cpufreq: Avoid creating excessively large stack frames

In the process of modifying a cpufreq policy, the cpufreq core makes
a copy of it including all of the internals which is stored on the
CPU stack.  Because struct cpufreq_policy is relatively large, this
may cause the size of the stack frame to exceed the 2 KB limit and
so the GCC complains when -Wframe-larger-than= is used.

In fact, it is not necessary to copy the entire policy structure
in order to modify it, however.

First, because cpufreq_set_policy() obtains the min and max policy
limits from frequency QoS now, it is not necessary to pass the limits
to it from the callers.  The only things that need to be passed to it
from there are the new governor pointer or (if there is a built-in
governor in the driver) the "policy" value representing the governor
choice.  They both can be passed as individual arguments, though, so
make cpufreq_set_policy() take them this way and rework its callers
accordingly.  This avoids making copies of cpufreq policies in the
callers of cpufreq_set_policy().

Second, cpufreq_set_policy() still needs to pass the new policy
data to the ->verify() callback of the cpufreq driver whose task
is to sanitize the min and max policy limits.  It still does not
need to make a full copy of struct cpufreq_policy for this purpose,
but it needs to pass a few items from it to the driver in case they
are needed (different drivers have different needs in that respect
and all of them have to be covered).  For this reason, introduce
struct cpufreq_policy_data to hold copies of the members of
struct cpufreq_policy used by the existing ->verify() driver
callbacks and pass a pointer to a temporary structure of that
type to ->verify() (instead of passing a pointer to full struct
cpufreq_policy to it).

While at it, notice that intel_pstate and longrun don't really need
to verify the "policy" value in struct cpufreq_policy, so drop those
check from them to avoid copying "policy" into struct
cpufreq_policy_data (which allows it to be slightly smaller).

Also while at it fix up white space in a couple of places and make
cpufreq_set_policy() static (as it can be so).

Fixes: 3000ce3 ("cpufreq: Use per-policy frequency QoS")
Link: https://lore.kernel.org/linux-pm/CAMuHMdX6-jb1W8uC2_237m8ctCpsnGp=JCxqt8pCWVqNXHmkVg@mail.gmail.com
Reported-by: kbuild test robot <[email protected]>
Reported-by: Geert Uytterhoeven <[email protected]>
Cc: 5.4+ <[email protected]> # 5.4+
Signed-off-by: Rafael J. Wysocki <[email protected]>
Acked-by: Viresh Kumar <[email protected]>

Author: rafaeljw

drivers/cpufreq/cppc_cpufreq.c

@@ -221,7 +221,7 @@ static int cppc_cpufreq_set_target(struct cpufreq_policy *policy,
 	return ret;
 }
 
-static int cppc_verify_policy(struct cpufreq_policy *policy)
+static int cppc_verify_policy(struct cpufreq_policy_data *policy)
 {
 	cpufreq_verify_within_cpu_limits(policy);
 	return 0;

drivers/cpufreq/cpufreq-nforce2.c

@@ -291,7 +291,7 @@ static int nforce2_target(struct cpufreq_policy *policy,
  * nforce2_verify - verifies a new CPUFreq policy
  * @policy: new policy
  */
-static int nforce2_verify(struct cpufreq_policy *policy)
+static int nforce2_verify(struct cpufreq_policy_data *policy)
 {
 	unsigned int fsb_pol_max;
 

drivers/cpufreq/cpufreq.c

@@ -74,6 +74,9 @@ static void cpufreq_exit_governor(struct cpufreq_policy *policy);
 static int cpufreq_start_governor(struct cpufreq_policy *policy);
 static void cpufreq_stop_governor(struct cpufreq_policy *policy);
 static void cpufreq_governor_limits(struct cpufreq_policy *policy);
+static int cpufreq_set_policy(struct cpufreq_policy *policy,
+			      struct cpufreq_governor *new_gov,
+			      unsigned int new_pol);
 
