From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 6CBC13126DB for ; Thu, 18 Dec 2025 10:47:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766054829; cv=none; b=Fb9lVXHP9ndc2EVpqrVpQ6xWeyU2X0GFGuYhbydnPf8OPes7vuluUZcH4fe+XV7VkmR3FgSbh7FiZMenXDVcsyq+S+cwqQm2DNzUYKG9zFMTEzVnt7FzP4WKlvdTgvH54Qhfzqn1lYDNZDKFzqvL9Eq3Mp8zTspjKyYeThk3H8M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766054829; c=relaxed/simple; bh=g/A7oX+8ts5DP/Xw2EGoeBRSvakWmb03zjoHp4vgrZQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=BLw+hZoQ5cczeEp9QfvVGlbO/WO+fZEOR5c5CVsL9S91FJeu2g6m3JvUu56BRkPRIytALfVkanFsRErCwUqTWx2qKHhmEpJR0JHSPpDGHZDvd6IP9RWPrzOISuX+THjAaU9zKZ3GlTApUAY4IZlg0e3g0w+lbQBjGDWWrfd6oTY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=PWnqa5x+; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none 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="PWnqa5x+" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Bg5f4nNrZvTxDcKqw1lLhXwRAEudNdSHb6/OsGIH6B0=; b=PWnqa5x+oym52ePYad7AFHxv/H a7DV6Vn8eFzq1nrLkbpnoDhiBXBUe2WDq/fcBxYjwrucb5Nlf0H3UZuESODVuf76MzDDToL/ZhFYA GobsYt96uRR4KkxJxyQ5d519n9jUP6aDjW23JAk/zBeq7cMl2XsQ9ZeADUwf6hvU/ml5jHih3zs5e 73AVb44sXBKvbpGkyxAS+ikmBbzwOs7Ac9URTNZm6z2qK1eSz1Gw/pjrWcfEw2FvK9adQju3Vzmca kiWrcJjwE48ScEqzGbA96VBCNpJT7vcUrXyl/cGkrJIMF9YYnFVI2FCXs9BfolPMqQ/iAa6ZMZ8EV zXzsVnbA==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1vWAfi-00000008aWo-09r3; Thu, 18 Dec 2025 09:51:46 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 898CE300578; Thu, 18 Dec 2025 11:46:59 +0100 (CET) Date: Thu, 18 Dec 2025 11:46:59 +0100 From: Peter Zijlstra To: Uros Bizjak Cc: Jean Delvare , LKML , Josh Poimboeuf , ardb@kernel.org, Linus Torvalds , x86@kernel.org Subject: Re: Build breakage caused by the use of UDB Message-ID: <20251218104659.GT3911114@noisy.programming.kicks-ass.net> References: <20251217124119.5832bba7@endymion> <20251217123536.GE3707891@noisy.programming.kicks-ass.net> <20251217124713.GD3708021@noisy.programming.kicks-ass.net> <20251217130204.GE3708021@noisy.programming.kicks-ass.net> <20251217133431.GF3708021@noisy.programming.kicks-ass.net> <20251218085447.GJ3707891@noisy.programming.kicks-ass.net> <20251218103853.GS3911114@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=us-ascii Content-Disposition: inline In-Reply-To: <20251218103853.GS3911114@noisy.programming.kicks-ass.net> On Thu, Dec 18, 2025 at 11:38:53AM +0100, Peter Zijlstra wrote: > On Thu, Dec 18, 2025 at 11:26:13AM +0100, Uros Bizjak wrote: > > > I see... OTOH, a trivial solution would be to just use "ud2" mnemonic, > > as proposed in [1]. > > > > [1] https://lore.kernel.org/lkml/20250909100038.1709394-1-ubizjak@gmail.com/ > > Yes, there is that. I suppose I worry about all the other _ASM_BYTES > users, but since they don't actually show miscompilation, perhaps I > should not worry. > > Let me do a build with just using ud2 instead. Yep, this builds. Let me stick a changelog on with Fixes and Cc stable and stick it in x86/urgent. --- diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h index d561a8443c13..9b4e04690e1a 100644 --- a/arch/x86/include/asm/bug.h +++ b/arch/x86/include/asm/bug.h @@ -15,7 +15,7 @@ extern void __WARN_trap(struct bug_entry *bug, ...); /* * Despite that some emulators terminate on UD2, we use it for WARN(). */ -#define ASM_UD2 _ASM_BYTES(0x0f, 0x0b) +#define ASM_UD2 __ASM_FORM(ud2) #define INSN_UD2 0x0b0f #define LEN_UD2 2