| 1 | #ifndef ELF_HPP |
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| 2 | #define ELF_HPP |
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| 3 | |
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| 4 | #include "common.hpp" |
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| 5 | |
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| 6 | #if IS_LINUX |
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| 7 | #include <array> |
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| 8 | #include <cstdint> |
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| 9 | #include <cstdio> |
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| 10 | #include <cstring> |
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| 11 | |
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| 12 | #include <elf.h> |
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| 13 | |
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| 14 | template<typename T, typename std::enable_if<std::is_integral<T>::value, int>::type = 0> |
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| 15 | T elf_byteswap_if_needed(T value, bool elf_is_little) { |
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| 16 | if(is_little_endian() == elf_is_little) { |
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| 17 | return value; |
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| 18 | } else { |
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| 19 | return byteswap(value); |
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| 20 | } |
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| 21 | } |
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| 22 | |
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| 23 | // TODO: Address code duplication here. Do we actually have to care about 32-bit if the library is compiled as 64-bit? |
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| 24 | // I think probably not... |
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| 25 | |
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| 26 | // TODO: Re-evaluate use of off_t |
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| 27 | // I think we can rely on PT_PHDR https://stackoverflow.com/q/61568612/15675011... |
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| 28 | static uintptr_t elf_get_module_image_base_from_program_table( |
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| 29 | FILE* file, |
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| 30 | bool is_64, |
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| 31 | bool is_little_endian, |
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| 32 | off_t e_phoff, |
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| 33 | off_t e_phentsize, |
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| 34 | int e_phnum |
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| 35 | ) { |
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| 36 | for(int i = 0; i < e_phnum; i++) { |
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| 37 | if(is_64) { |
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| 38 | Elf64_Phdr program_header = load_bytes<Elf64_Phdr>(file, e_phoff + e_phentsize * i); |
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| 39 | if(elf_byteswap_if_needed(program_header.p_type, is_little_endian) == PT_PHDR) { |
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| 40 | return elf_byteswap_if_needed(program_header.p_vaddr, is_little_endian) |
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| 41 | - elf_byteswap_if_needed(program_header.p_offset, is_little_endian); |
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| 42 | } |
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| 43 | } else { |
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| 44 | Elf32_Phdr program_header = load_bytes<Elf32_Phdr>(file, e_phoff + e_phentsize * i); |
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| 45 | if(elf_byteswap_if_needed(program_header.p_type, is_little_endian) == PT_PHDR) { |
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| 46 | return elf_byteswap_if_needed(program_header.p_vaddr, is_little_endian) |
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| 47 | - elf_byteswap_if_needed(program_header.p_offset, is_little_endian); |
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| 48 | } |
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| 49 | } |
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| 50 | } |
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| 51 | return 0; |
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| 52 | } |
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| 53 | |
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| 54 | static uintptr_t elf_get_module_image_base(const std::string& obj_path) { |
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| 55 | FILE* file = fopen(obj_path.c_str(), "rb"); |
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| 56 | if(file == nullptr) { |
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| 57 | throw file_error(); |
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| 58 | } |
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| 59 | // Initial checks/metadata |
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| 60 | auto magic = load_bytes<std::array<char, 4>>(file, 0); |
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| 61 | internal_verify(magic == (std::array<char, 4>{0x7F, 'E', 'L', 'F'})); |
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| 62 | bool is_64 = load_bytes<uint8_t>(file, 4) == 2; |
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| 63 | bool is_little_endian = load_bytes<uint8_t>(file, 5) == 1; |
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| 64 | internal_verify(load_bytes<uint8_t>(file, 6) == 1, "Unexpected ELF version"); |
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| 65 | // |
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| 66 | if(is_64) { |
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| 67 | Elf64_Ehdr file_header = load_bytes<Elf64_Ehdr>(file, 0); |
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| 68 | internal_verify(file_header.e_ehsize == sizeof(Elf64_Ehdr)); |
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| 69 | return elf_get_module_image_base_from_program_table( |
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| 70 | file, |
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| 71 | is_64, |
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| 72 | is_little_endian, |
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| 73 | elf_byteswap_if_needed(file_header.e_phoff, is_little_endian), |
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| 74 | elf_byteswap_if_needed(file_header.e_phentsize, is_little_endian), |
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| 75 | elf_byteswap_if_needed(file_header.e_phnum, is_little_endian) |
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| 76 | ); |
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| 77 | } else { |
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| 78 | Elf32_Ehdr file_header = load_bytes<Elf32_Ehdr>(file, 0); |
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| 79 | internal_verify(file_header.e_ehsize == sizeof(Elf32_Ehdr)); |
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| 80 | return elf_get_module_image_base_from_program_table( |
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| 81 | file, |
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| 82 | is_64, |
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| 83 | is_little_endian, |
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| 84 | elf_byteswap_if_needed(file_header.e_phoff, is_little_endian), |
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| 85 | elf_byteswap_if_needed(file_header.e_phentsize, is_little_endian), |
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| 86 | elf_byteswap_if_needed(file_header.e_phnum, is_little_endian) |
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| 87 | ); |
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| 88 | } |
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| 89 | } |
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| 90 | |
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| 91 | #endif |
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| 92 | |
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| 93 | #endif |
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