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Thu, 4 Feb 2021 10:49:40 +0000 (GMT) Received: from [9.199.39.112] (unknown [9.199.39.112]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 4 Feb 2021 10:49:40 +0000 (GMT) Subject: Re: [PATCH v2] powerpc/uprobes: Validation for prefixed instruction To: mpe@ellerman.id.au References: <20210204104703.273429-1-ravi.bangoria@linux.ibm.com> From: Ravi Bangoria Message-ID: <79b0bed7-8b98-d58d-dc47-644195bbc095@linux.ibm.com> Date: Thu, 4 Feb 2021 16:19:40 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20210204104703.273429-1-ravi.bangoria@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369, 18.0.737 definitions=2021-02-04_05:2021-02-04, 2021-02-04 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 clxscore=1015 malwarescore=0 bulkscore=0 spamscore=0 priorityscore=1501 suspectscore=0 phishscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2102040062 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: Ravi Bangoria , jniethe5@gmail.com, oleg@redhat.com, rostedt@goodmis.org, linux-kernel@vger.kernel.org, paulus@samba.org, sandipan@linux.ibm.com, naveen.n.rao@linux.ibm.com, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 2/4/21 4:17 PM, Ravi Bangoria wrote: > Don't allow Uprobe on 2nd word of a prefixed instruction. As per > ISA 3.1, prefixed instruction should not cross 64-byte boundary. > So don't allow Uprobe on such prefixed instruction as well. > > There are two ways probed instruction is changed in mapped pages. > First, when Uprobe is activated, it searches for all the relevant > pages and replace instruction in them. In this case, if we notice > that probe is on the 2nd word of prefixed instruction, error out > directly. Second, when Uprobe is already active and user maps a > relevant page via mmap(), instruction is replaced via mmap() code > path. But because Uprobe is invalid, entire mmap() operation can > not be stopped. In this case just print an error and continue. @mpe, arch_uprobe_analyze_insn() can return early if cpu_has_feature(CPU_FTR_ARCH_31) is not set. But that will miss out a rare scenario of user running binary with prefixed instruction on p10 predecessors. Please let me know if I should add cpu_has_feature(CPU_FTR_ARCH_31) or not. - Ravi