On Tue, Mar 3, 2020 at 6:12 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
>
> hi,
> for bpftrace I'd like to print BTF functions (BTF_KIND_FUNC)
> declarations together with their names.
>
> I saw we have btf_dump__emit_type_decl and added BTF_KIND_FUNC,
> where it seemed to be missing, so it prints out something now
> (not sure it's the right fix though).
>
> Anyway, would you be ok with adding some flag/bool to struct
> btf_dump_emit_type_decl_opts, so I could get output like:
>
> kfunc:ksys_readahead(int fd, long long int offset, long unsigned int count) = ssize_t
> kfunc:ksys_read(unsigned int fd, char buf, long unsigned int count) = size_t
>
> ... to be able to the arguments and return type separated,
> so I could easily get to something like above?
>
> Current interface is just vfprintf callback and I'm not sure
> I can rely that it will allywas be called with same arguments,
> like having separated calls for parsed atoms like 'return type',
> '(', ')', '(', 'arg type', 'arg name', ...
>
> I'm open to any suggestion ;-)
Hey Jiri!
Can you please elaborate on the use case and problem you are trying to solve?
I think we can (and probably even should) add such option and support
to dump functions, but whatever we do it should be a valid C syntax
and should be compilable.
Example above:
kfunc:ksys_read(unsigned int fd, char buf, long unsigned int count) = size_t
Is this really the syntax you need to get? I think btf_dump, when
(optionally) emitting function declaration, will have to emit that
particular one as:
size_t ksys_read(unsigned int fd, char buf, long unsigned int count);
But I'd like to hear the use case before we add this. Thanks!
>
> thanks,
> jirka
>
>
> ---
> tools/lib/bpf/btf_dump.c | 4 ++++
> .../selftests/bpf/prog_tests/btf_dump.c | 21 +++++++++++++++++++
> .../bpf/progs/btf_dump_test_case_bitfields.c | 10 +++++++++
> .../bpf/progs/btf_dump_test_case_multidim.c | 3 +++
> .../progs/btf_dump_test_case_namespacing.c | 19 +++++++++++++++++
> .../bpf/progs/btf_dump_test_case_ordering.c | 3 +++
> .../bpf/progs/btf_dump_test_case_packing.c | 16 ++++++++++++++
> .../bpf/progs/btf_dump_test_case_padding.c | 15 +++++++++++++
> .../bpf/progs/btf_dump_test_case_syntax.c | 3 +++
> 9 files changed, 94 insertions(+)
>
[...]
>
> +/*
> + *int ()(struct {
> + * struct packed_trailing_space _1;
> + * short: 16;
> + * struct non_packed_trailing_space _2;
> + * struct packed_fields _3;
> + * short: 16;
> + * struct non_packed_fields _4;
> + * struct nested_packed _5;
> + * short: 16;
> + * union union_is_never_packed _6;
> + * union union_does_not_need_packing _7;
> + * union jump_code_union _8;
> + * int: 24;
> + *} __attribute__((packed)) *_)
> + */
This clearly isn't compilable, right?
> /*------ END-EXPECTED-OUTPUT ------ */
>
> int f(struct {
> diff --git a/tools/testing/selftests/bpf/progs/btf_dump_test_case_padding.c b/tools/testing/selftests/bpf/progs/btf_dump_test_case_padding.c
> index 35c512818a56..581349bb0c2f 100644
> --- a/tools/testing/selftests/bpf/progs/btf_dump_test_case_padding.c
> +++ b/tools/testing/selftests/bpf/progs/btf_dump_test_case_padding.c
> @@ -102,6 +102,21 @@ struct zone {
> struct zone_padding __pad__;
> };
>
[...]
