2011-9-28 Linux antidebug 5

Content: When debuging programm line by line or when running it
in some debugger then ther can be some time delays when you
pressing buttons. We can measure them with asm command

rdtsc 

this instruction read time-stamp counter into edx:eax in our
programm will be enought values from
eax

function for c that uses rdtsc is

extern int get_timer()

in fasm it looks like

get_timer:
	rdtsc
	ret

ther is writen code

s = get_timer();
for (i=0;i<10000;i++)
{
}
e = get_timer();
d = e - s;

average time to execute 10000 is 70069 ticks for value
on with we detecting how fast working code i have choose
twice of average 120000 if execution time is larger then
probably it is debuged.

Compile

make