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Tue, 29 Aug 2023 06:35:16 +0000 (GMT) Received: from ozlabs.au.ibm.com (unknown [9.192.253.14]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTP for ; Tue, 29 Aug 2023 06:35:16 +0000 (GMT) Received: from bgray-lenovo-p15.ozlabs.ibm.com (haven.au.ibm.com [9.192.254.114]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.au.ibm.com (Postfix) with ESMTPSA id 90F7C6046C; Tue, 29 Aug 2023 16:35:13 +1000 (AEST) From: Benjamin Gray To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH 2/3] powerpc/watchpoint: Disable pagefaults when getting user instruction Date: Tue, 29 Aug 2023 16:34:56 +1000 Message-ID: <20230829063457.54157-3-bgray@linux.ibm.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230829063457.54157-1-bgray@linux.ibm.com> References: <20230829063457.54157-1-bgray@linux.ibm.com> MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: wGUE3PDuD2Kxwjr-1StG5KDJHXUxBvFy X-Proofpoint-GUID: wGUE3PDuD2Kxwjr-1StG5KDJHXUxBvFy X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.267,Aquarius:18.0.957,Hydra:6.0.601,FMLib:17.11.176.26 definitions=2023-08-29_03,2023-08-28_04,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 mlxscore=0 adultscore=0 impostorscore=0 mlxlogscore=608 malwarescore=0 bulkscore=0 clxscore=1015 priorityscore=1501 spamscore=0 phishscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2308100000 definitions=main-2308290056 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Benjamin Gray Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" This is called in an atomic context, so is not allowed to sleep if a user page needs to be faulted in and has nowhere it can be deferred to. The pagefault_disabled() function is documented as preventing user access methods from sleeping. In practice the page will be mapped in nearly always because we are reading the instruction that just triggered the watchpoint trap. Signed-off-by: Benjamin Gray --- arch/powerpc/kernel/hw_breakpoint_constraints.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/hw_breakpoint_constraints.c b/arch/powerpc/kernel/hw_breakpoint_constraints.c index a74623025f3a..9e51801c4915 100644 --- a/arch/powerpc/kernel/hw_breakpoint_constraints.c +++ b/arch/powerpc/kernel/hw_breakpoint_constraints.c @@ -131,8 +131,13 @@ void wp_get_instr_detail(struct pt_regs *regs, ppc_inst_t *instr, int *type, int *size, unsigned long *ea) { struct instruction_op op; + int err; - if (__get_user_instr(*instr, (void __user *)regs->nip)) + pagefault_disable(); + err = __get_user_instr(*instr, (void __user *)regs->nip); + pagefault_enable(); + + if (err) return; analyse_instr(&op, regs, *instr);