linux-kernel - Re: [PATCH V2] mm: debug_vm_pgtable: Don't use _

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Message-ID: <30c10b5f-1b26-e0a8-8185-6fa3296d68dc@arm.com>
Date:   Mon, 27 Sep 2021 07:47:27 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     guoren@...nel.org, akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Guo Ren <guoren@...ux.alibaba.com>
Subject: Re: [PATCH V2] mm: debug_vm_pgtable: Don't use __P000 directly



On 9/24/21 11:38 AM, guoren@...nel.org wrote:
> From: Guo Ren <guoren@...ux.alibaba.com>
> 
> The __Pxxx/__Sxxx macros are only for protection_map[] init. All
> usage of them in linux should come from protection_map array.
> 
> Because a lot of architectures would re-initilize protection_map[]
> array, eg: x86-mem_encrypt, m68k-motorola, mips, arm, sparc.
> 
> Using __P000 is not rigorous.
> 
> Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
> Reviewed-by: Andrew Morton <akpm@...ux-foundation.org>

Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>


> 
> ---
> 
> Changes since V2:
>  - s/init protection_map[]/protection_map[] init/
>  - s/Becasue/Because/
>  - Remove unclear part
>  - Replace __P000 and __S000 with protection_map[0] and
>    protection_map[8]
> ---
>  mm/debug_vm_pgtable.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> index 1403639302e4..228e3954b90c 100644
> --- a/mm/debug_vm_pgtable.c
> +++ b/mm/debug_vm_pgtable.c
> @@ -1104,13 +1104,14 @@ static int __init init_args(struct pgtable_debug_args *args)
>  	/*
>  	 * Initialize the debugging data.
>  	 *
> -	 * __P000 (or even __S000) will help create page table entries with
> -	 * PROT_NONE permission as required for pxx_protnone_tests().
> +	 * protection_map[0] (or even protection_map[8]) will help create
> +	 * page table entries with PROT_NONE permission as required for
> +	 * pxx_protnone_tests().
>  	 */
>  	memset(args, 0, sizeof(*args));
>  	args->vaddr              = get_random_vaddr();
>  	args->page_prot          = vm_get_page_prot(VMFLAGS);
> -	args->page_prot_none     = __P000;
> +	args->page_prot_none     = protection_map[0];
>  	args->is_contiguous_page = false;
>  	args->pud_pfn            = ULONG_MAX;
>  	args->pmd_pfn            = ULONG_MAX;
>