Re: [PATCH v2] rockchip: board: Increase rng-seed size to make it sufficient for modern Linux

[Dragan Simic <dsimic@manjaro.org>]

Hello Alex,

Thanks for the v2.  Please see a few comments below.

On 2024-10-14 19:53, Alex Shumsky wrote:
> Modern Linux requires 32 byte seed to initialize random pool, but 
> u-boot
> currently provides only 8 bytes. Increase rng-seed size to make Linux 
> happy and
> initialize rng pool instantly.
> 
> Boot with 8 byte rng-seed:
>     # dmesg | grep crng
>     [   12.089286] random: crng init done
> Boot with 32 byte rng-seed:
>     # dmesg | grep crng
>     [    0.000000] random: crng init done
> 
> https://github.com/torvalds/linux/blob/7234e2ea0edd00bfb6bb2159e55878c19885ce68/drivers/char/random.c#L632
> 
> Signed-off-by: Alex Shumsky <alexthreed@gmail.com>
> Fixes: d2048bafae40 ("rockchip: board: Add board_rng_seed() for all
> Rockchip devices")
> ---
> 
> Changes in v2:
> - add env config knob rng_seed_size

Perhaps the emitted warning should also be mentioned here.

> - 12-character commit SHA in Fixes
> 
>  arch/arm/mach-rockchip/board.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mach-rockchip/board.c 
> b/arch/arm/mach-rockchip/board.c
> index 3fadf7e412..f9f0d7214c 100644
> --- a/arch/arm/mach-rockchip/board.c
> +++ b/arch/arm/mach-rockchip/board.c
> @@ -472,9 +472,15 @@ __weak int misc_init_r(void)
>  __weak int board_rng_seed(struct abuf *buf)
>  {
>  	struct udevice *dev;
> -	size_t len = 0x8;
> +	ulong len = env_get_ulong("rng_seed_size", 10, 32);
>  	u64 *data;
> 
> +	if (len < 32) {
> +		// rng_seed_size should be 32 bytes for Linux 5.19+, or 64 for older 
> Linux'es

Shouldn't it be 8 for older kernels?

> +		log_warning("Too small rng_seed_size (%lu). It is likely
> insufficient to init linux crng\n",
> +			    len);

Perhaps this would read better:

   "Value for rng_seed_size too low (%lu) and likely insufficient
   for the Linux RNG initialization"

> +	}
> +
>  	data = malloc(len);
>  	if (!data) {
>  		printf("Out of memory\n");