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disk: part_efi: add support for the Backup GPT

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Check the Backup GPT table if the Primary GPT table is invalid.
Renamed "Secondary GPT" to "Backup GPT" as per:
  UEFI Specification (Version 2.3.1, Errata A)

Signed-off-by: Steve Rae <srae@broadcom.com>
This commit is contained in:
Steve Rae
2014-05-05 13:00:08 -07:00
committed by Tom Rini
parent fa39ffe5d6
commit ae95fad5af
2 changed files with 26 additions and 10 deletions
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14
doc/README.gpt
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@@ -66,14 +66,14 @@ GPT brief explanation:
|Partition n |
| |
----------------------------------------------------------
LBA -34 |Entry 1|Entry 2| Entry 3| Entry 4| Secondary
-------------------------------------------------- (bkp)
LBA -33 |Entries 5 - 128 | GPT
LBA -34 |Entry 1|Entry 2| Entry 3| Entry 4| Backup
-------------------------------------------------- GPT
LBA -33 |Entries 5 - 128 |
| |
| |
LBA -2 | |
--------------------------------------------------
LBA -1 |Secondary GPT Header |
LBA -1 |Backup GPT Header |
----------------------------------------------------------
For a legacy reasons, GPT's LBA 0 sector has a MBR structure. It is called
@@ -86,7 +86,7 @@ It is possible to define 128 linearly placed partition entries.
"LBA -1" means the last addressable block (in the mmc subsystem:
"dev_desc->lba - 1")
Primary/Secondary GPT header:
Primary/Backup GPT header:
----------------------------
Offset Size Description
@@ -115,7 +115,7 @@ IMPORTANT:
GPT headers and partition entries are protected by CRC32 (the POSIX CRC32).
Primary GPT header and Secondary GPT header have swapped values of "Current LBA"
Primary GPT header and Backup GPT header have swapped values of "Current LBA"
and "Backup LBA" and therefore different CRC32 check-sum.
CRC32 for GPT headers (field "CRC of header") are calculated up till
@@ -125,7 +125,7 @@ CRC32 for partition entries (field "CRC32 of partition array") is calculated for
the whole array entry ( Number_of_partition_entries *
sizeof(partition_entry_size (usually 128)))
Observe, how Secondary GPT is placed in the memory. It is NOT a mirror reflect
Observe, how Backup GPT is placed in the memory. It is NOT a mirror reflect
of the Primary.
Partition Entry Format: