linux-kernel - [tip: x86/percpu] x86/percpu: Fix x86_this_cpu_variable_test

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Date: Sat, 06 Apr 2024 11:07:57 -0000
From: "tip-bot2 for Uros Bizjak" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Uros Bizjak <ubizjak@...il.com>, Ingo Molnar <mingo@...nel.org>,
 Linus Torvalds <torvalds@...ux-foundation.org>,
 "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: x86/percpu] x86/percpu: Fix x86_this_cpu_variable_test_bit()
 asm template

The following commit has been merged into the x86/percpu branch of tip:

Commit-ID:     4c3677c077582f8665806def3f6dd35587793c69
Gitweb:        https://git.kernel.org/tip/4c3677c077582f8665806def3f6dd35587793c69
Author:        Uros Bizjak <ubizjak@...il.com>
AuthorDate:    Thu, 04 Apr 2024 11:42:01 +02:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Sat, 06 Apr 2024 12:42:17 +02:00

x86/percpu: Fix x86_this_cpu_variable_test_bit() asm template

Fix x86_this_cpu_variable_test_bit(), which is implemented with an
incorrect asm template, where argument 2 (count argument) is considered
a percpu variable. However, x86_this_cpu_test_bit() is currently
used exclusively with constant bit number argument, so the called
x86_this_cpu_variable_test_bit() function is never instantiated.

The fix introduces named assembler operands to prevent this kind
of error.

Signed-off-by: Uros Bizjak <ubizjak@...il.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: "H. Peter Anvin" <hpa@...or.com>
Link: https://lore.kernel.org/r/20240404094218.448963-1-ubizjak@gmail.com
---
 arch/x86/include/asm/percpu.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index 20696df..cbfbbe8 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -586,10 +586,11 @@ static inline bool x86_this_cpu_variable_test_bit(int nr,
 {
 	bool oldbit;

-	asm volatile("btl "__percpu_arg(2)",%1"
+	asm volatile("btl %[nr], " __percpu_arg([var])
 			CC_SET(c)
 			: CC_OUT(c) (oldbit)
-			: "m" (*__my_cpu_ptr((unsigned long __percpu *)(addr))), "Ir" (nr));
+			: [var] "m" (*__my_cpu_ptr((unsigned long __percpu *)(addr))),
+			  [nr] "Ir" (nr));

 	return oldbit;
 }