Cross Reference: /freebsd-11.0-release/sys/boot/i386/cdboot/cdboot.S

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cdboot.S (130943)	cdboot.S (157652)
1# 2# Copyright (c) 2001 John Baldwin <jhb@FreeBSD.org> 3# All rights reserved. 4# 5# Redistribution and use in source and binary forms, with or without 6# modification, are permitted provided that the following conditions 7# are met: 8# 1. Redistributions of source code must retain the above copyright 9# notice, this list of conditions and the following disclaimer. 10# 2. Redistributions in binary form must reproduce the above copyright 11# notice, this list of conditions and the following disclaimer in the 12# documentation and/or other materials provided with the distribution. 13# 3. Neither the name of the author nor the names of any co-contributors 14# may be used to endorse or promote products derived from this software 15# without specific prior written permission. 16# 17# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20# ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27# SUCH DAMAGE. 28# 29	1# 2# Copyright (c) 2001 John Baldwin <jhb@FreeBSD.org> 3# All rights reserved. 4# 5# Redistribution and use in source and binary forms, with or without 6# modification, are permitted provided that the following conditions 7# are met: 8# 1. Redistributions of source code must retain the above copyright 9# notice, this list of conditions and the following disclaimer. 10# 2. Redistributions in binary form must reproduce the above copyright 11# notice, this list of conditions and the following disclaimer in the 12# documentation and/or other materials provided with the distribution. 13# 3. Neither the name of the author nor the names of any co-contributors 14# may be used to endorse or promote products derived from this software 15# without specific prior written permission. 16# 17# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20# ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27# SUCH DAMAGE. 28# 29
30# $FreeBSD: head/sys/boot/i386/cdboot/cdboot.s 130943 2004-06-22 21:55:22Z jhb $	30# $FreeBSD: head/sys/boot/i386/cdboot/cdboot.s 157652 2006-04-11 04:39:29Z sobomax $
31 32# 33# This program is a freestanding boot program to load an a.out binary 34# from a CD-ROM booted with no emulation mode as described by the El 35# Torito standard. Due to broken BIOSen that do not load the desired 36# number of sectors, we try to fit this in as small a space as possible. 37# 38# Basically, we first create a set of boot arguments to pass to the loaded 39# binary. Then we attempt to load /boot/loader from the CD we were booted 40# off of. 41# 42 43# 44# Memory locations. 45# 46 .set MEM_PAGE_SIZE,0x1000 # memory page size, 4k 47 .set MEM_ARG,0x900 # Arguments at start 48 .set MEM_ARG_BTX,0xa100 # Where we move them to so the 49 # BTX client can see them 50 .set MEM_ARG_SIZE,0x18 # Size of the arguments 51 .set MEM_BTX_ADDRESS,0x9000 # where BTX lives 52 .set MEM_BTX_ENTRY,0x9010 # where BTX starts to execute 53 .set MEM_BTX_OFFSET,MEM_PAGE_SIZE # offset of BTX in the loader 54 .set MEM_BTX_CLIENT,0xa000 # where BTX clients live 55# 56# a.out header fields 57# 58 .set AOUT_TEXT,0x04 # text segment size 59 .set AOUT_DATA,0x08 # data segment size 60 .set AOUT_BSS,0x0c # zero'd BSS size 61 .set AOUT_SYMBOLS,0x10 # symbol table 62 .set AOUT_ENTRY,0x14 # entry point 63 .set AOUT_HEADER,MEM_PAGE_SIZE # size of the a.out header 64# 65# Flags for kargs->bootflags 66# 67 .set KARGS_FLAGS_CD,0x1 # flag to indicate booting from 68 # CD loader 69# 70# Segment selectors. 71# 72 .set SEL_SDATA,0x8 # Supervisor data 73 .set SEL_RDATA,0x10 # Real mode data 74 .set SEL_SCODE,0x18 # PM-32 code 75 .set SEL_SCODE16,0x20 # PM-16 code 76# 77# BTX constants 78# 79 .set INT_SYS,0x30 # BTX syscall interrupt 80# 81# Constants for reading from the CD. 82# 83 .set ERROR_TIMEOUT,0x80 # BIOS timeout on read 84 .set NUM_RETRIES,3 # Num times to retry 85 .set SECTOR_SIZE,0x800 # size of a sector 86 .set SECTOR_SHIFT,11 # number of place to shift 87 .set BUFFER_LEN,0x100 # number of sectors in buffer 88 .set MAX_READ,0x10000 # max we can read at a time 89 .set MAX_READ_SEC,MAX_READ >> SECTOR_SHIFT 90 .set MEM_READ_BUFFER,0x9000 # buffer to read from CD 91 .set MEM_VOLDESC,MEM_READ_BUFFER # volume descriptor 92 .set MEM_DIR,MEM_VOLDESC+SECTOR_SIZE # Lookup buffer 93 .set VOLDESC_LBA,0x10 # LBA of vol descriptor 94 .set VD_PRIMARY,1 # Primary VD 95 .set VD_END,255 # VD Terminator 96 .set VD_ROOTDIR,156 # Offset of Root Dir Record 97 .set DIR_LEN,0 # Offset of Dir Record length 98 .set DIR_EA_LEN,1 # Offset of EA length 99 .set DIR_EXTENT,2 # Offset of 64-bit LBA 100 .set DIR_SIZE,10 # Offset of 64-bit length 101 .set DIR_NAMELEN,32 # Offset of 8-bit name len 102 .set DIR_NAME,33 # Offset of dir name 103# 104# We expect to be loaded by the BIOS at 0x7c00 (standard boot loader entry 105# point) 106# 107 .code16 108 .globl start 109 .org 0x0, 0x0 110# 111# Program start. 