[PATCH] hwmon: occ: rework attribute registration for stack usage

From: Arnd Bergmann
Date: Tue Jun 10 2025 - 05:25:20 EST

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From: Arnd Bergmann <arnd@xxxxxxxx>

clang produces an output with excessive stack usage when building the
occ_setup_sensor_attrs() function, apparently the result of having
a lot of struct literals and building with the -fno-strict-overflow
option that leads clang to skip some optimization in case the 'attr'
pointer overruns:

drivers/hwmon/occ/common.c:775:12: error: stack frame size (1392) exceeds limit (1280) in 'occ_setup_sensor_attrs' [-Werror,-Wframe-larger-than]

Replace the custom macros for initializing the attributes with a
simpler function call that does not run into this corner case.

Link: https://godbolt.org/z/Wf1Yx76a5
Fixes: 54076cb3b5ff ("hwmon (occ): Add sensor attributes and register hwmon device")
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
drivers/hwmon/occ/common.c | 212 +++++++++++++++----------------------
1 file changed, 85 insertions(+), 127 deletions(-)

diff --git a/drivers/hwmon/occ/common.c b/drivers/hwmon/occ/common.c
index 36b3900218ce..b3694a4209b9 100644
--- a/drivers/hwmon/occ/common.c
+++ b/drivers/hwmon/occ/common.c
@@ -745,29 +745,30 @@ static ssize_t occ_show_extended(struct device *dev,
}

/*
- * Some helper macros to make it easier to define an occ_attribute. Since these
- * are dynamically allocated, we shouldn't use the existing kernel macros which
+ * A helper to make it easier to define an occ_attribute. Since these
+ * are dynamically allocated, we cannot use the existing kernel macros which
* stringify the name argument.
*/
-#define ATTR_OCC(_name, _mode, _show, _store) { \
- .attr = { \
- .name = _name, \
- .mode = VERIFY_OCTAL_PERMISSIONS(_mode), \
- }, \
- .show = _show, \
- .store = _store, \
-}
-
-#define SENSOR_ATTR_OCC(_name, _mode, _show, _store, _nr, _index) { \
- .dev_attr = ATTR_OCC(_name, _mode, _show, _store), \
- .index = _index, \
- .nr = _nr, \
+static void occ_init_attribute(struct occ_attribute *attr, int mode,
+ ssize_t (*show)(struct device *dev, struct device_attribute *attr, char *buf),
+ ssize_t (*store)(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count),
+ int nr, int index, const char *fmt, ...)
+{
+ va_list args;
+
+ va_start(args, fmt);
+ vsnprintf(attr->name, sizeof(attr->name), fmt, args);
+ va_end(args);
+
+ attr->sensor.dev_attr.attr.name = attr->name;
+ attr->sensor.dev_attr.attr.mode = mode;
+ attr->sensor.dev_attr.show = show;
+ attr->sensor.dev_attr.store = store;
+ attr->sensor.index = index;
+ attr->sensor.nr = nr;
}

-#define OCC_INIT_ATTR(_name, _mode, _show, _store, _nr, _index) \
- ((struct sensor_device_attribute_2) \
- SENSOR_ATTR_OCC(_name, _mode, _show, _store, _nr, _index))
-
/*
* Allocate and instatiate sensor_device_attribute_2s. It's most efficient to
* use our own instead of the built-in hwmon attribute types.
@@ -853,14 +854,15 @@ static int occ_setup_sensor_attrs(struct occ *occ)
sensors->extended.num_sensors = 0;
}

- occ->attrs = devm_kzalloc(dev, sizeof(*occ->attrs) * num_attrs,
+ occ->attrs = devm_kcalloc(dev, num_attrs, sizeof(*occ->attrs),
GFP_KERNEL);
if (!occ->attrs)
return -ENOMEM;

/* null-terminated list */
- occ->group.attrs = devm_kzalloc(dev, sizeof(*occ->group.attrs) *
- num_attrs + 1, GFP_KERNEL);
+ occ->group.attrs = devm_kcalloc(dev, num_attrs + 1,
+ sizeof(*occ->group.attrs),
+ GFP_KERNEL);
if (!occ->group.attrs)
return -ENOMEM;

@@ -870,43 +872,33 @@ static int occ_setup_sensor_attrs(struct occ *occ)
s = i + 1;
temp = ((struct temp_sensor_2 *)sensors->temp.data) + i;

