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Diffstat (limited to 'Documentation/prctl/disable-tsc-test.c')
-rw-r--r--Documentation/prctl/disable-tsc-test.c95
1 files changed, 95 insertions, 0 deletions
diff --git a/Documentation/prctl/disable-tsc-test.c b/Documentation/prctl/disable-tsc-test.c
new file mode 100644
index 000000000..2541e65cb
--- /dev/null
+++ b/Documentation/prctl/disable-tsc-test.c
@@ -0,0 +1,95 @@
+/*
+ * Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...)
+ *
+ * Basic test to test behaviour of PR_GET_TSC and PR_SET_TSC
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <signal.h>
+#include <inttypes.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
+
+const char *tsc_names[] =
+{
+ [0] = "[not set]",
+ [PR_TSC_ENABLE] = "PR_TSC_ENABLE",
+ [PR_TSC_SIGSEGV] = "PR_TSC_SIGSEGV",
+};
+
+static uint64_t rdtsc(void)
+{
+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;
+}
+
+static void sigsegv_cb(int sig)
+{
+ int tsc_val = 0;
+
+ printf("[ SIG_SEGV ]\n");
+ printf("prctl(PR_GET_TSC, &tsc_val); ");
+ fflush(stdout);
+
+ if ( prctl(PR_GET_TSC, &tsc_val) == -1)
+ perror("prctl");
+
+ printf("tsc_val == %s\n", tsc_names[tsc_val]);
+ printf("prctl(PR_SET_TSC, PR_TSC_ENABLE)\n");
+ fflush(stdout);
+ if ( prctl(PR_SET_TSC, PR_TSC_ENABLE) == -1)
+ perror("prctl");
+
+ printf("rdtsc() == ");
+}
+
+int main(int argc, char **argv)
+{
+ int tsc_val = 0;
+
+ signal(SIGSEGV, sigsegv_cb);
+
+ printf("rdtsc() == %llu\n", (unsigned long long)rdtsc());
+ printf("prctl(PR_GET_TSC, &tsc_val); ");
+ fflush(stdout);
+
+ if ( prctl(PR_GET_TSC, &tsc_val) == -1)
+ perror("prctl");
+
+ printf("tsc_val == %s\n", tsc_names[tsc_val]);
+ printf("rdtsc() == %llu\n", (unsigned long long)rdtsc());
+ printf("prctl(PR_SET_TSC, PR_TSC_ENABLE)\n");
+ fflush(stdout);
+
+ if ( prctl(PR_SET_TSC, PR_TSC_ENABLE) == -1)
+ perror("prctl");
+
+ printf("rdtsc() == %llu\n", (unsigned long long)rdtsc());
+ printf("prctl(PR_SET_TSC, PR_TSC_SIGSEGV)\n");
+ fflush(stdout);
+
+ if ( prctl(PR_SET_TSC, PR_TSC_SIGSEGV) == -1)
+ perror("prctl");
+
+ printf("rdtsc() == ");
+ fflush(stdout);
+ printf("%llu\n", (unsigned long long)rdtsc());
+ fflush(stdout);
+
+ exit(EXIT_SUCCESS);
+}
+