[PATCH 3.16 124/245] powerpc/irq: fix stack overflow verification

Ben Hutchings
2020-04-23T23:15:49Z

From: Christophe Leroy <christophe.leroy@c-s.fr>

commit 099bc4812f09155da77eeb960a983470249c9ce1 upstream.

Before commit 0366a1c70b89 ("powerpc/irq: Run softirqs off the top of
the irq stack"), check_stack_overflow() was called by do_IRQ(), before
switching to the irq stack.
In that commit, do_IRQ() was renamed __do_irq(), and is now executing
on the irq stack, so check_stack_overflow() has just become almost
useless.

Move check_stack_overflow() call in do_IRQ() to do the check while
still on the current stack.

Fixes: 0366a1c70b89 ("powerpc/irq: Run softirqs off the top of the irq stack")
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/e033aa8116ab12b7ca9a9c75189ad0741e3b9b5f.1575872340.git.christophe.leroy@c-s.fr
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/powerpc/kernel/irq.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -471,8 +471,6 @@ void __do_irq(struct pt_regs *regs)

trace_irq_entry(regs);

- check_stack_overflow();
-
/*
* Query the platform PIC for the interrupt & ack it.
*
@@ -504,6 +502,8 @@ void do_IRQ(struct pt_regs *regs)
irqtp = hardirq_ctx[raw_smp_processor_id()];
sirqtp = softirq_ctx[raw_smp_processor_id()];

+ check_stack_overflow();
+
/* Already there ? */
if (unlikely(curtp == irqtp || curtp == sirqtp)) {
__do_irq(regs);