Documentation / prctl / disable-tsc-ctxt-sw-stress-test.c

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Based on kernel version 3.9. Page generated on 2013-05-02 23:12 EST.

	/*
	 * Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...)
	 *
	 * Tests if the control register is updated correctly
	 * at context switches
	 *
	 * Warning: this test will cause a very high load for a few seconds
	 *
	 */
	
	#include <stdio.h>
	#include <stdlib.h>
	#include <unistd.h>
	#include <signal.h>
	#include <inttypes.h>
	#include <wait.h>
	
	
	#include <sys/prctl.h>
	#include <linux/prctl.h>
	
	/* Get/set the process' ability to use the timestamp counter instruction */
	#ifndef PR_GET_TSC
	#define PR_GET_TSC 25
	#define PR_SET_TSC 26
	# define PR_TSC_ENABLE		1   /* allow the use of the timestamp counter */
	# define PR_TSC_SIGSEGV		2   /* throw a SIGSEGV instead of reading the TSC */
	#endif
	
	uint64_t rdtsc() {
	uint32_t lo, hi;
	/* We cannot use "=A", since this would use %rax on x86_64 */
	__asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
	return (uint64_t)hi << 32 | lo;
	}
	
	void sigsegv_expect(int sig)
	{
		/* */
	}
	
	void segvtask(void)
	{
		if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0)
		{
			perror("prctl");
			exit(0);
		}
		signal(SIGSEGV, sigsegv_expect);
		alarm(10);
		rdtsc();
		fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n");
		exit(0);
	}
	
	
	void sigsegv_fail(int sig)
	{
		fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n");
		exit(0);
	}
	
	void rdtsctask(void)
	{
		if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0)
		{
			perror("prctl");
			exit(0);
		}
		signal(SIGSEGV, sigsegv_fail);
		alarm(10);
		for(;;) rdtsc();
	}
	
	
	int main(int argc, char **argv)
	{
		int n_tasks = 100, i;
	
		fprintf(stderr, "[No further output means we're allright]\n");
	
		for (i=0; i<n_tasks; i++)
			if (fork() == 0)
			{
				if (i & 1)
					segvtask();
				else
					rdtsctask();
			}
	
		for (i=0; i<n_tasks; i++)
			wait(NULL);
	
		exit(0);
	}

• [ prctl ]
• disable-tsc-ctxt-sw-stress-test.c
• disable-tsc-on-off-stress-test.c
• disable-tsc-test.c
• no_new_privs.txt
• seccomp_filter.txt
•