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From: John Fastabend <john.fastabend@gmail.com>
To: John Fastabend <john.fastabend@gmail.com>,
	Andrii Nakryiko <andrii.nakryiko@gmail.com>,
	Alexei Starovoitov <ast@fb.com>
Cc: John Fastabend <john.fastabend@gmail.com>,
	Andrii Nakryiko <andriin@fb.com>, bpf <bpf@vger.kernel.org>,
	Networking <netdev@vger.kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Kernel Team <Kernel-team@fb.com>
Subject: Re: [PATCH bpf-next 1/2] libbpf: stop enforcing kern_version, populate it for users
Date: Fri, 18 Oct 2019 07:49:13 -0700	[thread overview]
Message-ID: <5da9d0e9bca63_1a132ad0125505c044@john-XPS-13-9370.notmuch> (raw)
In-Reply-To: <5d976c62bb52b_583b2ae668e6e5b41@john-XPS-13-9370.notmuch>

John Fastabend wrote:
> Andrii Nakryiko wrote:
> > On Fri, Oct 4, 2019 at 7:36 AM Alexei Starovoitov <ast@fb.com> wrote:
> > >
> > > On 10/4/19 7:32 AM, Andrii Nakryiko wrote:
> > > >> If we are not going to validate the section should we also skip collect'ing it?
> > > > Well, if user supplied version, we will parse and use it to override
> > > > out prepopulated one, so in that sense we do have validation.
> > > >
> > > > But I think it's fine just to drop it altogether. Will do in v3.
> > > >
> > >
> > > what about older kernel that still enforce it?
> > > May be populate it in bpf_attr while loading, but
> > > don't check it in elf from libbpf?
> > 
> > That's what my change does. I pre-populate correct kernel version in
> > bpf_object->kern_version from uname(). If ELF has "version" section,
> > we still parse it and override bpf_object->kern_version.
> > bpf_object->kern_version then is always specified as part of
> > bpf_prog_load->kern_version.
> > 
> > So what we are discussing here is to not even look at user-provided
> > version, but just always specify correct current kernel version. So I
> > don't think we are going to break anything, except we might allow to
> > pass some programs that were failing before due to unspecified or zero
> > version.
> > 
> > So with that, do you think it's ok to get rid of version section altogether?
> 
> Should be fine on my side. Go for it.

... Actually it turns out this broke some kernels that report via uname()
incorrect version info. Sent a patch out to add just the bits back we need
to get it working again.

To bad but I can't fix distributions that are deployed so...

  reply	other threads:[~2019-10-18 14:49 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-04  3:00 [PATCH bpf-next 0/2] Add new-style bpf_object__open APIs Andrii Nakryiko
2019-10-04  3:00 ` [PATCH bpf-next 1/2] libbpf: stop enforcing kern_version, populate it for users Andrii Nakryiko
2019-10-04 14:05   ` John Fastabend
2019-10-04 14:32     ` Andrii Nakryiko
2019-10-04 14:36       ` Alexei Starovoitov
2019-10-04 14:55         ` John Fastabend
2019-10-04 15:07         ` Andrii Nakryiko
2019-10-04 15:59           ` John Fastabend
2019-10-18 14:49             ` John Fastabend [this message]
2019-10-04  3:00 ` [PATCH bpf-next 2/2] libbpf: add bpf_object__open_{file,mem} w/ extensible opts Andrii Nakryiko

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