Commit | Line | Data |
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59f0d218 FF |
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_VERNEEDED 0x6ffffffe | |
18 | #define DT_VERNEEDNUM 0x6fffffff | |
19 | ||
20 | template<typename ElfHeaderType /*Elf{32,64}_Ehdr*/, | |
21 | typename ElfSectionHeaderType /*Elf{32,64}_Shdr*/, | |
22 | typename ElfDynamicSectionEntryType /* Elf{32,64}_Dyn */> | |
009c8d94 | 23 | bool process_elf(uint8_t* bytes, size_t elf_file_size, char const* file_name) |
59f0d218 FF |
24 | { |
25 | if (sizeof(ElfSectionHeaderType) > elf_file_size) { | |
009c8d94 | 26 | 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); |
59f0d218 FF |
27 | return false; |
28 | } | |
29 | ElfHeaderType* elf_hdr = reinterpret_cast<ElfHeaderType*>(bytes); | |
30 | ||
31 | size_t last_section_header_byte = elf_hdr->e_shoff + sizeof(ElfSectionHeaderType) * elf_hdr->e_shnum; | |
32 | if (last_section_header_byte > elf_file_size) { | |
009c8d94 | 33 | 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); |
59f0d218 FF |
34 | return false; |
35 | } | |
36 | ElfSectionHeaderType* section_header_table = reinterpret_cast<ElfSectionHeaderType*>(bytes + elf_hdr->e_shoff); | |
37 | ||
38 | for (unsigned int i = 1; i < elf_hdr->e_shnum; i++) { | |
39 | ElfSectionHeaderType* section_header_entry = section_header_table + i; | |
40 | if (section_header_entry->sh_type == SHT_DYNAMIC) { | |
41 | size_t const last_dynamic_section_byte = section_header_entry->sh_offset + section_header_entry->sh_size; | |
42 | if (last_dynamic_section_byte > elf_file_size) { | |
009c8d94 | 43 | 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); |
59f0d218 FF |
44 | return false; |
45 | } | |
46 | ||
47 | size_t const dynamic_section_entries = section_header_entry->sh_size / sizeof(ElfDynamicSectionEntryType); | |
48 | ElfDynamicSectionEntryType* const dynamic_section = | |
49 | reinterpret_cast<ElfDynamicSectionEntryType*>(bytes + section_header_entry->sh_offset); | |
50 | ||
51 | unsigned int last_nonnull_entry_idx = 0; | |
52 | for (unsigned int j = dynamic_section_entries - 1; j > 0; j--) { | |
53 | ElfDynamicSectionEntryType* dynamic_section_entry = dynamic_section + j; | |
54 | if (dynamic_section_entry->d_tag != DT_NULL) { | |
55 | last_nonnull_entry_idx = j; | |
56 | break; | |
57 | } | |
58 | } | |
59 | ||
60 | for (unsigned int j = 0; j < dynamic_section_entries; j++) { | |
61 | ElfDynamicSectionEntryType* dynamic_section_entry = dynamic_section + j; | |
3ca4ba78 | 62 | char const* removed_name = nullptr; |
59f0d218 | 63 | switch (dynamic_section_entry->d_tag) { |
3ca4ba78 FF |
64 | case DT_VERNEEDED: removed_name = "DT_VERNEEDED"; break; |
65 | case DT_VERNEEDNUM: removed_name = "DT_VERNEEDNUM"; break; | |
637f22d1 FF |
66 | case DT_VERDEF: removed_name = "DT_VERDEF"; break; |
67 | case DT_VERDEFNUM: removed_name = "DT_VERDEFNUM"; break; | |
3ca4ba78 FF |
68 | case DT_RPATH: removed_name = "DT_RPATH"; break; |
69 | case DT_RUNPATH: removed_name = "DT_RUNPATH"; break; | |
70 | } | |
