From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B6E9FC433DF for ; Thu, 27 Aug 2020 16:49:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 96D1A22CE3 for ; Thu, 27 Aug 2020 16:49:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="EakLQnPF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727906AbgH0QtY (ORCPT ); Thu, 27 Aug 2020 12:49:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51858 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727882AbgH0QtQ (ORCPT ); Thu, 27 Aug 2020 12:49:16 -0400 Received: from mail-ej1-x641.google.com (mail-ej1-x641.google.com [IPv6:2a00:1450:4864:20::641]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3CCB2C061264 for ; Thu, 27 Aug 2020 09:49:15 -0700 (PDT) Received: by mail-ej1-x641.google.com with SMTP id d11so8519296ejt.13 for ; Thu, 27 Aug 2020 09:49:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=b5mt7pQURye9ecR53f+JvCJ0uiGgMxCegvnwnLRHzLo=; b=EakLQnPFKi98TUfE+RqWCoPr3r9CgBHj/DV4tdU3T4twCuQndAB4O6iUrgVlxPMdG7 Gq+nZwxk2bEnY3RiAyb/670KKTFQ0Af+huh57E6sdJBMdVTpwYembXC1o5Qgva629mQD 4tlkzj2lXMfrkUNxIVfc7JZ+viH55An4qkeoveT7/DFtgwZTWY7gox8VZKgFqoYB7uT2 BHUAM0GHQGixfKeI3oxt5HuQNAKWsXIjL2gEI3mvJP8SEqt1FDhkT11PgEP5a4MoTUNv PzEL2SMLy5LsZOIN27+GoJY6okVQmW1Yo8uudbRtDxQ3O7CYHSHd4bga6oys58LM0wuC RTdg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=b5mt7pQURye9ecR53f+JvCJ0uiGgMxCegvnwnLRHzLo=; b=swXSVkkCvWVT6l58KBbYm+h733mL17rIZ0vVNMz/pxXHcFfarrgh+JQHM5V3Ew90JL 5CdhGN/E/6mscN1n/kQPyoABcOsfsddEEVaZBkgSIt2T+DOtn3z4YCMZLs8g28oKxnp/ lBrVFomr8dY83enDthpKsXKRJ/ruVY4P68JLLRdYpB4+VVJMyvxSGd8TEb62BxpvJNQW GuDAy4in74iuJVkrn6n2WTKSkvorpr0Sk4RGK4R7uRp9bhIcV6syWhfKQhZ9eoE9iNSI q5ClUSk+cjGzfTKah3zeidfJ2CvuXqm+U5AAj33dYYUa6PcMZBqva0Ytgj7FDs7ir0sa pusQ== X-Gm-Message-State: AOAM533ha1XaoPlEl6JXBppdDExq0+gzjb2MBbTdqEOPCfAajGCpKMrj PuCqyd9u+5F7EdQ2PelhNnU= X-Google-Smtp-Source: ABdhPJw0ClNIO9jd/shZgALigC7aDMkBNZ2ND8Oqiy6UAgf7eU77ImYjD2vtFD8Xqrm4zCfIUaKk7g== X-Received: by 2002:a17:907:271a:: with SMTP id w26mr18415996ejk.402.1598546953816; Thu, 27 Aug 2020 09:49:13 -0700 (PDT) Received: from localhost.localdomain (93-103-18-160.static.t-2.net. [93.103.18.160]) by smtp.gmail.com with ESMTPSA id lx15sm2285182ejb.66.2020.08.27.09.49.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Aug 2020 09:49:13 -0700 (PDT) From: Uros Bizjak To: x86@kernel.org, linux-kernel@vger.kernel.org Cc: Uros Bizjak , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" Subject: [PATCH] x86: Use XORL r32,r32 in __get_user_asm Date: Thu, 27 Aug 2020 18:49:05 +0200 Message-Id: <20200827164905.88235-1-ubizjak@gmail.com> X-Mailer: git-send-email 2.26.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Use XORL r32,r32 for all operand sizes. x86_64 zero extends 32bit operations, so for 64bit operands, XORL r32,r32 is functionally equal to XORL r64,r64, but avoids a REX prefix byte when legacy registers are used. 32bit operation also avoids 0x66 size prefix for 16bit operands and REX prefix when %sil, %dil and %bpl 8bit registers are used. As a bonus, 32bit XORL breaks register dependency chains, avoiding potential partial register stalls with 8 and 16bit operands. The patch lowers the size of .fixup section by 20 bytes. Signed-off-by: Uros Bizjak Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: "H. Peter Anvin" --- arch/x86/include/asm/uaccess.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index ecefaffd15d4..2bffba2a1b23 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -343,7 +343,7 @@ do { \ "2:\n" \ ".section .fixup,\"ax\"\n" \ "3: mov %[efault],%[errout]\n" \ - " xor"itype" %[output],%[output]\n" \ + " xorl %k[output],%k[output]\n" \ " jmp 2b\n" \ ".previous\n" \ _ASM_EXTABLE_UA(1b, 3b) \ -- 2.26.2