linux-kernel - Re: [PATCH 5/8] arm64: irq: add a default handle

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Message-ID: <20210222095913.GA70951@C02TD0UTHF1T.local>
Date:   Mon, 22 Feb 2021 09:59:13 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     catalin.marinas@....com, james.morse@....com, marcan@...can.st,
        maz@...nel.org, tglx@...utronix.de, will@...nel.org
Subject: Re: [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
>