[PATCH v3 bpf-next 1/2] bpftool: Use print_entry_error() in case of ENOENT when dumping

[Benjamin Poirier]

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 <bpoir...@suse.com>
---
 tools/bpf/bpftool/map.c | 33 ++++++++++++++-------------------
 1 file 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;
-- 
2.21.0