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[PATCH v2 0/7] support >512b sector disks with old/buggy firmware

From: Mihai Moldovan
Subject: [PATCH v2 0/7] support >512b sector disks with old/buggy firmware
Date: Sun, 24 May 2020 14:25:10 +0200

This is a patch series enabling successful boots on machines with
old/buggy system firmware that always assumes that hardware is using
512-bytes sectors, but more modern disks (e.g., 4Kn disks).

I will not get into the details in that cover letter, since the commits
themselves are supposed to be verbosely explaining what has been done
and why exactly, including proper comments within the code,  but I will
give a short summary of the user-visible features:
  - it works for me (yay!)
  - only x86 is supported, the SPARC core.img writing code is so
    different and weird that was I not able to merge the changes to
    both platforms (and OFW probably does not suffer from these
    problems anyway)
  - as a drive-by fix, stop allocating RS codes space on SPARC which
    cannot use it
  - adds disk sector size autodetection in the biosdisk module
  - adds a new, documented command line option --emu-512b that spaces
    out core.img in such a way that these buggy machines can read it
    correctly and enables the former mentioned disk sector size
  - as another drive-by fix, make the diskfilter debug output more

This stuff is not perfect and it likely also cannot be:
  - the disk sector size autodetection relies on content being
    *different* in the first two sectors of a disk, so it will fail to
    detect the sector size if, for example, the disk is empty
  - the last few sectors on a disk will not be readable if the system
    firmware is not very lenient.

Lastly, most of this stuff is opt-in. Users will need to explicitly
pass the new --emu-512b option to grub-install to get the new behavior.
This will also automatically set the biosdisk_autodetect_sector_size
environment variable in core.img's embedded config file. The
environment variable seems to stick after loading the actual (menu)
config file.

  - unbreak SPARC due to a very, very, very stupid typo
  - fix a few typos in GPT code comments.

Mihai Moldovan (7):
  biosdisk: autodetect hardware sector size (opt-in)
  biosdisk: restore LBA mode after read/write failures
  setup: add support for native sector addressing w/ 512-bytes lengths
  grub-install: hook up --emu-512b to sector size autodetection in
  docs/grub: document --emu-512b install option
  diskfilter: write out currently scanned partition
  gpt: respect native sector size if set/detected

 docs/grub.texi                    |  15 +
 grub-core/disk/diskfilter.c       |  54 ++-
 grub-core/disk/i386/pc/biosdisk.c | 642 +++++++++++++++++++++++++++++-
 grub-core/disk/ldm.c              |  10 +-
 grub-core/fs/btrfs.c              |   9 +-
 grub-core/fs/zfs/zfs.c            |   9 +-
 grub-core/partmap/gpt.c           |  79 +++-
 grub-core/partmap/msdos.c         |  30 +-
 include/grub/emu/hostdisk.h       |   3 +-
 include/grub/fs.h                 |   3 +-
 include/grub/i386/pc/biosdisk.h   |   3 +
 include/grub/partition.h          |   3 +-
 include/grub/util/install.h       |   4 +-
 util/grub-install.c               |  44 +-
 util/grub-setup.c                 |  10 +-
 util/setup.c                      | 349 ++++++++++++++--
 16 files changed, 1204 insertions(+), 63 deletions(-)


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