- snprintf(attr->name, sizeof(attr->name), "temp%d_label", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444, show_temp, NULL,
- 0, i);
+ occ_init_attribute(attr, 0444, show_temp, NULL,
+ 0, i, "temp%d_label", s);
attr++;

if (sensors->temp.version == 2 &&
temp->fru_type == OCC_FRU_TYPE_VRM) {
- snprintf(attr->name, sizeof(attr->name),
- "temp%d_alarm", s);
+ occ_init_attribute(attr, 0444, show_temp, NULL,
+ 1, i, "temp%d_alarm", s);
} else {
- snprintf(attr->name, sizeof(attr->name),
- "temp%d_input", s);
+ occ_init_attribute(attr, 0444, show_temp, NULL,
+ 1, i, "temp%d_input", s);
}

- attr->sensor = OCC_INIT_ATTR(attr->name, 0444, show_temp, NULL,
- 1, i);
attr++;

if (sensors->temp.version > 1) {
- snprintf(attr->name, sizeof(attr->name),
- "temp%d_fru_type", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444,
- show_temp, NULL, 2, i);
+ occ_init_attribute(attr, 0444, show_temp, NULL,
+ 2, i, "temp%d_fru_type", s);
attr++;

- snprintf(attr->name, sizeof(attr->name),
- "temp%d_fault", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444,
- show_temp, NULL, 3, i);
+ occ_init_attribute(attr, 0444, show_temp, NULL,
+ 3, i, "temp%d_fault", s);
attr++;

if (sensors->temp.version == 0x10) {
- snprintf(attr->name, sizeof(attr->name),
- "temp%d_max", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444,
- show_temp, NULL,
- 4, i);
+ occ_init_attribute(attr, 0444, show_temp, NULL,
+ 4, i, "temp%d_max", s);
attr++;
}
}
@@ -915,14 +907,12 @@ static int occ_setup_sensor_attrs(struct occ *occ)
for (i = 0; i < sensors->freq.num_sensors; ++i) {
s = i + 1;

- snprintf(attr->name, sizeof(attr->name), "freq%d_label", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444, show_freq, NULL,
- 0, i);
+ occ_init_attribute(attr, 0444, show_freq, NULL,
+ 0, i, "freq%d_label", s);
attr++;

- snprintf(attr->name, sizeof(attr->name), "freq%d_input", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444, show_freq, NULL,
- 1, i);
+ occ_init_attribute(attr, 0444, show_freq, NULL,
+ 1, i, "freq%d_input", s);
attr++;
}

@@ -938,32 +928,24 @@ static int occ_setup_sensor_attrs(struct occ *occ)
s = (i * 4) + 1;

for (j = 0; j < 4; ++j) {
- snprintf(attr->name, sizeof(attr->name),
- "power%d_label", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444,
- show_power, NULL,
- nr++, i);
+ occ_init_attribute(attr, 0444, show_power,
+ NULL, nr++, i,
+ "power%d_label", s);
attr++;

- snprintf(attr->name, sizeof(attr->name),
- "power%d_average", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444,
- show_power, NULL,
- nr++, i);
+ occ_init_attribute(attr, 0444, show_power,
+ NULL, nr++, i,
+ "power%d_average", s);
attr++;

- snprintf(attr->name, sizeof(attr->name),
- "power%d_average_interval", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444,
- show_power, NULL,
- nr++, i);
+ occ_init_attribute(attr, 0444, show_power,
+ NULL, nr++, i,
+ "power%d_average_interval", s);
attr++;

- snprintf(attr->name, sizeof(attr->name),
- "power%d_input", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444,
- show_power, NULL,
- nr++, i);
+ occ_init_attribute(attr, 0444, show_power,
+ NULL, nr++, i,
+ "power%d_input", s);
attr++;

s++;
@@ -975,28 +957,20 @@ static int occ_setup_sensor_attrs(struct occ *occ)
for (i = 0; i < sensors->power.num_sensors; ++i) {
s = i + 1;

- snprintf(attr->name, sizeof(attr->name),
- "power%d_label", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444,
- show_power, NULL, 0, i);
+ occ_init_attribute(attr, 0444, show_power, NULL,
+ 0, i, "power%d_label", s);
attr++;

- snprintf(attr->name, sizeof(attr->name),
- "power%d_average", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444,
- show_power, NULL, 1, i);
+ occ_init_attribute(attr, 0444, show_power, NULL,
+ 1, i, "power%d_average", s);
attr++;

