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Make sure the mpu_noexec_ram regions has the lowest priority

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From the ARMv7-M ARM section B3.5.3:

	Where there is an overlap between two regions, the register with
	the highest region number takes priority.

We want to make sure the mpu_noexec_ram region has the lowest
priority to allow the mpu_stack_guard region to overwrite the first N
bytes of it.

This change fixes using mpu_noexec_ram and mpu_stack_guard together.
This commit is contained in:
Sören Tempel 2020-02-17 09:37:26 +01:00
parent 5bb3b3dfea
commit 59676a1f5e
2 changed files with 3 additions and 3 deletions
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2
core/sched.c
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@ -121,7 +121,7 @@ int __attribute__((used)) sched_run(void)
#ifdef MODULE_MPU_STACK_GUARD
mpu_configure(
1, /* MPU region 1 */
2, /* MPU region 2 */
(uintptr_t)sched_active_thread->stack_start + 31, /* Base Address (rounded up) */
MPU_ATTR(1, AP_RO_RO, 0, 1, 0, 1, MPU_SIZE_32B) /* Attributes and Size */
);

4
cpu/cortexm_common/vectors_cortexm.c
View File

@ -152,7 +152,7 @@ void reset_handler_default(void)
* executable. This is the Cortex-M SRAM region used for on-chip RAM.
*/
mpu_configure(
2, /* Region 0 and 1 are used by mpu_stack_guard */
0, /* Region 0 (lowest priority) */
(uintptr_t)&_sram, /* RAM base address */
MPU_ATTR(1, AP_RW_RW, 0, 1, 0, 1, MPU_SIZE_512M) /* Allow read/write but no exec */
);
@ -161,7 +161,7 @@ void reset_handler_default(void)
#ifdef MODULE_MPU_STACK_GUARD
if (((uintptr_t)&_sstack) != SRAM_BASE) {
mpu_configure(
0, /* MPU region 0 */
1, /* MPU region 1 */
(uintptr_t)&_sstack + 31, /* Base Address (rounded up) */
MPU_ATTR(1, AP_RO_RO, 0, 1, 0, 1, MPU_SIZE_32B) /* Attributes and Size */
);