linux-kernel - Re: [PATCH 0/5] perf bpf: Improve error code delivering and output

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Date:	Tue, 3 Nov 2015 12:43:00 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Wang Nan <wangnan0@...wei.com>
Cc:	lizefan@...wei.com, pi3orama@....com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5] perf bpf: Improve error code delivering and output

Em Tue, Nov 03, 2015 at 10:44:41AM +0000, Wang Nan escreveu:
> This patchset is based on tip/core.
> 
> Arnaldo found some confusing error reports when reviewing BPF related
> patches. This patch set makes some changes:

Thanks for working on this!

I applied the first two and made comments about the conversion to using
err.h, please check,

- Arnaldo
 
>  - perf test only print ok, failed or skip. Extra messages can be seen
>    by '-v'.
> 
>  - libbpf not output anything when called from perf without '-v'.
> 
>  - Create libbpf and bpf-loader specific error number group to deliver
>    precise error. New strerror framework makes adding new error code
>    easier.
> 
>  - Improve error messages.
> 
> After applying this patch:
> 
> When target object not exist:
> 
>  $ ls ./foo.o
>  ls: cannot access ./foo.o: No such file or directory
>  $ ./perf record --event foo.o sleep
>  event syntax error: 'foo.o'
>                       \___ Failed to load foo.o: No such file or directory
> 
>  (add -v to see detail)
>  Run 'perf list' for a list of valid events
> 
>   Usage: perf record [<options>] [<command>]
>      or: perf record [<options>] -- <command> [<options>]
> 
>      -e, --event <event>   event selector. use 'perf list' to list available events
> 
> When target object format invalid:
> 
>  $ cp /etc/passwd ./badbpf.o
>  $ ./perf record --event ./badbpf.o sleep
>  event syntax error: './badbpf.o'
>                       \___ Failed to load ./badbpf.o: BPF object format invalid
>  (... skip ...)
> 
> When run by normal user and /proc/sys/kernel/kptr_restrict is 1:
> 
>  $ cat /proc/sys/kernel/kptr_restrict
>  1
>  $ ./perf record --event ./bpf-script-example.o sleep
>  Failed to init vmlinux path.
>  event syntax error: './bpf-script-example.o'
>                       \___ You need to be root, and /proc/sys/kernel/kptr_restrict should be 0
>  (... skip ...)
> 
> After fixing /proc/sys/kernel/kptr_restrict:
> 
>  $ sudo -s
>  # echo 0 > /proc/sys/kernel/kptr_restrict
>  # exit
>  $ ./perf record --event ./bpf-script-example.o sleep
>  Failed to open kprobe_events: Permission denied
>  event syntax error: './bpf-script-example.o'
>                       \___ You need to be root
>  (... skip ...)
> 
> Load an object with no 'version' section:
> 
>  # ./perf record --event ./bpf-script-example.o sleep
>  event syntax error: './bpf-script-example.o'
>                       \___ Failed to load ./bpf-script-example.o: 'version' section incorrect or lost
>  (... skip ...)
> 
> Load an object with incorrect 'version' section:
>  # ./perf record --event ./bpf-script-example.o sleep
>  event syntax error: './bpf-script-example.o'
>                       \___ Failed to load program: Validate your program and check 'license'/'version' sections in your object
>  (... skip ...)
> 
> When event name not set:
> 
>  # ./perf record --event ./bpf-script-example.o sleep
>  event syntax error: './bpf-script-example.o'
>                       \___ No event name found in config string
>  (... skip ...)
> 
> Wang Nan (5):
>   perf test: Keep test result clean if '-v' not set
>   perf tools: Mute libbpf when '-v' not set
>   perf tools: Parsing libbpf return value using err.h
>   bpf tools: Improve libbpf error reporting
>   perf tools: Improve BPF related error messages output
> 
>  tools/lib/bpf/libbpf.c             | 149 +++++++++++++++++++++++++------------
>  tools/lib/bpf/libbpf.h             |  12 +++
>  tools/perf/tests/attr.c            |   3 +-
>  tools/perf/tests/code-reading.c    |   8 +-
>  tools/perf/tests/keep-tracking.c   |   4 +-
>  tools/perf/tests/llvm.c            |  13 ++--
>  tools/perf/tests/switch-tracking.c |   4 +-
>  tools/perf/util/bpf-loader.c       | 110 +++++++++++++++++++++++----
>  tools/perf/util/bpf-loader.h       |  18 +++++
>  tools/perf/util/parse-events.c     |   7 +-
>  10 files changed, 243 insertions(+), 85 deletions(-)
> 
> -- 
> 1.8.3.4
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