Re: [PATCH 3/3] samples: bpf: refactor BPF map in map test with libbpf

On Fri, Jun 26, 2020 at 1:18 AM Daniel T. Lee [off-list ref] wrote:

From commit 646f02ffdd49 ("libbpf: Add BTF-defined map-in-map
support"), a way to define internal map in BTF-defined map has been
added.

Instead of using previous 'inner_map_idx' definition, the structure to
be used for the inner map can be directly defined using array directive.

    __array(values, struct inner_map)

This commit refactors map in map test program with libbpf by explicitly
defining inner map with BTF-defined format.

Signed-off-by: Daniel T. Lee <redacted>
---

Thanks for the clean up, looks good except that prog NULL check.

It also seems like this is the last use of bpf_map_def_legacy, do you
mind removing it as well?

 samples/bpf/Makefile               |  2 +-
 samples/bpf/test_map_in_map_kern.c | 85 +++++++++++++++---------------
 samples/bpf/test_map_in_map_user.c | 53 +++++++++++++++++--
 3 files changed, 91 insertions(+), 49 deletions(-)

[...]

        snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+       obj = bpf_object__open_file(filename, NULL);
+       if (libbpf_get_error(obj)) {

this is right, but...

+               fprintf(stderr, "ERROR: opening BPF object file failed\n");
+               return 0;
+       }

-       if (load_bpf_file(filename)) {
-               printf("%s", bpf_log_buf);
-               return 1;
+       prog = bpf_object__find_program_by_name(obj, "trace_sys_connect");
+       if (libbpf_get_error(prog)) {

this is wrong. Just NULL check. libbpf APIs are not very consistent
with what they return, unfortunately.

+               printf("finding a prog in obj file failed\n");
+               goto cleanup;
+       }
+

[...]