sys/boot/pc98/btx/btx/btx.s

   1 #
   2 # Copyright (c) 1998 Robert Nordier
   3 # All rights reserved.
   4 #
   5 # Redistribution and use in source and binary forms are freely
   6 # permitted provided that the above copyright notice and this
   7 # paragraph and the following disclaimer are duplicated in all
   8 # such forms.
   9 #
  10 # This software is provided "AS IS" and without any express or
  11 # implied warranties, including, without limitation, the implied
  12 # warranties of merchantability and fitness for a particular
  13 # purpose.
  14 #
  15
  16 # $FreeBSD: src/sys/boot/pc98/btx/btx/btx.s,v 1.6.2.5 2001/12/27 16:53:08 nyan Exp $
  17
  18 #
  19 # Memory layout.
  20 #
  21                 .set MEM_BTX,0x1000             # Start of BTX memory
  22                 .set MEM_ESP0,0x1800            # Supervisor stack
  23                 .set MEM_BUF,0x1800             # Scratch buffer
  24                 .set MEM_ESP1,0x1e00            # Link stack
  25                 .set MEM_IDT,0x1e00             # IDT
  26                 .set MEM_TSS,0x1f98             # TSS
  27                 .set MEM_MAP,0x2000             # I/O bit map
  28                 .set MEM_DIR,0x4000             # Page directory
  29                 .set MEM_TBL,0x5000             # Page tables
  30                 .set MEM_ORG,0x9000             # BTX code
  31                 .set MEM_USR,0xa000             # Start of user memory
  32 #
  33 # Paging control.
  34 #
  35                 .set PAG_SIZ,0x1000             # Page size
  36                 .set PAG_CNT,0x1000             # Pages to map
  37 #
  38 # Segment selectors.
  39 #
  40                 .set SEL_SCODE,0x8              # Supervisor code
  41                 .set SEL_SDATA,0x10             # Supervisor data
  42                 .set SEL_RCODE,0x18             # Real mode code
  43                 .set SEL_RDATA,0x20             # Real mode data
  44                 .set SEL_UCODE,0x28|3           # User code
  45                 .set SEL_UDATA,0x30|3           # User data
  46                 .set SEL_TSS,0x38               # TSS
  47 #
  48 # Task state segment fields.
  49 #
  50                 .set TSS_ESP0,0x4               # PL 0 ESP
  51                 .set TSS_SS0,0x8                # PL 0 SS
  52                 .set TSS_ESP1,0xc               # PL 1 ESP
  53                 .set TSS_MAP,0x66               # I/O bit map base
  54 #
  55 # System calls.
  56 #
  57                 .set SYS_EXIT,0x0               # Exit
  58                 .set SYS_EXEC,0x1               # Exec
  59 #
  60 # V86 constants.
  61 #
  62                 .set V86_FLG,0x208eff           # V86 flag mask
  63                 .set V86_STK,0x400              # V86 stack allowance
  64 #
  65 # Dump format control bytes.
  66 #
  67                 .set DMP_X16,0x1                # Word
  68                 .set DMP_X32,0x2                # Long
  69                 .set DMP_MEM,0x4                # Memory
  70                 .set DMP_EOL,0x8                # End of line
  71 #
  72 # Screen defaults and assumptions.
  73 #
  74 .`ifdef' PC98
  75                 .set SCR_MAT,0xe1               # Mode/attribute
  76 .else
  77                 .set SCR_MAT,0x7                # Mode/attribute
  78 .endif
  79                 .set SCR_COL,0x50               # Columns per row
  80                 .set SCR_ROW,0x19               # Rows per screen
  81 #
  82 # BIOS Data Area locations.
  83 #
  84 .`ifdef' PC98
  85                 .set BDA_MEM,0x501              # Free memory
  86                 .set BDA_KEYFLAGS,0x53a         # Keyboard shift-state flags
  87                 .set BDA_POS,0x53e              # Cursor position
  88 .else
  89                 .set BDA_MEM,0x413              # Free memory
  90                 .set BDA_KEYFLAGS,0x417         # Keyboard shift-state flags
  91                 .set BDA_SCR,0x449              # Video mode
  92                 .set BDA_POS,0x450              # Cursor position
  93                 .set BDA_BOOT,0x472             # Boot howto flag
  94 .endif
  95 #
  96 # Derivations, for brevity.
