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SubjectRe: [PATCH v3 6/8] arm64: irqflags: Introduce explicit debugging for IRQ priorities
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On 07/06/2019 17:31, Marc Zyngier wrote:
> On 06/06/2019 10:31, Julien Thierry wrote:
>> Using IRQ priority masking to enable/disable interrupts is a bit
>> sensitive as it requires to deal with both ICC_PMR_EL1 and PSR.I.
>>
>> Introduce some validity checks to both highlight the states in which
>> functions dealing with IRQ enabling/disabling can (not) be called, and
>> bark a warning when called in an unexpected state.
>>
>> Since these checks are done on hotpaths, introduce a build option to
>> choose whether to do the checking.
>>
>> Signed-off-by: Julien Thierry <julien.thierry@arm.com>
>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>> Cc: Will Deacon <will.deacon@arm.com>
>> ---
>> arch/arm64/Kconfig | 11 +++++++++++
>> arch/arm64/include/asm/cpufeature.h | 6 ++++++
>> arch/arm64/include/asm/daifflags.h | 7 +++++++
>> arch/arm64/include/asm/irqflags.h | 14 +++++++++++++-
>> 4 files changed, 37 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 697ea05..8acc40e 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -1436,6 +1436,17 @@ config ARM64_PSEUDO_NMI
>>
>> If unsure, say N
>>
>> +if ARM64_PSEUDO_NMI
>> +config ARM64_DEBUG_PRIORITY_MASKING
>> + bool "Debug interrupt priority masking"
>> + help
>> + This adds runtime checks to functions enabling/disabling
>> + interrupts when using priority masking. The additional checks verify
>> + the validity of ICC_PMR_EL1 when calling concerned functions.
>> +
>> + If unsure, say N
>> +endif
>> +
>> config RELOCATABLE
>> bool
>> help
>> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
>> index bc895c8..693a086 100644
>> --- a/arch/arm64/include/asm/cpufeature.h
>> +++ b/arch/arm64/include/asm/cpufeature.h
>> @@ -617,6 +617,12 @@ static inline bool system_uses_irq_prio_masking(void)
>> cpus_have_const_cap(ARM64_HAS_IRQ_PRIO_MASKING);
>> }
>>
>> +static inline bool system_has_prio_mask_debugging(void)
>> +{
>> + return IS_ENABLED(CONFIG_ARM64_DEBUG_PRIORITY_MASKING) &&
>> + system_uses_irq_prio_masking();
>> +}
>> +
>> #define ARM64_SSBD_UNKNOWN -1
>> #define ARM64_SSBD_FORCE_DISABLE 0
>> #define ARM64_SSBD_KERNEL 1
>> diff --git a/arch/arm64/include/asm/daifflags.h b/arch/arm64/include/asm/daifflags.h
>> index f93204f..eca5bee 100644
>> --- a/arch/arm64/include/asm/daifflags.h
>> +++ b/arch/arm64/include/asm/daifflags.h
>> @@ -28,6 +28,10 @@
>> /* mask/save/unmask/restore all exceptions, including interrupts. */
>> static inline void local_daif_mask(void)
>> {
>> + WARN_ON(system_has_prio_mask_debugging() &&
>> + (read_sysreg_s(SYS_ICC_PMR_EL1) == (GIC_PRIO_IRQOFF |
>> + GIC_PRIO_PSR_I_SET)));
>> +
>> asm volatile(
>> "msr daifset, #0xf // local_daif_mask\n"
>> :
>> @@ -62,6 +66,9 @@ static inline void local_daif_restore(unsigned long flags)
>> {
>> bool irq_disabled = flags & PSR_I_BIT;
>>
>> + WARN_ON(system_has_prio_mask_debugging() &&
>> + !(read_sysreg(daif) & PSR_I_BIT));
>> +
>> if (!irq_disabled) {
>> trace_hardirqs_on();
>>
>> diff --git a/arch/arm64/include/asm/irqflags.h b/arch/arm64/include/asm/irqflags.h
>> index b6f757f..cac2d2a 100644
>> --- a/arch/arm64/include/asm/irqflags.h
>> +++ b/arch/arm64/include/asm/irqflags.h
>> @@ -40,6 +40,12 @@
>> */
>> static inline void arch_local_irq_enable(void)
>> {
>> + if (system_has_prio_mask_debugging()) {
>> + u32 pmr = read_sysreg_s(SYS_ICC_PMR_EL1);
>> +
>> + WARN_ON_ONCE(pmr != GIC_PRIO_IRQON && pmr != GIC_PRIO_IRQOFF);
>> + }
>> +
>> asm volatile(ALTERNATIVE(
>> "msr daifclr, #2 // arch_local_irq_enable\n"
>> "nop",
>> @@ -53,6 +59,12 @@ static inline void arch_local_irq_enable(void)
>>
>> static inline void arch_local_irq_disable(void)
>> {
>> + if (system_has_prio_mask_debugging()) {
>> + u32 pmr = read_sysreg_s(SYS_ICC_PMR_EL1);
>> +
>> + WARN_ON_ONCE(pmr != GIC_PRIO_IRQON && pmr != GIC_PRIO_IRQOFF);
>> + }
>> +
>> asm volatile(ALTERNATIVE(
>> "msr daifset, #2 // arch_local_irq_disable",
>> __msr_s(SYS_ICC_PMR_EL1, "%0"),
>> @@ -86,7 +98,7 @@ static inline int arch_irqs_disabled_flags(unsigned long flags)
>>
>> asm volatile(ALTERNATIVE(
>> "and %w0, %w1, #" __stringify(PSR_I_BIT),
>> - "eor %w0, %w1, #" __stringify(GIC_PRIO_IRQOFF),
>> + "eor %w0, %w1, #" __stringify(GIC_PRIO_IRQON),
>
> Err... Which version is the correct one? This one, or the previous one?
>

Argh, bad fixup of the patches. This one is the correct one (any state
!= GIC_PRIO_IRQON means interrupts are disabled), but the correct value
should already be in use in the previous patch.

Will fix that in the next posting.

Thanks,

--
Julien Thierry

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