netdev - [PATCH v3 bpf-next 1/4] bpftool: Print the enum's name instead of value

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Date:   Tue, 17 Mar 2020 20:14:37 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     <bpf@...r.kernel.org>
CC:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, <kernel-team@...com>,
        <netdev@...r.kernel.org>
Subject: [PATCH v3 bpf-next 1/4] bpftool: Print the enum's name instead of value

This patch prints the enum's name if there is one found in
the array of btf_enum.

The commit 9eea98497951 ("bpf: fix BTF verification of enums")
has details about an enum could have any power-of-2 size (up to 8 bytes).
This patch also takes this chance to accommodate these non 4 byte
enums.

Acked-by: Quentin Monnet <quentin@...valent.com>
Signed-off-by: Martin KaFai Lau <kafai@...com>
---
 tools/bpf/bpftool/btf_dumper.c | 39 +++++++++++++++++++++++++++++++---
 1 file changed, 36 insertions(+), 3 deletions(-)

diff --git a/tools/bpf/bpftool/btf_dumper.c b/tools/bpf/bpftool/btf_dumper.c
index 01cc52b834fa..079f9171b1a3 100644
--- a/tools/bpf/bpftool/btf_dumper.c
+++ b/tools/bpf/bpftool/btf_dumper.c
@@ -43,9 +43,42 @@ static int btf_dumper_modifier(const struct btf_dumper *d, __u32 type_id,
 	return btf_dumper_do_type(d, actual_type_id, bit_offset, data);
 }
 
-static void btf_dumper_enum(const void *data, json_writer_t *jw)
+static void btf_dumper_enum(const struct btf_dumper *d,
+			    const struct btf_type *t,
+			    const void *data)
 {
-	jsonw_printf(jw, "%d", *(int *)data);
+	const struct btf_enum *enums = btf_enum(t);
+	__s64 value;
+	__u16 i;
+
+	switch (t->size) {
+	case 8:
+		value = *(__s64 *)data;
+		break;
+	case 4:
+		value = *(__s32 *)data;
+		break;
+	case 2:
+		value = *(__s16 *)data;
+		break;
+	case 1:
+		value = *(__s8 *)data;
+		break;
+	default:
+		jsonw_string(d->jw, "<invalid_enum_size>");
+		return;
+	}
+
+	for (i = 0; i < btf_vlen(t); i++) {
+		if (value == enums[i].val) {
+			jsonw_string(d->jw,
+				     btf__name_by_offset(d->btf,
+							 enums[i].name_off));
+			return;
+		}
+	}
+
+	jsonw_int(d->jw, value);
 }
 
 static int btf_dumper_array(const struct btf_dumper *d, __u32 type_id,
@@ -366,7 +399,7 @@ static int btf_dumper_do_type(const struct btf_dumper *d, __u32 type_id,
 	case BTF_KIND_ARRAY:
 		return btf_dumper_array(d, type_id, data);
 	case BTF_KIND_ENUM:
-		btf_dumper_enum(data, d->jw);
+		btf_dumper_enum(d, t, data);
 		return 0;
 	case BTF_KIND_PTR:
 		btf_dumper_ptr(data, d->jw, d->is_plain_text);
-- 
2.17.1