From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (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 D1AFA1FBC8E for ; Tue, 28 Oct 2025 18:56:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761677782; cv=none; b=tR2F+N0pNBTYQZPAdRrlgyCnbKctSzfwgGrjN/Xu3ICIT0LjX0Cbb3FTUITeoF8bm690PcNKqqYOIILAjQuNYF1xrbybPDqQ2uu7NlG7nINj4RKdXRzFf5vmc8zpfFiUG4JS2dSat8BQjZ0cx/A4P3hqqUD9AXr1nrTK6+0ukqY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761677782; c=relaxed/simple; bh=atPVB/NslUpTU+PiXPab0qojrF1pMcoycpP3HvJooBs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=VZbjer/3hk5PeCZj45RP/SzbYIYwT8ce1voGdOGCLoP9uVDDvmp4kgNVrUgNmxVXMl3LK7FGF8rDapFaNAjSvuBlAI+j91jIeDKKW5T5JfcXQh7veAYF+OaRQvDXR9h9WUIyijt1hsgY4hLdn1PFSGwPcPuEi5+KTytp39JhO70= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=S6PRWO2Y; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="S6PRWO2Y" Received: from [IPV6:2601:646:8081:9484:71ce:e7c:a6bf:3efe] ([IPv6:2601:646:8081:9484:71ce:e7c:a6bf:3efe]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 59SIu2Iq1613600 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Tue, 28 Oct 2025 11:56:03 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 59SIu2Iq1613600 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025102301; t=1761677764; bh=p+roapVSERhQEWat+bM2z2fsS5MsGKwo/pdV1SiLyPk=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=S6PRWO2YNJzBuxOLTr+ylmX7f0iqHmVW/sLFNDCunvirk+Ab65nriYyiMMwWzqQVb QI7GL8k/Di5jWOFhtBzCnUNrrP192ETX/zI7/2Yw9Jf776RF3c5lVNes/sMztFZMKw rl0PNTIY/wxjN3pNN4uCT4vXyyng78uZICXfecDwK4zgZEV3cW8Q/N0ZiAgIeWri5R vT8PERcLtPxVUAm+Q2hIOcWRJEtla4KKcDXhzUr0E8E87t8kSGg3dQ2bjKBR/wQ963 ksnB4JWwRYfblip4MGe1yhcl1eI+GvbCbit84ZbUGoQXQO7wZ2w0fnDK8IFfDgANrl RsBbceTUeWjzg== Message-ID: <7623dfcf-f6ed-4caf-bb60-7fa953f0778c@zytor.com> Date: Tue, 28 Oct 2025 11:55:57 -0700 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 v2] x86,ibt: Use UDB instead of 0xEA To: Alexei Starovoitov , Peter Zijlstra Cc: X86 ML , Kees Cook , alyssa.milburn@intel.com, scott.d.constable@intel.com, Joao Moreira , Andrew Cooper , Sami Tolvanen , Nathan Chancellor , Masami Hiramatsu , ojeda@kernel.org, LKML References: <20250901191307.GI4067720@noisy.programming.kicks-ass.net> <20250902081915.GK3245006@noisy.programming.kicks-ass.net> <20250902192609.GL3245006@noisy.programming.kicks-ass.net> Content-Language: en-US, sv-SE From: "H. Peter Anvin" In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2025-09-02 12:37, Alexei Starovoitov wrote: > > I suspect that 'reserved' opcode will not be used any time soon. > If 10 years from now the opcode is used in some future CPU that CPU > is better to be not vulnerable and CFI, FineIBT things will be > gone from the kernel by then. > So I would do absolutely nothing and just ignore the lack of blessing. > What makes you say that? *Please* don't make these kinds of assumptions -- it causes massive headaches for both us chip makers and for users. -hpa