[PATCH v2 07/10] cryptodisk: Replace some literals with constants in grub_cryptodisk_endecrypt.

[Glenn Washburn]

This should improve readability of code by providing clues as to what the
value represents.

Signed-off-by: Glenn Washburn <development@efficientek.com>
---
 grub-core/disk/cryptodisk.c | 12 +++++++-----
 include/grub/types.h        |  3 +++
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/grub-core/disk/cryptodisk.c b/grub-core/disk/cryptodisk.c
index 623f0f396..1a91c2d55 100644
--- a/grub-core/disk/cryptodisk.c
+++ b/grub-core/disk/cryptodisk.c
@@ -297,19 +297,21 @@ grub_cryptodisk_endecrypt (struct grub_cryptodisk *dev,
          }
          break;
        case GRUB_CRYPTODISK_MODE_IV_BYTECOUNT64:
-         iv[1] = grub_cpu_to_le32 (sector >> (32 - log_sector_size));
+         /* The IV is the 64 bit byte offset of the sector. */
+         iv[1] = grub_cpu_to_le32 (sector >> (GRUB_TYPE_BIT(iv[0])
+                                              - log_sector_size));
          iv[0] = grub_cpu_to_le32 ((sector << log_sector_size)
-                                   & 0xFFFFFFFF);
+                                   & GRUB_TYPE_MAX(iv[0]));
          break;
        case GRUB_CRYPTODISK_MODE_IV_BENBI:
          {
            grub_uint64_t num = (sector << dev->benbi_log) + 1;
-           iv[sz - 2] = grub_cpu_to_be32 (num >> 32);
-           iv[sz - 1] = grub_cpu_to_be32 (num & 0xFFFFFFFF);
+           iv[sz - 2] = grub_cpu_to_be32 (num >> GRUB_TYPE_BIT(iv[0]));
+           iv[sz - 1] = grub_cpu_to_be32 (num & GRUB_TYPE_MAX(iv[0]));
          }
          break;
        case GRUB_CRYPTODISK_MODE_IV_ESSIV:
-         iv[0] = grub_cpu_to_le32 (sector & 0xFFFFFFFF);
+         iv[0] = grub_cpu_to_le32 (sector & GRUB_TYPE_MAX(iv[0]));
          err = grub_crypto_ecb_encrypt (dev->essiv_cipher, iv, iv,
                                         dev->cipher->cipher->blocksize);
          if (err)
diff --git a/include/grub/types.h b/include/grub/types.h
index 035a4b528..8b4267ebd 100644
--- a/include/grub/types.h
+++ b/include/grub/types.h
@@ -319,4 +319,7 @@ static inline void grub_set_unaligned64 (void *ptr, 
grub_uint64_t val)
 
 #define GRUB_CHAR_BIT 8
 
+#define GRUB_TYPE_BIT(type) (sizeof(type) * GRUB_CHAR_BIT)
+#define GRUB_TYPE_MAX(type) ((2 * ((1ULL << (GRUB_TYPE_BIT(type) - 1)) - 1)) + 
1)
+
 #endif /* ! GRUB_TYPES_HEADER */
-- 
2.27.0