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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id ECD5EC4332F for ; Thu, 20 Oct 2022 11:30:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230443AbiJTLax (ORCPT ); Thu, 20 Oct 2022 07:30:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54244 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230435AbiJTLat (ORCPT ); Thu, 20 Oct 2022 07:30:49 -0400 Received: from mail.ispras.ru (mail.ispras.ru [83.149.199.84]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8C0A5194F9F; Thu, 20 Oct 2022 04:30:45 -0700 (PDT) Received: from mail.ispras.ru (unknown [83.149.199.84]) by mail.ispras.ru (Postfix) with ESMTPSA id E125A419E9C7; Thu, 20 Oct 2022 11:30:43 +0000 (UTC) DKIM-Filter: OpenDKIM Filter v2.11.0 mail.ispras.ru E125A419E9C7 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ispras.ru; s=default; t=1666265444; bh=oTHe40uiQ4sXkhkleFkcW8SP3I0jzmqEVmIO8mpwtzc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=fORPZHPJlxo41mqZ+v752ztBbOHrXyjuWzte82iIV+wfkbrZqMDhBZhjASqhDiTvl +EUUoAsBfpMcKSXJJe0AcSax1O1q8+S9MqXHVjY3GPP8V/ZtVo2EAhUwT7mfX4QcJD 54GgTHQ0fkJ3/IR8m9jyAtA5nH6tfuWv1MEn1zvo= MIME-Version: 1.0 Date: Thu, 20 Oct 2022 14:30:43 +0300 From: Evgeniy Baskov To: Ard Biesheuvel Cc: Borislav Petkov , Andy Lutomirski , Dave Hansen , Ingo Molnar , Peter Zijlstra , Thomas Gleixner , Alexey Khoroshilov , lvc-project@linuxtesting.org, x86@kernel.org, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH 05/16] x86/boot: Support 4KB pages for identity mapping In-Reply-To: References: <30135b246edca4185b3943d62e40dfc7f3740f71.1662459668.git.baskov@ispras.ru> User-Agent: Roundcube Webmail/1.4.4 Message-ID: <4bb7e962bb4745894f20f752c5e48382@ispras.ru> X-Sender: baskov@ispras.ru Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org On 2022-10-19 10:11, Ard Biesheuvel wrote: > On Tue, 6 Sept 2022 at 12:42, Evgeniy Baskov wrote: >> >> Current identity mapping code only supports 2M and 1G pages. >> 4KB pages are desirable for better memory protection granularity >> in compressed kernel code. >> >> Change identity mapping code to support 4KB pages and >> memory remapping with different attributes. >> >> Signed-off-by: Evgeniy Baskov > > This looks reasonable to me but someone on team-x86 will need to review > this. > > One nit below Thanks! > >> --- >> arch/x86/include/asm/init.h | 1 + >> arch/x86/mm/ident_map.c | 186 >> +++++++++++++++++++++++++++++------- >> 2 files changed, 155 insertions(+), 32 deletions(-) >> >> diff --git a/arch/x86/include/asm/init.h b/arch/x86/include/asm/init.h >> index 5f1d3c421f68..a8277ee82c51 100644 >> --- a/arch/x86/include/asm/init.h >> +++ b/arch/x86/include/asm/init.h >> @@ -8,6 +8,7 @@ struct x86_mapping_info { >> unsigned long page_flag; /* page flag for PMD or PUD >> entry */ >> unsigned long offset; /* ident mapping offset */ >> bool direct_gbpages; /* PUD level 1GB page support >> */ >> + bool allow_4kpages; /* Allow more granular >> mappings with 4K pages */ >> unsigned long kernpg_flag; /* kernel pagetable flag >> override */ >> }; >> >> diff --git a/arch/x86/mm/ident_map.c b/arch/x86/mm/ident_map.c >> index 968d7005f4a7..ad455d4ef595 100644 >> --- a/arch/x86/mm/ident_map.c >> +++ b/arch/x86/mm/ident_map.c >> @@ -2,26 +2,130 @@ >> /* >> * Helper routines for building identity mapping page tables. This is >> * included by both the compressed kernel and the regular kernel. >> + * > > Drop this change > >> */ >> >> -static void ident_pmd_init(struct x86_mapping_info *info, pmd_t >> *pmd_page, >> - unsigned long addr, unsigned long end) >> +static