linux-kernel - Re: [PATCH v23 15/28] x86/mm: Update maybe

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Message-ID: <20210322104616.tht6flrxif257fdb@box>
Date:   Mon, 22 Mar 2021 13:46:16 +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>
Subject: Re: [PATCH v23 15/28] x86/mm: Update maybe_mkwrite() for shadow stack

On Tue, Mar 16, 2021 at 08:10:41AM -0700, Yu-cheng Yu wrote:
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index a6c18c5752d6..af805ffde48e 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -997,6 +997,8 @@ static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
>  {
>  	if (likely(vma->vm_flags & VM_WRITE))
>  		pte = pte_mkwrite(pte);
> +	else
> +		pte = arch_maybe_mkwrite(pte, vma);
>  	return pte;
>  }

I think it would be cleaner to allow arch code to override maybe_mkwrite()
and maybe_pmd_mkwrite() altogether. Wrap it into #ifndef maybe_mkwrite
here and provide VM_SHSTK-aware version from <asm/pgtable.h>.

-- 
 Kirill A. Shutemov