  97 #
  98                 .set _ESP0H,MEM_ESP0>>0x8       # Byte 1 of ESP0
  99                 .set _ESP1H,MEM_ESP1>>0x8       # Byte 1 of ESP1
 100                 .set _TSSIO,MEM_MAP-MEM_TSS     # TSS I/O base
 101                 .set _TSSLM,MEM_DIR-MEM_TSS-1   # TSS limit
 102                 .set _IDTLM,MEM_TSS-MEM_IDT-1   # IDT limit
 103 #
 104 # Code segment.
 105 #
 106                 .globl start
 107                 .code16
 108 start:                                          # Start of code
 109 #
 110 # BTX header.
 111 #
 112 btx_hdr:        .byte 0xeb                      # Machine ID
 113                 .byte 0xe                       # Header size
 114                 .ascii "BTX"                    # Magic
 115                 .byte 0x1                       # Major version
 116                 .byte 0x1                       # Minor version
 117                 .byte BTX_FLAGS                 # Flags
 118                 .word PAG_CNT-MEM_ORG>>0xc      # Paging control
 119                 .word break-start               # Text size
 120                 .long 0x0                       # Entry address
 121 #
 122 # Initialization routine.
 123 #
 124 init:           cli                             # Disable interrupts
 125                 xor %ax,%ax                     # Zero/segment
 126                 mov %ax,%ss                     # Set up
 127                 mov $MEM_ESP0,%sp               #  stack
 128                 mov %ax,%es                     # Address
 129                 mov %ax,%ds                     #  data
 130                 pushl $0x2                      # Clear
 131                 popfl                           #  flags
 132 #
 133 # Initialize memory.
 134 #
 135                 mov $MEM_IDT,%di                # Memory to initialize
 136                 mov $(MEM_ORG-MEM_IDT)/2,%cx    # Words to zero
 137                 push %di                        # Save
 138                 rep                             # Zero-fill
 139                 stosw                           #  memory
 140                 pop %di                         # Restore
 141 #
 142 # Create IDT.
 143 #
 144                 mov $idtctl,%si                 # Control string
 145 init.1:         lodsb                           # Get entry
 146                 cbw                             #  count
 147                 xchg %ax,%cx                    #  as word
 148                 jcxz init.4                     # If done
 149                 lodsb                           # Get segment
 150                 xchg %ax,%dx                    #  P:DPL:type
 151                 lodsw                           # Get control
 152                 xchg %ax,%bx                    #  set
 153                 lodsw                           # Get handler offset
 154                 mov $SEL_SCODE,%dh              # Segment selector
 155 init.2:         shr %bx                         # Handle this int?
 156                 jnc init.3                      # No
 157                 mov %ax,(%di)                   # Set handler offset
 158                 mov %dh,0x2(%di)                #  and selector
 159                 mov %dl,0x5(%di)                # Set P:DPL:type
 160                 add $0x4,%ax                    # Next handler
 161 init.3:         lea 0x8(%di),%di                # Next entry
 162                 loop init.2                     # Till set done
 163                 jmp init.1                      # Continue
 164 #
 165 # Initialize TSS.
 166 #
 167 init.4:         movb $_ESP0H,TSS_ESP0+1(%di)    # Set ESP0
 168                 movb $SEL_SDATA,TSS_SS0(%di)    # Set SS0
 169                 movb $_ESP1H,TSS_ESP1+1(%di)    # Set ESP1
 170                 movb $_TSSIO,TSS_MAP(%di)       # Set I/O bit map base
 171 ifdef(`PAGING',`
 172 #
 173 # Create page directory.
