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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 A2168C433E7 for ; Tue, 13 Oct 2020 18:44:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 557C92145D for ; Tue, 13 Oct 2020 18:44:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731632AbgJMSn7 (ORCPT ); Tue, 13 Oct 2020 14:43:59 -0400 Received: from mga04.intel.com ([192.55.52.120]:20642 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726481AbgJMSn7 (ORCPT ); Tue, 13 Oct 2020 14:43:59 -0400 IronPort-SDR: Kjaudnb4Km4UOzFkEr78oOwAKMo2j6Fby2qry6+9jgA6PlRX2rZACZ6cQcR9GnHz7W71ruYfdL 5ckJfzbkK+4Q== X-IronPort-AV: E=McAfee;i="6000,8403,9773"; a="163326911" X-IronPort-AV: E=Sophos;i="5.77,371,1596524400"; d="scan'208";a="163326911" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Oct 2020 11:43:58 -0700 IronPort-SDR: Y8yr31bWt2D5ZFUro2P0qp+6A5viSF0HAT183NiudA8pSe1LDbuRDA7sOocHWIOtV1Xh+MKs9o UAAH72LnMERw== X-IronPort-AV: E=Sophos;i="5.77,371,1596524400"; d="scan'208";a="346281329" Received: from murawskx-mobl.amr.corp.intel.com (HELO [10.209.9.29]) ([10.209.9.29]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Oct 2020 11:43:58 -0700 Subject: Re: [PATCH RFC V3 5/9] x86/pks: Add PKS kernel API To: ira.weiny@intel.com, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andy Lutomirski , Peter Zijlstra Cc: Fenghua Yu , x86@kernel.org, Dave Hansen , Dan Williams , Andrew Morton , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org References: <20201009194258.3207172-1-ira.weiny@intel.com> <20201009194258.3207172-6-ira.weiny@intel.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201009194258.3207172-6-ira.weiny@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > +static inline void pks_update_protection(int pkey, unsigned long protection) > +{ > + current->thread.saved_pkrs = update_pkey_val(current->thread.saved_pkrs, > + pkey, protection); > + preempt_disable(); > + write_pkrs(current->thread.saved_pkrs); > + preempt_enable(); > +} Why does this need preempt count manipulation in addition to the get/put_cpu_var() inside of write_pkrs()? > +/** > + * PKS access control functions > + * > + * Change the access of the domain specified by the pkey. These are global > + * updates. They only affects the current running thread. It is undefined and > + * a bug for users to call this without having allocated a pkey and using it as > + * pkey here. > + * > + * pks_mknoaccess() > + * Disable all access to the domain > + * pks_mkread() > + * Make the domain Read only > + * pks_mkrdwr() > + * Make the domain Read/Write > + * > + * @pkey the pkey for which the access should change. > + * > + */ > +void pks_mknoaccess(int pkey) > +{ > + pks_update_protection(pkey, PKEY_DISABLE_ACCESS); > +} > +EXPORT_SYMBOL_GPL(pks_mknoaccess); These are named like PTE manipulation functions, which is kinda weird. What's wrong with: pks_disable_access(pkey) ? > +void pks_mkread(int pkey) > +{ > + pks_update_protection(pkey, PKEY_DISABLE_WRITE); > +} > +EXPORT_SYMBOL_GPL(pks_mkread); I really don't like this name. It doesn't make readable, or even read-only, *especially* if it was already access-disabled. > +static const char pks_key_user0[] = "kernel"; > + > +/* Store names of allocated keys for debug. Key 0 is reserved for the kernel. */ > +static const char *pks_key_users[PKS_NUM_KEYS] = { > + pks_key_user0 > +}; > + > +/* > + * Each key is represented by a bit. Bit 0 is set for key 0 and reserved for > + * its use. We use ulong for the bit operations but only 16 bits are used. > + */ > +static unsigned long pks_key_allocation_map = 1 << PKS_KERN_DEFAULT_KEY; > + > +/* > + * pks_key_alloc - Allocate a PKS key > + * > + * @pkey_user: String stored for debugging of key exhaustion. The caller is > + * responsible to maintain this memory until pks_key_free(). > + */ > +int pks_key_alloc(const char * const pkey_user) > +{ > + int nr; > + > + if (!cpu_feature_enabled(X86_FEATURE_PKS)) > + return -EINVAL; I'm not sure I like -EINVAL for this. I thought we returned -ENOSPC for this case for user pkeys. > + while (1) { > + nr = find_first_zero_bit(&pks_key_allocation_map, PKS_NUM_KEYS); > + if (nr >= PKS_NUM_KEYS) { > + pr_info("Cannot allocate supervisor key for %s.\n", > + pkey_user); > + return -ENOSPC; > + } > + if (!test_and_set_bit_lock(nr, &pks_key_allocation_map)) > + break; > + } > + > + /* for debugging key exhaustion */ > + pks_key_users[nr] = pkey_user; > + > + return nr; > +} > +EXPORT_SYMBOL_GPL(pks_key_alloc); > + > +/* > + * pks_key_free - Free a previously allocate PKS key > + * > + * @pkey: Key to be free'ed > + */ > +void pks_key_free(int pkey) > +{ > + if (!cpu_feature_enabled(X86_FEATURE_PKS)) > + return; > + > + if (pkey >= PKS_NUM_KEYS || pkey <= PKS_KERN_DEFAULT_KEY) > + return; This seems worthy of a WARN_ON_ONCE() at least. It's essentially corrupt data coming into a kernel API.