From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 A76DC353EDF for ; Thu, 13 Aug 2026 09:51:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786614715; cv=none; b=TC0tjXk8DkMHFrqk79UoaixeDPNqqRxhyX2hdG9AZEqBdI2JUad/TDZJ0kavmhnQsR4l7prAxpShcCIZFMoYCehHDFb9M9NnnOFMmG/HKCPU7Ske391QwWFLPRq8GZGe2xac2SP9/MkoDktXIt8NbXOCmxs1zfKSDlDWlkAy4MA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786614715; c=relaxed/simple; bh=9V6JAKr006bByYl75XRo8iQeBiukZBHWWnSZK+lmo9k=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=kbt13w+6KhmtWBgJRO0JCO749zzjhKJY+osSTzDjoovW9i/GRwVlDjFm+pyZofAZAHKSC626CNdrp2G05VB3z/W6H8bD6cxb1hZca4jPxg5Eynm9MenzYWGnJ197AoWdENnZU4avQzQRbGpv7DNdO2HOl3G1FYtOjzlOU1Q8ZkU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=hb6l+bMP; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="hb6l+bMP" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; 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; bh=Gfat6X/G5nt2aFN1UXVUUGvs3yP2Msp7A0Kfwmj1+5w=; b=hb6l+bMPZFVmMSWtDf5/qV7CXr 5Vp9Z39tZaP0iHerL6eN6O+JKEAyWyigwQnNz1eU57xdnjGdcVXcJa2ozb97VbwTM0rIlZIVEzhYv lzzZEv2569nGpXOQEAZrsr7SRJgyOVAS360eeFZPPSnckt0wDZRliugXWA9k5tt4+f/Wvn0s79tzD yf6N3TUvzDU64lERyr1zxF0S8Hxiqte4UFEACVSNmUV3T/zSEBeU35HtVw5TYJhv0FsYvDV0Em0HZ Was/olCiQyDeW6AGyU2J1NIvBrXcmubolPLzQdzyjhFlKH+4yZfMFhgaJjl2u25bR8VuZ2YF1AhJO mUK6EYFQ==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1wuS6B-00000003Nc3-3I84; Thu, 13 Aug 2026 09:51:43 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 53D123013F0; Thu, 13 Aug 2026 11:51:39 +0200 (CEST) Date: Thu, 13 Aug 2026 11:51:39 +0200 From: Peter Zijlstra To: =?utf-8?B?5p2O5YiZ6Imv?= Cc: =?iso-8859-1?Q?J=FCrgen_Gro=DF?= , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Kees Cook , Nathan Chancellor , Josh Poimboeuf , linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86/alternatives: gracefully skip unrecognized indirect call instructions Message-ID: <20260813095139.GB1246887@noisy.programming.kicks-ass.net> References: <191300ae-0f0d-430e-955f-bdd2aea4997e@suse.com> <20260812110023.GL776954@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-kernel@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: On Thu, Aug 13, 2026 at 01:14:41AM +0800, 李则良 wrote: > > > > I don't think we want to cater for this. But what actual instruction > > sequences is it emitting? > > This is the scene that triggers the bug, which can be perfectly > reproduced when KCFLAGS=-O1. > That's not what I asked, now was it. I asked what opcodes it does generate. Disassemble an affected function and show the difference between the normal -O2 and your -O1 build that causes the failure.