- snprintf(attr->name, sizeof(attr->name),
- "power%d_average_interval", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444,
- show_power, NULL, 2, i);
+ occ_init_attribute(attr, 0444, show_power, NULL,
+ 2, i, "power%d_average_interval", s);
attr++;

- snprintf(attr->name, sizeof(attr->name),
- "power%d_input", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444,
- show_power, NULL, 3, i);
+ occ_init_attribute(attr, 0444, show_power, NULL,
+ 3, i, "power%d_input", s);
attr++;
}

@@ -1004,56 +978,43 @@ static int occ_setup_sensor_attrs(struct occ *occ)
}

if (sensors->caps.num_sensors >= 1) {
- snprintf(attr->name, sizeof(attr->name), "power%d_label", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444, show_caps, NULL,
- 0, 0);
+ occ_init_attribute(attr, 0444, show_caps, NULL,
+ 0, 0, "power%d_label", s);
attr++;

- snprintf(attr->name, sizeof(attr->name), "power%d_cap", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444, show_caps, NULL,
- 1, 0);
+ occ_init_attribute(attr, 0444, show_caps, NULL,
+ 1, 0, "power%d_cap", s);
attr++;

- snprintf(attr->name, sizeof(attr->name), "power%d_input", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444, show_caps, NULL,
- 2, 0);
+ occ_init_attribute(attr, 0444, show_caps, NULL,
+ 2, 0, "power%d_input", s);
attr++;

- snprintf(attr->name, sizeof(attr->name),
- "power%d_cap_not_redundant", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444, show_caps, NULL,
- 3, 0);
+ occ_init_attribute(attr, 0444, show_caps, NULL,
+ 3, 0, "power%d_cap_not_redundant", s);
attr++;

- snprintf(attr->name, sizeof(attr->name), "power%d_cap_max", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444, show_caps, NULL,
- 4, 0);
+ occ_init_attribute(attr, 0444, show_caps, NULL,
+ 4, 0, "power%d_cap_max", s);
attr++;

- snprintf(attr->name, sizeof(attr->name), "power%d_cap_min", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444, show_caps, NULL,
- 5, 0);
+ occ_init_attribute(attr, 0444, show_caps, NULL,
+ 5, 0, "power%d_cap_min", s);
attr++;

- snprintf(attr->name, sizeof(attr->name), "power%d_cap_user",
- s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0644, show_caps,
- occ_store_caps_user, 6, 0);
+ occ_init_attribute(attr, 0644, show_caps, occ_store_caps_user,
+ 6, 0, "power%d_cap_user", s);
attr++;

if (sensors->caps.version > 1) {
- snprintf(attr->name, sizeof(attr->name),
- "power%d_cap_user_source", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444,
- show_caps, NULL, 7, 0);
+ occ_init_attribute(attr, 0444, show_caps, NULL,
+ 7, 0, "power%d_cap_user_source", s);
attr++;

if (sensors->caps.version > 2) {
- snprintf(attr->name, sizeof(attr->name),
- "power%d_cap_min_soft", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444,
- show_caps, NULL,
- 8, 0);
+ occ_init_attribute(attr, 0444, show_caps, NULL,
+ 8, 0,
+ "power%d_cap_min_soft", s);
attr++;
}
}
@@ -1062,19 +1023,16 @@ static int occ_setup_sensor_attrs(struct occ *occ)
for (i = 0; i < sensors->extended.num_sensors; ++i) {
s = i + 1;

- snprintf(attr->name, sizeof(attr->name), "extn%d_label", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444,
- occ_show_extended, NULL, 0, i);
+ occ_init_attribute(attr, 0444, occ_show_extended, NULL,
+ 0, i, "extn%d_label", s);
attr++;

- snprintf(attr->name, sizeof(attr->name), "extn%d_flags", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444,
- occ_show_extended, NULL, 1, i);
+ occ_init_attribute(attr, 0444, occ_show_extended, NULL,
+ 1, i, "extn%d_flags", s);
attr++;

- snprintf(attr->name, sizeof(attr->name), "extn%d_input", s);
- attr->sensor = OCC_INIT_ATTR(attr->name, 0444,
- occ_show_extended, NULL, 2, i);
+ occ_init_attribute(attr, 0444, occ_show_extended, NULL,
+ 2, i, "extn%d_input", s);
attr++;
}

--
2.39.5

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