 174 #
 175                 xor %edx,%edx                   # Page
 176                 mov $PAG_SIZ>>0x8,%dh           #  size
 177                 xor %eax,%eax                   # Zero
 178                 mov $MEM_DIR,%di                # Page directory
 179                 mov $PAG_CNT>>0xa,%cl           # Entries
 180                 mov $MEM_TBL|0x7,%ax            # First entry
 181 init.5:         stosl                           # Write entry
 182                 add %dx,%ax                     # To next
 183                 loop init.5                     # Till done
 184 #
 185 # Create page tables.
 186 #
 187                 mov $MEM_TBL,%di                # Page table
 188                 mov $PAG_CNT>>0x8,%ch           # Entries
 189                 xor %ax,%ax                     # Start address
 190 init.6:         mov $0x7,%al                    # Set U:W:P flags
 191                 cmp btx_hdr+0x8,%cx             # Standard user page?
 192                 jb init.7                       # Yes
 193                 cmp $PAG_CNT-MEM_BTX>>0xc,%cx   # BTX memory?
 194                 jae init.7                      # No or first page
 195                 and $~0x2,%al                   # Clear W flag
 196                 cmp $PAG_CNT-MEM_USR>>0xc,%cx   # User page zero?
 197                 jne init.7                      # No
 198                 testb $0x80,btx_hdr+0x7         # Unmap it?
 199                 jz init.7                       # No
 200                 and $~0x1,%al                   # Clear P flag
 201 init.7:         stosl                           # Set entry
 202                 add %edx,%eax                   # Next address
 203                 loop init.6                     # Till done
 204 ')
 205 #
 206 # Bring up the system.
 207 #
 208                 mov $0x2820,%bx                 # Set protected mode
 209                 callw setpic                    #  IRQ offsets
 210                 lidt idtdesc                    # Set IDT
 211 ifdef(`PAGING',`
 212                 xor %eax,%eax                   # Set base
 213                 mov $MEM_DIR>>0x8,%ah           #  of page
 214                 mov %eax,%cr3                   #  directory
 215 ')
 216                 lgdt gdtdesc                    # Set GDT
 217                 mov %cr0,%eax                   # Switch to protected
 218 ifdef(`PAGING',`
 219                 or $0x80000001,%eax             #  mode and enable paging
 220 ',`
 221                 or $0x01,%eax                   #  mode
 222 ')
 223                 mov %eax,%cr0                   #
 224                 ljmp $SEL_SCODE,$init.8         # To 32-bit code
 225                 .code32
 226 init.8:         xorl %ecx,%ecx                  # Zero
 227                 movb $SEL_SDATA,%cl             # To 32-bit
 228                 movw %cx,%ss                    #  stack
 229 #
 230 # Launch user task.
 231 #
 232                 movb $SEL_TSS,%cl               # Set task
 233                 ltr %cx                         #  register
 234                 movl $MEM_USR,%edx              # User base address
 235                 movzwl %ss:BDA_MEM,%eax         # Get free memory
 236 .`ifdef' PC98
 237                 andl $0x7,%eax
 238                 incl %eax
 239                 shll $0x11,%eax                 # To bytes
 240 .else
 241                 shll $0xa,%eax                  # To bytes
 242 .endif
 243                 subl $0x1000,%eax               # Less arg space
 244                 subl %edx,%eax                  # Less base
 245                 movb $SEL_UDATA,%cl             # User data selector
 246                 pushl %ecx                      # Set SS
 247                 pushl %eax                      # Set ESP
 248                 push $0x202                     # Set flags (IF set)
 249                 push $SEL_UCODE                 # Set CS
 250                 pushl btx_hdr+0xc               # Set EIP
 251                 pushl %ecx                      # Set GS
 252                 pushl %ecx                      # Set FS
 253                 pushl %ecx                      # Set DS
 254                 pushl %ecx                      # Set ES
 255                 pushl %edx                      # Set EAX
 256                 movb $0x7,%cl                   # Set remaining
 257 init.9:         push $0x0                       #  general
 258                 loop init.9                     #  registers
 259                 popa                            #  and initialize
 260                 popl %es                        # Initialize
 261                 popl %ds                        #  user
 262                 popl %fs                        #  segment
 263                 popl %gs                        #  registers
 264                 iret                            # To user mode
 265 #
 266 # Exit routine.
