Attribute flags:
Bit 0 - System partition
+ Bit 1 - Hide from EFI
+ Bit 2 - Legacy BIOS bootable
+ Bit 48-63 - Defined and used by the individual partition type
+ For Basic data partition :
Bit 60 - Read-only
Bit 62 - Hidden
Bit 63 - Not mount
To restore GUID partition table one needs to:
1. Define partition layout in the environment.
Format of partitions layout:
- "partitions=uuid_disk=...;name=u-boot,size=60MiB,uuid=...;
+ "uuid_disk=...;name=u-boot,size=60MiB,uuid=...;
name=kernel,size=60MiB,uuid=...;"
or
- "partitions=uuid_disk=${uuid_gpt_disk};name=${uboot_name},
+ "uuid_disk=${uuid_gpt_disk};name=${uboot_name},
size=${uboot_size},uuid=${uboot_uuid};"
The fields 'name' and 'size' are mandatory for every partition.
The field 'start' is optional.
+ If field 'size' of the last partition is 0, the partition is extended
+ up to the end of the device.
+
The fields 'uuid' and 'uuid_disk' are optional if CONFIG_RANDOM_UUID is
enabled. A random uuid will be used if omitted or they point to an empty/
non-existent environment variable. The environment variable will be set to
- the generated UUID.
+ the generated UUID. The 'gpt guid' command reads the current value of the
+ uuid_disk from the GPT.
+
+ The field 'bootable' is optional, it is used to mark the GPT partition
+ bootable (set attribute flags "Legacy BIOS bootable").
+ "name=u-boot,size=60MiB;name=boot,size=60Mib,bootable;name=rootfs,size=0"
+ It can be used to locate bootable disks with command
+ "part list <interface> <dev> -bootable <varname>",
+ please check out doc/README.distro for use.
2. Define 'CONFIG_EFI_PARTITION' and 'CONFIG_CMD_GPT'
-2. From u-boot prompt type:
+3. From u-boot prompt type:
gpt write mmc 0 $partitions
+Checking (validating) GPT partitions in U-Boot:
+===============================================
+
+Procedure is the same as above. The only change is at point 3.
+
+At u-boot prompt one needs to write:
+ gpt verify mmc 0 [$partitions]
+
+where [$partitions] is an optional parameter.
+
+When it is not provided, only basic checks based on CRC32 calculation for GPT
+header and PTEs are performed.
+When provided, additionally partition data - name, size and starting
+offset (last two in LBA) - are compared with data defined in '$partitions'
+environment variable.
+
+After running this command, return code is set to 0 if no errors found in
+on non-volatile medium stored GPT.
+
+Following line can be used to assess if GPT verification has succeed:
+
+U-BOOT> gpt verify mmc 0 $partitions
+U-BOOT> if test $? = 0; then echo "GPT OK"; else echo "GPT ERR"; fi
+
+Renaming GPT partitions from U-Boot:
+====================================
+
+GPT partition names are a mechanism via which userspace and U-Boot can
+communicate about software updates and boot failure. The 'gpt guid',
+'gpt read', 'gpt rename' and 'gpt swap' commands facilitate
+programmatic renaming of partitions from bootscripts by generating and
+modifying the partitions layout string. Here is an illustration of
+employing 'swap' to exchange 'primary' and 'backup' partition names:
+
+U-BOOT> gpt swap mmc 0 primary backup
+
+Afterwards, all partitions previously named 'primary' will be named
+'backup', and vice-versa. Alternatively, single partitions may be
+renamed. In this example, mmc0's first partition will be renamed
+'primary':
+
+U-BOOT> gpt rename mmc 0 1 primary
+
+The GPT functionality may be tested with the 'sandbox' board by
+creating a disk image as described under 'Block Device Emulation' in
+board/sandbox/README.sandbox:
+
+=>host bind 0 ./disk.raw
+=> gpt read host 0
+[ . . . ]
+=> gpt swap host 0 name othername
+[ . . . ]
+
Partition type GUID:
====================
If you define 'CONFIG_PARTITION_TYPE_GUID', a optionnal parameter 'type'
can specify a other partition type guid:
- "partitions=uuid_disk=...;name=u-boot,size=60MiB,uuid=...;
+ "uuid_disk=...;name=u-boot,size=60MiB,uuid=...;
name=kernel,size=60MiB,uuid=...,
type=0FC63DAF-8483-4772-8E79-3D69D8477DE4;"
+Some strings can be also used at the place of known GUID :
+ "system" = PARTITION_SYSTEM_GUID
+ (C12A7328-F81F-11D2-BA4B-00A0C93EC93B)
+ "mbr" = LEGACY_MBR_PARTITION_GUID
+ (024DEE41-33E7-11D3-9D69-0008C781F39F)
+ "msft" = PARTITION_MSFT_RESERVED_GUID
+ (E3C9E316-0B5C-4DB8-817D-F92DF00215AE)
+ "data" = PARTITION_BASIC_DATA_GUID
+ (EBD0A0A2-B9E5-4433-87C0-68B6B72699C7)
+ "linux" = PARTITION_LINUX_FILE_SYSTEM_DATA_GUID
+ (0FC63DAF-8483-4772-8E79-3D69D8477DE4)
+ "raid" = PARTITION_LINUX_RAID_GUID
+ (A19D880F-05FC-4D3B-A006-743F0F84911E)
+ "swap" = PARTITION_LINUX_SWAP_GUID
+ (0657FD6D-A4AB-43C4-84E5-0933C84B4F4F)
+ "lvm" = PARTITION_LINUX_LVM_GUID
+ (E6D6D379-F507-44C2-A23C-238F2A3DF928)
+
+ "uuid_disk=...;name=u-boot,size=60MiB,uuid=...;
+ name=kernel,size=60MiB,uuid=...,type=linux;"
+
+They are also used to display the type of partition in "part list" command.
+
+
Useful info:
============