diff options
| -rw-r--r-- | elf.cpp | 159 | ||||
| -rw-r--r-- | elf.h | 8 | ||||
| -rw-r--r-- | test-elf.cpp | 20 |
3 files changed, 130 insertions, 57 deletions
@@ -2,50 +2,82 @@ #include "file.h" +#include <iostream> + // TODO //#include <boost/endian/conversion.hpp> #include <cstring> -// We need at least 4096 bytes aligment. Otherwise we get segfaults at startup -#define PAD 0x1000 +#define PAD // Helper Functions namespace { - void AddFileHeader(std::vector<uint8_t>& data, const std::vector<uint8_t>& code) + // 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 = PAD + code.size() + 17; + fh.e_shoff = PAGE_SIZE + paged_size(code) + data.size() + 23; #else - fh.e_shoff = sizeof(fh) + sizeof(Elf::ProgramHeader) + code.size() + 17; + fh.e_shoff = sizeof(fh) + sizeof(Elf::ProgramHeader) * 2 + code.size() + data.size() + 23; #endif - size_t old_size {data.size()}; - data.resize(old_size + sizeof(fh)); - std::memcpy(data.data() + old_size, reinterpret_cast<void*>(&fh), sizeof(fh)); + 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 AddProgramHeader(std::vector<uint8_t>& data, const std::vector<uint8_t>& code) + 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 = PAD; - ph.p_align = PAD; + ph.p_offset = PAGE_SIZE; + ph.p_align = PAGE_SIZE; #else - ph.p_offset = sizeof(Elf::FileHeader) + sizeof(Elf::ProgramHeader); + 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 {data.size()}; - data.resize(old_size + sizeof(ph)); - std::memcpy(data.data() + old_size, reinterpret_cast<void*>(&ph), sizeof(ph)); + 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>& data, const std::vector<uint8_t>& code) + void AddSectionHeaderNull(std::vector<uint8_t>& elf, const std::vector<uint8_t>& code, const std::vector<uint8_t>& data) { Elf::SectionHeader sh; @@ -56,12 +88,12 @@ namespace { sh.sh_addr = 0; sh.sh_offset = 0; - size_t old_size {data.size()}; - data.resize(old_size + sizeof(sh)); - std::memcpy(data.data() + old_size, reinterpret_cast<void*>(&sh), sizeof(sh)); + 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>& data, const std::vector<uint8_t>& code) + void AddSectionHeaderText(std::vector<uint8_t>& elf, const std::vector<uint8_t>& code, const std::vector<uint8_t>& data) { Elf::SectionHeader sh; @@ -69,73 +101,100 @@ namespace { sh.sh_size = code.size(); sh.sh_type = 1; // program #ifdef PAD - sh.sh_offset = PAD; + sh.sh_offset = PAGE_SIZE; #else - sh.sh_offset = sizeof(Elf::FileHeader) + sizeof(Elf::ProgramHeader); + sh.sh_offset = sizeof(Elf::FileHeader) + sizeof(Elf::ProgramHeader) * 2; #endif sh.sh_addralign = 1; - size_t old_size {data.size()}; - data.resize(old_size + sizeof(sh)); - std::memcpy(data.data() + old_size, reinterpret_cast<void*>(&sh), sizeof(sh)); + 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>& data, const std::vector<uint8_t>& code) + 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 = 17; + 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 = PAD + code.size(); + sh.sh_offset = PAGE_SIZE + paged_size(code) + data.size(); #else - sh.sh_offset = sizeof(Elf::FileHeader) + sizeof(Elf::ProgramHeader) + code.size(); + sh.sh_offset = sizeof(Elf::FileHeader) + sizeof(Elf::ProgramHeader) * 2 + code.size() + data.size(); #endif sh.sh_addralign = 1; - size_t old_size {data.size()}; - data.resize(old_size + sizeof(sh)); - std::memcpy(data.data() + old_size, reinterpret_cast<void*>(&sh), sizeof(sh)); + 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>& data, size_t size) + void PadUpTo(std::vector<uint8_t>& elf, size_t size) { - if (data.size() < size) { - data.resize(size); + if (elf.size() < size) { + elf.resize(size); } else throw std::runtime_error("Padding not possible. Too many bytes already."); } } -void Elf::Write(const std::filesystem::path& path, const std::vector<uint8_t>& code) +void Elf::Write(const std::filesystem::path& path, const std::vector<uint8_t>& code, const std::vector<uint8_t>& data) { - std::vector<uint8_t> data; + std::vector<uint8_t> elf; - AddFileHeader(data, code); - AddProgramHeader(data, code); + AddFileHeader(elf, code, data); + AddProgramHeaderCode(elf, code, data); + AddProgramHeaderData(elf, code, data); #ifdef PAD - PadUpTo(data, PAD); + PadUpTo(elf, PAGE_SIZE); #endif - data.insert(data.end(), code.begin(), code.end()); + elf.insert(elf.end(), code.begin(), code.end()); + +#ifdef PAD + PadUpTo(elf, PAGE_SIZE + paged_size(code)); +#endif - std::string section_names("\0.text\0.shstrtab\0", 17); - if (section_names.size() != 17) + 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 {data.size()}; - data.resize(old_size + section_names.size()); - std::memcpy(data.data() + old_size, section_names.data(), section_names.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(data, code); - AddSectionHeaderText(data, code); - AddSectionHeaderSectionNames(data, code); + AddSectionHeaderNull(elf, code, data); + AddSectionHeaderText(elf, code, data); + AddSectionHeaderData(elf, code, data); + AddSectionHeaderSectionNames(elf, code, data); - File::setFile(path, data); + File::setFile(path, elf); } std::vector<uint8_t> Elf::Read(const std::filesystem::path& path) @@ -42,10 +42,10 @@ struct FileHeader uint32_t e_flags{}; uint16_t e_ehsize{0x40}; // size of this header uint16_t e_phentsize{0x38}; // size of program header - uint16_t e_phnum{1}; // 1 program header + uint16_t e_phnum{2}; // program headers: .text, .data uint16_t e_shentsize{0x40}; // size of section header - uint16_t e_shnum{3}; // number of section headers - uint16_t e_shstrndx{2}; // 1st section header contains section names + uint16_t e_shnum{4}; // number of section headers + uint16_t e_shstrndx{3}; // 1st section header contains section names }; // Segment @@ -76,7 +76,7 @@ struct SectionHeader }; #pragma pack(pop) -void Write(const std::filesystem::path& path, const std::vector<uint8_t>&); +void Write(const std::filesystem::path& path, const std::vector<uint8_t>& code, const std::vector<uint8_t>& data); std::vector<uint8_t> Read(const std::filesystem::path& path); } diff --git a/test-elf.cpp b/test-elf.cpp index d3fa9a9..46ef267 100644 --- a/test-elf.cpp +++ b/test-elf.cpp @@ -35,7 +35,7 @@ protected: } void TearDown(){ std::error_code ec; - //fs::remove(TempFilename(), ec); + fs::remove(TempFilename(), ec); } }; @@ -44,13 +44,27 @@ TEST_F(ElfTest, read) { } #endif -TEST_F(ElfTest, write) { +TEST_F(ElfTest, write_code) { Elf::Write(TempFilename(), { 0x48, 0xc7, 0xc0, 0x3c, 0x00, 0x00, 0x00, // mov $0x3c,%rax # syscall 60 0x48, 0x31, 0xff, // xor %rdi,%rdi # exit code 0 0x0f, 0x05, // syscall - }); + }, {}); + + ASSERT_TRUE(fs::exists(TempFilename())); + ASSERT_GT(fs::file_size(TempFilename()), 0); +} + +TEST_F(ElfTest, write_code_data) { + Elf::Write(TempFilename(), + { + 0x48, 0xc7, 0xc0, 0x3c, 0x00, 0x00, 0x00, // mov $0x3c,%rax # syscall 60 + 0x48, 0x8b, 0x3c, 0x25, 0x00, 0x20, 0x40, // mov 0x402000,%rdi # use value from data segment as exit code + 0, + 0x0f, 0x05, // syscall + }, + {1, 0, 0, 0, 0, 0, 0, 0}); ASSERT_TRUE(fs::exists(TempFilename())); ASSERT_GT(fs::file_size(TempFilename()), 0); |