bpf.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Yonghong Song <yhs@fb.com>
Cc: Andrii Nakryiko <andriin@fb.com>, bpf <bpf@vger.kernel.org>,
	Martin KaFai Lau <kafai@fb.com>,
	Network Development <netdev@vger.kernel.org>,
	Alexei Starovoitov <ast@fb.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Kernel Team <kernel-team@fb.com>
Subject: Re: [PATCH bpf-next v4 12/21] bpf: add PTR_TO_BTF_ID_OR_NULL support
Date: Sun, 10 May 2020 09:11:21 -0700	[thread overview]
Message-ID: <CAADnVQKzhbFe4MQ0G4ZuPnjXbbzEfQMjvTwba4MkhyXQAuNP+Q@mail.gmail.com> (raw)
In-Reply-To: <d5b04ac9-3e3c-3e32-4058-afc29e3d34ce@fb.com>

On Sat, May 9, 2020 at 10:19 PM Yonghong Song <yhs@fb.com> wrote:
>
>
>
> On 5/9/20 5:50 PM, Alexei Starovoitov wrote:
> > On Sat, May 09, 2020 at 10:59:12AM -0700, Yonghong Song wrote:
> >> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> >> index a2cfba89a8e1..c490fbde22d4 100644
> >> --- a/kernel/bpf/btf.c
> >> +++ b/kernel/bpf/btf.c
> >> @@ -3790,7 +3790,10 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
> >>              return true;
> >>
> >>      /* this is a pointer to another type */
> >> -    info->reg_type = PTR_TO_BTF_ID;
> >> +    if (off != 0 && prog->aux->btf_id_or_null_non0_off)
> >> +            info->reg_type = PTR_TO_BTF_ID_OR_NULL;
> >> +    else
> >> +            info->reg_type = PTR_TO_BTF_ID;
> >
> > I think the verifier should be smarter than this.
> > It's too specific and inflexible. All ctx fields of bpf_iter execpt first
> > will be such ? let's figure out a different way to tell verifier about this.
> > How about using typedef with specific suffix? Like:
> > typedef struct bpf_map *bpf_map_or_null;
> >   struct bpf_iter__bpf_map {
> >     struct bpf_iter_meta *meta;
> >     bpf_map_or_null map;
> >   };
> > or use a union with specific second member? Like:
> >   struct bpf_iter__bpf_map {
> >     struct bpf_iter_meta *meta;
> >     union {
> >       struct bpf_map *map;
> >       long null;
> >     };
> >   };
>
> I have an alternative approach to refactor this for future
> support for map elements as well.
>
> For example, for bpf_map_elements iterator the prog context type
> can be
>      struct bpf_iter_bpf_map_elem {
>         struct bpf_iter_meta *meta;
>         strruct bpf_map *map;
>         <key type>  *key;
>         <value type> *val;
>     };
>
> target will pass the following information to bpf_iter registration:
>     arg 1: PTR_TO_BTF_ID
>     arg 2: PTR_TO_BTF_ID_OR_NULL
>     arg 3: PTR_TO_BUFFER
>     arg 4: PTR_TO_BUFFER
>
> verifier will retrieve the reg_type from target.

you mean to introduce something like 'struct bpf_func_proto'
that describes types of helpers, but instead something similar
to clarify the types in ctx ? That should work. Thanks

  reply	other threads:[~2020-05-10 16:11 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-09 17:58 [PATCH bpf-next v4 00/21] bpf: implement bpf iterator for kernel data Yonghong Song
2020-05-09 17:58 ` [PATCH bpf-next v4 01/21] bpf: implement an interface to register bpf_iter targets Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 02/21] bpf: allow loading of a bpf_iter program Yonghong Song
2020-05-10  0:41   ` Alexei Starovoitov
2020-05-10  5:07     ` Yonghong Song
2020-05-12 15:41     ` Yonghong Song
2020-05-12 16:25       ` Alexei Starovoitov
2020-05-12 16:29         ` Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 03/21] bpf: support bpf tracing/iter programs for BPF_LINK_CREATE Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 04/21] bpf: support bpf tracing/iter programs for BPF_LINK_UPDATE Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 05/21] bpf: implement bpf_seq_read() for bpf iterator Yonghong Song
2020-05-10  0:30   ` Alexei Starovoitov
2020-05-10  4:51     ` Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 06/21] bpf: create anonymous " Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 07/21] bpf: create file " Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 08/21] bpf: implement common macros/helpers for target iterators Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 09/21] bpf: add bpf_map iterator Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 10/21] net: bpf: add netlink and ipv6_route bpf_iter targets Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 11/21] bpf: add task and task/file iterator targets Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 12/21] bpf: add PTR_TO_BTF_ID_OR_NULL support Yonghong Song
2020-05-10  0:50   ` Alexei Starovoitov
2020-05-10  5:18     ` Yonghong Song
2020-05-10 16:11       ` Alexei Starovoitov [this message]
2020-05-10 17:05         ` Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 13/21] bpf: add bpf_seq_printf and bpf_seq_write helpers Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 14/21] bpf: handle spilled PTR_TO_BTF_ID properly when checking stack_boundary Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 15/21] bpf: support variable length array in tracing programs Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 16/21] tools/libbpf: add bpf_iter support Yonghong Song
2020-05-10  0:35   ` Alexei Starovoitov
2020-05-10  5:06     ` Yonghong Song
2020-05-10 16:09       ` Alexei Starovoitov
2020-05-10 17:04         ` Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 17/21] tools/libpf: add offsetof/container_of macro in bpf_helpers.h Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 18/21] tools/bpftool: add bpf_iter support for bptool Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 19/21] tools/bpf: selftests: add iterator programs for ipv6_route and netlink Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 20/21] tools/bpf: selftests: add iter progs for bpf_map/task/task_file Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 21/21] tools/bpf: selftests: add bpf_iter selftests Yonghong Song
2020-05-10  0:34   ` Alexei Starovoitov
2020-05-10  5:01     ` Yonghong Song
2020-05-10 16:14       ` Alexei Starovoitov
2020-05-10  0:27 ` [PATCH bpf-next v4 00/21] bpf: implement bpf iterator for kernel data Alexei Starovoitov
2020-05-10  4:47   ` Yonghong Song

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CAADnVQKzhbFe4MQ0G4ZuPnjXbbzEfQMjvTwba4MkhyXQAuNP+Q@mail.gmail.com \
    --to=alexei.starovoitov@gmail.com \
    --cc=andriin@fb.com \
    --cc=ast@fb.com \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=kafai@fb.com \
    --cc=kernel-team@fb.com \
    --cc=netdev@vger.kernel.org \
    --cc=yhs@fb.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).