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Date: Mon, 22 Feb 2016 14:50:00 -0800
From: Yu-cheng Yu <yu-cheng.yu@intel.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: X86 ML <x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@suse.de>,
        Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>,
        "Ravi V. Shankar" <ravi.v.shankar@intel.com>,
        Fenghua Yu <fenghua.yu@intel.com>
Subject: Re: [PATCH 08/10] x86/xsaves: Fix PTRACE frames for XSAVES
Message-ID: <20160222225000.GA4259@test-lenovo>
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On Mon, Feb 22, 2016 at 02:45:54PM -0800, Andy Lutomirski wrote:
> > +/*
> > + * Convert from kernel XSAVES compacted format to standard format and copy
> > + * to a ptrace buffer. It supports partial copy but pos always starts from
> > + * zero. This is called from xstateregs_get() and there we check the cpu
> > + * has XSAVES.
> > + */
> > +int copyout_from_xsaves(unsigned int pos, unsigned int count, void *kbuf,
> > +                       void __user *ubuf, const struct xregs_state *xsave)
> 
> Now that you've written this code, can it be shared with the signal
> handling code?
> 

For signal handling, we most likely save registers directly to memory.
But for ptrace, the thread being debugged is not the active thread.
Please let me think about it more.

--Yu-cheng