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https://github.com/FreeRTOS/FreeRTOS-Kernel.git
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Pre-allocate secure-side context structures
This commit improves ARMv8-M security by pre-allocating secure-side task context structures and changing how tasks reference a secure-side context structure when calling a secure function. The new configuration constant secureconfigMAX_SECURE_CONTEXTS sets the number of secure context structures to pre-allocate. secureconfigMAX_SECURE_CONTEXTS defaults to 8 if left undefined. Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>
This commit is contained in:
Gaurav Aggarwal
Gaurav-Aggarwal-AWS
parent
f8ada39d85
commit
ccaa0f4d6e
27 changed files with 1012 additions and 657 deletions
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@ -50,25 +50,74 @@
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* Bit[1] - 1 --> Thread mode uses PSP.
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*/
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#define securecontextCONTROL_VALUE_UNPRIVILEGED 0x03
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/**
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* @brief Invalid context ID.
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*/
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#define securecontextINVALID_CONTEXT_ID 0UL
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/**
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* @brief Maximum number of secure contexts.
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*/
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#ifndef secureconfigMAX_SECURE_CONTEXTS
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#define secureconfigMAX_SECURE_CONTEXTS 8UL
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#endif
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/*-----------------------------------------------------------*/
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/**
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* @brief Structure to represent secure context.
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*
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* @note Since stack grows down, pucStackStart is the highest address while
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* pucStackLimit is the first addess of the allocated memory.
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* @brief Pre-allocated array of secure contexts.
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*/
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typedef struct SecureContext
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SecureContext_t xSecureContexts[ secureconfigMAX_SECURE_CONTEXTS ];
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/*-----------------------------------------------------------*/
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/**
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* @brief Get a free context from the secure context pool (xSecureContexts).
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*
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* @return Index of a free context in the xSecureContexts array.
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*/
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static uint32_t ulGetSecureContext( void );
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/**
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* @brief Return the secure context to the secure context pool (xSecureContexts).
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*
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* @param[in] ulSecureContextIndex Index of the context in the xSecureContexts array.
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*/
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static void vReturnSecureContext( uint32_t ulSecureContextIndex );
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/* These are implemented in assembly. */
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extern void SecureContext_LoadContextAsm( SecureContext_t * pxSecureContext );
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extern void SecureContext_SaveContextAsm( SecureContext_t * pxSecureContext );
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/*-----------------------------------------------------------*/
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static uint32_t ulGetSecureContext( void )
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{
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uint8_t * pucCurrentStackPointer; /**< Current value of stack pointer (PSP). */
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uint8_t * pucStackLimit; /**< Last location of the stack memory (PSPLIM). */
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uint8_t * pucStackStart; /**< First location of the stack memory. */
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} SecureContext_t;
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uint32_t ulSecureContextIndex;
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for( ulSecureContextIndex = 0; ulSecureContextIndex < secureconfigMAX_SECURE_CONTEXTS; ulSecureContextIndex++ )
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{
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if( ( xSecureContexts[ ulSecureContextIndex ].pucCurrentStackPointer == NULL ) &&
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( xSecureContexts[ ulSecureContextIndex ].pucStackLimit == NULL ) &&
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( xSecureContexts[ ulSecureContextIndex ].pucStackStart == NULL ) )
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{
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break;
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}
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}
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return ulSecureContextIndex;
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}
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/*-----------------------------------------------------------*/
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static void vReturnSecureContext( uint32_t ulSecureContextIndex )
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{
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xSecureContexts[ ulSecureContextIndex ].pucCurrentStackPointer = NULL;
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xSecureContexts[ ulSecureContextIndex ].pucStackLimit = NULL;
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xSecureContexts[ ulSecureContextIndex ].pucStackStart = NULL;
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}
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/*-----------------------------------------------------------*/
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secureportNON_SECURE_CALLABLE void SecureContext_Init( void )
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{
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uint32_t ulIPSR;
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uint32_t ulIPSR, i;
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/* Read the Interrupt Program Status Register (IPSR) value. */
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secureportREAD_IPSR( ulIPSR );
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@ -81,6 +130,14 @@ secureportNON_SECURE_CALLABLE void SecureContext_Init( void )
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secureportSET_PSPLIM( securecontextNO_STACK );
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secureportSET_PSP( securecontextNO_STACK );
