From patchwork Mon Jan 24 17:47:38 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ard Biesheuvel X-Patchwork-Id: 12722609 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 6D64CC43217 for ; Mon, 24 Jan 2022 17:49:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244237AbiAXRtZ (ORCPT ); Mon, 24 Jan 2022 12:49:25 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56600 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244427AbiAXRtX (ORCPT ); Mon, 24 Jan 2022 12:49:23 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 96CC9C06173B for ; Mon, 24 Jan 2022 09:49:22 -0800 (PST) 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 5C456B811AC for ; Mon, 24 Jan 2022 17:49:21 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 441EBC36AE2; Mon, 24 Jan 2022 17:49:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1643046560; bh=S9VAgvS7Dq3pQmUaE1sjfY4F28GrRzw4QsaVdM6p2cE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=smbyr4J+IEJmplCjnf5mh8XUWXi3I+59MepPE4oLOdy2pkLKTQgrLJQzj4xXTLHK4 ScBKty3+LceT/7B023UuEnsrMJ1f55/gDXKabQjKHvGEbkfYAyUkieUXDIPhTQsDw+ I+zzmezPaa/biK9pQWoQ/7ONfFVlNNWQYOi+qnwbKSf/Jkd3a7vCnslj432iBjO3sN 9agB5qoGZN8nPwngk8zZW5p0hvNqh+5nfen2z1Tg6dnYMzmGunkMDafzI50Y9LS4Sx 6ZM46ruvSat1Tb8lea/rOs0OZlusCO3ede3ByI9ABBMZzlhzWx8WuSTuQtjq6Pm8AC /slrOeLAo4YyA== From: Ard Biesheuvel To: linux@armlinux.org.uk, linux-arm-kernel@lists.infradead.org Cc: linux-hardening@vger.kernel.org, Ard Biesheuvel , Nicolas Pitre , Arnd Bergmann , Kees Cook , Keith Packard , Linus Walleij , Nick Desaulniers , Tony Lindgren , Marc Zyngier , Vladimir Murzin , Jesse Taube Subject: [PATCH v5 26/32] ARM: memmove: use frame pointer as unwind anchor Date: Mon, 24 Jan 2022 18:47:38 +0100 Message-Id: <20220124174744.1054712-27-ardb@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220124174744.1054712-1-ardb@kernel.org> References: <20220124174744.1054712-1-ardb@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=6060; h=from:subject; bh=S9VAgvS7Dq3pQmUaE1sjfY4F28GrRzw4QsaVdM6p2cE=; b=owEB7QES/pANAwAKAcNPIjmS2Y8kAcsmYgBh7uYz0OjoiDentb6t7pZtc080VYIAGPoHXehiwE+w IX4gUl6JAbMEAAEKAB0WIQT72WJ8QGnJQhU3VynDTyI5ktmPJAUCYe7mMwAKCRDDTyI5ktmPJBavDA CSrS7Cos4dYkj0uU4By5+ZpsWY+H6R4VS+UV6mUUUeLYfxdzcImuarmQTSV2aIagBKV7LhSEVDlH1p pYdEf6exNAtbDwUvt+0UxhzhXVbYkH9fOeG58RSDZev1cuk/pyGsL7bo54RXPb6X96NlYox/yOwg6N DcpZJAi/SsfamP1KZWT1VEVudzRxJ1dOz/cO6B+CfsINrTEpH11sSFqD/sTFb8ISP5j5JN2rIj+9j3 Q2HyEhexeQfuaCzZORwecK2fDOo3NyQmk3vWzUr9rXFB2UlbMjL5T7FPcS6cuDzqosEUbMLfuWQXT4 soCXjO8RAhc9f0/9nfpx2PaVarPXj8qBORobSsbsxdTh+sZ1ClZUwQEoAROcoYq4aPYtViZMSDJGhB 9xfiCvDpI0gp14QB6YcQpT564kNg6WSu4+49RwF/lWbhHzAIuN+XDRGHFwpmICMkJwjLidra/LORpw