rockchip: board: Increase rng-seed size to make it sufficient for modern Linux
Increase rng-seed size to make Linux happy and initialize rng pool instantly.
Linux 5.19+ requires 32 bytes of entropy to initialize random pool, but u-boot
currently provides only 8 bytes.
Linux 5.18 and probably some versions before it used to require 64 bytes.
Bump min value to 64 bytes to be on a safe side.
Boot with 8 byte rng-seed (Linux 6.11):
# dmesg | grep crng
[ 12.089286] random: crng init done
Boot with 32 byte rng-seed (Linux 6.11):
# dmesg | grep crng
[ 0.000000] random: crng init done
Linux source references:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/char/random.c?h=v5.19#n551
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/char/random.c?h=v5.18#n236
Signed-off-by: Alex Shumsky <alexthreed@gmail.com>
Fixes: d2048bafae40 ("rockchip: board: Add board_rng_seed() for all Rockchip devices")
Reviewed-by: Dragan Simic <dsimic@manjaro.org>
Reviewed-by: Marek Vasut <marex@denx.de>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/arch/arm/mach-rockchip/board.c b/arch/arm/mach-rockchip/board.c
index 3fadf7e..75d6693 100644
--- a/arch/arm/mach-rockchip/board.c
+++ b/arch/arm/mach-rockchip/board.c
@@ -472,9 +472,18 @@
__weak int board_rng_seed(struct abuf *buf)
{
struct udevice *dev;
- size_t len = 0x8;
+ ulong len = env_get_ulong("rng_seed_size", 10, 64);
u64 *data;
+ if (len < 64) {
+ /*
+ * rng_seed_size should be at least 32 bytes for Linux 5.19+,
+ * or 64 for older Linux kernel versions
+ */
+ log_warning("Value for rng_seed_size (%lu) too low, Linux kernel RNG may fail to initialize early\n",
+ len);
+ }
+
data = malloc(len);
if (!data) {
printf("Out of memory\n");
diff --git a/common/Kconfig b/common/Kconfig
index 90cee19..14a6c44 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -928,6 +928,9 @@
new seed for use on subsequent boots, and whether or not the
kernel should account any entropy from the given seed.
+ Default seed size (64 bytes) can be overridden by a decimal
+ environment variable rng_seed_size.
+
endmenu
menu "Update support"
diff --git a/doc/usage/environment.rst b/doc/usage/environment.rst
index cc33d3e..7bd9ffc 100644
--- a/doc/usage/environment.rst
+++ b/doc/usage/environment.rst
@@ -323,6 +323,11 @@
Useful on scripts which control the retry operation
themselves.
+rng_seed_size
+ Size of random value added to device-tree node /chosen/rng-seed.
+ This variable is given as a decimal number.
+ If unset, 64 bytes is used as the default.
+
silent_linux
If set then Linux will be told to boot silently, by
adding 'console=' to its command line. If "yes" it will be
diff --git a/include/fdt_support.h b/include/fdt_support.h
index 741e236..9447a64 100644
--- a/include/fdt_support.h
+++ b/include/fdt_support.h
@@ -202,7 +202,8 @@
*
* This function is called if CONFIG_BOARD_RNG_SEED is set, and must
* be provided by the board. It should return, via @buf, some suitable
- * seed value to pass to the kernel.
+ * seed value to pass to the kernel. Seed size could be set in a decimal
+ * environment variable rng_seed_size and it defaults to 64 bytes.
*
* @param buf A struct abuf for returning the seed and its size.
* @return 0 if ok, negative on error.