linux-kernel - Re: [PATCH] mm: make 'highmem' symbol ro_after

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Message-ID: <YfG/Wi5OBHeDRPdg@kernel.org>
Date:   Wed, 26 Jan 2022 23:38:34 +0200
From:   Mike Rapoport <rppt@...nel.org>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: make 'highmem' symbol ro_after_init

On Mon, Jan 24, 2022 at 06:05:55PM +0100, Ard Biesheuvel wrote:
> The 'highmem' variable is only set at boot, so we can make it
> ro_after_init and prevent it from being corrupted inadvertently, or from
> ending up in a contended cacheline.
> 
> Signed-off-by: Ard Biesheuvel <ardb@...nel.org>

Acked-by: Mike Rapoport <rppt@...ux.ibm.com>

> ---
>  mm/memory.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index c125c4969913..50e82cb94ccc 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -106,7 +106,7 @@ EXPORT_SYMBOL(mem_map);
>   * highstart_pfn must be the same; there must be no gap between ZONE_NORMAL
>   * and ZONE_HIGHMEM.
>   */
> -void *high_memory;
> +void *high_memory __ro_after_init;
>  EXPORT_SYMBOL(high_memory);
>  
>  /*
> -- 
> 2.30.2
> 
> 

-- 
Sincerely yours,
Mike.