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Date:   Wed, 03 Mar 2021 08:15:59 -0000
From:   "tip-bot2 for Jason Gerecke" <tip-bot2@linutronix.de>
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To:     linux-tip-commits@vger.kernel.org
Subject: [tip: locking/core] x86/jump_label: Mark arguments as const to
 satisfy asm constraints
Cc:     Jason Gerecke <jason.gerecke@wacom.com>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        "Steven Rostedt (VMware)" <rostedt@goodmis.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org
In-Reply-To: <20210211214848.536626-1-jason.gerecke@wacom.com>
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The following commit has been merged into the locking/core branch of tip:

Commit-ID:     566a9522381495d27b596ee3bdc9578ba02a895d
Gitweb:        https://git.kernel.org/tip/566a9522381495d27b596ee3bdc9578ba02=
a895d
Author:        Jason Gerecke <killertofu@gmail.com>
AuthorDate:    Thu, 11 Feb 2021 13:48:48 -08:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Tue, 02 Mar 2021 15:06:34 +01:00

x86/jump_label: Mark arguments as const to satisfy asm constraints

When compiling an external kernel module with `-O0` or `-O1`, the following
compile error may be reported:

    ./arch/x86/include/asm/jump_label.h:25:2: error: impossible constraint in=
 =E2=80=98asm=E2=80=99
       25 |  asm_volatile_goto("1:"
          |  ^~~~~~~~~~~~~~~~~

It appears that these lower optimization levels prevent GCC from detecting
that the key/branch arguments can be treated as constants and used as
immediate operands. To work around this, explicitly add the `const` label.

Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20210211214848.536626-1-jason.gerecke@wacom.c=
om
---
 arch/x86/include/asm/jump_label.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_la=
bel.h
index 06c3cc2..7f20066 100644
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -20,7 +20,7 @@
 #include <linux/stringify.h>
 #include <linux/types.h>
=20
-static __always_inline bool arch_static_branch(struct static_key *key, bool =
branch)
+static __always_inline bool arch_static_branch(struct static_key * const key=
, const bool branch)
 {
 	asm_volatile_goto("1:"
 		".byte " __stringify(STATIC_KEY_INIT_NOP) "\n\t"
@@ -36,7 +36,7 @@ l_yes:
 	return true;
 }
=20
-static __always_inline bool arch_static_branch_jump(struct static_key *key, =
bool branch)
+static __always_inline bool arch_static_branch_jump(struct static_key * cons=
t key, const bool branch)
 {
 	asm_volatile_goto("1:"
 		".byte 0xe9\n\t .long %l[l_yes] - 2f\n\t"