From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: David Ahern <dsahern@gmail.com>, bpf <bpf@vger.kernel.org>,
Network Development <netdev@vger.kernel.org>,
Daniel Borkmann <borkmann@iogearbox.net>,
Andrii Nakryiko <andrii.nakryiko@gmail.com>,
Lorenzo Bianconi <lorenzo@kernel.org>,
David Miller <davem@davemloft.net>
Subject: Re: [PATCH bpf-next V1] bpf: devmap dynamic map-value area based on BTF
Date: Fri, 5 Jun 2020 09:58:26 -0700 [thread overview]
Message-ID: <CAADnVQKWj_eoVE9XLqwEX2ZWB_yLwRtuQqY7EuFZSNZd40ukPQ@mail.gmail.com> (raw)
In-Reply-To: <20200605102323.15c2c06c@carbon>
On Fri, Jun 5, 2020 at 1:23 AM Jesper Dangaard Brouer <brouer@redhat.com> wrote:
>
> Great. If we can remove this requirement of -1 init (and let zero mean
> feature isn't used), then I'm all for exposing expose in uapi/bpf.h.
Not having it in bpf.h doesn't magically make it invisible.
It's uapi because user space C sources rely on its fixed format.
vmlinux.h contains all kernel types. both uapi and kernel internal.
devmap selftest taking uapi 'struct bpf_devmap_val' from vmlinux.h is
an awful hack.
I prefer to keep vmlinux.h usage to bpf programs only.
User space C code should interface with kernel via proper uapi headers.
When vmlinux.h is used by bpf C program it's completely different from
user space C code doing the same, because llvm emits relocations for
bpf prog and libbpf adjusts them.
So doing 'foo->bar' in bpf C is specific to target kernel, whereas
user C code 'foo->bar' is a hard constant which bakes it into uapi
that kernel has to keep backwards compatible.
If in some distant future we teach both gcc and clang to do bpf-style
relocations for x86 and teach ld.so to adjust them then we can dream
about very differently looking kernel/user interfaces.
Right now any struct used by user C code and passed into kernel is uapi.
next prev parent reply other threads:[~2020-06-05 16:58 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-03 15:44 [PATCH bpf-next V1] bpf: devmap dynamic map-value area based on BTF Jesper Dangaard Brouer
2020-06-03 16:22 ` Alexei Starovoitov
2020-06-04 15:48 ` Jesper Dangaard Brouer
2020-06-04 16:40 ` David Ahern
2020-06-04 17:33 ` Alexei Starovoitov
2020-06-05 8:23 ` Jesper Dangaard Brouer
2020-06-05 11:01 ` Toke Høiland-Jørgensen
2020-06-05 17:01 ` Alexei Starovoitov
2020-06-05 16:58 ` Alexei Starovoitov [this message]
2020-06-09 12:19 ` Jesper Dangaard Brouer
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=CAADnVQKWj_eoVE9XLqwEX2ZWB_yLwRtuQqY7EuFZSNZd40ukPQ@mail.gmail.com \
--to=alexei.starovoitov@gmail.com \
--cc=andrii.nakryiko@gmail.com \
--cc=borkmann@iogearbox.net \
--cc=bpf@vger.kernel.org \
--cc=brouer@redhat.com \
--cc=davem@davemloft.net \
--cc=dsahern@gmail.com \
--cc=lorenzo@kernel.org \
--cc=netdev@vger.kernel.org \
/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).