2 Commits

Author	SHA1	Message	Date
Yonghong Song	73df93c57c	tools/bpftool: fix a bug in bpftool perf ... Commit b04df400c3 ("tools/bpftool: add perf subcommand") introduced bpftool subcommand perf to query bpf program kuprobe and tracepoint attachments. The perf subcommand will first test whether bpf subcommand BPF_TASK_FD_QUERY is supported in kernel or not. It does it by opening a file with argv[0] and feeds the file descriptor and current task pid to the kernel for querying. Such an approach won't work if the argv[0] cannot be opened successfully in the current directory. This is especially true when bpftool is accessible through PATH env variable. The error below reflects the open failure for file argv[0] at home directory. [yhs@localhost ~]$ which bpftool /usr/local/sbin/bpftool [yhs@localhost ~]$ bpftool perf Error: perf_query_support: No such file or directory To fix the issue, let us open root directory ("/") which exists in every linux system. With the fix, the error message will correctly reflect the permission issue. [yhs@localhost ~]$ which bpftool /usr/local/sbin/bpftool [yhs@localhost ~]$ bpftool perf Error: perf_query_support: Operation not permitted HINT: non root or kernel doesn't support TASK_FD_QUERY Fixes: b04df400c3 ("tools/bpftool: add perf subcommand") Reported-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Yonghong Song <yhs@fb.com> Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>	2018-06-13 02:03:17 +02:00
Yonghong Song	b04df400c3	tools/bpftool: add perf subcommand ... The new command "bpftool perf [show | list]" will traverse all processes under /proc, and if any fd is associated with a perf event, it will print out related perf event information. Documentation is also added. Below is an example to show the results using bcc commands. Running the following 4 bcc commands: kprobe: trace.py '__x64_sys_nanosleep' kretprobe: trace.py 'r::__x64_sys_nanosleep' tracepoint: trace.py 't:syscalls:sys_enter_nanosleep' uprobe: trace.py 'p:/home/yhs/a.out:main' The bpftool command line and result: $ bpftool perf pid 21711 fd 5: prog_id 5 kprobe func __x64_sys_write offset 0 pid 21765 fd 5: prog_id 7 kretprobe func __x64_sys_nanosleep offset 0 pid 21767 fd 5: prog_id 8 tracepoint sys_enter_nanosleep pid 21800 fd 5: prog_id 9 uprobe filename /home/yhs/a.out offset 1159 $ bpftool -j perf [{"pid":21711,"fd":5,"prog_id":5,"fd_type":"kprobe","func":"__x64_sys_write","offset":0}, \ {"pid":21765,"fd":5,"prog_id":7,"fd_type":"kretprobe","func":"__x64_sys_nanosleep","offset":0}, \ {"pid":21767,"fd":5,"prog_id":8,"fd_type":"tracepoint","tracepoint":"sys_enter_nanosleep"}, \ {"pid":21800,"fd":5,"prog_id":9,"fd_type":"uprobe","filename":"/home/yhs/a.out","offset":1159}] $ bpftool prog 5: kprobe name probe___x64_sys tag e495a0c82f2c7a8d gpl loaded_at 2018-05-15T04:46:37-0700 uid 0 xlated 200B not jited memlock 4096B map_ids 4 7: kprobe name probe___x64_sys tag f2fdee479a503abf gpl loaded_at 2018-05-15T04:48:32-0700 uid 0 xlated 200B not jited memlock 4096B map_ids 7 8: tracepoint name tracepoint__sys tag 5390badef2395fcf gpl loaded_at 2018-05-15T04:48:48-0700 uid 0 xlated 200B not jited memlock 4096B map_ids 8 9: kprobe name probe_main_1 tag 0a87bdc2e2953b6d gpl loaded_at 2018-05-15T04:49:52-0700 uid 0 xlated 200B not jited memlock 4096B map_ids 9 $ ps ax | grep "python ./trace.py" 21711 pts/0 T 0:03 python ./trace.py __x64_sys_write 21765 pts/0 S+ 0:00 python ./trace.py r::__x64_sys_nanosleep 21767 pts/2 S+ 0:00 python ./trace.py t:syscalls:sys_enter_nanosleep 21800 pts/3 S+ 0:00 python ./trace.py p:/home/yhs/a.out:main 22374 pts/1 S+ 0:00 grep --color=auto python ./trace.py Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com> Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>	2018-05-24 18:18:20 -07:00