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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A6849C433F5 for ; Sun, 26 Sep 2021 15:12:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 86045610A2 for ; Sun, 26 Sep 2021 15:12:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232156AbhIZPNm (ORCPT ); Sun, 26 Sep 2021 11:13:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58322 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232168AbhIZPMu (ORCPT ); Sun, 26 Sep 2021 11:12:50 -0400 Received: from mail-pl1-x632.google.com (mail-pl1-x632.google.com [IPv6:2607:f8b0:4864:20::632]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7F1BDC061575 for ; Sun, 26 Sep 2021 08:11:10 -0700 (PDT) Received: by mail-pl1-x632.google.com with SMTP id x4so2493548pln.5 for ; Sun, 26 Sep 2021 08:11:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=82l7hm5ayFTY+bZsY9eWKZD25UHpS8vS8pRLVtykk+U=; b=WNRNa3XBWsZZGqFh+pOdrzf6bCIfdjgqcTgmn9dViAHUPtNHVpguxER1wdoiigE4+a NYRwaU/zjbMIqvA0SOzzlxx7AlTr2deax+ABmzLV7M86Xk0hlWhNUG1RXCDbdYD3Rh1k 1jXCYg7/+PqHohJhnI1WXkAtuBfI6EFnx7qZYwIuEexKZsjqfBe++uWKf2ZEUl5oqxss GsZyy5DOxcWT3CkAQhCA4C8xqyck7JTsWfhORa0VFEJDOuVlvl1GYvAt3L66U5gVIqlb 2/RRfVQTa5wvf+/xGh3VTNXWyxeegSnrc+PXl9AAXshtciywpoHyIpBfERMOICJi3LJg JzyQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=82l7hm5ayFTY+bZsY9eWKZD25UHpS8vS8pRLVtykk+U=; b=oVbn5k+nmlFEzXqJbn8uVEhh7Y64jSRJU+mRR2U5qe5xSr6kJOsashnM23d+lG1ff9 5r5u9XmJh96XSuKE6yq1hKwiGkt5W8Hq0wiwZpIVj+/A+EZby7I9YOhGuyu0eNcwlROQ qBOGr4LQtJHPLZD2aReYPNlqO6joVbH59z3hgnhRiXWPQqgU1xiawcodFWwwKXoZiRzw FINoW1kSHCT/JPSHPQTF4iFPL1mJqinS9oYiVw0vu2scx7xMj/WI4yD24uf2htuc0om0 BnaM2djvs2dctCYXiBYQCjXM54MiHCSdEuf5Mv+duoI2EkhyeU9vHhLVbFBkIJQHEjkI 4pwQ== X-Gm-Message-State: AOAM531ig1zIOuKu8iR+cVCVlqBkIb1xzqWSOoHSN05eQJAcwzx9u0zn bc9orYiEqa6/G/z1qkZhj5zj5V8SKMvtsA== X-Google-Smtp-Source: ABdhPJwmfpWfxJpGrtQJsCRNYJFIX55DvEVikDMltFU/yfbVJYe28Dfv7Ge6Xp4RiH7weX4AFl8gDQ== X-Received: by 2002:a17:90a:5895:: with SMTP id j21mr13945357pji.99.1632669069964; Sun, 26 Sep 2021 08:11:09 -0700 (PDT) Received: from localhost ([47.88.60.64]) by smtp.gmail.com with ESMTPSA id e2sm14920438pfn.141.2021.09.26.08.11.08 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sun, 26 Sep 2021 08:11:09 -0700 (PDT) From: Lai Jiangshan To: linux-kernel@vger.kernel.org Cc: Lai Jiangshan , Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" Subject: [PATCH V2 23/41] x86/entry: Add the C version ist_switch_to_kernel_gsbase() Date: Sun, 26 Sep 2021 23:08:20 +0800 Message-Id: <20210926150838.197719-24-jiangshanlai@gmail.com> X-Mailer: git-send-email 2.19.1.6.gb485710b In-Reply-To: <20210926150838.197719-1-jiangshanlai@gmail.com> References: <20210926150838.197719-1-jiangshanlai@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Lai Jiangshan It implements the second half of paranoid_entry() whose functionality is to switch to kernel gsbase. Not functional difference intended. Signed-off-by: Lai Jiangshan --- arch/x86/entry/entry64.c | 44 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) diff --git a/arch/x86/entry/entry64.c b/arch/x86/entry/entry64.c index b939b56d985d..1a0d5d703ad6 100644 --- a/arch/x86/entry/entry64.c +++ b/arch/x86/entry/entry64.c @@ -229,3 +229,47 @@ static __always_inline unsigned long get_percpu_base(void) return pcpu_unit_offsets; } #endif + +/* + * Handle GSBASE depends on the availability of FSGSBASE. + * + * Without FSGSBASE the kernel enforces that negative GSBASE + * values indicate kernel GSBASE. With FSGSBASE no assumptions + * can be made about the GSBASE value when entering from user + * space. + */ +static __always_inline unsigned long ist_switch_to_kernel_gsbase(void) +{ + unsigned long gsbase; + + if (static_cpu_has(X86_FEATURE_FSGSBASE)) { + /* + * Read the current GSBASE for return. + * Retrieve and set the current CPUs kernel GSBASE. + * + * The unconditional write to GS base below ensures that + * no subsequent loads based on a mispredicted GS base can + * happen, therefore no LFENCE is needed here. + */ + gsbase = rdgsbase(); + wrgsbase(get_percpu_base()); + return gsbase; + } + + gsbase = __rdmsr(MSR_GS_BASE); + + /* + * The kernel-enforced convention is a negative GSBASE indicates + * a kernel value. No SWAPGS needed on entry and exit. + */ + if ((long)gsbase < 0) { + kernel_entry_fence_no_swapgs(); + /* no SWAPGS required on exit */ + return 1; + } + + user_entry_swapgs_and_fence(); + + /* SWAPGS required on exit */ + return 0; +} -- 2.19.1.6.gb485710b