 267 #
 268 exit:           cli                             # Disable interrupts
 269                 movl $MEM_ESP0,%esp             # Clear stack
 270 #
 271 # Turn off paging.
 272 #
 273                 movl %cr0,%eax                  # Get CR0
 274 ifdef(`PAGING',`
 275                 andl $~0x80000000,%eax          # Disable
 276                 movl %eax,%cr0                  #  paging
 277 ')
 278                 xorl %ecx,%ecx                  # Zero
 279 ifdef(`PAGING',`
 280                 movl %ecx,%cr3                  # Flush TLB
 281 ')
 282 #
 283 # To 16 bits.
 284 #
 285                 ljmpw $SEL_RCODE,$exit.1        # Reload CS
 286                 .code16
 287 exit.1:         mov $SEL_RDATA,%cl              # 16-bit selector
 288                 mov %cx,%ss                     # Reload SS
 289                 mov %cx,%ds                     # Load
 290                 mov %cx,%es                     #  remaining
 291                 mov %cx,%fs                     #  segment
 292                 mov %cx,%gs                     #  registers
 293 #
 294 # To real-address mode.
 295 #
 296                 dec %ax                         # Switch to
 297                 mov %eax,%cr0                   #  real mode
 298                 ljmp $0x0,$exit.2               # Reload CS
 299 exit.2:         xor %ax,%ax                     # Real mode segment
 300                 mov %ax,%ss                     # Reload SS
 301                 mov %ax,%ds                     # Address data
 302 .`ifdef' PC98
 303                 mov $0x1008,%bx                 # Set real mode
 304 .else
 305                 mov $0x7008,%bx                 # Set real mode
 306 .endif
 307                 callw setpic                    #  IRQ offsets
 308                 lidt ivtdesc                    # Set IVT
 309 #
 310 # Reboot or await reset.
 311 #
 312                 sti                             # Enable interrupts
 313                 testb $0x1,btx_hdr+0x7          # Reboot?
 314 exit.3:         jz exit.3                       # No
 315 .`ifdef' PC98
 316                 movb $0xa0,%al
 317                 outb %al,$0x35
 318                 movb 0,%al
 319                 outb %al,$0xf0
 320 exit.4:         jmp exit.4
 321 .else
 322                 movw $0x1234, BDA_BOOT          # Do a warm boot
 323                 ljmp $0xffff,$0x0               # reboot the machine
 324 .endif
 325 #
 326 # Set IRQ offsets by reprogramming 8259A PICs.
 327 #
 328 .`ifdef' PC98
 329 setpic:         in $0x02,%al                    # Save master
 330                 push %ax                        #  IMR
 331                 in $0x0a,%al                    # Save slave
 332                 push %ax                        #  IMR
 333                 movb $0x11,%al                  # ICW1 to
 334                 outb %al,$0x00                  #  master,
 335                 outb %al,$0x08                  #  slave
 336                 movb %bl,%al                    # ICW2 to
 337                 outb %al,$0x02                  #  master
 338                 movb %bh,%al                    # ICW2 to
 339                 outb %al,$0x0a                  #  slave
 340                 movb $0x80,%al                  # ICW3 to
 341                 outb %al,$0x02                  #  master
 342                 movb $0x7,%al                   # ICW3 to
 343                 outb %al,$0x0a                  #  slave
 344                 movb $0x1d,%al                  # ICW4 to
 345                 outb %al,$0x02                  #  master,
 346                 movb $0x9,%al                   # ICW4 to
 347                 outb %al,$0x0a                  #  slave
 348                 pop %ax                         # Restore slave
 349                 outb %al,$0x0a                  #  IMR
 350                 pop %ax                         # Restore master
 351                 outb %al,$0x02                  #  IMR
 352 .else
 353 setpic:         in $0x21,%al                    # Save master
 354                 push %ax                        #  IMR
 355                 in $0xa1,%al                    # Save slave
 356                 push %ax                        #  IMR
 357                 movb $0x11,%al                  # ICW1 to
 358                 outb %al,$0x20                  #  master,
 359                 outb %al,$0xa0                  #  slave
 360                 movb %bl,%al                    # ICW2 to
 361                 outb %al,$0x21                  #  master
 362                 movb %bh,%al                    # ICW2 to
 363                 outb %al,$0xa1                  #  slave
 364                 movb $0x4,%al                   # ICW3 to
 365                 outb %al,$0x21                  #  master
 366                 movb $0x2,%al                   # ICW3 to
 367                 outb %al,$0xa1                  #  slave
 368                 movb $0x1,%al                   # ICW4 to
 369                 outb %al,$0x21                  #  master,
 370                 outb %al,$0xa1                  #  slave
 371                 pop %ax                         # Restore slave
 372                 outb %al,$0xa1                  #  IMR
 373                 pop %ax                         # Restore master
 374                 outb %al,$0x21                  #  IMR
 375 .endif
 376                 retw                            # To caller
 377                 .code32
 378 #
 379 # Initiate return from V86 mode to user mode.
