Monkey-Patching in C/C++ :-)

monkeypatchor.cpp

// compile me: g++ -shared -fPIC -ldl -o monkeypatchor.so monkeypatchor.cpp
// use me: LD_PRELOAD=`pwd`/monkeypatchor.so /bin/ls
#include <dlfcn.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>

void* (*malloc_super)(size_t);
void  (*free_super)(void*);

__attribute__((constructor))
void my_init() {
        printf("Monkey-patching into malloc() and free()\n");
        malloc_super = (void* (*)(size_t)) dlsym(RTLD_NEXT, "malloc");
        free_super = (void (*)(void*)) dlsym(RTLD_NEXT, "free");
}

void* malloc(size_t n) {
        void *result = malloc_super(n);
        if (result) {
                printf("Protected addr space: %p\n", result);
                mlock(result, n);
        }
        return result;
}

void free(void *p) {
        //munlock(p);
        free_super(p);
}

thanks! you're a life saver