From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 06439E8B36D for ; Tue, 3 Feb 2026 22:29:14 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4f5J7D6PH3z2yFQ; Wed, 04 Feb 2026 09:29:12 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip=63.228.1.57 ARC-Seal: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1770157752; cv=none; b=TDxuNi4ovb7JIy+etMta5yOI1kwGCpHjbliRz1awYTicsQQg2qRRy6HRH+43Hl5D3jfjITZFt0K9sxOir1gG1de4wnUFOLhse+ud75IbnRFIzgEGdxVtwO73l9rq8igoi9FLKkmsJfXdNjzXrttM3OypZPPxvguSxgpcV6Eq61D0xcCPJotSWoe/H37Dfgt3gFlD+iC8B0AeSgnK2nKGUOOgJUKlqV9wwlW9cST5vjQtlBcXv2hhTzWX4UwKNFpxdgharvMZb+SyBElMXKo5xuJePj5CBfaRBxNxXbo+FqZEjkktMT+VBHAbV2wqFRhDjwIUW5tGaE7pVZIH4LY6mg== ARC-Message-Signature: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1770157752; c=relaxed/relaxed; bh=Mcn9IlcZ31nIdqD6XJ39e/F8iEV1JgZ372/KWmM9QS0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Ps3I0Oe77kmL8l1RZ51JME2ctMNpKuuc5BUjnKYkGrAakJY1Px456nFs1ZBvbBlqYvuu7sZigU3wBNpvyTXMHiDhJXBVV0lGqM2MKmBAYgiNWfTqWNoDRm6cJomSDMM8ScMUKmjfzbKTZ+HL7PSc9Th2p99PLl8CY1vF4BBGYp3TN/j5FOpHQqtxVrEcbjGIP7I/7MCsi1zXTwrVF5uZrq7RqPgBb+c9PrQrp1/C+Z54LgwtOeqKyszr0b7eWCYdREEFsA5bvWiGsTfrbvW/0F1FcH8n1j1Zl2z8Ry67+lfRGsJQ0wreuZ+p+SZD69eORJBRfYoubscqEmkdxPKHkg== ARC-Authentication-Results: i=1; lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org; spf=pass (client-ip=63.228.1.57; helo=gate.crashing.org; envelope-from=segher@kernel.crashing.org; receiver=lists.ozlabs.org) smtp.mailfrom=kernel.crashing.org Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.crashing.org (client-ip=63.228.1.57; helo=gate.crashing.org; envelope-from=segher@kernel.crashing.org; receiver=lists.ozlabs.org) Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) by lists.ozlabs.org (Postfix) with ESMTP id 4f5J7C3fw4z2xs4 for ; Wed, 04 Feb 2026 09:29:10 +1100 (AEDT) Received: from gate.crashing.org (localhost [127.0.0.1]) by gate.crashing.org (8.18.1/8.18.1/Debian-2) with ESMTP id 613MSbKs3677924; Tue, 3 Feb 2026 16:28:37 -0600 Received: (from segher@localhost) by gate.crashing.org (8.18.1/8.18.1/Submit) id 613MSauR3677923; Tue, 3 Feb 2026 16:28:36 -0600 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Tue, 3 Feb 2026 16:28:36 -0600 From: Segher Boessenkool To: "Christophe Leroy (CS GROUP)" Cc: Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, llvm@lists.linux.dev, kernel test robot Subject: Re: [PATCH] powerpc/uaccess: Fix inline assembly for clang build on PPC32 Message-ID: References: <8ca3a657a650e497a96bfe7acde2f637dadab344.1770103646.git.chleroy@kernel.org> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8ca3a657a650e497a96bfe7acde2f637dadab344.1770103646.git.chleroy@kernel.org> Hi! On Tue, Feb 03, 2026 at 08:30:41AM +0100, Christophe Leroy (CS GROUP) wrote: > Test robot reports the following error with clang-16.0.6: > > In file included from kernel/rseq.c:75: > include/linux/rseq_entry.h:141:3: error: invalid operand for instruction > unsafe_get_user(offset, &ucs->post_commit_offset, efault); > ^ > include/linux/uaccess.h:608:2: note: expanded from macro 'unsafe_get_user' > arch_unsafe_get_user(x, ptr, local_label); \ > ^ > arch/powerpc/include/asm/uaccess.h:518:2: note: expanded from macro 'arch_unsafe_get_user' > __get_user_size_goto(__gu_val, __gu_addr, sizeof(*(p)), e); \ > ^ > arch/powerpc/include/asm/uaccess.h:284:2: note: expanded from macro '__get_user_size_goto' > __get_user_size_allowed(x, ptr, size, __gus_retval); \ > ^ > arch/powerpc/include/asm/uaccess.h:275:10: note: expanded from macro '__get_user_size_allowed' > case 8: __get_user_asm2(x, (u64 __user *)ptr, retval); break; \ > ^ > arch/powerpc/include/asm/uaccess.h:258:4: note: expanded from macro '__get_user_asm2' > " li %1+1,0\n" \ > ^ > :7:5: note: instantiated into assembly here > li 31+1,0 > ^ > 1 error generated. > > On PPC32, for 64 bits vars a pair of registers is used. Usually the > lower register in the pair is the high part and the higher register is > the low part. GCC uses r3/r4 ... r11/r12 ... r14/r15 ... r30/r31 > > In older kernel code inline assembly was using %1 and %1+1 to represent > 64 bits values. However here it looks like clang uses r31 as high part, > allthough r32 doesn't exist hence the error. > > Allthoug %1+1 should work, most places now use %L1 instead of %1+1, so > let's do the same here. > > With that change, the build doesn't fail anymore and a disassembly shows > clang uses r17/r18 and r31/r14 pair when GCC would have used r16/r17 and > r30/r31: This does not fix the problem that somehow LLVM thinks that GPR31/FPR0 is a valid pair for two-register integer things (well, 31+1 in assembler is not actually valid at all). Quite worrying. Maybe you can fix this in a more fundamental way? In LLVM itself? (The kernel patch of course is a nice workaround, if it in fact works reliably, but a big fat comment here would be useful. Pointing to the LLVM problem report where this is tracked, etc.) Segher