linux-kernel - Re: [PATCH 08/10] x86/xsaves: Fix PTRACE frames for XSAVES

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Date:	Mon, 22 Feb 2016 14:50:00 -0800
From:	Yu-cheng Yu <yu-cheng.yu@...el.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	X86 ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...e.de>,
	Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>,
	"Ravi V. Shankar" <ravi.v.shankar@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>
Subject: Re: [PATCH 08/10] x86/xsaves: Fix PTRACE frames for XSAVES

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