Under Linux kernel 2.6.35, getting current time(accuracy macrosenconds).

Kernel API function prototype:

#include 
struct timeval {
	__kernel_time_t		tv_sec;		/* seconds */
	__kernel_suseconds_t	tv_usec;	/* microseconds */
};
do_gettimeofday(struct timeval *tv)

Code:

unsigned long timeuse;
struct timeval tv_start, tv_end;
do_gettimeofday(&tv_start);   
/* do something */
do_gettimeofday(&tv_end);

timeuse = (tv_end.tv_sec - tv_start.tv_sec) * 1000;
timeuse += (tv_end.tv_usec - tv_start.tv_usec) / 1000;

pr_debug("timeuse: %lu ms\n", timeuse);