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From: Florian Weimer <fweimer@redhat.com>
To: Jiri Slaby <jirislaby@kernel.org>
Cc: "Michal Suchánek" <msuchanek@suse.de>,
	"Jiri Olsa" <jolsa@redhat.com>, "Yonghong Song" <yhs@fb.com>,
	linux-kernel@vger.kernel.org, "Martin KaFai Lau" <kafai@fb.com>,
	"David S. Miller" <davem@davemloft.net>,
	"Hideaki YOSHIFUJI" <yoshfuji@linux-ipv6.org>,
	"David Ahern" <dsahern@kernel.org>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Alexei Starovoitov" <ast@kernel.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"Andrii Nakryiko" <andrii@kernel.org>,
	"Song Liu" <songliubraving@fb.com>,
	"John Fastabend" <john.fastabend@gmail.com>,
	"KP Singh" <kpsingh@kernel.org>,
	netdev@vger.kernel.org, bpf@vger.kernel.org,
	"Jiri Olsa" <jolsa@kernel.org>,
	"Jesper Dangaard Brouer" <brouer@redhat.com>
Subject: Re: linux-next failing build due to missing cubictcp_state symbol
Date: Fri, 07 May 2021 09:10:05 +0200	[thread overview]
Message-ID: <87lf8rf29e.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <6c14f3c8-7474-9f3f-b4a6-2966cb19e1ed@kernel.org> (Jiri Slaby's message of "Mon, 3 May 2021 08:11:50 +0200")

* Jiri Slaby:

> The dot makes the difference, of course. The question is why is it
> there? I keep looking into it. Only if someone has an immediate
> idea...

We see the failure on aarch64 as well, with 8404c9fbc84b741
(from Linus' tree).

As far as I can tell, the core issue is that BTF_ID is applied to a
symbol which is defined as static on the C side (and even in a different
translation unit, but this aspect doesn't really matter).  The compiler
can and will change symbol names, calling conventions and data layout
for static functions/variables, so this is never going to work reliably.
It is possible to inhibit these optimizations by using __attribute__
((used)).  But I'm pretty sure that BTF generation fails to work
properly if there are symbol name collisions, so I think it's better to
drop the static and rely on duplicate symbol checks from the linker
(which of course does not happen for C entities declared static).

Thanks,
Florian


  parent reply	other threads:[~2021-05-07  7:10 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-23 13:05 linux-next failing build due to missing cubictcp_state symbol Michal Suchánek
2021-04-23 14:41 ` Yonghong Song
2021-04-23 17:55   ` Michal Suchánek
2021-04-25 11:15     ` Michal Suchánek
2021-04-26 11:32       ` Michal Suchánek
2021-04-26 12:12         ` Michal Suchánek
2021-04-26 12:14           ` Michal Suchánek
2021-04-26 15:41             ` Yonghong Song
2021-04-26 16:03               ` Jiri Olsa
2021-04-26 19:16                 ` Jiri Olsa
2021-04-27 12:12                   ` Michal Suchánek
2021-04-30 17:47                     ` Michal Suchánek
2021-04-30 18:26                       ` Michal Suchánek
2021-05-01  6:45                       ` Jiri Slaby
2021-05-01 10:54                         ` Michal Suchánek
2021-05-03  6:11                         ` Jiri Slaby
2021-05-03  7:13                           ` Michal Suchánek
2021-05-03  7:59                           ` Jiri Slaby
2021-05-03  8:59                             ` Jiri Slaby
2021-05-03 10:08                               ` Jiri Olsa
2021-05-03 16:46                                 ` Michal Suchánek
2021-05-03 16:58                                   ` Michal Suchánek
2021-05-04  6:41                                 ` Jiri Slaby
2021-05-06  5:31                                   ` Martin KaFai Lau
2021-05-06 13:16                                     ` Jiri Olsa
2021-05-07  7:10                           ` Florian Weimer [this message]
2021-05-05 13:56                   ` Michal Suchánek
2021-05-06  4:31                     ` Jiri Slaby
2021-05-06  5:20                       ` Martin KaFai Lau
2021-05-06  5:54                       ` Jiri Slaby
2021-05-06  8:19                         ` Michal Suchánek

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