 /**
  * Two notifier lists: the "policy" list is involved in the
@@ -616,25 +619,22 @@ static struct cpufreq_governor *find_governor(const char *str_governor)
 	return NULL;
 }
 
-static int cpufreq_parse_policy(char *str_governor,
-				struct cpufreq_policy *policy)
+static unsigned int cpufreq_parse_policy(char *str_governor)
 {
-	if (!strncasecmp(str_governor, "performance", CPUFREQ_NAME_LEN)) {
-		policy->policy = CPUFREQ_POLICY_PERFORMANCE;
-		return 0;
-	}
-	if (!strncasecmp(str_governor, "powersave", CPUFREQ_NAME_LEN)) {
-		policy->policy = CPUFREQ_POLICY_POWERSAVE;
-		return 0;
-	}
-	return -EINVAL;
+	if (!strncasecmp(str_governor, "performance", CPUFREQ_NAME_LEN))
+		return CPUFREQ_POLICY_PERFORMANCE;
+
+	if (!strncasecmp(str_governor, "powersave", CPUFREQ_NAME_LEN))
+		return CPUFREQ_POLICY_POWERSAVE;
+
+	return CPUFREQ_POLICY_UNKNOWN;
 }
 
 /**
  * cpufreq_parse_governor - parse a governor string only for has_target()
+ * @str_governor: Governor name.
  */
-static int cpufreq_parse_governor(char *str_governor,
-				  struct cpufreq_policy *policy)
+static struct cpufreq_governor *cpufreq_parse_governor(char *str_governor)
 {
 	struct cpufreq_governor *t;
 
@@ -648,7 +648,7 @@ static int cpufreq_parse_governor(char *str_governor,
 
 		ret = request_module("cpufreq_%s", str_governor);
 		if (ret)
-			return -EINVAL;
+			return NULL;
 
 		mutex_lock(&cpufreq_governor_mutex);
 
@@ -659,12 +659,7 @@ static int cpufreq_parse_governor(char *str_governor,
 
 	mutex_unlock(&cpufreq_governor_mutex);
 
-	if (t) {
-		policy->governor = t;
-		return 0;
-	}
-
-	return -EINVAL;
+	return t;
 }
 
 /**
@@ -765,28 +760,33 @@ static ssize_t show_scaling_governor(struct cpufreq_policy *policy, char *buf)
 static ssize_t store_scaling_governor(struct cpufreq_policy *policy,
 					const char *buf, size_t count)
 {
+	char str_governor[16];
 	int ret;
-	char	str_governor[16];
-	struct cpufreq_policy new_policy;
-
-	memcpy(&new_policy, policy, sizeof(*policy));
 
 	ret = sscanf(buf, "%15s", str_governor);
 	if (ret != 1)
 		return -EINVAL;
 
 	if (cpufreq_driver->setpolicy) {
-		if (cpufreq_parse_policy(str_governor, &new_policy))
+		unsigned int new_pol;
+
+		new_pol = cpufreq_parse_policy(str_governor);
+		if (!new_pol)
 			return -EINVAL;
+
+		ret = cpufreq_set_policy(policy, NULL, new_pol);
 	} else {
-		if (cpufreq_parse_governor(str_governor, &new_policy))
+		struct cpufreq_governor *new_gov;
+
+		new_gov = cpufreq_parse_governor(str_governor);
+		if (!new_gov)
 			return -EINVAL;
-	}
 
-	ret = cpufreq_set_policy(policy, &new_policy);
+		ret = cpufreq_set_policy(policy, new_gov,
+					 CPUFREQ_POLICY_UNKNOWN);
 
