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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2C72EC5518F for ; Tue, 4 Aug 2026 17:05:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id: Content-Transfer-Encoding:MIME-Version:References:In-Reply-To:Message-Id:Date :Subject:To:From:Reply-To:Content-Type:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=jOJrFyZ5QAJ1G1jhx0f7R9JTBI5OBq+7Zhiui72HjXY=; b=HpTJqzfVRsymTi 7Fw4IzoirEcflflZ/USsOYtywrwKgIprbUtt78XwBV8qfCWsTbTbguzUMophiy671RzMIxuVzS2t3 ynSyuQoIfeoJn5pYwvQ3/zVOsr0W9toglTTWIc6itRM0eWSLytBrqnIimi7F4B1WJdiLzt1Zhj/aI DWm6QB+7dpsV8FgyY7y8GL94rG1eva3jDSE2B7irNaj5TCQbEpZuG98DzDR+TSogHquy9gbxMATvU rS3dqAjiYOXJL8JSowecee/j0MnG/HsA6EqN5lX4FVKgKQxXStxEH3hQxyHAfy0VvBZPrUpzdHozC PeL90znMRuJEVl0GUVyw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wrIZw-00000002PlW-1qRQ; Tue, 04 Aug 2026 17:05:24 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wrIZt-00000002PkY-0Bzr for linux-arm-kernel@lists.infradead.org; Tue, 04 Aug 2026 17:05:22 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 533831684; Tue, 4 Aug 2026 10:05:16 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id CFE643F632; Tue, 4 Aug 2026 10:05:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1785863120; bh=WVzy+CFQzZ9ki8AaGr2tZyokJVK18eIfmnCV3Kgx2R0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sGehTrTUwMenQPYItLGFO9Vpv7W1HiuDEAatv/sjFrxlAx3wLHPoXTh4GY2NfFKSX BlUKhI5zrxRUz8aSlfnPPqzQRtlKyDECCx4QSn3HAsKzijYJm5luPkrCPgChQH/8O5 o59yg178gbY80vIMcCK8WHGJbvw61cewmODJs6EQ= From: Mark Rutland To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v2 01/20] arm64: percpu: Fix this_cpu_write() casting Date: Tue, 4 Aug 2026 18:04:44 +0100 Message-Id: <20260804170503.3513916-2-mark.rutland@arm.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20260804170503.3513916-1-mark.rutland@arm.com> References: <20260804170503.3513916-1-mark.rutland@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260804_100521_197779_CE31E8BF X-CRM114-Status: GOOD ( 12.18 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, vladimir.murzin@arm.com, ryan.roberts@arm.com, peterz@infradead.org, catalin.marinas@arm.com, david.laight.linux@gmail.com, stable@vger.kernel.org, ruanjinjie@huawei.com, james.morse@arm.com, yang@os.amperecomputing.com, cl@gentwo.org, maz@kernel.org, david@kernel.org, ljs@kernel.org, will@kernel.org, ardb@kernel.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org The arm64 implementation of this_cpu_write() casts 'val' to unsigned long. This is necessary to handle cases where 'val' is a pointer type, and to avoid spurious compiler warnings for the (unreachable!) cases where the pointer type would be cast to a smaller integer type. Unfortunately, the cast is applied to 'val' rather than '(val)', which won't always generate the expected value when 'val' is an expression. For example, for this_cpu_write(pcp, zero - 1), where 'pcp' is a u64 and 'zero' is a u32: * 'zero' ===> (u32) 0x00000000 * 'zero - 1' ===> (u32) 0xffffffff * '(unsigned long)zero - 1' ===> (u64) 0xffffffffffffffff * '(unsigned long)(zero - 1)' ===> (u64) 0x00000000ffffffff Fix this by adding brackets around 'val' The bug described above can be seen from the disassembly of the following test code: | void this_cpu_write_zero_minus_1(u64 __percpu *pcp) | { | u32 zero = 0; | this_cpu_write(*pcp, zero - 1); | } | | void this_cpu_write_zero_minus_1_brackets(u64 __percpu *pcp) | { | u32 zero = 0; | this_cpu_write(*pcp, (zero - 1)); | } Generated code before this patch: | : | paciasp | stp x29, x30, [sp, #-16]! | mrs x1, sp_el0 | mov x29, sp | ldr w2, [x1, #8] | add w2, w2, #0x1 | str w2, [x1, #8] | mov x3, #0xffffffffffffffff | mrs x2, tpidr_el1 | str x3, [x0, x2] | ldr x0, [x1, #8] | add x0, x0, x3 | str w0, [x1, #8] | cbz x0, 1f | ldr x0, [x1, #8] | cbnz x0, 2f | 1: bl preempt_schedule_notrace | 2: ldp x29, x30, [sp], #16 | autiasp | ret | | : | paciasp | stp x29, x30, [sp, #-16]! | mrs x1, sp_el0 | mov x29, sp | ldr w2, [x1, #8] | add w2, w2, #0x1 | str w2, [x1, #8] | mov x3, #0xffffffff | mrs x2, tpidr_el1 | str x3, [x0, x2] | ldr x0, [x1, #8] | sub x0, x0, #0x1 | str w0, [x1, #8] | cbz x0, 1f | ldr x0, [x1, #8] | cbnz x0, 2f | 1: bl preempt_schedule_notrace | 2: ldp x29, x30, [sp], #16 | autiasp | ret Generated code after this patch: | : | paciasp | stp x29, x30, [sp, #-16]! | mrs x1, sp_el0 | mov x29, sp | ldr w2, [x1, #8] | add w2, w2, #0x1 | str w2, [x1, #8] | mov x3, #0xffffffff | mrs x2, tpidr_el1 | str x3, [x0, x2] | ldr x0, [x1, #8] | sub x0, x0, #0x1 | str w0, [x1, #8] | cbz x0, 1f | ldr x0, [x1, #8] | cbnz x0, 2f | 1: bl preempt_schedule_notrace | 2: ldp x29, x30, [sp], #16 | autiasp | ret | | : | b this_cpu_write_zero_minus_1 Fixes: 959bf2fd03b5 ("arm64: percpu: Rewrite per-cpu ops to allow use of LSE atomics") Reported-by: David Laight Signed-off-by: Mark Rutland Cc: Ada Couprie Diaz Cc: Ard Biesheuvel Cc: Catalin Marinas Cc: James Morse Cc: Jinjie Ruan Cc: Marc Zyngier Cc: Peter Zijlstra Cc: Vladimir Murzin Cc: Will Deacon Cc: Yang Shi Cc: stable@vger.kernel.org --- arch/arm64/include/asm/percpu.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/arm64/include/asm/percpu.h b/arch/arm64/include/asm/percpu.h index b57b2bb009677..63bbfd4944a37 100644 --- a/arch/arm64/include/asm/percpu.h +++ b/arch/arm64/include/asm/percpu.h @@ -179,13 +179,13 @@ PERCPU_RET_OP(add, add, ldadd) _pcp_protect_return(__percpu_read_64, pcp) #define this_cpu_write_1(pcp, val) \ - _pcp_protect(__percpu_write_8, pcp, (unsigned long)val) + _pcp_protect(__percpu_write_8, pcp, (unsigned long)(val)) #define this_cpu_write_2(pcp, val) \ - _pcp_protect(__percpu_write_16, pcp, (unsigned long)val) + _pcp_protect(__percpu_write_16, pcp, (unsigned long)(val)) #define this_cpu_write_4(pcp, val) \ - _pcp_protect(__percpu_write_32, pcp, (unsigned long)val) + _pcp_protect(__percpu_write_32, pcp, (unsigned long)(val)) #define this_cpu_write_8(pcp, val) \ - _pcp_protect(__percpu_write_64, pcp, (unsigned long)val) + _pcp_protect(__percpu_write_64, pcp, (unsigned long)(val)) #define this_cpu_add_1(pcp, val) \ _pcp_protect(__percpu_add_case_8, pcp, val) -- 2.30.2