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/* Initialize all secure contexts. */
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for( i = 0; i < secureconfigMAX_SECURE_CONTEXTS; i++ )
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{
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xSecureContexts[ i ].pucCurrentStackPointer = NULL;
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xSecureContexts[ i ].pucStackLimit = NULL;
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xSecureContexts[ i ].pucStackStart = NULL;
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}
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#if ( configENABLE_MPU == 1 )
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{
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/* Configure thread mode to use PSP and to be unprivileged. */
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@ -88,7 +145,7 @@ secureportNON_SECURE_CALLABLE void SecureContext_Init( void )
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}
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#else /* configENABLE_MPU */
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{
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/* Configure thread mode to use PSP and to be privileged.. */
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/* Configure thread mode to use PSP and to be privileged. */
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secureportSET_CONTROL( securecontextCONTROL_VALUE_PRIVILEGED );
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}
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#endif /* configENABLE_MPU */
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@ -104,8 +161,8 @@ secureportNON_SECURE_CALLABLE void SecureContext_Init( void )
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#endif /* configENABLE_MPU */
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{
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uint8_t * pucStackMemory = NULL;
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uint32_t ulIPSR;
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SecureContextHandle_t xSecureContextHandle = NULL;
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uint32_t ulIPSR, ulSecureContextIndex;
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SecureContextHandle_t xSecureContextHandle;
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#if ( configENABLE_MPU == 1 )
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uint32_t * pulCurrentStackPointer = NULL;
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@ -118,10 +175,11 @@ secureportNON_SECURE_CALLABLE void SecureContext_Init( void )
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* when the processor is running in the Thread Mode. */
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if( ulIPSR != 0 )
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{
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/* Allocate the context structure. */
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xSecureContextHandle = ( SecureContextHandle_t ) pvPortMalloc( sizeof( SecureContext_t ) );
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/* Ontain a free secure context. */
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ulSecureContextIndex = ulGetSecureContext();
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if( xSecureContextHandle != NULL )
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/* Were we able to get a free context? */
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if( ulSecureContextIndex < secureconfigMAX_SECURE_CONTEXTS )
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{
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/* Allocate the stack space. */
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pucStackMemory = pvPortMalloc( ulSecureStackSize );
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@ -134,18 +192,18 @@ secureportNON_SECURE_CALLABLE void SecureContext_Init( void )
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* pointer before writing i.e. if stack pointer is 0x2, a push
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* operation will decrement the stack pointer to 0x1 and then
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* write at 0x1. */
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xSecureContextHandle->pucStackStart = pucStackMemory + ulSecureStackSize;
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xSecureContexts[ ulSecureContextIndex ].pucStackStart = pucStackMemory + ulSecureStackSize;
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/* The stack cannot go beyond this location. This value is
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* programmed in the PSPLIM register on context switch.*/
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xSecureContextHandle->pucStackLimit = pucStackMemory;
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xSecureContexts[ ulSecureContextIndex ].pucStackLimit = pucStackMemory;
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#if ( configENABLE_MPU == 1 )
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{
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/* Store the correct CONTROL value for the task on the stack.
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* This value is programmed in the CONTROL register on
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* context switch. */
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pulCurrentStackPointer = ( uint32_t * ) xSecureContextHandle->pucStackStart;
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pulCurrentStackPointer = ( uint32_t * ) xSecureContexts[ ulSecureContextIndex ].pucStackStart;
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pulCurrentStackPointer--;
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if( ulIsTaskPrivileged )
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@ -159,22 +217,22 @@ secureportNON_SECURE_CALLABLE void SecureContext_Init( void )
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/* Store the current stack pointer. This value is programmed in
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* the PSP register on context switch. */
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xSecureContextHandle->pucCurrentStackPointer = ( uint8_t * ) pulCurrentStackPointer;
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xSecureContexts[ ulSecureContextIndex ].pucCurrentStackPointer = ( uint8_t * ) pulCurrentStackPointer;
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}
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#else /* configENABLE_MPU */
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{
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/* Current SP is set to the starting of the stack. This
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* value programmed in the PSP register on context switch. */
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xSecureContextHandle->pucCurrentStackPointer = xSecureContextHandle->pucStackStart;
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xSecureContexts[ ulSecureContextIndex ].pucCurrentStackPointer = xSecureContexts[ ulSecureContextIndex ].pucStackStart;
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}
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#endif /* configENABLE_MPU */
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/* Ensure to never return 0 as a valid context handle. */
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xSecureContextHandle = ulSecureContextIndex + 1UL;
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}
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else
