armv8.1-m: Add PACBTI support to kernel non-secure implementation

In this commit, Pointer Authentication, and Branch Target
Identification Extension (PACBTI) support is added for
Non-Secure and Non-TrustZone variants of Cortex-M85
FreeRTOS-Kernel Port.

The PACBTI support is added for Arm Compiler For
Embedded, and IAR toolchains only. The support in
the kernel is not yet enabled for GNU toolchain
due to known issues.

Signed-off-by: Ahmed Ismail <[email protected]>

Author: Ahmed Ismail

.github/.cSpellWords.txt

@@ -448,6 +448,7 @@ MAINRDY
 MAIR
 Mang
 Mbits
+mbranch
 mcause
 MCFR
 MCKA
@@ -586,6 +587,8 @@ OWATCOM
 OWDR
 OWER
 OWSR
+pacbti
+PACBTI
 PAGEN
 PCDR
 PCER
@@ -900,6 +903,7 @@ TXTEN
 TXUBR
 TXVC
 TXVDIS
+UBTI
 UDCP
 UNACKED
 uncrustify
@@ -915,6 +919,7 @@ UNSUB
 UNSUBACK
 unsubscriptions
 unsuspended
+UPAC
 URAD
 URAT
 URSTEN

include/FreeRTOS.h

@@ -3032,6 +3032,18 @@
     #define configCONTROL_INFINITE_LOOP()
 #endif
 
+/* Set configENABLE_PAC and/or configENABLE_BTI to 1 to enable PAC and/or BTI
+ * support and 0 to disable them. These are currently used in ARMv8.1-M ports. */
+#if ( portHAS_PACBTI_FEATURE == 1 )
+    #ifndef configENABLE_PAC
+        #define configENABLE_PAC    0
+    #endif
+
+    #ifndef configENABLE_BTI
+        #define configENABLE_BTI    0
+    #endif
+#endif
+
 /* Sometimes the FreeRTOSConfig.h settings only allow a task to be created using
  * dynamically allocated RAM, in which case when any task is deleted it is known
  * that both the task's stack and TCB need to be freed.  Sometimes the

portable/ARMv8M/non_secure/port.c

@@ -1,6 +1,8 @@
 /*
  * FreeRTOS Kernel <DEVELOPMENT BRANCH>
  * Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * Copyright 2024 Arm Limited and/or its affiliates
+ * <[email protected]>
  *
  * SPDX-License-Identifier: MIT
  *
@@ -110,6 +112,7 @@ typedef void ( * portISR_t )( void );
 #define portSCB_VTOR_REG                      ( *( ( portISR_t ** ) 0xe000ed08 ) )
 #define portSCB_SYS_HANDLER_CTRL_STATE_REG    ( *( ( volatile uint32_t * ) 0xe000ed24 ) )
 #define portSCB_MEM_FAULT_ENABLE_BIT          ( 1UL << 16UL )
+#define portSCB_USG_FAULT_ENABLE_BIT          ( 1UL << 18UL )
 /*-----------------------------------------------------------*/
 
 /**
@@ -373,6 +376,20 @@ typedef void ( * portISR_t )( void );
  * any secure calls.
  */
 #define portNO_SECURE_CONTEXT    0
+
+/**
+ * @brief Constants required to check and configure PACBTI security feature implementation.
+ */
+#if ( portHAS_PACBTI_FEATURE == 1 )
+
+    #define portID_ISAR5_REG         ( *( ( volatile uint32_t * ) 0xe000ed74 ) )
+
+    #define portCONTROL_UPAC_EN      ( 1UL << 7UL )
+    #define portCONTROL_PAC_EN       ( 1UL << 6UL )
+    #define portCONTROL_UBTI_EN      ( 1UL << 5UL )
+    #define portCONTROL_BTI_EN       ( 1UL << 4UL )
+
+#endif /* portHAS_PACBTI_FEATURE */
 /*-----------------------------------------------------------*/
 
 /**
@@ -410,6 +427,26 @@ static void prvTaskExitError( void );
     static void prvSetupFPU( void ) PRIVILEGED_FUNCTION;
 #endif /* configENABLE_FPU */
 
+#if ( portHAS_PACBTI_FEATURE == 1 )
+
+/**
+ * @brief Configures PACBTI features.
+ *
+ * This function configures the Pointer Authentication, and Branch Target
+ * Identification security features as per the user configuration. It returns
+ * the value of the special purpose CONTROL register accordingly, and optionally
+ * updates the CONTROL register value. Currently, only Cortex-M85 (ARMv8.1-M
+ * architecture based) target supports PACBTI security feature.
+ *
+ * @param xWriteControlRegister Used to control whether the special purpose
+ * CONTROL register should be updated or not.
+ *
+ * @return CONTROL register value according to the configured PACBTI option.
+ */
+    static uint32_t prvConfigurePACBTI( BaseType_t xWriteControlRegister );
+
+#endif /* portHAS_PACBTI_FEATURE */
+
 /**
  * @brief Setup the timer to generate the tick interrupts.
  *
@@ -1457,6 +1494,7 @@ void vPortSVCHandler_C( uint32_t * pulCallerStackAddress ) /* PRIVILEGED_FUNCTIO
                                          xMPU_SETTINGS * xMPUSettings ) /* PRIVILEGED_FUNCTION */
     {
         uint32_t ulIndex = 0;
+        uint32_t ulControl = 0x0;
 
