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arch32: Fix incorrect exc_exit sequence

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The incorrect sequence will cause the thread cannot be aborted in the
ISR context. The following test case failed:
tests/kernel/fatal/exception/kernel.common.stack_sentinel.

The stack sentinel detects the stack overflow as normal during a timer
ISR exit. Note that, currently, the stack overflow detection is behind
the context switch checking, and then the detection will call svc to
raise a fatal error resulting in increasing the nested counter(+1). At
this point, it needs a context switch to finally abort the thread.
However, after the fatal error handling, the program cannot do a context
switch either during the svc exit[1], or during the timer ISR exit[2].

[1] is because the svc context is in an interrupt nested state (the
nested counter is 2).
[2] is because the current point (after svc context pop out) is right
behind the switch checking.

Signed-off-by: Jaxson Han <jaxson.han@arm.com>
This commit is contained in:
Jaxson Han 2022-03-21 10:10:54 +08:00 • committed by Anas Nashif
commit a7a8a64e9c
1 changed files with 4 additions and 4 deletions
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8
arch/arm/core/aarch32/cortex_a_r/exc_exit.S
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@ -86,6 +86,10 @@ system_thread_exit\@:
*/ */
SECTION_SUBSEC_FUNC(TEXT, _HandlerModeExit, z_arm_int_exit) SECTION_SUBSEC_FUNC(TEXT, _HandlerModeExit, z_arm_int_exit)
#ifdef CONFIG_STACK_SENTINEL
bl z_check_stack_sentinel
#endif /* CONFIG_STACK_SENTINEL */
#ifdef CONFIG_PREEMPT_ENABLED #ifdef CONFIG_PREEMPT_ENABLED
/* Do not context switch if exiting a nested interrupt */ /* Do not context switch if exiting a nested interrupt */
ldr r3, =_kernel ldr r3, =_kernel
@ -100,10 +104,6 @@ SECTION_SUBSEC_FUNC(TEXT, _HandlerModeExit, z_arm_int_exit)
__EXIT_INT: __EXIT_INT:
#endif /* CONFIG_PREEMPT_ENABLED */ #endif /* CONFIG_PREEMPT_ENABLED */
#ifdef CONFIG_STACK_SENTINEL
bl z_check_stack_sentinel
#endif /* CONFIG_STACK_SENTINEL */
/* Disable nested interrupts while exiting */ /* Disable nested interrupts while exiting */
cpsid i cpsid i