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Mon, 13 Jan 2020 20:39:11 +0000 From: Song Liu To: Alexey Budankov CC: Arnaldo Carvalho de Melo , Masami Hiramatsu , Peter Zijlstra , Ingo Molnar , "jani.nikula@linux.intel.com" , "joonas.lahtinen@linux.intel.com" , "rodrigo.vivi@intel.com" , Alexei Starovoitov , "Benjamin Herrenschmidt" , Paul Mackerras , Michael Ellerman , "james.bottomley@hansenpartnership.com" , Serge Hallyn , James Morris , Will Deacon , "Mark Rutland" , Casey Schaufler , Robert Richter , Jiri Olsa , Andi Kleen , Stephane Eranian , Igor Lubashev , Alexander Shishkin , Namhyung Kim , linux-kernel Subject: Re: [PATCH v4 2/9] perf/core: open access for CAP_SYS_PERFMON privileged process Thread-Topic: [PATCH v4 2/9] perf/core: open access for CAP_SYS_PERFMON privileged process Thread-Index: AQHVtYUpMC7X/V/PgEituL3lQIWiD6fhEFaAgAFGyQCAAbsNAIAAHqKAgAAO5YCAAHXsgIAACgUAgAADSQCAAJ0NAIAD1/8A Date: Mon, 13 Jan 2020 20:39:10 +0000 Message-ID: <2794FEDA-8259-41C0-AF43-28AE2BEB4E26@fb.com> References: <20200108160713.GI2844@hirez.programming.kicks-ass.net> <20200110140234.GO2844@hirez.programming.kicks-ass.net> <20200111005213.6dfd98fb36ace098004bde0e@kernel.org> <20200110164531.GA2598@kernel.org> <20200111084735.0ff01c758bfbfd0ae2e1f24e@kernel.org> <2B79131A-3F76-47F5-AAB4-08BCA820473F@fb.com> <5e191833.1c69fb81.8bc25.a88c@mx.google.com> <158a4033-f8d6-8af7-77b0-20e62ec913b0@linux.intel.com> In-Reply-To: <158a4033-f8d6-8af7-77b0-20e62ec913b0@linux.intel.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-mailer: Apple Mail (2.3608.40.2.2.4) x-originating-ip: [2620:10d:c090:200::6df5] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: a87b7a05-e80c-4d39-d882-08d79868a523 x-ms-traffictypediagnostic: BYAPR15MB3334: x-microsoft-antispam-prvs: x-fb-source: Internal x-ms-oob-tlc-oobclassifiers: OLM:4125; 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charset="us-ascii" Content-ID: <4E052D1263306F4C99322179A5ACE9A7@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: a87b7a05-e80c-4d39-d882-08d79868a523 X-MS-Exchange-CrossTenant-originalarrivaltime: 13 Jan 2020 20:39:10.7277 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: 0pcBRuL6i4iyJ1QToxUvBK7pR75FeW3sWduq/pYamHSCgYNVv0QDzqigEKntEuMP7Nt9uS5ursgvpteesceZqQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB3334 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.572 definitions=2020-01-13_06:2020-01-13,2020-01-13 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 lowpriorityscore=0 priorityscore=1501 malwarescore=0 impostorscore=0 bulkscore=0 adultscore=0 clxscore=1015 suspectscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-2001130168 X-FB-Internal: deliver Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Jan 11, 2020, at 1:57 AM, Alexey Budankov wrote: >=20 >=20 > On 11.01.2020 3:35, arnaldo.melo@gmail.com wrote: >> ,Jann Horn ,Thomas Gleixner ,Tvrtko Ursulin ,Lionel La= ndwerlin ,linux-kernel ,"linux-security-module@vger.kernel.org" ,"selinux@vger.kernel.org" ,"intel-g= fx@lists.freedesktop.org" ,"bpf@vger.kerne= l.org" ,"linux-parisc@vger.kernel.org" ,"linuxppc-dev@lists.ozlabs.org" ,"linux-perf-users@vger.kernel.org" ,= "linux-arm-kernel@lists.infradead.org" ,"oprofile-list@lists.sf.net" >> From: Arnaldo Carvalho de Melo >> Message-ID: >>=20 >> On January 10, 2020 9:23:27 PM GMT-03:00, Song Liu wrote: >>>=20 >>>=20 >>>> On Jan 10, 2020, at 3:47 PM, Masami Hiramatsu >>> wrote: >>>>=20 >>>> On Fri, 10 Jan 2020 13:45:31 -0300 >>>> Arnaldo Carvalho de Melo wrote: >>>>=20 >>>>> Em Sat, Jan 11, 2020 at 12:52:13AM +0900, Masami Hiramatsu escreveu: >>>>>> On Fri, 10 Jan 2020 15:02:34 +0100 Peter Zijlstra >>> wrote: >>>>>>> Again, this only allows attaching to previously created kprobes, >>> it does >>>>>>> not allow creating kprobes, right? >>>>>=20 >>>>>>> That is; I don't think CAP_SYS_PERFMON should be allowed to create >>>>>>> kprobes. >>>>>=20 >>>>>>> As might be clear; I don't actually know what the user-ABI is for >>>>>>> creating kprobes. >>>>>=20 >>>>>> There are 2 ABIs nowadays, ftrace and ebpf. perf-probe uses ftrace >>> interface to >>>>>> define new kprobe events, and those events are treated as >>> completely same as >>>>>> tracepoint events. On the other hand, ebpf tries to define new >>> probe event >>>>>> via perf_event interface. Above one is that interface. IOW, it >>> creates new kprobe. >>>>>=20 >>>>> Masami, any plans to make 'perf probe' use the perf_event_open() >>>>> interface for creating kprobes/uprobes? >>>>=20 >>>> Would you mean perf probe to switch to perf_event_open()? >>>> No, perf probe is for setting up the ftrace probe events. I think we >>> can add an >>>> option to use perf_event_open(). But current kprobe creation from >>> perf_event_open() >>>> is separated from ftrace by design. >>>=20 >>> I guess we can extend event parser to understand kprobe directly. >>> Instead of >>>=20 >>> perf probe kernel_func >>> perf stat/record -e probe:kernel_func ... >>>=20 >>> We can just do=20 >>>=20 >>> perf stat/record -e kprobe:kernel_func ... >>=20 >>=20 >> You took the words from my mouth, exactly, that is a perfect use case, a= n alternative to the 'perf probe' one of making a disabled event that then = gets activated via record/stat/trace, in many cases it's better, removes th= e explicit probe setup case. >=20 > Arnaldo, Masami, Song, >=20 > What do you think about making this also open to CAP_SYS_PERFMON privileg= ed processes? I think we should at least allow CAP_SYS_PERFMON to create some kprobes. Ma= ybe we can=20 limited that to per-task kprobes, and the task should be owned by the user? Thanks, Song