Merge pull request #9030 from kjbracey-arm/mpu_size

Reduce ROM impact of MPU code

Author: Cruz Monrreal

TESTS/mbed_hal/mpu/main.cpp

@@ -72,11 +72,9 @@ static void hard_fault_handler_test()
 
 static void mpu_fault_test(const volatile uint16_t *mem_function)
 {
-    mbed_mpu_init();
-
-    // Verify that the mpu causes faults when executing ram
+    // Verify that the mpu causes faults when executing ram after init
     fault_count = 0;
-    mbed_mpu_enable_ram_xn(true);
+    mbed_mpu_init();
     call_mem(mem_function);
     TEST_ASSERT_EQUAL(1, fault_count);
 
@@ -86,7 +84,7 @@ static void mpu_fault_test(const volatile uint16_t *mem_function)
     call_mem(mem_function);
     TEST_ASSERT_EQUAL(0, fault_count);
 
-    // Verify that the mpu causes faults when executing ram
+    // Verify that the mpu can be turned back on
     fault_count = 0;
     mbed_mpu_enable_ram_xn(true);
     call_mem(mem_function);

hal/mpu/mbed_mpu_v8m.c

@@ -78,7 +78,8 @@ void mbed_mpu_init()
                 (3 << MPU_RBAR_AP_Pos) |             // RO allowed by all privilege levels
                 (0 << MPU_RBAR_XN_Pos);              // Execute Never disabled
     MPU->RLAR = (0x1FFFFFFF & MPU_RLAR_LIMIT_Msk) |     // Last address is 0x1FFFFFFF
-                (region << MPU_RLAR_AttrIndx_Pos);   // Attribute index - configured to be the same as the region number
+                (region << MPU_RLAR_AttrIndx_Pos) |  // Attribute index - configured to be the same as the region number
+                (1 << MPU_RLAR_EN_Pos);              // Region enabled
 
     region = 1;
     MPU->RNR = region;
@@ -90,7 +91,8 @@ void mbed_mpu_init()
                 (1 << MPU_RBAR_AP_Pos) |             // RW allowed by all privilege levels
                 (1 << MPU_RBAR_XN_Pos);              // Execute Never enabled
     MPU->RLAR = (0x3FFFFFFF & MPU_RLAR_LIMIT_Msk) |     // Last address is 0x3FFFFFFF
-                (region << MPU_RLAR_AttrIndx_Pos);   // Attribute index - configured to be the same as the region number
+                (region << MPU_RLAR_AttrIndx_Pos) |  // Attribute index - configured to be the same as the region number
+                (1 << MPU_RLAR_EN_Pos);              // Region enabled
 
     region = 2;
     MPU->RNR = region;
@@ -102,7 +104,8 @@ void mbed_mpu_init()
                 (1 << MPU_RBAR_AP_Pos) |             // RW allowed by all privilege levels
                 (1 << MPU_RBAR_XN_Pos);              // Execute Never enabled
     MPU->RLAR = (0x7FFFFFFF & MPU_RLAR_LIMIT_Msk) |     // Last address is 0x7FFFFFFF
-                (region << MPU_RLAR_AttrIndx_Pos);   // Attribute index - configured to be the same as the region number
+                (region << MPU_RLAR_AttrIndx_Pos) |  // Attribute index - configured to be the same as the region number
+                (1 << MPU_RLAR_EN_Pos);              // Region enabled
 
     region = 3;
     MPU->RNR = region;
@@ -114,7 +117,8 @@ void mbed_mpu_init()
                 (1 << MPU_RBAR_AP_Pos) |             // RW allowed by all privilege levels
                 (1 << MPU_RBAR_XN_Pos);              // Execute Never enabled
     MPU->RLAR = (0x9FFFFFFF & MPU_RLAR_LIMIT_Msk) |     // Last address is 0x9FFFFFFF
-                (region << MPU_RLAR_AttrIndx_Pos);   // Attribute index - configured to be the same as the region number
+                (region << MPU_RLAR_AttrIndx_Pos) |  // Attribute index - configured to be the same as the region number
+                (1 << MPU_RLAR_EN_Pos);              // Region enabled
 
     // Enable the MPU
     MPU->CTRL =

hal/mpu_api.h

@@ -64,8 +64,8 @@ extern "C" {
  * Initialize the MPU
  *
  * Initialize or re-initialize the memory protection unit.
- * It is implementation defined what region are protected
- * by the MPU after initialization.
+ * After initialization or re-initialization, ROM and RAM protection
+ * are both enabled.
  */
 void mbed_mpu_init(void);
 
@@ -75,7 +75,9 @@ void mbed_mpu_init(void);
  * This function is used to mark all of ROM as read and execute only.
  * When enabled writes to ROM cause a fault.
  *
- * @param enable true to disable execution in ram, false otherwise
+ * By default writes to ROM are disabled.
+ *
+ * @param enable true to disable writes to ROM, false otherwise
  */
 void mbed_mpu_enable_rom_wn(bool enable);
 
