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Message-ID: <161788402204.29796.3718117807122564028.tip-bot2@tip-bot2>
Date: Thu, 08 Apr 2021 12:13:42 -0000
From: "tip-bot2 for Kees Cook" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Kees Cook <keescook@...omium.org>,
Thomas Gleixner <tglx@...utronix.de>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: x86/entry] jump_label: Provide CONFIG-driven build state defaults
The following commit has been merged into the x86/entry branch of tip:
Commit-ID: 0d66ccc1627013c95f1e7ef10b95b8451cd7834e
Gitweb: https://git.kernel.org/tip/0d66ccc1627013c95f1e7ef10b95b8451cd7834e
Author: Kees Cook <keescook@...omium.org>
AuthorDate: Thu, 01 Apr 2021 16:23:42 -07:00
Committer: Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Thu, 08 Apr 2021 14:05:19 +02:00
jump_label: Provide CONFIG-driven build state defaults
As shown in the comment in jump_label.h, choosing the initial state of
static branches changes the assembly layout. If the condition is expected
to be likely it's inline, and if unlikely it is out of line via a jump.
A few places in the kernel use (or could be using) a CONFIG to choose the
default state, which would give a small performance benefit to their
compile-time declared default. Provide the infrastructure to do this.
Signed-off-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lore.kernel.org/r/20210401232347.2791257-2-keescook@chromium.org
---
include/linux/jump_label.h | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index d926912..05f5554 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -382,6 +382,21 @@ struct static_key_false {
[0 ... (count) - 1] = STATIC_KEY_FALSE_INIT, \
}
+#define _DEFINE_STATIC_KEY_1(name) DEFINE_STATIC_KEY_TRUE(name)
+#define _DEFINE_STATIC_KEY_0(name) DEFINE_STATIC_KEY_FALSE(name)
+#define DEFINE_STATIC_KEY_MAYBE(cfg, name) \
+ __PASTE(_DEFINE_STATIC_KEY_, IS_ENABLED(cfg))(name)
+
+#define _DEFINE_STATIC_KEY_RO_1(name) DEFINE_STATIC_KEY_TRUE_RO(name)
+#define _DEFINE_STATIC_KEY_RO_0(name) DEFINE_STATIC_KEY_FALSE_RO(name)
+#define DEFINE_STATIC_KEY_MAYBE_RO(cfg, name) \
+ __PASTE(_DEFINE_STATIC_KEY_RO_, IS_ENABLED(cfg))(name)
+
+#define _DECLARE_STATIC_KEY_1(name) DECLARE_STATIC_KEY_TRUE(name)
+#define _DECLARE_STATIC_KEY_0(name) DECLARE_STATIC_KEY_FALSE(name)
+#define DECLARE_STATIC_KEY_MAYBE(cfg, name) \
+ __PASTE(_DECLARE_STATIC_KEY_, IS_ENABLED(cfg))(name)
+
extern bool ____wrong_branch_error(void);
#define static_key_enabled(x) \
@@ -482,6 +497,10 @@ extern bool ____wrong_branch_error(void);
#endif /* CONFIG_JUMP_LABEL */
+#define static_branch_maybe(config, x) \
+ (IS_ENABLED(config) ? static_branch_likely(x) \
+ : static_branch_unlikely(x))
+
/*
* Advanced usage; refcount, branch is enabled when: count != 0
*/
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