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SubjectRe: [patch 1/8] selftests/x86: Test signal frame XSTATE header corruption handling
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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@kernel.org>
>>>
>>> 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

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