112# 113start: cld # string ops inc 114 xor %ax,%ax # zero %ax 115 mov %ax,%ss # setup the 116 mov $start,%sp # stack 117 mov %ax,%ds # setup the 118 mov %ax,%es # data segments 119 mov %dl,drive # Save BIOS boot device 120 mov $msg_welcome,%si # %ds:(%si) -> welcome message 121 call putstr # display the welcome message 122# 123# Setup the arguments that the loader is expecting from boot[12] 124# 125 mov $msg_bootinfo,%si # %ds:(%si) -> boot args message 126 call putstr # display the message 127 mov $MEM_ARG,%bx # %ds:(%bx) -> boot args 128 mov %bx,%di # %es:(%di) -> boot args 129 xor %eax,%eax # zero %eax 130 mov $(MEM_ARG_SIZE/4),%cx # Size of arguments in 32-bit 131 # dwords 132 rep # Clear the arguments 133 stosl # to zero 134 mov drive,%dl # Store BIOS boot device 135 mov %dl,0x4(%bx) # in kargs->bootdev 136 or $KARGS_FLAGS_CD,0x8(%bx) # kargs->bootflags \|= 137 # KARGS_FLAGS_CD 138# 139# Load Volume Descriptor 140# 141 mov $VOLDESC_LBA,%eax # Set LBA of first VD 142load_vd: push %eax # Save %eax 143 mov $1,%dh # One sector 144 mov $MEM_VOLDESC,%ebx # Destination 145 call read # Read it in 146 cmpb $VD_PRIMARY,(%bx) # Primary VD? 147 je have_vd # Yes 148 pop %eax # Prepare to 149 inc %eax # try next 150 cmpb $VD_END,(%bx) # Last VD? 151 jne load_vd # No, read next 152 mov $msg_novd,%si # No VD 153 jmp error # Halt 154have_vd: # Have Primary VD 155# 156# Try to look up the loader binary using the paths in the loader_paths 157# array. 158# 159 mov $loader_paths,%si # Point to start of array 160lookup_path: push %si # Save file name pointer 161 call lookup # Try to find file 162 pop %di # Restore file name pointer 163 jnc lookup_found # Found this file 164 xor %al,%al # Look for next 165 mov $0xffff,%cx # path name by 166 repnz # scanning for 167 scasb # nul char 168 mov %di,%si # Point %si at next path 169 mov (%si),%al # Get first char of next path 170 or %al,%al # Is it double nul? 171 jnz lookup_path # No, try it. 172 mov $msg_failed,%si # Failed message 173 jmp error # Halt 174lookup_found: # Found a loader file 175# 176# Load the binary into the buffer. Due to real mode addressing limitations 177# we have to read it in in 64k chunks. 178# 179 mov DIR_SIZE(%bx),%eax # Read file length 180 add $SECTOR_SIZE-1,%eax # Convert length to sectors 181 shr $SECTOR_SHIFT,%eax 182 cmp $BUFFER_LEN,%eax 183 jbe load_sizeok 184 mov $msg_load2big,%si # Error message 185 call error 186load_sizeok: movzbw %al,%cx # Num sectors to read 187 mov DIR_EXTENT(%bx),%eax # Load extent 188 xor %edx,%edx 189 mov DIR_EA_LEN(%bx),%dl 190 add %edx,%eax # Skip extended 191 mov $MEM_READ_BUFFER,%ebx # Read into the buffer 192load_loop: mov %cl,%dh 193 cmp $MAX_READ_SEC,%cl # Truncate to max read size 194 jbe load_notrunc 195 mov $MAX_READ_SEC,%dh 196load_notrunc: sub %dh,%cl # Update count 197 push %eax # Save 198 call read # Read it in 199 pop %eax # Restore 200 add $MAX_READ_SEC,%eax # Update LBA 201 add $MAX_READ,%ebx # Update dest addr 202 jcxz load_done # Done? 203 jmp load_loop # Keep going 204load_done: 205# 206# Turn on the A20 address line 207# 208 call seta20 # Turn A20 on 209# 210# Relocate the loader and BTX using a very lazy protected mode 211# 212 mov $msg_relocate,%si # Display the 213 call putstr # relocation message 214 mov MEM_READ_BUFFER+AOUT_ENTRY,%edi # %edi is the destination 215 mov $(MEM_READ_BUFFER+AOUT_HEADER),%esi # %esi is 216 # the start of the text 217 # segment 218 mov MEM_READ_BUFFER+AOUT_TEXT,%ecx # %ecx = length of the text 219 # segment 220 push %edi # Save entry point for later 221 lgdt gdtdesc # setup our own gdt 222 cli # turn off interrupts 223 mov %cr0,%eax # Turn on 224 or $0x1,%al # protected 225 mov %eax,%cr0 # mode 226 ljmp $SEL_SCODE,$pm_start # long jump to clear the 227 # instruction pre-fetch queue 228 .code32 229pm_start: mov $SEL_SDATA,%ax # Initialize 230 mov %ax,%ds # %ds and 231 mov %ax,%es # %es to a flat selector 232 rep # Relocate the 233 movsb # text segment 234 add $(MEM_PAGE_SIZE - 1),%edi # pad %edi out to a new page 235 and $~(MEM_PAGE_SIZE - 1),%edi # for the data segment 236 mov MEM_READ_BUFFER+AOUT_DATA,%ecx # size of the data segment 237 rep # Relocate the 238 movsb # data segment 239 mov MEM_READ_BUFFER+AOUT_BSS,%ecx # size of the bss 240 xor %eax,%eax # zero %eax 241 add $3,%cl # round %ecx up to 242 shr $2,%ecx # a multiple of 