On 2021-02-22 09:59, Mark Rutland wrote:

On Fri, Feb 19, 2021 at 11:39:01AM +0000, Mark Rutland wrote:

quoted

If we accidentally unmask IRQs before we've registered an IRQ
controller, handle_arch_irq will be NULL, and the IRQ exception 
handler
will branch to a bogus address.

To make this easier to debug, this patch initialises handle_arch_irq 
to
a default handler which will panic(), making such problems easier to
debug. When we add support for FIQ handlers, we can follow the same
approach.

quoted

-void (*handle_arch_irq)(struct pt_regs *) __ro_after_init;
+void default_handle_irq(struct pt_regs *regs)
+{
+	panic("IRQ taken without a registered IRQ controller\n");
+}

The kbuild test robot pointed out that this should be static (likewise
with default_handle_fiq in patch 8), since it's only used within this
file, so I've updated that in my branch.

Mark.

quoted

+
+void (*handle_arch_irq)(struct pt_regs *) __ro_after_init = 
default_handle_irq;

 int __init set_handle_irq(void (*handle_irq)(struct pt_regs *))
 {
-	if (handle_arch_irq)
+	if (handle_arch_irq != default_handle_irq)
 		return -EBUSY;

 	handle_arch_irq = handle_irq;

@@ -87,7 +92,7 @@ void __init init_IRQ(void)
 	init_irq_stacks();
 	init_irq_scs();
 	irqchip_init();
-	if (!handle_arch_irq)
+	if (handle_arch_irq == default_handle_irq)
 		panic("No interrupt controller found.");

It also seems odd to have both default_handle_irq() that panics,
and init_IRQ that panics as well. Not a big deal, but maybe
we should just drop this altogether and get the firework on the
first interrupt.

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...

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