linux-kernel - Re: [PATCH v1 2/4] perf trace: Migrate BPF augmentation to use a skeleton

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Message-ID: <ZNzK70eH3ISoL8r0@kernel.org>
Date:   Wed, 16 Aug 2023 10:11:11 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, Fangrui Song <maskray@...gle.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Andi Kleen <ak@...ux.intel.com>, Leo Yan <leo.yan@...aro.org>,
        Madhavan Srinivasan <maddy@...ux.ibm.com>,
        Carsten Haitzler <carsten.haitzler@....com>,
        Ravi Bangoria <ravi.bangoria@....com>,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Yang Jihong <yangjihong1@...wei.com>,
        James Clark <james.clark@....com>,
        Tiezhu Yang <yangtiezhu@...ngson.cn>,
        Eduard Zingerman <eddyz87@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Yonghong Song <yhs@...com>, Rob Herring <robh@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, llvm@...ts.linux.dev,
        Wang Nan <wangnan0@...wei.com>,
        Wang ShaoBo <bobo.shaobowang@...wei.com>,
        YueHaibing <yuehaibing@...wei.com>,
        He Kuang <hekuang@...wei.com>,
        Brendan Gregg <brendan.d.gregg@...il.com>
Subject: Re: [PATCH v1 2/4] perf trace: Migrate BPF augmentation to use a
 skeleton

Em Tue, Aug 15, 2023 at 07:34:08AM -0700, Ian Rogers escreveu:
> On Tue, Aug 15, 2023, 7:25 AM Arnaldo Carvalho de Melo <acme@...nel.org> wrote:
> >                 bpf_object__for_each_program(prog, trace.skel->obj) {
> >                         if (prog != trace.skel->progs.sys_enter && prog !=
> > trace.skel->progs.sys_exit)
> >                                 bpf_program__set_autoattach(prog,
> > /*autoattach=*/false);
> >                 }
> >
> > So that we don't have to add new lines disabling attachment when adding
> > support for other pointer receiving syscalls.
 
> Makes sense. Thanks,

Just taking notes about things to work on top of what is in
tmp.perf-tools-next, that will move to perf-tools-next soon:

We need to make these libbpf error messages appear only in verbose mode,
and probably have a hint about unprivileged BPF, a quick attempt failed
after several attempts at getting privileges :-\

Probably attaching to tracepoints is off limits to !root even with
/proc/sys/kernel/unprivileged_bpf_disabled set to zero.

[acme@...co perf-tools-next]$ perf trace ls
libbpf: Failed to bump RLIMIT_MEMLOCK (err = -1), you might need to do it explicitly!
libbpf: Error in bpf_object__probe_loading():Operation not permitted(1). Couldn't load trivial BPF program. Make sure your kernel supports BPF (CONFIG_BPF_SYSCALL=y) and/or that RLIMIT_MEMLOCK is set to big enough value.
libbpf: failed to load object 'augmented_raw_syscalls_bpf'
libbpf: failed to load BPF skeleton 'augmented_raw_syscalls_bpf': -1
Error:	No permissions to read /sys/kernel/tracing//events/raw_syscalls/sys_(enter|exit)
Hint:	Try 'sudo mount -o remount,mode=755 /sys/kernel/tracing/'

[acme@...co perf-tools-next]$

[acme@...co perf-tools-next]$ perf trace -e open* sleep 1
libbpf: Failed to bump RLIMIT_MEMLOCK (err = -1), you might need to do it explicitly!
libbpf: Error in bpf_object__probe_loading():Operation not permitted(1). Couldn't load trivial BPF program. Make sure your kernel supports BPF (CONFIG_BPF_SYSCALL=y) and/or that RLIMIT_MEMLOCK is set to big enough value.
libbpf: failed to load object 'augmented_raw_syscalls_bpf'
libbpf: failed to load BPF skeleton 'augmented_raw_syscalls_bpf': -1
Error:	No permissions to read /sys/kernel/tracing//events/raw_syscalls/sys_(enter|exit)
Hint:	Try 'sudo mount -o remount,mode=755 /sys/kernel/tracing/'

