linux-kernel - Re: [PATCH] random: move randomize

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Message-Id: <20220516142800.4730a41ec1498d5e3d7863c0@linux-foundation.org>
Date:   Mon, 16 May 2022 14:28:00 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH] random: move randomize_page() into mm where it belongs

On Sat, 14 May 2022 14:05:56 +0200 "Jason A. Donenfeld" <Jason@...c4.com> wrote:

> randomize_page is an mm function. It is documented like one. It contains
> the history of one. It has the naming convention of one. It looks
> just like another very similar function in mm, randomize_stack_top().
> And it has always been maintained and updated by mm people. There is no
> need for it to be in random.c. In the "which shape does not look like
> the other ones" test, pointing to randomize_page() is correct.
> 
> So move randomize_page() into mm/util.c, right next to the similar
> randomize_stack_top() function.
> 
> This commit contains no actual code changes.

hm, does it make sense?

Probably randomize_page() (which used to be called randomize_range())
should have been called randomize_address().  Is it an MM function
then?  Not really - it's simply an application of the random number
generator.  So I think it's more a random thing than an MM thing.

> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -343,6 +343,38 @@ unsigned long randomize_stack_top(unsigned long stack_top)
>  #endif
>  }
>  
> +/**
> + * randomize_page - Generate a random, page aligned address

The patch assumes that drivers/char/random.o is always built into
vmlinux, which appears to be the case.  If some space-conscious person
goes and makes random.o build-time optional then they'll need to make
the appropriate adjustments in util.c.  I see no problems with this.