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Message-ID: <20160222232738.GB4259@test-lenovo>
Date: Mon, 22 Feb 2016 15:27:38 -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 04/10] x86/xsaves: Introduce a new check that allows
correct xstates copy from kernel to user directly
On Mon, Feb 22, 2016 at 02:42:54PM -0800, Andy Lutomirski wrote:
> > +static int should_save_registers_directly(void)
>
> I don't like the name of this function because:
>
> > +{
> > + /*
> > + * In signal handling path, the kernel already checks if
> > + * FPU instructions have been used before it calls
> > + * copy_fpstate_to_sigframe(). We check this here again
> > + * to detect any potential mis-use and saving invalid
> > + * register values directly to a signal frame.
> > + */
> > + WARN_ONCE(!current->thread.fpu.fpstate_active,
> > + "direct FPU save with no math use\n");
>
> ... Here "direct" seems to mean that we're asking whether to directly save ...
>
> > +
> > + /*
> > + * In the case that we are using a compacted kernel
> > + * xsave area, we can not copy the thread.fpu.state
> > + * directly to userspace and *must* save it from the
> > + * registers directly.
> > + */
>
> ... and here "directly" means *both* copying directly to userspace and
> saving using xsave directly.
>
> So can you rename it to something with an obvious meaning like
> "may_memcpy_fpu_regs" or similar?
This function determines whether the kernel should do
copy_fpregs_to_sigframe(). Perhaps we can re-name it to
may_copy_fpregs_to_sigframe()?
--Yu-cheng
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