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{
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/* Free the context to avoid memory leak and make sure to return
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* NULL to indicate failure. */
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vPortFree( xSecureContextHandle );
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xSecureContextHandle = NULL;
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xSecureContextHandle = securecontextINVALID_CONTEXT_ID;
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}
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}
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}
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@ -185,7 +243,7 @@ secureportNON_SECURE_CALLABLE void SecureContext_Init( void )
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secureportNON_SECURE_CALLABLE void SecureContext_FreeContext( SecureContextHandle_t xSecureContextHandle )
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{
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uint32_t ulIPSR;
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uint32_t ulIPSR, ulSecureContextIndex;
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/* Read the Interrupt Program Status Register (IPSR) value. */
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secureportREAD_IPSR( ulIPSR );
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@ -194,14 +252,43 @@ secureportNON_SECURE_CALLABLE void SecureContext_FreeContext( SecureContextHandl
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* when the processor is running in the Thread Mode. */
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if( ulIPSR != 0 )
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{
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/* Ensure that valid parameters are passed. */
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secureportASSERT( xSecureContextHandle != NULL );
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/* Only free if a valid context handle is passed. */
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if( ( xSecureContextHandle > 0UL ) && ( xSecureContextHandle <= secureconfigMAX_SECURE_CONTEXTS ) )
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{
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ulSecureContextIndex = xSecureContextHandle - 1UL;
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/* Free the stack space. */
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vPortFree( xSecureContextHandle->pucStackLimit );
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/* Free the stack space. */
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vPortFree( xSecureContexts[ ulSecureContextIndex ].pucStackLimit );
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/* Free the context itself. */
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vPortFree( xSecureContextHandle );
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/* Return the context back to the free contexts pool. */
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vReturnSecureContext( ulSecureContextIndex );
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}
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}
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}
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/*-----------------------------------------------------------*/
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secureportNON_SECURE_CALLABLE void SecureContext_LoadContext( SecureContextHandle_t xSecureContextHandle )
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{
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uint32_t ulSecureContextIndex;
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if( ( xSecureContextHandle > 0UL ) && ( xSecureContextHandle <= secureconfigMAX_SECURE_CONTEXTS ) )
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{
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ulSecureContextIndex = xSecureContextHandle - 1UL;
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SecureContext_LoadContextAsm( &( xSecureContexts[ ulSecureContextIndex ] ) );
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}
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}
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/*-----------------------------------------------------------*/
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secureportNON_SECURE_CALLABLE void SecureContext_SaveContext( SecureContextHandle_t xSecureContextHandle )
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{
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uint32_t ulSecureContextIndex;
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if( ( xSecureContextHandle > 0UL ) && ( xSecureContextHandle <= secureconfigMAX_SECURE_CONTEXTS ) )
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{
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ulSecureContextIndex = xSecureContextHandle - 1UL;
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SecureContext_SaveContextAsm( &( xSecureContexts[ ulSecureContextIndex ] ) );
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}
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}
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/*-----------------------------------------------------------*/
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@ -36,15 +36,29 @@
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#include "FreeRTOSConfig.h"
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/**
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* @brief PSP value when no task's context is loaded.
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* @brief PSP value when no secure context is loaded.
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*/
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#define securecontextNO_STACK 0x0
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/*-----------------------------------------------------------*/
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/**
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* @brief Opaque handle.
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* @brief Structure to represent a secure context.
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*
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* @note Since stack grows down, pucStackStart is the highest address while
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* pucStackLimit is the first address of the allocated memory.
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*/
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struct SecureContext;
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typedef struct SecureContext * SecureContextHandle_t;
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typedef struct SecureContext
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{
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uint8_t * pucCurrentStackPointer; /**< Current value of stack pointer (PSP). */
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uint8_t * pucStackLimit; /**< Last location of the stack memory (PSPLIM). */
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uint8_t * pucStackStart; /**< First location of the stack memory. */
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} SecureContext_t;
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/*-----------------------------------------------------------*/
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/**
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* @brief Opaque handle for a secure context.
