linux-kernel - [PATCH] hwmon: occ: fix unaligned accesses

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Message-Id: <20250610092553.2641094-1-arnd@kernel.org>
Date: Tue, 10 Jun 2025 11:25:49 +0200
From: Arnd Bergmann <arnd@...nel.org>
To: Jean Delvare <jdelvare@...e.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Eddie James <eajames@...ux.vnet.ibm.com>
Cc: Arnd Bergmann <arnd@...db.de>,
	Al Viro <viro@...iv.linux.org.uk>,
	linux-hwmon@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] hwmon: occ: fix unaligned accesses

From: Arnd Bergmann <arnd@...db.de>

Passing a pointer to an unaligned integer as a function argument is
undefined behavior:

drivers/hwmon/occ/common.c:492:27: warning: taking address of packed member 'accumulator' of class or structure 'power_sensor_2' may result in an unaligned pointer value [-Waddress-of-packed-member]
  492 |   val = occ_get_powr_avg(&power->accumulator,
      |                           ^~~~~~~~~~~~~~~~~~
drivers/hwmon/occ/common.c:493:13: warning: taking address of packed member 'update_tag' of class or structure 'power_sensor_2' may result in an unaligned pointer value [-Waddress-of-packed-member]
  493 |            &power->update_tag);
      |             ^~~~~~~~~~~~~~~~~

Move the get_unaligned() calls out of the function and pass these
through argument registers instead.

Fixes: c10e753d43eb ("hwmon (occ): Add sensor types and versions")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/hwmon/occ/common.c | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/drivers/hwmon/occ/common.c b/drivers/hwmon/occ/common.c
index 9029ad53790b..b3694a4209b9 100644
--- a/drivers/hwmon/occ/common.c
+++ b/drivers/hwmon/occ/common.c
@@ -459,12 +459,10 @@ static ssize_t occ_show_power_1(struct device *dev,
 	return sysfs_emit(buf, "%llu\n", val);
 }
 
-static u64 occ_get_powr_avg(u64 *accum, u32 *samples)
+static u64 occ_get_powr_avg(u64 accum, u32 samples)
 {
-	u64 divisor = get_unaligned_be32(samples);
-
-	return (divisor == 0) ? 0 :
-		div64_u64(get_unaligned_be64(accum) * 1000000ULL, divisor);
+	return (samples == 0) ? 0 :
+		mul_u64_u32_div(accum, 1000000UL, samples);
 }
 
 static ssize_t occ_show_power_2(struct device *dev,
@@ -489,8 +487,8 @@ static ssize_t occ_show_power_2(struct device *dev,
 				  get_unaligned_be32(&power->sensor_id),
 				  power->function_id, power->apss_channel);
 	case 1:
-		val = occ_get_powr_avg(&power->accumulator,
-				       &power->update_tag);
+		val = occ_get_powr_avg(get_unaligned_be64(&power->accumulator),
+				       get_unaligned_be32(&power->update_tag));
 		break;
 	case 2:
 		val = (u64)get_unaligned_be32(&power->update_tag) *
@@ -527,8 +525,8 @@ static ssize_t occ_show_power_a0(struct device *dev,
 		return sysfs_emit(buf, "%u_system\n",
 				  get_unaligned_be32(&power->sensor_id));
 	case 1:
-		val = occ_get_powr_avg(&power->system.accumulator,
-				       &power->system.update_tag);
+		val = occ_get_powr_avg(get_unaligned_be64(&power->system.accumulator),
+				       get_unaligned_be32(&power->system.update_tag));
 		break;
 	case 2:
 		val = (u64)get_unaligned_be32(&power->system.update_tag) *
@@ -541,8 +539,8 @@ static ssize_t occ_show_power_a0(struct device *dev,
 		return sysfs_emit(buf, "%u_proc\n",
 				  get_unaligned_be32(&power->sensor_id));
 	case 5:
-		val = occ_get_powr_avg(&power->proc.accumulator,
-				       &power->proc.update_tag);
+		val = occ_get_powr_avg(get_unaligned_be64(&power->proc.accumulator),
+				       get_unaligned_be32(&power->proc.update_tag));
 		break;
 	case 6:
 		val = (u64)get_unaligned_be32(&power->proc.update_tag) *
@@ -555,8 +553,8 @@ static ssize_t occ_show_power_a0(struct device *dev,
 		return sysfs_emit(buf, "%u_vdd\n",
 				  get_unaligned_be32(&power->sensor_id));
 	case 9:
-		val = occ_get_powr_avg(&power->vdd.accumulator,
-				       &power->vdd.update_tag);
+		val = occ_get_powr_avg(get_unaligned_be64(&power->vdd.accumulator),
+				       get_unaligned_be32(&power->vdd.update_tag));
 		break;
 	case 10:
 		val = (u64)get_unaligned_be32(&power->vdd.update_tag) *
@@ -569,8 +567,8 @@ static ssize_t occ_show_power_a0(struct device *dev,
 		return sysfs_emit(buf, "%u_vdn\n",
 				  get_unaligned_be32(&power->sensor_id));
 	case 13:
-		val = occ_get_powr_avg(&power->vdn.accumulator,
-				       &power->vdn.update_tag);
+		val = occ_get_powr_avg(get_unaligned_be64(&power->vdn.accumulator),
+				       get_unaligned_be32(&power->vdn.update_tag));
 		break;
 	case 14:
 		val = (u64)get_unaligned_be32(&power->vdn.update_tag) *
-- 
2.39.5