iotYP1PBsJET8JoErr+ZU7ksK5RrcNGlX3Clpqay8mYck= X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org The memmove routine is a bit unusual in the way it manages the stack pointer: depending on the execution path through the function, the SP assumes different values as different subsets of the register file are preserved and restored again. This is problematic when it comes to EHABI unwind info, as it is not instruction accurate, and does not allow tracking the SP value as it changes. Commit 207a6cb06990c ("ARM: 8224/1: Add unwinding support for memmove function") addressed this by carving up the function in different chunks as far as the unwinder is concerned, and keeping a set of unwind directives for each of them, each corresponding with the state of the stack pointer during execution of the chunk in question. This not only duplicates unwind info unnecessarily, but it also complicates unwinding the stack upon overflow. Instead, let's do what the compiler does when the SP is updated halfway through a function, which is to use a frame pointer and emit the appropriate unwind directives to communicate this to the unwinder. Note that Thumb-2 uses R7 for this, while ARM uses R11 aka FP. So let's avoid touching R7 in the body of the function, so that Thumb-2 can use it as the frame pointer. R11 was not modified in the first place. Signed-off-by: Ard Biesheuvel Tested-by: Keith Packard Tested-by: Marc Zyngier Tested-by: Vladimir Murzin # ARMv7M --- arch/arm/lib/memmove.S | 60 +++++++------------- 1 file changed, 20 insertions(+), 40 deletions(-) diff --git a/arch/arm/lib/memmove.S b/arch/arm/lib/memmove.S index 6fecc12a1f51..6410554039fd 100644 --- a/arch/arm/lib/memmove.S +++ b/arch/arm/lib/memmove.S @@ -31,12 +31,13 @@ WEAK(memmove) subs ip, r0, r1 cmphi r2, ip bls __memcpy - - stmfd sp!, {r0, r4, lr} UNWIND( .fnend ) UNWIND( .fnstart ) - UNWIND( .save {r0, r4, lr} ) @ in first stmfd block + UNWIND( .save {r0, r4, fpreg, lr} ) + stmfd sp!, {r0, r4, UNWIND(fpreg,) lr} + UNWIND( .setfp fpreg, sp ) + UNWIND( mov fpreg, sp ) add r1, r1, r2 add r0, r0, r2 subs r2, r2, #4 @@ -48,12 +49,7 @@ WEAK(memmove) bne 10f 1: subs r2, r2, #(28) - stmfd sp!, {r5 - r8} - UNWIND( .fnend ) - - UNWIND( .fnstart ) - UNWIND( .save {r0, r4, lr} ) - UNWIND( .save {r5 - r8} ) @ in second stmfd block + stmfd sp!, {r5, r6, r8, r9} blt 5f CALGN( ands ip, r0, #31 ) @@ -72,9 +68,9 @@ WEAK(memmove) PLD( pld [r1, #-96] ) 3: PLD( pld [r1, #-128] ) -4: ldmdb r1!, {r3, r4, r5, r6, r7, r8, ip, lr} +4: ldmdb r1!, {r3, r4, r5, r6, r8, r9, ip, lr} subs r2, r2, #32 - stmdb r0!, {r3, r4, r5, r6, r7, r8, ip, lr} + stmdb r0!, {r3, r4, r5, r6, r8, r9, ip, lr} bge 3b PLD( cmn r2, #96 ) PLD( bge 4b ) @@ -88,8 +84,8 @@ WEAK(memmove) W(ldr) r4, [r1, #-4]! W(ldr) r5, [r1, #-4]! W(ldr) r6, [r1, #-4]! - W(ldr) r7, [r1, #-4]! W(ldr) r8, [r1, #-4]! + W(ldr) r9, [r1, #-4]! W(ldr) lr, [r1, #-4]! add pc, pc, ip @@ -99,17 +95,13 @@ WEAK(memmove) W(str) r4, [r0, #-4]! W(str) r5, [r0, #-4]! W(str) r6, [r0, #-4]! - W(str) r7, [r0, #-4]! W(str) r8, [r0, #-4]! + W(str) r9, [r0, #-4]! W(str) lr, [r0, #-4]! CALGN( bcs 2b ) -7: ldmfd sp!, {r5 - r8} - UNWIND( .fnend ) @ end of second stmfd block - - UNWIND( .fnstart ) - UNWIND( .save {r0, r4, lr} ) @ still in first stmfd block +7: ldmfd sp!, {r5, r6, r8, r9} 8: movs r2, r2, lsl #31 ldrbne r3, [r1, #-1]! @@ -118,7 +110,7 @@ WEAK(memmove) strbne r3, [r0, #-1]! strbcs r4, [r0, #-1]! strbcs ip, [r0, #-1] - ldmfd sp!, {r0, r4, pc} + ldmfd sp!, {r0, r4, UNWIND(fpreg,) pc} 9: cmp ip, #2 ldrbgt r3, [r1, #-1]! @@ -137,13 +129,10 @@ WEAK(memmove) ldr r3, [r1, #0] beq 17f blt 18f - UNWIND( .fnend ) .macro backward_copy_shift push pull - UNWIND( .fnstart ) - UNWIND( .save {r0, r4, lr} ) @ still in first stmfd block subs r2, r2, #28 blt 14f @@ -152,12 +141,7 @@ WEAK(memmove) CALGN( subcc r2, r2, ip ) CALGN( bcc 15f ) -11: stmfd sp!, {r5 - r9} - UNWIND( .fnend ) - - UNWIND( .fnstart ) - UNWIND( .save {r0, r4, lr} ) - UNWIND( .save {r5 - r9} ) @ in new second stmfd block +11: stmfd sp!, {r5, r6, r8 - r10} PLD( pld [r1, #-4] ) PLD( subs r2, r2, #96 ) @@ -167,35 +151,31 @@ WEAK(memmove) PLD( pld [r1, #-96] ) 12: PLD( pld [r1, #-128] ) -13: ldmdb r1!, {r7, r8, r9, ip} +13: ldmdb r1!, {r8, r9, r10, ip} mov lr, r3, lspush #\push subs r2, r2, #32 ldmdb r1!, {r3, r4, r5, r6} orr lr, lr, ip, lspull #\pull mov ip, ip, lspush #\push - orr ip, ip, r9, lspull #\pull + orr ip, ip, r10, lspull #\pull + mov r10, r10, lspush #\push + orr r10, r10, r9, lspull #\pull mov r9, r9, lspush #\push orr r9, r9, r8, lspull #\pull mov r8, r8, lspush #\push - orr r8, r8, r7, lspull #\pull - mov r7, r7, lspush #\push - orr r7, r7, r6, lspull #\pull + orr r8, r8, r6, lspull #\pull mov r6, r6, lspush #\push orr r6, r6, r5, lspull #\pull mov r5, r5, lspush #\push orr r5, r5, r4, lspull #\pull mov r4, r4, lspush #\push orr r4, r4, r3, lspull #\pull - stmdb r0!, {r4 - r9, ip, lr} + stmdb r0!, {r4 - r6, r8 - r10, ip, lr} bge 12b PLD( cmn r2, #96 ) PLD( bge 13b ) - ldmfd sp!, {r5 - r9} - UNWIND( .fnend ) @ end of the second stmfd block - - UNWIND( .fnstart ) - UNWIND( .save {r0, r4, lr} ) @ still in first stmfd block + ldmfd sp!, {r5, r6, r8 - r10} 14: ands ip, r2, #28 beq 16f @@ -211,7 +191,6 @@ WEAK(memmove) 16: add r1, r1, #(\pull / 8) b 8b - UNWIND( .fnend ) .endm @@ -222,5 +201,6 @@ WEAK(memmove) 18: backward_copy_shift push=24 pull=8 + UNWIND( .fnend ) ENDPROC(memmove) ENDPROC(__memmove)