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/*
* FreeRTOS Kernel V10.3.0
* Copyright (C) 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
* http://www.FreeRTOS.org
* http://aws.amazon.com/freertos
*
* 1 tab == 4 spaces!
*/
/* Secure context includes. */
#include "secure_context.h"
/* Secure heap includes. */
#include "secure_heap.h"
/* Secure port macros. */
#include "secure_port_macros.h"
/**
* @brief CONTROL value for privileged tasks.
*
* Bit[0] - 0 --> Thread mode is privileged.
* Bit[1] - 1 --> Thread mode uses PSP.
*/
#define securecontextCONTROL_VALUE_PRIVILEGED 0x02
/**
* @brief CONTROL value for un-privileged tasks.
*
* Bit[0] - 1 --> Thread mode is un-privileged.
* Bit[1] - 1 --> Thread mode uses PSP.
*/
#define securecontextCONTROL_VALUE_UNPRIVILEGED 0x03
/*-----------------------------------------------------------*/
/**
* @brief Structure to represent secure context.
*
* @note Since stack grows down, pucStackStart is the highest address while
* pucStackLimit is the first addess of the allocated memory.
*/
typedef struct SecureContext
{
uint8_t *pucCurrentStackPointer; /**< Current value of stack pointer (PSP). */
uint8_t *pucStackLimit; /**< Last location of the stack memory (PSPLIM). */
uint8_t *pucStackStart; /**< First location of the stack memory. */
} SecureContext_t;
/*-----------------------------------------------------------*/
secureportNON_SECURE_CALLABLE void SecureContext_Init( void )
{
uint32_t ulIPSR;
/* Read the Interrupt Program Status Register (IPSR) value. */
secureportREAD_IPSR( ulIPSR );
/* Do nothing if the processor is running in the Thread Mode. IPSR is zero
* when the processor is running in the Thread Mode. */
if( ulIPSR != 0 )
{
/* No stack for thread mode until a task's context is loaded. */
secureportSET_PSPLIM( securecontextNO_STACK );
secureportSET_PSP( securecontextNO_STACK );
#if( configENABLE_MPU == 1 )
{
/* Configure thread mode to use PSP and to be unprivileged. */
secureportSET_CONTROL( securecontextCONTROL_VALUE_UNPRIVILEGED );
}
#else /* configENABLE_MPU */
{
/* Configure thread mode to use PSP and to be privileged.. */
secureportSET_CONTROL( securecontextCONTROL_VALUE_PRIVILEGED );
}
#endif /* configENABLE_MPU */
}
}
/*-----------------------------------------------------------*/
#if( configENABLE_MPU == 1 )
secureportNON_SECURE_CALLABLE SecureContextHandle_t SecureContext_AllocateContext( uint32_t ulSecureStackSize, uint32_t ulIsTaskPrivileged )
#else /* configENABLE_MPU */
secureportNON_SECURE_CALLABLE SecureContextHandle_t SecureContext_AllocateContext( uint32_t ulSecureStackSize )
#endif /* configENABLE_MPU */
{
uint8_t *pucStackMemory = NULL;
uint32_t ulIPSR;
SecureContextHandle_t xSecureContextHandle = NULL;
#if( configENABLE_MPU == 1 )
uint32_t *pulCurrentStackPointer = NULL;
#endif /* configENABLE_MPU */
/* Read the Interrupt Program Status Register (IPSR) value. */
secureportREAD_IPSR( ulIPSR );
/* Do nothing if the processor is running in the Thread Mode. IPSR is zero
* when the processor is running in the Thread Mode. */
if( ulIPSR != 0 )
{
/* Allocate the context structure. */
xSecureContextHandle = ( SecureContextHandle_t ) pvPortMalloc( sizeof( SecureContext_t ) );
if( xSecureContextHandle != NULL )
{
/* Allocate the stack space. */
pucStackMemory = pvPortMalloc( ulSecureStackSize );
if( pucStackMemory != NULL )
{
/* Since stack grows down, the starting point will be the last
* location. Note that this location is next to the last
* allocated byte because the hardware decrements the stack
* pointer before writing i.e. if stack pointer is 0x2, a push
* operation will decrement the stack pointer to 0x1 and then
* write at 0x1. */
xSecureContextHandle->pucStackStart = pucStackMemory + ulSecureStackSize;
/* The stack cannot go beyond this location. This value is
* programmed in the PSPLIM register on context switch.*/
xSecureContextHandle->pucStackLimit = pucStackMemory;
#if( configENABLE_MPU == 1 )
{
/* Store the correct CONTROL value for the task on the stack.
* This value is programmed in the CONTROL register on
* context switch. */
pulCurrentStackPointer = ( uint32_t * ) xSecureContextHandle->pucStackStart;
pulCurrentStackPointer--;
if( ulIsTaskPrivileged )
{
*( pulCurrentStackPointer ) = securecontextCONTROL_VALUE_PRIVILEGED;
}
else
{
*( pulCurrentStackPointer ) = securecontextCONTROL_VALUE_UNPRIVILEGED;
}
/* Store the current stack pointer. This value is programmed in
* the PSP register on context switch. */
xSecureContextHandle->pucCurrentStackPointer = ( uint8_t * ) pulCurrentStackPointer;
}
#else /* configENABLE_MPU */
{
/* Current SP is set to the starting of the stack. This
* value programmed in the PSP register on context switch. */
xSecureContextHandle->pucCurrentStackPointer = xSecureContextHandle->pucStackStart;
}
#endif /* configENABLE_MPU */
}
else
{
/* Free the context to avoid memory leak and make sure to return
* NULL to indicate failure. */
vPortFree( xSecureContextHandle );
xSecureContextHandle = NULL;
}
}
}
return xSecureContextHandle;
}
/*-----------------------------------------------------------*/
secureportNON_SECURE_CALLABLE void SecureContext_FreeContext( SecureContextHandle_t xSecureContextHandle )
{
uint32_t ulIPSR;
/* Read the Interrupt Program Status Register (IPSR) value. */
secureportREAD_IPSR( ulIPSR );
/* Do nothing if the processor is running in the Thread Mode. IPSR is zero
* when the processor is running in the Thread Mode. */
if( ulIPSR != 0 )
{
/* Ensure that valid parameters are passed. */
secureportASSERT( xSecureContextHandle != NULL );
/* Free the stack space. */
vPortFree( xSecureContextHandle->pucStackLimit );
/* Free the context itself. */
vPortFree( xSecureContextHandle );
}
}
/*-----------------------------------------------------------*/
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