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From:   Kees Cook <keescook@chromium.org>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     Kees Cook <keescook@chromium.org>,
        Elena Reshetova <elena.reshetova@intel.com>, x86@kernel.org,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Potapenko <glider@google.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Jann Horn <jannh@google.com>,
        "Perla, Enrico" <enrico.perla@intel.com>,
        kernel-hardening@lists.openwall.com,
        linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH v2 2/5] init_on_alloc: Unpessimize default-on builds
Date:   Tue, 24 Mar 2020 13:32:28 -0700
Message-Id: <20200324203231.64324-3-keescook@chromium.org>
In-Reply-To: <20200324203231.64324-1-keescook@chromium.org>
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Right now, the state of CONFIG_INIT_ON_ALLOC_DEFAULT_ON (and
...ON_FREE...) did not change the assembly ordering of the static branch
tests. Use the new jump_label macro to check CONFIG settings to default
to the "expected" state, unpessimizes the resulting assembly code.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 include/linux/mm.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 059658604dd6..64e911159ffa 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2665,7 +2665,8 @@ static inline void kernel_poison_pages(struct page *page, int numpages,
 DECLARE_STATIC_KEY_MAYBE(CONFIG_INIT_ON_ALLOC_DEFAULT_ON, init_on_alloc);
 static inline bool want_init_on_alloc(gfp_t flags)
 {
-	if (static_branch_unlikely(&init_on_alloc) &&
+	if (static_branch_maybe(CONFIG_INIT_ON_ALLOC_DEFAULT_ON,
+				&init_on_alloc) &&
 	    !page_poisoning_enabled())
 		return true;
 	return flags & __GFP_ZERO;
@@ -2674,7 +2675,8 @@ static inline bool want_init_on_alloc(gfp_t flags)
 DECLARE_STATIC_KEY_MAYBE(CONFIG_INIT_ON_FREE_DEFAULT_ON, init_on_free);
 static inline bool want_init_on_free(void)
 {
-	return static_branch_unlikely(&init_on_free) &&
+	return static_branch_maybe(CONFIG_INIT_ON_FREE_DEFAULT_ON,
+				   &init_on_free) &&
 	       !page_poisoning_enabled();
 }
 
-- 
2.20.1