4 243 rep # zero the 244 stosl # bss 245 mov MEM_READ_BUFFER+AOUT_ENTRY,%esi # %esi -> relocated loader 246 add $MEM_BTX_OFFSET,%esi # %esi -> BTX in the loader 247 mov $MEM_BTX_ADDRESS,%edi # %edi -> where BTX needs to go 248 movzwl 0xa(%esi),%ecx # %ecx -> length of BTX 249 rep # Relocate 250 movsb # BTX 251 ljmp $SEL_SCODE16,$pm_16 # Jump to 16-bit PM 252 .code16 253pm_16: mov $SEL_RDATA,%ax # Initialize 254 mov %ax,%ds # %ds and 255 mov %ax,%es # %es to a real mode selector 256 mov %cr0,%eax # Turn off 257 and $~0x1,%al # protected 258 mov %eax,%cr0 # mode 259 ljmp $0,$pm_end # Long jump to clear the 260 # instruction pre-fetch queue 261pm_end: sti # Turn interrupts back on now 262# 263# Copy the BTX client to MEM_BTX_CLIENT 264# 265 xor %ax,%ax # zero %ax and set 266 mov %ax,%ds # %ds and %es 267 mov %ax,%es # to segment 0 268 mov $MEM_BTX_CLIENT,%di # Prepare to relocate 269 mov $btx_client,%si # the simple btx client 270 mov $(btx_client_end-btx_client),%cx # length of btx client 271 rep # Relocate the 272 movsb # simple BTX client 273# 274# Copy the boot[12] args to where the BTX client can see them 275# 276 mov $MEM_ARG,%si # where the args are at now 277 mov $MEM_ARG_BTX,%di # where the args are moving to 278 mov $(MEM_ARG_SIZE/4),%cx # size of the arguments in longs 279 rep # Relocate 280 movsl # the words 281# 282# Save the entry point so the client can get to it later on 283# 284 pop %eax # Restore saved entry point 285 stosl # and add it to the end of 286 # the arguments 287# 288# Now we just start up BTX and let it do the rest 289# 290 mov $msg_jump,%si # Display the 291 call putstr # jump message 292 ljmp $0,$MEM_BTX_ENTRY # Jump to the BTX entry point 293 294# 295# Lookup the file in the path at [SI] from the root directory. 296# 297# Trashes: All but BX 298# Returns: CF = 0 (success), BX = pointer to record 299# CF = 1 (not found) 300# 301lookup: mov $VD_ROOTDIR+MEM_VOLDESC,%bx # Root directory record 302 push %si 303 mov $msg_lookup,%si # Display lookup message 304 call putstr 305 pop %si 306 push %si 307 call putstr 308 mov $msg_lookup2,%si 309 call putstr 310 pop %si 311lookup_dir: lodsb # Get first char of path 312 cmp $0,%al # Are we done? 313 je lookup_done # Yes 314 cmp $'/',%al # Skip path separator. 315 je lookup_dir 316 dec %si # Undo lodsb side effect 317 call find_file # Lookup first path item 318 jnc lookup_dir # Try next component 319 mov $msg_lookupfail,%si # Not found message 320 call putstr 321 stc # Set carry 322 ret 323 jmp error 324lookup_done: mov $msg_lookupok,%si # Success message 325 call putstr 326 clc # Clear carry 327 ret 328 329# 330# Lookup file at [SI] in directory whose record is at [BX]. 331# 332# Trashes: All but returns 333# Returns: CF = 0 (success), BX = pointer to record, SI = next path item 334# CF = 1 (not found), SI = preserved 335# 336find_file: mov DIR_EXTENT(%bx),%eax # Load extent 337 xor %edx,%edx 338 mov DIR_EA_LEN(%bx),%dl 339 add %edx,%eax # Skip extended attributes 340 mov %eax,rec_lba # Save LBA 341 mov DIR_SIZE(%bx),%eax # Save size 342 mov %eax,rec_size 343 xor %cl,%cl # Zero length 344 push %si # Save 345ff.namelen: inc %cl # Update length 346 lodsb # Read char 347 cmp $0,%al # Nul? 348 je ff.namedone # Yes 349 cmp $'/',%al # Path separator? 350 jnz ff.namelen # No, keep going 351ff.namedone: dec %cl # Adjust length and save 352 mov %cl,name_len 353 pop %si # Restore 354ff.load: mov rec_lba,%eax # Load LBA 355 mov $MEM_DIR,%ebx # Address buffer 356 mov $1,%dh # One sector 357 call read # Read directory block 358 incl rec_lba # Update LBA to next block 359ff.scan: mov %ebx,%edx # Check for EOF 360 sub $MEM_DIR,%edx 361 cmp %edx,rec_size 362 ja ff.scan.1 363 stc # EOF reached 364 ret 365ff.scan.1: cmpb $0,DIR_LEN(%bx) # Last record in block? 366 je ff.nextblock 367 push %si # Save 368 movzbw DIR_NAMELEN(%bx),%si # Find end of string 369ff.checkver: cmpb $'0',DIR_NAME-1(%bx,%si) # Less than '0'? 370 jb ff.checkver.1 371 cmpb $'9',DIR_NAME-1(%bx,%si) # Greater than '9'? 372 ja ff.checkver.1 373 dec %si # Next char 374 jnz ff.checkver 375 jmp ff.checklen # All numbers in name, so 376 # no version 377ff.checkver.1: movzbw DIR_NAMELEN(%bx),%cx 378 cmp %cx,%si # Did we find any digits? 379 je ff.checkdot # No 380 cmpb $';',DIR_NAME-1(%bx,%si) # Check for semicolon 381 jne ff.checkver.2 382 dec %si # Skip semicolon 383 mov %si,%cx 384 mov %cl,DIR_NAMELEN(%bx) # Adjust length 385 jmp ff.checkdot 386ff.checkver.2: mov %cx,%si # Restore %si to end of string 387ff.checkdot: cmpb $'.',DIR_NAME-1(%bx,%si) # Trailing dot? 388 jne ff.checklen # No 389 decb DIR_NAMELEN(%bx) # Adjust length 390ff.checklen: pop %si # Restore 391 movzbw name_len,%cx # Load length of name 392 cmp %cl,DIR_NAMELEN(%bx) # Does length match? 