From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754031AbdKNJaP (ORCPT ); Tue, 14 Nov 2017 04:30:15 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:42234 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753947AbdKNJ3l (ORCPT ); Tue, 14 Nov 2017 04:29:41 -0500 From: Kamalesh Babulal To: Michael Ellerman Cc: Kamalesh Babulal , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, live-patching@vger.kernel.org, Josh Poimboeuf , Balbir Singh Subject: [PATCH v4 2/3] powerpc/modules: Don't try to restore r2 after a sibling call Date: Tue, 14 Nov 2017 04:29:09 -0500 X-Mailer: git-send-email 2.9.3 In-Reply-To: <20171114092910.20399-1-kamalesh@linux.vnet.ibm.com> References: <20171114092910.20399-1-kamalesh@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 17111409-0040-0000-0000-0000040E0AFA X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17111409-0041-0000-0000-000020B0BD52 Message-Id: <20171114092910.20399-3-kamalesh@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-11-14_05:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1711140129 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Josh Poimboeuf When attempting to load a livepatch module, I got the following error: module_64: patch_module: Expect noop after relocate, got 3c820000 The error was triggered by the following code in unregister_netdevice_queue(): 14c: 00 00 00 48 b 14c 14c: R_PPC64_REL24 net_set_todo 150: 00 00 82 3c addis r4,r2,0 GCC didn't insert a nop after the branch to net_set_todo() because it's a sibling call, so it never returns. The nop isn't needed after the branch in that case. Signed-off-by: Josh Poimboeuf Signed-off-by: Kamalesh Babulal --- arch/powerpc/kernel/module_64.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c index 39b01fd..9e5391f 100644 --- a/arch/powerpc/kernel/module_64.c +++ b/arch/powerpc/kernel/module_64.c @@ -489,6 +489,10 @@ static int restore_r2(u32 *instruction, struct module *me) if (is_early_mcount_callsite(instruction - 1)) return 1; + /* Sibling calls don't return, so they don't need to restore r2 */ + if (instruction[-1] == PPC_INST_BRANCH) + return 1; + if (*instruction != PPC_INST_NOP) { pr_err("%s: Expect noop after relocate, got %08x\n", me->name, *instruction); -- 2.9.3