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Make the executable file can be loaded by dlopen() after glibc>=2.30.
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| /* There is a behavior change in glibc>=2.30. dlopen() will fail if the file is position independent executable. | |
| This tool will clean up the PIE flag in the file to bypass the dlopen() check. | |
| */ | |
| #include <stdio.h> | |
| #include <string.h> | |
| #include <elf.h> | |
| #define EXEC(x, err_msg) \ | |
| if (!(x)) { \ | |
| perror(err_msg); \ | |
| err = -1; \ | |
| goto ex; \ | |
| } | |
| int main(int argc, char* argv[]) { | |
| int err = 0; | |
| if (argc != 2) { | |
| printf("Usage: mkexeloadable <executable-elf64-file>\n"); | |
| return -1; | |
| } | |
| FILE* fp = fopen(argv[1], "r+b"); | |
| EXEC(fp != NULL, "Can't open file"); | |
| // Read elf header. | |
| Elf64_Ehdr elf_header; | |
| EXEC(fread(&elf_header, sizeof(elf_header), 1, fp) == 1, "Read elf64_ehdr failed"); | |
| // Is it a elf64 file? | |
| EXEC(strncmp((char*)elf_header.e_ident, "\177ELF\002", 5) == 0, "It is not a valid elf64 file"); | |
| // Find out dynamic section | |
| Elf64_Shdr section_header; | |
| Elf64_Dyn dyn; | |
| EXEC(fseek(fp, elf_header.e_shoff, SEEK_SET) == 0, "Seek file failed"); | |
| for (int i = 0; i < elf_header.e_shnum; ++i) { | |
| EXEC(fread(§ion_header, elf_header.e_shentsize, 1, fp) == 1, "Read section header failed"); | |
| if (section_header.sh_type == SHT_DYNAMIC) { | |
| EXEC(fseek(fp, section_header.sh_offset, SEEK_SET) == 0, "Seek file failed"); | |
| while (1) { | |
| EXEC(fread(&dyn, sizeof(Elf64_Dyn), 1, fp) == 1, "Read section entry failed"); | |
| EXEC(dyn.d_tag != 0, "Can't find flags_1"); | |
| if (dyn.d_tag == 0x6ffffffb) { | |
| // Clear PIE flag. | |
| dyn.d_un.d_val &= ~DF_1_PIE; | |
| EXEC(fseek(fp, -sizeof(Elf64_Dyn), SEEK_CUR) == 0, "Seek flags_1 failed"); | |
| EXEC(fwrite(&dyn, sizeof(Elf64_Dyn), 1, fp) == 1, "Write back flags_1 failed"); | |
| // Success! | |
| goto ex; | |
| } | |
| } | |
| } | |
| } | |
| // Can't find required flags, something might be wrong. | |
| EXEC(0, "Can't find required flags"); | |
| ex: | |
| if (fp) { | |
| fclose(fp); | |
| } | |
| return err; | |
| } |
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