void ident_pte_init(struct x86_mapping_info *info, pte_t >> *pte_page, >> + unsigned long addr, unsigned long end, >> + unsigned long flags) >> { >> - addr &= PMD_MASK; >> - for (; addr < end; addr += PMD_SIZE) { >> + addr &= PAGE_MASK; >> + for (; addr < end; addr += PAGE_SIZE) { >> + pte_t *pte = pte_page + pte_index(addr); >> + >> + set_pte(pte, __pte((addr - info->offset) | flags)); >> + } >> +} >> + >> +pte_t *ident_split_large_pmd(struct x86_mapping_info *info, >> + pmd_t *pmdp, unsigned long page_addr) >> +{ >> + unsigned long pmd_addr, page_flags; >> + pte_t *pte; >> + >> + pte = (pte_t *)info->alloc_pgt_page(info->context); >> + if (!pte) >> + return NULL; >> + >> + pmd_addr = page_addr & PMD_MASK; >> + >> + /* Not a large page - clear PSE flag */ >> + page_flags = pmd_flags(*pmdp) & ~_PSE; >> + ident_pte_init(info, pte, pmd_addr, pmd_addr + PMD_SIZE, >> page_flags); >> + >> + return pte; >> +} >> + >> +static int ident_pmd_init(struct x86_mapping_info *info, pmd_t >> *pmd_page, >> + unsigned long addr, unsigned long end, >> + unsigned long flags) >> +{ >> + unsigned long next; >> + bool new_table = 0; >> + >> + for (; addr < end; addr = next) { >> pmd_t *pmd = pmd_page + pmd_index(addr); >> + pte_t *pte; >> >> - if (pmd_present(*pmd)) >> + next = (addr & PMD_MASK) + PMD_SIZE; >> + if (next > end) >> + next = end; >> + >> + /* >> + * Use 2M pages if 4k pages are not allowed or >> + * we are not mapping extra, i.e. address and size are >> aligned. >> + */ >> + >> + if (!info->allow_4kpages || >> + (!(addr & ~PMD_MASK) && next == addr + PMD_SIZE)) >> { >> + >> + pmd_t pmdval; >> + >> + addr &= PMD_MASK; >> + pmdval = __pmd((addr - info->offset) | flags | >> _PSE); >> + set_pmd(pmd, pmdval); >> continue; >> + } >> + >> + /* >> + * If currently mapped page is large, we need to split >> it. >> + * The case when we can remap 2M page to 2M page >> + * with different flags is already covered above. >> + * >> + * If there's nothing mapped to desired address, >> + * we need to allocate new page table. >> + */ >> >> - set_pmd(pmd, __pmd((addr - info->offset) | >> info->page_flag)); >> + if (pmd_large(*pmd)) { >> + pte = ident_split_large_pmd(info, pmd, addr); >> + new_table = 1; >> + } else if (!pmd_present(*pmd)) { >> + pte = (pte_t >> *)info->alloc_pgt_page(info->context); >> + new_table = 1; >> + } else { >> + pte = pte_offset_kernel(pmd, 0); >> + new_table = 0; >> + } >> + >> + if (!pte) >> + return -ENOMEM; >> + >> + ident_pte_init(info, pte, addr, next, flags); >> + >> + if (new_table) >> + set_pmd(pmd, __pmd(__pa(pte) | >> info->kernpg_flag)); >> } >> + >> + return 0; >> } >> >> + >> +pmd_t *ident_split_large_pud(struct x86_mapping_info *info, >> + pud_t *pudp, unsigned long page_addr) >> +{ >> + unsigned long pud_addr, page_flags; >> + pmd_t *pmd; >> + >> + pmd = (pmd_t *)info->alloc_pgt_page(info->context); >> + if (!pmd) >> + return NULL; >> + >> + pud_addr = page_addr & PUD_MASK; >> + >> + /* Not a large page - clear PSE flag */ >> + page_flags = pud_flags(*pudp) & ~_PSE; >> + ident_pmd_init(info, pmd, pud_addr, pud_addr + PUD_SIZE, >> page_flags); >> + >> + return pmd; >> +} >> + >> + >> static int ident_pud_init(struct x86_mapping_info *info, pud_t >> *pud_page, >> unsigned long addr, unsigned long end) >> { >> unsigned long next; >> + bool new_table = 0; >> + int result; >> >> for (; addr < end; addr = next) { >> pud_t *pud = pud_page + pud_index(addr); >> @@ -31,28 +135,39 @@ static int ident_pud_init(struct x86_mapping_info >> *info, pud_t *pud_page, >> if (next > end) >> next = end; >> >> + /* Use 1G pages only if