cgpt: Support non-standard (smaller) entries table

The standard says that entries table must be at least 16384 bytes. On
some of our devices, the NOR section is only 8 KiB and used to store
both primary and secondary tables. On this device, we can only store 24
entries.

Therefore, this CL adds support for non-standard entry table. It adjusts
the MIN_NUMBER_OF_ENTRIES to 16, and replaces GPT_ENTRIES_SECTORS with
CalculateEntriesSectors.

BUG=chromium:441812
BRANCH=none
TEST=unittest

Change-Id: I6b85b35ce5612c7abb22142f8252bd0d45b676c5
Reviewed-on: https://chromium-review.googlesource.com/234996
Reviewed-by: Bill Richardson <wfrichar@chromium.org>
Commit-Queue: Nam Nguyen <namnguyen@chromium.org>
Tested-by: Nam Nguyen <namnguyen@chromium.org>

8 files changed, 89 insertions, 48 deletions

diff --git a/cgpt/cgpt_common.c b/cgpt/cgpt_common.c
index b580e33a..ffaa3090 100644
--- a/cgpt/cgpt_common.c
+++ b/cgpt/cgpt_common.c
@@ -176,7 +176,8 @@ static int GptLoad(struct drive *drive, uint32_t sector_bytes) {
                   drive->gpt.flags) == 0) {
     if (CGPT_OK != Load(drive, &drive->gpt.primary_entries,
                         primary_header->entries_lba,
-                        drive->gpt.sector_bytes, GPT_ENTRIES_SECTORS)) {
+                        drive->gpt.sector_bytes,
+                        CalculateEntriesSectors(primary_header))) {
       Error("Cannot read primary partition entry array\n");
       return -1;
     }
@@ -189,7 +190,8 @@ static int GptLoad(struct drive *drive, uint32_t sector_bytes) {
                   drive->gpt.flags) == 0) {
     if (CGPT_OK != Load(drive, &drive->gpt.secondary_entries,
                         secondary_header->entries_lba,
-                        drive->gpt.sector_bytes, GPT_ENTRIES_SECTORS)) {
+                        drive->gpt.sector_bytes,
+                        CalculateEntriesSectors(secondary_header))) {
       Error("Cannot read secondary partition entry array\n");
       return -1;
     }
@@ -222,7 +224,8 @@ static int GptSave(struct drive *drive) {
   if (drive->gpt.modified & GPT_MODIFIED_ENTRIES1) {
     if (CGPT_OK != Save(drive, drive->gpt.primary_entries,
                         primary_header->entries_lba,
-                        drive->gpt.sector_bytes, GPT_ENTRIES_SECTORS)) {
+                        drive->gpt.sector_bytes,
+                        CalculateEntriesSectors(primary_header))) {
       errors++;
       Error("Cannot write primary entries: %s\n", strerror(errno));
     }
@@ -231,7 +234,8 @@ static int GptSave(struct drive *drive) {
   if (drive->gpt.modified & GPT_MODIFIED_ENTRIES2) {
     if (CGPT_OK != Save(drive, drive->gpt.secondary_entries,
                         secondary_header->entries_lba,
-                        drive->gpt.sector_bytes, GPT_ENTRIES_SECTORS)) {
+                        drive->gpt.sector_bytes,
+                        CalculateEntriesSectors(secondary_header))) {
       errors++;
       Error("Cannot write secondary entries: %s\n", strerror(errno));
     }
@@ -808,12 +812,16 @@ void UpdateCrc(GptData *gpt) {
   if (gpt->modified & GPT_MODIFIED_ENTRIES1 &&
       memcmp(primary_header, GPT_HEADER_SIGNATURE2,
              GPT_HEADER_SIGNATURE_SIZE)) {
+    size_t entries_size = primary_header->size_of_entry *
+        primary_header->number_of_entries;
     primary_header->entries_crc32 =
-        Crc32(gpt->primary_entries, TOTAL_ENTRIES_SIZE);
+        Crc32(gpt->primary_entries, entries_size);
   }
   if (gpt->modified & GPT_MODIFIED_ENTRIES2) {
+    size_t entries_size = secondary_header->size_of_entry *
+        secondary_header->number_of_entries;
     secondary_header->entries_crc32 =
-        Crc32(gpt->secondary_entries, TOTAL_ENTRIES_SIZE);
+        Crc32(gpt->secondary_entries, entries_size);
   }
   if (gpt->modified & GPT_MODIFIED_HEADER1) {
     primary_header->header_crc32 = 0;
@@ -867,17 +875,26 @@ uint8_t RepairEntries(GptData *gpt, const uint32_t valid_entries) {
   if (!memcmp(h->signature, GPT_HEADER_SIGNATURE2, GPT_HEADER_SIGNATURE_SIZE))
     return 0;
 
