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Message-Id: <20210315180229.1224655-2-keescook@chromium.org>
Date: Mon, 15 Mar 2021 11:02:24 -0700
From: Kees Cook <keescook@...omium.org>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Kees Cook <keescook@...omium.org>,
Peter Zijlstra <peterz@...radead.org>,
Elena Reshetova <elena.reshetova@...el.com>,
x86@...nel.org,
Andy Lutomirski <luto@...nel.org>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Potapenko <glider@...gle.com>,
Alexander Popov <alex.popov@...ux.com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Jann Horn <jannh@...gle.com>,
Vlastimil Babka <vbabka@...e.cz>,
David Hildenbrand <david@...hat.com>,
Mike Rapoport <rppt@...ux.ibm.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Jonathan Corbet <corbet@....net>,
Randy Dunlap <rdunlap@...radead.org>,
kernel-hardening@...ts.openwall.com,
linux-hardening@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v6 1/6] jump_label: Provide CONFIG-driven build state defaults
As shown in jump_label.h[1], 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.
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/jump_label.h?h=v5.11#n398
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lore.kernel.org/lkml/20200324220641.GT2452@worktop.programming.kicks-ass.net/
Signed-off-by: Kees Cook <keescook@...omium.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 d92691262f51..05f5554d860f 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
*/
--
2.25.1
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