The timespec_sub function, as implemented in several timer selftests, is prone to integer overflow on 32-bit systems.
The calculation `NSEC_PER_SEC * b.tv_sec` is performed using 32-bit arithmetic, and the result overflows before being stored in the 64-bit `ret` variable. This leads to incorrect time delta calculations and test failures.
As suggested by tglx, this patch fixes the issue by:
1. Creating a new `static inline` helper function, `timespec_to_ns`, which safely converts a `timespec` to nanoseconds by casting `tv_sec` to `long long` before multiplying with `NSEC_PER_SEC`.
2. Placing the new helper and a rewritten `timespec_sub` into a common header: tools/testing/selftests/timers/helpers.h.
3. Removing the duplicated, buggy implementations from all timer selftests and replacing them with an #include of the new header.
This consolidates the code and ensures the calculation is correctly performed using 64-bit arithmetic across all tests.
Changes in v2: - Per tglx's feedback, instead of changing NSEC_PER_SEC globally, this version consolidates the buggy timespec_sub() implementations into a new 32-bit safe inline function in a shared header. - Amended the commit message to be more descriptive. --- .../selftests/timers/alarmtimer-suspend.c | 15 +++------ tools/testing/selftests/timers/helpers.h | 31 +++++++++++++++++++ tools/testing/selftests/timers/nanosleep.c | 2 +- tools/testing/selftests/timers/nsleep-lat.c | 12 ++----- .../testing/selftests/timers/valid-adjtimex.c | 8 ++--- 5 files changed, 43 insertions(+), 25 deletions(-) create mode 100644 tools/testing/selftests/timers/helpers.h
diff --git a/tools/testing/selftests/timers/alarmtimer-suspend.c b/tools/testing/selftests/timers/alarmtimer-suspend.c index a9ef76ea6051..e85ab182abe5 100644 --- a/tools/testing/selftests/timers/alarmtimer-suspend.c +++ b/tools/testing/selftests/timers/alarmtimer-suspend.c @@ -31,8 +31,9 @@ #include <include/vdso/time64.h> #include <errno.h> #include "../kselftest.h" +#include "helpers.h"
-#define UNREASONABLE_LAT (NSEC_PER_SEC * 5) /* hopefully we resume in 5 secs */ +#define UNREASONABLE_LAT (NSEC_PER_SEC * 5LL) /* hopefully we resume in 5 secs */
#define SUSPEND_SECS 15 int alarmcount; @@ -70,14 +71,6 @@ char *clockstring(int clockid) }
-long long timespec_sub(struct timespec a, struct timespec b) -{ - long long ret = NSEC_PER_SEC * b.tv_sec + b.tv_nsec; - - ret -= NSEC_PER_SEC * a.tv_sec + a.tv_nsec; - return ret; -} - int final_ret;
void sigalarm(int signo) @@ -88,8 +81,8 @@ void sigalarm(int signo) clock_gettime(alarm_clock_id, &ts); alarmcount++;
- delta_ns = timespec_sub(start_time, ts); - delta_ns -= NSEC_PER_SEC * SUSPEND_SECS * alarmcount; + delta_ns = timespec_sub(ts, start_time); + delta_ns -= (long long)NSEC_PER_SEC * SUSPEND_SECS * alarmcount;
