linux-kernel - Re: [GIT PULL] x86/asm changes for v5.6

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Message-ID: <20200128223110.GB6787@zn.tnic>
Date:   Tue, 28 Jan 2020 23:31:10 +0100
From:   Borislav Petkov <bp@...e.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        "Luck, Tony" <tony.luck@...el.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] x86/asm changes for v5.6

On Tue, Jan 28, 2020 at 01:04:19PM -0800, Linus Torvalds wrote:
> On Tue, Jan 28, 2020 at 12:41 PM Luck, Tony <tony.luck@...el.com> wrote:
> >
> > Is there still some easy way to get gdb to disassemble from /dev/kmem
> > to see what we ended up with after all the patching?
> 
> Hmm. No, I think it's all gone.
> 
> It _used_ to be easy to just do "objdump --disassemble /proc/kcore" as
> root, but I think we've broken that long ago.

Either booting with "debug-alternative" on baremetal or starting a guest
and stopping it with gdb and examining the patched memory is what I've
been using to hack on the alternatives in past years. Guest won't help
you a whole lot with FSRM but you could "force it", for example.

-- 
Regards/Gruss,
    Boris.

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