Re: [PATCH] randomize_range: use random long instead of int

From: Jason Cooper <jason@lakedaemon.net>
To: william.c.roberts@intel.com
Cc: linux-mm@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux@arm.linux.org.uk, akpm@linux-foundation.org,
	keescook@chromium.org, tytso@mit.edu, arnd@arndb.de,
	gregkh@linuxfoundation.org, catalin.marinas@arm.com,
	will.deacon@arm.com, ralf@linux-mips.org,
	benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au,
	davem@davemloft.net, tglx@linutronix.de, mingo@redhat.com,
	hpa@zytor.com, x86@kernel.org, viro@zeniv.linux.org.uk,
	nnk@google.com, jeffv@google.com, salyzyn@android.com,
	dcashman@android.com
Subject: Re: [PATCH] randomize_range: use random long instead of int
Date: Tue, 26 Jul 2016 02:18:30 +0000	[thread overview]
Message-ID: <20160726021830.GC4541@io.lakedaemon.net> (raw)
In-Reply-To: <1469471141-25669-1-git-send-email-william.c.roberts@intel.com>

Hi William, Kees,

On Mon, Jul 25, 2016 at 11:25:41AM -0700, william.c.roberts@intel.com wrote:
> From: William Roberts <william.c.roberts@intel.com>
> 
> Use a long when generating the random range rather than
> an int. This will produce better random distributions as
> well as matching all the types at hand.
> 
> Signed-off-by: William Roberts <william.c.roberts@intel.com>
> ---
>  drivers/char/random.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

Upon further review, I think we should dig into this a little bit
deeper.  Standby, I'll post an RFC series shortly.

thx,

Jason.

> diff --git a/drivers/char/random.c b/drivers/char/random.c
> index 0158d3b..bbf11b5 100644
> --- a/drivers/char/random.c
> +++ b/drivers/char/random.c
> @@ -1837,7 +1837,8 @@ randomize_range(unsigned long start, unsigned long end, unsigned long len)
>  
>  	if (end <= start + len)
>  		return 0;
> -	return PAGE_ALIGN(get_random_int() % range + start);
> +
> +	return PAGE_ALIGN(get_random_long() % range + start);
>  }
>  
>  /* Interface for in-kernel drivers of true hardware RNGs.
> -- 
> 1.9.1
> 