[PATCH v2 00/10] efi/libstub: Avoid UTF-16 conversion busywork

[Ard Biesheuvel]

From: Ard Biesheuvel <ardb@xxxxxxxxxx>

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@xxxxxxxxxx>
Cc: x86@xxxxxxxxxx

[0] https://lore.kernel.org/all/20260906130817.1151961-9-ardb@xxxxxxxxxx

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