relro + dlopen

gistfile1.txt

laptop-dev-01[shawn]:/home/shawn/tmp $ cat dlopen.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <dlfcn.h>

int main(int argc, char *argv[])
{
        void *handle;

        if (argc < 3) {
                printf("USAGE: %s /path/to/lib symname\n", argv[0]);
                exit(1);
        }

        handle = dlopen(argv[1], RTLD_NOW | RTLD_GLOBAL);
        if (!(handle)) {
                fprintf(stderr, "%s\n", dlerror());
                exit(1);
        }

        printf("%s: %p\n", argv[2], dlsym(handle, argv[2]));

        dlclose(handle);

        return 0;
}
laptop-dev-01[shawn]:/home/shawn/tmp $ clang -Wl,-z,relro -Wl,-z,now -fPIE -pie -o dlopen dlopen.c
laptop-dev-01[shawn]:/home/shawn/tmp $ ./dlopen /lib/libthr.so.3 pthread_create
pthread_create: 0x4a7781dc080
laptop-dev-01[shawn]:/home/shawn/tmp $