linux-kernel - [PATCH AUTOSEL 5.10 32/38] jump_label,noinstr: Avoid instrumentation for JUMP

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Message-Id: <20220607175835.480735-32-sashal@kernel.org>
Date:   Tue,  7 Jun 2022 13:58:27 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        kernel test robot <lkp@...el.com>,
        Sasha Levin <sashal@...nel.org>, jpoimboe@...nel.org,
        jbaron@...mai.com
Subject: [PATCH AUTOSEL 5.10 32/38] jump_label,noinstr: Avoid instrumentation for JUMP_LABEL=n builds

From: Peter Zijlstra <peterz@...radead.org>

[ Upstream commit 656d054e0a15ec327bd82801ccd58201e59f6896 ]

When building x86_64 with JUMP_LABEL=n it's possible for
instrumentation to sneak into noinstr:

vmlinux.o: warning: objtool: exit_to_user_mode+0x14: call to static_key_count.constprop.0() leaves .noinstr.text section
vmlinux.o: warning: objtool: syscall_exit_to_user_mode+0x2d: call to static_key_count.constprop.0() leaves .noinstr.text section
vmlinux.o: warning: objtool: irqentry_exit_to_user_mode+0x1b: call to static_key_count.constprop.0() leaves .noinstr.text section

Switch to arch_ prefixed atomic to avoid the explicit instrumentation.

Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 include/linux/jump_label.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index 32809624d422..e67ee4d7318f 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -249,9 +249,9 @@ extern void static_key_disable_cpuslocked(struct static_key *key);
 #include <linux/atomic.h>
 #include <linux/bug.h>
 
-static inline int static_key_count(struct static_key *key)
+static __always_inline int static_key_count(struct static_key *key)
 {
-	return atomic_read(&key->enabled);
+	return arch_atomic_read(&key->enabled);
 }
 
 static __always_inline void jump_label_init(void)
-- 
2.35.1