393 je ff.checkname # Yes, check name 394ff.nextrec: add DIR_LEN(%bx),%bl # Next record 395 adc $0,%bh 396 jmp ff.scan 397ff.nextblock: subl $SECTOR_SIZE,rec_size # Adjust size 398 jnc ff.load # If subtract ok, keep going 399 ret # End of file, so not found 400ff.checkname: lea DIR_NAME(%bx),%di # Address name in record 401 push %si # Save 402 repe cmpsb # Compare name 403 jcxz ff.match # We have a winner! 404 pop %si # Restore 405 jmp ff.nextrec # Keep looking. 406ff.match: add $2,%sp # Discard saved %si 407 clc # Clear carry 408 ret 409 410# 411# Load DH sectors starting at LBA EAX into [EBX]. 412# 413# Trashes: EAX 414# 415read: push %si # Save 416 push %cx # Save since some BIOSs trash 417 mov %eax,edd_lba # LBA to read from 418 mov %ebx,%eax # Convert address 419 shr $4,%eax # to segment 420 mov %ax,edd_addr+0x2 # and store 421read.retry: call twiddle # Entertain the user 422 push %dx # Save 423 mov $edd_packet,%si # Address Packet 424 mov %dh,edd_len # Set length 425 mov drive,%dl # BIOS Device 426 mov $0x42,%ah # BIOS: Extended Read 427 int $0x13 # Call BIOS 428 pop %dx # Restore 429 jc read.fail # Worked? 430 pop %cx # Restore 431 pop %si 432 ret # Return 433read.fail: cmp $ERROR_TIMEOUT,%ah # Timeout? 434 je read.retry # Yes, Retry. 435read.error: mov %ah,%al # Save error 436 mov $hex_error,%di # Format it 437 call hex8 # as hex 438 mov $msg_badread,%si # Display Read error message 439 440# 441# Display error message at [SI] and halt. 442# 443error: call putstr # Display message 444halt: hlt 445 jmp halt # Spin 446 447# 448# Display a null-terminated string. 449# 450# Trashes: AX, SI 451# 452putstr: push %bx # Save 453putstr.load: lodsb # load %al from %ds:(%si) 454 test %al,%al # stop at null 455 jnz putstr.putc # if the char != null, output it 456 pop %bx # Restore 457 ret # return when null is hit 458putstr.putc: call putc # output char 459 jmp putstr.load # next char 460 461# 462# Display a single char. 463# 464putc: mov $0x7,%bx # attribute for output 465 mov $0xe,%ah # BIOS: put_char 466 int $0x10 # call BIOS, print char in %al 467 ret # Return to caller 468 469# 470# Output the "twiddle" 471# 472twiddle: push %ax # Save 473 push %bx # Save 474 mov twiddle_index,%al # Load index 475 mov twiddle_chars,%bx # Address table 476 inc %al # Next 477 and $3,%al # char 478 mov %al,twiddle_index # Save index for next call 479 xlat # Get char 480 call putc # Output it 481 mov $8,%al # Backspace 482 call putc # Output it 483 pop %bx # Restore 484 pop %ax # Restore 485 ret 486 487#	31 32# 33# This program is a freestanding boot program to load an a.out binary 34# from a CD-ROM booted with no emulation mode as described by the El 35# Torito standard. Due to broken BIOSen that do not load the desired 36# number of sectors, we try to fit this in as small a space as possible. 37# 38# Basically, we first create a set of boot arguments to pass to the loaded 39# binary. Then we attempt to load /boot/loader from the CD we were booted 40# off of. 41# 42 43# 44# Memory locations. 45# 46 .set MEM_PAGE_SIZE,0x1000 # memory page size, 4k 47 .set MEM_ARG,0x900 # Arguments at start 48 .set MEM_ARG_BTX,0xa100 # Where we move them to so the 49 # BTX client can see them 50 .set MEM_ARG_SIZE,0x18 # Size of the arguments 51 .set MEM_BTX_ADDRESS,0x9000 # where BTX lives 52 .set MEM_BTX_ENTRY,0x9010 # where BTX starts to execute 53 .set MEM_BTX_OFFSET,MEM_PAGE_SIZE # offset of BTX in the loader 54 .set MEM_BTX_CLIENT,0xa000 # where BTX clients live 55# 56# a.out header fields 57# 58 .set AOUT_TEXT,0x04 # text segment size 59 .set AOUT_DATA,0x08 # data segment size 60 .set AOUT_BSS,0x0c # zero'd BSS size 61 .set AOUT_SYMBOLS,0x10 # symbol table 62 .set AOUT_ENTRY,0x14 # entry point 63 .set AOUT_HEADER,MEM_PAGE_SIZE # size of the a.out header 64# 65# Flags for kargs->bootflags 66# 67 .set KARGS_FLAGS_CD,0x1 # flag to indicate booting from 68 # CD loader 69# 70# Segment selectors. 