From: Jiri Olsa <jolsa@redhat.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Qais Yousef <qais.yousef@arm.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>, Jiri Olsa <jolsa@kernel.org>,
Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
open list <linux-kernel@vger.kernel.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>
Subject: Re: BTFIDS: FAILED unresolved symbol udp6_sock
Date: Sun, 3 Jan 2021 00:06:54 +0100 [thread overview]
Message-ID: <20210102230654.GA732432@krava> (raw)
In-Reply-To: <CAEf4BzYbeQqzK2n9oz6wqysVj35k+VZC7DZrXFEtjUM6eiyvOA@mail.gmail.com>
On Sat, Jan 02, 2021 at 02:25:34PM -0800, Andrii Nakryiko wrote:
SNIP
> >
> > so your .config has
> > CONFIG_CRYPTO_DEV_BCM_SPU=y
> >
> > and that defines 'struct device_private' which
> > clashes with the same struct defined in drivers/base/base.h
> >
> > so several networking structs will be doubled, like net_device:
> >
> > $ bpftool btf dump file ../vmlinux.config | grep net_device\' | grep STRUCT
> > [2731] STRUCT 'net_device' size=2240 vlen=133
> > [113981] STRUCT 'net_device' size=2240 vlen=133
> >
> > each is using different 'struct device_private' when it's unwinded
> >
> > and that will confuse BTFIDS logic, becase we have multiple structs
> > with the same name, and we can't be sure which one to pick
> >
> > perhaps we should check on this in pahole and warn earlier with
> > better error message.. I'll check, but I'm not sure if pahole can
> > survive another hastab ;-)
> >
> > Andrii, any ideas on this? ;-)
>
> It's both unavoidable and correct from the C type system's
> perspective, so there is nothing for pahole to warn about. We used to
> have (for a long time) a similar clash with two completely different
> ring_buffer structs. Eventually they just got renamed to avoid
> duplication of related structs (task_struct and tons of other). But
> both BTF dedup and CO-RE relocation algorithms are designed to handle
> this correctly, ...
AFAIU it's all correctly dedulicated, but still all structs that
contain (at some point) 'struct device_private' will appear twice
in BTF data.. each with different 'struct device_private'
> ... so perhaps BTFIDS should be able to handle this as
> well?
hm, BTFIDS sees BTF data with two same struct names and has no
way to tell which one to use
unless we have some annotation data for BTF types I don't
see a way to handle this correctly.. but I think we can
detect this directly in BTFIDS and print more accurate error
message
as long as we dont see this on daily basis, I think that better
error message + following struct rename is good solution
>
> >
> > easy fix is the patch below that renames the bcm's structs,
> > it makes the kernel to compile.. but of course the new name
> > is probably wrong and we should push this through that code
> > authors
>
> In this case, I think renaming generic device_private name is a good
> thing regardless.
ok, I'll send the change
jirka
next prev parent reply other threads:[~2021-01-02 23:08 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-29 15:13 BTFIDS: FAILED unresolved symbol udp6_sock Qais Yousef
2020-12-29 17:34 ` Jiri Olsa
2020-12-29 23:28 ` Qais Yousef
2020-12-30 9:03 ` Jiri Olsa
2020-12-30 13:27 ` Jiri Olsa
2020-12-30 13:28 ` Jiri Olsa
2020-12-30 14:19 ` Arnaldo Carvalho de Melo
2020-12-30 15:04 ` Jiri Olsa
2020-12-30 15:29 ` Qais Yousef
2021-01-02 22:25 ` Andrii Nakryiko
2021-01-02 23:06 ` Jiri Olsa [this message]
2021-01-04 20:54 ` Andrii Nakryiko
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