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SubjectRe: [PATCH 18/24] x86/fpu: Prepare copy_fpstate_to_sigframe() for TIF_NEED_FPU_LOAD
On 2019-03-31 20:20:25 [+0200], Thomas Gleixner wrote:
>
> I think this should do the following:
>
> fpregs_lock();
> if (!test_thread_flag(TIF_NEED_FPU_LOAD)) {
> pagefault_disable();
> ret = copy_fpu_to_user(...);
> pagefault_enable();
> if (!res)
> return 0;
> copy_fpregs_to_fpstate(fpu);
> }
> fpregs_unlock();
>
> The point is that in most cases the direct store from the FPU registers to
> user space will succeed simply because the stack is accessible and you only
> do the store in kernel memory and copy when that fails.

let me try that.

> Thanks,
>
> tglx
>

Sebastian

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