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 7B4E1CF9C6B for ; Tue, 24 Sep 2024 11:30:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Ng/ShEdaF4U+7lZmzaK6jJFWkWXLGdUo2c/kKpuw1es=; b=QmmE+4d2dS65x3N4xHLo6wai0H Fc/ZAXxGQKiE+KNo+TLJ0xbgupm9ZSWeOfEqgQMwXeOBR0aBujOgDyBfjLbXWsPmtuGxFCtwf7Q5n WpUs+4PY2qRBH3VQFd7VCcpEyRx5EDuKqNOfEOtotRHbz7GU8k96UxQaWty2nFid+v/0szy1jZTx4 Oibh+yylz0JXH0QSLnHgbLHGAQynm8vex6lfKzpLhj7QSFtgm/i85kEVn5RKh9Zm47d+8C9Aq0yF9 uegKEsjOJP2yLF1pjOBOS21mMRkM5xA0znOO91LAAUBwrgizcc5DPSvjYcREFmaG5deYhWQxQic/u ol4l8oHQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1st3kO-000000029ST-1c04; Tue, 24 Sep 2024 11:30:24 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1st3iC-000000028c8-2J0T for linux-arm-kernel@lists.infradead.org; Tue, 24 Sep 2024 11:28:10 +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 EADECDA7; Tue, 24 Sep 2024 04:28:34 -0700 (PDT) Received: from [10.57.76.149] (unknown [10.57.76.149]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 452493F528; Tue, 24 Sep 2024 04:28:00 -0700 (PDT) Message-ID: <47e1537f-5b60-4541-aed1-a20e804c137d@arm.com> Date: Tue, 24 Sep 2024 13:27:58 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 19/30] arm64: add POE signal support To: Joey Gouly , linux-arm-kernel@lists.infradead.org Cc: nd@arm.com, akpm@linux-foundation.org, aneesh.kumar@kernel.org, aneesh.kumar@linux.ibm.com, anshuman.khandual@arm.com, bp@alien8.de, broonie@kernel.org, catalin.marinas@arm.com, christophe.leroy@csgroup.eu, dave.hansen@linux.intel.com, hpa@zytor.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, maz@kernel.org, mingo@redhat.com, mpe@ellerman.id.au, naveen.n.rao@linux.ibm.com, npiggin@gmail.com, oliver.upton@linux.dev, shuah@kernel.org, skhan@linuxfoundation.org, szabolcs.nagy@arm.com, tglx@linutronix.de, will@kernel.org, x86@kernel.org, kvmarm@lists.linux.dev, linux-kselftest@vger.kernel.org References: <20240822151113.1479789-1-joey.gouly@arm.com> <20240822151113.1479789-20-joey.gouly@arm.com> Content-Language: en-GB From: Kevin Brodsky In-Reply-To: <20240822151113.1479789-20-joey.gouly@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240924_042808_668619_4623B539 X-CRM114-Status: GOOD ( 11.05 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 22/08/2024 17:11, Joey Gouly wrote: > @@ -1178,6 +1237,9 @@ static void setup_return(struct pt_regs *regs, struct k_sigaction *ka, > sme_smstop(); > } > > + if (system_supports_poe()) > + write_sysreg_s(POR_EL0_INIT, SYS_POR_EL0); At the point where setup_return() is called, the signal frame has already been written to the user stack. In other words, we write to the user stack first, and then reset POR_EL0. This may be problematic, especially if we are using the alternate signal stack, which the interrupted POR_EL0 may not grant access to. In that situation uaccess will fail and we'll end up with a SIGSEGV. This issue has already been discussed on the x86 side, and as it happens patches to reset PKRU early [1] have just landed. I don't think this is a blocker for getting this series landed, but we should try and align with x86. If there's no objection, I'm planning to work on a counterpart to the x86 series (resetting POR_EL0 early during signal delivery). Kevin [1] https://lore.kernel.org/lkml/20240802061318.2140081-2-aruna.ramakrishna@oracle.com/ > + > if (ka->sa.sa_flags & SA_RESTORER) > sigtramp = ka->sa.sa_restorer; > else