linux-kernel - [PATCH AUTOSEL 4.19 02/16] s390/facility: Disable compile time optimization for decompressor code

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Message-ID: <20241004183150.3676355-2-sashal@kernel.org>
Date: Fri,  4 Oct 2024 14:31:29 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Heiko Carstens <hca@...ux.ibm.com>,
	Sven Schnelle <svens@...ux.ibm.com>,
	Sasha Levin <sashal@...nel.org>,
	gor@...ux.ibm.com,
	agordeev@...ux.ibm.com,
	frankja@...ux.ibm.com,
	nsg@...ux.ibm.com,
	linux-s390@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 02/16] s390/facility: Disable compile time optimization for decompressor code

From: Heiko Carstens <hca@...ux.ibm.com>

[ Upstream commit 0147addc4fb72a39448b8873d8acdf3a0f29aa65 ]

Disable compile time optimizations of test_facility() for the
decompressor. The decompressor should not contain any optimized code
depending on the architecture level set the kernel image is compiled
for to avoid unexpected operation exceptions.

Add a __DECOMPRESSOR check to test_facility() to enforce that
facilities are always checked during runtime for the decompressor.

Reviewed-by: Sven Schnelle <svens@...ux.ibm.com>
Signed-off-by: Heiko Carstens <hca@...ux.ibm.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/s390/include/asm/facility.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/s390/include/asm/facility.h b/arch/s390/include/asm/facility.h
index 7ffbc5d7ccf38..79730031e17f3 100644
--- a/arch/s390/include/asm/facility.h
+++ b/arch/s390/include/asm/facility.h
@@ -53,8 +53,10 @@ static inline int test_facility(unsigned long nr)
 	unsigned long facilities_als[] = { FACILITIES_ALS };
 
 	if (__builtin_constant_p(nr) && nr < sizeof(facilities_als) * 8) {
-		if (__test_facility(nr, &facilities_als))
-			return 1;
+		if (__test_facility(nr, &facilities_als)) {
+			if (!__is_defined(__DECOMPRESSOR))
+				return 1;
+		}
 	}
 	return __test_facility(nr, &S390_lowcore.stfle_fac_list);
 }
-- 
2.43.0