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*/
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typedef uint32_t SecureContextHandle_t;
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/*-----------------------------------------------------------*/
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/**
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@ -32,57 +32,62 @@
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/* Secure port macros. */
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#include "secure_port_macros.h"
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secureportNON_SECURE_CALLABLE void SecureContext_LoadContext( SecureContextHandle_t xSecureContextHandle )
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void SecureContext_LoadContextAsm( SecureContext_t * pxSecureContext )
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{
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/* xSecureContextHandle value is in r0. */
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/* pxSecureContext value is in r0. */
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__asm volatile
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(
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" .syntax unified \n"
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" \n"
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" mrs r1, ipsr \n"/* r1 = IPSR. */
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" cbz r1, load_ctx_therad_mode \n"/* Do nothing if the processor is running in the Thread Mode. */
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" ldmia r0!, {r1, r2} \n"/* r1 = xSecureContextHandle->pucCurrentStackPointer, r2 = xSecureContextHandle->pucStackLimit. */
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" .syntax unified \n"
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" \n"
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" mrs r1, ipsr \n" /* r1 = IPSR. */
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" cbz r1, load_ctx_therad_mode \n" /* Do nothing if the processor is running in the Thread Mode. */
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" ldmia r0!, {r1, r2} \n" /* r1 = pxSecureContext->pucCurrentStackPointer, r2 = pxSecureContext->pucStackLimit. */
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" \n"
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#if ( configENABLE_MPU == 1 )
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" ldmia r1!, {r3} \n"/* Read CONTROL register value from task's stack. r3 = CONTROL. */
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" msr control, r3 \n"/* CONTROL = r3. */
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" ldmia r1!, {r3} \n" /* Read CONTROL register value from task's stack. r3 = CONTROL. */
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" msr control, r3 \n" /* CONTROL = r3. */
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#endif /* configENABLE_MPU */
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" msr psplim, r2 \n"/* PSPLIM = r2. */
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" msr psp, r1 \n"/* PSP = r1. */
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" \n"
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" load_ctx_therad_mode: \n"
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" nop \n"
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" \n"
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" \n"
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" msr psplim, r2 \n" /* PSPLIM = r2. */
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" msr psp, r1 \n" /* PSP = r1. */
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" \n"
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" load_ctx_therad_mode: \n"
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" bx lr \n"
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" \n"
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::: "r0", "r1", "r2"
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);
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}
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/*-----------------------------------------------------------*/
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secureportNON_SECURE_CALLABLE void SecureContext_SaveContext( SecureContextHandle_t xSecureContextHandle )
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void SecureContext_SaveContextAsm( SecureContext_t * pxSecureContext )
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{
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/* xSecureContextHandle value is in r0. */
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/* pxSecureContext value is in r0. */
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__asm volatile
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(
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" .syntax unified \n"
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" \n"
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" mrs r1, ipsr \n"/* r1 = IPSR. */
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" cbz r1, save_ctx_therad_mode \n"/* Do nothing if the processor is running in the Thread Mode. */
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" mrs r1, psp \n"/* r1 = PSP. */
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" .syntax unified \n"
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" \n"
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" mrs r1, ipsr \n" /* r1 = IPSR. */
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" cbz r1, save_ctx_therad_mode \n" /* Do nothing if the processor is running in the Thread Mode. */
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" mrs r1, psp \n" /* r1 = PSP. */
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" \n"
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#if ( configENABLE_FPU == 1 )
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" vstmdb r1!, {s0} \n"/* Trigger the defferred stacking of FPU registers. */
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" vldmia r1!, {s0} \n"/* Nullify the effect of the pervious statement. */
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" vstmdb r1!, {s0} \n" /* Trigger the defferred stacking of FPU registers. */
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" vldmia r1!, {s0} \n" /* Nullify the effect of the pervious statement. */
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#endif /* configENABLE_FPU */
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" \n"
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#if ( configENABLE_MPU == 1 )
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" mrs r2, control \n"/* r2 = CONTROL. */
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" stmdb r1!, {r2} \n"/* Store CONTROL value on the stack. */
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" mrs r2, control \n" /* r2 = CONTROL. */
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" stmdb r1!, {r2} \n" /* Store CONTROL value on the stack. */
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#endif /* configENABLE_MPU */
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" str r1, [r0] \n"/* Save the top of stack in context. xSecureContextHandle->pucCurrentStackPointer = r1. */
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" movs r1, %0 \n"/* r1 = securecontextNO_STACK. */
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" msr psplim, r1 \n"/* PSPLIM = securecontextNO_STACK. */
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" msr psp, r1 \n"/* PSP = securecontextNO_STACK i.e. No stack for thread mode until next task's context is loaded. */
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" \n"
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" save_ctx_therad_mode: \n"
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" nop \n"
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" \n"
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" \n"
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" str r1, [r0] \n" /* Save the top of stack in context. pxSecureContext->pucCurrentStackPointer = r1. */
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" movs r1, %0 \n" /* r1 = securecontextNO_STACK. */
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" msr psplim, r1 \n" /* PSPLIM = securecontextNO_STACK. */
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" msr psp, r1 \n" /* PSP = securecontextNO_STACK i.e. No stack for thread mode until next task's context is loaded. */
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" \n"
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" save_ctx_therad_mode: \n"
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" bx lr \n"
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" \n"
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::"i" ( securecontextNO_STACK ) : "r1", "memory"
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);
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}
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@ -38,7 +38,9 @@
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/**
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* @brief Total heap size.
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*/
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#define secureconfigTOTAL_HEAP_SIZE ( ( ( size_t ) ( 10 * 1024 ) ) )
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#ifndef secureconfigTOTAL_HEAP_SIZE
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#define secureconfigTOTAL_HEAP_SIZE ( ( ( size_t ) ( 10 * 1024 ) ) )
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#endif
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/* No test marker by default. */
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#ifndef mtCOVERAGE_TEST_MARKER
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