+  if (gpt->valid_headers & MASK_PRIMARY) {
+    h = (GptHeader*)gpt->primary_header;
+  } else if (gpt->valid_headers & MASK_SECONDARY) {
+    h = (GptHeader*)gpt->secondary_header;
+  } else {
+    /* We cannot trust any header, don't update entries. */
+    return 0;
+  }
+
+  size_t entries_size = h->number_of_entries * h->size_of_entry;
   if (valid_entries == MASK_BOTH) {
-    if (memcmp(gpt->primary_entries, gpt->secondary_entries,
-               TOTAL_ENTRIES_SIZE)) {
-      memcpy(gpt->secondary_entries, gpt->primary_entries, TOTAL_ENTRIES_SIZE);
+    if (memcmp(gpt->primary_entries, gpt->secondary_entries, entries_size)) {
+      memcpy(gpt->secondary_entries, gpt->primary_entries, entries_size);
       return GPT_MODIFIED_ENTRIES2;
     }
   } else if (valid_entries == MASK_PRIMARY) {
-    memcpy(gpt->secondary_entries, gpt->primary_entries, TOTAL_ENTRIES_SIZE);
+    memcpy(gpt->secondary_entries, gpt->primary_entries, entries_size);
     return GPT_MODIFIED_ENTRIES2;
   } else if (valid_entries == MASK_SECONDARY) {
-    memcpy(gpt->primary_entries, gpt->secondary_entries, TOTAL_ENTRIES_SIZE);
+    memcpy(gpt->primary_entries, gpt->secondary_entries, entries_size);
     return GPT_MODIFIED_ENTRIES1;
   }
 
@@ -922,7 +939,7 @@ uint8_t RepairHeader(GptData *gpt, const uint32_t valid_headers) {
     secondary_header->my_lba = gpt->gpt_drive_sectors - 1;  /* the last sector */
     secondary_header->alternate_lba = primary_header->my_lba;
     secondary_header->entries_lba = secondary_header->my_lba -
-        GPT_ENTRIES_SECTORS;
+        CalculateEntriesSectors(primary_header);
     return GPT_MODIFIED_HEADER2;
   } else if (valid_headers == MASK_SECONDARY) {
     memcpy(primary_header, secondary_header, sizeof(GptHeader));
diff --git a/cgpt/cgpt_create.c b/cgpt/cgpt_create.c
index 2265c8f9..64f3f4d2 100644
--- a/cgpt/cgpt_create.c
+++ b/cgpt/cgpt_create.c
@@ -29,10 +29,6 @@ static int GptCreate(struct drive *drive, CgptCreateParams *params) {
                 drive->gpt.sector_bytes * GPT_HEADER_SECTORS);
   AllocAndClear(&drive->gpt.secondary_header,
                 drive->gpt.sector_bytes * GPT_HEADER_SECTORS);
-  AllocAndClear(&drive->gpt.primary_entries,
-                drive->gpt.sector_bytes * GPT_ENTRIES_SECTORS);
-  AllocAndClear(&drive->gpt.secondary_entries,
-                drive->gpt.sector_bytes * GPT_ENTRIES_SECTORS);
 
