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

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Message-ID: <20210409152547.ljbcoqrqyej7ojxs@box.shutemov.name>
Date:   Fri, 9 Apr 2021 18:25:47 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc:     x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...nel.org>,
        Balbir Singh <bsingharora@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>,
        Dave Martin <Dave.Martin@....com>,
        Weijiang Yang <weijiang.yang@...el.com>,
        Pengfei Xu <pengfei.xu@...el.com>,
        Haitao Huang <haitao.huang@...el.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH v24 18/30] mm/mmap: Add shadow stack pages to memory
 accounting

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@...el.com>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> ---
> 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