[RFC] random: UEFI RNG input is bootloader randomness

[Dominik Brodowski]

Depending on RANDOM_TRUST_BOOTLOADER, bootloader-provided randomness
is credited as entropy. As the UEFI seeding entropy pool is seeded by
the UEFI firmware/bootloader, add its content as bootloader randomness.

Note that this UEFI (v2.4 or newer) feature is currently only
implemented for EFI stub booting on ARM, and further note that
RANDOM_TRUST_BOOTLOADER must only be enabled if there indeed is
sufficient trust in the bootloader _and_ its source of randomness.

Signed-off-by: Dominik Brodowski <li...@dominikbrodowski.net>
Cc: Ard Biesheuvel <ard.biesheu...@linaro.org>
Cc: Hsin-Yi Wang <hsi...@chromium.org>
Cc: Stephen Boyd <swb...@chromium.org>
Cc: Rob Herring <r...@kernel.org>
Cc: Theodore Ts'o <ty...@mit.edu>
Cc: Lee, Chun-Yi <joeyli.ker...@gmail.com>

---

Untested patch, as efi_random_get_seed() is only hooked up on ARM,
and the firmware on my old x86 laptop only has UEFI v2.31 anyway.

Thanks,
        Dominik

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 8f1ab04f6743..db0bffce754e 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -545,7 +545,7 @@ int __init efi_config_parse_tables(void *config_tables, int 
count, int sz,
                                              sizeof(*seed) + size);
                        if (seed != NULL) {
                                pr_notice("seeding entropy pool\n");
-                               add_device_randomness(seed->bits, seed->size);
+                               add_bootloader_randomness(seed->bits, 
seed->size);
                                early_memunmap(seed, sizeof(*seed) + size);
                        } else {
                                pr_err("Could not map UEFI random seed!\n");