From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755251AbeDDBOj (ORCPT ); Tue, 3 Apr 2018 21:14:39 -0400 Received: from mga07.intel.com ([134.134.136.100]:26742 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754890AbeDDBMn (ORCPT ); Tue, 3 Apr 2018 21:12:43 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.48,403,1517904000"; d="scan'208";a="217321571" Subject: [PATCH 04/11] x86/espfix: document use of _PAGE_GLOBAL To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Dave Hansen , aarcange@redhat.com, luto@kernel.org, torvalds@linux-foundation.org, keescook@google.com, hughd@google.com, jgross@suse.com, x86@kernel.org, namit@vmware.com From: Dave Hansen Date: Tue, 03 Apr 2018 18:09:56 -0700 References: <20180404010946.6186729B@viggo.jf.intel.com> In-Reply-To: <20180404010946.6186729B@viggo.jf.intel.com> Message-Id: <20180404010956.32C1983F@viggo.jf.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dave Hansen The "normal" kernel page table creation mechanisms using PAGE_KERNEL_* page protections will never set _PAGE_GLOBAL with PTI. The few places in the kernel that always want _PAGE_GLOBAL must avoid using PAGE_KERNEL_*. Document that we want it here and its use is not accidental. Signed-off-by: Dave Hansen Cc: Andrea Arcangeli Cc: Andy Lutomirski Cc: Linus Torvalds Cc: Kees Cook Cc: Hugh Dickins Cc: Juergen Gross Cc: x86@kernel.org Cc: Nadav Amit --- b/arch/x86/kernel/espfix_64.c | 4 ++++ 1 file changed, 4 insertions(+) diff -puN arch/x86/kernel/espfix_64.c~espfix-use-kern-defaults-not-supported arch/x86/kernel/espfix_64.c --- a/arch/x86/kernel/espfix_64.c~espfix-use-kern-defaults-not-supported 2018-04-02 16:41:14.274605175 -0700 +++ b/arch/x86/kernel/espfix_64.c 2018-04-02 16:41:14.278605175 -0700 @@ -195,6 +195,10 @@ void init_espfix_ap(int cpu) pte_p = pte_offset_kernel(&pmd, addr); stack_page = page_address(alloc_pages_node(node, GFP_KERNEL, 0)); + /* + * __PAGE_KERNEL_* includes _PAGE_GLOBAL, which we want since + * this is mapped to userspace. + */ pte = __pte(__pa(stack_page) | ((__PAGE_KERNEL_RO | _PAGE_ENC) & ptemask)); for (n = 0; n < ESPFIX_PTE_CLONES; n++) set_pte(&pte_p[n*PTE_STRIDE], pte); _