From: Julien Thierry julien.thierry@arm.com
commit 17ce302f3117e9518395847a3120c8a108b587b8 upstream.
In the presence of any form of instrumentation, nmi_enter() should be done before calling any traceable code and any instrumentation code.
Currently, nmi_enter() is done in handle_domain_nmi(), which is much too late as instrumentation code might get called before. Move the nmi_enter/exit() calls to the arch IRQ vector handler.
On arm64, it is not possible to know if the IRQ vector handler was called because of an NMI before acknowledging the interrupt. However, It is possible to know whether normal interrupts could be taken in the interrupted context (i.e. if taking an NMI in that context could introduce a potential race condition).
When interrupting a context with IRQs disabled, call nmi_enter() as soon as possible. In contexts with IRQs enabled, defer this to the interrupt controller, which is in a better position to know if an interrupt taken is an NMI.
Fixes: bc3c03ccb464 ("arm64: Enable the support of pseudo-NMIs") Cc: stable@vger.kernel.org # 5.1.x- Cc: Will Deacon will.deacon@arm.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Jason Cooper jason@lakedaemon.net Cc: Mark Rutland mark.rutland@arm.com Reviewed-by: Marc Zyngier marc.zyngier@arm.com Signed-off-by: Julien Thierry julien.thierry@arm.com Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/arm64/kernel/entry.S | 44 ++++++++++++++++++++++++++++++++----------- arch/arm64/kernel/irq.c | 17 ++++++++++++++++ drivers/irqchip/irq-gic-v3.c | 7 ++++++ kernel/irq/irqdesc.c | 8 +++++-- 4 files changed, 63 insertions(+), 13 deletions(-)
--- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -420,6 +420,20 @@ tsk .req x28 // current thread_info irq_stack_exit .endm
+#ifdef CONFIG_ARM64_PSEUDO_NMI + /* + * Set res to 0 if irqs were unmasked in interrupted context. + * Otherwise set res to non-0 value. + */ + .macro test_irqs_unmasked res:req, pmr:req +alternative_if ARM64_HAS_IRQ_PRIO_MASKING + sub \res, \pmr, #GIC_PRIO_IRQON +alternative_else + mov \res, xzr +alternative_endif + .endm +#endif + .text
/* @@ -616,19 +630,19 @@ ENDPROC(el1_sync) el1_irq: kernel_entry 1 enable_da_f -#ifdef CONFIG_TRACE_IRQFLAGS + #ifdef CONFIG_ARM64_PSEUDO_NMI alternative_if ARM64_HAS_IRQ_PRIO_MASKING ldr x20, [sp, #S_PMR_SAVE] -alternative_else - mov x20, #GIC_PRIO_IRQON -alternative_endif - cmp x20, #GIC_PRIO_IRQOFF - /* Irqs were disabled, don't trace */ - b.ls 1f +alternative_else_nop_endif + test_irqs_unmasked res=x0, pmr=x20 + cbz x0, 1f + bl asm_nmi_enter +1: #endif + +#ifdef CONFIG_TRACE_IRQFLAGS bl trace_hardirqs_off -1: #endif
irq_handler @@ -647,14 +661,22 @@ alternative_else_nop_endif bl preempt_schedule_irq // irq en/disable is done inside 1: #endif -#ifdef CONFIG_TRACE_IRQFLAGS + #ifdef CONFIG_ARM64_PSEUDO_NMI /* * if IRQs were disabled when we received the interrupt, we have an NMI * and we are not re-enabling interrupt upon eret. Skip tracing. */ - cmp x20, #GIC_PRIO_IRQOFF - b.ls 1f + test_irqs_unmasked res=x0, pmr=x20 + cbz x0, 1f + bl asm_nmi_exit +1: +#endif + +#ifdef CONFIG_TRACE_IRQFLAGS +#ifdef CONFIG_ARM64_PSEUDO_NMI + test_irqs_unmasked res=x0, pmr=x20 + cbnz x0, 1f #endif bl trace_hardirqs_on 1: --- a/arch/arm64/kernel/irq.c +++ b/arch/arm64/kernel/irq.c @@ -27,8 +27,10 @@ #include <linux/smp.h> #include <linux/init.h> #include <linux/irqchip.h> +#include <linux/kprobes.h> #include <linux/seq_file.h> #include <linux/vmalloc.h> +#include <asm/daifflags.h> #include <asm/vmap_stack.h>
unsigned long irq_err_count; @@ -76,3 +78,18 @@ void __init init_IRQ(void) if (!handle_arch_irq) panic("No interrupt controller found."); } + +/* + * Stubs to make nmi_enter/exit() code callable from ASM + */ +asmlinkage void notrace asm_nmi_enter(void) +{ + nmi_enter(); +} +NOKPROBE_SYMBOL(asm_nmi_enter); + +asmlinkage void notrace asm_nmi_exit(void) +{ + nmi_exit(); +} +NOKPROBE_SYMBOL(asm_nmi_exit); --- a/drivers/irqchip/irq-gic-v3.c +++ b/drivers/irqchip/irq-gic-v3.c @@ -472,8 +472,12 @@ static void gic_deactivate_unhandled(u32
static inline void gic_handle_nmi(u32 irqnr, struct pt_regs *regs) { + bool irqs_enabled = interrupts_enabled(regs); int err;
+ if (irqs_enabled) + nmi_enter(); + if (static_branch_likely(&supports_deactivate_key)) gic_write_eoir(irqnr); /* @@ -485,6 +489,9 @@ static inline void gic_handle_nmi(u32 ir err = handle_domain_nmi(gic_data.domain, irqnr, regs); if (err) gic_deactivate_unhandled(irqnr); + + if (irqs_enabled) + nmi_exit(); }
static asmlinkage void __exception_irq_entry gic_handle_irq(struct pt_regs *regs) --- a/kernel/irq/irqdesc.c +++ b/kernel/irq/irqdesc.c @@ -679,6 +679,8 @@ int __handle_domain_irq(struct irq_domai * @hwirq: The HW irq number to convert to a logical one * @regs: Register file coming from the low-level handling code * + * This function must be called from an NMI context. + * * Returns: 0 on success, or -EINVAL if conversion has failed */ int handle_domain_nmi(struct irq_domain *domain, unsigned int hwirq, @@ -688,7 +690,10 @@ int handle_domain_nmi(struct irq_domain unsigned int irq; int ret = 0;
- nmi_enter(); + /* + * NMI context needs to be setup earlier in order to deal with tracing. + */ + WARN_ON(!in_nmi());
irq = irq_find_mapping(domain, hwirq);
@@ -701,7 +706,6 @@ int handle_domain_nmi(struct irq_domain else ret = -EINVAL;
- nmi_exit(); set_irq_regs(old_regs); return ret; }