 380 #
 381 inthlt:         hlt                             # To supervisor mode
 382 #
 383 # Exception jump table.
 384 #
 385 intx00:         push $0x0                       # Int 0x0: #DE
 386                 jmp ex_noc                      # Divide error
 387                 push $0x1                       # Int 0x1: #DB
 388                 jmp ex_noc                      # Debug
 389                 push $0x3                       # Int 0x3: #BP
 390                 jmp ex_noc                      # Breakpoint
 391                 push $0x4                       # Int 0x4: #OF
 392                 jmp ex_noc                      # Overflow
 393                 push $0x5                       # Int 0x5: #BR
 394                 jmp ex_noc                      # BOUND range exceeded
 395                 push $0x6                       # Int 0x6: #UD
 396                 jmp ex_noc                      # Invalid opcode
 397                 push $0x7                       # Int 0x7: #NM
 398                 jmp ex_noc                      # Device not available
 399                 push $0x8                       # Int 0x8: #DF
 400                 jmp except                      # Double fault
 401                 push $0xa                       # Int 0xa: #TS
 402                 jmp except                      # Invalid TSS
 403                 push $0xb                       # Int 0xb: #NP
 404                 jmp except                      # Segment not present
 405                 push $0xc                       # Int 0xc: #SS
 406                 jmp except                      # Stack segment fault
 407                 push $0xd                       # Int 0xd: #GP
 408                 jmp ex_v86                      # General protection
 409                 push $0xe                       # Int 0xe: #PF
 410                 jmp except                      # Page fault
 411 intx10:         push $0x10                      # Int 0x10: #MF
 412                 jmp ex_noc                      # Floating-point error
 413 #
 414 # Handle #GP exception.
 415 #
 416 ex_v86:         testb $0x2,0x12(%esp,1)         # V86 mode?
 417                 jz except                       # No
 418                 jmp v86mon                      # To monitor
 419 #
 420 # Save a zero error code.
 421 #
 422 ex_noc:         pushl (%esp,1)                  # Duplicate int no
 423                 movb $0x0,0x4(%esp,1)           # Fake error code
 424 #
 425 # Handle exception.
 426 #
 427 except:         cld                             # String ops inc
 428                 pushl %ds                       # Save
 429                 pushl %es                       #  most
 430                 pusha                           #  registers
 431                 movb $0x6,%al                   # Push loop count
 432                 testb $0x2,0x3a(%esp,1)         # V86 mode?
 433                 jnz except.1                    # Yes
 434                 pushl %gs                       # Set GS
 435                 pushl %fs                       # Set FS
 436                 pushl %ds                       # Set DS
 437                 pushl %es                       # Set ES
 438                 movb $0x2,%al                   # Push loop count
 439                 cmpw $SEL_SCODE,0x44(%esp,1)    # Supervisor mode?
