[PATCH 2/2] efidisk: respect block_io_protocol minimum buffer alignment

[Leif Lindholm <leif.lindholm@linaro.org>]

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.

Implement a driver-specific malloc function that allocates a buffer
with the required alignment. Also verify on open that the alignment
value is valid, or return failure.
---
 grub-core/disk/efi/efidisk.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/grub-core/disk/efi/efidisk.c b/grub-core/disk/efi/efidisk.c
index 1c00e3e..9b42585 100644
--- a/grub-core/disk/efi/efidisk.c
+++ b/grub-core/disk/efi/efidisk.c
@@ -457,6 +457,13 @@ get_device (struct grub_efidisk_data *devices, int num)
   return 0;
 }
 
+static void *
+aligned_malloc (struct grub_disk *disk, grub_size_t size)
+{
+  struct grub_efidisk_data *d = disk->data;
+  return grub_memalign (d->block_io->media->io_align, size);
+}
+
 static grub_err_t
 grub_efidisk_open (const char *name, struct grub_disk *disk)
 {
@@ -493,8 +500,15 @@ grub_efidisk_open (const char *name, struct grub_disk *disk)
   m = d->block_io->media;
   /* FIXME: Probably it is better to store the block size in the 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);
+  grub_dprintf ("efidisk",
+               "m = %p, last block = %llx, block size = %x, io align = %x\n",
+               m, (unsigned long long) m->last_block, m->block_size,
+               m->io_align);
+
+  /* Ensure required buffer alignment is a power of two (or is zero). */
+  if (m->io_align & (m->io_align - 1))
+    return grub_error (GRUB_ERR_IO, "invalid buffer alignment %d", 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);
@@ -505,6 +519,7 @@ grub_efidisk_open (const char *name, struct grub_disk *disk)
        (1U << disk->log_sector_size) < m->block_size;
        disk->log_sector_size++);
   disk->data = d;
+  disk->malloc = aligned_malloc;
 
   grub_dprintf ("efidisk", "opening %s succeeded\n", name);
 
-- 
2.1.4