/* TODO:
 *   notify gdb of unload
 *   for non-prelinked libraries, find a way to decrement libbase
 */
static void call_destructors(soinfo *si);
unsigned unload_library(soinfo *si)
{
    unsigned *d;
    if (si->refcount == 1) {
        TRACE("%5d unloading '%s'\n", pid, si->name);
        call_destructors(si);

        /*
         * Make sure that we undo the PT_GNU_RELRO protections we added
         * in link_image. This is needed to undo the DT_NEEDED hack below.
         */
        if ((si->gnu_relro_start != 0) && (si->gnu_relro_len != 0)) {
            Elf_Addr start = (si->gnu_relro_start & ~PAGE_MASK);
            unsigned len = (si->gnu_relro_start - start) + si->gnu_relro_len;
            if (mprotect((void *) start, len, PROT_READ | PROT_WRITE) < 0)
                DL_ERR("%5d %s: could not undo GNU_RELRO protections. "
                       "Expect a crash soon. errno=%d (%s)",
                       pid, si->name, errno, strerror(errno));

        }

        for(d = si->dynamic; *d; d += 2) {
            if(d[0] == DT_NEEDED){
                soinfo *lsi = (soinfo *)d[1];

                // The next line will segfault if the we don't undo the
                // PT_GNU_RELRO protections (see comments above and in
                // link_image().
                d[1] = 0;

                if (validate_soinfo(lsi)) {
                    TRACE("%5d %s needs to unload %s\n", pid,
                          si->name, lsi->name);
                    unload_library(lsi);
                }
                else
                    DL_ERR("%5d %s: could not unload dependent library",
                           pid, si->name);
            }
        }

        munmap((char *)si->base, si->size);
        notify_gdb_of_unload(si);
        free_info(si);
        si->refcount = 0;
    }
    else {
        si->refcount--;
        INFO("%5d not unloading '%s', decrementing refcount to %d\n",
              pid, si->name, si->refcount);
    }
    return si->refcount;
}