Re: [patch 1/8] selftests/x86: Test signal frame XSTATE header corruption handling

[Shuah Khan]

On 6/2/21 8:15 AM, Thomas Gleixner wrote:
> On Wed, Jun 02 2021 at 14:38, Borislav Petkov wrote:
> > On Wed, Jun 02, 2021 at 11:55:44AM +0200, Thomas Gleixner wrote:
> > > From: Andy Lutomirski <luto@xxxxxxxxxx>
> > >
> > > This is very heavily based on some code from Thomas Gleixner.  On a system
> > > without XSAVES, it triggers the WARN_ON():
> > >
> > >      Bad FPU state detected at copy_kernel_to_fpregs+0x2f/0x40, reinitializing FPU registers.
> >
> > That triggers
> >
> > [  149.497274] corrupt_xstate_[1627] bad frame in rt_sigreturn frame:00000000dad08ab1 ip:7f031449ffe1 sp:7ffd0c5c59f0 orax:ffffffffffffffff in libpthread-2.31.so[7f0314493000+10000]
> >
> > on an AMD laptop here.
>
> Yes, that's the ratelimited printk in the signal code.
>
> > > +static inline void __cpuid(unsigned int *eax, unsigned int *ebx,
> > > +			   unsigned int *ecx, unsigned int *edx)
> > > +{
> > > +	asm volatile(
> > > +		"cpuid;"
> > > +		: "=a" (*eax),
> > > +		  "=b" (*ebx),
> > > +		  "=c" (*ecx),
> > > +		  "=d" (*edx)
> > > +		: "0" (*eax), "2" (*ecx));
> > > +}
> > > +
> > > +static inline int xsave_enabled(void)
> > > +{
> > > +	unsigned int eax, ebx, ecx, edx;
> > > +
> > > +	eax = 0x1;
> > > +	ecx = 0x0;
> > > +	__cpuid(&eax, &ebx, &ecx, &edx);
> > > +
> > > +	/* Is CR4.OSXSAVE enabled ? */
> > > +	return ecx & (1U << 27);
> > > +}
> >
> > One fine day someone should sit down and unify all those auxillary
> > functions used in the selftests into a lib...
>
> Yes please. Shuah, that would be a great newcomer task...

Yes. I will add to newcomer task list.

thanks,
-- Shuah