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[bpf-next,v2,1/3] tools: bpftool: print optional built-in features along with version

Message ID 20200907163804.29244-2-quentin@isovalent.com
State Superseded
Headers show
Series [bpf-next,v2,1/3] tools: bpftool: print optional built-in features along with version | expand

Commit Message

Quentin Monnet Sept. 7, 2020, 4:38 p.m. UTC 
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
invocation:

    $ 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.

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

Signed-off-by: Quentin Monnet <quentin@isovalent.com>
---
 tools/bpf/bpftool/Documentation/bpftool.rst |  8 ++++++-
 tools/bpf/bpftool/main.c                    | 26 +++++++++++++++++++--
 2 files changed, 31 insertions(+), 3 deletions(-)
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Patch

diff --git a/tools/bpf/bpftool/Documentation/bpftool.rst b/tools/bpf/bpftool/Documentation/bpftool.rst
index 420d4d5df8b6..a3629a3f1175 100644
--- a/tools/bpf/bpftool/Documentation/bpftool.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool.rst
@@ -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
diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
index 4a191fcbeb82..a47bf5f7562a 100644
--- a/tools/bpf/bpftool/main.c
+++ b/tools/bpf/bpftool/main.c
@@ -70,13 +70,35 @@  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 {
 		printf("%s v%s\n", bin_name, BPFTOOL_VERSION);
+		printf("features: libbfd=%s, skeletons=%s\n",
+		       has_libbfd ? "true" : "false",
+		       has_skeletons ? "true" : "false");
 	}
 	return 0;
 }