bpftool: Add "bootstrap" feature to version output

Along with the version number, "bpftool version" displays a list of
features that were selected at compilation time for bpftool. It would be
useful to indicate in that list whether a binary is a bootstrap version
of bpftool. Given that an increasing number of components rely on
bootstrap versions for generating skeletons, this could help understand
what a binary is capable of if it has been copied outside of the usual
"bootstrap" directory.

To detect a bootstrap version, we simply rely on the absence of
implementation for the do_prog() function. To do this, we must move the
(unchanged) list of commands before do_version(), which in turn requires
renaming this "cmds" array to avoid shadowing it with the "cmds"
argument in cmd_select().

Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20221020100332.69563-1-quentin@isovalent.com

diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
index 8bf3615..b22223d 100644 (file)
--- a/tools/bpf/bpftool/main.c
+++ b/tools/bpf/bpftool/main.c
@@ -71,6 +71,27 @@ static int do_help(int argc, char **argv)
        return 0;
 }
 
+static int do_batch(int argc, char **argv);
+static int do_version(int argc, char **argv);
+
+static const struct cmd commands[] = {
+       { "help",       do_help },
+       { "batch",      do_batch },
+       { "prog",       do_prog },
+       { "map",        do_map },
+       { "link",       do_link },
+       { "cgroup",     do_cgroup },
+       { "perf",       do_perf },
+       { "net",        do_net },
+       { "feature",    do_feature },
+       { "btf",        do_btf },
+       { "gen",        do_gen },
+       { "struct_ops", do_struct_ops },
+       { "iter",       do_iter },
+       { "version",    do_version },
+       { 0 }
+};
+
 #ifndef BPFTOOL_VERSION
 /* bpftool's major and minor version numbers are aligned on libbpf's. There is
  * an offset of 6 for the version number, because bpftool's version was higher
@@ -82,6 +103,15 @@ static int do_help(int argc, char **argv)
 #define BPFTOOL_PATCH_VERSION 0
 #endif
 
+static void
+print_feature(const char *feature, bool state, unsigned int *nb_features)
+{
+       if (state) {
+               printf("%s %s", *nb_features ? "," : "", feature);
+               *nb_features = *nb_features + 1;
+       }
+}
+
 static int do_version(int argc, char **argv)
 {
 #ifdef HAVE_LIBBFD_SUPPORT
@@ -94,6 +124,18 @@ static int do_version(int argc, char **argv)
 #else
        const bool has_skeletons = true;
 #endif
+       bool bootstrap = false;
+       int i;
+
+       for (i = 0; commands[i].cmd; i++) {
+               if (!strcmp(commands[i].cmd, "prog")) {
+                       /* Assume we run a bootstrap version if "bpftool prog"
+                        * is not available.
+                        */
+                       bootstrap = !commands[i].func;
+                       break;
+               }
+       }
 
        if (json_output) {
                jsonw_start_object(json_wtr);   /* root object */
@@ -114,6 +156,7 @@ static int do_version(int argc, char **argv)
                jsonw_bool_field(json_wtr, "libbfd", has_libbfd);
                jsonw_bool_field(json_wtr, "libbpf_strict", !legacy_libbpf);
                jsonw_bool_field(json_wtr, "skeletons", has_skeletons);
+               jsonw_bool_field(json_wtr, "bootstrap", bootstrap);
                jsonw_end_object(json_wtr);     /* features */
 
                jsonw_end_object(json_wtr);     /* root object */
@@ -128,16 +171,10 @@ static int do_version(int argc, char **argv)
 #endif
                printf("using libbpf %s\n", libbpf_version_string());
                printf("features:");
-               if (has_libbfd) {
-                       printf(" libbfd");
-                       nb_features++;
-               }
-               if (!legacy_libbpf) {
-                       printf("%s libbpf_strict", nb_features++ ? "," : "");
-                       nb_features++;
-               }
-               if (has_skeletons)
-                       printf("%s skeletons", nb_features++ ? "," : "");
+               print_feature("libbfd", has_libbfd, &nb_features);
+               print_feature("libbpf_strict", !legacy_libbpf, &nb_features);
+               print_feature("skeletons", has_skeletons, &nb_features);
+               print_feature("bootstrap", bootstrap, &nb_features);
                printf("\n");
        }
        return 0;
@@ -279,26 +316,6 @@ static int make_args(char *line, char *n_argv[], int maxargs, int cmd_nb)
        return n_argc;
 }
 
-static int do_batch(int argc, char **argv);
-
-static const struct cmd cmds[] = {
-       { "help",       do_help },
-       { "batch",      do_batch },
-       { "prog",       do_prog },
-       { "map",        do_map },
-       { "link",       do_link },
-       { "cgroup",     do_cgroup },
-       { "perf",       do_perf },
-       { "net",        do_net },
-       { "feature",    do_feature },
-       { "btf",        do_btf },
-       { "gen",        do_gen },
-       { "struct_ops", do_struct_ops },
-       { "iter",       do_iter },
-       { "version",    do_version },
-       { 0 }
-};
-
 static int do_batch(int argc, char **argv)
 {
        char buf[BATCH_LINE_LEN_MAX], contline[BATCH_LINE_LEN_MAX];
@@ -386,7 +403,7 @@ static int do_batch(int argc, char **argv)
                        jsonw_name(json_wtr, "output");
                }
 
-               err = cmd_select(cmds, n_argc, n_argv, do_help);
+               err = cmd_select(commands, n_argc, n_argv, do_help);
 
                if (json_output)
                        jsonw_end_object(json_wtr);
@@ -528,7 +545,7 @@ int main(int argc, char **argv)
        if (version_requested)
                return do_version(argc, argv);
 
-       ret = cmd_select(cmds, argc, argv, do_help);
+       ret = cmd_select(commands, argc, argv, do_help);
 
        if (json_output)
                jsonw_destroy(&json_wtr);