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: 3000ce3c52f8 ("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 <lkp@intel.com>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: 5.4+ <stable@vger.kernel.org> # 5.4+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

1 files changed, 23 insertions, 9 deletions

diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 31b1b0e03df8..018dce868de6 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -148,6 +148,20 @@ struct cpufreq_policy {
 	struct notifier_block nb_max;
 };
 
+/*
+ * Used for passing new cpufreq policy data to the cpufreq driver's ->verify()
+ * callback for sanitization.  That callback is only expected to modify the min
+ * and max values, if necessary, and specifically it must not update the
+ * frequency table.
+ */
+struct cpufreq_policy_data {
+	struct cpufreq_cpuinfo		cpuinfo;
+	struct cpufreq_frequency_table	*freq_table;
+	unsigned int			cpu;
+	unsigned int			min;    /* in kHz */
+	unsigned int			max;    /* in kHz */
+};
+
 struct cpufreq_freqs {
 	struct cpufreq_policy *policy;
 	unsigned int old;
@@ -201,8 +215,6 @@ u64 get_cpu_idle_time(unsigned int cpu, u64 *wall, int io_busy);
 struct cpufreq_policy *cpufreq_cpu_acquire(unsigned int cpu);
 void cpufreq_cpu_release(struct cpufreq_policy *policy);
 int cpufreq_get_policy(struct cpufreq_policy *policy, unsigned int cpu);
-int cpufreq_set_policy(struct cpufreq_policy *policy,
-		       struct cpufreq_policy *new_policy);
 void refresh_frequency_limits(struct cpufreq_policy *policy);
 void cpufreq_update_policy(unsigned int cpu);
 void cpufreq_update_limits(unsigned int cpu);
@@ -284,7 +296,7 @@ struct cpufreq_driver {
 
 	/* needed by all drivers */
 	int		(*init)(struct cpufreq_policy *policy);
-	int		(*verify)(struct cpufreq_policy *policy);
+	int		(*verify)(struct cpufreq_policy_data *policy);
 
 	/* define one out of two */
 	int		(*setpolicy)(struct cpufreq_policy *policy);
@@ -415,8 +427,9 @@ static inline int cpufreq_thermal_control_enabled(struct cpufreq_driver *drv)
 		(drv->flags & CPUFREQ_IS_COOLING_DEV);
 }
 
-static inline void cpufreq_verify_within_limits(struct cpufreq_policy *policy,
-		unsigned int min, unsigned int max)
+static inline void cpufreq_verify_within_limits(struct cpufreq_policy_data *policy,
+						unsigned int min,
+						unsigned int max)
 {
 	if (policy->min < min)
 		policy->min = min;
@@ -432,10 +445,10 @@ static inline void cpufreq_verify_within_limits(struct cpufreq_policy *policy,
 }
 
 static inline void
-cpufreq_verify_within_cpu_limits(struct cpufreq_policy *policy)
+cpufreq_verify_within_cpu_limits(struct cpufreq_policy_data *policy)
 {
 	cpufreq_verify_within_limits(policy, policy->cpuinfo.min_freq,
-			policy->cpuinfo.max_freq);
+				     policy->cpuinfo.max_freq);
 }
 
 #ifdef CONFIG_CPU_FREQ
@@ -513,6 +526,7 @@ static inline unsigned long cpufreq_scale(unsigned long old, u_int div,
  *                          CPUFREQ GOVERNORS                        *
  *********************************************************************/
 
+#define CPUFREQ_POLICY_UNKNOWN		(0)
 /*
  * If (cpufreq_driver->target) exists, the ->governor decides what frequency
  * within the limits is used. If (cpufreq_driver->setpolicy> exists, these
@@ -684,9 +698,9 @@ static inline void dev_pm_opp_free_cpufreq_table(struct device *dev,
 int cpufreq_frequency_table_cpuinfo(struct cpufreq_policy *policy,
 				    struct cpufreq_frequency_table *table);
 
-int cpufreq_frequency_table_verify(struct cpufreq_policy *policy,
+int cpufreq_frequency_table_verify(struct cpufreq_policy_data *policy,
 				   struct cpufreq_frequency_table *table);
-int cpufreq_generic_frequency_table_verify(struct cpufreq_policy *policy);
+int cpufreq_generic_frequency_table_verify(struct cpufreq_policy_data *policy);
 
 int cpufreq_table_index_unsorted(struct cpufreq_policy *policy,
 				 unsigned int target_freq,