From patchwork Mon Jun 13 14:45:47 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ard Biesheuvel X-Patchwork-Id: 12879898 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 5078BCCA47B for ; Mon, 13 Jun 2022 18:31:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245667AbiFMSbC (ORCPT ); Mon, 13 Jun 2022 14:31:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53248 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245506AbiFMSat (ORCPT ); Mon, 13 Jun 2022 14:30:49 -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 2838BB7DCF for ; Mon, 13 Jun 2022 07:47:03 -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 B3D54B8105C for ; Mon, 13 Jun 2022 14:47:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7D8FCC341C4; Mon, 13 Jun 2022 14:46:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1655131620; bh=39z4H7gQhk37tMuzT7u3jfPc/a1t6NKvtH23Ke11dSg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=slPGkU0PFtZFL2JNNsFuUVU4wQ7guIYoXHJL4zX9LmBDx/QlkLySG4g8nq4ryG/Qb rpUbpUpmJhB1f9GbvL++IhBnVRRXJGeg+7nAkl1EeSWp1qfluS6R4v1RqvggIqbtw5 RxLsppORwuqvjfSvAXuDs7ScRFGumDIYtvixH6yGnqQcQxd8364wvwRcJhm9CmKkKV 2rCYEFNxO3xku+jAqWML+iG+SujlbF6R3DpyGYzvF5n7i9eOMJlGeyqteYuNW1D4du 2akW42Qbab1U/JevHoJxYb8kNgCYBDe0Q6z2Zx5WT3Ua6FAI33hGvpv/QaBXHLefcR jtd5qAd3vxGTg== 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 23/26] arm64: head: remap the kernel text/inittext region read-only Date: Mon, 13 Jun 2022 16:45:47 +0200 Message-Id: <20220613144550.3760857-24-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=5386; h=from:subject; bh=39z4H7gQhk37tMuzT7u3jfPc/a1t6NKvtH23Ke11dSg=; b=owEB7QES/pANAwAKAcNPIjmS2Y8kAcsmYgBip02YimbsU6+W6N3oes89CwxS3smL+xwynIaGeLP9 rtpbfaWJAbMEAAEKAB0WIQT72WJ8QGnJQhU3VynDTyI5ktmPJAUCYqdNmAAKCRDDTyI5ktmPJF5rDA CRhzzdUfxHEaLOJ+f/oakVY8sASHL8n7d8oqI56o7iaIHsFa6wS4AXfLXHUGeDYzFQvfLGXj9k5Wvf BzQRFKXB0HIUVV4QhHhs6MrHIv2fJXWJzmztrC0vvPRQQiHJA7TaAALz1NeMtErvGAMrCSLodDzrTO BZZat/MqQEOkNKDfeVkGbLrm35NQUaWVRjY5kga0t9EPtGo3BhnFVL7gHifl5bR1ka25h3VqXmL/Pp OeoLqJb7wBndScEY7wkB+wJ4h+cebitUELcnCrDf82t8/WqeStiJGUArtaXhegd7hISQmm7ZieYxAm l1e2CBrblYUSSmgwhOVb9AH/faBjPzigFYiWlXTqJkcZBdgorro0b6NMT4dqwFKVovFFB5thfP3YGK Z3rx4Zzg6IOhOXZMprLlZrh+TEodLUzkiYqVovrNsV8b4FMlcLliGhoMMrLLIvoqnWPiVTg9WgHa0C 38Cbs7zPVSXwOOOi/9M9F/z72msZo6KebMbQDxtH5IZ7s= X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org In order to be able to run with WXN from boot (which could potentially be under a hypervisor regime that mandates this), update the temporary kernel page tables with read-only attributes for the text regions before attempting to execute from them. This is rather straight-forward for 16k and 64k granule configurations, as the split between executable and writable regions is guaranteed to be aligned to the granule used for the early kernel page tables. For 4k, it involves installing a single table entry and populating it accordingly. Signed-off-by: Ard Biesheuvel Reviewed-by: Kees Cook --- arch/arm64/include/asm/assembler.h | 8 +++ arch/arm64/kernel/head.S | 73 ++++++++++++++++++-- arch/arm64/kernel/vmlinux.lds.S | 2 +- arch/arm64/mm/proc.S | 11 --- 4 files changed, 78 insertions(+), 16 deletions(-) diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h index b2584709c332..e1e652410d7d 100644 --- a/arch/arm64/include/asm/assembler.h +++ b/arch/arm64/include/asm/assembler.h @@ -507,6 +507,14 @@ alternative_endif load_ttbr1 \page_table, \tmp, \tmp2 .endm + .macro __idmap_cpu_set_reserved_ttbr1, tmp1, tmp2 + adrp \tmp1, reserved_pg_dir + load_ttbr1 \tmp1, \tmp1, \tmp2 + tlbi vmalle1 + dsb nsh + isb + .endm + /* * reset_pmuserenr_el0 - reset PMUSERENR_EL0 if PMUv3 present */ diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 6bf685f988f1..92cbad41eed8 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -87,7 +87,7 @@ * x22 create_idmap() .. start_kernel() ID map VA of the DT blob * x23 primary_entry() .. start_kernel() physical misalignment/KASLR offset * x24 __primary_switch() linear map KASLR seed - * x28 create_idmap() callee preserved temp register + * x28 create_idmap(), remap_kernel_text() callee preserved temp register */ SYM_CODE_START(primary_entry) bl preserve_boot_args @@ -380,6 +380,66 @@ SYM_FUNC_START_LOCAL(create_kernel_mapping) ret SYM_FUNC_END(create_kernel_mapping) +SYM_FUNC_START_LOCAL(remap_kernel_text) + mov x28, lr + + ldr_l x1, kimage_vaddr + mov x2, x1 + ldr_l x3, .Linitdata_begin + adrp x4, _text + bic x4, x4, #SWAPPER_BLOCK_SIZE - 1 + mov x5, SWAPPER_RX_MMUFLAGS + mov x6, #SWAPPER_BLOCK_SHIFT + bl remap_region + +#if SWAPPER_BLOCK_SHIFT > PAGE_SHIFT + /* + * If the boundary between inittext and initdata happens to be aligned + * sufficiently, we are done here. Otherwise, we have to replace its block + * entry with a table entry, and populate the lower level table accordingly. + */ + ldr_l x3, .Linitdata_begin + tst x3, #SWAPPER_BLOCK_SIZE - 1 + b.eq 0f + + /* First, create a table mapping to replace the block mapping */ + ldr_l x1, kimage_vaddr + bic x2, x3, #SWAPPER_BLOCK_SIZE - 1 + adrp x4, init_pg_end - PAGE_SIZE + mov x5, #PMD_TYPE_TABLE + mov x6, #SWAPPER_BLOCK_SHIFT + bl remap_region + + /* Apply executable permissions to the first subregion */ + adrp x0, init_pg_end - PAGE_SIZE + ldr_l x3, .Linitdata_begin + bic x1, x3, #SWAPPER_BLOCK_SIZE - 1 + mov x2, x1 + adrp x4, __initdata_begin + bic x4, x4, #SWAPPER_BLOCK_SIZE - 1 + mov x5, SWAPPER_RX_MMUFLAGS | PTE_TYPE_PAGE + mov x6, #PAGE_SHIFT + bl remap_region + + /* Apply writable permissions to the second subregion */ + ldr_l x2, .Linitdata_begin + bic x1, x2, #SWAPPER_BLOCK_SIZE - 1 + add x3, x1, #SWAPPER_BLOCK_SIZE + adrp x4, __initdata_begin + mov x5, SWAPPER_RW_MMUFLAGS | PTE_TYPE_PAGE + mov x6, #PAGE_SHIFT + bl remap_region +#endif +0: dsb ishst + ret x28 +SYM_FUNC_END(remap_kernel_text) + + __INITDATA + .align 3 +.Linitdata_begin: + .quad __initdata_begin + .previous + /* * Initialize CPU registers with task-specific and cpu-specific context. * @@ -808,12 +868,17 @@ SYM_FUNC_START_LOCAL(__primary_switch) #endif bl clear_page_tables bl create_kernel_mapping - +#ifdef CONFIG_RELOCATABLE adrp x1, init_pg_dir load_ttbr1 x1, x1, x2 -#ifdef CONFIG_RELOCATABLE - bl __relocate_kernel + bl __relocate_kernel // preserves x0 + + __idmap_cpu_set_reserved_ttbr1 x1, x2 #endif + bl remap_kernel_text + adrp x1, init_pg_dir + load_ttbr1 x1, x1, x2 + ldr x8, =__primary_switched adrp x0, __PHYS_OFFSET br x8 diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 736aca63dad1..3830c6c66e46 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -310,7 +310,7 @@ SECTIONS . = ALIGN(PAGE_SIZE); init_pg_dir = .; - . += INIT_DIR_SIZE; + . += INIT_DIR_SIZE + PAGE_SIZE; init_pg_end = .; . = ALIGN(SEGMENT_ALIGN); diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S index 493b8ffc9be5..c237e976b138 100644 --- a/arch/arm64/mm/proc.S +++ b/arch/arm64/mm/proc.S @@ -168,17 +168,6 @@ SYM_FUNC_END(cpu_do_resume) .pushsection ".idmap.text", "awx" -.macro __idmap_cpu_set_reserved_ttbr1, tmp1, tmp2 - adrp \tmp1, reserved_pg_dir - phys_to_ttbr \tmp2, \tmp1 - offset_ttbr1 \tmp2, \tmp1 - msr ttbr1_el1, \tmp2 - isb - tlbi vmalle1 - dsb nsh - isb -.endm - /* * void idmap_cpu_replace_ttbr1(phys_addr_t ttbr1) *