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From: Nathan Chancellor <natechancellor@gmail.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Sasha Levin <sashal@kernel.org>
Cc: stable@vger.kernel.org, x86@kernel.org,
	clang-built-linux@googlegroups.com,
	Nathan Chancellor <natechancellor@gmail.com>
Subject: [PATCH 4.14] x86/retpolines: Fix up backport of a9d57ef15cbe
Date: Sun, 29 Sep 2019 11:32:06 -0700	[thread overview]
Message-ID: <20190929183206.922721-1-natechancellor@gmail.com> (raw)

Commit a9d57ef15cbe ("x86/retpolines: Disable switch jump tables when
retpolines are enabled") added -fno-jump-tables to workaround a GCC issue
while deliberately avoiding adding this flag when CONFIG_CC_IS_CLANG is
set, which is defined by the kconfig system when CC=clang is provided.

However, this symbol was added in 4.18 in commit 469cb7376c06 ("kconfig:
add CC_IS_CLANG and CLANG_VERSION") so it is always undefined in 4.14,
meaning -fno-jump-tables gets added when using Clang.

Fix this up by using the equivalent $(cc-name) comparison, which matches
what upstream did until commit 076f421da5d4 ("kbuild: replace cc-name
test with CONFIG_CC_IS_CLANG").

Fixes: e28951100515 ("x86/retpolines: Disable switch jump tables when retpolines are enabled")
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---
 arch/x86/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index cd596ca60901..3dc54d2f79c4 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -249,7 +249,7 @@ ifdef CONFIG_RETPOLINE
   # retpoline builds, however, gcc does not for x86. This has
   # only been fixed starting from gcc stable version 8.4.0 and
   # onwards, but not for older ones. See gcc bug #86952.
-  ifndef CONFIG_CC_IS_CLANG
+  ifneq ($(cc-name), clang)
     KBUILD_CFLAGS += $(call cc-option,-fno-jump-tables)
   endif
 endif
-- 
2.23.0


             reply	other threads:[~2019-09-29 18:32 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-29 18:32 Nathan Chancellor [this message]
2019-10-03  7:55 ` [PATCH 4.14] x86/retpolines: Fix up backport of a9d57ef15cbe Greg Kroah-Hartman

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