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Fri, 5 Sep 2025 06:12:05 GMT Received: from smtprelay03.dal12v.mail.ibm.com ([172.16.1.5]) by ppma13.dal12v.mail.ibm.com (PPS) with ESMTPS id 48vdumqx1a-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 05 Sep 2025 06:12:05 +0000 Received: from smtpav02.dal12v.mail.ibm.com (smtpav02.dal12v.mail.ibm.com [10.241.53.101]) by smtprelay03.dal12v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 5856C4aZ48955772 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 5 Sep 2025 06:12:04 GMT Received: from smtpav02.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A5CA65805F; Fri, 5 Sep 2025 06:12:04 +0000 (GMT) Received: from smtpav02.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7C6D55805C; Fri, 5 Sep 2025 06:12:00 +0000 (GMT) Received: from jarvis.j0t-au.ibm.com (unknown [9.90.171.232]) by smtpav02.dal12v.mail.ibm.com (Postfix) with ESMTP; Fri, 5 Sep 2025 06:12:00 +0000 (GMT) From: Andrew Donnellan To: 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: [PATCH RFC] powerpc: Panic on jump label code patching failure Date: Fri, 5 Sep 2025 16:11:35 +1000 Message-ID: <20250905061135.1451362-1-ajd@linux.ibm.com> X-Mailer: git-send-email 2.51.0 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-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwODMwMDAzMCBTYWx0ZWRfX96Lf5pinkkAe SWHwo837foscTeRwpLEUJWJrZ1Y5CaiQ/IQBsSentBEfagYO1u1JfkNmKqhkPBNPDqNul4RAsRZ YYa9JQKoS3L+jSJaJpejdnTnMKJrr2wHU5HtfUIMr8V+783ubsoiiSdmVo+mjadj8mujxAKA+wD wok/czKCjg4m2IvXMfIl+smeC8bnVp2UusT9pTrqvCTb8Z2Mq7sMejRewdrvoIdO7E0pxnz8NUs FCyfWBisZl46yM0m3OEax5erumCwdQiOLJN+k+Zyw8XGjnLf6UA+dnWd5McCeEgoNhxA1kdYZ7e 6lU3X6ACbffK77H0kI5em53z0R2LvBfH8zJQDxBbzEUPpaC1Tiql6iqj0qthuymYTYAvf+DSf32 8A3kGA85 X-Proofpoint-GUID: -XeHBqheUgEkTi5oLlF3x3FKZ_pPzdpT X-Proofpoint-ORIG-GUID: H3f_zlIX5ElpJY2djrWAYIy97iLbrzaf X-Authority-Analysis: v=2.4 cv=Ao/u3P9P c=1 sm=1 tr=0 ts=68ba7f36 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=yJojWOMRYYMA:10 a=voM4FWlXAAAA:8 a=1UX6Do5GAAAA:8 a=b3CbU_ItAAAA:8 a=VnNF1IyMAAAA:8 a=OjDvQk8CL8vKLhAk-QAA:9 a=IC2XNlieTeVoXbcui8wp:22 a=Et2XPkok5AAZYJIKzHr1:22 a=Rv2g8BkzVjQTVhhssdqe:22 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_01,2025-09-04_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1011 phishscore=0 impostorscore=0 priorityscore=1501 spamscore=0 suspectscore=0 bulkscore=0 adultscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2508300030 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)); } -- 2.51.0