cpuidle: change enter_s2idle() prototype

Control Flow Integrity(CFI) is a security mechanism that disallows
changes to the original control flow graph of a compiled binary,
making it significantly harder to perform such attacks.

init_state_node() assign same function callback to different
function pointer declarations.

static int init_state_node(struct cpuidle_state *idle_state,
                           const struct of_device_id *matches,
                           struct device_node *state_node) { ...
        idle_state->enter = match_id->data; ...
        idle_state->enter_s2idle = match_id->data; }

Function declarations:

struct cpuidle_state { ...
        int (*enter) (struct cpuidle_device *dev,
                      struct cpuidle_driver *drv,
                      int index);

        void (*enter_s2idle) (struct cpuidle_device *dev,
                              struct cpuidle_driver *drv,
                              int index); };

In this case, either enter() or enter_s2idle() would cause CFI check
failed since they use same callee.

Align function prototype of enter() since it needs return value for
some use cases. The return value of enter_s2idle() is no
need currently.

Signed-off-by: Neal Liu <neal.liu@mediatek.com>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 75534c5..6ffb6c9 100644 (file)
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -655,8 +655,8 @@ static int acpi_idle_enter(struct cpuidle_device *dev,
        return index;
 }
 
-static void acpi_idle_enter_s2idle(struct cpuidle_device *dev,
-                                  struct cpuidle_driver *drv, int index)
+static int acpi_idle_enter_s2idle(struct cpuidle_device *dev,
+                                 struct cpuidle_driver *drv, int index)
 {
        struct acpi_processor_cx *cx = per_cpu(acpi_cstate[index], dev->cpu);
 
@@ -674,6 +674,8 @@ static void acpi_idle_enter_s2idle(struct cpuidle_device *dev,
                }
        }
        acpi_idle_do_entry(cx);
+
+       return 0;
 }
 
 static int acpi_processor_setup_cpuidle_cx(struct acpi_processor *pr,

diff --git a/drivers/cpuidle/cpuidle-tegra.c b/drivers/cpuidle/cpuidle-tegra.c
index 1500458..a12fb14 100644 (file)
--- a/drivers/cpuidle/cpuidle-tegra.c
+++ b/drivers/cpuidle/cpuidle-tegra.c
@@ -253,11 +253,13 @@ static int tegra_cpuidle_enter(struct cpuidle_device *dev,
        return err ? -1 : index;
 }
 
-static void tegra114_enter_s2idle(struct cpuidle_device *dev,
-                                 struct cpuidle_driver *drv,
-                                 int index)
+static int tegra114_enter_s2idle(struct cpuidle_device *dev,
+                                struct cpuidle_driver *drv,
+                                int index)
 {
        tegra_cpuidle_enter(dev, drv, index);
+
+       return 0;
 }
 
 /*

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index fa23a7e..3f86f36 100644 (file)
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -173,13 +173,15 @@ static __cpuidle int intel_idle(struct cpuidle_device *dev,
  * Invoked as a suspend-to-idle callback routine with frozen user space, frozen
  * scheduler tick and suspended scheduler clock on the target CPU.
  */
-static __cpuidle void intel_idle_s2idle(struct cpuidle_device *dev,
-                                       struct cpuidle_driver *drv, int index)
+static __cpuidle int intel_idle_s2idle(struct cpuidle_device *dev,
+                                      struct cpuidle_driver *drv, int index)
 {
        unsigned long eax = flg2MWAIT(drv->states[index].flags);
        unsigned long ecx = 1; /* break on interrupt flag */
 
        mwait_idle_with_hints(eax, ecx);
+
+       return 0;
 }
 
 /*

diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index ec2ef63..b65909a 100644 (file)
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -65,10 +65,13 @@ struct cpuidle_state {
         * CPUs execute ->enter_s2idle with the local tick or entire timekeeping
         * suspended, so it must not re-enable interrupts at any point (even
         * temporarily) or attempt to change states of clock event devices.
+        *
+        * This callback may point to the same function as ->enter if all of
+        * the above requirements are met by it.
         */
-       void (*enter_s2idle) (struct cpuidle_device *dev,
-                             struct cpuidle_driver *drv,
-                             int index);
+       int (*enter_s2idle)(struct cpuidle_device *dev,
+                           struct cpuidle_driver *drv,
+                           int index);
 };
 
 /* Idle State Flags */