From: Ard Biesheuvel <ardb+git@google.com>
To: linux-efi@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, Ard Biesheuvel <ardb@kernel.org>,
Vincent Mailhol <mailhol@kernel.org>,
x86@kernel.org
Subject: [PATCH v2 00/10] efi/libstub: Avoid UTF-16 conversion busywork
Date: Wed, 9 Sep 2026 13:55:31 +0200 [thread overview]
Message-ID: <20260909115530.1924665-12-ardb+git@google.com> (raw)
From: Ard Biesheuvel <ardb@kernel.org>
The EFI libstub performs some redundant conversions between UTF-16 and
UTF-8 and back again, which includes dealing with surrogate pairs, which
UEFI implementations themselves simply ignore.
So drop all the homegrown code, and use the existing UCS-2 (== UTF-16
without surrogate pairs) library code where conversion to UTF-8 is
actually needed (the kernel command line).
The remaining handling involves the EFI console, which supports wide
characters natively, so just use those directly.
Changes since v1 [0]:
- drop size limit from ucs2_strscpy() instead of just the WARN()
- suppress modinfo sections from ucs2_string when __DISABLE_EXPORTS is
defined
- allow the input limit and max output size to be passed separately to
ucs2_to_utf8()
- reimplement efi_convert_cmdline() to optimize the common case, and
only process the input character by character if its size exceeds
COMMAND_LINE_SIZE
- use memcpy() to avoid strscpy() semantics in handling of %ls
- incorporate Vincent's patch (which inspired this work) for
completeness
Cc: Vincent Mailhol <mailhol@kernel.org>
Cc: x86@kernel.org
[0] https://lore.kernel.org/all/20260906130817.1151961-9-ardb@kernel.org
Ard Biesheuvel (9):
x86/boot: Drop pointless re-implementation of panic()
lib/ucs2_string: Drop arbitrary input size limit and associated WARN()
lib/ucs2_string: Suppress modinfo when __DISABLE_EXPORTS is set
lib/ucs2_string: Split out ucs2_as_utf8_l() taking a separate limit
efi/libstub: Use ucs2_string library for UTF-16 to UTF-8 conversion
efi/libstub: Avoid efi_puts() for compile time constant strings
efi/libstub: Output UTF-16 directly from vsnprintf()
efi/libstub: Add support for printing human readable GUIDs
efi/libstub: Add efi_snprintf() to construct wide strings
Vincent Mailhol (1):
efi/libstub: add initial Boot Loader Interface support
arch/x86/boot/compressed/error.c | 19 ---
arch/x86/boot/compressed/error.h | 1 -
arch/x86/boot/compressed/mem.c | 2 +-
drivers/firmware/efi/libstub/Makefile | 3 +-
drivers/firmware/efi/libstub/bli.c | 87 ++++++++++++
drivers/firmware/efi/libstub/efi-stub-helper.c | 100 +++++--------
drivers/firmware/efi/libstub/efi-stub.c | 1 +
drivers/firmware/efi/libstub/efistub.h | 8 +-
drivers/firmware/efi/libstub/gop.c | 6 +-
drivers/firmware/efi/libstub/printk.c | 95 ++-----------
drivers/firmware/efi/libstub/vsprintf.c | 150 +++++++-------------
drivers/firmware/efi/libstub/x86-stub.c | 1 +
include/linux/efi.h | 22 +++
include/linux/ucs2_string.h | 11 +-
lib/ucs2_string.c | 10 +-
15 files changed, 241 insertions(+), 275 deletions(-)
create mode 100644 drivers/firmware/efi/libstub/bli.c
--
2.55.0.1003.g10538fe699-goog
next reply other threads:[~2026-09-09 11:55 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-09 11:55 Ard Biesheuvel [this message]
2026-09-09 11:55 ` [PATCH v2 01/10] x86/boot: Drop pointless re-implementation of panic() Ard Biesheuvel
2026-09-09 19:14 ` Borislav Petkov
2026-09-09 20:43 ` Ard Biesheuvel
2026-09-10 13:12 ` Kiryl Shutsemau
2026-09-11 7:32 ` Ard Biesheuvel
2026-09-09 11:55 ` [PATCH v2 02/10] lib/ucs2_string: Drop arbitrary input size limit and associated WARN() Ard Biesheuvel
2026-09-09 11:55 ` [PATCH v2 03/10] lib/ucs2_string: Suppress modinfo when __DISABLE_EXPORTS is set Ard Biesheuvel
2026-09-09 11:55 ` [PATCH v2 04/10] lib/ucs2_string: Split out ucs2_as_utf8_l() taking a separate limit Ard Biesheuvel
2026-09-09 11:55 ` [PATCH v2 05/10] efi/libstub: Use ucs2_string library for UTF-16 to UTF-8 conversion Ard Biesheuvel
2026-09-09 11:55 ` [PATCH v2 06/10] efi/libstub: Avoid efi_puts() for compile time constant strings Ard Biesheuvel
2026-09-09 11:55 ` [PATCH v2 07/10] efi/libstub: Output UTF-16 directly from vsnprintf() Ard Biesheuvel
2026-09-09 11:55 ` [PATCH v2 08/10] efi/libstub: Add support for printing human readable GUIDs Ard Biesheuvel
2026-09-09 11:55 ` [PATCH v2 09/10] efi/libstub: Add efi_snprintf() to construct wide strings Ard Biesheuvel
2026-09-09 11:55 ` [PATCH v2 10/10] efi/libstub: add initial Boot Loader Interface support Ard Biesheuvel
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