linux-kernel - Re: eh_frame confusion

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Message-ID: <20200302124442.GI22482@gate.crashing.org>
Date:   Mon, 2 Mar 2020 06:44:42 -0600
From:   Segher Boessenkool <segher@...nel.crashing.org>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: eh_frame confusion

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.


Segher