리눅스 커널에서 스택의 값을 어떻게 바꾸나요?

void fn2()
{
    printf("                                      fn2\n");
}
 
void fn()
{
    printf("                       fn PREV \n");
    fn2();
    printf("                       fn NEXT \n");
}
 
 
 
int CALLBACK fnCallBack()
{
    return 2;
}
 
int __cdecl fnCdecl()
{
    return 3;
}
 
 
 
void (*pfn)();
 
int main(int argc, char** argv) 
{
    //함수가 호출될 때는 스택에 어떤 값을 저장할까?
    pfn = fn;
    printf("fn             %x\n", fn);
    printf("pfn            %x\n", pfn);
    printf("fnCallBack     %x\n", fnCallBack);
    printf("fnCdecl        %x\n", fnCdecl);
 
 
    //이때 스택에 저장되는 값을 변경
    printf("-------------\n");
//    *(int*)0x401529 = *(int*)pfn;
 
    printf("fn();\n");
    fn();
 
    printf("pfn            %x\n", pfn);
    printf("pfn = (void(*)())fn;\n");
    pfn = (void(*)())fn;
    printf("pfn();\n");
    pfn();
 
    printf("pfn            %x\n", pfn);
 
    printf("pfn = (void(*)())fn2;\n");
    pfn = (void(*)())fn2;
    printf("pfn();\n");
    pfn();
 
    printf("pfn            %x\n", pfn);
    printf("fn             %x\n", fn);
    printf("-------------\n");
 
 
	return 0;
}
 
 
 
 
출력 결과
 
fn             40153d
pfn            40153d
fnCallBack     401562
fnCdecl        40156c
-------------
fn();
                       fn PREV
                                      fn2
                       fn NEXT
pfn            40153d
pfn = (void(*)())fn;
pfn();
                       fn PREV
                                      fn2
                       fn NEXT
pfn            40153d
pfn = (void(*)())fn2;
pfn();
                                      fn2
pfn            401529
fn             40153d
-------------