[PATCH bpf-next 3/3] bpftool: Fix pretty print dump for maps without BTF loaded

[Jiri Olsa <jolsa@xxxxxxxxxx>]

The commit e5043894b21f ("bpftool: Use libbpf_get_error() to check
error") forced map dump with pretty print enabled to has BTF loaded,
which is not necessarily needed.

Keeping the libbpf_get_error call, but setting errno to 0 because
get_map_kv_btf does nothing for this case.

This fixes test_offload.py for me, which failed because of the
pretty print fails with:

   Test map dump...
   Traceback (most recent call last):
     File "/root/bpf-next/tools/testing/selftests/bpf/./test_offload.py", line 1251, in <module>
       _, entries = bpftool("map dump id %d" % (m["id"]))
     File "/root/bpf-next/tools/testing/selftests/bpf/./test_offload.py", line 169, in bpftool
       return tool("bpftool", args, {"json":"-p"}, JSON=JSON, ns=ns,
     File "/root/bpf-next/tools/testing/selftests/bpf/./test_offload.py", line 155, in tool
       ret, stdout = cmd(ns + name + " " + params + args,
     File "/root/bpf-next/tools/testing/selftests/bpf/./test_offload.py", line 109, in cmd
       return cmd_result(proc, include_stderr=include_stderr, fail=fail)
     File "/root/bpf-next/tools/testing/selftests/bpf/./test_offload.py", line 131, in cmd_result
       raise Exception("Command failed: %s\n%s" % (proc.args, stderr))
   Exception: Command failed: bpftool -p map dump id 4325

Fixes: e5043894b21f ("bpftool: Use libbpf_get_error() to check error")
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
 tools/bpf/bpftool/map.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index c66a3c979b7a..2ccf85042e75 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -862,6 +862,7 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
 	prev_key = NULL;
 
 	if (wtr) {
+		errno = 0;
 		btf = get_map_kv_btf(info);
 		err = libbpf_get_error(btf);
 		if (err) {
-- 
2.34.1