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Message-ID: <20201230152946.gththmiujgj7qkj4@e107158-lin>
Date: Wed, 30 Dec 2020 15:29:46 +0000
From: Qais Yousef <qais.yousef@....com>
To: Jiri Olsa <jolsa@...hat.com>
Cc: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Jiri Olsa <jolsa@...nel.org>, netdev@...r.kernel.org,
bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: BTFIDS: FAILED unresolved symbol udp6_sock
On 12/30/20 14:28, Jiri Olsa wrote:
> On Wed, Dec 30, 2020 at 02:28:02PM +0100, Jiri Olsa wrote:
> > On Wed, Dec 30, 2020 at 10:03:37AM +0100, Jiri Olsa wrote:
> > > On Tue, Dec 29, 2020 at 11:28:35PM +0000, Qais Yousef wrote:
> > > > Hi Jiri
> > > >
> > > > On 12/29/20 18:34, Jiri Olsa wrote:
> > > > > On Tue, Dec 29, 2020 at 03:13:52PM +0000, Qais Yousef wrote:
> > > > > > Hi
> > > > > >
> > > > > > When I enable CONFIG_DEBUG_INFO_BTF I get the following error in the BTFIDS
> > > > > > stage
> > > > > >
> > > > > > FAILED unresolved symbol udp6_sock
> > > > > >
> > > > > > I cross compile for arm64. My .config is attached.
> > > > > >
> > > > > > I managed to reproduce the problem on v5.9 and v5.10. Plus 5.11-rc1.
> > > > > >
> > > > > > Have you seen this before? I couldn't find a specific report about this
> > > > > > problem.
> > > > > >
> > > > > > Let me know if you need more info.
> > > > >
> > > > > hi,
> > > > > this looks like symptom of the gcc DWARF bug we were
> > > > > dealing with recently:
> > > > >
> > > > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97060
> > > > > https://lore.kernel.org/lkml/CAE1WUT75gu9G62Q9uAALGN6vLX=o7vZ9uhqtVWnbUV81DgmFPw@mail.gmail.com/#r
> > > > >
> > > > > what pahole/gcc version are you using?
> > > >
> > > > I'm on gcc 9.3.0
> > > >
> > > > aarch64-linux-gnu-gcc (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0
> > > >
> > > > I was on pahole v1.17. I moved to v1.19 but I still see the same problem.
> > >
> > > I can reproduce with your .config, but make 'defconfig' works,
> > > so I guess it's some config option issue, I'll check later today
My .config was a defconfig + CONFIG_DEBUG_INFO_BTF + convert all modules to
built-in.
> >
> > so your .config has
> > CONFIG_CRYPTO_DEV_BCM_SPU=y
Ah, how random. I removed this config and indeed it does work then, thanks!
> >
> > 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
We can't tell which object/subsystem the struct come from?
Or maybe we can introduce some annotation to help BTFIDS to pick the right one?
> >
> > 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? ;-)
> >
> > 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
>
> also another quick fix is to switch it to module
This works too.
Thanks for your speedy response.
Cheers
--
Qais Yousef
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