Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Christophe Leroy <christophe.leroy@csgroup.eu>
To:     Michael Ellerman <mpe@ellerman.id.au>,
        Nicholas Piggin <npiggin@gmail.com>
Cc:     Christophe Leroy <christophe.leroy@csgroup.eu>,
        linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        Zhouyi Zhou <zhouzhouyi@gmail.com>
Subject: [PATCH] powerpc: Fix hard_irq_disable() with sanitizer
Date:   Tue, 23 Aug 2022 18:36:35 +0200
Message-Id: <a8298991b3df049a54ee8e558838e34265812014.1661272586.git.christophe.leroy@csgroup.eu>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

As reported by Zhouyi Zhou, WRITE_ONCE() is not atomic
as expected when KASAN or KCSAN are compiled in.

Fix it by re-implementing it using inline assembly.

Reported-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
Fixes: 077fc62b2b66 ("powerpc/irq: remove inline assembly in hard_irq_disable macro")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/include/asm/hw_irq.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h
index 8a7b0b78a80e..83ab6668387b 100644
--- a/arch/powerpc/include/asm/hw_irq.h
+++ b/arch/powerpc/include/asm/hw_irq.h
@@ -285,7 +285,8 @@ static inline bool pmi_irq_pending(void)
 	flags = irq_soft_mask_set_return(IRQS_ALL_DISABLED);		\
 	local_paca->irq_happened |= PACA_IRQ_HARD_DIS;			\
 	if (!arch_irqs_disabled_flags(flags)) {				\
-		WRITE_ONCE(local_paca->saved_r1, current_stack_pointer);\
+		asm volatile("std%X0 %1,%0" : "=m" (local_paca->saved_r1) \
+					    : "r" (current_stack_pointer)); \
 		trace_hardirqs_off();					\
 	}								\
 } while(0)
-- 
2.37.1