* ext4dist: code cleanup (#2181)

 - Dynamically handle different ext4_file_operations
   (avoid wasting extra cycles).

 - make the code pep8 compliant

 - clarify comments

* ext4dist: fix: properly support kernels without ext4_file_read_iter()

Signed-off-by: Andrea Righi <righi.andrea@gmail.com>

* fixed shebangs in tools (and lib)

* fixed shebangs in examples

* do not mangle shebangs in rpm spec

* renamed style-check.sh to c-style-check.sh

* factored out python linter to a separate file

* added shebang validation to the py-style-check

* added shebangs to all python executables

* tools: the argument of get_kprobe_functions() should be a bytes object

It fixes the following error:
Traceback (most recent call last):
  File "/usr/share/bcc/tools/ext4dist", line 189, in <module>
    if BPF.get_kprobe_functions('ext4_file_read_iter'):
  File "/usr/lib/python3.6/site-packages/bcc/__init__.py", line 519, in get_kprobe_functions
    if (t.lower() in [b't', b'w']) and re.match(event_re, fn) \
  File "/usr/lib64/python3.6/re.py", line 172, in match
    return _compile(pattern, flags).match(string)
TypeError: cannot use a string pattern on a bytes-like object

* tools: fix freeze in offwaketime

Since commit 47cecb65, the sigint signal is ignored
unconditionally which prevents offwaketime to be stopped by
pressing Ctrl-C when run without a specified duration.

* tools: Skip backward time entries in xfsslower

While using xfsslower on RHEL7 we occasionally get
following screwed up latencies:

  # xfsslower
  Tracing XFS operations slower than 1 ms
  TIME     COMM           PID    T BYTES   OFF_KB   LAT(ms) FILENAME
  13:25:03 git            3385   R 62      4704     18446744073708.55 tmp_pack_bDUbwZ
  13:25:03 git            3385   S 0       0           3.05 tmp_idx_Kjb2bW
  ...

The reason for this is that on RHEL7 it's possible to get backward
timetamp with bpf_ktime_get_ns. This needs to be fixed, but meanwhile
this fix makes sure the latencies with backward times are skipped.

For the rest of the kernels this is just sanity fix with
possibly just single compare instruction overhead.

It's temporary workaround for #728.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>

* tools: Skip backward time entries in ext4dist

While using ext4dist on RHEL7 we occasionally get
following screwed up latencies:

  # ext4dist
  Tracing ext4 operation latency... Hit Ctrl-C to end.
  ^C

  operation = write
               usecs                         : count     distribution
                   0 -> 1                    : 1134529   |********            |
                   2 -> 3                    : 2777582   |********************|
                   4 -> 7                    : 688014    |****                |
                   8 -> 15                   : 36160     |                    |
                  16 -> 31                   : 698       |                    |
                  32 -> 63                   : 6         |                    |
                  64 -> 127                  : 15        |                    |
                 128 -> 255                  : 7         |                    |
                 256 -> 511                  : 1         |                    |
                 512 -> 1023                 : 0         |                    |
                1024 -> 2047                 : 0         |                    |
                2048 -> 4095                 : 2         |                    |
                4096 -> 8191                 : 1         |                    |
                8192 -> 16383                : 5         |                    |
               16384 -> 32767                : 0         |                    |
               32768 -> 65535                : 0         |                    |

    9007199254740992 -> 18014398509481983    : 0         |                    |
   18014398509481984 -> 36028797018963967    : 1         |                    |

The reason for this is that on RHEL7 it's possible to get backward
timestamp with bpf_ktime_get_ns. This needs to be fixed, but meanwhile
this fix makes sure the latencies with backward times are skipped.

For the rest of the kernels this is just sanity fix with
possibly just single compare instruction overhead.

It's temporary workaround for #728.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>

based on kernel version, different kernel functions are kprobed.

Several python tools allow their eBPF code to be printed to
stdout for debugging.  There are other projects that would
like to share these program definitions however, instead of
duplicating code.  We previously agreed on an --ebpf option
and we now continue adding it to more tools.

Signed-off-by: Nathan Scott <nathans@redhat.com>

This fixes the bcc module and all the affected tools for issues related to string handling in Python 3. Specifically, when passing Python strings to C libraries they are encoded as ASCII, and when constructing Python strings from C strings, they are decoded first.