linux-kernel - [PATCH] x86: tsc: use div64_u64() instead of do

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Date:   Wed,  9 Feb 2022 00:35:13 -0800
From:   Qing Wang <wangqing@...o.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        linux-kernel@...r.kernel.org
Cc:     Wang Qing <wangqing@...o.com>
Subject: [PATCH] x86: tsc: use div64_u64() instead of do_div()

From: Wang Qing <wangqing@...o.com>

do_div() does a 64-by-32 division.
When the divisor is u64, do_div() truncates it to 32 bits, this means it
can test non-zero and be truncated to zero for division.

fix do_div.cocci warning:
do_div() does a 64-by-32 division, please consider using div64_u64 instead.

Signed-off-by: Wang Qing <wangqing@...o.com>
---
 arch/x86/kernel/tsc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index a698196..e97124c
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -365,7 +365,7 @@ static unsigned long calc_pmtimer_ref(u64 deltatsc, u64 pm1, u64 pm2)
 	pm2 -= pm1;
 	tmp = pm2 * 1000000000LL;
 	do_div(tmp, PMTMR_TICKS_PER_SEC);
-	do_div(deltatsc, tmp);
+	div64_u64(deltatsc, tmp);
 
 	return (unsigned long) deltatsc;
 }
-- 
2.7.4