71# 72 .set SEL_SDATA,0x8 # Supervisor data 73 .set SEL_RDATA,0x10 # Real mode data 74 .set SEL_SCODE,0x18 # PM-32 code 75 .set SEL_SCODE16,0x20 # PM-16 code 76# 77# BTX constants 78# 79 .set INT_SYS,0x30 # BTX syscall interrupt 80# 81# Constants for reading from the CD. 82# 83 .set ERROR_TIMEOUT,0x80 # BIOS timeout on read 84 .set NUM_RETRIES,3 # Num times to retry 85 .set SECTOR_SIZE,0x800 # size of a sector 86 .set SECTOR_SHIFT,11 # number of place to shift 87 .set BUFFER_LEN,0x100 # number of sectors in buffer 88 .set MAX_READ,0x10000 # max we can read at a time 89 .set MAX_READ_SEC,MAX_READ >> SECTOR_SHIFT 90 .set MEM_READ_BUFFER,0x9000 # buffer to read from CD 91 .set MEM_VOLDESC,MEM_READ_BUFFER # volume descriptor 92 .set MEM_DIR,MEM_VOLDESC+SECTOR_SIZE # Lookup buffer 93 .set VOLDESC_LBA,0x10 # LBA of vol descriptor 94 .set VD_PRIMARY,1 # Primary VD 95 .set VD_END,255 # VD Terminator 96 .set VD_ROOTDIR,156 # Offset of Root Dir Record 97 .set DIR_LEN,0 # Offset of Dir Record length 98 .set DIR_EA_LEN,1 # Offset of EA length 99 .set DIR_EXTENT,2 # Offset of 64-bit LBA 100 .set DIR_SIZE,10 # Offset of 64-bit length 101 .set DIR_NAMELEN,32 # Offset of 8-bit name len 102 .set DIR_NAME,33 # Offset of dir name 103# 104# We expect to be loaded by the BIOS at 0x7c00 (standard boot loader entry 105# point) 106# 107 .code16 108 .globl start 109 .org 0x0, 0x0 110# 111# Program start. 112# 113start: cld # string ops inc 114 xor %ax,%ax # zero %ax 115 mov %ax,%ss # setup the 116 mov $start,%sp # stack 117 mov %ax,%ds # setup the 118 mov %ax,%es # data segments 119 mov %dl,drive # Save BIOS boot device 120 mov $msg_welcome,%si # %ds:(%si) -> welcome message 121 call putstr # display the welcome message 122# 123# Setup the arguments that the loader is expecting from boot[12] 124# 125 mov $msg_bootinfo,%si # %ds:(%si) -> boot args message 126 call putstr # display the message 127 mov $MEM_ARG,%bx # %ds:(%bx) -> boot args 128 mov %bx,%di # %es:(%di) -> boot args 129 xor %eax,%eax # zero %eax 130 mov $(MEM_ARG_SIZE/4),%cx # Size of arguments in 32-bit 131 # dwords 132 rep # Clear the arguments 133 stosl # to zero 134 mov drive,%dl # Store BIOS boot device 135 mov %dl,0x4(%bx) # in kargs->bootdev 136 or $KARGS_FLAGS_CD,0x8(%bx) # kargs->bootflags \|= 137 # KARGS_FLAGS_CD 138# 139# Load Volume Descriptor 140# 141 mov $VOLDESC_LBA,%eax # Set LBA of first VD 142load_vd: push %eax # Save %eax 143 mov $1,%dh # One sector 144 mov $MEM_VOLDESC,%ebx # Destination 145 call read # Read it in 146 cmpb $VD_PRIMARY,(%bx) # Primary VD? 147 je have_vd # Yes 148 pop %eax # Prepare to 149 inc %eax # try next 150 cmpb $VD_END,(%bx) # Last VD? 151 jne load_vd # No, read next 152 mov $msg_novd,%si # No VD 153 jmp error # Halt 154have_vd: # Have Primary VD 155# 156# Try to look up the loader binary using the paths in the loader_paths 157# array. 158# 159 mov $loader_paths,%si # Point to start of array 160lookup_path: push %si # Save file name pointer 161 call lookup # Try to find file 162 pop %di # Restore file name pointer 163 jnc lookup_found # Found this file 164 xor %al,%al # Look for next 165 mov $0xffff,%cx # path name by 166 repnz # scanning for 167 scasb # nul char 168 mov %di,%si # Point %si at next path 169 mov (%si),%al # Get first char of next path 170 or %al,%al # Is it double nul? 171 jnz lookup_path # No, try it. 172 mov $msg_failed,%si # Failed message 173 jmp error # Halt 174lookup_found: # Found a loader file 175# 176# Load the binary into the buffer. Due to real mode addressing limitations 177# we have to read it in in 64k chunks. 178# 179 mov DIR_SIZE(%bx),%eax # Read file length 180 add $SECTOR_SIZE-1,%eax # Convert length to sectors 181 shr $SECTOR_SHIFT,%eax 182 cmp $BUFFER_LEN,%eax 183 jbe load_sizeok 184 mov $msg_load2big,%si # Error message 185 call error 186load_sizeok: movzbw %al,%cx # Num sectors to read 187 mov DIR_EXTENT(%bx),%eax # Load extent 188 xor %edx,%edx 189 mov DIR_EA_LEN(%bx),%dl 190 add %edx,%eax # Skip extended 191 mov $MEM_READ_BUFFER,%ebx # Read into the buffer 192load_loop: mov %cl,%dh 193 cmp $MAX_READ_SEC,%cl # Truncate to max read size 194 jbe load_notrunc 195 mov $MAX_READ_SEC,%dh 196load_notrunc: sub %dh,%cl # Update count 197 push %eax # Save 198 call read # Read it in 199 pop %eax # Restore 200 add $MAX_READ_SEC,%eax # Update LBA 201 add $MAX_READ,%ebx # Update dest addr 202 jcxz load_done # Done? 203 jmp load_loop # Keep going 204load_done: 205# 206# Turn on the A20 address line 207# 208 call seta20 # Turn A20 on 209# 210# Relocate the loader and BTX using a very lazy protected mode 211# 212 mov $msg_relocate,%si # Display the 213 call putstr # relocation message 214 mov MEM_READ_BUFFER+AOUT_ENTRY,%edi # %edi is the destination 215 mov $(MEM_READ_BUFFER+AOUT_HEADER),%esi # %esi is 216 # the start of the text 217 # segment 218 mov MEM_READ_BUFFER+AOUT_TEXT,%ecx # %ecx = length of the text 219 # segment 220 push %edi # Save entry point for later 221 lgdt gdtdesc # setup our own gdt 222 cli # turn off interrupts 223 mov %cr0,%eax # Turn on 224 or $0x1,%al # protected 225 mov %eax,%cr0 # mode 226 ljmp $SEL_SCODE,$pm_start # long jump to clear the 227 # instruction pre-fetch queue 228 .code32 229pm_start: mov $SEL_SDATA,%ax # Initialize 230 mov %ax,%ds # %ds and 231 mov %ax,%es # %es to a flat