-	if (new_policy.governor)
-		module_put(new_policy.governor->owner);
+		module_put(new_gov->owner);
+	}
 
 	return ret ? ret : count;
 }
@@ -1053,40 +1053,33 @@ __weak struct cpufreq_governor *cpufreq_default_governor(void)
 
 static int cpufreq_init_policy(struct cpufreq_policy *policy)
 {
-	struct cpufreq_governor *gov = NULL, *def_gov = NULL;
-	struct cpufreq_policy new_policy;
-
-	memcpy(&new_policy, policy, sizeof(*policy));
-
-	def_gov = cpufreq_default_governor();
+	struct cpufreq_governor *def_gov = cpufreq_default_governor();
+	struct cpufreq_governor *gov = NULL;
+	unsigned int pol = CPUFREQ_POLICY_UNKNOWN;
 
 	if (has_target()) {
-		/*
-		 * Update governor of new_policy to the governor used before
-		 * hotplug
-		 */
+		/* Update policy governor to the one used before hotplug. */
 		gov = find_governor(policy->last_governor);
 		if (gov) {
 			pr_debug("Restoring governor %s for cpu %d\n",
-				policy->governor->name, policy->cpu);
-		} else {
-			if (!def_gov)
-				return -ENODATA;
+				 policy->governor->name, policy->cpu);
+		} else if (def_gov) {
 			gov = def_gov;
+		} else {
+			return -ENODATA;
 		}
-		new_policy.governor = gov;
 	} else {
 		/* Use the default policy if there is no last_policy. */
 		if (policy->last_policy) {
-			new_policy.policy = policy->last_policy;
+			pol = policy->last_policy;
+		} else if (def_gov) {
+			pol = cpufreq_parse_policy(def_gov->name);
 		} else {
-			if (!def_gov)
-				return -ENODATA;
-			cpufreq_parse_policy(def_gov->name, &new_policy);
+			return -ENODATA;
 		}
 	}
 
-	return cpufreq_set_policy(policy, &new_policy);
+	return cpufreq_set_policy(policy, gov, pol);
 }
 
 static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy, unsigned int cpu)
@@ -1114,13 +1107,10 @@ static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy, unsigned int cp
 
 void refresh_frequency_limits(struct cpufreq_policy *policy)
 {
-	struct cpufreq_policy new_policy;
-
 	if (!policy_is_inactive(policy)) {
-		new_policy = *policy;
 		pr_debug("updating policy for CPU %u\n", policy->cpu);
 
-		cpufreq_set_policy(policy, &new_policy);
+		cpufreq_set_policy(policy, policy->governor, policy->policy);
 	}
 }
 EXPORT_SYMBOL(refresh_frequency_limits);
@@ -2364,46 +2354,49 @@ EXPORT_SYMBOL(cpufreq_get_policy);
 /**
  * cpufreq_set_policy - Modify cpufreq policy parameters.
  * @policy: Policy object to modify.
- * @new_policy: New policy data.
+ * @new_gov: Policy governor pointer.
+ * @new_pol: Policy value (for drivers with built-in governors).
  *
- * Pass @new_policy to the cpufreq driver's ->verify() callback. Next, copy the
- * min and max parameters of @new_policy to @policy and either invoke the
- * driver's ->setpolicy() callback (if present) or carry out a governor update
- * for @policy.  That is, run the current governor's ->limits() callback (if the
- * governor field in @new_policy points to the same object as the one in
- * @policy) or replace the governor for @policy with the new one stored in
- * @new_policy.
+ * Invoke the cpufreq driver's ->verify() callback to sanity-check the frequency
+ * limits to be set for the policy, update @policy with the verified limits
+ * values and either invoke the driver's ->setpolicy() callback (if present) or
+ * carry out a governor update for @policy.  That is, run the current governor's
+ * ->limits() callback (if @new_gov points to the same object as the one in
+ * @policy) or replace the governor for @policy with @new_gov.
  *
  * The cpuinfo part of @policy is not updated by this function.
  */
-int cpufreq_set_policy(struct cpufreq_policy *policy,
-		       struct cpufreq_policy *new_policy)
+static int cpufreq_set_policy(struct cpufreq_policy *policy,
+			      struct cpufreq_governor *new_gov,
+			      unsigned int new_pol)
 {
+	struct cpufreq_policy_data new_data;
 	struct cpufreq_governor *old_gov;
 	int ret;
 