71 | if (removed_name != nullptr) { | |
009c8d94 | 72 | printf("termux-elf-cleaner: Removing the %s dynamic section entry from '%s'\n", removed_name, file_name); |
3ca4ba78 FF |
73 | // Tag the entry with DT_NULL and put it last: |
74 | dynamic_section_entry->d_tag = DT_NULL; | |
75 | // Decrease j to process new entry index: | |
76 | std::swap(dynamic_section[j--], dynamic_section[last_nonnull_entry_idx--]); | |
59f0d218 FF |
77 | } |
78 | } | |
79 | } | |
80 | } | |
81 | return true; | |
82 | } | |
83 | ||
84 | ||
009c8d94 | 85 | int main(int argc, char const** argv) |
59f0d218 FF |
86 | { |
87 | if (argc < 2 || (argc == 2 && strcmp(argv[1], "-h")==0)) { | |
88 | fprintf(stderr, "usage: %s <filename>\n", argv[0]); | |
89 | fprintf(stderr, " Processes ELF files to remove DT_VERNEEDED, DT_VERNEEDNUM, DT_RPATH\n" | |
90 | " and DT_RUNPATH entries (which the Android linker warns about)\n"); | |
91 | return 1; | |
92 | } | |
93 | ||
94 | for (int i = 1; i < argc; i++) { | |
009c8d94 FF |
95 | char const* file_name = argv[i]; |
96 | int fd = open(file_name, O_RDWR); | |
360e5c42 FF |
97 | if (fd < 0) { |
98 | char* error_message; | |
99 | if (asprintf(&error_message, "open(\"%s\")", file_name) == -1) error_message = (char*) "open()"; | |
100 | perror(error_message); | |
101 | return 1; | |
102 | } | |
59f0d218 FF |
103 | |
104 | struct stat st; | |
105 | if (fstat(fd, &st) < 0) { perror("fstat()"); return 1; } | |
106 | ||
360e5c42 FF |
107 | if (st.st_size < (long long) sizeof(Elf32_Ehdr)) { |
108 | close(fd); | |
109 | continue; | |
110 | } | |
59f0d218 FF |
111 | |
112 | void* mem = mmap(0, st.st_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); | |
113 | if (mem == MAP_FAILED) { perror("mmap()"); return 1; } | |
114 | ||
115 | uint8_t* bytes = reinterpret_cast<uint8_t*>(mem); | |
116 | if (!(bytes[0] == 0x7F && bytes[1] == 'E' && bytes[2] == 'L' && bytes[3] == 'F')) { | |
009c8d94 | 117 | // Not the ELF magic number. |
59f0d218 FF |
118 | munmap(mem, st.st_size); |
119 | close(fd); | |
120 | continue; | |
121 | } | |
122 | ||
009c8d94 FF |
123 | if (bytes[/*EI_DATA*/5] != 1) { |
124 | fprintf(stderr, "termux-elf-cleaner: Not little endianness in '%s'\n", file_name); | |
360e5c42 FF |
125 | munmap(mem, st.st_size); |
126 | close(fd); | |
009c8d94 FF |
127 | continue; |
128 | } | |
129 | ||
130 | uint8_t const bit_value = bytes[/*EI_CLASS*/4]; | |
131 | if (bit_value == 1) { | |
132 | if (!process_elf<Elf32_Ehdr, Elf32_Shdr, Elf32_Dyn>(bytes, st.st_size, file_name)) return 1; | |
133 | } else if (bit_value == 2) { | |
134 | if (!process_elf<Elf64_Ehdr, Elf64_Shdr, Elf64_Dyn>(bytes, st.st_size, file_name)) return 1; | |
59f0d218 | 135 | } else { |
009c8d94 FF |
136 | printf("termux-elf-cleaner: Incorrect bit value %d in '%s'\n", bit_value, file_name); |
137 | return 1; | |
59f0d218 FF |
138 | } |
139 | ||
140 | if (msync(mem, st.st_size, MS_SYNC) < 0) { perror("msync()"); return 1; } | |
141 | ||
142 | munmap(mem, st.st_size); | |
143 | close(fd); | |
144 | } | |
145 | return 0; | |
146 | } | |
147 |