         xMPUSettings->ulContext[ ulIndex ] = 0x04040404; /* r4. */
         ulIndex++;
@@ -1503,16 +1541,24 @@ void vPortSVCHandler_C( uint32_t * pulCallerStackAddress ) /* PRIVILEGED_FUNCTIO
         xMPUSettings->ulContext[ ulIndex ] = ( uint32_t ) pxEndOfStack;         /* PSPLIM. */
         ulIndex++;
 
+        #if ( portHAS_PACBTI_FEATURE == 1 )
+        {
+            /* Check PACBTI security feature configuration before pushing the
+             * CONTROL register's value on task's TCB. */
+            ulControl = prvConfigurePACBTI( pdFALSE );
+        }
+        #endif /* portHAS_PACBTI_FEATURE */
+
         if( xRunPrivileged == pdTRUE )
         {
             xMPUSettings->ulTaskFlags |= portTASK_IS_PRIVILEGED_FLAG;
-            xMPUSettings->ulContext[ ulIndex ] = ( uint32_t ) portINITIAL_CONTROL_PRIVILEGED; /* CONTROL. */
+            xMPUSettings->ulContext[ ulIndex ] = ( ulControl | ( uint32_t ) portINITIAL_CONTROL_PRIVILEGED ); /* CONTROL. */
             ulIndex++;
         }
         else
         {
             xMPUSettings->ulTaskFlags &= ( ~portTASK_IS_PRIVILEGED_FLAG );
-            xMPUSettings->ulContext[ ulIndex ] = ( uint32_t ) portINITIAL_CONTROL_UNPRIVILEGED; /* CONTROL. */
+            xMPUSettings->ulContext[ ulIndex ] = ( ulControl | ( uint32_t ) portINITIAL_CONTROL_UNPRIVILEGED ); /* CONTROL. */
             ulIndex++;
         }
 
@@ -1740,6 +1786,14 @@ BaseType_t xPortStartScheduler( void ) /* PRIVILEGED_FUNCTION */
     portNVIC_SHPR3_REG |= portNVIC_SYSTICK_PRI;
     portNVIC_SHPR2_REG = 0;
 
+    #if ( portHAS_PACBTI_FEATURE == 1 )
+    {
+        /* Set the CONTROL register value based on PACBTI security feature
+         * configuration before starting the first task. */
+        ( void) prvConfigurePACBTI( pdTRUE );
+    }
+    #endif /* portHAS_PACBTI_FEATURE */
+
     #if ( configENABLE_MPU == 1 )
     {
         /* Setup the Memory Protection Unit (MPU). */
@@ -2158,3 +2212,42 @@ BaseType_t xPortIsInsideInterrupt( void )
 
 #endif /* #if ( ( configENABLE_MPU == 1 ) && ( configUSE_MPU_WRAPPERS_V1 == 0 ) ) */
 /*-----------------------------------------------------------*/
+
+#if ( portHAS_PACBTI_FEATURE == 1 )
+
+    static uint32_t prvConfigurePACBTI( BaseType_t xWriteControlRegister )
+    {
+        uint32_t ulControl = 0x0;
+
+        /* Ensure that PACBTI is implemented. */
+        configASSERT( portID_ISAR5_REG != 0x0 );
+
+        /* Enable UsageFault exception if PAC or BTI is enabled. */
+        #if( ( configENABLE_PAC == 1 ) || ( configENABLE_BTI == 1 ) )
+        {
+            portSCB_SYS_HANDLER_CTRL_STATE_REG |= portSCB_USG_FAULT_ENABLE_BIT;
+        }
+        #endif
+
+        #if( configENABLE_PAC == 1 )
+        {
+            ulControl |= ( portCONTROL_UPAC_EN | portCONTROL_PAC_EN );
+        }
+        #endif
+
+        #if( configENABLE_BTI == 1 )
+        {
+            ulControl |= ( portCONTROL_UBTI_EN | portCONTROL_BTI_EN );
+        }
+        #endif
+
+        if( xWriteControlRegister == pdTRUE )
+        {
+            __asm volatile ( "msr control, %0" : : "r" ( ulControl ) );
+        }
+
+        return ulControl;
+    }
+
+#endif /* #if ( portHAS_PACBTI_FEATURE == 1 ) */
+/*-----------------------------------------------------------*/

portable/ARMv8M/non_secure/portable/GCC/ARM_CM23/portmacro.h

@@ -1,6 +1,8 @@
 /*
  * FreeRTOS Kernel <DEVELOPMENT BRANCH>
  * Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * Copyright 2024 Arm Limited and/or its affiliates
+ * <[email protected]>
  *
  * SPDX-License-Identifier: MIT
  *
@@ -51,6 +53,7 @@
 #define portARCH_NAME                    "Cortex-M23"
 #define portHAS_ARMV8M_MAIN_EXTENSION    0
 #define portARMV8M_MINOR_VERSION         0
+#define portHAS_PACBTI_FEATURE           0
 #define portDONT_DISCARD                 __attribute__( ( used ) )
 /*-----------------------------------------------------------*/
 