selector 232 rep # Relocate the 233 movsb # text segment 234 add $(MEM_PAGE_SIZE - 1),%edi # pad %edi out to a new page 235 and $~(MEM_PAGE_SIZE - 1),%edi # for the data segment 236 mov MEM_READ_BUFFER+AOUT_DATA,%ecx # size of the data segment 237 rep # Relocate the 238 movsb # data segment 239 mov MEM_READ_BUFFER+AOUT_BSS,%ecx # size of the bss 240 xor %eax,%eax # zero %eax 241 add $3,%cl # round %ecx up to 242 shr $2,%ecx # a multiple of 4 243 rep # zero the 244 stosl # bss 245 mov MEM_READ_BUFFER+AOUT_ENTRY,%esi # %esi -> relocated loader 246 add $MEM_BTX_OFFSET,%esi # %esi -> BTX in the loader 247 mov $MEM_BTX_ADDRESS,%edi # %edi -> where BTX needs to go 248 movzwl 0xa(%esi),%ecx # %ecx -> length of BTX 249 rep # Relocate 250 movsb # BTX 251 ljmp $SEL_SCODE16,$pm_16 # Jump to 16-bit PM 252 .code16 253pm_16: mov $SEL_RDATA,%ax # Initialize 254 mov %ax,%ds # %ds and 255 mov %ax,%es # %es to a real mode selector 256 mov %cr0,%eax # Turn off 257 and $~0x1,%al # protected 258 mov %eax,%cr0 # mode 259 ljmp $0,$pm_end # Long jump to clear the 260 # instruction pre-fetch queue 261pm_end: sti # Turn interrupts back on now 262# 263# Copy the BTX client to MEM_BTX_CLIENT 264# 265 xor %ax,%ax # zero %ax and set 266 mov %ax,%ds # %ds and %es 267 mov %ax,%es # to segment 0 268 mov $MEM_BTX_CLIENT,%di # Prepare to relocate 269 mov $btx_client,%si # the simple btx client 270 mov $(btx_client_end-btx_client),%cx # length of btx client 271 rep # Relocate the 272 movsb # simple BTX client 273# 274# Copy the boot[12] args to where the BTX client can see them 275# 276 mov $MEM_ARG,%si # where the args are at now 277 mov $MEM_ARG_BTX,%di # where the args are moving to 278 mov $(MEM_ARG_SIZE/4),%cx # size of the arguments in longs 279 rep # Relocate 280 movsl # the words 281# 282# Save the entry point so the client can get to it later on 283# 284 pop %eax # Restore saved entry point 285 stosl # and add it to the end of 286 # the arguments 287# 288# Now we just start up BTX and let it do the rest 289# 290 mov $msg_jump,%si # Display the 291 call putstr # jump message 292 ljmp $0,$MEM_BTX_ENTRY # Jump to the BTX entry point 293 294# 295# Lookup the file in the path at [SI] from the root directory. 296# 297# Trashes: All but BX 298# Returns: CF = 0 (success), BX = pointer to record 299# CF = 1 (not found) 300# 301lookup: mov $VD_ROOTDIR+MEM_VOLDESC,%bx # Root directory record 302 push %si 303 mov $msg_lookup,%si # Display lookup message 304 call putstr 305 pop %si 306 push %si 307 call putstr 308 mov $msg_lookup2,%si 309 call putstr 310 pop %si 311lookup_dir: lodsb # Get first char of path 312 cmp $0,%al # Are we done? 313 je lookup_done # Yes 314 cmp $'/',%al # Skip path separator. 315 je lookup_dir 316 dec %si # Undo lodsb side effect 317 call find_file # Lookup first path item 318 jnc lookup_dir # Try next component 319 mov $msg_lookupfail,%si # Not found message 320 call putstr 321 stc # Set carry 322 ret 323 jmp error 324lookup_done: mov $msg_lookupok,%si # Success message 325 call putstr 326 clc # Clear carry 327 ret 328 329# 330# Lookup file at [SI] in directory whose record is at [BX]. 331# 332# Trashes: All but returns 333# Returns: CF = 0 (success), BX = pointer to record, SI = next path item 334# CF = 1 (not found), SI = preserved 335# 336find_file: mov DIR_EXTENT(%bx),%eax # Load extent 337 xor %edx,%edx 338 mov DIR_EA_LEN(%bx),%dl 339 add %edx,%eax # Skip extended attributes 340 mov %eax,rec_lba # Save LBA 341 mov DIR_SIZE(%bx),%eax # Save size 342 mov %eax,rec_size 343 xor %cl,%cl # Zero length 344 push %si # Save 345ff.namelen: inc %cl # Update length 346 lodsb # Read char 347 cmp $0,%al # Nul? 348 je ff.namedone # Yes 349 cmp $'/',%al # Path separator? 350 jnz ff.namelen # No, keep going 351ff.namedone: dec %cl # Adjust length and save 352 mov %cl,name_len 353 pop %si # Restore 354ff.load: mov rec_lba,%eax # Load LBA 355 mov $MEM_DIR,%ebx # Address buffer 356 mov $1,%dh # One sector 357 call read # Read directory block 358 incl rec_lba # Update LBA to next block 359ff.scan: mov %ebx,%edx # Check for EOF 360 sub $MEM_DIR,%edx 361 cmp %edx,rec_size 362 ja ff.scan.1 363 stc # EOF reached 364 ret 365ff.scan.1: cmpb $0,DIR_LEN(%bx) # Last record in block? 366 je ff.nextblock 367 push %si # Save 368 movzbw DIR_NAMELEN(%bx),%si # Find end of string 369ff.checkver: cmpb $'0',DIR_NAME-1(%bx,%si) # Less than '0'? 370 jb ff.checkver.1 371 cmpb $'9',DIR_NAME-1(%bx,%si) # Greater than '9'? 372 ja ff.checkver.1 373 dec %si # Next char 374 jnz ff.checkver 375 jmp ff.checklen # All numbers in name, so 376 # no version 377ff.checkver.1: movzbw DIR_NAMELEN(%bx),%cx 378 cmp %cx,%si # Did we find any digits? 