   drive->gpt.modified |= (GPT_MODIFIED_HEADER1 | GPT_MODIFIED_ENTRIES1 |
                          GPT_MODIFIED_HEADER2 | GPT_MODIFIED_ENTRIES2);
@@ -45,21 +41,12 @@ static int GptCreate(struct drive *drive, CgptCreateParams *params) {
     h->size = sizeof(GptHeader);
     h->my_lba = GPT_PMBR_SECTORS;  /* The second sector on drive. */
     h->alternate_lba = drive->gpt.gpt_drive_sectors - GPT_HEADER_SECTORS;
-    h->entries_lba = h->my_lba + GPT_HEADER_SECTORS;
-    if (!(drive->gpt.flags & GPT_FLAG_EXTERNAL)) {
-      h->entries_lba += params->padding;
-      h->first_usable_lba = h->entries_lba + GPT_ENTRIES_SECTORS;
-      h->last_usable_lba = (drive->gpt.streaming_drive_sectors -
-			    GPT_HEADER_SECTORS -
-                            GPT_ENTRIES_SECTORS - 1);
-    } else {
-      h->first_usable_lba = params->padding;
-      h->last_usable_lba = (drive->gpt.streaming_drive_sectors - 1);
-    }
     if (CGPT_OK != GenerateGuid(&h->disk_uuid)) {
       Error("Unable to generate new GUID.\n");
       return -1;
     }
+
+    /* Calculate number of entries */
     h->size_of_entry = sizeof(GptEntry);
     h->number_of_entries = TOTAL_ENTRIES_SIZE / h->size_of_entry;
     if (drive->gpt.flags & GPT_FLAG_EXTERNAL) {
@@ -69,7 +56,7 @@ static int GptCreate(struct drive *drive, CgptCreateParams *params) {
         Error("Not enough space for a GPT header.\n");
         return -1;
       }
-      half_size_sectors -= GPT_HEADER_SECTORS;
+      half_size_sectors -= (GPT_HEADER_SECTORS + GPT_PMBR_SECTORS);
       size_t half_size = half_size_sectors * drive->gpt.sector_bytes;
       if (half_size < (MIN_NUMBER_OF_ENTRIES * h->size_of_entry)) {
         Error("Not enough space for minimum number of entries.\n");
@@ -80,6 +67,22 @@ static int GptCreate(struct drive *drive, CgptCreateParams *params) {
       }
     }
 
+    /* Then use number of entries to calculate entries_lba. */
+    h->entries_lba = h->my_lba + GPT_HEADER_SECTORS;
+    if (!(drive->gpt.flags & GPT_FLAG_EXTERNAL)) {
+      h->entries_lba += params->padding;
+      h->first_usable_lba = h->entries_lba + CalculateEntriesSectors(h);
+      h->last_usable_lba = (drive->gpt.streaming_drive_sectors - GPT_HEADER_SECTORS -
+                            CalculateEntriesSectors(h) - 1);
+    } else {
+      h->first_usable_lba = params->padding;
+      h->last_usable_lba = (drive->gpt.streaming_drive_sectors - 1);
+    }
+
+    size_t entries_size = h->number_of_entries * h->size_of_entry;
+    AllocAndClear(&drive->gpt.primary_entries, entries_size);
+    AllocAndClear(&drive->gpt.secondary_entries, entries_size);
+
     // Copy to secondary
     RepairHeader(&drive->gpt, MASK_PRIMARY);
 
diff --git a/cgpt/cgpt_show.c b/cgpt/cgpt_show.c
index 68a185cb..143b5fa1 100644
--- a/cgpt/cgpt_show.c
+++ b/cgpt/cgpt_show.c
@@ -271,7 +271,7 @@ static int GptShow(struct drive *drive, CgptShowParams *params) {
 
     GptHeader* primary_header = (GptHeader*)drive->gpt.primary_header;
     printf(GPT_FMT, (int)primary_header->entries_lba,
-           (int)GPT_ENTRIES_SECTORS,
+           (int)CalculateEntriesSectors(primary_header),
            drive->gpt.valid_entries & MASK_PRIMARY ? "" : "INVALID",
            "Pri GPT table");
 
