From nobody Fri Feb 13 09:48:17 2026 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 85131E7E644 for ; Tue, 26 Sep 2023 16:09:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235122AbjIZQJV (ORCPT ); Tue, 26 Sep 2023 12:09:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33682 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231300AbjIZQJU (ORCPT ); Tue, 26 Sep 2023 12:09:20 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9FF6F95 for ; Tue, 26 Sep 2023 09:09:13 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 04F55C433C7; Tue, 26 Sep 2023 16:09:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1695744553; bh=KIbC1Ui2Ufy2ZZPQgUs1RBN/CWpdIljaKe9AGeuEHZU=; h=From:To:Cc:Subject:Date:From; b=nGT4zamObMbcyTm3cidGJPErWADcslA/S4HeodBErtmexNAHIo1FGdXIQbP1ZafTo dkUvTtPBLsSVezV3W4gOd73sZ9woyU0lEjWIZh0ZaLtSymgRZeQfa1mRx653HJgFKq eaDRjYsSRzOepbxCElSDxojz99v30Rz/xPk6rQhsEFeyqFNwF20T2VEZhOqF7H+eo+ RC4oNgF4oB94j3Ade3j9wHiRz2Z/XDOnE6tA4FY2WUshPSEgwUWJofrE+FFuOFp86P Xm9UPJxXmiPdScr6z9pi9FML9rp0XgDJhSNGCx9Oc8H0zNLjX+d19P3D53EZFYK9Tj 5lW5WrmgKUoiQ== From: Masahiro Yamada To: patches@armlinux.org.uk Cc: linux-kernel@vger.kernel.org, Russell King , Masahiro Yamada , Ard Biesheuvel , linux-arm-kernel@lists.infradead.org Subject: [PATCH] ARM: fix get_user() broken with veneer Date: Wed, 27 Sep 2023 01:09:03 +0900 Message-Id: <20230926160903.62924-1-masahiroy@kernel.org> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The 32-bit ARM kernel stops working if the kernel grows to the point where veneers for __get_user_* are created. AAPCS32 [1] states, "Register r12 (IP) may be used by a linker as a scratch register between a routine and any subroutine it calls. It can also be used within a routine to hold intermediate values between subroutine calls." However, bl instructions buried within the inline asm are unpredictable for compilers; hence, "ip" must be added to the clobber list. This becomes critical when veneers for __get_user_* are created because veneers use the ip register since commit 02e541db0540 ("ARM: 8323/1: force linker to use PIC veneers"). [1]: https://github.com/ARM-software/abi-aa/blob/2023Q1/aapcs32/aapcs32.rst Signed-off-by: Masahiro Yamada Reviewed-by: Ard Biesheuvel --- KernelVersion: v6.6-rc1 arch/arm/include/asm/uaccess.h | 14 ++------------ 1 file changed, 2 insertions(+), 12 deletions(-) diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h index bb5c81823117..c28f5ec21e41 100644 --- a/arch/arm/include/asm/uaccess.h +++ b/arch/arm/include/asm/uaccess.h @@ -109,16 +109,6 @@ extern int __get_user_64t_1(void *); extern int __get_user_64t_2(void *); extern int __get_user_64t_4(void *); =20 -#define __GUP_CLOBBER_1 "lr", "cc" -#ifdef CONFIG_CPU_USE_DOMAINS -#define __GUP_CLOBBER_2 "ip", "lr", "cc" -#else -#define __GUP_CLOBBER_2 "lr", "cc" -#endif -#define __GUP_CLOBBER_4 "lr", "cc" -#define __GUP_CLOBBER_32t_8 "lr", "cc" -#define __GUP_CLOBBER_8 "lr", "cc" - #define __get_user_x(__r2, __p, __e, __l, __s) \ __asm__ __volatile__ ( \ __asmeq("%0", "r0") __asmeq("%1", "r2") \ @@ -126,7 +116,7 @@ extern int __get_user_64t_4(void *); "bl __get_user_" #__s \ : "=3D&r" (__e), "=3Dr" (__r2) \ : "0" (__p), "r" (__l) \ - : __GUP_CLOBBER_##__s) + : "ip", "lr", "cc") =20 /* narrowing a double-word get into a single 32bit word register: */ #ifdef __ARMEB__ @@ -148,7 +138,7 @@ extern int __get_user_64t_4(void *); "bl __get_user_64t_" #__s \ : "=3D&r" (__e), "=3Dr" (__r2) \ : "0" (__p), "r" (__l) \ - : __GUP_CLOBBER_##__s) + : "ip", "lr", "cc") #else #define __get_user_x_64t __get_user_x #endif --=20 2.39.2