[PATCH v3 6/7] powerpc/64/interrupt: avoid BUG/WARN recursion in interrupt entry

[Nicholas Piggin]

BUG/WARN are handled with a program interrupt which can turn into an
infinite recursion when there are bugs in interrupt handler entry
(which can be irritated by bugs in other parts of the code).

There is one feeble attempt to avoid this recursion, but it misses
several cases. Make a tidier macro for this and switch most bugs in
the interrupt entry wrapper over to use it.

Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
---
 arch/powerpc/include/asm/interrupt.h | 33 +++++++++++++++++-----------
 1 file changed, 20 insertions(+), 13 deletions(-)

diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
index b61555e30c7c..7f3180047115 100644
--- a/arch/powerpc/include/asm/interrupt.h
+++ b/arch/powerpc/include/asm/interrupt.h
@@ -74,6 +74,19 @@
 #include <asm/kprobes.h>
 #include <asm/runlatch.h>
 
+#ifdef CONFIG_PPC64
+/*
+ * WARN/BUG is handled with a program interrupt so minimise checks here to
+ * avoid recursion and maximise the chance of getting the first oops handled.
+ */
+#define INT_SOFT_MASK_BUG_ON(regs, cond)				\
+do {									\
+	if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG) &&		\
+	    (user_mode(regs) || (TRAP(regs) != INTERRUPT_PROGRAM)))	\
+		BUG_ON(cond);						\
+} while (0)
+#endif
+
 #ifdef CONFIG_PPC_BOOK3S_64
 extern char __end_soft_masked[];
 bool search_kernel_soft_mask_table(unsigned long addr);
@@ -170,8 +183,7 @@ static inline void interrupt_enter_prepare(struct pt_regs *regs)
 	 * context.
 	 */
 	if (!(local_paca->irq_happened & PACA_IRQ_HARD_DIS)) {
-		if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG))
-			BUG_ON(!(regs->msr & MSR_EE));
+		INT_SOFT_MASK_BUG_ON(regs, !(regs->msr & MSR_EE));
 		__hard_irq_enable();
 	} else {
 		__hard_RI_enable();
@@ -194,20 +206,15 @@ static inline void interrupt_enter_prepare(struct pt_regs *regs)
 		 * CT_WARN_ON comes here via program_check_exception,
 		 * so avoid recursion.
 		 */
-		if (TRAP(regs) != INTERRUPT_PROGRAM) {
+		if (TRAP(regs) != INTERRUPT_PROGRAM)
 			CT_WARN_ON(ct_state() != CONTEXT_KERNEL &&
 				   ct_state() != CONTEXT_IDLE);
-			if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG))
-				BUG_ON(is_implicit_soft_masked(regs));
-		}
-
-		/* Move this under a debugging check */
-		if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG) &&
-				arch_irq_disabled_regs(regs))
-			BUG_ON(search_kernel_restart_table(regs->nip));
+		INT_SOFT_MASK_BUG_ON(regs, is_implicit_soft_masked(regs));
+		INT_SOFT_MASK_BUG_ON(regs, arch_irq_disabled_regs(regs) &&
+					   search_kernel_restart_table(regs->nip));
 	}
-	if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG))
-		BUG_ON(!arch_irq_disabled_regs(regs) && !(regs->msr & MSR_EE));
+	INT_SOFT_MASK_BUG_ON(regs, !arch_irq_disabled_regs(regs) &&
+				   !(regs->msr & MSR_EE));
 #endif
 
 	booke_restore_dbcr0();
-- 
2.37.2