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Fix portSWITCH_TO_USER_MODE() on Armv7-M MPU ports (#803)

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A task's privilege level is stored in ulTaskFlag member in the TCB. Current
implementation of portSWITCH_TO_USER_MODE() does not update this
flag but just lowers the processor's privilege level. This results in many
APIs incorrectly determining task's privilege level and access permissions -

- xPortIsAuthorizedToAccessBuffer
- xPortIsTaskPrivileged
- xPortIsAuthorizedToAccessKernelObject

This PR fixes the portSWITCH_TO_USER_MODE() implementation to correctly
update the ulTaskFlag member in the TCB before lowering the processor's
privilege level.
This commit is contained in:
Soren Ptak 2023-09-26 02:06:23 -07:00 • committed by GitHub
parent ac5deb155d
commit 84bdb05bd2
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8 changed files with 131 additions and 45 deletions
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20
portable/IAR/ARM_CM4F_MPU/port.c
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@ -283,6 +283,11 @@ extern void vPortRestoreContextOfFirstTask( void ) PRIVILEGED_FUNCTION;
*/
BaseType_t xPortIsTaskPrivileged( void ) PRIVILEGED_FUNCTION;
/**
* @brief Make a task unprivileged.
*/
void vPortSwitchToUserMode( void );
/*-----------------------------------------------------------*/
/* Each task maintains its own interrupt status in the critical nesting
@ -318,7 +323,7 @@ StackType_t * pxPortInitialiseStack( StackType_t * pxTopOfStack,
}
else
{
xMPUSettings->ulTaskFlags &= ( ~portTASK_IS_PRIVILEGED_FLAG );
xMPUSettings->ulTaskFlags &= ( ~( portTASK_IS_PRIVILEGED_FLAG ) );
xMPUSettings->ulContext[ 0 ] = portINITIAL_CONTROL_IF_UNPRIVILEGED;
}
@ -741,6 +746,19 @@ BaseType_t xPortIsTaskPrivileged( void ) /* PRIVILEGED_FUNCTION */
}
/*-----------------------------------------------------------*/
void vPortSwitchToUserMode( void )
{
/* Load the current task's MPU settings from its TCB. */
xMPU_SETTINGS * xTaskMpuSettings = xTaskGetMPUSettings( NULL );
/* Mark the task as unprivileged. */
xTaskMpuSettings->ulTaskFlags &= ( ~( portTASK_IS_PRIVILEGED_FLAG ) );
/* Lower the processor's privilege level. */
vResetPrivilege();
}
/*-----------------------------------------------------------*/
/*
* See header file for description.
*/