linux-kernel - [RFC PATCH 0/3] Remove unused EFI runtime APIs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250714060843.4029171-5-ardb+git@google.com>
Date: Mon, 14 Jul 2025 08:08:44 +0200
From: Ard Biesheuvel <ardb+git@...gle.com>
To: linux-kernel@...r.kernel.org
Cc: linux-arm-kernel@...ts.infradead.org, Ard Biesheuvel <ardb@...nel.org>, 
	Heinrich Schuchardt <heinrich.schuchardt@...onical.com>, Feng Tang <feng.tang@...ux.alibaba.com>, 
	Alexandre Belloni <alexandre.belloni@...tlin.com>, Juergen Gross <jgross@...e.com>, 
	Stefano Stabellini <sstabellini@...nel.org>, 
	Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>, Sunil V L <sunilvl@...tanamicro.com>, 
	Bibo Mao <maobibo@...ngson.cn>, linux-rtc@...r.kernel.org, linux-efi@...r.kernel.org, 
	xen-devel@...ts.xenproject.org, x86@...nel.org, 
	linux-riscv@...ts.infradead.org, loongarch@...ts.linux.dev
Subject: [RFC PATCH 0/3] Remove unused EFI runtime APIs

From: Ard Biesheuvel <ardb@...nel.org>

Using EFI runtime services to program the RTC to wake up the system is
supported in theory, but rarely works in practice. Fortunately, this
functionality is rarely [if ever] used to begin with so we can just drop
it. (Note that the EFI rtc driver is not used by x86, which programs the
CMOS rtc directly)

The same applies to GetNextHighMonoCount(), which, if implemented,
usually relies on SetVariable() under the hood *, which is often not
supported at runtime by non-x86 platforms. But it has no known users
either so let's drop support for it as well.

This means we need to drop the slightly pointless tests for it too.

* EDK2 based EFI implementations usually have a MTC variable carrying
  the monotonic counter variable, which is therefore not truly
  monotonic, given that SetVariable() will happily overwrite it. 

Cc: Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
Cc: Feng Tang <feng.tang@...ux.alibaba.com>
Cc: Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: Stefano Stabellini <sstabellini@...nel.org>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com> 
Cc: Sunil V L <sunilvl@...tanamicro.com>
Cc: Bibo Mao <maobibo@...ngson.cn>
Cc: linux-rtc@...r.kernel.org
Cc: linux-efi@...r.kernel.org
Cc: xen-devel@...ts.xenproject.org
Cc: x86@...nel.org
Cc: linux-riscv@...ts.infradead.org
Cc: loongarch@...ts.linux.dev

Ard Biesheuvel (3):
  efi-rtc: Remove wakeup functionality
  efi/test: Don't bother pseudo-testing unused EFI services
  efi: Remove support for pointless, unused EFI services

 arch/x86/platform/efi/efi_64.c          |  22 ----
 drivers/firmware/efi/runtime-wrappers.c |  68 ------------
 drivers/firmware/efi/test/efi_test.c    | 108 +-------------------
 drivers/rtc/rtc-efi.c                   |  76 +-------------
 drivers/xen/efi.c                       |  56 ----------
 include/linux/efi.h                     |   6 --
 6 files changed, 4 insertions(+), 332 deletions(-)

-- 
2.50.0.727.gbf7dc18ff4-goog