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Date: Tue,  9 Apr 2024 13:22:12 -0700
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Message-ID: <20240409202222.2830476-1-jstultz@google.com>
Subject: [PATCH] selftests: timers: Fix valid-adjtimex signed left-shift
 undefined behavior
From: John Stultz <jstultz@google.com>
To: LKML <linux-kernel@vger.kernel.org>
Cc: John Stultz <jstultz@google.com>, Thomas Gleixner <tglx@linutronix.de>, 
	Stephen Boyd <sboyd@kernel.org>, Anna-Maria Behnsen <anna-maria@linutronix.de>, 
	Frederic Weisbecker <frederic@kernel.org>, Shuah Khan <shuah@kernel.org>, 
	Nathan Chancellor <nathan@kernel.org>, Nick Desaulniers <ndesaulniers@google.com>, 
	Lee Jones <joneslee@google.com>, Muhammad Usama Anjum <usama.anjum@collabora.com>, 
	linux-kselftest@vger.kernel.org
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So, 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
will trip 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,
        ~~~~^
..

So fix our use of shifting negative values in the valid-adjtimex
test case to use multiply by (1<<16) to avoid this.

The patch also aligns the values a bit to make it look nicer.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Anna-Maria Behnsen <anna-maria@linutronix.de>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Lee Jones <joneslee@google.com>
Cc: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: linux-kselftest@vger.kernel.org
Reported-by: Lee Jones <joneslee@google.com>
Reported-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Link: https://lore.kernel.org/lkml/0c6d4f0d-2064-4444-986b-1d1ed782135f@collabora.com/
Signed-off-by: John Stultz <jstultz@google.com>
---
 .../testing/selftests/timers/valid-adjtimex.c | 69 ++++++++++---------
 1 file changed, 35 insertions(+), 34 deletions(-)

diff --git a/tools/testing/selftests/timers/valid-adjtimex.c b/tools/testing/selftests/timers/valid-adjtimex.c
index 48b9a803235a..9606d45767e7 100644
--- a/tools/testing/selftests/timers/valid-adjtimex.c
+++ b/tools/testing/selftests/timers/valid-adjtimex.c
@@ -62,45 +62,46 @@ 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)
-- 
2.44.0.478.gd926399ef9-goog