Commit acd26bcf authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

genirq: Provide interrupt injection mechanism 



Error injection mechanisms need a half ways safe way to inject interrupts as
invoking generic_handle_irq() or the actual device interrupt handler
directly from e.g. a debugfs write is not guaranteed to be safe.

On x86 generic_handle_irq() is unsafe due to the hardware trainwreck which
is the base of x86 interrupt delivery and affinity management.

Move the irq debugfs injection code into a separate function which can be
used by error injection code as well.

The implementation prevents at least that state is corrupted, but it cannot
close a very tiny race window on x86 which might result in a stale and not
serviced device interrupt under very unlikely circumstances.

This is explicitly for debugging and testing and not for production use or
abuse in random driver code.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: default avatarKuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: default avatarKuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Acked-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lkml.kernel.org/r/20200306130623.990928309@linutronix.de
parent da90921a

include/linux/interrupt.h

+2 −0
Original line number Original line Diff line number Diff line
@@ -248,6 +248,8 @@ extern void enable_percpu_nmi(unsigned int irq, unsigned int type); 
extern int prepare_percpu_nmi(unsigned int irq);

extern int prepare_percpu_nmi(unsigned int irq);

extern void teardown_percpu_nmi(unsigned int irq);

extern void teardown_percpu_nmi(unsigned int irq);





extern int irq_inject_interrupt(unsigned int irq);



/* The following three functions are for the core kernel use only. */

/* The following three functions are for the core kernel use only. */

extern void suspend_device_irqs(void);

extern void suspend_device_irqs(void);

extern void resume_device_irqs(void);

extern void resume_device_irqs(void);

kernel/irq/Kconfig

+5 −0
Original line number Original line Diff line number Diff line
@@ -43,6 +43,10 @@ config GENERIC_IRQ_MIGRATION 
config AUTO_IRQ_AFFINITY

config AUTO_IRQ_AFFINITY

       bool

       bool





# Interrupt injection mechanism

config GENERIC_IRQ_INJECTION

	bool



# Tasklet based software resend for pending interrupts on enable_irq()

# Tasklet based software resend for pending interrupts on enable_irq()

config HARDIRQS_SW_RESEND

config HARDIRQS_SW_RESEND

       bool

       bool
@@ -127,6 +131,7 @@ config SPARSE_IRQ 
config GENERIC_IRQ_DEBUGFS

config GENERIC_IRQ_DEBUGFS

	bool "Expose irq internals in debugfs"

	bool "Expose irq internals in debugfs"

	depends on DEBUG_FS

	depends on DEBUG_FS

	select GENERIC_IRQ_INJECTION

	default n

	default n

	---help---

	---help---

kernel/irq/chip.c

+1 −1
Original line number Original line Diff line number Diff line
@@ -278,7 +278,7 @@ int irq_startup(struct irq_desc *desc, bool resend, bool force) 
		}

		}

	}

	}

	if (resend)

	if (resend)

		check_irq_resend(desc);

		check_irq_resend(desc, false);





	return ret;

	return ret;

}

}

kernel/irq/debugfs.c

+1 −33
Original line number Original line Diff line number Diff line
@@ -190,39 +190,7 @@ static ssize_t irq_debug_write(struct file *file, const char __user *user_buf, 
		return -EFAULT;

		return -EFAULT;





	if (!strncmp(buf, "trigger", size)) {

	if (!strncmp(buf, "trigger", size)) {

		unsigned long flags;

		int err = irq_inject_interrupt(irq_desc_get_irq(desc));

		int err;



		/* Try the HW interface first */

		err = irq_set_irqchip_state(irq_desc_get_irq(desc),

					    IRQCHIP_STATE_PENDING, true);

		if (!err)

			return count;



		/*

		 * Otherwise, try to inject via the resend interface,

		 * which may or may not succeed.

		 */

		chip_bus_lock(desc);

		raw_spin_lock_irqsave(&desc->lock, flags);



		/*

		 * Don't allow injection when the interrupt is:

		 *  - Level or NMI type

		 *  - not activated

		 *  - replaying already

		 */

		if (irq_settings_is_level(desc) ||

		    !irqd_is_activated(&desc->irq_data) ||

		    (desc->istate & (IRQS_NMI | IRQS_REPLAY))) {

			err = -EINVAL;

		} else {

			desc->istate |= IRQS_PENDING;

			err = check_irq_resend(desc);

		}



		raw_spin_unlock_irqrestore(&desc->lock, flags);

		chip_bus_sync_unlock(desc);





		return err ? err : count;

		return err ? err : count;

	}

	}

kernel/irq/internals.h

+1 −1
Original line number Original line Diff line number Diff line
@@ -108,7 +108,7 @@ irqreturn_t handle_irq_event_percpu(struct irq_desc *desc); 
irqreturn_t handle_irq_event(struct irq_desc *desc);

irqreturn_t handle_irq_event(struct irq_desc *desc);





/* Resending of interrupts :*/

/* Resending of interrupts :*/

int check_irq_resend(struct irq_desc *desc);

int check_irq_resend(struct irq_desc *desc, bool inject);

bool irq_wait_for_poll(struct irq_desc *desc);

bool irq_wait_for_poll(struct irq_desc *desc);

void __irq_wake_thread(struct irq_desc *desc, struct irqaction *action);

void __irq_wake_thread(struct irq_desc *desc, struct irqaction *action);

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