@@ -282,7 +282,7 @@ static int GptShow(struct drive *drive, CgptShowParams *params) {
     /****************************** Secondary *************************/
     GptHeader* secondary_header = (GptHeader*)drive->gpt.secondary_header;
     printf(GPT_FMT, (int)secondary_header->entries_lba,
-           (int)GPT_ENTRIES_SECTORS,
+           (int)CalculateEntriesSectors(secondary_header),
            drive->gpt.valid_entries & MASK_SECONDARY ? "" : "INVALID",
            "Sec GPT table");
     /* We show secondary table details if any of following is true.
@@ -294,7 +294,8 @@ static int GptShow(struct drive *drive, CgptShowParams *params) {
         ((drive->gpt.valid_entries & MASK_SECONDARY) &&
          (!(drive->gpt.valid_entries & MASK_PRIMARY) ||
           memcmp(drive->gpt.primary_entries, drive->gpt.secondary_entries,
-                 TOTAL_ENTRIES_SIZE)))) {
+                 secondary_header->number_of_entries *
+                 secondary_header->size_of_entry)))) {
       EntriesDetails(drive, SECONDARY, params->numeric);
     }
 
diff --git a/firmware/lib/cgptlib/cgptlib_internal.c b/firmware/lib/cgptlib/cgptlib_internal.c
index 5e2889c6..6a89d841 100644
--- a/firmware/lib/cgptlib/cgptlib_internal.c
+++ b/firmware/lib/cgptlib/cgptlib_internal.c
@@ -12,11 +12,18 @@
 #include "gpt_misc.h"
 #include "utility.h"
 
+const static int SECTOR_SIZE = 512;
+
+size_t CalculateEntriesSectors(GptHeader* h) {
+  size_t bytes = h->number_of_entries * h->size_of_entry;
+  size_t ret = (bytes + SECTOR_SIZE - 1) / SECTOR_SIZE;
+  return ret;
+}
 
 int CheckParameters(GptData *gpt)
 {
 	/* Currently, we only support 512-byte sectors. */
-	if (gpt->sector_bytes != 512)
+	if (gpt->sector_bytes != SECTOR_SIZE)
 		return GPT_ERROR_INVALID_SECTOR_SIZE;
 
 	/*
@@ -33,9 +40,11 @@ int CheckParameters(GptData *gpt)
 	/*
 	 * Sector count of a drive should be reasonable. If the given value is
 	 * too small to contain basic GPT structure (PMBR + Headers + Entries),
-	 * the value is wrong.
+	 * the value is wrong. Entries size is hard coded to TOTAL_ENTRIES_SIZE (see
+	 * cgpt_create.c). This check is only applicable when GPT is stored on device.
 	 */
-	if (gpt->gpt_drive_sectors < (1 + 2 * (1 + GPT_ENTRIES_SECTORS)))
+	if (!(gpt->flags & GPT_FLAG_EXTERNAL) &&
+		gpt->gpt_drive_sectors < (1 + 2 * (1 + TOTAL_ENTRIES_SIZE / SECTOR_SIZE)))
 		return GPT_ERROR_INVALID_SECTOR_NUMBER;
 
 	return GPT_SUCCESS;
@@ -105,7 +114,7 @@ int CheckHeader(GptHeader *h, int is_secondary,
 	if (is_secondary) {
 		if (h->my_lba != gpt_drive_sectors - GPT_HEADER_SECTORS)
 			return 1;
-		if (h->entries_lba != h->my_lba - GPT_ENTRIES_SECTORS)
+		if (h->entries_lba != h->my_lba - CalculateEntriesSectors(h))
 			return 1;
 	} else {
 		if (h->my_lba != GPT_PMBR_SECTORS)
@@ -131,10 +140,10 @@ int CheckHeader(GptHeader *h, int is_secondary,
 	 * array.
 	 */
 	/* TODO(namnguyen): Also check for padding between header & entries. */
-	if (h->first_usable_lba < 2 + GPT_ENTRIES_SECTORS)
+	if (h->first_usable_lba < 2 + CalculateEntriesSectors(h))
 		return 1;
 	if (h->last_usable_lba >=
-			streaming_drive_sectors - 1 - GPT_ENTRIES_SECTORS)
+			streaming_drive_sectors - 1 - CalculateEntriesSectors(h))
 		return 1;
 