 440                 jne except.1                    # No
 441                 pushl %ss                       # Set SS
 442                 leal 0x50(%esp,1),%eax          # Set
 443                 pushl %eax                      #  ESP
 444                 jmp except.2                    # Join common code
 445 except.1:       pushl 0x50(%esp,1)              # Set GS, FS, DS, ES
 446                 decb %al                        #  (if V86 mode), and
 447                 jne except.1                    #  SS, ESP
 448 except.2:       push $SEL_SDATA                 # Set up
 449                 popl %ds                        #  to
 450                 pushl %ds                       #  address
 451                 popl %es                        #  data
 452                 movl %esp,%ebx                  # Stack frame
 453                 movl $dmpfmt,%esi               # Dump format string
 454                 movl $MEM_BUF,%edi              # Buffer
 455 .`ifdef' PC98
 456                 pushl %eax
 457                 pushl %edx
 458 wait.1:
 459                 inb  $0x60,%al
 460                 testb $0x04,%al
 461                 jz   wait.1
 462                 movb $0xe0,%al
 463                 outb %al,$0x62
 464 wait.2:
 465                 inb  $0x60,%al
 466                 testb $0x01,%al
 467                 jz   wait.2
 468                 xorl %edx,%edx
 469                 inb  $0x62,%al
 470                 movb %al,%dl
 471                 inb  $0x62,%al
 472                 movb %al,%dh
 473                 inb  $0x62,%al
 474                 inb  $0x62,%al
 475                 inb  $0x62,%al
 476                 movl %edx,%eax
 477                 shlw $1,%ax
 478                 movl $BDA_POS,%edx
 479                 movw %ax,(%edx)
 480                 popl  %edx
 481                 popl  %eax
 482 .endif
 483                 pushl %edi                      # Dump to
 484                 call dump                       #  buffer
 485                 popl %esi                       #  and
 486                 call putstr                     #  display
 487                 leal 0x18(%esp,1),%esp          # Discard frame
 488                 popa                            # Restore
 489                 popl %es                        #  registers
 490                 popl %ds                        #  saved
 491                 cmpb $0x3,(%esp,1)              # Breakpoint?
 492                 je except.3                     # Yes
 493                 jmp exit                        # Exit
 494 except.3:       leal 0x8(%esp,1),%esp           # Discard err, int no
 495                 iret                            # From interrupt
 496 #
 497 # Return to user mode from V86 mode.
 498 #
 499 intrtn:         cld                             # String ops inc
 500                 pushl %ds                       # Address
 501                 popl %es                        #  data
 502                 leal 0x3c(%ebp),%edx            # V86 Segment registers
 503                 movl MEM_TSS+TSS_ESP1,%esi      # Link stack pointer
 504                 lodsl                           # INT_V86 args pointer
 505                 movl %esi,%ebx                  # Saved exception frame
 506                 testl %eax,%eax                 # INT_V86 args?
 507                 jz intrtn.2                     # No
 508                 movl $MEM_USR,%edi              # User base
 509                 movl 0x1c(%esi),%ebx            # User ESP
 510                 movl %eax,(%edi,%ebx,1)         # Restore to user stack
 511                 leal 0x8(%edi,%eax,1),%edi      # Arg segment registers
 512                 testb $0x4,-0x6(%edi)           # Return flags?
 513                 jz intrtn.1                     # No
 514                 movl 0x30(%ebp),%eax            # Get V86 flags
 515                 movw %ax,0x18(%esi)             # Set user flags
 516 intrtn.1:       leal 0x10(%esi),%ebx            # Saved exception frame
 517                 xchgl %edx,%esi                 # Segment registers
 518                 movb $0x4,%cl                   # Update seg regs
 519                 rep                             #  in INT_V86
 520                 movsl                           #  args
 521 intrtn.2:       movl %edx,%esi                  # Segment registers
 522                 leal 0x28(%ebp),%edi            # Set up seg
 523                 movb $0x4,%cl                   #  regs for
 524                 rep                             #  later
 525                 movsl                           #  pop
 526                 movl %ebx,%esi                  # Restore exception
 527                 movb $0x5,%cl                   #  frame to
 528                 rep                             #  supervisor
 529                 movsl                           #  stack
 530                 movl %esi,MEM_TSS+TSS_ESP1      # Link stack pointer
 531                 popa                            # Restore
 532                 leal 0x8(%esp,1),%esp           # Discard err, int no
 533                 popl %es                        # Restore
 534                 popl %ds                        #  user
 535                 popl %fs                        #  segment
 536                 popl %gs                        #  registers
 537                 iret                            # To user mode
 538 #
 539 # V86 monitor.
