1 #-
2 # Copyright (c) 2007 Yahoo!, Inc.
3 # All rights reserved.
4 # Written by: John Baldwin <jhb@FreeBSD.org>
5 #
6 # Redistribution and use in source and binary forms, with or without
7 # modification, are permitted provided that the following conditions
8 # are met:
9 # 1. Redistributions of source code must retain the above copyright
10 # notice, this list of conditions and the following disclaimer.
11 # 2. Redistributions in binary form must reproduce the above copyright
12 # notice, this list of conditions and the following disclaimer in the
13 # documentation and/or other materials provided with the distribution.
14 # 3. Neither the name of the author nor the names of any co-contributors
15 # may be used to endorse or promote products derived from this software
16 # without specific prior written permission.
17 #
18 # THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
19 # ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 # ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
22 # FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 # OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 # HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 # OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 # SUCH DAMAGE.
29 #
30 # $FreeBSD: releng/10.4/sys/boot/i386/pmbr/pmbr.s 239060 2012-08-05 12:57:38Z ae $
31 #
32 # Partly from: src/sys/boot/i386/mbr/mbr.s 1.7
33
34 # A 512 byte PMBR boot manager that looks for a FreeBSD boot GPT partition
35 # and boots it.
36
37 .set LOAD,0x7c00 # Load address
38 .set EXEC,0x600 # Execution address
39 .set MAGIC,0xaa55 # Magic: bootable
40 .set SECSIZE,0x200 # Size of a single disk sector
41 .set DISKSIG,440 # Disk signature offset
42 .set STACK,EXEC+SECSIZE*4 # Stack address
43 .set GPT_ADDR,STACK # GPT header address
44 .set GPT_SIG,0
45 .set GPT_SIG_0,0x20494645 # "EFI "
46 .set GPT_SIG_1,0x54524150 # "PART"
47 .set GPT_MYLBA,24
48 .set GPT_PART_LBA,72
49 .set GPT_NPART,80
50 .set GPT_PART_SIZE,84
51 .set PART_ADDR,GPT_ADDR+SECSIZE # GPT partition array address
52 .set PART_TYPE,0
53 .set PART_START_LBA,32
54 .set PART_END_LBA,40
55 .set DPBUF,PART_ADDR+SECSIZE
56 .set DPBUF_SEC,0x10 # Number of sectors
57
58 .set NHRDRV,0x475 # Number of hard drives
59
60 .globl start # Entry point
61 .code16
62
63 #
64 # Setup the segment registers for flat addressing and setup the stack.
65 #
66 start: cld # String ops inc
67 xorw %ax,%ax # Zero
68 movw %ax,%es # Address
69 movw %ax,%ds # data
70 movw %ax,%ss # Set up
71 movw $STACK,%sp # stack
72 #
73 # Relocate ourself to a lower address so that we have more room to load
74 # other sectors.
75 #
76 movw $main-EXEC+LOAD,%si # Source
77 movw $main,%di # Destination
78 movw $SECSIZE-(main-start),%cx # Byte count
79 rep # Relocate
80 movsb # code
81 #
82 # Jump to the relocated code.
83 #
84 jmp main-LOAD+EXEC # To relocated code
85 #
86 # Validate drive number in %dl.
87 #
88 main: cmpb $0x80,%dl # Drive valid?
89 jb main.1 # No
90 movb NHRDRV,%dh # Calculate the highest
91 addb $0x80,%dh # drive number available
92 cmpb %dh,%dl # Within range?
93 jb main.2 # Yes
94 main.1: movb $0x80,%dl # Assume drive 0x80
95 #
96 # Load the GPT header and verify signature. Try LBA 1 for the primary one and
97 # the last LBA for the backup if it is broken.
98 #
99 main.2: call getdrvparams # Read drive parameters
100 movb $1,%dh # %dh := 1 (reading primary)
101 main.2a: movw $GPT_ADDR,%bx
102 movw $lba,%si
103 call read # Read header and check GPT sig
104 cmpl $GPT_SIG_0,GPT_ADDR+GPT_SIG
105 jnz main.2b
106 cmpl $GPT_SIG_1,GPT_ADDR+GPT_SIG+4
107 jnz main.2b
108 jmp load_part
109 main.2b: cmpb $1,%dh # Reading primary?
110 jne err_pt # If no - invalid table found
111 #
112 # Try alternative LBAs from the last sector for the GPT header.
113 #
114 main.3: movb $0,%dh # %dh := 0 (reading backup)
115 movw $DPBUF+DPBUF_SEC,%si # %si = last sector + 1
116 movw $lba,%di # %di = $lba
117 main.3a: decl (%si) # 0x0(%si) = last sec (0-31)
118 movw $2,%cx
119 rep
120 movsw # $lastsec--, copy it to $lba
121 jmp main.2a # Read the next sector
122 #
123 # Load a partition table sector from disk and look for a FreeBSD boot
124 # partition.