 	/* Success */
@@ -321,7 +330,7 @@ void GptRepair(GptData *gpt)
 		Memcpy(header2, header1, sizeof(GptHeader));
 		header2->my_lba = gpt->gpt_drive_sectors - GPT_HEADER_SECTORS;
 		header2->alternate_lba = GPT_PMBR_SECTORS;  /* Second sector. */
-		header2->entries_lba = header2->my_lba - GPT_ENTRIES_SECTORS;
+		header2->entries_lba = header2->my_lba - CalculateEntriesSectors(header1);
 		header2->header_crc32 = HeaderCrc(header2);
 		gpt->modified |= GPT_MODIFIED_HEADER2;
 	}
diff --git a/firmware/lib/cgptlib/include/cgptlib_internal.h b/firmware/lib/cgptlib/include/cgptlib_internal.h
index f88bc567..b4e2f5f9 100644
--- a/firmware/lib/cgptlib/include/cgptlib_internal.h
+++ b/firmware/lib/cgptlib/include/cgptlib_internal.h
@@ -51,17 +51,12 @@
 #define MIN_SIZE_OF_ENTRY 128
 #define MAX_SIZE_OF_ENTRY 512
 #define SIZE_OF_ENTRY_MULTIPLE 8
-#define MIN_NUMBER_OF_ENTRIES 32
+#define MIN_NUMBER_OF_ENTRIES 16
 #define MAX_NUMBER_OF_ENTRIES 512
 
 /* Defines GPT sizes */
 #define GPT_PMBR_SECTORS 1  /* size (in sectors) of PMBR */
 #define GPT_HEADER_SECTORS 1
-/*
- * Entries sectors assumes sector size if 512 bytes; then (TOTAL_ENTRIES_SIZE /
- * 512) = 32
- */
-#define GPT_ENTRIES_SECTORS 32
 
 /*
  * Alias name of index in internal array for primary and secondary header and
@@ -163,4 +158,9 @@ void GetCurrentKernelUniqueGuid(GptData *gpt, void *dest);
  */
 const char *GptErrorText(int error_code);
 
+/**
+ * Return number of 512-byte sectors required to store the entries table.
+ */
+size_t CalculateEntriesSectors(GptHeader* h);
+
 #endif /* VBOOT_REFERENCE_CGPTLIB_INTERNAL_H_ */
diff --git a/tests/cgptlib_test.c b/tests/cgptlib_test.c
index e81f50e7..759fa500 100644
--- a/tests/cgptlib_test.c
+++ b/tests/cgptlib_test.c
@@ -247,7 +247,7 @@ static int ParameterTests(void)
 		{512, 0, GPT_ERROR_INVALID_SECTOR_NUMBER},
 		{512, 66, GPT_ERROR_INVALID_SECTOR_NUMBER},
 		{512, GPT_PMBR_SECTORS + GPT_HEADER_SECTORS * 2 +
-		 GPT_ENTRIES_SECTORS * 2, GPT_SUCCESS},
+		 TOTAL_ENTRIES_SIZE / DEFAULT_SECTOR_SIZE * 2, GPT_SUCCESS},
 		{4096, DEFAULT_DRIVE_SECTORS, GPT_ERROR_INVALID_SECTOR_SIZE},
 	};
 	int i;
@@ -537,6 +537,8 @@ static int NumberOfPartitionEntriesTest(void)
 	BuildTestGptData(gpt);
 	h1->number_of_entries--;
 	h2->number_of_entries /= 2;
+	/* Because we halved h2 entries, its entries_lba is going to change. */
+	h2->entries_lba = h2->my_lba - CalculateEntriesSectors(h2);
 	RefreshCrc32(gpt);
 	EXPECT(1 == CheckHeader(h1, 0, gpt->streaming_drive_sectors, gpt->gpt_drive_sectors, 0));
 	EXPECT(1 == CheckHeader(h2, 1, gpt->streaming_drive_sectors, gpt->gpt_drive_sectors, 0));
@@ -1460,6 +1462,9 @@ static int CheckHeaderOffDevice()
 
