From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-4.orcon.net.nz (smtp-4.orcon.net.nz [60.234.4.59]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3D36E25A655; Sun, 6 Sep 2026 02:17:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=60.234.4.59 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788661046; cv=none; b=KxR+12x48+fWNvu186VIvpxK+Iw7NQZnRIgk6R59f1arNshGwHDzJ72VhEdGTWpWEM4quOI9BwixAQHmUEogSP81S5hRMeUodg8Q9pRmC94Z0D8lcUmzGKw3VbIzPyW6wvvUY3WL4at+myHC+Vf1D3R36r4f1htcaOedULdgq/w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788661046; c=relaxed/simple; bh=b8TaBa4LiEzekil4Vt4bAoiS0AvQ2Eqv7bIMWRXdG3A=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ltVv4woUzeZPUFf1gqUBGUMufsHgejW+Z74FOCJwPbKfM1JHO22fQA3lBH6qSPF9oQyCyuItq2XzvR0QjCx9H1RabkJrPm5EgMIouzsLW3cEBt33cMTmtlcIhoE34xvnZzlvklS3seAwnsnou+ETgfd9gHXalqP3MvAucpfR2Vc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=orcon.net.nz; spf=pass smtp.mailfrom=orcon.net.nz; dkim=pass (2048-bit key) header.d=orcon.net.nz header.i=@orcon.net.nz header.b=sdiIUedM; arc=none smtp.client-ip=60.234.4.59 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=orcon.net.nz Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=orcon.net.nz Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=orcon.net.nz header.i=@orcon.net.nz header.b="sdiIUedM" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=orcon.net.nz; s=s1; h=In-Reply-To:Content-Transfer-Encoding:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=dTU2DK9Ec45Y4m03S6RF2YksWqUEMJXPgQusutCtZ9Q=; b=sdiIUedMNuF+AZGMzAwuYC+/95 eCXuJu1un2+1n8Lv0eaDZbuWvoer1+0cZhifuaPo2vlaZwrLnJgfLLIk/+Ua6ulqGc6DihQLEYQM7 7pV7IMkwb7B/BV4lVQS2tA4UkSq7HCc1J5buNSNm1x1Szxl6s3tbtE8tRuPqvjDFs4YxKS18ixuQR 59PRof384aD3nPFtDjoGdZDvzTEJcTIBFt7HC8XxGZaJMnMo6bnZqxidtriK0K4JFRNVLAtTjblJQ YMFbdHMC+9uUYzZuGAOdMn+rfXNJh6jY5u90TafbDyCRc60yt8BeS/sDlJRX/Tm/hFjDMWRB4aTS3 8eoajpMQ==; Received: from [121.99.247.178] (port=32811 helo=creeky) by smtp-4.orcon.net.nz with esmtpa (Exim 4.90_1) (envelope-from ) id 1x321E-0007NA-3e; Sun, 06 Sep 2026 13:50:04 +1200 Date: Sun, 6 Sep 2026 13:49:59 +1200 From: Michael Cree To: Magnus Lindholm Cc: Matt Turner , linux-alpha@vger.kernel.org, richard.henderson@linaro.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 03/24] alpha: select ARCH_HAS_UBSAN Message-ID: Mail-Followup-To: Michael Cree , Magnus Lindholm , Matt Turner , linux-alpha@vger.kernel.org, richard.henderson@linaro.org, linux-kernel@vger.kernel.org References: <61175f9015771b6a6d78624579ecc180f57d17e9.1788277742.git.mattst88@gmail.com> Precedence: bulk X-Mailing-List: linux-alpha@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-GeoIP: NZ X-Spam_score: -2.9 X-Spam_score_int: -28 X-Spam_bar: -- Hi Magnus, On Sat, Sep 05, 2026 at 01:15:18AM +0200, Magnus Lindholm wrote: > On Fri, Sep 4, 2026 at 10:31 PM Michael Cree wrote: > > On Wed, Sep 02, 2026 at 12:34:50AM +0200, Magnus Lindholm wrote: > > > On Tue, Sep 1, 2026 at 5:50 PM Matt Turner wrote: > > > > > > > > GCC's undefined behavior sanitizer has no architecture-specific runtime > > > > requirements. Enable it for Alpha to allow UBSAN instrumentation of the > > > > kernel. > > > > > > > I tested this patch on top of my rebased Alpha GENERIC_ENTRY patch on an > > > AlphaServer ES40. The kernel built and booted successfully with > > > CONFIG_UBSAN=y, and the UBSAN instrumentation is active. > > > > So have I, on an XP1000 and ES45. > > > > > CONFIG_UBSAN_ALIGNMENT did expose a misaligned struct bucket_table > > > allocation in lib/rhashtable.c. This appears to be a generic rhashtable > > > allocation-alignment issue rather than an Alpha UBSAN problem. > > > > But in my case the kernel vomited copious misaligned access reports, > > > > Interestingly "kernel unaligned acc" in /proc/cpuinfo remained at > > zero, which really makes me wonder whether these reports are all > > false-positives. > > > Good question, had to dig deeper here, > > Not false positives - real UB, but harmless, and I tracked down why. Thanks for taking time to find the explanation. So, technical UB but no consequence for operation. Cheers, Michael.