From: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Segher Boessenkool <segher@kernel.crashing.org>,
Michael Ellerman <mpe@ellerman.id.au>
Cc: Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Subject: Re: eh_frame confusion
Date: Mon, 02 Mar 2020 22:47:18 +0530 [thread overview]
Message-ID: <1583169014.zvau4om8mi.naveen@linux.ibm.com> (raw)
In-Reply-To: <20200302124442.GI22482@gate.crashing.org>
Segher Boessenkool wrote:
> On Mon, Mar 02, 2020 at 11:56:05AM +0100, Rasmus Villemoes wrote:
>> I'm building a ppc32 kernel, and noticed that after upgrading from gcc-7
>> to gcc-8 all object files now end up having .eh_frame section.
>
> Since GCC 8, we enable -fasynchronous-unwind-tables by default for
> PowerPC. See https://gcc.gnu.org/r259298 .
>
>> For
>> vmlinux, that's not a problem, because they all get discarded in
>> arch/powerpc/kernel/vmlinux.lds.S . However, they stick around in
>> modules, which doesn't seem to be useful - given that everything worked
>> just fine with gcc-7, and I don't see anything in the module loader that
>> handles .eh_frame.
>
> It is useful for debugging. Not many people debug the kernel like this,
> of course.
I'm trying to understand if we need that. Other architectures seems to
pass -fasynchronous-unwind-tables only for the vdso, but disable it for
the kernel build. I suppose we can do the same.
If using -fno-asynchronous-unwind-tables, would crash/perf have
problems?
- Naveen
next prev parent reply other threads:[~2020-03-02 17:17 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-02 10:56 eh_frame confusion Rasmus Villemoes
2020-03-02 12:44 ` Segher Boessenkool
2020-03-02 17:17 ` Naveen N. Rao [this message]
2020-03-02 17:09 ` Naveen N. Rao
2020-03-02 17:32 ` Naveen N. Rao
2020-03-03 9:50 ` Rasmus Villemoes
2020-03-05 12:47 ` Naveen N. Rao
2020-03-03 10:28 ` Michael Ellerman
2020-03-05 12:41 ` Naveen N. Rao
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