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

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Date:   Fri, 19 Feb 2021 11:39:01 +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,
        mark.rutland@....com, maz@...nel.org, tglx@...utronix.de,
        will@...nel.org
Subject: [PATCH 5/8] arm64: irq: add a default handle_irq panic function

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.

Signed-off-by: Mark Rutland <mark.rutland@....com>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Hector Martin <marcan@...can.st>
Cc: James Morse <james.morse@....com>
Cc: Marc Zyngier <maz@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Will Deacon <will@...nel.org>
---
 arch/arm64/kernel/irq.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/irq.c b/arch/arm64/kernel/irq.c
index ad63bd50fa7b..00bcf37aa0ea 100644
--- a/arch/arm64/kernel/irq.c
+++ b/arch/arm64/kernel/irq.c
@@ -71,11 +71,16 @@ static void init_irq_stacks(void)
 }
 #endif
 
-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");
+}
+
+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