linux-kernel - [PATCH] x86/percpu: Enable named address spaces for all capable GCC versions

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Message-ID: <20240520082134.121320-1-ubizjak@gmail.com>
Date: Mon, 20 May 2024 10:21:14 +0200
From: Uros Bizjak <ubizjak@...il.com>
To: linux-kernel@...r.kernel.org,
	x86@...nel.org
Cc: Uros Bizjak <ubizjak@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Andy Lutomirski <luto@...nel.org>,
	Brian Gerst <brgerst@...il.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Josh Poimboeuf <jpoimboe@...hat.com>
Subject: [PATCH] x86/percpu: Enable named address spaces for all capable GCC versions

Enable named address spaces also for GCC 6, GCC 7 and GCC 8
releases. These compilers all produce kernel images that boot
without problems.

Use compile-time test to detect compiler support for named
address spaces. The test passes with GCC 6 as the earliest
compiler version where the support for named address spaces
was introduced.

Signed-off-by: Uros Bizjak <ubizjak@...il.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
---
 arch/x86/Kconfig | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 9d16fee6bdb8..c9e0a54f469e 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2430,7 +2430,8 @@ source "kernel/livepatch/Kconfig"
 endmenu
 
 config CC_HAS_NAMED_AS
-	def_bool CC_IS_GCC && GCC_VERSION >= 90100
+	def_bool $(success,echo 'int __seg_fs fs; int __seg_gs gs;' | $(CC) -x c - -S -o /dev/null)
+	depends on CC_IS_GCC
 
 config CC_HAS_NAMED_AS_FIXED_SANITIZERS
 	def_bool CC_IS_GCC && GCC_VERSION >= 130300
-- 
2.45.1