data() + old_size, reinterpret_cast<void*>(&sh), sizeof(sh));
}
void AddSectionHeaderText(std::vector<uint8_t>& elf, const std::vector<uint8_t>& code, const std::vector<uint8_t>& data)
{
Elf::SectionHeader sh;
sh.sh_name = 1; // offset in section
sh.sh_size = code.size();
sh.sh_type = 1; // program
#ifdef PAD
sh.sh_offset = PAGE_SIZE;
#else
sh.sh_offset = sizeof(Elf::FileHeader) + sizeof(Elf::ProgramHeader) * 2;
#endif
sh.sh_addralign = 1;
size_t old_size {elf.size()};
elf.resize(old_size + sizeof(sh));
std::memcpy(elf.data() + old_size, reinterpret_cast<void*>(&sh), sizeof(sh));
}
void AddSectionHeaderData(std::vector<uint8_t>& elf, const std::vector<uint8_t>& code, const std::vector<uint8_t>& data)
{
Elf::SectionHeader sh;
sh.sh_name = 7; // offset in section
sh.sh_size = data.size();
sh.sh_type = 1; // program (also data)
#ifdef PAD
sh.sh_offset = PAGE_SIZE + paged_size(code);
#else
sh.sh_offset = sizeof(Elf::FileHeader) + sizeof(Elf::ProgramHeader) * 2 + code.size();
#endif
sh.sh_addralign = 1;
size_t old_size {elf.size()};
elf.resize(old_size + sizeof(sh));
std::memcpy(elf.data() + old_size, reinterpret_cast<void*>(&sh), sizeof(sh));
}
void AddSectionHeaderSectionNames(std::vector<uint8_t>& elf, const std::vector<uint8_t>& code, const std::vector<uint8_t>& data)
{
Elf::SectionHeader sh;
sh.sh_name = 13; // offset in section
sh.sh_size = 23;
sh.sh_type = 3; // section names
sh.sh_flags = 0;
sh.sh_addr = 0;
#ifdef PAD
sh.sh_offset = PAGE_SIZE + paged_size(code) + data.size();
#else
sh.sh_offset = sizeof(Elf::FileHeader) + sizeof(Elf::ProgramHeader) * 2 + code.size() + data.size();
#endif
sh.sh_addralign = 1;
size_t old_size {elf.size()};
elf.resize(old_size + sizeof(sh));
std::memcpy(elf.data() + old_size, reinterpret_cast<void*>(&sh), sizeof(sh));
}
void PadUpTo(std::vector<uint8_t>& elf, size_t size)
{
if (elf.size() < size) {
elf.resize(size);
} else if (elf.size() > size)
throw std::runtime_error("Padding not possible. Too many bytes already. ("s + std::to_string(elf.size()) + " > "s + std::to_string(size) + ")"s);
}
}
void Elf::Write(const std::filesystem::path& path, const std::vector<uint8_t>& code, const std::vector<uint8_t>& data)
{
std::vector<uint8_t> elf;
AddFileHeader(elf, code, data);
AddProgramHeaderCode(elf, code, data);
AddProgramHeaderData(elf, code, data);
#ifdef PAD
PadUpTo(elf, PAGE_SIZE);
#endif
elf.insert(elf.end(), code.begin(), code.end());
#ifdef PAD
PadUpTo(elf, PAGE_SIZE + paged_size(code));
#endif
elf.insert(elf.end(), data.begin(), data.end());
std::string section_names("\0.text\0.data\0.shstrtab\0", 23);
if (section_names.size() != 23)
throw std::runtime_error("Bad size");
size_t old_size {elf.size()};
elf.resize(old_size + section_names.size());
std::memcpy(elf.data() + old_size, section_names.data(), section_names.size());
AddSectionHeaderNull(elf, code, data);
AddSectionHeaderText(elf, code, data);
AddSectionHeaderData(elf, code, data);
AddSectionHeaderSectionNames(elf, code, data);
File::setFile(path, elf);
fs::permissions(path, fs::perms::owner_exec | fs::perms::group_exec | fs::perms::others_exec, fs::perm_options::add);
}
std::vector<uint8_t> Elf::Read(const std::filesystem::path& path)
{
std::vector<uint8_t> result;
// TODO
return result;
}
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