dlopen from memory?

Question

I\'m looking for a way to load generated object code directly from memory.

I understand that if I write it to a file, I can call dlopen to dynamically load its symbo

Answer 1

I needed a solution to this because I have a scriptable system that has no filesystem (using blobs from a database) and needs to load binary plugins to support some scripts. This is the solution I came up with which works on FreeBSD but may not be portable.

void *dlblob(const void *blob, size_t len) {
    /* Create shared-memory file descriptor */
    int fd = shm_open(SHM_ANON, O_RDWR, 0);
    ftruncate(fd, len);
    /* MemMap file descriptor, and load data */
    void *mem = mmap(NULL, len, PROT_WRITE, MAP_SHARED, fd, 0);
    memcpy(mem, blob, len);
    munmap(mem, len);
    /* Open Dynamic Library from SHM file descriptor */
    void *so = fdlopen(fd,RTLD_LAZY);
    close(fd);
    return so;
}

Obviously the code lacks any kind of error checking etc, but this is the core functionality.

ETA: My initial assumption that fdlopen is POSIX was wrong, this appears to be a FreeBSD-ism.