linux-kernel - Re: [PATCH v1] mseal: move can_do

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Message-ID: <2m3zmlehfigs5r7rptwcoft3j4fipfkgfxmdrdttpf76hwhwae@vclfa5ulcmv2>
Date: Thu, 5 Dec 2024 23:25:43 -0500
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: jeffxu@...omium.org
Cc: akpm@...ux-foundation.org, vbabka@...e.cz, lorenzo.stoakes@...cle.com,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
        linux-mm@...ck.org, jorgelo@...omium.org, keescook@...omium.org,
        pedro.falcato@...il.com, rdunlap@...radead.org
Subject: Re: [PATCH v1] mseal: move can_do_mseal to mseal.c

* jeffxu@...omium.org <jeffxu@...omium.org> [241205 20:39]:
> From: Jeff Xu <jeffxu@...omium.org>
> 
> No code logic change.
> 
> can_do_mseal is called exclusively by mseal.c,
> and mseal.c is compiled only when CONFIG_64BIT flag is
> set in makefile. Therefore, it is unnecessary to have
> 32 bit stub function in the header file.

There is no reason to keep this function at all; it is used in one
place, and that place uses three lines of code as well.

In fact, having it separate from the comment about flags being reserved
makes the function very puzzling.

> 
> Signed-off-by: Jeff Xu <jeffxu@...omium.org>
> ---
>  mm/internal.h | 16 ----------------
>  mm/mseal.c    |  8 ++++++++
>  2 files changed, 8 insertions(+), 16 deletions(-)
> 
> diff --git a/mm/internal.h b/mm/internal.h
> index 74dc1c48fa31..5e4ef5ce9c0a 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -1457,22 +1457,6 @@ void __meminit __init_single_page(struct page *page, unsigned long pfn,
>  unsigned long shrink_slab(gfp_t gfp_mask, int nid, struct mem_cgroup *memcg,
>  			  int priority);
>  
> -#ifdef CONFIG_64BIT
> -static inline int can_do_mseal(unsigned long flags)
> -{
> -	if (flags)
> -		return -EINVAL;
> -
> -	return 0;
> -}
> -
> -#else
> -static inline int can_do_mseal(unsigned long flags)
> -{
> -	return -EPERM;
> -}
> -#endif
> -
>  #ifdef CONFIG_SHRINKER_DEBUG
>  static inline __printf(2, 0) int shrinker_debugfs_name_alloc(
>  			struct shrinker *shrinker, const char *fmt, va_list ap)
> diff --git a/mm/mseal.c b/mm/mseal.c
> index 81d6e980e8a9..e167220a0bf0 100644
> --- a/mm/mseal.c
> +++ b/mm/mseal.c
> @@ -158,6 +158,14 @@ static int apply_mm_seal(unsigned long start, unsigned long end)
>  	return 0;
>  }
>  
> +static inline int can_do_mseal(unsigned long flags)
> +{
> +	if (flags)
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
>  /*
>   * mseal(2) seals the VM's meta data from
>   * selected syscalls.
> -- 
> 2.47.0.338.g60cca15819-goog
>