379 je ff.checkdot # No 380 cmpb $';',DIR_NAME-1(%bx,%si) # Check for semicolon 381 jne ff.checkver.2 382 dec %si # Skip semicolon 383 mov %si,%cx 384 mov %cl,DIR_NAMELEN(%bx) # Adjust length 385 jmp ff.checkdot 386ff.checkver.2: mov %cx,%si # Restore %si to end of string 387ff.checkdot: cmpb $'.',DIR_NAME-1(%bx,%si) # Trailing dot? 388 jne ff.checklen # No 389 decb DIR_NAMELEN(%bx) # Adjust length 390ff.checklen: pop %si # Restore 391 movzbw name_len,%cx # Load length of name 392 cmp %cl,DIR_NAMELEN(%bx) # Does length match? 393 je ff.checkname # Yes, check name 394ff.nextrec: add DIR_LEN(%bx),%bl # Next record 395 adc $0,%bh 396 jmp ff.scan 397ff.nextblock: subl $SECTOR_SIZE,rec_size # Adjust size 398 jnc ff.load # If subtract ok, keep going 399 ret # End of file, so not found 400ff.checkname: lea DIR_NAME(%bx),%di # Address name in record 401 push %si # Save 402 repe cmpsb # Compare name 403 jcxz ff.match # We have a winner! 404 pop %si # Restore 405 jmp ff.nextrec # Keep looking. 406ff.match: add $2,%sp # Discard saved %si 407 clc # Clear carry 408 ret 409 410# 411# Load DH sectors starting at LBA EAX into [EBX]. 412# 413# Trashes: EAX 414# 415read: push %si # Save 416 push %cx # Save since some BIOSs trash 417 mov %eax,edd_lba # LBA to read from 418 mov %ebx,%eax # Convert address 419 shr $4,%eax # to segment 420 mov %ax,edd_addr+0x2 # and store 421read.retry: call twiddle # Entertain the user 422 push %dx # Save 423 mov $edd_packet,%si # Address Packet 424 mov %dh,edd_len # Set length 425 mov drive,%dl # BIOS Device 426 mov $0x42,%ah # BIOS: Extended Read 427 int $0x13 # Call BIOS 428 pop %dx # Restore 429 jc read.fail # Worked? 430 pop %cx # Restore 431 pop %si 432 ret # Return 433read.fail: cmp $ERROR_TIMEOUT,%ah # Timeout? 434 je read.retry # Yes, Retry. 435read.error: mov %ah,%al # Save error 436 mov $hex_error,%di # Format it 437 call hex8 # as hex 438 mov $msg_badread,%si # Display Read error message 439 440# 441# Display error message at [SI] and halt. 442# 443error: call putstr # Display message 444halt: hlt 445 jmp halt # Spin 446 447# 448# Display a null-terminated string. 449# 450# Trashes: AX, SI 451# 452putstr: push %bx # Save 453putstr.load: lodsb # load %al from %ds:(%si) 454 test %al,%al # stop at null 455 jnz putstr.putc # if the char != null, output it 456 pop %bx # Restore 457 ret # return when null is hit 458putstr.putc: call putc # output char 459 jmp putstr.load # next char 460 461# 462# Display a single char. 463# 464putc: mov $0x7,%bx # attribute for output 465 mov $0xe,%ah # BIOS: put_char 466 int $0x10 # call BIOS, print char in %al 467 ret # Return to caller 468 469# 470# Output the "twiddle" 471# 472twiddle: push %ax # Save 473 push %bx # Save 474 mov twiddle_index,%al # Load index 475 mov twiddle_chars,%bx # Address table 476 inc %al # Next 477 and $3,%al # char 478 mov %al,twiddle_index # Save index for next call 479 xlat # Get char 480 call putc # Output it 481 mov $8,%al # Backspace 482 call putc # Output it 483 pop %bx # Restore 484 pop %ax # Restore 485 ret 486 487#
488# Enable A20	488# Enable A20. Put upper limit on amount of time we wait for the 489# keyboard controller to get ready (65K x ISA access time). If 490# we wait more than that amount it's likely that the hardware 491# is legacy-free and simply doesn't have keyboard controller 492# and don't need enabling A20 at all.
489# 490seta20: cli # Disable interrupts	493# 494seta20: cli # Disable interrupts
491seta20.1: in $0x64,%al # Get status	495 xor %cx,%cx # Clear 496seta20.1: inc %cx # Increment, overflow? 497 jz seta20.3 # Yes 498 in $0x64,%al # Get status
492 test $0x2,%al # Busy? 493 jnz seta20.1 # Yes 494 mov $0xd1,%al # Command: Write 495 out %al,$0x64 # output port 496seta20.2: in $0x64,%al # Get status 497 test $0x2,%al # Busy? 498 jnz seta20.2 # Yes 499 mov $0xdf,%al # Enable 500 out %al,$0x60 # A20	499 test $0x2,%al # Busy? 500 jnz seta20.1 # Yes 501 mov $0xd1,%al # Command: Write 502 out %al,$0x64 # output port 503seta20.2: in $0x64,%al # Get status 504 test $0x2,%al # Busy? 505 jnz seta20.2 # Yes 506 mov $0xdf,%al # Enable 507 out %al,$0x60 # A20
501 sti # Enable interrupts	508seta20.3: sti # Enable interrupts
