linux-kernel - [PATCH AUTOSEL 5.15 07/19] s390: disable -Warray-bounds

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Date:   Tue, 10 May 2022 11:44:17 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Sven Schnelle <svens@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Sasha Levin <sashal@...nel.org>, gor@...ux.ibm.com,
        agordeev@...ux.ibm.com, linux-s390@...r.kernel.org
Subject: [PATCH AUTOSEL 5.15 07/19] s390: disable -Warray-bounds

From: Sven Schnelle <svens@...ux.ibm.com>

[ Upstream commit 8b202ee218395319aec1ef44f72043e1fbaccdd6 ]

gcc-12 shows a lot of array bound warnings on s390. This is caused
by the S390_lowcore macro which uses a hardcoded address of 0.

Wrapping that with absolute_pointer() works, but gcc no longer knows
that a 12 bit displacement is sufficient to access lowcore. So it
emits instructions like 'lghi %r1,0; l %rx,xxx(%r1)' instead of a
single load/store instruction. As s390 stores variables often
read/written in lowcore, this is considered problematic. Therefore
disable -Warray-bounds on s390 for gcc-12 for the time being, until
there is a better solution.

Signed-off-by: Sven Schnelle <svens@...ux.ibm.com>
Link: https://lore.kernel.org/r/yt9dzgkelelc.fsf@linux.ibm.com
Link: https://lore.kernel.org/r/20220422134308.1613610-1-svens@linux.ibm.com
Link: https://lore.kernel.org/r/20220425121742.3222133-1-svens@linux.ibm.com
Signed-off-by: Heiko Carstens <hca@...ux.ibm.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/s390/Makefile | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/s390/Makefile b/arch/s390/Makefile
index d4fd1426a822..c7b7a60f6405 100644
--- a/arch/s390/Makefile
+++ b/arch/s390/Makefile
@@ -32,6 +32,16 @@ KBUILD_CFLAGS_DECOMPRESSOR += -fno-stack-protector
 KBUILD_CFLAGS_DECOMPRESSOR += $(call cc-disable-warning, address-of-packed-member)
 KBUILD_CFLAGS_DECOMPRESSOR += $(if $(CONFIG_DEBUG_INFO),-g)
 KBUILD_CFLAGS_DECOMPRESSOR += $(if $(CONFIG_DEBUG_INFO_DWARF4), $(call cc-option, -gdwarf-4,))
+
+ifdef CONFIG_CC_IS_GCC
+	ifeq ($(call cc-ifversion, -ge, 1200, y), y)
+		ifeq ($(call cc-ifversion, -lt, 1300, y), y)
+			KBUILD_CFLAGS += $(call cc-disable-warning, array-bounds)
+			KBUILD_CFLAGS_DECOMPRESSOR += $(call cc-disable-warning, array-bounds)
+		endif
+	endif
+endif
+
 UTS_MACHINE	:= s390x
 STACK_SIZE	:= $(if $(CONFIG_KASAN),65536,16384)
 CHECKFLAGS	+= -D__s390__ -D__s390x__
-- 
2.35.1