| 1 | #include <algorithm> |
| 2 | #include <fcntl.h> |
| 3 | #include <stdio.h> |
| 4 | #include <stdlib.h> |
| 5 | #include <string.h> |
| 6 | #include <sys/mman.h> |
| 7 | #include <sys/stat.h> |
| 8 | #include <sys/types.h> |
| 9 | #include <unistd.h> |
| 10 | |
| 11 | #ifdef __APPLE__ |
| 12 | # include "elf.h" |
| 13 | #else |
| 14 | # include <elf.h> |
| 15 | #endif |
| 16 | |
| 17 | #define DT_VERSYM 0x6ffffff0 |
| 18 | #define DT_VERNEEDED 0x6ffffffe |
| 19 | #define DT_VERNEEDNUM 0x6fffffff |
| 20 | |
| 21 | template<typename ElfHeaderType /*Elf{32,64}_Ehdr*/, |
| 22 | typename ElfSectionHeaderType /*Elf{32,64}_Shdr*/, |
| 23 | typename ElfDynamicSectionEntryType /* Elf{32,64}_Dyn */> |
| 24 | bool process_elf(uint8_t* bytes, size_t elf_file_size, char const* file_name) |
| 25 | { |
| 26 | if (sizeof(ElfSectionHeaderType) > elf_file_size) { |
| 27 | fprintf(stderr, "termux-elf-cleaner: Elf header for '%s' would end at %zu but file size only %zu\n", file_name, sizeof(ElfSectionHeaderType), elf_file_size); |
| 28 | return false; |
| 29 | } |
| 30 | ElfHeaderType* elf_hdr = reinterpret_cast<ElfHeaderType*>(bytes); |
| 31 | |
| 32 | size_t last_section_header_byte = elf_hdr->e_shoff + sizeof(ElfSectionHeaderType) * elf_hdr->e_shnum; |
| 33 | if (last_section_header_byte > elf_file_size) { |
| 34 | fprintf(stderr, "termux-elf-cleaner: Section header for '%s' would end at %zu but file size only %zu\n", file_name, last_section_header_byte, elf_file_size); |
| 35 | return false; |
| 36 | } |
| 37 | ElfSectionHeaderType* section_header_table = reinterpret_cast<ElfSectionHeaderType*>(bytes + elf_hdr->e_shoff); |
| 38 | |
| 39 | for (unsigned int i = 1; i < elf_hdr->e_shnum; i++) { |
| 40 | ElfSectionHeaderType* section_header_entry = section_header_table + i; |
| 41 | if (section_header_entry->sh_type == SHT_DYNAMIC) { |
| 42 | size_t const last_dynamic_section_byte = section_header_entry->sh_offset + section_header_entry->sh_size; |
| 43 | if (last_dynamic_section_byte > elf_file_size) { |
| 44 | fprintf(stderr, "termux-elf-cleaner: Dynamic section for '%s' would end at %zu but file size only %zu\n", file_name, last_dynamic_section_byte, elf_file_size); |
| 45 | return false; |
| 46 | } |
| 47 | |
| 48 | size_t const dynamic_section_entries = section_header_entry->sh_size / sizeof(ElfDynamicSectionEntryType); |
| 49 | ElfDynamicSectionEntryType* const dynamic_section = |
| 50 | reinterpret_cast<ElfDynamicSectionEntryType*>(bytes + section_header_entry->sh_offset); |
| 51 | |
| 52 | unsigned int last_nonnull_entry_idx = 0; |
| 53 | for (unsigned int j = dynamic_section_entries - 1; j > 0; j--) { |
| 54 | ElfDynamicSectionEntryType* dynamic_section_entry = dynamic_section + j; |
| 55 | if (dynamic_section_entry->d_tag != DT_NULL) { |
| 56 | last_nonnull_entry_idx = j; |
| 57 | break; |
| 58 | } |
| 59 | } |
| 60 | |
| 61 | for (unsigned int j = 0; j < dynamic_section_entries; j++) { |
| 62 | ElfDynamicSectionEntryType* dynamic_section_entry = dynamic_section + j; |
| 63 | char const* removed_name = nullptr; |
| 64 | switch (dynamic_section_entry->d_tag) { |
| 65 | case DT_VERSYM: removed_name = "DT_VERSYM"; break; |
| 66 | case DT_VERNEEDED: removed_name = "DT_VERNEEDED"; break; |
| 67 | case DT_VERNEEDNUM: removed_name = "DT_VERNEEDNUM"; break; |
| 68 | case DT_VERDEF: removed_name = "DT_VERDEF"; break; |