-	pr_debug("setting new policy for CPU %u: %u - %u kHz\n",
-		 new_policy->cpu, new_policy->min, new_policy->max);
-
-	memcpy(&new_policy->cpuinfo, &policy->cpuinfo, sizeof(policy->cpuinfo));
-
+	memcpy(&new_data.cpuinfo, &policy->cpuinfo, sizeof(policy->cpuinfo));
+	new_data.freq_table = policy->freq_table;
+	new_data.cpu = policy->cpu;
 	/*
 	 * PM QoS framework collects all the requests from users and provide us
 	 * the final aggregated value here.
 	 */
-	new_policy->min = freq_qos_read_value(&policy->constraints, FREQ_QOS_MIN);
-	new_policy->max = freq_qos_read_value(&policy->constraints, FREQ_QOS_MAX);
+	new_data.min = freq_qos_read_value(&policy->constraints, FREQ_QOS_MIN);
+	new_data.max = freq_qos_read_value(&policy->constraints, FREQ_QOS_MAX);
+
+	pr_debug("setting new policy for CPU %u: %u - %u kHz\n",
+		 new_data.cpu, new_data.min, new_data.max);
 
 	/*
 	 * Verify that the CPU speed can be set within these limits and make sure
 	 * that min <= max.
 	 */
-	ret = cpufreq_driver->verify(new_policy);
+	ret = cpufreq_driver->verify(&new_data);
 	if (ret)
 		return ret;
 
-	policy->min = new_policy->min;
-	policy->max = new_policy->max;
+	policy->min = new_data.min;
+	policy->max = new_data.max;
 	trace_cpu_frequency_limits(policy);
 
 	policy->cached_target_freq = UINT_MAX;
@@ -2412,12 +2405,12 @@ int cpufreq_set_policy(struct cpufreq_policy *policy,
 		 policy->min, policy->max);
 
 	if (cpufreq_driver->setpolicy) {
-		policy->policy = new_policy->policy;
+		policy->policy = new_pol;
 		pr_debug("setting range\n");
 		return cpufreq_driver->setpolicy(policy);
 	}
 
-	if (new_policy->governor == policy->governor) {
+	if (new_gov == policy->governor) {
 		pr_debug("governor limits update\n");
 		cpufreq_governor_limits(policy);
 		return 0;
@@ -2434,7 +2427,7 @@ int cpufreq_set_policy(struct cpufreq_policy *policy,
 	}
 
 	/* start new governor */
-	policy->governor = new_policy->governor;
+	policy->governor = new_gov;
 	ret = cpufreq_init_governor(policy);
 	if (!ret) {
 		ret = cpufreq_start_governor(policy);

drivers/cpufreq/freq_table.c

@@ -60,7 +60,7 @@ int cpufreq_frequency_table_cpuinfo(struct cpufreq_policy *policy,
 		return 0;
 }
 
-int cpufreq_frequency_table_verify(struct cpufreq_policy *policy,
+int cpufreq_frequency_table_verify(struct cpufreq_policy_data *policy,
 				   struct cpufreq_frequency_table *table)
 {
 	struct cpufreq_frequency_table *pos;
@@ -100,7 +100,7 @@ EXPORT_SYMBOL_GPL(cpufreq_frequency_table_verify);
  * Generic routine to verify policy & frequency table, requires driver to set
  * policy->freq_table prior to it.
  */
-int cpufreq_generic_frequency_table_verify(struct cpufreq_policy *policy)
+int cpufreq_generic_frequency_table_verify(struct cpufreq_policy_data *policy)
 {
 	if (!policy->freq_table)
 		return -ENODEV;

drivers/cpufreq/gx-suspmod.c

@@ -328,7 +328,7 @@ static void gx_set_cpuspeed(struct cpufreq_policy *policy, unsigned int khz)
  *      for the hardware supported by the driver.
  */
 
-static int cpufreq_gx_verify(struct cpufreq_policy *policy)
+static int cpufreq_gx_verify(struct cpufreq_policy_data *policy)
 {
 	unsigned int tmp_freq = 0;
 	u8 tmp1, tmp2;