unfuck.c

#include <fcntl.h>
#include <gelf.h>
#include <libelf.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>

#include <fcntl.h>
#include <gelf.h>
#include <libelf.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>

void
printProgramHeaderInfo(Elf* elf)
{
    Elf64_Ehdr* ehdr = elf64_getehdr(elf);
    if (!ehdr) {
        fprintf(stderr, "elf64_getehdr() failed: %s\n", elf_errmsg(-1));
        exit(EXIT_FAILURE);
    }

    for (size_t i = 0; i < ehdr->e_phnum; ++i) {
        GElf_Phdr phdr;
        if (gelf_getphdr(elf, i, &phdr) != &phdr) {
            fprintf(stderr, "gelf_getphdr() failed: %s\n", elf_errmsg(-1));
            exit(EXIT_FAILURE);
        }

        printf("Program Header %zu - Type: %lu, Alignment: %lu\n", i, phdr.p_type, phdr.p_align);
    }
}

void
modifyElfAlignment(const char* filename)
{
    int fd, elferr;

    if (elf_version(EV_CURRENT) == EV_NONE) {
        fprintf(stderr, "ELF library initialization failed: %s\n", elf_errmsg(-1));
        exit(EXIT_FAILURE);
    }

    if ((fd = open(filename, O_RDWR)) == -1) {
        perror("open");
        exit(EXIT_FAILURE);
    }

    struct stat st;
    if (fstat(fd, &st) == -1) {
        perror("fstat");
        exit(EXIT_FAILURE);
    }

    Elf* elf;
    if ((elf = elf_begin(fd, ELF_C_RDWR_MMAP, NULL)) == NULL) {
        fprintf(stderr, "elf_begin() failed: %s\n", elf_errmsg(-1));
        exit(EXIT_FAILURE);
    }

    printf("Program Headers before modification:\n");
    printProgramHeaderInfo(elf);

    Elf64_Ehdr* ehdr = elf64_getehdr(elf);
    if (!ehdr) {
        fprintf(stderr, "elf64_getehdr() failed: %s\n", elf_errmsg(-1));
        exit(EXIT_FAILURE);
    }

    for (size_t i = 0; i < ehdr->e_phnum; ++i) {
        GElf_Phdr phdr;
        if (gelf_getphdr(elf, i, &phdr) != &phdr) {
            fprintf(stderr, "gelf_getphdr() failed: %s\n", elf_errmsg(-1));
            exit(EXIT_FAILURE);
        }

        if (phdr.p_filesz == 0 && phdr.p_memsz == 0 && phdr.p_type == PT_LOAD) {
            printf("Modifying Alignment of Program Header %zu\n", i);
            phdr.p_align = 0;
            phdr.p_type = PT_NULL;

            if (gelf_update_phdr(elf, i, &phdr) == 0) {
                fprintf(stderr, "gelf_update_phdr() failed: %s\n", elf_errmsg(-1));
                exit(EXIT_FAILURE);
            }
        }
    }

    printf("\nProgram Headers after modification:\n");
    printProgramHeaderInfo(elf);
    close(fd);
}

int
main(int argc, char* argv[])
{
    if (argc != 2) {
        fprintf(stderr, "Usage: %s <elf_filename>\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    modifyElfAlignment(argv[1]);

    return 0;
}