Commit 428826f5358c ("fdt: add support for rng-seed") introduced
add_bootloader_randomness(), permitting randomness provided by the
bootloader or firmware to be credited as entropy. However, the fact
that the UEFI support code was already wired into the RNG subsystem
via a call to add_device_randomness() was overlooked, and so it was
not converted at the same time.
Note that this UEFI (v2.4 or newer) feature is currently only
implemented for EFI stub booting on ARM, and further note that
CONFIG_RANDOM_TRUST_BOOTLOADER must be enabled, and this should be
done only if there indeed is sufficient trust in the bootloader
_and_ its source of randomness.
Introducing a chosen node, rng-seed, which is an entropy that can be
passed to kernel called very early to increase initial device
randomness. Bootloader should provide this entropy and the value is
read from /chosen/rng-seed in DT.
Obtain of_fdt_crc32 for CRC check after early_init_dt_scan_nodes(),
since early_init_dt_scan_chosen() would modify fdt to erase rng-seed.
Add a new interface add_bootloader_randomness() for rng-seed use case.
Depends on whether the seed is trustworthy, rng seed would be passed to
add_hwgenerator_randomness(). Otherwise it would be passed to
add_device_randomness(). Decision is controlled by kernel config
RANDOM_TRUST_BOOTLOADER.
Signed-off-by: Hsin-Yi Wang <email address hidden>
Reviewed-by: Stephen Boyd <email address hidden>
Reviewed-by: Rob Herring <email address hidden>
Reviewed-by: Theodore Ts'o <email address hidden> # drivers/char/random.c
Signed-off-by: Will Deacon <email address hidden>
(cherry picked from commit 428826f5358c922dc378830a1717b682c0823160)
Signed-off-by: Kamal Mostafa <email address hidden>
Acked-by: Stefan Bader <email address hidden>
Acked-by: Connor Kuehl <email address hidden>
Signed-off-by: Khalid Elmously <email address hidden>
