linux-kernel - [PATCH] powerpc/uaccess: Don't set KUEP by default on book3s/32

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Message-Id: <1492bb150c1aaa53d99a604b49992e60ea20cd5f.1586962582.git.christophe.leroy@c-s.fr>
Date:   Wed, 15 Apr 2020 14:57:11 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH] powerpc/uaccess: Don't set KUEP by default on book3s/32

On book3s/32, KUEP is an heavy process as it requires to
set/unset the NX bit in each of the 12 user segments
everytime the kernel is entered/exited from/to user space.

Don't select KUEP by default on book3s/32.

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
 arch/powerpc/platforms/Kconfig.cputype | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
index 0c7151c98b56..11412078e732 100644
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -377,7 +377,7 @@ config PPC_HAVE_KUEP
 config PPC_KUEP
 	bool "Kernel Userspace Execution Prevention"
 	depends on PPC_HAVE_KUEP
-	default y
+	default y if !PPC_BOOK3S_32
 	help
 	  Enable support for Kernel Userspace Execution Prevention (KUEP)
 
-- 
2.25.0