Re: [PATCH 5/6] x86/shstk: don't create the shadow stack for PF_USER_WORKERs

[Mark Brown]

On Fri, Aug 15, 2025 at 05:43:11PM +0200, Oleg Nesterov wrote:
> On 08/15, Mark Brown wrote:

> > Sure, but OTOH at least for arm64 there's no cost to leaving the feature
> > enabled unless you actually execute userspace code so if we never return
> > to userspace writing the code to disable isn't really buying us anything.

> The fact that a kernel thread can have the pointless ARCH_SHSTK_SHSTK is
> the only reason I know why x86_task_fpu(PF_USER_WORKER) has to work.

> I'd like to make this logic consistent with PF_KTHREAD, and in the longer
> term change the x86 FPU code so that the kernel threads can run without
> without "struct fpu" attached to task_struct.

OK, that's entirely x86 specific - there's no reason we'd want to do
that for arm64.

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