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tools: bpftool: Print optional built-in features along with version

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Bpftool has a number of features that can be included or left aside
during compilation. This includes:

- Support for libbfd, providing the disassembler for JIT-compiled
  programs.
- Support for BPF skeletons, used for profiling programs or iterating on
  the PIDs of processes associated with BPF objects.

In order to make it easy for users to understand what features were
compiled for a given bpftool binary, print the status of the two
features above when showing the version number for bpftool ("bpftool -V"
or "bpftool version"). Document this in the main manual page. Example
invocations:

    $ bpftool version
    ./bpftool v5.9.0-rc1
    features: libbfd, skeletons

    $ bpftool -p version
    {
        "version": "5.9.0-rc1",
        "features": {
            "libbfd": true,
            "skeletons": true
        }
    }

Some other parameters are optional at compilation
("DISASM_FOUR_ARGS_SIGNATURE", LIBCAP support) but they do not impact
significantly bpftool's behaviour from a user's point of view, so their
status is not reported.

Available commands and supported program types depend on the version
number, and are therefore not reported either. Note that they are
already available, albeit without JSON, via bpftool's help messages.

v3:
- Use a simple list instead of boolean values for plain output.

v2:
- Fix JSON (object instead or array for the features).

Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200909162500.17010-2-quentin@isovalent.com
This commit is contained in:
Quentin Monnet 2020-09-09 17:24:58 +01:00 committed by Alexei Starovoitov
parent 41d5c37b74
commit 82b8cf0acc
2 changed files with 38 additions and 3 deletions
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8
tools/bpf/bpftool/Documentation/bpftool.rst
View File

@ -50,7 +50,13 @@ OPTIONS
Print short help message (similar to **bpftool help**).
-V, --version
Print version number (similar to **bpftool version**).
Print version number (similar to **bpftool version**), and
optional features that were included when bpftool was
compiled. Optional features include linking against libbfd to
provide the disassembler for JIT-ted programs (**bpftool prog
dump jited**) and usage of BPF skeletons (some features like
**bpftool prog profile** or showing pids associated to BPF
objects may rely on it).
-j, --json
Generate JSON output. For commands that cannot produce JSON, this

33
tools/bpf/bpftool/main.c
View File

@ -70,13 +70,42 @@ static int do_help(int argc, char **argv)
static int do_version(int argc, char **argv)
{
#ifdef HAVE_LIBBFD_SUPPORT
const bool has_libbfd = true;
#else
const bool has_libbfd = false;
#endif
#ifdef BPFTOOL_WITHOUT_SKELETONS
const bool has_skeletons = false;
#else
const bool has_skeletons = true;
#endif
if (json_output) {
jsonw_start_object(json_wtr);
jsonw_start_object(json_wtr); /* root object */
jsonw_name(json_wtr, "version");
jsonw_printf(json_wtr, "\"%s\"", BPFTOOL_VERSION);
jsonw_end_object(json_wtr);
jsonw_name(json_wtr, "features");
jsonw_start_object(json_wtr); /* features */
jsonw_bool_field(json_wtr, "libbfd", has_libbfd);
jsonw_bool_field(json_wtr, "skeletons", has_skeletons);
jsonw_end_object(json_wtr); /* features */
jsonw_end_object(json_wtr); /* root object */
} else {
unsigned int nb_features = 0;
printf("%s v%s\n", bin_name, BPFTOOL_VERSION);
printf("features:");
if (has_libbfd) {
printf(" libbfd");
nb_features++;
}
if (has_skeletons)
printf("%s skeletons", nb_features++ ? "," : "");
printf("\n");
}
return 0;
}