new file mode 100644
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include <test_progs.h>
+#include "tag.skel.h"
+
+void test_btf_tag(void)
+{
+ struct tag *skel;
+
+ skel = tag__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "btf_tag"))
+ return;
+ tag__destroy(skel);
+}
new file mode 100644
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+#define __tag1 __attribute__((btf_tag("tag1")))
+#define __tag2 __attribute__((btf_tag("tag2")))
+
+struct key_t {
+ int a;
+ int b __tag1 __tag2;
+ int c;
+} __tag1 __tag2;
+
+struct {
+ __uint(type, BPF_MAP_TYPE_HASH);
+ __uint(max_entries, 3);
+ __type(key, struct key_t);
+ __type(value, __u64);
+} hashmap1 SEC(".maps");
+
+__u32 total __tag1 __tag2 = 0;
+
+static __noinline int foo(int x __tag1 __tag2) __tag1 __tag2
+{
+ struct key_t key;
+ __u64 val = 1;
+
+ key.a = key.b = key.c = x;
+ bpf_map_update_elem(&hashmap1, &key, &val, 0);
+ return 0;
+}
+
+SEC("fentry/bpf_fentry_test1")
+int BPF_PROG(sub, int x)
+{
+ return foo(x);
+}
Add a bpf program with btf_tag attributes. The program is loaded successfully with the kernel. With the command bpftool btf dump file ./tag.o the following dump shows that tags are properly encoded: [8] STRUCT 'key_t' size=12 vlen=3 'a' type_id=2 bits_offset=0 'b' type_id=2 bits_offset=32 'c' type_id=2 bits_offset=64 [9] TAG 'tag1' type_id=8 component_id=-1 [10] TAG 'tag2' type_id=8 component_id=-1 [11] TAG 'tag1' type_id=8 component_id=1 [12] TAG 'tag2' type_id=8 component_id=1 ... [21] FUNC_PROTO '(anon)' ret_type_id=2 vlen=1 'x' type_id=2 [22] FUNC 'foo' type_id=21 linkage=static [23] TAG 'tag1' type_id=22 component_id=0 [24] TAG 'tag2' type_id=22 component_id=0 [25] TAG 'tag1' type_id=22 component_id=-1 [26] TAG 'tag2' type_id=22 component_id=-1 ... [29] VAR 'total' type_id=27, linkage=global [30] TAG 'tag1' type_id=29 component_id=-1 [31] TAG 'tag2' type_id=29 component_id=-1 If an old clang compiler, which does not support btf_tag attribute, is used, these btf_tag attributes will be silently ignored. Acked-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Yonghong Song <yhs@fb.com> --- .../selftests/bpf/prog_tests/btf_tag.c | 14 +++++++ tools/testing/selftests/bpf/progs/tag.c | 39 +++++++++++++++++++ 2 files changed, 53 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/btf_tag.c create mode 100644 tools/testing/selftests/bpf/progs/tag.c