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: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lkml.kernel.org/r/20200306130623.990928309@linutronix.de

1 files changed, 1 insertions, 33 deletions

diff --git a/kernel/irq/debugfs.c b/kernel/irq/debugfs.c
index 0c607798f519..4f9f844074db 100644
--- a/kernel/irq/debugfs.c
+++ b/kernel/irq/debugfs.c
@@ -190,39 +190,7 @@ static ssize_t irq_debug_write(struct file *file, const char __user *user_buf,
 		return -EFAULT;
 
 	if (!strncmp(buf, "trigger", size)) {
-		unsigned long flags;
-		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);
+		int err = irq_inject_interrupt(irq_desc_get_irq(desc));
 
 		return err ? err : count;
 	}