forced, even if they are >> supported. */ >> if (info->direct_gbpages) { >> pud_t pudval; >> - >> - if (pud_present(*pud)) >> - continue; >> + unsigned long flags; >> >> addr &= PUD_MASK; >> - pudval = __pud((addr - info->offset) | >> info->page_flag); >> + flags = info->page_flag | _PSE; >> + pudval = __pud((addr - info->offset) | flags); >> + >> set_pud(pud, pudval); >> continue; >> } >> >> - if (pud_present(*pud)) { >> + if (pud_large(*pud)) { >> + pmd = ident_split_large_pud(info, pud, addr); >> + new_table = 1; >> + } else if (!pud_present(*pud)) { >> + pmd = (pmd_t >> *)info->alloc_pgt_page(info->context); >> + new_table = 1; >> + } else { >> pmd = pmd_offset(pud, 0); >> - ident_pmd_init(info, pmd, addr, next); >> - continue; >> + new_table = 0; >> } >> - pmd = (pmd_t *)info->alloc_pgt_page(info->context); >> + >> if (!pmd) >> return -ENOMEM; >> - ident_pmd_init(info, pmd, addr, next); >> - set_pud(pud, __pud(__pa(pmd) | info->kernpg_flag)); >> + >> + result = ident_pmd_init(info, pmd, addr, next, >> info->page_flag); >> + if (result) >> + return result; >> + >> + if (new_table) >> + set_pud(pud, __pud(__pa(pmd) | >> info->kernpg_flag)); >> } >> >> return 0; >> @@ -63,6 +178,7 @@ static int ident_p4d_init(struct x86_mapping_info >> *info, p4d_t *p4d_page, >> { >> unsigned long next; >> int result; >> + bool new_table = 0; >> >> for (; addr < end; addr = next) { >> p4d_t *p4d = p4d_page + p4d_index(addr); >> @@ -72,15 +188,14 @@ static int ident_p4d_init(struct x86_mapping_info >> *info, p4d_t *p4d_page, >> if (next > end) >> next = end; >> >> - if (p4d_present(*p4d)) { >> + if (!p4d_present(*p4d)) { >> + pud = (pud_t >> *)info->alloc_pgt_page(info->context); >> + new_table = 1; >> + } else { >> pud = pud_offset(p4d, 0); >> - result = ident_pud_init(info, pud, addr, >> next); >> - if (result) >> - return result; >> - >> - continue; >> + new_table = 0; >> } >> - pud = (pud_t *)info->alloc_pgt_page(info->context); >> + >> if (!pud) >> return -ENOMEM; >> >> @@ -88,19 +203,22 @@ static int ident_p4d_init(struct x86_mapping_info >> *info, p4d_t *p4d_page, >> if (result) >> return result; >> >> - set_p4d(p4d, __p4d(__pa(pud) | info->kernpg_flag)); >> + if (new_table) >> + set_p4d(p4d, __p4d(__pa(pud) | >> info->kernpg_flag)); >> } >> >> return 0; >> } >> >> -int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t >> *pgd_page, >> - unsigned long pstart, unsigned long >> pend) >> +int kernel_ident_mapping_init(struct x86_mapping_info *info, >> + pgd_t *pgd_page, unsigned long pstart, >> + unsigned long pend) >> { >> unsigned long addr = pstart + info->offset; >> unsigned long end = pend + info->offset; >> unsigned long next; >> int result; >> + bool new_table; >> >> /* Set the default pagetable flags if not supplied */ >> if (!info->kernpg_flag) >> @@ -117,20 +235,24 @@ int kernel_ident_mapping_init(struct >> x86_mapping_info *info, pgd_t *pgd_page, >> if (next > end) >> next = end; >> >> - if (pgd_present(*pgd)) { >> + if (!pgd_present(*pgd)) { >> + p4d = (p4d_t >> *)info->alloc_pgt_page(info->context); >> + new_table = 1; >> + } else { >> p4d = p4d_offset(pgd, 0); >> - result = ident_p4d_init(info, p4d, addr, >> next); >> - if (result) >> - return result; >> - continue; >> + new_table = 0; >> } >> >> - p4d = (p4d_t *)info->alloc_pgt_page(info->context); >> if (!p4d) >> return -ENOMEM; >> + >> result = ident_p4d_init(info, p4d, addr, next); >> if (result) >> return result; >> + >> + if (!new_table) >> + continue; >> + >> if (pgtable_l5_enabled()) { >> set_pgd(pgd, __pgd(__pa(p4d) | >> info->kernpg_flag)); >> } else { >> -- >> 2.35.1 >>