Improve GRUB2 boot to also adhere UEFI spec (#1830) (#1893)

buildroot-external/patches/grub2/0003-efidisk-pass-buffers-with-higher-alignment.patch

@@ -1,7 +1,7 @@
-From 74d815143bb9b504fb54d3eaf0ed3e382b26000a Mon Sep 17 00:00:00 2001
-Message-Id: <74d815143bb9b504fb54d3eaf0ed3e382b26000a.1651759401.git.stefan@agner.ch>
-In-Reply-To: <184b6a054e04bb4c7fb4885a30d62314229dc551.1651759401.git.stefan@agner.ch>
-References: <184b6a054e04bb4c7fb4885a30d62314229dc551.1651759401.git.stefan@agner.ch>
+From e3c27254802e1d7ebaa64df8edb93b0a899f1678 Mon Sep 17 00:00:00 2001
+Message-Id: <e3c27254802e1d7ebaa64df8edb93b0a899f1678.1652212828.git.stefan@agner.ch>
+In-Reply-To: <184b6a054e04bb4c7fb4885a30d62314229dc551.1652212828.git.stefan@agner.ch>
+References: <184b6a054e04bb4c7fb4885a30d62314229dc551.1652212828.git.stefan@agner.ch>
 From: Stefan Agner <stefan@agner.ch>
 Date: Thu, 5 May 2022 15:46:51 +0200
 Subject: [PATCH] efidisk: pass buffers with higher alignment
@@ -14,12 +14,18 @@ That particular system has IoAlign set to 2, and sometimes returns
 status 7 when buffers with alignment of 2 are passed. Things seem
 to work fine with buffers aligned to 4 bytes.
 
-It seems that IoAlign > 1 means 2 ^ IoAlign. There is also such a hint
-in an example printed in the Driver Writer's Guide:
+It seems that some system interpret IoAlign > 1 to mean 2 ^ IoAlign.
+There is also such a hint in an example printed in the Driver Writer's
+Guide:
 ScsiPassThruMode.IoAlign = 2; // Data must be alligned on 4-byte boundary
 
-Pass 2 ^ IoAlign aligned buffers to make sure GRUB2 works properly on
-all systems.
+However, some systems (e.g. U-Boot and some drivers in EDK II) do follow
+the UEFI specification.
+
+Work around by using an alignment of at least 512 bytes in case
+alignment is requested. Also make sure that IoAlign is still respected
+as per UEFI specification if a higher alignment than block size is
+requested.
 
 Note: The problem has only noticed with compressed squashfs. It seems
 that ext4 (and presumably other file system drivers) pass buffers with
@@ -27,32 +33,38 @@ a higher alignment already.
 
 Signed-off-by: Stefan Agner <stefan@agner.ch>
 ---
- grub-core/disk/efi/efidisk.c | 12 ++++++++++--
- 1 file changed, 10 insertions(+), 2 deletions(-)
+ grub-core/disk/efi/efidisk.c | 18 ++++++++++++++++--
+ 1 file changed, 16 insertions(+), 2 deletions(-)
 
 diff --git a/grub-core/disk/efi/efidisk.c b/grub-core/disk/efi/efidisk.c
-index 9e20af70e..eaf22367f 100644
+index 9e20af70e..c4eb4f4e7 100644
 --- a/grub-core/disk/efi/efidisk.c
 +++ b/grub-core/disk/efi/efidisk.c
-@@ -553,8 +553,16 @@ grub_efidisk_readwrite (struct grub_disk *disk, grub_disk_addr_t sector,
+@@ -553,8 +553,22 @@ grub_efidisk_readwrite (struct grub_disk *disk, grub_disk_addr_t sector,
    d = disk->data;
    bio = d->block_io;
  
 -  /* Set alignment to 1 if 0 specified */
 -  io_align = bio->media->io_align ? bio->media->io_align : 1;
 +  /*
-+   * If IoAlign is > 1, it means alignment by 2^IoAlign
-+   * Note: UEFI spec claims alignment by IoAlign. But there are systems
-+   * with IoAlign=2 which return status 7 if 2 bytes aligned buffers are
-+   * passed.
++   * If IoAlign is > 1, it should represent the required alignment. However,
++   * some UEFI implementation on Intel NUC systems seem to use IoAlign=2 but
++   * require 2^IoAlign.
++   * Make sure to align to at least block size if IO alignment is required.
 +   */
 +  if (bio->media->io_align > 1)
-+    io_align = 1 << bio->media->io_align;
++    {
++      if (bio->media->io_align < bio->media->block_size)
++        io_align = bio->media->block_size;
++      else
++        io_align = bio->media->io_align;
++    }
 +  else
 +    io_align = 1;
++
    num_bytes = size << disk->log_sector_size;
  
    if ((grub_addr_t) buf & (io_align - 1))
 -- 
-2.36.0
+2.36.1