Function xh_elf_replace_function

Bcore/src/main/cpp/xhook/xh_elf.c:448–497

}

static int xh_elf_replace_function(xh_elf_t *self, const char *symbol, ElfW(Addr) addr, void *new_func, void **old_func)
{
    void         *old_addr;
    unsigned int  old_prot = 0;
    unsigned int  need_prot = PROT_READ | PROT_WRITE;
    int           r;

    //already replaced?
    //here we assume that we always have read permission, is this a problem?
    if(*(void **)addr == new_func) return 0;

    //get old prot
    if(0 != (r = xh_util_get_addr_protect(addr, self->pathname, &old_prot)))
    {
        XH_LOG_ERROR("get addr prot failed. ret: %d", r);
        return r;
    }
    
    if(old_prot != need_prot)
    {
        //set new prot
        if(0 != (r = xh_util_set_addr_protect(addr, need_prot)))
        {
            XH_LOG_ERROR("set addr prot failed. ret: %d", r);
            return r;
        }
    }
    
    //save old func
    old_addr = *(void **)addr;
    if(NULL != old_func) *old_func = old_addr;

    //replace func
    *(void **)addr = new_func; //segmentation fault sometimes

    if(old_prot != need_prot)
    {
        //restore the old prot
        if(0 != (r = xh_util_set_addr_protect(addr, old_prot)))
        {
            XH_LOG_WARN("restore addr prot failed. ret: %d", r);
        }
    }
    
    //clear cache
    xh_util_flush_instruction_cache(addr);

    XH_LOG_INFO("XH_HK_OK %p: %p -> %p %s %s\n", (void *)addr, old_addr, new_func, symbol, self->pathname);
    return 0;
}

static int xh_elf_check(xh_elf_t *self)
{