Commit acd26bcf authored by Thomas Gleixner's avatar Thomas Gleixner

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
......@@ -248,6 +248,8 @@ extern void enable_percpu_nmi(unsigned int irq, unsigned int type);
extern int prepare_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. */
extern void suspend_device_irqs(void);
extern void resume_device_irqs(void);
......
......@@ -43,6 +43,10 @@ config GENERIC_IRQ_MIGRATION
config AUTO_IRQ_AFFINITY
bool
# Interrupt injection mechanism
config GENERIC_IRQ_INJECTION
bool
# Tasklet based software resend for pending interrupts on enable_irq()
config HARDIRQS_SW_RESEND
bool
......@@ -127,6 +131,7 @@ config SPARSE_IRQ
config GENERIC_IRQ_DEBUGFS
bool "Expose irq internals in debugfs"
depends on DEBUG_FS
select GENERIC_IRQ_INJECTION
default n
---help---
......
......@@ -278,7 +278,7 @@ int irq_startup(struct irq_desc *desc, bool resend, bool force)
}
}
if (resend)
check_irq_resend(desc);
check_irq_resend(desc, false);
return ret;
}
......
......@@ -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;
}
......
......@@ -108,7 +108,7 @@ irqreturn_t handle_irq_event_percpu(struct irq_desc *desc);
irqreturn_t handle_irq_event(struct irq_desc *desc);
/* 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);
void __irq_wake_thread(struct irq_desc *desc, struct irqaction *action);
......
......@@ -91,7 +91,7 @@ static int irq_sw_resend(struct irq_desc *desc)
*
* Is called with interrupts disabled and desc->lock held.
*/
int check_irq_resend(struct irq_desc *desc)
int check_irq_resend(struct irq_desc *desc, bool inject)
{
int err = 0;
......@@ -108,7 +108,7 @@ int check_irq_resend(struct irq_desc *desc)
if (desc->istate & IRQS_REPLAY)
return -EBUSY;
if (!(desc->istate & IRQS_PENDING))
if (!(desc->istate & IRQS_PENDING) && !inject)
return 0;
desc->istate &= ~IRQS_PENDING;
......@@ -122,3 +122,52 @@ int check_irq_resend(struct irq_desc *desc)
desc->istate |= IRQS_REPLAY;
return err;
}
#ifdef CONFIG_GENERIC_IRQ_INJECTION
/**
* irq_inject_interrupt - Inject an interrupt for testing/error injection
* @irq: The interrupt number
*
* This function must only be used for debug and testing purposes!
*
* Especially on x86 this can cause a premature completion of an interrupt
* affinity change causing the interrupt line to become stale. Very
* unlikely, but possible.
*
* The injection can fail for various reasons:
* - Interrupt is not activated
* - Interrupt is NMI type or currently replaying
* - Interrupt is level type
* - Interrupt does not support hardware retrigger and software resend is
* either not enabled or not possible for the interrupt.
*/
int irq_inject_interrupt(unsigned int irq)
{
struct irq_desc *desc;
unsigned long flags;
int err;
/* Try the state injection hardware interface first */
if (!irq_set_irqchip_state(irq, IRQCHIP_STATE_PENDING, true))
return 0;
/* That failed, try via the resend mechanism */
desc = irq_get_desc_buslock(irq, &flags, 0);
if (!desc)
return -EINVAL;
/*
* Only try to inject when the interrupt is:
* - not NMI type
* - activated
*/
if ((desc->istate & IRQS_NMI) || !irqd_is_activated(&desc->irq_data))
err = -EINVAL;
else
err = check_irq_resend(desc, true);
irq_put_desc_busunlock(desc, flags);
return err;
}
EXPORT_SYMBOL_GPL(irq_inject_interrupt);
#endif
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