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Date: Mon, 15 Aug 2016 11:52:38 -0500
From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
        "H . Peter Anvin" <hpa@zytor.com>, X86 ML <x86@kernel.org>,
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        Frederic Weisbecker <fweisbec@gmail.com>,
        Byungchul Park <byungchul.park@lge.com>,
        Nilay Vaish <nilayvaish@gmail.com>
Subject: Re: [PATCH v3 42/51] x86/unwind: create stack frames for saved
 syscall registers
Message-ID: <20160815165238.6bwekwqdbdxjvfbk@treble>
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On Sun, Aug 14, 2016 at 01:23:11AM -0700, Andy Lutomirski wrote:
> On Fri, Aug 12, 2016 at 7:29 AM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> > The entry code doesn't encode pt_regs for syscalls.  But they're always
> > at the same location, so we can add a manual check for them.
> 
> At first I thought these would be useless (they're the *user* state
> and aren't directly relevant to the kernel), but then I realized that
> they could be extremely valuable: they contain the syscall args.

Yeah, that's what I was thinking.  I'll add that justification to the
patch header.

> Do they display in OOPS dumps?

Yes.

> It might be nice to add orig_ax to the regs display too so we get the
> syscall nr as well.

Hm, good idea.  I'm surprised orig_ax isn't already being shown since it
could be useful for exceptions and irqs too.

-- 
Josh