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 <alexthr...@gmail.com>
Fixes: d2048bafae40 ("rockchip: board: Add board_rng_seed() for all Rockchip
devices")
Reviewed-by: Dragan Simic <dsi...@manjaro.org>
Reviewed-by: Marek Vasut <ma...@denx.de>
---
Changes in v6:
- fix wording in docs and debug message
Changes in v5:
- add docs
Changes in v4:
- fix typos and code style
Changes in v3:
- reword warning
- increase default rng_seed_size to support older linux as well
- reword commit message
Changes in v2:
- add env config knob rng_seed_size
- add warning for small rng_seed_size
- 12-character commit SHA in Fixes
arch/arm/mach-rockchip/board.c | 11 ++++++++++-
common/Kconfig | 3 +++
doc/usage/environment.rst | 5 +++++
include/fdt_support.h | 3 ++-
4 files changed, 20 insertions(+), 2 deletions(-)
diff --git a/arch/arm/mach-rockchip/board.c b/arch/arm/mach-rockchip/board.c
index 3fadf7e412..75d6693e28 100644
--- a/arch/arm/mach-rockchip/board.c
+++ b/arch/arm/mach-rockchip/board.c
@@ -472,9 +472,18 @@ __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, 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 957de0c5c0..8098f90683 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -927,6 +927,9 @@ config BOARD_RNG_SEED
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 cc33d3ec0f..7bd9ffce8d 100644
--- a/doc/usage/environment.rst
+++ b/doc/usage/environment.rst
@@ -323,6 +323,11 @@ netretry
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 741e2360c2..9447a64e06 100644
--- a/include/fdt_support.h
+++ b/include/fdt_support.h
@@ -202,7 +202,8 @@ int ft_board_setup(void *blob, struct bd_info *bd);
*
* 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.
--
2.34.1
