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
diff --git a/kernel/irq/debugfs.c b/kernel/irq/debugfs.c
index 0c60779..4f9f844 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;
}