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@ -51,6 +51,16 @@
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*/
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#define securecontextCONTROL_VALUE_UNPRIVILEGED 0x03
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/**
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* @brief Size of stack seal values in bytes.
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*/
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#define securecontextSTACK_SEAL_SIZE 8
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/**
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* @brief Stack seal value as recommended by ARM.
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*/
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#define securecontextSTACK_SEAL_VALUE 0xFEF5EDA5
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/**
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* @brief Maximum number of secure contexts.
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*/
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@ -204,18 +214,22 @@ secureportNON_SECURE_CALLABLE void SecureContext_Init( void )
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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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pucStackMemory = pvPortMalloc( ulSecureStackSize + securecontextSTACK_SEAL_SIZE );
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if( pucStackMemory != NULL )
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{
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/* Since stack grows down, the starting point will be the last
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* location. Note that this location is next to the last
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* allocated byte because the hardware decrements the stack
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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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* allocated byte for stack (excluding the space for seal values)
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* because the hardware decrements the stack pointer before
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* writing i.e. if stack pointer is 0x2, a push operation will
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* decrement the stack pointer to 0x1 and then write at 0x1. */
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xSecureContexts[ ulSecureContextIndex ].pucStackStart = pucStackMemory + ulSecureStackSize;
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/* Seal the created secure process stack. */
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*( uint32_t * )( pucStackMemory + ulSecureStackSize ) = securecontextSTACK_SEAL_VALUE;
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*( uint32_t * )( pucStackMemory + ulSecureStackSize + 4 ) = securecontextSTACK_SEAL_VALUE;
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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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xSecureContexts[ ulSecureContextIndex ].pucStackLimit = pucStackMemory;
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