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Diffstat (limited to 'Documentation/prctl/disable-tsc-test.c')
-rw-r--r-- | Documentation/prctl/disable-tsc-test.c | 94 |
1 files changed, 94 insertions, 0 deletions
diff --git a/Documentation/prctl/disable-tsc-test.c b/Documentation/prctl/disable-tsc-test.c new file mode 100644 index 0000000..843c81e --- /dev/null +++ b/Documentation/prctl/disable-tsc-test.c @@ -0,0 +1,94 @@ +/* + * 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", +}; + +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_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); +} + |