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arm: aarch32: introduce status bit-flag for the MPU region width

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Introduce an additional single-bit flag to hold
the current length of the MPU Stack Guard size
(long or default) for the case when building
with MPU_STACK_GUARD and FPU_SHARING, in Cortex-M
platforms.

In addition, the commit adds some documentation
about the existing status flags in Arm's
thread arch.mode variable.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
This commit is contained in:
Ioannis Glaropoulos 2021-01-29 09:53:06 +01:00 • committed by Anas Nashif
commit e063ba1a52
1 changed files with 20 additions and 0 deletions
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20
include/arch/arm/aarch32/thread.h
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@ -75,6 +75,23 @@ struct _thread_arch {
#endif
#if defined(CONFIG_USERSPACE) || defined(CONFIG_FPU_SHARING)
/*
* Status variable holding several thread status flags
* as follows:
*
* +--------------bit-3----------bit-2--------bit-1---+----bit-0------+
* : | | | | |
* : reserved |<Guard FLOAT>| <FP context> | reserved | <priv mode> |
* : bits | | CONTROL.FPCA | | CONTROL.nPRIV |
* +------------------------------------------------------------------+
*
* Bit 0: thread's current privileged mode (Supervisor or User mode)
* Mirrors CONTROL.nPRIV flag.
* Bit 2: indicating whether the thread has an active FP context.
* Mirrors CONTROL.FPCA flag.
* Bit 3: indicating whether the thread is applying the long (FLOAT)
* or the default MPU stack guard size.
*/
uint32_t mode;
#if defined(CONFIG_USERSPACE)
uint32_t priv_stack_start;
@ -82,6 +99,9 @@ struct _thread_arch {
#endif
};
#if defined(CONFIG_FPU_SHARING) && defined(CONFIG_MPU_STACK_GUARD)
#define Z_ARM_MODE_MPU_GUARD_FLOAT_Msk (1 << 3)
#endif
typedef struct _thread_arch _thread_arch_t;
#endif /* _ASMLANGUAGE */