%{
#include <linux/mm.h>
%}

global mypage

function change_name:long (filename:long) %{ /* pure */
    char *page = (char *)__get_free_page(GFP_KERNEL);
    page[0] = 't';
    page[1] = 't';
    page[2] = '\0';
    THIS->__retvalue = (long)page;
%}

# function change_name2:long (filename:long) %{ /* pure */
#     char *p = (char *)(long)THIS->filename;
#     p[0] = 't';
#     p[1] = 't';
#     p[2] = 0;
#     THIS->__retvalue = (long)p;
# %}

probe syscall.open {
    if (pid() == target()) {
	println("====================")
	println(argstr)
	if (($flags & 07) == 1 || ($flags & 07) == 2) {
	    change_flag = 1
	}

	mypage = 0
	if (change_flag == 1) {
	    # $filename = $filename + 0x1
	    # printf("%s\n", kernel_string($filename))
	    #print_backtrace()
	    print_regs()
	    printf("%p\n", $filename)
	    $filename = change_name($filename)
	    mypage = $filename
	    printf("%p\n", $filename)
	    println(kernel_string($filename))
	}
    }
}

function my_free_page (paddr:long) %{
    if (THIS->paddr) {
	free_page(THIS->paddr);
    }
%}

probe syscall.open.return {
    println(retstr)
    if (mypage) {
	printf("syscall open returns: %d\n", $return)
	my_free_page(mypage);
    }
    println("--------------------")
}