From patchwork Mon Jun 13 14:45:31 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ard Biesheuvel X-Patchwork-Id: 12879901 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 0F60FC433EF for ; Mon, 13 Jun 2022 18:31:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244881AbiFMSbF (ORCPT ); Mon, 13 Jun 2022 14:31:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55708 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245582AbiFMSau (ORCPT ); Mon, 13 Jun 2022 14:30:50 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A668FB5780 for ; Mon, 13 Jun 2022 07:46:23 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 3AE1DB81058 for ; Mon, 13 Jun 2022 14:46:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 06EF4C341C7; Mon, 13 Jun 2022 14:46:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1655131581; bh=OhKluuvrPX/ZIKI6cSSrnjwjMiDdvqkJIcBzUOSbddk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=D/UfUVUaH1ovxR820aTzGba59k83AkXAuugCzGUdqM3E8Esk7X/UiOvMWhqm7cMwS O43BEMkIhWLNjEF//ZpU/EEtxsheNB71hbHxVjJanMv03P8FjX84Gabjm4781a0Jdw 2QfZHj/SvDF4Q2J5pexDtWkN56MvlewnvVRtqpH0mtnMc/zdFc2/DwqcQSQxX+vvGU aTCZfyBARcbw1CeBvt3CMJx1aCoAhg0tYeptrnrh9DobSyu03szbV9lpItLd0xPYtm 9Fdx3RocD3RFYeAwRVF/uzPGF+8VIj4fg2zmEUXePYh+tHRe0Fd87e0QP45DZH88r5 OiY3NZjIuA7Ug== From: Ard Biesheuvel To: linux-arm-kernel@lists.infradead.org Cc: linux-hardening@vger.kernel.org, Ard Biesheuvel , Marc Zyngier , Will Deacon , Mark Rutland , Kees Cook , Catalin Marinas , Mark Brown , Anshuman Khandual Subject: [PATCH v4 07/26] arm64: head: split off idmap creation code Date: Mon, 13 Jun 2022 16:45:31 +0200 Message-Id: <20220613144550.3760857-8-ardb@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220613144550.3760857-1-ardb@kernel.org> References: <20220613144550.3760857-1-ardb@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=5970; h=from:subject; bh=OhKluuvrPX/ZIKI6cSSrnjwjMiDdvqkJIcBzUOSbddk=; b=owEB7QES/pANAwAKAcNPIjmS2Y8kAcsmYgBip013BkB7RbgceET9//c1e3q1KM8XQiA2SuRu0Jut Lucg722JAbMEAAEKAB0WIQT72WJ8QGnJQhU3VynDTyI5ktmPJAUCYqdNdwAKCRDDTyI5ktmPJGctC/ 44lf4aX8pgQZFwviqJI43KozRnPQH7s3iwBbiHsw8pTquGElPc9lMeEeBhx3igXEf8YCyX/rAtj0II ACeitxinucMeH7NLGaOg08+7zrb2g1LYylLZuTtCPhZ/OwS+3EQXKokf3fS63SjORzeBva3cSJE4J/ 0sFOO4tJNx3ct61l+QHu/doTVHGvlHniG5PjbgkldMEl9Md2vxgQVpKeJNWyyoZtHA0PR4TwmsWv8D 6EsoGGPltihj4SD7kSXEV03CMnzS9w2QnFMmZKHQQjhaZj9NNuYFqdqUNYv2/J35RHGE11wioaO6Vc RlSmYTWGa9LHM42dQ2OuZ32UMU1SJbkqKBumh6179dNhhASESL+wuoah2oJHFKkNEljaDyHwu3HfYs Kgv13z6VU+pfBB/f+TMXuuPlKzSu5zBFi7ryXtExSyors5FDUMyVWyCkn0bDeGajX8SxV/fZsGwgPI P/HagQGRUPyF4lhvN7ekddofZR7Yls2QVl9viWs+Vq7iM= X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org Split off the creation of the ID map page tables, so that we can avoid running it again unnecessarily when KASLR is in effect (which only randomizes the virtual placement). This will permit us to drop some explicit cache maintenance to the PoC which was necessary because the cache invalidation being performed on some global variables might otherwise clobber unrelated variables that happen to share a cacheline. Signed-off-by: Ard Biesheuvel --- arch/arm64/kernel/head.S | 101 ++++++++++---------- 1 file changed, 52 insertions(+), 49 deletions(-) diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index eb54c0289c8a..1cbc52097bf9 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -84,7 +84,7 @@ * Register Scope Purpose * x21 primary_entry() .. start_kernel() FDT pointer passed at boot in x0 * x23 primary_entry() .. start_kernel() physical misalignment/KASLR offset - * x28 __create_page_tables() callee preserved temp register + * x28 clear_page_tables() callee preserved temp register * x19/x20 __primary_switch() callee preserved temp registers * x24 __primary_switch() .. relocate_kernel() current RELR displacement */ @@ -94,7 +94,10 @@ SYM_CODE_START(primary_entry) adrp x23, __PHYS_OFFSET and x23, x23, MIN_KIMG_ALIGN - 1 // KASLR offset, defaults to 0 bl set_cpu_boot_mode_flag - bl __create_page_tables + bl clear_page_tables + bl create_idmap + bl create_kernel_mapping + /* * The following calls CPU setup code, see arch/arm64/mm/proc.S for * details. @@ -122,6 +125,35 @@ SYM_CODE_START_LOCAL(preserve_boot_args) b dcache_inval_poc // tail call SYM_CODE_END(preserve_boot_args) +SYM_FUNC_START_LOCAL(clear_page_tables) + mov x28, lr + + /* + * Invalidate the init page tables to avoid potential dirty cache lines + * being evicted. Other page tables are allocated in rodata as part of + * the kernel image, and thus are clean to the PoC per the boot + * protocol. + */ + adrp x0, init_pg_dir + adrp x1, init_pg_end + bl dcache_inval_poc + + /* + * Clear the init page tables. + */ + adrp x0, init_pg_dir + adrp x1, init_pg_end + sub x1, x1, x0 +1: stp xzr, xzr, [x0], #16 + stp xzr, xzr, [x0], #16 + stp xzr, xzr, [x0], #16 + stp xzr, xzr, [x0], #16 + subs x1, x1, #64 + b.ne 1b + + ret x28 +SYM_FUNC_END(clear_page_tables) + /* * Macro to populate page table entries, these entries can be pointers to the next level * or last level entries pointing to physical memory. @@ -231,44 +263,8 @@ SYM_CODE_END(preserve_boot_args) populate_entries \tbl, \rtbl, \istart, \iend, \flags, #SWAPPER_BLOCK_SIZE, \tmp .endm -/* - * Setup the initial page tables. We only setup the barest amount which is - * required to get the kernel running. The following sections are required: - * - identity mapping to enable the MMU (low address, TTBR0) - * - first few MB of the kernel linear mapping to jump to once the MMU has - * been enabled - */ -SYM_FUNC_START_LOCAL(__create_page_tables) - mov x28, lr - /* - * Invalidate the init page tables to avoid potential dirty cache lines - * being evicted. Other page tables are allocated in rodata as part of - * the kernel image, and thus are clean to the PoC per the boot - * protocol. - */ - adrp x0, init_pg_dir - adrp x1, init_pg_end - bl dcache_inval_poc - - /* - * Clear the init page tables. - */ - adrp x0, init_pg_dir - adrp x1, init_pg_end - sub x1, x1, x0 -1: stp xzr, xzr, [x0], #16 - stp xzr, xzr, [x0], #16 - stp xzr, xzr, [x0], #16 - stp xzr, xzr, [x0], #16 - subs x1, x1, #64 - b.ne 1b - - mov x7, SWAPPER_MM_MMUFLAGS - - /* - * Create the identity mapping. - */ +SYM_FUNC_START_LOCAL(create_idmap) adrp x0, idmap_pg_dir adrp x3, __idmap_text_start // __pa(__idmap_text_start) @@ -319,12 +315,23 @@ SYM_FUNC_START_LOCAL(__create_page_tables) */ #endif adr_l x6, __idmap_text_end // __pa(__idmap_text_end) + mov x7, SWAPPER_MM_MMUFLAGS map_memory x0, x1, x3, x6, x7, x3, IDMAP_PGD_ORDER, x10, x11, x12, x13, x14, EXTRA_SHIFT /* - * Map the kernel image (starting with PHYS_OFFSET). + * Since the page tables have been populated with non-cacheable + * accesses (MMU disabled), invalidate those tables again to + * remove any speculatively loaded cache lines. */ + dmb sy + + adrp x0, idmap_pg_dir + adrp x1, idmap_pg_end + b dcache_inval_poc // tail call +SYM_FUNC_END(create_idmap) + +SYM_FUNC_START_LOCAL(create_kernel_mapping) adrp x0, init_pg_dir mov_q x5, KIMAGE_VADDR // compile time __va(_text) add x5, x5, x23 // add KASLR displacement @@ -332,6 +339,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables) adrp x3, _text // runtime __pa(_text) sub x6, x6, x3 // _end - _text add x6, x6, x5 // runtime __va(_end) + mov x7, SWAPPER_MM_MMUFLAGS map_memory x0, x1, x5, x6, x7, x3, (VA_BITS - PGDIR_SHIFT), x10, x11, x12, x13, x14 @@ -342,16 +350,10 @@ SYM_FUNC_START_LOCAL(__create_page_tables) */ dmb sy - adrp x0, idmap_pg_dir - adrp x1, idmap_pg_end - bl dcache_inval_poc - adrp x0, init_pg_dir adrp x1, init_pg_end - bl dcache_inval_poc - - ret x28 -SYM_FUNC_END(__create_page_tables) + b dcache_inval_poc // tail call +SYM_FUNC_END(create_kernel_mapping) /* * Initialize CPU registers with task-specific and cpu-specific context. @@ -836,7 +838,8 @@ SYM_FUNC_START_LOCAL(__primary_switch) pre_disable_mmu_workaround msr sctlr_el1, x20 // disable the MMU isb - bl __create_page_tables // recreate kernel mapping + bl clear_page_tables + bl create_kernel_mapping // Recreate kernel mapping tlbi vmalle1 // Remove any stale TLB entries dsb nsh