1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
|
#!/usr/bin/env python3
# This file is part of the coreboot project.
#
# SPDX-License-Identifier: GPL-2.0-only
import sys, os, struct, uuid, zlib, io
# This script wraps the bootblock in a GPT partition, because that's what
# SiFive's bootrom will load.
# Size of a GPT disk block, in bytes
BLOCK_SIZE = 512
BLOCK_MASK = BLOCK_SIZE - 1
# Size of the bootcode part of the MBR
MBR_BOOTCODE_SIZE = 0x1be
# MBR trampoline to bootblock
MBR_BOOTCODE = bytes([
# j pc + 0x0800
0x6f, 0x00, 0x10, 0x00,
])
# A protecive MBR, without the bootcode part
PROTECTIVE_MBR_FOOTER = bytes([
0x00, 0x00, 0x02, 0x00, 0xee, 0xff, 0xff, 0xff,
0x01, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x55, 0xaa
])
# A "protective MBR"[1], which may also contain some boot code.
# [1]: https://en.wikipedia.org/wiki/GUID_Partition_Table#PROTECTIVE-MBR
class ProtectiveMBR:
def __init__(self):
self.bootcode = MBR_BOOTCODE + bytes(MBR_BOOTCODE_SIZE - len(MBR_BOOTCODE))
def generate(self, stream):
assert len(self.bootcode) == MBR_BOOTCODE_SIZE
mbr = self.bootcode + PROTECTIVE_MBR_FOOTER
assert len(mbr) == BLOCK_SIZE
stream.write(mbr)
# Generate a GUID from a string
class GUID(uuid.UUID):
def __init__(self, string):
super().__init__(string)
def get_bytes(self):
return self.bytes_le
DUMMY_GUID_DISK_UNIQUE = GUID('17145242-abaa-441d-916a-3f26c970aba2')
DUMMY_GUID_PART_UNIQUE = GUID('7552133d-c8de-4a20-924c-0e85f5ea81f2')
GUID_TYPE_FSBL = GUID('5B193300-FC78-40CD-8002-E86C45580B47')
# A GPT disk header
# https://en.wikipedia.org/wiki/GUID_Partition_Table#Partition_table_header_(LBA_1)
class GPTHeader:
def __init__(self):
self.current_lba = 1
self.backup_lba = 1
self.first_usable_lba = 2
self.last_usable_lba = 0xff # dummy value
self.uniq = DUMMY_GUID_DISK_UNIQUE
self.part_entries_lba = 2
self.part_entries_number = 0
self.part_entries_crc32 = 0
self.part_entry_size = 128
def pack_with_crc(self, crc):
header_size = 92
header = struct.pack('<8sIIIIQQQQ16sQIII',
b'EFI PART', 0x10000, header_size, crc, 0,
self.current_lba, self.backup_lba, self.first_usable_lba,
self.last_usable_lba, self.uniq.get_bytes(),
self.part_entries_lba, self.part_entries_number,
self.part_entry_size, self.part_entries_crc32)
assert len(header) == header_size
return header
def generate(self, stream):
crc = zlib.crc32(self.pack_with_crc(0))
header = self.pack_with_crc(crc)
stream.write(header.ljust(BLOCK_SIZE, b'\0'))
# A GPT partition entry.
# https://en.wikipedia.org/wiki/GUID_Partition_Table#Partition_entries_(LBA_2-33)
class GPTPartition:
def __init__(self):
self.type = GUID('00000000-0000-0000-0000-000000000000')
self.uniq = GUID('00000000-0000-0000-0000-000000000000')
self.first_lba = 0
self.last_lba = 0
self.attr = 0
self.name = ''
def generate(self, stream):
name_utf16 = self.name.encode('UTF-16LE')
part = struct.pack('<16s16sQQQ72s',
self.type.get_bytes(), self.uniq.get_bytes(),
self.first_lba, self.last_lba, self.attr,
name_utf16.ljust(72, b'\0'))
assert len(part) == 128
stream.write(part)
class GPTImage:
# The final image consists of:
# - A protective MBR
# - A GPT header
# - A few GPT partition entries
# - The content of the bootblock
def __init__(self):
self.mbr = ProtectiveMBR()
self.header = GPTHeader()
self.partitions = [ GPTPartition() for i in range(8) ]
self.bootblock = b''
# Fix up a few numbers to ensure consistency between the different
# components.
def fixup(self):
# Align the bootblock to a whole number to LBA blocks
bootblock_size = (len(self.bootblock) + BLOCK_SIZE - 1) & ~BLOCK_MASK
self.bootblock = self.bootblock.ljust(bootblock_size)
# Propagate the number of partition entries
self.header.part_entries_number = len(self.partitions)
self.header.first_usable_lba = 2 + self.header.part_entries_number // 4
# Create a partition entry for the bootblock
self.partitions[0].type = GUID_TYPE_FSBL
self.partitions[0].uniq = DUMMY_GUID_PART_UNIQUE
self.partitions[0].first_lba = self.header.first_usable_lba
self.partitions[0].last_lba = \
self.header.first_usable_lba + bootblock_size // BLOCK_SIZE
# Calculate the CRC32 checksum of the partitions array
partition_array = io.BytesIO()
for part in self.partitions:
part.generate(partition_array)
self.header.part_entries_crc32 = zlib.crc32(partition_array.getvalue())
def generate(self, stream):
self.mbr.generate(stream)
self.header.generate(stream)
for part in self.partitions:
part.generate(stream)
stream.write(self.bootblock)
if __name__ == '__main__':
if len(sys.argv) != 3:
print('Usage:', file=sys.stderr)
print(' %s bootblock.raw.bin bootblock.bin' % sys.argv[0],
file=sys.stderr)
sys.exit(1)
image = GPTImage()
with open(sys.argv[1], 'rb') as f:
image.bootblock = f.read()
image.fixup()
# Verify if first partition is at expected lba, otherwise trampoline will
# fail
if image.partitions[0].first_lba != 4:
print('Warning: First partition not at expected location (LBA 4)')
sys.exit(1)
with open(sys.argv[2], 'wb') as f:
image.generate(f)
|
