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arch: arm: mpu: protect RNR when reading RBAR, RASR in ARMv7-M driver

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We lock IRQs around writing to RNR and immediate reading of RBAR
RASR in ARMv7-M MPU driver. We do this for the functions invoked
directly or undirectly by arch_buffer_validate(). This locking
guarantees that
- arch_buffer_validate() calls by ISRs may safely preempt each
  other
- arch_buffer_validate() calls by threads may safely preempt
  each other (i.e via context switch -out and -in again).

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
This commit is contained in:
Ioannis Glaropoulos 2020-02-13 17:42:23 +01:00 • committed by Andrew Boie
commit f8a5f0330d
1 changed files with 29 additions and 4 deletions
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33
arch/arm/core/aarch32/cortex_m/mpu/arm_mpu_v7_internal.h
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@ -151,8 +151,16 @@ static inline u32_t mpu_region_get_size(u32_t index)
*/ */
static inline int is_enabled_region(u32_t index) static inline int is_enabled_region(u32_t index)
{ {
/* Lock IRQs to ensure RNR value is correct when reading RASR. */
unsigned int key;
u32_t rasr;
key = irq_lock();
MPU->RNR = index; MPU->RNR = index;
return (MPU->RASR & MPU_RASR_ENABLE_Msk) ? 1 : 0; rasr = MPU->RASR;
irq_unlock(key);
return (rasr & MPU_RASR_ENABLE_Msk) ? 1 : 0;
} }
/* Only a single bit is set for all user accessible permissions. /* Only a single bit is set for all user accessible permissions.
@ -169,8 +177,16 @@ static inline int is_enabled_region(u32_t index)
*/ */
static inline u32_t get_region_ap(u32_t r_index) static inline u32_t get_region_ap(u32_t r_index)
{ {
/* Lock IRQs to ensure RNR value is correct when reading RASR. */
unsigned int key;
u32_t rasr;
key = irq_lock();
MPU->RNR = r_index; MPU->RNR = r_index;
return (MPU->RASR & MPU_RASR_AP_Msk) >> MPU_RASR_AP_Pos; rasr = MPU->RASR;
irq_unlock(key);
return (rasr & MPU_RASR_AP_Msk) >> MPU_RASR_AP_Pos;
} }
/** /**
@ -185,9 +201,18 @@ static inline int is_in_region(u32_t r_index, u32_t start, u32_t size)
u32_t r_size_lshift; u32_t r_size_lshift;
u32_t r_addr_end; u32_t r_addr_end;
/* Lock IRQs to ensure RNR value is correct when reading RBAR, RASR. */
unsigned int key;
u32_t rbar, rasr;
key = irq_lock();
MPU->RNR = r_index; MPU->RNR = r_index;
r_addr_start = MPU->RBAR & MPU_RBAR_ADDR_Msk; rbar = MPU->RBAR;
r_size_lshift = ((MPU->RASR & MPU_RASR_SIZE_Msk) >> rasr = MPU->RASR;
irq_unlock(key);
r_addr_start = rbar & MPU_RBAR_ADDR_Msk;
r_size_lshift = ((rasr & MPU_RASR_SIZE_Msk) >>
MPU_RASR_SIZE_Pos) + 1; MPU_RASR_SIZE_Pos) + 1;
r_addr_end = r_addr_start + (1UL << r_size_lshift) - 1; r_addr_end = r_addr_start + (1UL << r_size_lshift) - 1;