From: Yonghong Song <yhs@fb.com>
Date: Tue, 14 Sep 2021 15:30:31 -0700
Subject: bpftool: Add support for BTF_KIND_TAG
Patch-mainline: v5.16-rc1
Git-commit: 5c07f2fec00361fb5e8cff8ba7fdede7b29f38bd
References: jsc#PED-1377

Added bpftool support to dump BTF_KIND_TAG information.
The new bpftool will be used in later patches to dump
btf in the test bpf program object file.

Currently, the tags are not emitted with
  bpftool btf dump file <path> format c
and they are silently ignored.  The tag information is
mostly used in the kernel for verification purpose and the kernel
uses its own btf to check. With adding these tags
to vmlinux.h, tags will be encoded in program's btf but
they will not be used by the kernel, at least for now.
So let us delay adding these tags to format C header files
until there is a real need.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210914223031.246951-1-yhs@fb.com
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 tools/bpf/bpftool/btf.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

--- a/tools/bpf/bpftool/btf.c
+++ b/tools/bpf/bpftool/btf.c
@@ -37,6 +37,7 @@ static const char * const btf_kind_str[N
 	[BTF_KIND_VAR]		= "VAR",
 	[BTF_KIND_DATASEC]	= "DATASEC",
 	[BTF_KIND_FLOAT]	= "FLOAT",
+	[BTF_KIND_TAG]		= "TAG",
 };
 
 struct btf_attach_table {
@@ -347,6 +348,17 @@ static int dump_btf_type(const struct bt
 			printf(" size=%u", t->size);
 		break;
 	}
+	case BTF_KIND_TAG: {
+		const struct btf_tag *tag = (const void *)(t + 1);
+
+		if (json_output) {
+			jsonw_uint_field(w, "type_id", t->type);
+			jsonw_int_field(w, "component_idx", tag->component_idx);
+		} else {
+			printf(" type_id=%u component_idx=%d", t->type, tag->component_idx);
+		}
+		break;
+	}
 	default:
 		break;
 	}