linux hook demo

#include                                                                                                                                   
#include 
#include  
#include 
#include 

void *orignal_=0;
unsigned char orignal_text_[12];
int orignal_page_;
int pagesize_;

void set(void *orignal, void * mock_func) {
    int ret;
    pagesize_ = sysconf(_SC_PAGE_SIZE);
    orignal_page_ = reinterpret_cast(orignal) / pagesize_;
    orignal_page_ *= pagesize_;

    unsigned char machine_code[] = { 0x48, 0xb8, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,0xff, 0xe0 };

    ret = mprotect(reinterpret_cast(orignal_page_), pagesize_, PROT_READ | PROT_WRITE | PROT_EXEC);
    if (ret < 0) {
        printf("mproterct error");
        return;
    }   
    if (0 == orignal_) {
        memcpy(orignal_text_, orignal, sizeof(orignal_text_));
    }   
    memcpy(machine_code + 2, &mock_func, sizeof(mock_func));
    memcpy(orignal, machine_code, sizeof(machine_code));

    mprotect(reinterpret_cast(orignal_page_), pagesize_, PROT_READ | PROT_EXEC);
    orignal_ = orignal;
}
void clear() {
    if (0 != orignal_) {
        int ret;
        ret = mprotect(reinterpret_cast(orignal_page_), pagesize_, PROT_READ | PROT_WRITE | PROT_EXEC);
        if (ret < 0) {
            printf("mproterct error");
            return;
        }   
        memcpy(orignal_, orignal_text_, sizeof(orignal_text_));
        mprotect(reinterpret_cast(orignal_page_), pagesize_, PROT_READ | PROT_EXEC);
        orignal_ = 0;
    }   
}
void original(int a,int b){ 
    int c = a+b; 
    c=c*100;
    printf("original out:%d\n",c);
}
void newfunc(int a,int b){
    int c = a-b;
    printf("newfunc out:%d\n",c);
}
int main()
{
    set((void*)original,(void*)newfunc);
    original(1,2);
    return 0;
}