bpftool: Use print_entry_error() in case of ENOENT when dumping

Commit bf598a8f0f77 ("bpftool: Improve handling of ENOENT on map dumps")
used print_entry_plain() in case of ENOENT. However, that commit introduces
dead code. Per-cpu maps are zero-filled. When reading them, it's all or
nothing. There will never be a case where some cpus have an entry and
others don't.

The truth is that ENOENT is an error case. Use print_entry_error() to
output the desired message. That function's "value" parameter is also
renamed to indicate that we never use it for an actual map value.

The output format is unchanged.

Signed-off-by: Benjamin Poirier <bpoirier@suse.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 14 insertions, 19 deletions

diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index e96903078991..df958af56b6c 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -261,20 +261,20 @@ static void print_entry_json(struct bpf_map_info *info, unsigned char *key,
 }
 
 static void print_entry_error(struct bpf_map_info *info, unsigned char *key,
-                              const char *value)
+                              const char *error_msg)
 {
-        int value_size = strlen(value);
+        int msg_size = strlen(error_msg);
         bool single_line, break_names;
 
-        break_names = info->key_size > 16 || value_size > 16;
-        single_line = info->key_size + value_size <= 24 && !break_names;
+        break_names = info->key_size > 16 || msg_size > 16;
+        single_line = info->key_size + msg_size <= 24 && !break_names;
 
         printf("key:%c", break_names ? '\n' : ' ');
         fprint_hex(stdout, key, info->key_size, " ");
 
         printf(single_line ? "  " : "\n");
 
-        printf("value:%c%s", break_names ? '\n' : ' ', value);
+        printf("value:%c%s", break_names ? '\n' : ' ', error_msg);
 
         printf("\n");
 }
@@ -298,11 +298,7 @@ static void print_entry_plain(struct bpf_map_info *info, unsigned char *key,
 
                 if (info->value_size) {
                         printf("value:%c", break_names ? '\n' : ' ');
-                        if (value)
-                                fprint_hex(stdout, value, info->value_size,
-                                           " ");
-                        else
-                                printf("<no entry>");
+                        fprint_hex(stdout, value, info->value_size, " ");
                 }
 
                 printf("\n");
@@ -321,11 +317,8 @@ static void print_entry_plain(struct bpf_map_info *info, unsigned char *key,
                         for (i = 0; i < n; i++) {
                                 printf("value (CPU %02d):%c",
                                        i, info->value_size > 16 ? '\n' : ' ');
-                                if (value)
-                                        fprint_hex(stdout, value + i * step,
-                                                   info->value_size, " ");
-                                else
-                                        printf("<no entry>");
+                                fprint_hex(stdout, value + i * step,
+                                           info->value_size, " ");
                                 printf("\n");
                         }
                 }
@@ -722,11 +715,13 @@ static int dump_map_elem(int fd, void *key, void *value,
                 jsonw_string_field(json_wtr, "error", strerror(lookup_errno));
                 jsonw_end_object(json_wtr);
         } else {
+                const char *msg = NULL;
+
                 if (errno == ENOENT)
-                        print_entry_plain(map_info, key, NULL);
-                else
-                        print_entry_error(map_info, key,
-                                          strerror(lookup_errno));
+                        msg = "<no entry>";
+
+                print_entry_error(map_info, key,
+                                  msg ? : strerror(lookup_errno));
         }
 
         return 0;