portable/ARMv8M/non_secure/portable/GCC/ARM_CM23_NTZ/portmacro.h

@@ -1,6 +1,8 @@
 /*
  * FreeRTOS Kernel <DEVELOPMENT BRANCH>
  * Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * Copyright 2024 Arm Limited and/or its affiliates
+ * <[email protected]>
  *
  * SPDX-License-Identifier: MIT
  *
@@ -51,6 +53,7 @@
 #define portARCH_NAME                    "Cortex-M23"
 #define portHAS_ARMV8M_MAIN_EXTENSION    0
 #define portARMV8M_MINOR_VERSION         0
+#define portHAS_PACBTI_FEATURE           0
 #define portDONT_DISCARD                 __attribute__( ( used ) )
 /*-----------------------------------------------------------*/
 

portable/ARMv8M/non_secure/portable/GCC/ARM_CM33/portmacro.h

@@ -1,6 +1,8 @@
 /*
  * FreeRTOS Kernel <DEVELOPMENT BRANCH>
  * Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * Copyright 2024 Arm Limited and/or its affiliates
+ * <[email protected]>
  *
  * SPDX-License-Identifier: MIT
  *
@@ -51,6 +53,7 @@
 #define portARCH_NAME                    "Cortex-M33"
 #define portHAS_ARMV8M_MAIN_EXTENSION    1
 #define portARMV8M_MINOR_VERSION         0
+#define portHAS_PACBTI_FEATURE           0
 #define portDONT_DISCARD                 __attribute__( ( used ) )
 /*-----------------------------------------------------------*/
 

portable/ARMv8M/non_secure/portable/GCC/ARM_CM33_NTZ/portmacro.h

@@ -1,6 +1,8 @@
 /*
  * FreeRTOS Kernel <DEVELOPMENT BRANCH>
  * Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * Copyright 2024 Arm Limited and/or its affiliates
+ * <[email protected]>
  *
  * SPDX-License-Identifier: MIT
  *
@@ -51,6 +53,7 @@
 #define portARCH_NAME                    "Cortex-M33"
 #define portHAS_ARMV8M_MAIN_EXTENSION    1
 #define portARMV8M_MINOR_VERSION         0
+#define portHAS_PACBTI_FEATURE           0
 #define portDONT_DISCARD                 __attribute__( ( used ) )
 /*-----------------------------------------------------------*/
 

portable/ARMv8M/non_secure/portable/GCC/ARM_CM35P/portmacro.h

@@ -1,6 +1,8 @@
 /*
  * FreeRTOS Kernel <DEVELOPMENT BRANCH>
  * Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * Copyright 2024 Arm Limited and/or its affiliates
+ * <[email protected]>
  *
  * SPDX-License-Identifier: MIT
  *
@@ -51,6 +53,7 @@
 #define portARCH_NAME                    "Cortex-M35P"
 #define portHAS_ARMV8M_MAIN_EXTENSION    1
 #define portARMV8M_MINOR_VERSION         0
+#define portHAS_PACBTI_FEATURE           0
 #define portDONT_DISCARD                 __attribute__( ( used ) )
 /*-----------------------------------------------------------*/
 

portable/ARMv8M/non_secure/portable/GCC/ARM_CM55/portmacro.h

@@ -1,6 +1,8 @@
 /*
  * FreeRTOS Kernel <DEVELOPMENT BRANCH>
  * Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * Copyright 2024 Arm Limited and/or its affiliates
+ * <[email protected]>
  *
  * SPDX-License-Identifier: MIT
  *
@@ -56,6 +58,7 @@
 #define portARCH_NAME                    "Cortex-M55"
 #define portHAS_ARMV8M_MAIN_EXTENSION    1
 #define portARMV8M_MINOR_VERSION         1
+#define portHAS_PACBTI_FEATURE           0
 #define portDONT_DISCARD                 __attribute__( ( used ) )
 /*-----------------------------------------------------------*/
 

portable/ARMv8M/non_secure/portable/GCC/ARM_CM85/portmacro.h

@@ -1,6 +1,8 @@
 /*
  * FreeRTOS Kernel <DEVELOPMENT BRANCH>
  * Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * Copyright 2024 Arm Limited and/or its affiliates
+ * <[email protected]>
  *
  * SPDX-License-Identifier: MIT
  *
@@ -56,6 +58,7 @@
 #define portARCH_NAME                    "Cortex-M85"
 #define portHAS_ARMV8M_MAIN_EXTENSION    1
 #define portARMV8M_MINOR_VERSION         1
+#define portHAS_PACBTI_FEATURE           1
 #define portDONT_DISCARD                 __attribute__( ( used ) )
 /*-----------------------------------------------------------*/