[acme@...co perf-tools-next]$ sudo mount -o remount,mode=755 /sys/kernel/tracing/
[sudo] password for acme:
[acme@...co perf-tools-next]$ perf trace -e open* sleep 1
libbpf: Failed to bump RLIMIT_MEMLOCK (err = -1), you might need to do it explicitly!
libbpf: Error in bpf_object__probe_loading():Operation not permitted(1). Couldn't load trivial BPF program. Make sure your kernel supports BPF (CONFIG_BPF_SYSCALL=y) and/or that RLIMIT_MEMLOCK is set to big enough value.
libbpf: failed to load object 'augmented_raw_syscalls_bpf'
libbpf: failed to load BPF skeleton 'augmented_raw_syscalls_bpf': -1
Error:	No permissions to read /sys/kernel/tracing//events/raw_syscalls/sys_(enter|exit)
Hint:	Try 'sudo mount -o remount,mode=755 /sys/kernel/tracing/'

[acme@...co perf-tools-next]$ sudo mount -o remount,mode=755 /sys/kernel/debug
[acme@...co perf-tools-next]$ perf trace -e open* sleep 1
libbpf: Failed to bump RLIMIT_MEMLOCK (err = -1), you might need to do it explicitly!
libbpf: Error in bpf_object__probe_loading():Operation not permitted(1). Couldn't load trivial BPF program. Make sure your kernel supports BPF (CONFIG_BPF_SYSCALL=y) and/or that RLIMIT_MEMLOCK is set to big enough value.
libbpf: failed to load object 'augmented_raw_syscalls_bpf'
libbpf: failed to load BPF skeleton 'augmented_raw_syscalls_bpf': -1
Error:	No permissions to read /sys/kernel/tracing//events/raw_syscalls/sys_(enter|exit)
Hint:	Try 'sudo mount -o remount,mode=755 /sys/kernel/tracing/'

[acme@...co perf-tools-next]$ sudo sh -c "echo 0 > /proc/sys/kernel/unprivileged_bpf_disabled"
[acme@...co perf-tools-next]$ perf trace -e open* sleep 1
libbpf: prog 'syscall_unaugmented': BPF program load failed: Operation not permitted
libbpf: prog 'syscall_unaugmented': failed to load: -1
libbpf: failed to load object 'augmented_raw_syscalls_bpf'
libbpf: failed to load BPF skeleton 'augmented_raw_syscalls_bpf': -1
Error:	No permissions to read /sys/kernel/tracing//events/raw_syscalls/sys_(enter|exit)
Hint:	Try 'sudo mount -o remount,mode=755 /sys/kernel/tracing/'

[acme@...co perf-tools-next]$ cat /proc/sys/kernel/unprivileged_bpf_disabled
0
[acme@...co perf-tools-next]$
[acme@...co perf-tools-next]$
[acme@...co perf-tools-next]$ cat /proc/sys/kernel/perf_event_paranoid
2
[acme@...co perf-tools-next]$ sudo sh -c "echo -1 > /proc/sys/kernel/perf_event_paranoid"
[acme@...co perf-tools-next]$ perf trace -e open* sleep 1
libbpf: prog 'syscall_unaugmented': BPF program load failed: Operation not permitted
libbpf: prog 'syscall_unaugmented': failed to load: -1
libbpf: failed to load object 'augmented_raw_syscalls_bpf'
libbpf: failed to load BPF skeleton 'augmented_raw_syscalls_bpf': -1
Error:	No permissions to read /sys/kernel/tracing//events/raw_syscalls/sys_(enter|exit)
Hint:	Try 'sudo mount -o remount,mode=755 /sys/kernel/tracing/'

[acme@...co perf-tools-next]$