linux-kernel - [PATCH 0/2] x86, efi/random: invoke EFI_RNG

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Date:   Wed,  6 Nov 2019 08:06:11 +0100
From:   Dominik Brodowski <linux@...inikbrodowski.net>
To:     linux-kernel@...r.kernel.org
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Kees Cook <keescook@...omium.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Rob Herring <robh@...nel.org>, Theodore Ts'o <tytso@....edu>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-efi@...r.kernel.org,
        Mario Limonciello <Mario.Limonciello@...l.com>
Subject: [PATCH 0/2] x86, efi/random: invoke EFI_RNG_PROTOCOL in the x86 EFI stub

EFI v2.4 and later may provide for a EFI_RNG_PROTOCOL, which can be called
from the EFI stubs to seed the kernel entropy pool. So far, this feature has
only been implemented on arm/arm64. This series makes the relevant EFI
libstub code arch-independent and enables the feature also on x86.

Please note that this feature only works if Linux is booted as an EFI stub,
and that the EFI-provided randomness is not credited as entropy unless
RANDOM_TRUST_BOOTLOADER is set.

Thanks to Ard Biesheuvel for his hints on how to test the EFI_RNG_PROTOCOL
from the UEFI shell ( RngTest-X64.efi ), and especially to Mario Limonciello:
he gave me highly useful hints on the implementation of the EFI_RNG_PROTOCOL
which ultimately helped me to determine why the earlier RFC patch did not
work out as expected.

The patches are also available in the Git repository at:

  https://git.kernel.org/pub/scm/linux/kernel/git/brodo/linux.git/ random

Dominik Brodowski (2):
  efi/random: use arch-independent efi_call_proto()
  x86: efi/random: Invoke EFI_RNG_PROTOCOL to seed the UEFI RNG table

 arch/x86/boot/compressed/eboot.c       |  3 +++
 drivers/firmware/efi/libstub/Makefile  |  5 +++--
 drivers/firmware/efi/libstub/efistub.h |  2 --
 drivers/firmware/efi/libstub/random.c  | 21 ++++++++++++++++-----
 include/linux/efi.h                    |  2 ++
 5 files changed, 24 insertions(+), 9 deletions(-)

-- 
2.24.0