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Commit 968908c3 authored by John Stultz's avatar John Stultz Committed by Greg Kroah-Hartman
Browse files

selftests: timers: Fix valid-adjtimex signed left-shift undefined behavior 



[ Upstream commit 076361362122a6d8a4c45f172ced5576b2d4a50d ]

The struct adjtimex freq field takes a signed value who's units are in
shifted (<<16) parts-per-million.

Unfortunately for negative adjustments, the straightforward use of:

  freq = ppm << 16 trips undefined behavior warnings with clang:

valid-adjtimex.c:66:6: warning: shifting a negative signed value is undefined [-Wshift-negative-value]
        -499<<16,
        ~~~~^
valid-adjtimex.c:67:6: warning: shifting a negative signed value is undefined [-Wshift-negative-value]
        -450<<16,
        ~~~~^
..

Fix it by using a multiply by (1 << 16) instead of shifting negative values
in the valid-adjtimex test case. Align the values for better readability.

Reported-by: default avatarLee Jones <joneslee@google.com>
Reported-by: default avatarMuhammad Usama Anjum <usama.anjum@collabora.com>
Signed-off-by: default avatarJohn Stultz <jstultz@google.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarMuhammad Usama Anjum <usama.anjum@collabora.com>
Link: https://lore.kernel.org/r/20240409202222.2830476-1-jstultz@google.com
Link: https://lore.kernel.org/lkml/0c6d4f0d-2064-4444-986b-1d1ed782135f@collabora.com/


Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 2c9cb7a5

tools/testing/selftests/timers/valid-adjtimex.c

+36 −37
Original line number Diff line number Diff line
@@ -21,9 +21,6 @@ 
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 *   GNU General Public License for more details.

 */







#include <stdio.h>

#include <stdlib.h>

#include <time.h>
@@ -62,45 +59,47 @@ int clear_time_state(void) 
#define NUM_FREQ_OUTOFRANGE 4

#define NUM_FREQ_INVALID 2



#define SHIFTED_PPM (1 << 16)



long valid_freq[NUM_FREQ_VALID] = {

	-499<<16,

	-450<<16,

	-400<<16,

	-350<<16,

	-300<<16,

	-250<<16,

	-200<<16,

	-150<<16,

	-100<<16,

	-75<<16,

	-50<<16,

	-25<<16,

	-10<<16,

	-5<<16,

	-1<<16,

	 -499 * SHIFTED_PPM,

	 -450 * SHIFTED_PPM,

	 -400 * SHIFTED_PPM,

	 -350 * SHIFTED_PPM,

	 -300 * SHIFTED_PPM,

	 -250 * SHIFTED_PPM,

	 -200 * SHIFTED_PPM,

	 -150 * SHIFTED_PPM,

	 -100 * SHIFTED_PPM,

	  -75 * SHIFTED_PPM,

	  -50 * SHIFTED_PPM,

	  -25 * SHIFTED_PPM,

	  -10 * SHIFTED_PPM,

	   -5 * SHIFTED_PPM,

	   -1 * SHIFTED_PPM,

	-1000,

	1<<16,

	5<<16,

	10<<16,

	25<<16,

	50<<16,

	75<<16,

	100<<16,

	150<<16,

	200<<16,

	250<<16,

	300<<16,

	350<<16,

	400<<16,

	450<<16,

	499<<16,

	    1 * SHIFTED_PPM,

	    5 * SHIFTED_PPM,

	   10 * SHIFTED_PPM,

	   25 * SHIFTED_PPM,

	   50 * SHIFTED_PPM,

	   75 * SHIFTED_PPM,

	  100 * SHIFTED_PPM,

	  150 * SHIFTED_PPM,

	  200 * SHIFTED_PPM,

	  250 * SHIFTED_PPM,

	  300 * SHIFTED_PPM,

	  350 * SHIFTED_PPM,

	  400 * SHIFTED_PPM,

	  450 * SHIFTED_PPM,

	  499 * SHIFTED_PPM,

};



long outofrange_freq[NUM_FREQ_OUTOFRANGE] = {

	-1000<<16,

	-550<<16,

	550<<16,

	1000<<16,

	-1000 * SHIFTED_PPM,

	 -550 * SHIFTED_PPM,

	  550 * SHIFTED_PPM,

	 1000 * SHIFTED_PPM,

};



#define LONG_MAX (~0UL>>1)