linux-kernel - Re: [PATCH RFC 0/2] Add basic tracing support for m68k

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Message-ID: <CAP4=nvTjdZRfWtpvM+gThPv6SghW96i9YykA88vAFH5x39GZqw@mail.gmail.com>
Date: Thu, 28 Nov 2024 16:25:45 +0100
From: Tomas Glozar <tglozar@...hat.com>
To: Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
Cc: Steven Rostedt <rostedt@...dmis.org>, linux-m68k@...ts.linux-m68k.org, 
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	Geert Uytterhoeven <geert@...ux-m68k.org>, Greg Ungerer <gerg@...ux-m68k.org>
Subject: Re: [PATCH RFC 0/2] Add basic tracing support for m68k

po 18. 11. 2024 v 11:13 odesílatel Jean-Michel Hautbois
<jeanmichel.hautbois@...eli.org> napsal:
>
> I had to modify the source code a bit, as it does not compile with my
> uclibc toolchain:
> ...

glibc added a gettid() wrapper with version 2.30; earlier glibc and
uclibc do not have it. That can be fixed by conditionally including
the inline function if on glibc lower than 2.30 or another libc; for
reference on how to detect that, see how kernel self tests do it [1].

As of the FOPTS changes: are those necessary for rtla to build, or
were you just using them for easier debugging? AFAIK rtla shouldn't
depend on unwind tables or stack protection for functionality.

>
> But it is not enough, as executing rtla fails with a segfault.
> I can dump a core, but I could not manage to build gdb for my board so I
> can't debug it (I don't know how to debug a coredump without gdb !).
>
> JM
>

I have seen a similar libtraceevent-related rtla segfault recently on
ARM64, which was fixed by updating libtraceevent to a version that
includes the fix. Such issues are caused by the files for kernel
tracepoint tracefs having different contents on different
architectures, exposing bugs. I see Steven has already fixed one of
the issues on m68k [2].

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/testing/selftests/nolibc/nolibc-test.c#n1008
[2] https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/commit/?id=45a9b0647c904b7bf1240da5a11fe3a1ffd1006d

Tomas