On Thu, Nov 10, 2022 at 6:43 AM Eduard Zingerman <eddyz87@xxxxxxxxx> wrote:
>
> Covers the following cases:
> - `__atribute__((btf_decl_tag("...")))` could be applied to structs
> and unions;
> - decl tag applied to an empty struct is printed on a single line;
> - decl tags with the same name could be applied to several structs;
> - several decl tags could be applied to the same struct;
> - attribute `packed` works fine with decl tags (it is a separate
> branch in `tools/lib/bpf/btf_dump.c:btf_dump_emit_attributes`;
> - decl tag could be attached to typedef;
> - decl tag could be attached to a struct field;
> - decl tag could be attached to a struct field and a struct itself
> simultaneously;
> - decl tag could be attached to a global variable;
> - decl tag could be attached to a func proto parameter;
> - btf__add_decl_tag could be interleaved with btf_dump__dump_type calls.
>
> Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
> ---
> .../selftests/bpf/prog_tests/btf_dump.c | 79 +++++++++++++++++++
> .../bpf/progs/btf_dump_test_case_decl_tag.c | 65 +++++++++++++++
> 2 files changed, 144 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/progs/btf_dump_test_case_decl_tag.c
>
[...]
> + /* First, BTF corresponding to the following C code:
> + *
> + * typedef void (*fn)(int a __btf_decl_tag("a_tag"));
> + *
> + */
> + id = btf__add_int(btf, "int", 4, BTF_INT_SIGNED);
> + ASSERT_EQ(id, 1, "int_id");
> + id = btf__add_func_proto(btf, 0);
> + ASSERT_EQ(id, 2, "func_proto_id");
> + err = btf__add_func_param(btf, "a", 1);
> + ASSERT_OK(err, "func_param_ok");
> + id = btf__add_decl_tag(btf, "a_tag", 2, 0);
> + ASSERT_EQ(id, 3, "decl_tag_a");
> + id = btf__add_ptr(btf, 2);
> + ASSERT_EQ(id, 4, "proto_ptr");
> + id = btf__add_typedef(btf, "fn", 4);
> + ASSERT_EQ(id, 5, "typedef");
can you please also add decl_tag for func_proto itself (comp_idx == -1)
> +
> + err = btf_dump_all_types(btf, d);
> + ASSERT_OK(err, "btf_dump_all_types #1");
> + fflush(dump_buf_file);
> + dump_buf[dump_buf_sz] = 0; /* some libc implementations don't do this */
> +
> + ASSERT_STREQ(dump_buf,
> + "#if __has_attribute(btf_decl_tag)\n"
> + "#define __btf_decl_tag(x) __attribute__((btf_decl_tag(x)))\n"
> + "#else\n"
> + "#define __btf_decl_tag(x)\n"
> + "#endif\n"
> + "\n"
> + "typedef void (*fn)(int a __btf_decl_tag(\"a_tag\"));\n\n",
> + "decl tags for fn");
> +
[...]
> +struct tag_on_field_and_struct {
> + int x __btf_decl_tag("t1");
> +} __btf_decl_tag("t2");
> +
> +struct root_struct {
> + struct empty_with_tag a;
> + struct one_tag b;
> + struct same_tag c;
> + struct two_tags d;
> + struct packed e;
> + td_with_tag f;
> + struct tags_on_fields g;
> + struct tag_on_field_and_struct h;
> +};
> +
> +SEC(".data") int global_var __btf_decl_tag("var_tag") = (int)777;
do you need explicit SEC(".data")? I'd expect global_var is put into
.data anyways. If it's about __attribute__((unused)), then we can do
that more explicitly here instead of through SEC()? Or just make sure
global_var is used in f() internally
> +
> +/* ------ END-EXPECTED-OUTPUT ------ */
> +
> +int f(struct root_struct *s)
> +{
> + return 0;
> +}
> --
> 2.34.1
>
