linux-kernel - Re: [RFC PATCH 1/3] config: provide a fragment to enable gdb for qemu

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Message-ID: <CAK8P3a1qn2SOsk_Uo_VDGSkR6OsDkqzm0Rbo+5F5Pc1WA3tJzQ@mail.gmail.com>
Date:   Tue, 18 Dec 2018 10:07:21 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Anders Roxell <anders.roxell@...aro.org>
Cc:     Mark Brown <broonie@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC PATCH 1/3] config: provide a fragment to enable gdb for qemu

On Tue, Dec 18, 2018 at 9:45 AM Anders Roxell <anders.roxell@...aro.org> wrote:
>
> On Thu, 13 Dec 2018 at 13:40, Mark Brown <broonie@...nel.org> wrote:
> >
> > On Thu, Dec 13, 2018 at 01:29:08PM +0100, Anders Roxell wrote:
> > > Adding a fragment to make it easier to know what options is needed to
> > > build a kernel to get the that you can debug in qemu.
> >
> > > @@ -0,0 +1,7 @@
> > > +# Enable debug info for gdb
> > > +# CONFIG_COMPILE_TEST is not set
> > > +CONFIG_DEBUG_INFO=y
> > > +CONFIG_GDB_SCRIPTS=y
> >
> > Is this specifically for qemu or is this just good for debugging with
> > GDB in general (eg, via JTAG)?
>
> I haven't tried, and I don't have a JTAG so I could test it =/

The DEBUG_INFO=y and (as a dependency for that) CONFIG_COMPILE_TEST
are definitely needed for all GDB operation. I would assume that
the scripts also work with any other gdb environment, but haven't tried either.

For CONFIG_RANDOMIZE_BASE, I'm not actually sure if that helps or
not. I think I originally suggested to Anders to turn that off when he
was analyzing a bug, but I don't know if it helped or if it works just
as well without that.

        Arnd