125 #
126 load_part: movw $GPT_ADDR+GPT_PART_LBA,%si
127 movw $PART_ADDR,%bx
128 call read
129 scan: movw %bx,%si # Compare partition UUID
130 movw $boot_uuid,%di # with FreeBSD boot UUID
131 movb $0x10,%cl
132 repe cmpsb
133 jnz next_part # Didn't match, next partition
134 #
135 # We found a boot partition. Load it into RAM starting at 0x7c00.
136 #
137 movw %bx,%di # Save partition pointer in %di
138 leaw PART_START_LBA(%di),%si
139 movw $LOAD/16,%bx
140 movw %bx,%es
141 xorw %bx,%bx
142 load_boot: push %si # Save %si
143 call read
144 pop %si # Restore
145 movl PART_END_LBA(%di),%eax # See if this was the last LBA
146 cmpl (%si),%eax
147 jnz next_boot
148 movl PART_END_LBA+4(%di),%eax
149 cmpl 4(%si),%eax
150 jnz next_boot
151 mov %bx,%es # Reset %es to zero
152 jmp LOAD # Jump to boot code
153 next_boot: incl (%si) # Next LBA
154 adcl $0,4(%si)
155 mov %es,%ax # Adjust segment for next
156 addw $SECSIZE/16,%ax # sector
157 cmp $0x9000,%ax # Don't load past 0x90000,
158 jae err_big # 545k should be enough for
159 mov %ax,%es # any boot code. :)
160 jmp load_boot
161 #
162 # Move to the next partition. If we walk off the end of the sector, load
163 # the next sector. We assume that partition entries are smaller than 64k
164 # and that they won't span a sector boundary.
165 #
166 # XXX: Should we int 0x18 instead of err_noboot if we hit the end of the table?
167 #
168 next_part: decl GPT_ADDR+GPT_NPART # Was this the last partition?
169 jz err_noboot
170 movw GPT_ADDR+GPT_PART_SIZE,%ax
171 addw %ax,%bx # Next partition
172 cmpw $PART_ADDR+0x200,%bx # Still in sector?
173 jb scan
174 incl GPT_ADDR+GPT_PART_LBA # Next sector
175 adcl $0,GPT_ADDR+GPT_PART_LBA+4
176 jmp load_part
177 #
178 # Load a sector (64-bit LBA at %si) from disk %dl into %es:%bx by creating
179 # a EDD packet on the stack and passing it to the BIOS. Trashes %ax and %si.
180 #
181 read: pushl 0x4(%si) # Set the LBA
182 pushl 0x0(%si) # address
183 pushw %es # Set the address of
184 pushw %bx # the transfer buffer
185 pushw $0x1 # Read 1 sector
186 pushw $0x10 # Packet length
187 movw %sp,%si # Packer pointer
188 movw $0x4200,%ax # BIOS: LBA Read from disk
189 int $0x13 # Call the BIOS
190 add $0x10,%sp # Restore stack
191 jc err_rd # If error
192 ret
193 #
194 # Check the number of LBAs on the drive index %dx. Trashes %ax and %si.
195 #
196 getdrvparams:
197 movw $DPBUF,%si # Set the address of result buf
198 movw $0x001e,(%si) # len
199 movw $0x4800,%ax # BIOS: Read Drive Parameters
200 int $0x13 # Call the BIOS
201 jc err_rd # "I/O error" if error
202 ret
203 #
204 # Various error message entry points.
205 #
206 err_big: movw $msg_big,%si # "Boot loader too
207 jmp putstr # large"
208
209 err_pt: movw $msg_pt,%si # "Invalid partition
210 jmp putstr # table"
211
212 err_rd: movw $msg_rd,%si # "I/O error loading
213 jmp putstr # boot loader"
214
215 err_noboot: movw $msg_noboot,%si # "Missing boot
216 jmp putstr # loader"
217 #
218 # Output an ASCIZ string to the console via the BIOS.
219 #
220 putstr.0: movw $0x7,%bx # Page:attribute
221 movb $0xe,%ah # BIOS: Display
222 int $0x10 # character
223 putstr: lodsb # Get character
224 testb %al,%al # End of string?
225 jnz putstr.0 # No
226 putstr.1: jmp putstr.1 # Await reset
227
228 msg_big: .asciz "Boot loader too large"
229 msg_pt: .asciz "Invalid partition table"
230 msg_rd: .asciz "I/O error loading boot loader"
231 msg_noboot: .asciz "Missing boot loader"
232
233 lba: .quad 1 # LBA of GPT header
234
235 boot_uuid: .long 0x83bd6b9d
236 .word 0x7f41
237 .word 0x11dc
238 .byte 0xbe
239 .byte 0x0b
240 .byte 0x00
241 .byte 0x15
242 .byte 0x60
243 .byte 0xb8
244 .byte 0x4f
245 .byte 0x0f
246
247 .org DISKSIG,0x90
248 sig: .long 0 # OS Disk Signature
249 .word 0 # "Unknown" in PMBR
250
251 partbl: .fill 0x10,0x4,0x0 # Partition table
252 .word MAGIC # Magic number
Cache object: fe5e37fd2f464ec9f6271757f9ee955c
|