From patchwork Wed Sep 7 10:07:08 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Rutland X-Patchwork-Id: 75619 Delivered-To: patch@linaro.org Received: by 10.140.106.11 with SMTP id d11csp244201qgf; Wed, 7 Sep 2016 03:09:18 -0700 (PDT) X-Received: by 10.66.139.110 with SMTP id qx14mr81993115pab.101.1473242958693; Wed, 07 Sep 2016 03:09:18 -0700 (PDT) Return-Path: Received: from bombadil.infradead.org (bombadil.infradead.org. [2001:1868:205::9]) by mx.google.com with ESMTPS id 27si29041605pfk.163.2016.09.07.03.09.18 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 07 Sep 2016 03:09:18 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org designates 2001:1868:205::9 as permitted sender) client-ip=2001:1868:205::9; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org designates 2001:1868:205::9 as permitted sender) smtp.mailfrom=linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.85_2 #1 (Red Hat Linux)) id 1bhZmB-00086w-3X; Wed, 07 Sep 2016 10:08:15 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.85_2 #1 (Red Hat Linux)) id 1bhZlo-00082z-BS for linux-arm-kernel@lists.infradead.org; Wed, 07 Sep 2016 10:07:53 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 11F25A5E; Wed, 7 Sep 2016 03:07:36 -0700 (PDT) Received: from leverpostej.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 7F15E3F21A; Wed, 7 Sep 2016 03:07:34 -0700 (PDT) From: Mark Rutland To: linux-arm-kernel@lists.infradead.org Subject: [PATCH 1/3] arm64: alternative: add auto-nop infrastructure Date: Wed, 7 Sep 2016 11:07:08 +0100 Message-Id: <1473242830-26246-2-git-send-email-mark.rutland@arm.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1473242830-26246-1-git-send-email-mark.rutland@arm.com> References: <1473242830-26246-1-git-send-email-mark.rutland@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20160907_030752_451258_82CF306B X-CRM114-Status: GOOD ( 13.57 ) X-Spam-Score: -8.3 (--------) X-Spam-Report: SpamAssassin version 3.4.0 on bombadil.infradead.org summary: Content analysis details: (-8.3 points) pts rule name description ---- ---------------------- -------------------------------------------------- -5.0 RCVD_IN_DNSWL_HI RBL: Sender listed at http://www.dnswl.org/, high trust [217.140.101.70 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record -1.4 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, marc.zyngier@arm.com, andre.przywara@arm.com, will.deacon@arm.com, dave.martin@arm.com, james.morse@arm.com, catalin.marinas@arm.com, kvmarm@lists.cs.columbia.edu, christoffer.dall@linaro.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org In some cases, one side of an alternative sequence is simply a number of NOPs used to balance the other side. Keeping track of this manually is tedious, and the presence of large chains of NOPs makes the code more painful to read than necessary. To ameliorate matters, this patch adds a new alternative_else_nop_endif, which automatically balances an alternative sequence with a trivial NOP sled. In many cases, we would like a NOP-sled in the default case, and instructions patched in in the presence of a feature. To enable the NOPs to be generated automatically for this case, this patch also adds a new alternative_if, and updates alternative_else and alternative_endif to work with either alternative_if or alternative_endif. Signed-off-by: Mark Rutland Cc: Andre Przywara Cc: Catalin Marinas Cc: Dave Martin Cc: James Morse Cc: Will Deacon --- arch/arm64/include/asm/alternative.h | 71 +++++++++++++++++++++++++++--------- 1 file changed, 54 insertions(+), 17 deletions(-) -- 1.9.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel diff --git a/arch/arm64/include/asm/alternative.h b/arch/arm64/include/asm/alternative.h index 8746ff6..4ddbf1c 100644 --- a/arch/arm64/include/asm/alternative.h +++ b/arch/arm64/include/asm/alternative.h @@ -90,34 +90,55 @@ void apply_alternatives(void *start, size_t length); .endm /* - * Begin an alternative code sequence. + * Alternative sequences + * + * The code for the case where the capability is not present will be + * assembled and linked as normal. There are no restrictions on this + * code. + * + * The code for the case where the capability is present will be + * assembled into a special section to be used for dynamic patching. + * Code for that case must: + * + * 1. Be exactly the same length (in bytes) as the default code + * sequence. * - * The code that follows this macro will be assembled and linked as - * normal. There are no restrictions on this code. + * 2. Not contain a branch target that is used outside of the + * alternative sequence it is defined in (branches into an + * alternative sequence are not fixed up). + */ + +/* + * Begin an alternative code sequence. */ .macro alternative_if_not cap + .set .Lasm_alt_mode, 0 .pushsection .altinstructions, "a" altinstruction_entry 661f, 663f, \cap, 662f-661f, 664f-663f .popsection 661: .endm +.macro alternative_if cap + .set .Lasm_alt_mode, 1 + .pushsection .altinstructions, "a" + altinstruction_entry 663f, 661f, \cap, 664f-663f, 662f-661f + .popsection + .pushsection .altinstr_replacement, "ax" + .align 2 /* So GAS knows label 661 is suitably aligned */ +661: +.endm + /* - * Provide the alternative code sequence. - * - * The code that follows this macro is assembled into a special - * section to be used for dynamic patching. Code that follows this - * macro must: - * - * 1. Be exactly the same length (in bytes) as the default code - * sequence. - * - * 2. Not contain a branch target that is used outside of the - * alternative sequence it is defined in (branches into an - * alternative sequence are not fixed up). + * Provide the other half of the alternative code sequence. */ .macro alternative_else -662: .pushsection .altinstr_replacement, "ax" +662: + .if .Lasm_alt_mode==0 + .pushsection .altinstr_replacement, "ax" + .else + .popsection + .endif 663: .endm @@ -125,11 +146,27 @@ void apply_alternatives(void *start, size_t length); * Complete an alternative code sequence. */ .macro alternative_endif -664: .popsection +664: + .if .Lasm_alt_mode==0 + .popsection + .endif .org . - (664b-663b) + (662b-661b) .org . - (662b-661b) + (664b-663b) .endm +/* + * Provides a trivial alternative or default sequence consisting solely + * of NOPs. The number of NOPs is chosen automatically to match the + * previous case. + */ +.macro alternative_else_nop_endif +alternative_else +.rept (662b-661b) / 4 + nop +.endr +alternative_endif +.endm + #define _ALTERNATIVE_CFG(insn1, insn2, cap, cfg, ...) \ alternative_insn insn1, insn2, cap, IS_ENABLED(cfg)