linux-kernel - [PATCH 5.17 481/772] hwrng: cn10k

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Date:   Tue,  7 Jun 2022 19:01:13 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Vladis Dronov <vdronov@...hat.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.17 481/772] hwrng: cn10k - Optimize cn10k_rng_read()

From: Vladis Dronov <vdronov@...hat.com>

[ Upstream commit 753d6770879894de10d74b437ab99ea380f1cad7 ]

This function assumes that sizeof(void) is 1 and arithmetic works for
void pointers. This is a GNU C extention and may not work with other
compilers. Change this by using an u8 pointer.

Also move cn10k_read_trng() out of a loop thus saving some cycles.

Fixes: 38e9791a0209 ("hwrng: cn10k - Add random number generator support")
Signed-off-by: Vladis Dronov <vdronov@...hat.com>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/char/hw_random/cn10k-rng.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/char/hw_random/cn10k-rng.c b/drivers/char/hw_random/cn10k-rng.c
index 35001c63648b..dd226630b67d 100644
--- a/drivers/char/hw_random/cn10k-rng.c
+++ b/drivers/char/hw_random/cn10k-rng.c
@@ -90,6 +90,7 @@ static int cn10k_rng_read(struct hwrng *hwrng, void *data,
 {
 	struct cn10k_rng *rng = (struct cn10k_rng *)hwrng->priv;
 	unsigned int size;
+	u8 *pos = data;
 	int err = 0;
 	u64 value;
 
@@ -102,17 +103,20 @@ static int cn10k_rng_read(struct hwrng *hwrng, void *data,
 	while (size >= 8) {
 		cn10k_read_trng(rng, &value);
 
-		*((u64 *)data) = (u64)value;
+		*((u64 *)pos) = value;
 		size -= 8;
-		data += 8;
+		pos += 8;
 	}
 
-	while (size > 0) {
+	if (size > 0) {
 		cn10k_read_trng(rng, &value);
 
-		*((u8 *)data) = (u8)value;
-		size--;
-		data++;
+		while (size > 0) {
+			*pos = (u8)value;
+			value >>= 8;
+			size--;
+			pos++;
+		}
 	}
 
 	return max - size;
-- 
2.35.1