Function copy_and_patch_runtime

src/binfmt-bypass/main.cpp:18–36

#define EXIT_CODE_FAILURE 0xff

bool copy_and_patch_runtime(int fd, const char* const appimage_filename, const ssize_t elf_size) {
    // copy runtime header into memfd "file"
    {
        const auto realfd = open(appimage_filename, O_RDONLY);
        std::vector<char> buffer(elf_size);
        // TODO: check for errors
        read(realfd, buffer.data(), elf_size);
        write(fd, buffer.data(), elf_size);
        close(realfd);
    }

    // erase magic bytes
    lseek(fd, 8, SEEK_SET);
    char null_buf[]{0, 0, 0};
    write(fd, null_buf, 3);

    // TODO: handle errors properly
    return true;
}

#ifdef HAVE_MEMFD_CREATE