From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751608AbeEPFko (ORCPT ); Wed, 16 May 2018 01:40:44 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:33654 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751151AbeEPFkn (ORCPT ); Wed, 16 May 2018 01:40:43 -0400 From: Ravi Bangoria To: mpe@ellerman.id.au Cc: benh@kernel.crashing.org, paulus@samba.org, naveen.n.rao@linux.vnet.ibm.com, anton@samba.org, cyrilbur@gmail.com, matthew.brown.dev@gmail.com, sandipan@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Ravi Bangoria Subject: [RFC] powerpc/emulate_step: Fix kernel crash when VSX is not present Date: Wed, 16 May 2018 11:10:21 +0530 X-Mailer: git-send-email 2.14.3 X-TM-AS-GCONF: 00 x-cbid: 18051605-0012-0000-0000-000005D703F4 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18051605-0013-0000-0000-0000195425B7 Message-Id: <20180516054021.5328-1-ravi.bangoria@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-05-16_02:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1805160057 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org emulate_step() is not checking runtime VSX feature flag before emulating an instruction. This can cause kernel oops when kernel is compiled with CONFIG_VSX=y but running on machine where VSX is not supported or disabled. Ex, while running emulate_step tests on P6 machine: ... emulate_step_test: lvx : PASS emulate_step_test: stvx : PASS Oops: Exception in kernel mode, sig: 4 [#1] NIP [c000000000095c24] .load_vsrn+0x28/0x54 LR [c000000000094bdc] .emulate_loadstore+0x167c/0x17b0 Call Trace: [c0000000494c3770] [40fe240c7ae147ae] 0x40fe240c7ae147ae (unreliable) [c0000000494c37f0] [c000000000094bdc] .emulate_loadstore+0x167c/0x17b0 [c0000000494c3900] [c000000000094f6c] .emulate_step+0x25c/0x5bc [c0000000494c39b0] [c000000000ec90dc] .test_lxvd2x_stxvd2x+0x64/0x154 [c0000000494c3b90] [c000000000ec9204] .test_emulate_step+0x38/0x4c [c0000000494c3c00] [c00000000000de2c] .do_one_initcall+0x5c/0x2c0 [c0000000494c3cd0] [c000000000eb4bf8] .kernel_init_freeable+0x314/0x4cc [c0000000494c3db0] [c00000000000e1e4] .kernel_init+0x24/0x160 [c0000000494c3e30] [c00000000000bc24] .ret_from_kernel_thread+0x58/0xb4 With fix: ... emulate_step_test: stvx : PASS emulate_step_test: lxvd2x : FAIL emulate_step_test: stxvd2x : FAIL Fixes: https://github.com/linuxppc/linux/issues/148 Reported-by: Michael Ellerman Signed-off-by: Ravi Bangoria --- Note: VSX was first introduced on P6. But there are many VSX instructions which were introduced in later versions. So ideally, analyse_instr() should check for ISA version along with opcode. arch/powerpc/lib/sstep.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c index 34d68f1b1b40..470942f9c567 100644 --- a/arch/powerpc/lib/sstep.c +++ b/arch/powerpc/lib/sstep.c @@ -1173,6 +1173,7 @@ int analyse_instr(struct instruction_op *op, const struct pt_regs *regs, unsigned long int val, val2; unsigned int mb, me, sh; long ival; + int type; op->type = COMPUTE; @@ -2544,6 +2545,15 @@ int analyse_instr(struct instruction_op *op, const struct pt_regs *regs, #endif /* __powerpc64__ */ } + +#ifdef CONFIG_VSX + type = op->type & INSTR_TYPE_MASK; + if ((type == LOAD_VSX || type == STORE_VSX) && + !cpu_has_feature(CPU_FTR_VSX)) { + return -1; + } +#endif /* CONFIG_VSX */ + return 0; logical_done: -- 2.16.2