From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 3D6301A705D; Tue, 24 Sep 2024 11:28:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727177289; cv=none; b=FKozlS4O0ovsdlfhVF/5VhnPir3C9Xj03YF01NXlPFyktS1KZI2WJZmeJxzA2DQI7EwSo9P3WxHI2Q8jiFpiXxHTYscAdXrlXzGCyWQDmPUnWr4+gUd+aicqBbSKNY/7tpKKJo8DaZRvyMx6yCH9C+T1VfHIsi15xfZnTItZlYE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727177289; c=relaxed/simple; bh=w6ZtRnLtQAfgK8GE4fbEyNK/ud8SdGHKIdYvFa+frKs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=fwRZwaqUF8sdeDpoece5WdqtSDf1b0QG6jXbKoMzXMWkDcUFEGG1Qw9pzPepyEFhqN2OAOgI2fX2NFReg0pq0tQ/j+uaEiDZAAPfJvFXcxvBHL2F6fcGLGwOoHcG+jFDetiH/1pOXTKJxDUtRUA/53yXbOc74jNba3nRlTcXXAc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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