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arch: arc: add extra handling about exception raised in interrupt

exception, different with irq offload,  may be raised interrupt
handling, e.g.
  * z_check_stack_sentinel
  * wrong code

we need to add specific handling of this case in exception handling

Signed-off-by: Wayne Ren <>
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vonhust authored and ioannisg committed Aug 9, 2019
1 parent 484b923 commit 61d570bb38b9ba689d4ca0b0d35d04710e95a546
Showing with 29 additions and 5 deletions.
  1. +29 −5 arch/arc/core/fault_s.S
@@ -96,6 +96,13 @@ _exc_entry:
jl _Fault

/* the exception cause must be fixed in exception handler when exception returns
* directly, or exception will be repeated.
* If thread switch is raised in exception handler, the context of old thread will
* not be saved, i.e., it cannot be recovered, because we don't know where the
* exception comes out, thread context?irq_context?nest irq context?

@@ -129,15 +136,32 @@ _exc_return:
/* sflag instruction is not supported in current ARC GNU */
.long 0x00ff302f
/* clear AE bit to forget this was an exception */
/* clear AE bit to forget this was an exception, and go to
* register bank0 (if exception is raised in firq with 2 reg
* banks, then we may be bank1)
/* save r2 in ilink because of the possible following reg
* bank switch
mov ilink, r2
lr r3, [_ARC_V2_STATUS32]
and r3,r3,(~_ARC_V2_STATUS32_AE)
and r3,r3,(~(_ARC_V2_STATUS32_AE | _ARC_V2_STATUS32_RB(7)))
kflag r3
/* pretend lowest priority interrupt happened to use common handler */
lr r3, [_ARC_V2_AUX_IRQ_ACT]
or r3,r3,(1 << (CONFIG_NUM_IRQ_PRIO_LEVELS - 1)) /* use lowest */
/* pretend lowest priority interrupt happened to use common handler
* if exception is raised in irq, i.e., _ARC_V2_AUX_IRQ_ACT !=0,
* ignore irq handling, we cannot return to irq handling which may
* raise exception again. The ignored interrupts will be re-triggered
* if not cleared, or re-triggered by interrupt sources, or just missed
mov r3,(1 << (CONFIG_NUM_IRQ_PRIO_LEVELS - 1)) /* use lowest */
sr r3, [_ARC_V2_AUX_IRQ_ACT]

mov r2, ilink

/* Assumption: r2 has current thread */
b _rirq_common_interrupt_swap

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