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https://github.com/Telecominfraproject/OpenCellular.git
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962483c1e2
There were two changes. First, we need to pack the GPT header to make it match the spec (duh). Second, there's a subtle bug in how the BIOS recovers from corrupted headers. The EFI spec says that the primary GPT header must be at sector 1 (counting from zero) and the secondary GPT header must be at the last sector on the drive. The BIOS correctly looks in those locations to find the headers. However, if the secondary GPT header is invalid (as it usually is due to our build process), the BIOS is supposed to update it from the primary header. In this case, rather than write to the last sector on the drive where it just looked, the BIOS trusts the alternate_lba field of the primary header. That field is supposed to point to the secondary header location, but the BIOS just blindly uses it no matter where it points. The cgpt tool wasn't initializing that field, so it pointed to sector 0, which is the PMBR. The BIOS overwrote that, resulting in an unbootable drive. Review URL: http://codereview.chromium.org/2844006
105 lines
3.4 KiB
C
105 lines
3.4 KiB
C
/* Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*
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* Defines EFI related structure. See more details in EFI 2.3 spec.
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*
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* To download EFI standard, please visit UEFI homepage:
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* http://www.uefi.org/
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*/
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#ifndef VBOOT_REFERENCE_CGPTLIB_GPT_H_
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#define VBOOT_REFERENCE_CGPTLIB_GPT_H_
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#include <stdint.h>
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#define GPT_HEADER_SIGNATURE "EFI PART"
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#define GPT_HEADER_SIGNATURE_SIZE sizeof(GPT_HEADER_SIGNATURE)
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#define GPT_HEADER_REVISION 0x00010000
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/* The first 3 numbers should be stored in network-endian format
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* according to the GUID RFC. The UEFI spec appendix A claims they
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* should be stored in little-endian format. But they need to be
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* _displayed_ in network-endian format, which is also how they're
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* documented in the specs.
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*
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* Since what we have here are little-endian constants, they're
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* byte-swapped from the normal display order. */
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#define GPT_ENT_TYPE_UNUSED \
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{{{0x00000000,0x0000,0x0000,0x00,0x00,{0x00,0x00,0x00,0x00,0x00,0x00}}}}
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#define GPT_ENT_TYPE_EFI \
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{{{0xc12a7328,0xf81f,0x11d2,0xba,0x4b,{0x00,0xa0,0xc9,0x3e,0xc9,0x3b}}}}
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#define GPT_ENT_TYPE_CHROMEOS_KERNEL \
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{{{0xfe3a2a5d,0x4f32,0x41a7,0xb7,0x25,{0xac,0xcc,0x32,0x85,0xa3,0x09}}}}
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#define GPT_ENT_TYPE_CHROMEOS_ROOTFS \
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{{{0x3cb8e202,0x3b7e,0x47dd,0x8a,0x3c,{0x7f,0xf2,0xa1,0x3c,0xfc,0xec}}}}
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#define GPT_ENT_TYPE_CHROMEOS_RESERVED \
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{{{0x2e0a753d,0x9e48,0x43b0,0x83,0x37,{0xb1,0x51,0x92,0xcb,0x1b,0x5e}}}}
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#define GPT_ENT_TYPE_LINUX_DATA \
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{{{0xebd0a0a2,0xb9e5,0x4433,0x87,0xc0,{0x68,0xb6,0xb7,0x26,0x99,0xc7}}}}
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#define UUID_NODE_LEN 6
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#define GUID_SIZE 16
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/* GUID definition.
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* Defined in appendix A of EFI standard.
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*/
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typedef struct {
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union {
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struct {
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uint32_t time_low;
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uint16_t time_mid;
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uint16_t time_high_and_version;
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uint8_t clock_seq_high_and_reserved;
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uint8_t clock_seq_low;
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uint8_t node[UUID_NODE_LEN];
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} Uuid;
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uint8_t raw[GUID_SIZE];
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} u;
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} __attribute__((packed)) Guid;
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/* Some constant values */
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extern const Guid guid_unused;
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extern const Guid guid_chromeos_kernel;
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/* GPT header defines how many partitions exist on a drive and sectors managed.
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* For every drive device, there are 2 headers, primary and secondary.
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* Most of fields are duplicated except my_lba and entries_lba.
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*
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* You may find more details in chapter 5 of EFI standard.
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*/
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typedef struct {
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char signature[8];
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uint32_t revision;
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uint32_t size;
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uint32_t header_crc32;
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uint32_t reserved_zero;
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uint64_t my_lba;
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uint64_t alternate_lba;
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uint64_t first_usable_lba;
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uint64_t last_usable_lba;
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Guid disk_uuid;
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uint64_t entries_lba;
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uint32_t number_of_entries;
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uint32_t size_of_entry;
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uint32_t entries_crc32;
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uint8_t reserved_padding[]; /* entire sector reserved for header */
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} __attribute__((packed)) GptHeader;
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/* GPT partition entry defines the starting and ending LBAs of a partition.
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* It also contains the unique GUID, type, and attribute bits.
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*
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* You may find more details in chapter 5 of EFI standard.
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*/
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typedef struct {
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Guid type;
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Guid unique;
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uint64_t starting_lba;
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uint64_t ending_lba;
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uint64_t attributes;
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uint16_t name[36]; /* UTF-16 encoded partition name */
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uint8_t reserved[]; /* nothing, really */
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} __attribute__((packed)) GptEntry;
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#endif /* VBOOT_REFERENCE_CGPTLIB_GPT_H_ */
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