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 F4148CA1012 for ; Sat, 6 Sep 2025 04:11:29 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4cJfsq6mhzz2xgQ; Sat, 6 Sep 2025 14:11:27 +1000 (AEST) Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip=148.163.156.1 ARC-Seal: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1757131887; cv=none; b=HCdxS94adQ1tTEtRDGO+UMEUjEFuJ5nZFls6JyCS/6FnIfGAcAttnER40y/JeKAaX6eO83IZLoPHmYuuXMQEpIFyc/qhXALugcPaC5yqUaIkHndNUMZ2zG+DF/5HbVMw3XL6c0FTn+ZMskxfl2NoUhtomu4vRrCx3ROObV4aUf7xYGRZPlWxRLaC8WJy5435v0L60WGS//oFVLFjJOSAC3uJRIgfPt9FWi+NgIajZJa5jjC6IoSqk7G8XF9ZItVsnnes1OlKMpEcQBsnuMh60Ynn+XxvXUZM+arbODcAnvNLqHxThgAM7T3k/dNfd91Ac3e0p30MZjOZkmJc+lPxtA== ARC-Message-Signature: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1757131887; c=relaxed/relaxed; bh=/XrWDlMSknBUdI+P/nmBO66b2axhhLzm5K67zB4bETQ=; h=From:To:Cc:Subject:In-Reply-To:Date:Message-ID:References; b=HCZamm5ySti/3jtNOhjvdB45lSfyc9LlYhgjH9HZD+EbtvSUmOtiW2wyw+ARv9iciiePlImx3ivrLTXZTjVnV5lMEIMSWuxziPzh2add4U/Y2B/VBnMToB3FJo20MhK6lwtm+olFuiFXUzK+E+/21xBtMDnJlX74nuv9V8Zn5dI/a2TPoJKy1FF5zmW29cqCeAg2uQ3+21/LMcX+kFlT6WwoRYbp4I21RoVFo+zFwkrko27tycYpMYm915rN4r/2yebh18DK0oaMdaWYH5VTl9nCjX8T+jmYAeRNn9R7ilDxBXpMh3jGK8Bk/lmGV3CNNl9hefB9ZN90LS6b5IGgGw== ARC-Authentication-Results: i=1; lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com; dkim=pass (2048-bit key; unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256 header.s=pp1 header.b=bJhKJKY3; dkim-atps=neutral; spf=pass (client-ip=148.163.156.1; helo=mx0a-001b2d01.pphosted.com; envelope-from=riteshh@linux.ibm.com; receiver=lists.ozlabs.org) smtp.mailfrom=linux.ibm.com Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256 header.s=pp1 header.b=bJhKJKY3; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=linux.ibm.com (client-ip=148.163.156.1; helo=mx0a-001b2d01.pphosted.com; envelope-from=riteshh@linux.ibm.com; receiver=lists.ozlabs.org) Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4cJfsp6Nkqz2xWc for ; Sat, 6 Sep 2025 14:11:26 +1000 (AEST) Received: from pps.filterd (m0353729.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.18.1.2/8.18.1.2) with ESMTP id 5862wBNs014242; Sat, 6 Sep 2025 04:10:59 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc :date:from:in-reply-to:message-id:references:subject:to; s=pp1; bh=/XrWDlMSknBUdI+P/nmBO66b2axhhLzm5K67zB4bETQ=; b=bJhKJKY3GTZ6 ZfBnjHiHrRNTHRONw+rlCI97PyrMPiADjl52pdYNzRhGono/R4qOmEmf6J/VWUiZ tgMvWO5Yo+6kIYQaDBa7hkSr8CincgRV6egUrdXktbA7IZVdhRHeI/LB7bs1yx3U KLr1cVeSS56D5dpCtmgWKsfvtLkvCNXKVBSne0Jjq8EvdTZOTNOWU63gn4B+MxQz U9UqRAO2vYxiEBshfYItKOc1Ww0mmAi0dTXd9dxv8WTSOQNNF6U3zQ2uhMcz9x7d K0v3n2IHMynGnC5oIAMy5aG4PIe8d4OOJa4TIuMK3y1/bws+b133X1N5yzVbjnDB tBH1dCdJAA== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 490cmw85dg-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sat, 06 Sep 2025 04:10:59 +0000 (GMT) Received: from m0353729.ppops.net (m0353729.ppops.net [127.0.0.1]) by pps.reinject (8.18.1.12/8.18.0.8) with ESMTP id 5864Am07010706; Sat, 6 Sep 2025 04:10:58 GMT Received: