Respect EFI block-io buffer alignment

[Leif Lindholm]

This resolves a complete failure to access devices connected to the
SATA port on the ARM ltd. Juno platform (apart from a violation of the
UEFI block io protocol).

The below is a bit of a hack, but I'd like some feedback on preferred
solution before over(or under)engineering something.

As far as I can tell, a struct_disk is only ever allocated in
kern/disk.c, using grub_zalloc(). So the only reason for the horrid
ifdefs is that there is no grub_memalign for EMU.

Do I:
- Keep the ifdefs?
- Implement grub_memalign() for EMU?
- Something else?

/
    Leif

>From 2d8b7ae2dd4c639252517e9a1df783ed0564c112 Mon Sep 17 00:00:00 2001
From: Leif Lindholm <address@hidden>
Date: Wed, 17 Feb 2016 15:33:47 +0000
Subject: [PATCH] efidisk: Respect block_io_protocol buffer alignment

Returned from the OpenProtocol operation, the grub_efi_block_io_media
structure contains the io_align field, specifying the minimum alignment
required for buffers used in any data transfers with the device.

Add an io_align field to struct grub_disk, and use it in kern/disk.c
when GRUB_MACHINE_EFI is defined.

Reported-by: Jeremy Linton <address@hidden>
---
 grub-core/disk/efi/efidisk.c | 1 +
 grub-core/kern/disk.c        | 9 +++++++++
 include/grub/disk.h          | 3 +++
 3 files changed, 13 insertions(+)

diff --git a/grub-core/disk/efi/efidisk.c b/grub-core/disk/efi/efidisk.c
index 1c00e3e..424ff92 100644
--- a/grub-core/disk/efi/efidisk.c
+++ b/grub-core/disk/efi/efidisk.c
@@ -495,6 +495,7 @@ grub_efidisk_open (const char *name, struct grub_disk *disk)
      and total sectors should be replaced with total blocks.  */
   grub_dprintf ("efidisk", "m = %p, last block = %llx, block size = %x\n",
                m, (unsigned long long) m->last_block, m->block_size);
+  disk->io_align = m->io_align;
   disk->total_sectors = m->last_block + 1;
   /* Don't increase this value due to bug in some EFI.  */
   disk->max_agglomerate = 0xa0000 >> (GRUB_DISK_CACHE_BITS + 
GRUB_DISK_SECTOR_BITS);
diff --git a/grub-core/kern/disk.c b/grub-core/kern/disk.c
index 789f8c0..27bef10 100644
--- a/grub-core/kern/disk.c
+++ b/grub-core/kern/disk.c
@@ -331,7 +331,12 @@ grub_disk_read_small_real (grub_disk_t disk, 
grub_disk_addr_t sector,
     }
 
   /* Allocate a temporary buffer.  */
+#ifdef GRUB_MACHINE_EFI
+  tmp_buf = grub_memalign (disk->io_align,
+                          GRUB_DISK_SECTOR_SIZE << GRUB_DISK_CACHE_BITS);
+#else
   tmp_buf = grub_malloc (GRUB_DISK_SECTOR_SIZE << GRUB_DISK_CACHE_BITS);
+#endif
   if (! tmp_buf)
     return grub_errno;
 
@@ -373,7 +378,11 @@ grub_disk_read_small_real (grub_disk_t disk, 
grub_disk_addr_t sector,
     num = ((size + offset + (1ULL << (disk->log_sector_size))
            - 1) >> (disk->log_sector_size));
 
+#ifdef GRUB_MACHINE_EFI
+    tmp_buf = grub_memalign (disk->io_align, num << disk->log_sector_size);
+#else
     tmp_buf = grub_malloc (num << disk->log_sector_size);
+#endif
     if (!tmp_buf)
       return grub_errno;
     
diff --git a/include/grub/disk.h b/include/grub/disk.h
index b385af8..b063bf6 100644
--- a/include/grub/disk.h
+++ b/include/grub/disk.h
@@ -126,6 +126,9 @@ struct grub_disk
   /* Logarithm of sector size.  */
   unsigned int log_sector_size;
 
+  /* Minimum read/write buffer alignment */
+  unsigned int io_align;
+
   /* Maximum number of sectors read divided by GRUB_DISK_CACHE_SIZE.  */
   unsigned int max_agglomerate;
 
-- 
2.1.4