linux-kernel - [PATCH 1/7] s390/facility: Disable compile time optimization for decompressor code

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Message-ID: <20240913130544.2398678-2-hca@linux.ibm.com>
Date: Fri, 13 Sep 2024 15:05:37 +0200
From: Heiko Carstens <hca@...ux.ibm.com>
To: "Jason A . Donenfeld" <Jason@...c4.com>
Cc: Alexander Gordeev <agordeev@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Harald Freudenberger <freude@...ux.ibm.com>,
        Stefan Liebler <stli@...ux.ibm.com>, linux-kernel@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-s390@...r.kernel.org
Subject: [PATCH 1/7] s390/facility: Disable compile time optimization for decompressor code

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>
---
 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 b7d234838a36..65ebf86506cd 100644
--- a/arch/s390/include/asm/facility.h
+++ b/arch/s390/include/asm/facility.h
@@ -59,8 +59,10 @@ 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, &stfle_fac_list);
 }
-- 
2.43.0