 	BuildTestGptData(gpt);
 	secondary_header->number_of_entries = 100;
+	/* Because we change number of entries, we need to also update entrie_lba. */
+	secondary_header->entries_lba = secondary_header->my_lba -
+		CalculateEntriesSectors(secondary_header);
 	RefreshCrc32(gpt);
 	EXPECT(1 == CheckHeader(secondary_header, 1, gpt->streaming_drive_sectors,
 		gpt->gpt_drive_sectors, 0));
diff --git a/tests/run_cgpt_tests.sh b/tests/run_cgpt_tests.sh
index 6619a6b8..7170eef8 100755
--- a/tests/run_cgpt_tests.sh
+++ b/tests/run_cgpt_tests.sh
@@ -291,12 +291,17 @@ $CGPT find $MTD -t kernel ${DEV} >/dev/null
 
 # Enable write access again to test boundary in off device storage
 chmod 600 ${DEV}
+# Create a small 8K file to simulate Flash NOR section
+dd if=/dev/zero of=${DEV} bs=8K count=1
 # Drive size is not multiple of 512
 assert_fail $CGPT create -D 511 ${DEV}
 assert_fail $CGPT create -D 513 ${DEV}
 MTD="-D 1024"
 # Create a GPT table for a device of 1024 bytes (2 sectors)
 $CGPT create $MTD ${DEV}
+# Make sure number of entries is reasonable for 8KiB GPT
+X=$($CGPT show -D 1024 -d ${DEV} | grep -c "Number of entries: 24")
+[ "$X" = "2" ] || error
 # This fails because header verification is off due to different drive size
 assert_fail $CGPT show ${DEV}
 # But this passes because we pass in correct drive size
@@ -306,6 +311,7 @@ assert_fail $CGPT add $MTD -b 2 -s 1 -t data ${DEV}
 # This fails because partition size is over the size of the device
 assert_fail $CGPT add $MTD -b 0 -s 3 -t data ${DEV}
 
+
 echo "Done."
 
 happy "All tests passed."
diff --git a/tests/vboot_kernel_tests.c b/tests/vboot_kernel_tests.c
index 6f47ae35..41ac7add 100644
--- a/tests/vboot_kernel_tests.c
+++ b/tests/vboot_kernel_tests.c
@@ -87,14 +87,14 @@ static void SetupGptHeader(GptHeader *h, int is_secondary)
 	/* Set LBA pointers for primary or secondary header */
 	if (is_secondary) {
 		h->my_lba = MOCK_SECTOR_COUNT - GPT_HEADER_SECTORS;
-		h->entries_lba = h->my_lba - GPT_ENTRIES_SECTORS;
+		h->entries_lba = h->my_lba - CalculateEntriesSectors(h);
 	} else {
 		h->my_lba = GPT_PMBR_SECTORS;
 		h->entries_lba = h->my_lba + 1;
 	}
 
-	h->first_usable_lba = 2 + GPT_ENTRIES_SECTORS;
-	h->last_usable_lba = MOCK_SECTOR_COUNT - 2 - GPT_ENTRIES_SECTORS;
+	h->first_usable_lba = 2 + CalculateEntriesSectors(h);
+	h->last_usable_lba = MOCK_SECTOR_COUNT - 2 - CalculateEntriesSectors(h);
 
 	h->header_crc32 = HeaderCrc(h);
 }