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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A795CC7EE25 for ; Fri, 9 Jun 2023 18:38:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231990AbjFISiL (ORCPT ); Fri, 9 Jun 2023 14:38:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49882 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230454AbjFIShq (ORCPT ); Fri, 9 Jun 2023 14:37:46 -0400 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2800B4231 for ; Fri, 9 Jun 2023 11:37:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1686335845; x=1717871845; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=G6sE0O+Ymn27nVkvLirQB/p1cOObowjit5BY1oI6ToA=; b=jqZausiQqiliZT/hXqP1O+IG1QdCGRCqzgWrrEe8TEy8Sl5kfHOYsi6g 4T+cUj4RkdnHs0PHC4uBbqTqZcNwApAJ9iXcSClMslTgXCSzobp/X2WQD iXWFSiHYcLAL+qNN1rH2lgAmJ8v41nqlv1wDS6Om4nNxdIjLvTTLe0Ofq YGDainiuXsUl/Ll4ort/wPu0Ja7QIvHCXXhYfoJn6vhDUVFqwEAC3SGQP 92I7bLghifsegjkT0c+96uXLNAkL/cNvPHNrR8+hyanKej7GpDKEqWP19 JjT0WQKPh33RQsiP0o1uMtM+GUOWhxE1ih3SMBwFX9Xsxhp8Y+UM1HJLn w==; X-IronPort-AV: E=McAfee;i="6600,9927,10736"; a="338022207" X-IronPort-AV: E=Sophos;i="6.00,230,1681196400"; d="scan'208";a="338022207" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Jun 2023 11:37:20 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10736"; a="710444098" X-IronPort-AV: E=Sophos;i="6.00,230,1681196400"; d="scan'208";a="710444098" Received: from black.fi.intel.com (HELO black.fi.intel.com.) ([10.237.72.28]) by orsmga002.jf.intel.com with ESMTP; 09 Jun 2023 11:37:17 -0700 From: Alexander Shishkin To: linux-kernel@vger.kernel.org, x86@kernel.org, Andy Lutomirski , Dave Hansen , Ravi Shankar , Tony Luck , Sohil Mehta Cc: Alexander Shishkin , Dave Hansen Subject: [PATCH v3 10/12] x86/vsyscall: Document the fact that vsyscall=emulate disables LASS Date: Fri, 9 Jun 2023 21:36:30 +0300 Message-Id: <20230609183632.48706-11-alexander.shishkin@linux.intel.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230609183632.48706-1-alexander.shishkin@linux.intel.com> References: <20230609183632.48706-1-alexander.shishkin@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Since EMULATE mode of vsyscall disables LASS, because fixing the LASS violations during the EMULATE mode would need complex instruction decoding, document this fact in kernel-parameters.txt. Cc: Andy Lutomirski Suggested-by: Dave Hansen Signed-off-by: Alexander Shishkin --- Documentation/admin-guide/kernel-parameters.txt | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 9e5bab29685f..efed9193107e 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -6850,7 +6850,9 @@ emulate Vsyscalls turn into traps and are emulated reasonably safely. The vsyscall page is - readable. + readable. This also disables the LASS + feature to allow userspace to poke around + the vsyscall page. xonly [default] Vsyscalls turn into traps and are emulated reasonably safely. The vsyscall -- 2.39.2