From patchwork Tue Oct 27 13:45:45 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 312652 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=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, 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 9A8A9C388F9 for ; Tue, 27 Oct 2020 15:21:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 536292224A for ; Tue, 27 Oct 2020 15:21:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603812114; bh=dEldMgnZTCIzZ1Zh52EVtedfksIUyT/q4ZLdb6Y2hxc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=clSpXJAK4yijWN7dyYqx5DBDdY3vMvHLn9UIomJDQIcwFDezlb3BAioMaPQz79N1P zQRbIRlpOj89hoaEssdbDYlqffoegdQXN4R9ofJNgF2MCr/uaAaa2SQVlHx9gnVW/7 +jRTvpVCR+NNCTuZYz07eS7Hcv8yaEPD7P9x29F0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1797154AbgJ0PVx (ORCPT ); Tue, 27 Oct 2020 11:21:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:36534 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1797144AbgJ0PVv (ORCPT ); Tue, 27 Oct 2020 11:21:51 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 96F0A20657; Tue, 27 Oct 2020 15:21:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603812109; bh=dEldMgnZTCIzZ1Zh52EVtedfksIUyT/q4ZLdb6Y2hxc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Xj4S0UfFY9qED6ZTsUyhXkMa1XjtP1PE1kLdXj8cdeeHXHa4Ay5jtzJdsq2cdogld 6EIHi0ONokshU8GhenqJ2Ax9sYCluH2hRXidbtiAtrceHdYg1GdL7x+fVQKanScVaE p1xRivSYGCpFip+1SWdZ8JrUNkbnF/aPdD9EVWMg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Arvind Sankar , Borislav Petkov , Sasha Levin Subject: [PATCH 5.9 095/757] x86/fpu: Allow multiple bits in clearcpuid= parameter Date: Tue, 27 Oct 2020 14:45:45 +0100 Message-Id: <20201027135455.004084066@linuxfoundation.org> X-Mailer: git-send-email 2.29.1 In-Reply-To: <20201027135450.497324313@linuxfoundation.org> References: <20201027135450.497324313@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Arvind Sankar [ Upstream commit 0a4bb5e5507a585532cc413125b921c8546fc39f ] Commit 0c2a3913d6f5 ("x86/fpu: Parse clearcpuid= as early XSAVE argument") changed clearcpuid parsing from __setup() to cmdline_find_option(). While the __setup() function would have been called for each clearcpuid= parameter on the command line, cmdline_find_option() will only return the last one, so the change effectively made it impossible to disable more than one bit. Allow a comma-separated list of bit numbers as the argument for clearcpuid to allow multiple bits to be disabled again. Log the bits being disabled for informational purposes. Also fix the check on the return value of cmdline_find_option(). It returns -1 when the option is not found, so testing as a boolean is incorrect. Fixes: 0c2a3913d6f5 ("x86/fpu: Parse clearcpuid= as early XSAVE argument") Signed-off-by: Arvind Sankar Signed-off-by: Borislav Petkov Link: https://lkml.kernel.org/r/20200907213919.2423441-1-nivedita@alum.mit.edu Signed-off-by: Sasha Levin --- .../admin-guide/kernel-parameters.txt | 2 +- arch/x86/kernel/fpu/init.c | 30 ++++++++++++++----- 2 files changed, 23 insertions(+), 9 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index a1068742a6df1..ffe864390c5ac 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -577,7 +577,7 @@ loops can be debugged more effectively on production systems. - clearcpuid=BITNUM [X86] + clearcpuid=BITNUM[,BITNUM...] [X86] Disable CPUID feature X for the kernel. See arch/x86/include/asm/cpufeatures.h for the valid bit numbers. Note the Linux specific bits are not necessarily diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c index 61ddc3a5e5c2b..f8ff895aaf7e1 100644 --- a/arch/x86/kernel/fpu/init.c +++ b/arch/x86/kernel/fpu/init.c @@ -243,9 +243,9 @@ static void __init fpu__init_system_ctx_switch(void) */ static void __init fpu__init_parse_early_param(void) { - char arg[32]; + char arg[128]; char *argptr = arg; - int bit; + int arglen, res, bit; #ifdef CONFIG_X86_32 if (cmdline_find_option_bool(boot_command_line, "no387")) @@ -268,12 +268,26 @@ static void __init fpu__init_parse_early_param(void) if (cmdline_find_option_bool(boot_command_line, "noxsaves")) setup_clear_cpu_cap(X86_FEATURE_XSAVES); - if (cmdline_find_option(boot_command_line, "clearcpuid", arg, - sizeof(arg)) && - get_option(&argptr, &bit) && - bit >= 0 && - bit < NCAPINTS * 32) - setup_clear_cpu_cap(bit); + arglen = cmdline_find_option(boot_command_line, "clearcpuid", arg, sizeof(arg)); + if (arglen <= 0) + return; + + pr_info("Clearing CPUID bits:"); + do { + res = get_option(&argptr, &bit); + if (res == 0 || res == 3) + break; + + /* If the argument was too long, the last bit may be cut off */ + if (res == 1 && arglen >= sizeof(arg)) + break; + + if (bit >= 0 && bit < NCAPINTS * 32) { + pr_cont(" " X86_CAP_FMT, x86_cap_flag(bit)); + setup_clear_cpu_cap(bit); + } + } while (res == 2); + pr_cont("\n"); } /*