printf("ALARM(%i): %ld:%ld latency: %lld ns ", alarmcount, ts.tv_sec, ts.tv_nsec, delta_ns); diff --git a/tools/testing/selftests/timers/helpers.h b/tools/testing/selftests/timers/helpers.h new file mode 100644 index 000000000000..652f20247091 --- /dev/null +++ b/tools/testing/selftests/timers/helpers.h @@ -0,0 +1,31 @@ +#ifndef SELFTESTS_TIMERS_HELPERS_H +#define SELFTESTS_TIMERS_HELPERS_H + +#include <time.h> + +#ifndef NSEC_PER_SEC +#define NSEC_PER_SEC 1000000000L +#endif + +/* + * timespec_to_ns - Convert timespec to nanoseconds + */ +static inline long long timespec_to_ns(const struct timespec *ts) +{ + return ((long long) ts->tv_sec * NSEC_PER_SEC) + ts->tv_nsec; +} + +/* + * timespec_sub - Subtract two timespec values + * + * @a: first timespec + * @b: second timespec + * + * Returns a - b in nanoseconds. + */ +static inline long long timespec_sub(struct timespec a, struct timespec b) +{ + return timespec_to_ns(&a) - timespec_to_ns(&b); +} + +#endif /* SELFTESTS_TIMERS_HELPERS_H */ diff --git a/tools/testing/selftests/timers/nanosleep.c b/tools/testing/selftests/timers/nanosleep.c index 252c6308c569..41c33629d5f0 100644 --- a/tools/testing/selftests/timers/nanosleep.c +++ b/tools/testing/selftests/timers/nanosleep.c @@ -138,7 +138,7 @@ int main(int argc, char **argv) fflush(stdout);
length = 10; - while (length <= (NSEC_PER_SEC * 10)) { + while (length <= (NSEC_PER_SEC * 10LL)) { ret = nanosleep_test(clockid, length); if (ret == UNSUPPORTED) { ksft_test_result_skip("%-31s\n", clockstring(clockid)); diff --git a/tools/testing/selftests/timers/nsleep-lat.c b/tools/testing/selftests/timers/nsleep-lat.c index de23dc0c9f97..c888a77aab7a 100644 --- a/tools/testing/selftests/timers/nsleep-lat.c +++ b/tools/testing/selftests/timers/nsleep-lat.c @@ -26,6 +26,7 @@ #include <signal.h> #include <include/vdso/time64.h> #include "../kselftest.h" +#include "helpers.h"
#define UNRESONABLE_LATENCY 40000000 /* 40ms in nanosecs */
@@ -74,14 +75,6 @@ struct timespec timespec_add(struct timespec ts, unsigned long long ns) }
-long long timespec_sub(struct timespec a, struct timespec b) -{ - long long ret = NSEC_PER_SEC * b.tv_sec + b.tv_nsec; - - ret -= NSEC_PER_SEC * a.tv_sec + a.tv_nsec; - return ret; -} - int nanosleep_lat_test(int clockid, long long ns) { struct timespec start, end, target; @@ -146,7 +139,7 @@ int main(int argc, char **argv) continue;
length = 10; - while (length <= (NSEC_PER_SEC * 10)) { + while (length <= (NSEC_PER_SEC * 10LL)) { ret = nanosleep_lat_test(clockid, length); if (ret) break; @@ -164,3 +157,4 @@ int main(int argc, char **argv)
ksft_finished(); } + diff --git a/tools/testing/selftests/timers/valid-adjtimex.c b/tools/testing/selftests/timers/valid-adjtimex.c index 6b7801055ad1..a61d4b4739a2 100644 --- a/tools/testing/selftests/timers/valid-adjtimex.c +++ b/tools/testing/selftests/timers/valid-adjtimex.c @@ -260,16 +260,16 @@ int validate_set_offset(void) if (set_offset(-NSEC_PER_SEC - 1, 1)) return -1;
- if (set_offset(5 * NSEC_PER_SEC, 1)) + if (set_offset(5LL * NSEC_PER_SEC, 1)) return -1;
- if (set_offset(-5 * NSEC_PER_SEC, 1)) + if (set_offset(-5LL * NSEC_PER_SEC, 1)) return -1;
- if (set_offset(5 * NSEC_PER_SEC + NSEC_PER_SEC / 2, 1)) + if (set_offset(5LL * NSEC_PER_SEC + NSEC_PER_SEC / 2, 1)) return -1;
- if (set_offset(-5 * NSEC_PER_SEC - NSEC_PER_SEC / 2, 1)) + if (set_offset(-5LL * NSEC_PER_SEC - NSEC_PER_SEC / 2, 1)) return -1;
if (set_offset(USEC_PER_SEC - 1, 0))