linux-kernel - Re: [PATCH] ARM: VDSO: put read only/mostly objects into proper sections

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Date:	Wed, 10 Aug 2016 17:59:58 +0800
From:	Jisheng Zhang <jszhang@...vell.com>
To:	<linux@...linux.org.uk>, <nathan_lynch@...tor.com>,
	Kees Cook <keescook@...omium.org>
CC:	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: VDSO: put read only/mostly objects into proper
 sections

+ Kees

On Wed, 10 Aug 2016 17:09:47 +0800 wrote:

> vdso_data_mapping is never modified, so mark it as const.
> 
> vdso_data_page and vdso_text_mapping are initialized by vdso_init(),
> thereafter are mostly read during vdso special mapping handling.
> 
> The fact that they are mostly read and not written to makes them
> candidates for __read_mostly declarations.

Inspired by Kees's "arm: apply more __ro_after_init", is it better
to mark these vars as __ro_after_init?

Thanks,
Jisheng

> 
> Signed-off-by: Jisheng Zhang <jszhang@...vell.com>
> ---
>  arch/arm/kernel/vdso.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/kernel/vdso.c b/arch/arm/kernel/vdso.c
> index 994e971..c946092 100644
> --- a/arch/arm/kernel/vdso.c
> +++ b/arch/arm/kernel/vdso.c
> @@ -47,13 +47,13 @@ unsigned int vdso_total_pages __read_mostly;
>  static union vdso_data_store vdso_data_store __page_aligned_data;
>  static struct vdso_data *vdso_data = &vdso_data_store.data;
>  
> -static struct page *vdso_data_page;
> -static struct vm_special_mapping vdso_data_mapping = {
> +static struct page *vdso_data_page __read_mostly;
> +static const struct vm_special_mapping vdso_data_mapping = {
>  	.name = "[vvar]",
>  	.pages = &vdso_data_page,
>  };
>  
> -static struct vm_special_mapping vdso_text_mapping = {
> +static struct vm_special_mapping vdso_text_mapping __read_mostly = {
>  	.name = "[vdso]",
>  };
>