From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f198.google.com (mail-wr0-f198.google.com [209.85.128.198]) by kanga.kvack.org (Postfix) with ESMTP id 5796C6B028A for ; Fri, 16 Mar 2018 15:31:34 -0400 (EDT) Received: by mail-wr0-f198.google.com with SMTP id w10so2958763wrg.15 for ; Fri, 16 Mar 2018 12:31:34 -0700 (PDT) Received: from theia.8bytes.org (8bytes.org. [81.169.241.247]) by mx.google.com with ESMTPS id e1si1298454edc.321.2018.03.16.12.30.09 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 16 Mar 2018 12:30:09 -0700 (PDT) From: Joerg Roedel Subject: [PATCH 26/35] x86/mm/pti: Clone CPU_ENTRY_AREA on PMD level on x86_32 Date: Fri, 16 Mar 2018 20:29:44 +0100 Message-Id: <1521228593-3820-27-git-send-email-joro@8bytes.org> In-Reply-To: <1521228593-3820-1-git-send-email-joro@8bytes.org> References: <1521228593-3820-1-git-send-email-joro@8bytes.org> Sender: owner-linux-mm@kvack.org List-ID: To: Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Linus Torvalds , Andy Lutomirski , Dave Hansen , Josh Poimboeuf , Juergen Gross , Peter Zijlstra , Borislav Petkov , Jiri Kosina , Boris Ostrovsky , Brian Gerst , David Laight , Denys Vlasenko , Eduardo Valentin , Greg KH , Will Deacon , aliguori@amazon.com, daniel.gruss@iaik.tugraz.at, hughd@google.com, keescook@google.com, Andrea Arcangeli , Waiman Long , Pavel Machek , jroedel@suse.de, joro@8bytes.org From: Joerg Roedel Cloning on the P4D level would clone the complete kernel address space into the user-space page-tables for PAE kernels. Cloning on PMD level is fine for PAE and legacy paging. Signed-off-by: Joerg Roedel --- arch/x86/mm/pti.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index 96a690e..3ffd923 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -312,6 +312,7 @@ pti_clone_pmds(unsigned long start, unsigned long end, pmdval_t clear) } } +#ifdef CONFIG_X86_64 /* * Clone a single p4d (i.e. a top-level entry on 4-level systems and a * next-level entry on 5-level systems. @@ -335,6 +336,25 @@ static void __init pti_clone_user_shared(void) pti_clone_p4d(CPU_ENTRY_AREA_BASE); } +#else /* CONFIG_X86_64 */ + +/* + * On 32 bit PAE systems with 1GB of Kernel address space there is only + * one pgd/p4d for the whole kernel. Cloning that would map the whole + * address space into the user page-tables, making PTI useless. So clone + * the page-table on the PMD level to prevent that. + */ +static void __init pti_clone_user_shared(void) +{ + unsigned long start, end; + + start = CPU_ENTRY_AREA_BASE; + end = start + (PAGE_SIZE * CPU_ENTRY_AREA_PAGES); + + pti_clone_pmds(start, end, _PAGE_GLOBAL); +} +#endif /* CONFIG_X86_64 */ + /* * Clone the ESPFIX P4D into the user space visinble page table */ -- 2.7.4