Commit
c240ba287890 ("selftests/bpf: Add a test with a bpf
program with btf_tag attributes") added btf_tag selftest
to test BTF_KIND_TAG generation from C source code, and to
test kernel validation of generated BTF types.
But if an old clang (clang 13 or earlier) is used, the
following compiler warning may be seen:
progs/tag.c:23:20: warning: unknown attribute 'btf_tag' ignored
and the test itself is marked OK. The compiler warning is bad
and the test itself shouldn't be marked OK.
This patch added the check for btf_tag attribute support.
If btf_tag is not supported by the clang, the attribute will
not be used in the code and the test will be marked as skipped.
For example, with clang 13:
./test_progs -t btf_tag
#21 btf_tag:SKIP
Summary: 1/0 PASSED, 1 SKIPPED, 0 FAILED
The selftests/README.rst is updated to clarify when the btf_tag
test may be skipped.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210915061036.2577971-1-yhs@fb.com
__ https://reviews.llvm.org/D93563
+btf_tag test and Clang version
+==============================
+
+The btf_tag selftest require LLVM support to recognize the btf_tag attribute.
+It was introduced in `Clang 14`__.
+
+Without it, the btf_tag selftest will be skipped and you will observe:
+
+.. code-block:: console
+
+ #<test_num> btf_tag:SKIP
+
+__ https://reviews.llvm.org/D106614
+
Clang dependencies for static linking tests
===========================================
skel = tag__open_and_load();
if (!ASSERT_OK_PTR(skel, "btf_tag"))
return;
+
+ if (skel->rodata->skip_tests) {
+ printf("%s:SKIP: btf_tag attribute not supported", __func__);
+ test__skip();
+ }
+
tag__destroy(skel);
}
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
+#ifndef __has_attribute
+#define __has_attribute(x) 0
+#endif
+
+#if __has_attribute(btf_tag)
#define __tag1 __attribute__((btf_tag("tag1")))
#define __tag2 __attribute__((btf_tag("tag2")))
+volatile const bool skip_tests __tag1 __tag2 = false;
+#else
+#define __tag1
+#define __tag2
+volatile const bool skip_tests = true;
+#endif
struct key_t {
int a;
__type(value, __u64);
} hashmap1 SEC(".maps");
-__u32 total __tag1 __tag2 = 0;
static __noinline int foo(int x __tag1 __tag2) __tag1 __tag2
{