Re: [PATCH v24 18/30] mm/mmap: Add shadow stack pages to memory accounting

[Kirill A. Shutemov]

On Thu, Apr 01, 2021 at 03:10:52PM -0700, Yu-cheng Yu wrote:
> Account shadow stack pages to stack memory.
> 
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> ---
> v24:
> - Change arch_shadow_stack_mapping() to is_shadow_stack_mapping().
> - Change VM_SHSTK to VM_SHADOW_STACK.
> 
>  arch/x86/mm/pgtable.c   |  7 +++++++
>  include/linux/pgtable.h | 11 +++++++++++
>  mm/mmap.c               |  5 +++++
>  3 files changed, 23 insertions(+)
> 
> diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
> index e778dbbef3d8..212a8c1fe5ba 100644
> --- a/arch/x86/mm/pgtable.c
> +++ b/arch/x86/mm/pgtable.c
> @@ -897,3 +897,10 @@ int pmd_free_pte_page(pmd_t *pmd, unsigned long addr)
>  
>  #endif /* CONFIG_X86_64 */
>  #endif	/* CONFIG_HAVE_ARCH_HUGE_VMAP */
> +
> +#ifdef CONFIG_ARCH_HAS_SHADOW_STACK
> +bool is_shadow_stack_mapping(vm_flags_t vm_flags)
> +{
> +	return (vm_flags & VM_SHADOW_STACK);
> +}

No, just define it as you have here in linux/mm.h. It will always be false
for !CONFIG_ARCH_HAS_SHADOW_STACK as VM_SHADOW_STACK is 0 there.

This maze of #ifdefs are unneeded.

-- 
 Kirill A. Shutemov