linux-kernel - Re: [PATCH 0/3 v2] arm64/ptrace: allow to get all registers on syscall traps

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Message-ID: <20210208183752.GB559391@gmail.com>
Date:   Mon, 8 Feb 2021 10:37:52 -0800
From:   Andrei Vagin <avagin@...il.com>
To:     Keno Fischer <keno@...iacomputing.com>
Cc:     Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Oleg Nesterov <oleg@...hat.com>,
        linux-arm-kernel@...ts.infradead.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-api@...r.kernel.org,
        Anthony Steinhauser <asteinhauser@...gle.com>,
        Dave Martin <Dave.Martin@....com>, Kyle Huey <khuey@...nos.co>,
        Robert O'Callahan <roc@...nos.co>
Subject: Re: [PATCH 0/3 v2] arm64/ptrace: allow to get all registers on
 syscall traps

On Mon, Feb 01, 2021 at 07:11:12PM -0500, Keno Fischer wrote:
> Hi Andrei,
> 
> > This series introduces the PTRACE_O_ARM64_RAW_REGS option. If it is set,
> > PTRACE_GETREGSET returns values of all registers, and PTRACE_SETREGSET
> > allows to change any of them.
> 
> thanks for picking this up. I meant to work on this, but unfortunately ran out
> of time to be able to push it through, so I'm glad you're working on
> it, since it
> does absolutely need to get fixed. Besides this issue, the other problem we
> ran into when trying to port our ptracer to aarch64 is that orig_x0 is not
> accessible through the ptrace interface on aarch64, which can cause tricky
> behavior around restarts.

Could you describe the problem in more details? I wonder whether we have
the same thing in CRIU...

> We managed to work around that in the end,
> but it's painful. If we're fixing the kernel here anyway, I'm wondering if
> we might want to address that as well while we're at it.

Sure let think how to do this properly.

In this case, I think the ptrace option isn't a good choise. I don't
think that it is a good idea to change the layout of regset depending on
options...

Thanks,
Andrei

> 
> Keno