提交 73df93c5 编写于 作者: Y Yonghong Song 提交者: Daniel Borkmann

tools/bpftool: fix a bug in bpftool perf

Commit b04df400 ("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: b04df400 ("tools/bpftool: add perf subcommand")
Reported-by: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NYonghong Song <yhs@fb.com>
Reviewed-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
上级 5d902372
...@@ -29,9 +29,10 @@ static bool has_perf_query_support(void) ...@@ -29,9 +29,10 @@ static bool has_perf_query_support(void)
if (perf_query_supported) if (perf_query_supported)
goto out; goto out;
fd = open(bin_name, O_RDONLY); fd = open("/", O_RDONLY);
if (fd < 0) { if (fd < 0) {
p_err("perf_query_support: %s", strerror(errno)); p_err("perf_query_support: cannot open directory \"/\" (%s)",
strerror(errno));
goto out; goto out;
} }
......
Markdown is supported
0% .
You are about to add 0 people to the discussion. Proceed with caution.
先完成此消息的编辑!
想要评论请 注册