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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id w23sm106967pgi.63.2021.03.30.13.57.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Mar 2021 13:57:53 -0700 (PDT) From: Kees Cook To: Thomas Gleixner Cc: Kees Cook , Peter Zijlstra , Elena Reshetova , x86@kernel.org, Andy Lutomirski , Catalin Marinas , Will Deacon , Mark Rutland , Alexander Potapenko , Alexander Popov , Ard Biesheuvel , Jann Horn , Vlastimil Babka , David Hildenbrand , Mike Rapoport , Andrew Morton , Jonathan Corbet , Randy Dunlap , kernel-hardening@lists.openwall.com, linux-hardening@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v8 1/6] jump_label: Provide CONFIG-driven build state defaults Date: Tue, 30 Mar 2021 13:57:45 -0700 Message-Id: <20210330205750.428816-2-keescook@chromium.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210330205750.428816-1-keescook@chromium.org> References: <20210330205750.428816-1-keescook@chromium.org> MIME-Version: 1.0 X-Patch-Hashes: v=1; h=sha256; g=aa54c44d1d71b9550d6015efc734f667917094a1; i=Vishx6UyAXwYzcnoSyP+eBB3iQyx+/i5smsbQfc0cnA=; m=vc4sSYlf+uaSlLSFP5TpbQv56VaSRpBLpRuMltXaB4Q=; p=mNH2Bo/K9vrGz9sBtTDV8UFO0eJ8yv8BbR/DeIaO1es= X-Patch-Sig: m=pgp; i=keescook@chromium.org; s=0x0x8972F4DFDC6DC026; b=iQIzBAABCgAdFiEEpcP2jyKd1g9yPm4TiXL039xtwCYFAmBjkMwACgkQiXL039xtwCaWexAAp34 ok/GqKys22n/+Xt+9QrE/sBFj+uvgYjI14mqH/xkZoouYd5+myYJn0h/B8R83n48nwB7KdYtukzVv nSela//6I+ohCNhjgEt1TmUc81qTISl5q5mxbq/+IAPNVqlXEYCpTcSFkBbr5tbXOoOrbkI87vrja az8w6YyJGWbCBm/PpNK/FqvgxnWKMmJbomwDiBeWSgEfJUSD/M/r6PV1RhbK2mt7AniDqOPJ/oRG0 VB6GcbfW106hXfwKjmeqoce8yTv7YrC4mYL5sKA0yV/H62mmU9vkUtd+/0x07Cg1iXFAbg3bkDu/i hQkdH1ZBkjnjcWQJ6pvYBfHR+5Fblp8ibFwpPJc/hJmGkzxTde5pAlM3s4FMdtv++qD7bvL2tdXIS kzkw4HJRrjKMET9L3sAWvlSZgUTAip8wslmfIZUVea7HUy5ypoFIvSxHL5BNOGiTBp0zWwvXAzNt1 PTrOAP9fZKIsGI0Nj6laG2wpUdzjTpYcjfNxIPtygIIqheWGFwHwPYpWV0g8700cR/heR7qoBa0zt nrQX1WU7AUkaYROLg1QVWr13bMVlZZuDsSPfvsu3yo8alzHhY8xaryuKCwuTzY8ResHzU6XIqkmJb J1b8qCZ973eAn1T3KbVOk18YcqsShZ8C4SwIbyGOuesFrhes7bPZf/GqTx2MNcoU= X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: BB7A680192D9 X-Stat-Signature: ife7zacp1z5x9gg9jnunu8d3pehpher7 Received-SPF: none (chromium.org>: No applicable sender policy available) receiver=imf27; identity=mailfrom; envelope-from=""; helo=mail-pj1-f44.google.com; client-ip=209.85.216.44 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617137874-145995 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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/tr= ee/include/linux/jump_label.h?h=3Dv5.11#n398 Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/lkml/20200324220641.GT2452@worktop.programm= ing.kicks-ass.net/ Signed-off-by: Kees Cook --- 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] =3D STATIC_KEY_FALSE_INIT, \ } =20 +#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); =20 #define static_key_enabled(x) \ @@ -482,6 +497,10 @@ extern bool ____wrong_branch_error(void); =20 #endif /* CONFIG_JUMP_LABEL */ =20 +#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 !=3D 0 */ --=20 2.25.1