bpftool: Fix missing BTF output for json during map dump

The btf availability check is only done for plain text output.
It causes the whole BTF output went missing when json_output
is used.

This patch simplifies the logic a little by avoiding passing "int btf" to
map_dump().

For plain text output, the btf_wtr is only created when the map has
BTF (i.e. info->btf_id != 0).  The nullness of "json_writer_t *wtr"
in map_dump() alone can decide if dumping BTF output is needed.
As long as wtr is not NULL, map_dump() will print out the BTF-described
data whenever a map has BTF available (i.e. info->btf_id != 0)
regardless of json or plain-text output.

In do_dump(), the "int btf" is also renamed to "int do_plain_btf".

Fixes: f371215a1ed1 ("bpftool: Match maps by name")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Cc: Paul Chaignon <paul.chaignon@orange.com>
Link: https://lore.kernel.org/bpf/20200115230025.1101828-1-kafai@fb.com

diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index e00e9e19d6b7928e96b77de8700cc00017c2dfd2..45c1eda6512cdb4cc3c9198810e4e547e28a0e66 100644 (file)
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -933,7 +933,7 @@ static int maps_have_btf(int *fds, int nb_fds)
 
 static int
 map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
-        bool enable_btf, bool show_header)
+        bool show_header)
 {
        void *key, *value, *prev_key;
        unsigned int num_elems = 0;
@@ -950,18 +950,16 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
 
        prev_key = NULL;
 
-       if (enable_btf) {
-               err = btf__get_from_id(info->btf_id, &btf);
-               if (err || !btf) {
-                       /* enable_btf is true only if we've already checked
-                        * that all maps have BTF information.
-                        */
-                       p_err("failed to get btf");
-                       goto exit_free;
+       if (wtr) {
+               if (info->btf_id) {
+                       err = btf__get_from_id(info->btf_id, &btf);
+                       if (err || !btf) {
+                               err = err ? : -ESRCH;
+                               p_err("failed to get btf");
+                               goto exit_free;
+                       }
                }
-       }
 
-       if (wtr) {
                if (show_header) {
                        jsonw_start_object(wtr);        /* map object */
                        show_map_header_json(info, wtr);
@@ -1009,7 +1007,7 @@ static int do_dump(int argc, char **argv)
 {
        json_writer_t *wtr = NULL, *btf_wtr = NULL;
        struct bpf_map_info info = {};
-       int nb_fds, i = 0, btf = 0;
+       int nb_fds, i = 0;
        __u32 len = sizeof(info);
        int *fds = NULL;
        int err = -1;
@@ -1029,17 +1027,17 @@ static int do_dump(int argc, char **argv)
        if (json_output) {
                wtr = json_wtr;
        } else {
-               btf = maps_have_btf(fds, nb_fds);
-               if (btf < 0)
+               int do_plain_btf;
+
+               do_plain_btf = maps_have_btf(fds, nb_fds);
+               if (do_plain_btf < 0)
                        goto exit_close;
-               if (btf) {
+
+               if (do_plain_btf) {
                        btf_wtr = get_btf_writer();
-                       if (btf_wtr) {
-                               wtr = btf_wtr;
-                       } else {
+                       wtr = btf_wtr;
+                       if (!btf_wtr)
                                p_info("failed to create json writer for btf. falling back to plain output");
-                               btf = 0;
-                       }
                }
        }
 
@@ -1050,7 +1048,7 @@ static int do_dump(int argc, char **argv)
                        p_err("can't get map info: %s", strerror(errno));
                        break;
                }
-               err = map_dump(fds[i], &info, wtr, btf, nb_fds > 1);
+               err = map_dump(fds[i], &info, wtr, nb_fds > 1);
                if (!wtr && i != nb_fds - 1)
                        printf("\n");
 
@@ -1061,7 +1059,7 @@ static int do_dump(int argc, char **argv)
        if (wtr && nb_fds > 1)
                jsonw_end_array(wtr);   /* root array */
 
-       if (btf)
+       if (btf_wtr)
                jsonw_destroy(&btf_wtr);
 exit_close:
        for (; i < nb_fds; i++)