0004-gpt-record-size-of-of-the-entries-table.patch

From b78d543b0ab493f6bd20f2e5d101fc11c9357faf Mon Sep 17 00:00:00 2001
From: Michael Marineau <michael.marineau@coreos.com>
Date: Sat, 18 Oct 2014 16:46:17 -0700
Subject: [PATCH] gpt: record size of of the entries table

The size of the entries table will be needed later when writing it back
to disk. Restructure the entries reading code to flow a little better.
---
 grub-core/lib/gpt.c          | 53 ++++++++++++++++--------------------
 include/grub/gpt_partition.h |  5 +++-
 2 files changed, 27 insertions(+), 31 deletions(-)

diff --git a/grub-core/lib/gpt.c b/grub-core/lib/gpt.c
index 705bd77f9..01df7f3e8 100644
--- a/grub-core/lib/gpt.c
+++ b/grub-core/lib/gpt.c
@@ -153,7 +153,7 @@ grub_gpt_read_backup (grub_disk_t disk, grub_gpt_t gpt)
   return GRUB_ERR_NONE;
 }
 
-static struct grub_gpt_partentry *
+static grub_err_t
 grub_gpt_read_entries (grub_disk_t disk, grub_gpt_t gpt,
 		       struct grub_gpt_header *header)
 {
@@ -173,6 +173,10 @@ grub_gpt_read_entries (grub_disk_t disk, grub_gpt_t gpt,
       goto fail;
     }
 
+  /* Double check that the header was validated properly.  */
+  if (entries_size < GRUB_GPT_DEFAULT_ENTRIES_SIZE)
+    return grub_error (GRUB_ERR_BUG, "invalid GPT entries table size");
+
   entries = grub_malloc (entries_size);
   if (!entries)
     goto fail;
@@ -197,19 +201,21 @@ grub_gpt_read_entries (grub_disk_t disk, grub_gpt_t gpt,
     }
 
   grub_free (crc32_context);
-  return entries;
+  grub_free (gpt->entries);
+  gpt->entries = entries;
+  gpt->entries_size = entries_size;
+  return GRUB_ERR_NONE;
 
 fail:
   grub_free (entries);
   grub_free (crc32_context);
-  return NULL;
+  return grub_errno;
 }
 
 grub_gpt_t
 grub_gpt_read (grub_disk_t disk)
 {
   grub_gpt_t gpt;
-  struct grub_gpt_partentry *backup_entries;
 
   gpt = grub_zalloc (sizeof (*gpt));
   if (!gpt)
@@ -241,36 +247,23 @@ grub_gpt_read (grub_disk_t disk)
   else
     goto fail;
 
-  /* Same error handling scheme for the entry tables.  */
-  gpt->entries = grub_gpt_read_entries (disk, gpt, &gpt->primary);
-  if (!gpt->entries)
-    {
-      grub_error_push ();
-      backup_entries = grub_gpt_read_entries (disk, gpt, &gpt->backup);
-      grub_error_pop ();
-    }
-  else
-    {
-      gpt->status |= GRUB_GPT_PRIMARY_ENTRIES_VALID;
-      backup_entries = grub_gpt_read_entries (disk, gpt, &gpt->backup);
-    }
+  /* Similarly, favor the value or error from the primary table.  */
+  if (gpt->status & GRUB_GPT_BACKUP_HEADER_VALID &&
+      !grub_gpt_read_entries (disk, gpt, &gpt->backup))
+    gpt->status |= GRUB_GPT_BACKUP_ENTRIES_VALID;
 
-  if (backup_entries)
-    {
-      gpt->status |= GRUB_GPT_BACKUP_ENTRIES_VALID;
-
-      if (gpt->status & GRUB_GPT_PRIMARY_ENTRIES_VALID)
-	grub_free (backup_entries);
-      else
-	gpt->entries = backup_entries;
-    }
+  grub_errno = GRUB_ERR_NONE;
+  if (gpt->status & GRUB_GPT_PRIMARY_HEADER_VALID &&
+      !grub_gpt_read_entries (disk, gpt, &gpt->primary))
+    gpt->status |= GRUB_GPT_PRIMARY_ENTRIES_VALID;
 
   if (gpt->status & GRUB_GPT_PRIMARY_ENTRIES_VALID ||
       gpt->status & GRUB_GPT_BACKUP_ENTRIES_VALID)
-    {
-      grub_errno = GRUB_ERR_NONE;
-      return gpt;
-    }
+    grub_errno = GRUB_ERR_NONE;
+  else
+    goto fail;
+
+  return gpt;
 
 fail:
   grub_gpt_free (gpt);
diff --git a/include/grub/gpt_partition.h b/include/grub/gpt_partition.h
index 6d678fae2..451b02a89 100644
--- a/include/grub/gpt_partition.h
+++ b/include/grub/gpt_partition.h
@@ -106,7 +106,9 @@ typedef enum grub_gpt_status
 
 /* UEFI requires the entries table to be at least 16384 bytes for a
  * total of 128 entries given the standard 128 byte entry size.  */
-#define GRUB_GPT_DEFAULT_ENTRIES_LENGTH	128
+#define GRUB_GPT_DEFAULT_ENTRIES_SIZE	16384
+#define GRUB_GPT_DEFAULT_ENTRIES_LENGTH	\
+  (GRUB_GPT_DEFAULT_ENTRIES_SIZE / sizeof (struct grub_gpt_partentry))
 
 struct grub_gpt
 {
@@ -122,6 +124,7 @@ struct grub_gpt
 
   /* Only need one entries table, on disk both copies are identical.  */
   struct grub_gpt_partentry *entries;
+  grub_size_t entries_size;
 
   /* Logarithm of sector size, in case GPT and disk driver disagree.  */
   unsigned int log_sector_size;