Messages in this thread | | | From | Song Liu <> | Subject | Re: [PATCH v4 2/9] perf/core: open access for CAP_SYS_PERFMON privileged process | Date | Mon, 13 Jan 2020 20:39:10 +0000 |
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> On Jan 11, 2020, at 1:57 AM, Alexey Budankov <alexey.budankov@linux.intel.com> wrote: > > > On 11.01.2020 3:35, arnaldo.melo@gmail.com wrote: >> <keescook@chromium.org>,Jann Horn <jannh@google.com>,Thomas Gleixner <tglx@linutronix.de>,Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,Lionel Landwerlin <lionel.g.landwerlin@intel.com>,linux-kernel <linux-kernel@vger.kernel.org>,"linux-security-module@vger.kernel.org" <linux-security-module@vger.kernel.org>,"selinux@vger.kernel.org" <selinux@vger.kernel.org>,"intel-gfx@lists.freedesktop.org" <intel-gfx@lists.freedesktop.org>,"bpf@vger.kernel.org" <bpf@vger.kernel.org>,"linux-parisc@vger.kernel.org" <linux-parisc@vger.kernel.org>,"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,"linux-perf-users@vger.kernel.org" <linux-perf-users@vger.kernel.org>,"linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>,"oprofile-list@lists.sf.net" <oprofile-list@lists.sf.net> >> From: Arnaldo Carvalho de Melo <acme@kernel.org> >> Message-ID: <A7F0BF73-9189-44BA-9264-C88F2F51CBF3@kernel.org> >> >> On January 10, 2020 9:23:27 PM GMT-03:00, Song Liu <songliubraving@fb.com> wrote: >>> >>> >>>> On Jan 10, 2020, at 3:47 PM, Masami Hiramatsu <mhiramat@kernel.org> >>> wrote: >>>> >>>> On Fri, 10 Jan 2020 13:45:31 -0300 >>>> Arnaldo Carvalho de Melo <acme@kernel.org> wrote: >>>> >>>>> Em Sat, Jan 11, 2020 at 12:52:13AM +0900, Masami Hiramatsu escreveu: >>>>>> On Fri, 10 Jan 2020 15:02:34 +0100 Peter Zijlstra >>> <peterz@infradead.org> wrote: >>>>>>> Again, this only allows attaching to previously created kprobes, >>> it does >>>>>>> not allow creating kprobes, right? >>>>> >>>>>>> That is; I don't think CAP_SYS_PERFMON should be allowed to create >>>>>>> kprobes. >>>>> >>>>>>> As might be clear; I don't actually know what the user-ABI is for >>>>>>> creating kprobes. >>>>> >>>>>> 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. >>>>> >>>>> Masami, any plans to make 'perf probe' use the perf_event_open() >>>>> interface for creating kprobes/uprobes? >>>> >>>> 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. >>> >>> I guess we can extend event parser to understand kprobe directly. >>> Instead of >>> >>> perf probe kernel_func >>> perf stat/record -e probe:kernel_func ... >>> >>> We can just do >>> >>> perf stat/record -e kprobe:kernel_func ... >> >> >> You took the words from my mouth, exactly, that is a perfect use case, an 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 the explicit probe setup case. > > Arnaldo, Masami, Song, > > What do you think about making this also open to CAP_SYS_PERFMON privileged processes?
I think we should at least allow CAP_SYS_PERFMON to create some kprobes. Maybe we can limited that to per-task kprobes, and the task should be owned by the user?
Thanks, Song
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