From acd26bcf362708594ea081ef55140e37d0854ed2 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Fri, 6 Mar 2020 14:03:47 +0100 Subject: 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 Tested-by: Kuppuswamy Sathyanarayanan Reviewed-by: Kuppuswamy Sathyanarayanan Acked-by: Marc Zyngier Link: https://lkml.kernel.org/r/20200306130623.990928309@linutronix.de --- include/linux/interrupt.h | 2 ++ kernel/irq/Kconfig | 5 +++++ kernel/irq/chip.c | 2 +- kernel/irq/debugfs.c | 34 +----------------------------- kernel/irq/internals.h | 2 +- kernel/irq/resend.c | 53 +++++++++++++++++++++++++++++++++++++++++++++-- 6 files changed, 61 insertions(+), 37 deletions(-) diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h index c5fe60ec6b84..80f637c3a6f3 100644 --- a/include/linux/interrupt.h +++ b/include/linux/interrupt.h @@ -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); diff --git a/kernel/irq/Kconfig b/kernel/irq/Kconfig index f92d9a687372..20d501af4f2e 100644 --- a/kernel/irq/Kconfig +++ b/kernel/irq/Kconfig @@ -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--- diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c index b3fa2d87d2f3..41e7e37a0928 100644 --- a/kernel/irq/chip.c +++ b/kernel/irq/chip.c @@ -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; } 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; } diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h index 8980859bdf1e..7db284b10ac9 100644 --- a/kernel/irq/internals.h +++ b/kernel/irq/internals.h @@ -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); diff --git a/kernel/irq/resend.c b/kernel/irq/resend.c index bef72dcfb79b..27634f4022d0 100644 --- a/kernel/irq/resend.c +++ b/kernel/irq/resend.c @@ -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 -- cgit v1.2.3-59-g8ed1b