From nobody Mon Feb 9 00:53:43 2026 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 E12ACC77B73 for ; Tue, 30 May 2023 11:44:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229919AbjE3Lol (ORCPT ); Tue, 30 May 2023 07:44:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47108 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231612AbjE3Lnx (ORCPT ); Tue, 30 May 2023 07:43:53 -0400 Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3400C10A for ; Tue, 30 May 2023 04:43:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1685447027; x=1716983027; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=G6sE0O+Ymn27nVkvLirQB/p1cOObowjit5BY1oI6ToA=; b=f5R9XvEhb/2REO+NeYiPiiMcBopys3UhLtgj9Orier8PgHxKr5HeMkdB 6f0kKiHSR0TtHkNgAgiGzcTK8NsGa51uRRkNp/U8MHKuqIGAdMT3Tqx8W xTisDAJbFErEQ8AmB1cc2/9hF0jrinvz4p7Vg6dvHu0yjKqRDIJ+zl9LE e+OlPiYaRcrl0nbBAHvuzUoXnphneM06SPaBW0Bevy/G9wh01uXy3oWjT C2FH7RswwAK5KUrkLDgTRwux3sVjlZzgoMddjhkvxcPqO2YRM59ulCuic hw2N12nlwkLpvhcfEKDEzZGufHJxdHILzJ4o7HPTQitDSrnE9uopMw1vo A==; X-IronPort-AV: E=McAfee;i="6600,9927,10725"; a="383145399" X-IronPort-AV: E=Sophos;i="6.00,204,1681196400"; d="scan'208";a="383145399" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 May 2023 04:43:23 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10725"; a="700588765" X-IronPort-AV: E=Sophos;i="6.00,204,1681196400"; d="scan'208";a="700588765" Received: from black.fi.intel.com (HELO black.fi.intel.com.) ([10.237.72.28]) by orsmga007.jf.intel.com with ESMTP; 30 May 2023 04:43:20 -0700 From: Alexander Shishkin To: linux-kernel@vger.kernel.org, x86@kernel.org, Andy Lutomirski , Dave Hansen , Ravi Shankar , Tony Luck , Sohil Mehta , Paul Lai Cc: Alexander Shishkin , Dave Hansen Subject: [PATCH v2 10/12] x86/vsyscall: Document the fact that vsyscall=emulate disables LASS Date: Tue, 30 May 2023 14:42:45 +0300 Message-Id: <20230530114247.21821-11-alexander.shishkin@linux.intel.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230530114247.21821-1-alexander.shishkin@linux.intel.com> References: <20230530114247.21821-1-alexander.shishkin@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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/Documentatio= n/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 @@ =20 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. =20 xonly [default] Vsyscalls turn into traps and are emulated reasonably safely. The vsyscall --=20 2.39.2