linux-kernel - Re: [PATCH -next 3/4] arm64: mm: add support for page table check

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Date:   Mon, 21 Mar 2022 16:40:59 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Tong Tiangen <tongtiangen@...wei.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Pasha Tatashin <pasha.tatashin@...een.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Will Deacon <will@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH -next 3/4] arm64: mm: add support for page table check

On Mon, Mar 21, 2022 at 02:15:36PM +0800, Tong Tiangen wrote:
> Considering all your suggestions, The final logic should be:
> 
> +#define pte_user(pte)          (!!(pte_val(pte) & PTE_USER))
> 
> +#define pmd_user(pmd)		pte_user(pmd_pte(pmd))
> +#define pmd_user_exec(pmd)	pte_user_exec(pmd_pte(pmd))
> 
> +#define pud_user(pud)          pte_user(pud_pte(pud))
> 
> +static inline bool pte_user_accessible_page(pte_t pte)
> +{
> +	return pte_present(pte) && (pte_user(pte)|| pte_user_exec(pte));
> +}

This is fine.

> +static inline bool pmd_user_accessible_page(pmd_t pmd)
> +{
> +	return pmd_present(pmd) && (pmd_user(pmd)|| pmd_user_exec(pmd));
> +}

That's fine as well assuming that the function is only called on the
set_pmd_at() path where we know that the pmd would be a block mapping
(huge page). I think that's the case from a quick look at the current
x86 implementation.

> +static inline bool pud_user_accessible_page(pud_t pud)
> +{
> +	return pud_present(pud) && pud_user(pud);
> +}

Same here.

-- 
Catalin