# Re: \[PATCH v29 25/32\] x86/cet/shstk: Handle thread shadow stack

- From: Borislav Petkov \<bp@alien8.de\>
- Date: 2021-08-26 16:50:04 
- List: linux-mm
- Page: https://ratatoskr.run/linux-mm/2021/08/1489866
- Thread: https://ratatoskr.run/linux-doc/2021/08/1484313/t.md

```text
On Fri, Aug 20, 2021 at 11:11:54AM -0700, Yu-cheng Yu wrote:
> diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c
> index 5993aa8db338..7c1ca2476a5e 100644
> --- a/arch/x86/kernel/shstk.c
> +++ b/arch/x86/kernel/shstk.c
> @@ -75,6 +75,61 @@ int shstk_setup(void)
>  	return err;
>  }
>  
> +int shstk_alloc_thread_stack(struct task_struct *tsk, unsigned long clone_flags,
> +			     unsigned long stack_size)
> +{
> +	struct thread_shstk *shstk = &tsk->thread.shstk;
> +	struct cet_user_state *state;
> +	unsigned long addr;
> +
> +	if (!shstk->size)
> +		return 0;
> +
> +	/*
> +	 * Earlier clone() does not pass stack_size.  Use RLIMIT_STACK and

What is "earlier clone()"?

> +	 * cap to 4 GB.
> +	 */

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

```