From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: David Ahern <dsahern@gmail.com>, bpf <bpf@vger.kernel.org>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Networking <netdev@vger.kernel.org>,
Daniel Borkmann <borkmann@iogearbox.net>,
Lorenzo Bianconi <lorenzo@kernel.org>
Subject: Re: [PATCH bpf 1/3] bpf: syscall to start at file-descriptor 1
Date: Mon, 8 Jun 2020 11:36:33 -0700 [thread overview]
Message-ID: <CAEf4BzagW8GFfybMf10yorwTA+fpiuZHqT41Uu-vAsRHnZqKRw@mail.gmail.com> (raw)
In-Reply-To: <159163507753.1967373.62249862728421448.stgit@firesoul>
On Mon, Jun 8, 2020 at 9:51 AM Jesper Dangaard Brouer <brouer@redhat.com> wrote:
>
> This patch change BPF syscall to avoid returning file descriptor value zero.
>
> As mentioned in cover letter, it is very impractical when extending kABI
> that the file-descriptor value 'zero' is valid, as this requires new fields
> must be initialised as minus-1. First step is to change the kernel such that
> BPF-syscall simply doesn't return value zero as a FD number.
>
> This patch achieves this by similar code to anon_inode_getfd(), with the
> exception of getting unused FD starting from 1. The kernel already supports
> starting from a specific FD value, as this is used by f_dupfd(). It seems
> simpler to replicate part of anon_inode_getfd() code and use this start from
> offset feature, instead of using f_dupfd() handling afterwards.
Wouldn't it be better to just handle that on libbpf side? That way it
works on all kernels and doesn't require this duplication of logic
inside kernel?
>
> Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
> ---
> fs/file.c | 2 +-
> include/linux/file.h | 1 +
> kernel/bpf/syscall.c | 38 ++++++++++++++++++++++++++++++++------
> 3 files changed, 34 insertions(+), 7 deletions(-)
>
[...]
next prev parent reply other threads:[~2020-06-08 18:36 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-08 16:51 [PATCH bpf 0/3] bpf: avoid using/returning file descriptor value zero Jesper Dangaard Brouer
2020-06-08 16:51 ` [PATCH bpf 1/3] bpf: syscall to start at file-descriptor 1 Jesper Dangaard Brouer
2020-06-08 18:28 ` Toke Høiland-Jørgensen
2020-06-08 18:36 ` Andrii Nakryiko [this message]
2020-06-08 19:44 ` Jesper Dangaard Brouer
2020-06-08 20:05 ` Andrii Nakryiko
2020-06-08 19:00 ` kernel test robot
2020-06-08 19:55 ` kernel test robot
2020-06-08 19:55 ` [RFC PATCH] bpf: bpf_anon_inode_getfd() can be static kernel test robot
2020-06-08 20:42 ` [PATCH bpf 1/3] bpf: syscall to start at file-descriptor 1 kernel test robot
2020-06-08 16:51 ` [PATCH bpf 2/3] bpf: devmap adjust uapi for attach bpf program Jesper Dangaard Brouer
2020-06-08 18:30 ` Toke Høiland-Jørgensen
2020-06-08 16:51 ` [PATCH bpf 3/3] bpf: selftests and tools use struct bpf_devmap_val from uapi Jesper Dangaard Brouer
2020-06-09 1:34 ` [PATCH bpf 0/3] bpf: avoid using/returning file descriptor value zero Alexei Starovoitov
2020-06-09 9:55 ` Jesper Dangaard Brouer
2020-06-09 13:31 ` [PATCH bpf V2 0/2] bpf: adjust uapi for devmap prior to kernel release Jesper Dangaard Brouer
2020-06-09 13:31 ` [PATCH bpf V2 1/2] bpf: devmap adjust uapi for attach bpf program Jesper Dangaard Brouer
2020-06-09 13:47 ` David Ahern
2020-06-09 15:12 ` Jesper Dangaard Brouer
2020-06-09 13:31 ` [PATCH bpf V2 2/2] bpf: selftests and tools use struct bpf_devmap_val from uapi Jesper Dangaard Brouer
2020-06-09 19:03 ` [PATCH bpf V2 0/2] bpf: adjust uapi for devmap prior to kernel release Alexei Starovoitov
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