android_kernel_xiaomi_sm8350/tools/bpf/bpftool/Documentation/bpftool-feature.rst
Quentin Monnet 775bc8ada8 tools: bpftool: add -d option to get debug output from libbpf
libbpf has three levels of priority for output messages: warn, info,
debug. By default, debug output is not printed to the console.

Add a new "--debug" (short name: "-d") option to bpftool to print libbpf
logs for all three levels.

Internally, we simply use the function provided by libbpf to replace the
default printing function by one that prints logs regardless of their
level.

v2:
- Remove the possibility to select the log-levels to use (v1 offered a
  combination of "warn", "info" and "debug").
- Rename option and offer a short name: -d|--debug.
- Add option description to all bpftool manual pages (instead of
  bpftool-prog.rst only), as all commands use libbpf.

Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2019-05-28 11:02:21 +02:00

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===============
bpftool-feature
===============
-------------------------------------------------------------------------------
tool for inspection of eBPF-related parameters for Linux kernel or net device
-------------------------------------------------------------------------------
:Manual section: 8
SYNOPSIS
========
**bpftool** [*OPTIONS*] **feature** *COMMAND*
*OPTIONS* := { { **-j** | **--json** } [{ **-p** | **--pretty** }] }
*COMMANDS* := { **probe** | **help** }
FEATURE COMMANDS
================
| **bpftool** **feature probe** [*COMPONENT*] [**macros** [**prefix** *PREFIX*]]
| **bpftool** **feature help**
|
| *COMPONENT* := { **kernel** | **dev** *NAME* }
DESCRIPTION
===========
**bpftool feature probe** [**kernel**] [**macros** [**prefix** *PREFIX*]]
Probe the running kernel and dump a number of eBPF-related
parameters, such as availability of the **bpf()** system call,
JIT status, eBPF program types availability, eBPF helper
functions availability, and more.
If the **macros** keyword (but not the **-j** option) is
passed, a subset of the output is dumped as a list of
**#define** macros that are ready to be included in a C
header file, for example. If, additionally, **prefix** is
used to define a *PREFIX*, the provided string will be used
as a prefix to the names of the macros: this can be used to
avoid conflicts on macro names when including the output of
this command as a header file.
Keyword **kernel** can be omitted. If no probe target is
specified, probing the kernel is the default behaviour.
Note that when probed, some eBPF helpers (e.g.
**bpf_trace_printk**\ () or **bpf_probe_write_user**\ ()) may
print warnings to kernel logs.
**bpftool feature probe dev** *NAME* [**macros** [**prefix** *PREFIX*]]
Probe network device for supported eBPF features and dump
results to the console.
The two keywords **macros** and **prefix** have the same
role as when probing the kernel.
**bpftool feature help**
Print short help message.
OPTIONS
=======
-h, --help
Print short generic help message (similar to **bpftool help**).
-V, --version
Print version number (similar to **bpftool version**).
-j, --json
Generate JSON output. For commands that cannot produce JSON, this
option has no effect.
-p, --pretty
Generate human-readable JSON output. Implies **-j**.
-d, --debug
Print all logs available from libbpf, including debug-level
information.
SEE ALSO
========
**bpf**\ (2),
**bpf-helpers**\ (7),
**bpftool**\ (8),
**bpftool-prog**\ (8),
**bpftool-map**\ (8),
**bpftool-cgroup**\ (8),
**bpftool-net**\ (8),
**bpftool-perf**\ (8),
**bpftool-btf**\ (8)