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 652DF2D836D; Fri, 24 Apr 2026 09:24:39 +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=1777022681; cv=none; b=jUxNQgmeMqSGCz2G0adIKZLVZVv/MKI8vX6PSRGcLa+B3kKoTg8G36AP7yIrjPErk9uI99G5JpE3tOYNr03xSLuQgJ9kFh6pdsSVNenIv+ADQmlx8Rd7fLagUfp0VfMIGDwerr7uU43UN8ZlFvpMamB1IlTOmCSNN2JZId6V3kI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777022681; c=relaxed/simple; bh=LgeQDUtw5awG1hk00vwUt2oakv15VSwrc2cQLxVardQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=WkJwlqa7cSw03TPg/q9pI+N3l6Ynu0TYJN3wuoM/aH/wldpEu3JI9ADlnK0AvlCIJ3OnjhZwdcyDRyEn2pxQrsINynQINz2Qxutbp/rtJPlUN3hdpEwxbg8aLxUpc58v07z180M3XbWiV2fbWZXTibjYijVsPEg1B7Un36I7K+E= 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; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=ARqDpBz1; 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 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="ARqDpBz1" 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 4CBA71BC0; Fri, 24 Apr 2026 02:24:33 -0700 (PDT) Received: from [10.57.33.60] (unknown [10.57.33.60]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BAC9A3F23F; Fri, 24 Apr 2026 02:24:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1777022678; bh=LgeQDUtw5awG1hk00vwUt2oakv15VSwrc2cQLxVardQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=ARqDpBz19IP4LhyYurQOBbnl/oFWHTP3i3w96mTQP4+iHySWxpjUVbEtmU5mAnW+a NtOc2fZwKBBw12rkf6PTRut/K/TelXRELxijnfSxntb91AFbzyTu6Hv1aTP3UxkcTe 6ELkNwtRQSUBIbnLUu1BloTzsnFb5QK+6nfATO0I= Message-ID: Date: Fri, 24 Apr 2026 11:24:33 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/4] arm64: signal: Preserve POR_EL0 if poe_context is missing To: Will Deacon Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Catalin Marinas , Joey Gouly , Mark Brown , Shuah Khan , linux-kselftest@vger.kernel.org References: <20260421144252.1440365-1-kevin.brodsky@arm.com> <20260421144252.1440365-2-kevin.brodsky@arm.com> <693f4d7c-46f4-409b-8944-a8c9e4b5e073@arm.com> From: Kevin Brodsky Content-Language: en-GB In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 23/04/2026 14:41, Will Deacon wrote: > On Wed, Apr 22, 2026 at 04:55:05PM +0200, Kevin Brodsky wrote: >> On 22/04/2026 14:19, Will Deacon wrote: >>>> @@ -74,8 +76,12 @@ struct rt_sigframe_user_layout { >>>> * This state needs to be carefully managed to ensure that it doesn't cause >>>> * uaccess to fail when setting up the signal frame, and the signal handler >>>> * itself also expects a well-defined state when entered. >>>> + * >>>> + * The valid_fields member is a bitfield (see UA_STATE_HAS_*), specifying which >>>> + * of the remaining fields is valid (has been set to a value). >>>> */ >>>> struct user_access_state { >>>> + unsigned int valid_fields; >>>> u64 por_el0; >>>> }; >>> Do you think it would be worth adding some accessors to make it easier >>> to keep the flags in sync? For example: >>> >>> /* Stores por_el0 into uas->por_el0 and sets UA_STATE_HAS_POR_EL0 */ >>> void set_ua_state_por_el0(struct user_access_state *uas, u64 por_el0); >>> >>> /* >>> * If UA_STATE_HAS_POR_EL0, *por_el0 = uas->por_el0 and return 0. >>> * Otherwise, return -ENOENT. >>> */ >>> int get_ua_state_por_el0(struct user_access_state *uas, u64 *por_el0); >>> >>> WDYT? >> I did get a feeling having helpers would be a good idea. I wonder if >> getters/setters aren't a bit overkill though, as they make accesses to >> the struct more cumbersome and we'd need a pair for every member (unless >> we use some macro magic). > We only have one struct member, so it's probably fine for now, and we > could group related members together in sub-structures to help in future. > But it's up to you -- I don't feel strongly about it, but requiring the > caller to update the flag manually is going to be a bug magnet. > >> Maybe it would be sufficient to have say >> ua_state_has_field(POR_EL0) to check if the bit is set, and >> ua_state_set_field_valid(POR_EL0) to set the bit? > I don't think that really helps with my concern. I'd like to avoid callers > having to remember to deal with the flags when they update the data. Got it. I can't think of a better way to do this so I'll just go ahead with your suggestion, and prefix all members of the struct with __ to make it clear they shouldn't be accessed directly. The macro magic can wait until we have more than one struct member ;) I've also reconsidered setup_sigframe() and realised using valid_fields there is not a great idea, because the record is allocated in setup_sigframe_layout() based on system_supports_poe(), and leaving a record uninitialised would be bad™. I'll remove that change and I'll have preserve_poe_context() fail with a WARN_ON() if get_ua_state_por_el0() somehow returns an error. - Kevin