From: Kees Cook keescook@chromium.org
mainline inclusion from mainline-v5.13-rc1 commit 0d66ccc1627013c95f1e7ef10b95b8451cd7834e category: featrue bugzilla: https://gitee.com/openeuler/kernel/issues/I5YQ6Z CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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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@chromium.org Signed-off-by: Thomas Gleixner tglx@linutronix.de Acked-by: Peter Zijlstra (Intel) peterz@infradead.org Link: https://lore.kernel.org/r/20210401232347.2791257-2-keescook@chromium.org Signed-off-by: Yi Yang yiyang13@huawei.com Reviewed-by: Xiu Jianfeng xiujianfeng@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- 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 470a7e5a7756..6dec6543393b 100644 --- a/include/linux/jump_label.h +++ b/include/linux/jump_label.h @@ -388,6 +388,21 @@ 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) \ @@ -488,6 +503,10 @@ 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 */