from ppma22.wdc07v.mail.ibm.com (5c.69.3da9.ip4.static.sl-reverse.com [169.61.105.92]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 490cmw85de-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sat, 06 Sep 2025 04:10:58 +0000 (GMT) Received: from pps.filterd (ppma22.wdc07v.mail.ibm.com [127.0.0.1]) by ppma22.wdc07v.mail.ibm.com (8.18.1.2/8.18.1.2) with ESMTP id 5861EI5v017222; Sat, 6 Sep 2025 04:10:57 GMT Received: from smtprelay03.fra02v.mail.ibm.com ([9.218.2.224]) by ppma22.wdc07v.mail.ibm.com (PPS) with ESMTPS id 48vc114mc8-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sat, 06 Sep 2025 04:10:57 +0000 Received: from smtpav03.fra02v.mail.ibm.com (smtpav03.fra02v.mail.ibm.com [10.20.54.102]) by smtprelay03.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 5864ArSW50790870 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sat, 6 Sep 2025 04:10:53 GMT Received: from smtpav03.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7A33B20043; Sat, 6 Sep 2025 04:10:53 +0000 (GMT) Received: from smtpav03.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1011820040; Sat, 6 Sep 2025 04:10:49 +0000 (GMT) Received: from dw-tp (unknown [9.36.11.250]) by smtpav03.fra02v.mail.ibm.com (Postfix) with ESMTPS; Sat, 6 Sep 2025 04:10:48 +0000 (GMT) From: Ritesh Harjani (IBM) To: Andrew Donnellan , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, maddy@linux.ibm.com, mpe@ellerman.id.au, christophe.leroy@csgroup.eu, peterz@infradead.org, jpoimboe@kernel.org, jbaron@akamai.com Cc: npiggin@gmail.com, rostedt@goodmis.org, ardb@kernel.org, Erhard Furtner Subject: Re: [PATCH RFC] powerpc: Panic on jump label code patching failure In-Reply-To: <20250905061135.1451362-1-ajd@linux.ibm.com> Date: Sat, 06 Sep 2025 09:22:04 +0530 Message-ID: <87qzwki6fv.fsf@ritesh.list@gmail.com> References: <20250905061135.1451362-1-ajd@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: PVMDvjw-tL3NZRtUaiBXxzMfAvigclEn X-Proofpoint-ORIG-GUID: cbeOG78TMkQe-VMJ3z_O--cBwR6-zolj X-Authority-Analysis: v=2.4 cv=J52q7BnS c=1 sm=1 tr=0 ts=68bbb453 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=yJojWOMRYYMA:10 a=voM4FWlXAAAA:8 a=1UX6Do5GAAAA:8 a=VnNF1IyMAAAA:8 a=b3CbU_ItAAAA:8 a=iqv5_9DZO53ucXEhF-8A:9 a=IC2XNlieTeVoXbcui8wp:22 a=Et2XPkok5AAZYJIKzHr1:22 a=Rv2g8BkzVjQTVhhssdqe:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwOTA2MDAyNSBTYWx0ZWRfX/sPPXWdUt8iA cDIg8JcAgGeV/LWC8gxJlwyS8uepFEh2etmVIgLRPiW4uFxdN7IgpLf6UcpemvESv3K951sI8py Ax0ClkRQ9JJjoBKb9tyRi+znKHDCHCL3kz9pgQz+gj6KlKQt5TWn3QpGdbEArL0+7VyVUYozjfb +gfBjzvNqxJwizwgvoNtShktjhDsliOw4V2V9ne1Wow9Ei3Mbu/JwBbkvsdDDGa1210Vjftdg8H MM+ZEMKPN4M7FV9iDgzq2HrcT3XMaxss+lCq6XJTqF9D1sbf3NsyyN6AKpfYcYUcfdWeaIkkW8m MCfH378QQAFfANXMeJD7jkhC8Ri0aabeq+B0pbUcv5YGjcvshpSVrCIlTlzPY6pkR0LkVaYIQtd QYKcGa/O X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1117,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-09-05_09,2025-09-04_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 clxscore=1011 suspectscore=0 spamscore=0 phishscore=0 bulkscore=0 adultscore=0 