From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx0b-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (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 984A83C4B93; Fri, 3 Jul 2026 11:40:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.163.158.5 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783078819; cv=none; b=bZzwBKI0oEKphtupddSIrGywxXo4Ew5MxaFpuGGiPru98ChyhhgyLWf8JxswlMgFO/6UVXdP1M9REp/AmsZVblIMsPxoE5Trcm/yBz3nmh6VIuKtPXYxfWqLuxraxrlgk96FTMFkry5jx/0PLHT5N82Y4LkB7tRw1PczRK/VuwY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783078819; c=relaxed/simple; bh=oF3oIUV+LKz0emUew5qxSHFBM4G51YQMA7zouIB8abk=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=Y7hpGEQBdk5RpPFQOG9XvtoxBdqnX2ZvE02oyxGpS2vVrqu6h9nQIq4fO9FdtNO4dKSgVW+auFpyWSJXC1H34YsQWhiDB4b6VU1BFdmBnMjkxgDz+8zsKsnZingqluO69/qxpMCiOojU1Hgp9BUB6l7vutY/fMITExiqAciZMLk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com; spf=pass smtp.mailfrom=linux.ibm.com; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b=VXVUBoyp; arc=none smtp.client-ip=148.163.158.5 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b="VXVUBoyp" Received: from pps.filterd (m0360072.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 6636ITbX1761163; Fri, 3 Jul 2026 11:39:24 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc :content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=pp1; bh=oF3oIU V+LKz0emUew5qxSHFBM4G51YQMA7zouIB8abk=; b=VXVUBoyppp/UHI5Y4PknK/ 64pw1LEU//x+soMgCRCdX4EdRm1zU4BCz8O9WW4oNRLNu5JhDcy4EBLyBm/6FrOQ hqGOcwUP7gl/7Sj9txOvVGDP8jQ9qbjCNjUToJILQOuNpLHDRC8DEuwqJjn5Bsbk jf3l63BG5cKpkTLnfzlDDlALQjJJoBf+gKHNlL4ClS0BXrHUc4dnXahOQIQvzOE2 RnjFerav6HoB22z55ZqFWCNMvqeWu1Ub2Lv9DtcEBi0qc+6pcdgn8D9isf+11H2I 9r8JlXCZvNiYvmLVs1eyz9jM/CbzeXd+fEHg62Ub1+lS6+670BWFEDmq6/u/L6Ow == Received: from ppma13.dal12v.mail.ibm.com (dd.9e.1632.ip4.static.sl-reverse.com [50.22.158.221]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 4f26mk6hfh-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 03 Jul 2026 11:39:24 +0000 (GMT) Received: from pps.filterd (ppma13.dal12v.mail.ibm.com [127.0.0.1]) by ppma13.dal12v.mail.ibm.com (8.18.1.7/8.18.1.7) with ESMTP id 663BYsLL011332; Fri, 3 Jul 2026 11:39:23 GMT Received: from smtprelay03.fra02v.mail.ibm.com ([9.218.2.224]) by ppma13.dal12v.mail.ibm.com (PPS) with ESMTPS id 4f2u2grf4e-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 03 Jul 2026 11:39:22 +0000 (GMT) Received: from smtpav07.fra02v.mail.ibm.com (smtpav07.fra02v.mail.ibm.com [10.20.54.106]) by smtprelay03.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 663BdJ1R49021346 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 3 Jul 2026 11:39:19 GMT Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 45EAF20040; Fri, 3 Jul 2026 11:39:19 +0000 (GMT) Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id CC89120043; Fri, 3 Jul 2026 11:39:18 +0000 (GMT) Received: from tuxmaker.linux.ibm.com (unknown [9.87.85.9]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTPS; Fri, 3 Jul 2026 11:39:18 +0000 (GMT) From: Sven Schnelle To: Michal =?utf-8?Q?Such=C3=A1nek?= Cc: Peter Zijlstra , Thomas Gleixner , "H. Peter Anvin" , Jonathan Corbet , Shuah Khan , Huacai Chen , WANG Xuerui , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Andy Lutomirski , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Andrew Donnellan , Mark Rutland , Arnd Bergmann , Jiaxun Yang , Ryan Roberts , Greg Kroah-Hartman , Mukesh Kumar Chaurasiya , Shrikanth Hegde , Zong Li , Nam Cao , Deepak Gupta , Lukas Gerlach , Rui Qi , Kees Cook , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org Subject: Re: [RFC] entry: Untangle the return value of syscall_enter_from_user_mode from syscall NR In-Reply-To: References: <87h5mhnjsr.ffs@fw13> <87ldbsmnie.ffs@fw13> <20260703105718.GO751831@noisy.programming.kicks-ass.net> Date: Fri, 03 Jul 2026 13:39:18 +0200 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) 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-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzAzMDExMCBTYWx0ZWRfX9A1mR90iQ9fU Jnq5F39WZRpZmJZJo+YsMXBKsZBl5gTM0jj9mCML5R/Bd24LYkLFgakI/FJBKEk/4h15P+huPhT Qt4x0X5evHrib3jUNImZ7xP5zALzpi3mdHxCzHrZiWHfDxHBlxixkSy9cDZPp/nTWVn344jkMMG O12i1eIjoY94y3kSaaPRuWeqICdkdOzFC9qN9cXcDbd4yx6KKWE4d1phTqPs9FLJ4FlkNJ8+4fa /LYyk6rTIsgzLZV9WgaObJlQoHbWw7lz4c+lbe8M9Y7kkveYms1BJh6DmtlzccJMJ25zlPyUfZ8 JmMUjXhd8ewPBbHid4BGyyAMEeqTyK6ykKlCepPfXv4InKeRsqJriegDf9oxa/3VabPxqAi+ZDP fSV0sApuWT7vTMVqvinurA0q0Phf9Nlh1Md0MKTtLGwkyMUTXh+Ps6RpfCKXyu2yzYMrNM67vWx yRdPu407r0ZBuNDOK9g== X-Proofpoint-GUID: 0UewXK-tXcTk8FWkyPWn8VMN9H9juXe0 X-Authority-Analysis: v=2.4 cv=Z8bc2nRA c=1 sm=1 tr=0 ts=6a479f6c cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=7COA2AqOHvKb0wdBt1EA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Info: AW1haW4tMjYwNzAzMDExMCBTYWx0ZWRfX+Zctx0ZJQz6V Vq7aSPRPQpmK2s8ZW9Ab8ojRDqpVU5I5jpBSa8I4jJz5wtRMPZX84BaKOeHe7JCg0Z84TaNiznM cYzIAWu4Lm8wE8gWWhsc6/49iUcKYqo= X-Proofpoint-ORIG-GUID: XUA9fyTmm3_KCsdJOv0Gf6JjV0mivGPV X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-07-03_02,2026-06-26_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 adultscore=0 spamscore=0 priorityscore=1501 impostorscore=0 malwarescore=0 phishscore=0 bulkscore=0 lowpriorityscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607030110 Michal Such=C3=A1nek writes: > The same could be asked of syscall_enter_from_user_mode. I find it very > odd. Why does it conflate the syscall number with its return value? > > It never uses the syscall number passed in except when returning it > unchanged. When it pokes the registers it reads the syscall number from > them. > > If the caller of syscall_enter_from_user_mode only read the syscall > number from the registers when syscall_enter_from_user_mode returns and > indicates the syscall should be still executed this whole shenigan would I agree. The fact that if (nr < NR_syscall) just works because -1 gets casted to 0xffffffff and is therefore out of bounds is very odd.