arm64: irqflags: Introduce explicit debugging for IRQ priorities

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.

Cc: Will Deacon <will.deacon@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>

1 files changed, 7 insertions, 0 deletions

diff --git a/arch/arm64/include/asm/daifflags.h b/arch/arm64/include/asm/daifflags.h
index f93204f319da..eca5bee1d85b 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();