malwarescore=0 priorityscore=1501 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2509060025 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list Andrew Donnellan writes: > If patch_branch() or patch_instruction() fails while updating a jump > label, we presently fail silently, leading to unpredictable behaviour > later on. > > Change arch_jump_label_transform() to panic on a code patching failure, > matching the existing behaviour of arch_static_call_transform(). > > Reported-by: Erhard Furtner > Signed-off-by: Andrew Donnellan > > --- > > Ran into this while debugging an issue that Erhard reported to me about my > PAGE_TABLE_CHECK series on a G4, where updating a static key failed > silently, but only for one call site, leading to an incorrect reference > count later on. This looks to be due to the issue fixed in [0]. A loud > failure would have saved us all considerable debugging time. > > Should I change the return type of arch_jump_label_transform() and handle > this in an arch-independent way? Are there other users of code patching > in powerpc that ought to be hardened? > > Or is this excessive? > > [0] https://patchwork.ozlabs.org/project/linuxppc-dev/patch/4b5e6eb281d7b1ea77619bee17095f905a125168.1757003584.git.christophe.leroy@csgroup.eu/ > --- > arch/powerpc/kernel/jump_label.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/arch/powerpc/kernel/jump_label.c b/arch/powerpc/kernel/jump_label.c > index 2659e1ac8604..80d41ed7ac50 100644 > --- a/arch/powerpc/kernel/jump_label.c > +++ b/arch/powerpc/kernel/jump_label.c > @@ -12,9 +12,14 @@ void arch_jump_label_transform(struct jump_entry *entry, > enum jump_label_type type) > { > u32 *addr = (u32 *)jump_entry_code(entry); > + int err; > > if (type == JUMP_LABEL_JMP) > - patch_branch(addr, jump_entry_target(entry), 0); > + err = patch_branch(addr, jump_entry_target(entry), 0); > else > - patch_instruction(addr, ppc_inst(PPC_RAW_NOP())); > + err = patch_instruction(addr, ppc_inst(PPC_RAW_NOP())); > + > + if (err) > + panic("%s: patching failed, err %d, type %d, addr %pS, target %pS\n", > + __func__, err, type, addr, (void *)jump_entry_target(entry)); > } arch_jump_label_transform() is mainly getting called from __jump_level_update() and it's used for enabling or updating static keys / branch. But static keys can also be used by drivers / module subsystem whose initialization happens late. Although I understand that if the above fails, it might fail much before, from the arch setup code itself, but panic() still feels like a big hammer. Would pr_err() print with WARN_ON_ONCE(1) would suffice in case of an err? Also you said you ran into a problem at just one call site where above was silently failing. With the above change are you able to hit the panic() now? Because from what I see in patch_instruction(), it mainly will boil down to calling __patch_mem() which always returns 0. Although there are other places where there can be an error returned, so I was wondering if that is what you were hitting or something else? -ritesh > -- > 2.51.0