@@ -85,7 +87,9 @@ void mbed_mpu_enable_rom_wn(bool enable);
  * This function is used to mark all of RAM as execute never.
  * When enabled code is only allowed to execute from flash.
  *
- * @param enable true to disable execution in ram, false otherwise
+ * By default execution from RAM is disabled.
+ *
+ * @param enable true to disable execution from RAM, false otherwise
  */
 void mbed_mpu_enable_ram_xn(bool enable);
 

platform/mbed_mpu_mgmt.c

@@ -17,19 +17,19 @@
 #include "platform/mbed_mpu_mgmt.h"
 #include "platform/mbed_critical.h"
 #include "platform/mbed_error.h"
+#include "platform/mbed_assert.h"
 #include "hal/mpu_api.h"
 #include <limits.h>
 
+#if DEVICE_MPU
+
 static uint16_t mem_xn_lock;
 static uint16_t mem_wn_lock;
 
 void mbed_mpu_manager_lock_ram_execution()
 {
     core_util_critical_section_enter();
-    if (mem_xn_lock == USHRT_MAX) {
-        core_util_critical_section_exit();
-        MBED_ERROR1(MBED_MAKE_ERROR(MBED_MODULE_PLATFORM, MBED_ERROR_CODE_OVERFLOW), "Ram execute never lock overflow (> USHRT_MAX)", mem_xn_lock);
-    }
+    MBED_ASSERT(mem_xn_lock != USHRT_MAX);
     if (mem_xn_lock == 0) {
         mbed_mpu_enable_ram_xn(false);
     }
@@ -40,10 +40,7 @@ void mbed_mpu_manager_lock_ram_execution()
 void mbed_mpu_manager_unlock_ram_execution()
 {
     core_util_critical_section_enter();
-    if (mem_xn_lock == 0) {
-        core_util_critical_section_exit();
-        MBED_ERROR1(MBED_MAKE_ERROR(MBED_MODULE_PLATFORM, MBED_ERROR_CODE_UNDERFLOW), "Ram execute never lock underflow (< 0)", mem_xn_lock);
-    }
+    MBED_ASSERT(mem_xn_lock != 0);
     mem_xn_lock--;
     if (mem_xn_lock == 0) {
         mbed_mpu_enable_ram_xn(true);
@@ -54,10 +51,7 @@ void mbed_mpu_manager_unlock_ram_execution()
 void mbed_mpu_manager_lock_rom_write()
 {
     core_util_critical_section_enter();
-    if (mem_wn_lock == USHRT_MAX) {
-        core_util_critical_section_exit();
-        MBED_ERROR1(MBED_MAKE_ERROR(MBED_MODULE_PLATFORM, MBED_ERROR_CODE_OVERFLOW), "Rom write never lock overflow (> USHRT_MAX)", mem_wn_lock);
-    }
+    MBED_ASSERT(mem_wn_lock != USHRT_MAX);
     if (mem_wn_lock == 0) {
         mbed_mpu_enable_rom_wn(false);
     }
@@ -68,13 +62,12 @@ void mbed_mpu_manager_lock_rom_write()
 void mbed_mpu_manager_unlock_rom_write()
 {
     core_util_critical_section_enter();
-    if (mem_wn_lock == 0) {
-        core_util_critical_section_exit();
-        MBED_ERROR1(MBED_MAKE_ERROR(MBED_MODULE_PLATFORM, MBED_ERROR_CODE_UNDERFLOW), "Rom write never lock underflow (< 0)", mem_wn_lock);
-    }
+    MBED_ASSERT(mem_wn_lock != 0);
     mem_wn_lock--;
     if (mem_wn_lock == 0) {
         mbed_mpu_enable_rom_wn(true);
     }
     core_util_critical_section_exit();
 }
+
+#endif

platform/mbed_mpu_mgmt.h

@@ -32,6 +32,8 @@
 extern "C" {
 #endif
 
+#if DEVICE_MPU
+
 /** Lock ram execute never mode off
  *
  * This disables the MPU's execute never ram protection and allows
@@ -80,6 +82,18 @@ void mbed_mpu_manager_lock_rom_write(void);
  */
 void mbed_mpu_manager_unlock_rom_write(void);
 
+#else
+
+#define mbed_mpu_manager_lock_ram_execution() (void)0
+
+#define mbed_mpu_manager_unlock_ram_execution() (void)0
+
+#define mbed_mpu_manager_lock_rom_write() (void)0
+
+#define mbed_mpu_manager_unlock_rom_write() (void)0
+
+#endif
+
 #ifdef __cplusplus
 }
 #endif

rtos/TARGET_CORTEX/mbed_boot.c

@@ -89,8 +89,6 @@ uint32_t mbed_stack_isr_size = 0;
 void mbed_init(void)
 {
     mbed_mpu_init();
-    mbed_mpu_enable_ram_xn(true);
-    mbed_mpu_enable_rom_wn(true);
     mbed_cpy_nvic();
     mbed_sdk_init();
     mbed_rtos_init();