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SubjectRe: [PATCH 5/8] arm64: irq: add a default handle_irq panic function
On Fri, Feb 19, 2021 at 11:39:01AM +0000, Mark Rutland wrote:
> 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.

> -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.

> +
> +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.");
>
> if (system_uses_irq_prio_masking()) {
> --
> 2.11.0
>

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