502 ret # To caller 503 504# 505# Convert AL to hex, saving the result to [EDI]. 506# 507hex8: pushl %eax # Save 508 shrb $0x4,%al # Do upper 509 call hex8.1 # 4 510 popl %eax # Restore 511hex8.1: andb $0xf,%al # Get lower 4 512 cmpb $0xa,%al # Convert 513 sbbb $0x69,%al # to hex 514 das # digit 515 orb $0x20,%al # To lower case 516 stosb # Save char 517 ret # (Recursive) 518 519# 520# BTX client to start btxldr 521# 522 .code32 523btx_client: mov $(MEM_ARG_BTX-MEM_BTX_CLIENT+MEM_ARG_SIZE-4), %esi 524 # %ds:(%esi) -> end 525 # of boot[12] args 526 mov $(MEM_ARG_SIZE/4),%ecx # Number of words to push 527 std # Go backwards 528push_arg: lodsl # Read argument 529 push %eax # Push it onto the stack 530 loop push_arg # Push all of the arguments 531 cld # In case anyone depends on this 532 pushl MEM_ARG_BTX-MEM_BTX_CLIENT+MEM_ARG_SIZE # Entry point of 533 # the loader 534 push %eax # Emulate a near call 535 mov $0x1,%eax # 'exec' system call 536 int $INT_SYS # BTX system call 537btx_client_end: 538 .code16 539 540 .p2align 4 541# 542# Global descriptor table. 543# 544gdt: .word 0x0,0x0,0x0,0x0 # Null entry 545 .word 0xffff,0x0,0x9200,0xcf # SEL_SDATA 546 .word 0xffff,0x0,0x9200,0x0 # SEL_RDATA 547 .word 0xffff,0x0,0x9a00,0xcf # SEL_SCODE (32-bit) 548 .word 0xffff,0x0,0x9a00,0x8f # SEL_SCODE16 (16-bit) 549gdt.1: 550# 551# Pseudo-descriptors. 552# 553gdtdesc: .word gdt.1-gdt-1 # Limit 554 .long gdt # Base 555# 556# EDD Packet 557# 558edd_packet: .byte 0x10 # Length 559 .byte 0 # Reserved 560edd_len: .byte 0x0 # Num to read 561 .byte 0 # Reserved 562edd_addr: .word 0x0,0x0 # Seg:Off 563edd_lba: .quad 0x0 # LBA 564 565drive: .byte 0 566 567# 568# State for searching dir 569# 570rec_lba: .long 0x0 # LBA (adjusted for EA) 571rec_size: .long 0x0 # File size 572name_len: .byte 0x0 # Length of current name 573 574twiddle_index: .byte 0x0 575 576msg_welcome: .asciz "CD Loader 1.2\r\n\n" 577msg_bootinfo: .asciz "Building the boot loader arguments\r\n" 578msg_relocate: .asciz "Relocating the loader and the BTX\r\n" 579msg_jump: .asciz "Starting the BTX loader\r\n" 580msg_badread: .ascii "Read Error: 0x" 581hex_error: .ascii "00\r\n" 582msg_novd: .asciz "Could not find Primary Volume Descriptor\r\n" 583msg_lookup: .asciz "Looking up " 584msg_lookup2: .asciz "... " 585msg_lookupok: .asciz "Found\r\n" 586msg_lookupfail: .asciz "File not found\r\n" 587msg_load2big: .asciz "File too big\r\n" 588msg_failed: .asciz "Boot failed\r\n" 589twiddle_chars: .ascii "\|/-\\" 590loader_paths: .asciz "/BOOT/LOADER" 591 .asciz "/boot/loader" 592 .byte 0 593	509 ret # To caller 510 511# 512# Convert AL to hex, saving the result to [EDI]. 513# 514hex8: pushl %eax # Save 515 shrb $0x4,%al # Do upper 516 call hex8.1 # 4 517 popl %eax # Restore 518hex8.1: andb $0xf,%al # Get lower 4 519 cmpb $0xa,%al # Convert 520 sbbb $0x69,%al # to hex 521 das # digit 522 orb $0x20,%al # To lower case 523 stosb # Save char 524 ret # (Recursive) 525 526# 527# BTX client to start btxldr 528# 529 .code32 530btx_client: mov $(MEM_ARG_BTX-MEM_BTX_CLIENT+MEM_ARG_SIZE-4), %esi 531 # %ds:(%esi) -> end 532 # of boot[12] args 533 mov $(MEM_ARG_SIZE/4),%ecx # Number of words to push 534 std # Go backwards 535push_arg: lodsl # Read argument 536 push %eax # Push it onto the stack 537 loop push_arg # Push all of the arguments 538 cld # In case anyone depends on this 539 pushl MEM_ARG_BTX-MEM_BTX_CLIENT+MEM_ARG_SIZE # Entry point of 540 # the loader 541 push %eax # Emulate a near call 542 mov $0x1,%eax # 'exec' system call 543 int $INT_SYS # BTX system call 544btx_client_end: 545 .code16 546 547 .p2align 4 548# 549# Global descriptor table. 550# 551gdt: .word 0x0,0x0,0x0,0x0 # Null entry 552 .word 0xffff,0x0,0x9200,0xcf # SEL_SDATA 553 .word 0xffff,0x0,0x9200,0x0 # SEL_RDATA 554 .word 0xffff,0x0,0x9a00,0xcf # SEL_SCODE (32-bit) 555 .word 0xffff,0x0,0x9a00,0x8f # SEL_SCODE16 (16-bit) 556gdt.1: 557# 558# Pseudo-descriptors. 559# 560gdtdesc: .word gdt.1-gdt-1 # Limit 561 .long gdt # Base 562# 563# EDD Packet 564# 565edd_packet: .byte 0x10 # Length 566 .byte 0 # Reserved 567edd_len: .byte 0x0 # Num to read 568 .byte 0 # Reserved 569edd_addr: .word 0x0,0x0 # Seg:Off 570edd_lba: .quad 0x0 # LBA 571 572drive: .byte 0 573 574# 575# State for searching dir 576# 577rec_lba: .long 0x0 # LBA (adjusted for EA) 578rec_size: .long 0x0 # File size 579name_len: .byte 0x0 # Length of current name 580 581twiddle_index: .byte 0x0 582 583msg_welcome: .asciz "CD Loader 1.2\r\n\n" 584msg_bootinfo: .asciz "Building the boot loader arguments\r\n" 585msg_relocate: .asciz "Relocating the loader and the BTX\r\n" 586msg_jump: .asciz "Starting the BTX loader\r\n" 587msg_badread: .ascii "Read Error: 0x" 588hex_error: .ascii "00\r\n" 589msg_novd: .asciz "Could not find Primary Volume Descriptor\r\n" 590msg_lookup: .asciz "Looking up " 591msg_lookup2: .asciz "... " 592msg_lookupok: .asciz "Found\r\n" 593msg_lookupfail: .asciz "File not found\r\n" 594msg_load2big: .asciz "File too big\r\n" 595msg_failed: .asciz "Boot failed\r\n" 596twiddle_chars: .ascii "\|/-\\" 597loader_paths: .asciz "/BOOT/LOADER" 598 .asciz "/boot/loader" 599 .byte 0 600