linux/tools/bpf/bpftool
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
..
bash-completion bpftool: Support sendmsg{4,6} attach types 2018-05-30 12:53:00 +02:00
Documentation bpftool: Support sendmsg{4,6} attach types 2018-05-30 12:53:00 +02:00
.gitignore selftests/bpf: ignore build products 2018-05-10 00:41:06 +02:00
cfg.c tools: bpftool: generate .dot graph from CFG information 2018-03-01 18:29:49 -08:00
cfg.h tools: bpftool: detect sub-programs from the eBPF sequence 2018-03-01 18:29:48 -08:00
cgroup.c bpftool: Support sendmsg{4,6} attach types 2018-05-30 12:53:00 +02:00
common.c tools: bpftool: add simple perf event output reader 2018-05-04 23:41:04 +02:00
jit_disasm.c tools: bpftool: improve architecture detection by using ifindex 2018-01-18 01:26:15 +01:00
json_writer.c tools: bpftool: add JSON output for bpftool prog dump xlated * command 2017-10-24 01:25:08 +01:00
json_writer.h tools: bpftool: add JSON output for bpftool prog dump xlated * command 2017-10-24 01:25:08 +01:00
main.c tools/bpftool: add perf subcommand 2018-05-24 18:18:20 -07:00
main.h tools/bpftool: add perf subcommand 2018-05-24 18:18:20 -07:00
Makefile tools: bpftool: add simple perf event output reader 2018-05-04 23:41:04 +02:00
map_perf_ring.c tools: bpf: move the event reading loop to libbpf 2018-05-11 01:40:52 +02:00
map.c bpf: bpftool, support for sockhash 2018-05-16 22:00:21 +02:00
perf.c tools/bpftool: fix a bug in bpftool perf 2018-06-13 02:03:17 +02:00
prog.c bpf: add selftest for lirc_mode2 type program 2018-05-30 12:40:14 +02:00
xlated_dumper.c tools: bpftool: add delimiters to multi-function JITed dumps 2018-05-24 09:20:50 +02:00
xlated_dumper.h tools: bpftool: add delimiters to multi-function JITed dumps 2018-05-24 09:20:50 +02:00