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-rw-r--r--elf.cpp159
1 files changed, 109 insertions, 50 deletions
diff --git a/elf.cpp b/elf.cpp
index 2923392..0ad7a04 100644
--- a/elf.cpp
+++ b/elf.cpp
@@ -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)
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