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

[Dragan Simic]

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 <alexthr...@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");