arm: mpu: Add user context API placeholder

This patch adds a configure_mpu_user_context API and implements
the required function placeholders in the NXP and ARM MPU files.

Signed-off-by: Andy Gross <[email protected]>

Author: Andy Gross

arch/arm/core/cortex_m/mpu/arm_core_mpu.c

@@ -32,6 +32,22 @@ void configure_mpu_stack_guard(struct k_thread *thread)
 #endif
 
 #if defined(CONFIG_USERSPACE)
+/*
+ * @brief Configure MPU user context
+ *
+ * This function configures the thread's user context.
+ * The functionality is meant to be used during context switch.
+ *
+ * @param thread thread info data structure.
+ */
+void configure_mpu_user_context(struct k_thread *thread)
+{
+	SYS_LOG_DBG("configure user thread %p's context", thread);
+	arm_core_mpu_disable();
+	arm_core_mpu_configure_user_context(thread);
+	arm_core_mpu_enable();
+}
+
 /*
  * @brief Configure MPU memory domain
  *

arch/arm/core/cortex_m/mpu/arm_mpu.c

@@ -240,6 +240,11 @@ void arm_core_mpu_configure(u8_t type, u32_t base, u32_t size)
 }
 
 #if defined(CONFIG_USERSPACE)
+void arm_core_mpu_configure_user_context(struct k_thread *thread)
+{
+	return 0;
+}
+
 /**
  * @brief configure MPU regions for the memory partitions of the memory domain
  *

arch/arm/core/cortex_m/mpu/nxp_mpu.c

@@ -249,6 +249,11 @@ void arm_core_mpu_configure(u8_t type, u32_t base, u32_t size)
 }
 
 #if defined(CONFIG_USERSPACE)
+void arm_core_mpu_configure_user_context(struct k_thread *thread)
+{
+	return 0;
+}
+
 /**
  * @brief configure MPU regions for the memory partitions of the memory domain
  *

include/arch/arm/cortex_m/mpu/arm_core_mpu.h

@@ -42,6 +42,17 @@ void configure_mpu_stack_guard(struct k_thread *thread);
  * @param thread thread info data structure.
  */
 void configure_mpu_mem_domain(struct k_thread *thread);
+
+/*
+ * @brief Configure MPU user context
+ *
+ * This function configures the stack and application data regions
+ * for user mode threads
+ *
+ * @param thread thread info data structure.
+ */
+void configure_mpu_user_context(struct k_thread *thread);
+
 #endif
 
 #ifdef __cplusplus

include/arch/arm/cortex_m/mpu/arm_core_mpu_dev.h

@@ -37,6 +37,7 @@ extern "C" {
 #if defined(CONFIG_ARM_CORE_MPU)
 struct k_mem_domain;
 struct k_mem_partition;
+struct k_thread;
 
 /* ARM Core MPU Driver API */
 
@@ -71,6 +72,13 @@ void arm_core_mpu_configure(u8_t type, u32_t base, u32_t size);
  */
 void arm_core_mpu_configure_mem_domain(struct k_mem_domain *mem_domain);
 
+/**
+ * @brief configure MPU regions for a user thread's context
+ *
+ * @param	thread	thread to configure
+ */
+void arm_core_mpu_configure_user_context(struct k_thread *thread);
+
 /**
  * @brief configure MPU region for a single memory partition
  *