bsps/atsam: Add NULL pointer protection

5 files changed, 28 insertions, 2 deletions

diff --git a/bsps/arm/atsam/README b/bsps/arm/atsam/README
index 2ebaa726c8..47aa11d2c0 100644
--- a/bsps/arm/atsam/README
+++ b/bsps/arm/atsam/README
@@ -59,9 +59,13 @@ Use ATSAM_CONSOLE_DEVICE_INDEX=XYZ to set the device index for /dev/console
 Use ATSAM_CONSOLE_USE_INTERRUPTS=XYZ to set the use interrupt driven mode for
 console devices (used by default).
 
-Use ATSAM_MEMORY_TCM_SIZE=XYZ to set the size of tightly coupled memories (TCM)
+Use ATSAM_MEMORY_NULL_SIZE=XYZ to set the size of NULL pointer protection area
 in bytes (default 0x00000000).
 
+Use ATSAM_MEMORY_TCM_SIZE=XYZ to set the size of tightly coupled memories (TCM)
+in bytes (default 0x00000000). Note: ITCM is reduced by the
+ATSAM_MEMORY_NULL_SIZE.
+
 Use ATSAM_MEMORY_INTFLASH_SIZE=XYZ to set the size of internal flash in bytes
 (default is derived from chip variant).
 
diff --git a/bsps/arm/atsam/contrib/libraries/libboard/source/board_lowlevel.c b/bsps/arm/atsam/contrib/libraries/libboard/source/board_lowlevel.c
index cbdf41ba73..a2dd595fb5 100644
--- a/bsps/arm/atsam/contrib/libraries/libboard/source/board_lowlevel.c
+++ b/bsps/arm/atsam/contrib/libraries/libboard/source/board_lowlevel.c
@@ -347,6 +347,23 @@ void _SetupMemoryRegion(void)
 	SCB->SHCSR |= (SCB_SHCSR_MEMFAULTENA_Msk | SCB_SHCSR_BUSFAULTENA_Msk
 				   | SCB_SHCSR_USGFAULTENA_Msk);
 
+#ifdef __rtems__
+	dwRegionBaseAddr =
+		((uintptr_t)atsam_memory_null_begin) |
+		MPU_REGION_VALID |
+		MPU_NULL_REGION;
+	if (atsam_memory_null_begin != atsam_memory_itcm_end) {
+		dwRegionAttr =
+			MPU_AP_NO_ACCESS |
+			MPU_REGION_EXECUTE_NEVER |
+			MPU_CalMPURegionSize((uintptr_t)atsam_memory_null_size) |
+			MPU_REGION_ENABLE;
+	} else {
+		dwRegionAttr = MPU_REGION_DISABLE;
+	}
+	MPU_SetRegion(dwRegionBaseAddr, dwRegionAttr);
+#endif /* __rtems__ */
+
 	/* Enable the MPU region */
 #ifndef __rtems__
 	MPU_Enable(MPU_ENABLE | MPU_PRIVDEFENA);
diff --git a/bsps/arm/atsam/include/bsp.h b/bsps/arm/atsam/include/bsp.h
index 8fe98be364..0bca3d2c22 100644
--- a/bsps/arm/atsam/include/bsp.h
+++ b/bsps/arm/atsam/include/bsp.h
@@ -89,6 +89,10 @@ typedef struct {
   uint8_t phy_addr;
 } if_atsam_config;
 
+extern char atsam_memory_null_begin[];
+extern char atsam_memory_null_end[];
+extern char atsam_memory_null_size[];
+
 extern char atsam_memory_dtcm_begin[];
 extern char atsam_memory_dtcm_end[];
 extern char atsam_memory_dtcm_size[];
diff --git a/bsps/arm/atsam/include/libchip/include/mpu.h b/bsps/arm/atsam/include/libchip/include/mpu.h
index a5d00a681b..034ba58474 100644
--- a/bsps/arm/atsam/include/libchip/include/mpu.h
+++ b/bsps/arm/atsam/include/libchip/include/mpu.h
@@ -56,6 +56,7 @@
 #endif
 #define MPU_SYSTEM_REGION                       (12)
 #ifdef __rtems__
+#define MPU_NULL_REGION                         (13)
 /* Reserve the region with highest priority for user applications */
 #define MPU_USER_DEFINED_REGION                 (15)
 #endif /* __rtems__ */
diff --git a/bsps/arm/atsam/start/bspstarthooks.c b/bsps/arm/atsam/start/bspstarthooks.c
index 516b86228d..2be2fc050b 100644
--- a/bsps/arm/atsam/start/bspstarthooks.c
+++ b/bsps/arm/atsam/start/bspstarthooks.c
@@ -106,7 +106,7 @@ static void configure_tcm(void)
   uintptr_t tcm_size;
   uint32_t itcmcr_sz;
 
-  tcm_size = (uintptr_t) atsam_memory_itcm_size;
+  tcm_size = (uintptr_t) atsam_memory_dtcm_size;
   itcmcr_sz = (SCB->ITCMCR & SCB_ITCMCR_SZ_Msk) >> SCB_ITCMCR_SZ_Pos;
 
   if (tcm_setup_and_check_if_do_efc_config(tcm_size, itcmcr_sz)) {