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Disallow unprivileged critical sections with MPU wrappers v2 (#1427)

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When using MPU wrappers version 2 (configUSE_MPU_WRAPPERS_V1 == 0),
portRAISE_PRIVILEGE() is a no-op because the portSVC_RAISE_PRIVILEGE
handler is compiled only for MPU wrappers version 1. As a result, an
unprivileged task that calls taskENTER_CRITICAL() does not actually raise
its privilege, so the subsequent BASEPRI write is ignored by the hardware
and the critical section silently fails to mask interrupts. This produces
latent, hard-to-debug faults.

configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is therefore not supported with
MPU wrappers version 2. In the ARMv7-M MPU ports:

- When the option is left undefined under v2, default it to 0 instead of 1
  so the dangerous default configuration is safe.
- When the option is explicitly set to 1 under v2, raise a compile-time
  #error so the unsupported configuration is rejected loudly rather than
  failing silently at run time.

Behaviour for MPU wrappers version 1 is unchanged.
This commit is contained in:
Archit Gupta 2026-06-15 22:30:25 +00:00 committed by GitHub
parent fc25364931
commit 83e56c38ee
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GPG Key ID: B5690EEEBB952194
4 changed files with 48 additions and 8 deletions
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10
portable/GCC/ARM_CM3_MPU/port.c
View File

@ -55,10 +55,20 @@
#define portNVIC_SYSTICK_CLK ( 0 )
#endif
/* Unprivileged critical sections are not supported when using MPU wrappers
* version 2. Default the option to 0 and reject an explicit value of 1. */
#ifndef configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS
#if ( configUSE_MPU_WRAPPERS_V1 == 0 )
#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS 0
#else
#warning "configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is not defined. We recommend defining it to 0 in FreeRTOSConfig.h for better security."
#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS 1
#endif
#else
#if ( ( configUSE_MPU_WRAPPERS_V1 == 0 ) && ( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 ) )
#error configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is not supported with MPU wrappers version 2 ( configUSE_MPU_WRAPPERS_V1 == 0 ).
#endif
#endif
/* Prototype of all Interrupt Service Routines (ISRs). */
typedef void ( * portISR_t )( void );

10
portable/GCC/ARM_CM4_MPU/port.c
View File

@ -59,10 +59,20 @@
#define portNVIC_SYSTICK_CLK ( 0 )
#endif
/* Unprivileged critical sections are not supported when using MPU wrappers
* version 2. Default the option to 0 and reject an explicit value of 1. */
#ifndef configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS
#if ( configUSE_MPU_WRAPPERS_V1 == 0 )
#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS 0
#else
#warning "configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is not defined. We recommend defining it to 0 in FreeRTOSConfig.h for better security."
#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS 1
#endif
#else
#if ( ( configUSE_MPU_WRAPPERS_V1 == 0 ) && ( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 ) )
#error configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is not supported with MPU wrappers version 2 ( configUSE_MPU_WRAPPERS_V1 == 0 ).
#endif
#endif
/* Prototype of all Interrupt Service Routines (ISRs). */
typedef void ( * portISR_t )( void );

10
portable/IAR/ARM_CM4F_MPU/port.c
View File

@ -66,10 +66,20 @@
#define portNVIC_SYSTICK_CLK_BIT ( 0 )
#endif
/* Unprivileged critical sections are not supported when using MPU wrappers
* version 2. Default the option to 0 and reject an explicit value of 1. */
#ifndef configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS
#if ( configUSE_MPU_WRAPPERS_V1 == 0 )
#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS 0
#else
#warning "configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is not defined. We recommend defining it to 0 in FreeRTOSConfig.h for better security."
#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS 1
#endif
#else
#if ( ( configUSE_MPU_WRAPPERS_V1 == 0 ) && ( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 ) )
#error configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is not supported with MPU wrappers version 2 ( configUSE_MPU_WRAPPERS_V1 == 0 ).
#endif
#endif
/* Prototype of all Interrupt Service Routines (ISRs). */
typedef void ( * portISR_t )( void );

10
portable/RVDS/ARM_CM4_MPU/port.c
View File

@ -48,10 +48,20 @@
#undef MPU_WRAPPERS_INCLUDED_FROM_API_FILE
/* Unprivileged critical sections are not supported when using MPU wrappers
* version 2. Default the option to 0 and reject an explicit value of 1. */
#ifndef configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS
#if ( configUSE_MPU_WRAPPERS_V1 == 0 )
#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS 0
#else
#warning "configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is not defined. We recommend defining it to 0 in FreeRTOSConfig.h for better security."
#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS 1
#endif
#else
#if ( ( configUSE_MPU_WRAPPERS_V1 == 0 ) && ( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 ) )
#error configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is not supported with MPU wrappers version 2 ( configUSE_MPU_WRAPPERS_V1 == 0 ).
#endif
#endif
/* Prototype of all Interrupt Service Routines (ISRs). */
typedef void ( * portISR_t )( void );