| 69 | case DT_VERDEFNUM: removed_name = "DT_VERDEFNUM"; break; |
| 70 | case DT_RPATH: removed_name = "DT_RPATH"; break; |
| 71 | case DT_RUNPATH: removed_name = "DT_RUNPATH"; break; |
| 72 | } |
| 73 | if (removed_name != nullptr) { |
| 74 | printf("termux-elf-cleaner: Removing the %s dynamic section entry from '%s'\n", removed_name, file_name); |
| 75 | // Tag the entry with DT_NULL and put it last: |
| 76 | dynamic_section_entry->d_tag = DT_NULL; |
| 77 | // Decrease j to process new entry index: |
| 78 | std::swap(dynamic_section[j--], dynamic_section[last_nonnull_entry_idx--]); |
| 79 | } |
| 80 | } |
| 81 | } else if (section_header_entry->sh_type == SHT_GNU_verdef || |
| 82 | section_header_entry->sh_type == SHT_GNU_verneed || |
| 83 | section_header_entry->sh_type == SHT_GNU_versym) { |
| 84 | printf("termux-elf-cleaner: Removing version section from '%s'\n", file_name); |
| 85 | section_header_entry->sh_type = SHT_NULL; |
| 86 | } |
| 87 | } |
| 88 | return true; |
| 89 | } |
| 90 | |
| 91 | |
| 92 | int main(int argc, char const** argv) |
| 93 | { |
| 94 | if (argc < 2 || (argc == 2 && strcmp(argv[1], "-h")==0)) { |
| 95 | fprintf(stderr, "usage: %s <filename>\n", argv[0]); |
| 96 | fprintf(stderr, " Processes ELF files to remove DT_VERNEEDED, DT_VERNEEDNUM, DT_RPATH\n" |
| 97 | " and DT_RUNPATH entries (which the Android linker warns about)\n"); |
| 98 | return 1; |
| 99 | } |
| 100 | |
| 101 | for (int i = 1; i < argc; i++) { |
| 102 | char const* file_name = argv[i]; |
| 103 | int fd = open(file_name, O_RDWR); |
| 104 | if (fd < 0) { |
| 105 | char* error_message; |
| 106 | if (asprintf(&error_message, "open(\"%s\")", file_name) == -1) error_message = (char*) "open()"; |
| 107 | perror(error_message); |
| 108 | return 1; |
| 109 | } |
| 110 | |
| 111 | struct stat st; |
| 112 | if (fstat(fd, &st) < 0) { perror("fstat()"); return 1; } |
| 113 | |
| 114 | if (st.st_size < (long long) sizeof(Elf32_Ehdr)) { |
| 115 | close(fd); |
| 116 | continue; |
| 117 | } |
| 118 | |
| 119 | void* mem = mmap(0, st.st_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); |
| 120 | if (mem == MAP_FAILED) { perror("mmap()"); return 1; } |
| 121 | |
| 122 | uint8_t* bytes = reinterpret_cast<uint8_t*>(mem); |
| 123 | if (!(bytes[0] == 0x7F && bytes[1] == 'E' && bytes[2] == 'L' && bytes[3] == 'F')) { |
| 124 | // Not the ELF magic number. |
| 125 | munmap(mem, st.st_size); |
| 126 | close(fd); |
| 127 | continue; |
| 128 | } |
| 129 | |
| 130 | if (bytes[/*EI_DATA*/5] != 1) { |
| 131 | fprintf(stderr, "termux-elf-cleaner: Not little endianness in '%s'\n", file_name); |
| 132 | munmap(mem, st.st_size); |
| 133 | close(fd); |
| 134 | continue; |
| 135 | } |
| 136 | |
| 137 | uint8_t const bit_value = bytes[/*EI_CLASS*/4]; |
| 138 | if (bit_value == 1) { |
| 139 | if (!process_elf<Elf32_Ehdr, Elf32_Shdr, Elf32_Dyn>(bytes, st.st_size, file_name)) return 1; |
| 140 | } else if (bit_value == 2) { |
| 141 | if (!process_elf<Elf64_Ehdr, Elf64_Shdr, Elf64_Dyn>(bytes, st.st_size, file_name)) return 1; |
| 142 | } else { |
| 143 | printf("termux-elf-cleaner: Incorrect bit value %d in '%s'\n", bit_value, file_name); |
| 144 | return 1; |
| 145 | } |
| 146 | |
| 147 | if (msync(mem, st.st_size, MS_SYNC) < 0) { perror("msync()"); return 1; } |
| 148 | |
| 149 | munmap(mem, st.st_size); |
| 150 | close(fd); |
| 151 | } |
| 152 | return 0; |
| 153 | } |
| 154 | |