 540 #
 541 v86mon:         cld                             # String ops inc
 542                 pushl $SEL_SDATA                # Set up for
 543                 popl %ds                        #  flat addressing
 544                 pusha                           # Save registers
 545                 movl %esp,%ebp                  # Address stack frame
 546                 movzwl 0x2c(%ebp),%edi          # Load V86 CS
 547                 shll $0x4,%edi                  # To linear
 548                 movl 0x28(%ebp),%esi            # Load V86 IP
 549                 addl %edi,%esi                  # Code pointer
 550                 xorl %ecx,%ecx                  # Zero
 551                 movb $0x2,%cl                   # 16-bit operands
 552                 xorl %eax,%eax                  # Zero
 553 v86mon.1:       lodsb                           # Get opcode
 554                 cmpb $0x66,%al                  # Operand size prefix?
 555                 jne v86mon.2                    # No
 556                 movb $0x4,%cl                   # 32-bit operands
 557                 jmp v86mon.1                    # Continue
 558 v86mon.2:       cmpb $0xf4,%al                  # HLT?
 559                 jne v86mon.3                    # No
 560                 cmpl $inthlt+0x1,%esi           # Is inthlt?
 561                 jne v86mon.7                    # No (ignore)
 562                 jmp intrtn                      # Return to user mode
 563 v86mon.3:       cmpb $0xf,%al                   # Prefixed instruction?
 564                 jne v86mon.4                    # No
 565                 cmpb $0x09,(%esi)               # Is it a WBINVD?
 566                 je v86wbinvd                    # Yes
 567                 cmpb $0x30,(%esi)               # Is it a WRMSR?
 568                 je v86wrmsr                     # Yes
 569                 cmpb $0x32,(%esi)               # Is it a RDMSR?
 570                 je v86rdmsr                     # Yes
 571                 cmpb $0x20,(%esi)               # Is this a
 572                 jne v86mon.4                    #  MOV EAX,CR0
 573                 cmpb $0xc0,0x1(%esi)            #  instruction?
 574                 je v86mov                       # Yes
 575 v86mon.4:       cmpb $0xfa,%al                  # CLI?
 576                 je v86cli                       # Yes
 577                 cmpb $0xfb,%al                  # STI?
 578                 je v86sti                       # Yes
 579                 movzwl 0x38(%ebp),%ebx          # Load V86 SS
 580                 shll $0x4,%ebx                  # To offset
 581                 pushl %ebx                      # Save
 582                 addl 0x34(%ebp),%ebx            # Add V86 SP
 583                 movl 0x30(%ebp),%edx            # Load V86 flags
 584                 cmpb $0x9c,%al                  # PUSHF/PUSHFD?
 585                 je v86pushf                     # Yes
 586                 cmpb $0x9d,%al                  # POPF/POPFD?
 587                 je v86popf                      # Yes
 588                 cmpb $0xcd,%al                  # INT imm8?
 589                 je v86intn                      # Yes
 590                 cmpb $0xcf,%al                  # IRET/IRETD?
 591                 je v86iret                      # Yes
 592                 popl %ebx                       # Restore
 593                 popa                            # Restore
 594                 jmp except                      # Handle exception
 595 v86mon.5:       movl %edx,0x30(%ebp)            # Save V86 flags
 596 v86mon.6:       popl %edx                       # V86 SS adjustment
 597                 subl %edx,%ebx                  # Save V86
 598                 movl %ebx,0x34(%ebp)            #  SP
 599 v86mon.7:       subl %edi,%esi                  # From linear
 600                 movl %esi,0x28(%ebp)            # Save V86 IP
 601                 popa                            # Restore
 602                 leal 0x8(%esp,1),%esp           # Discard int no, error
 603                 iret                            # To V86 mode
 604 #
 605 # Emulate MOV EAX,CR0.
 606 #
 607 v86mov:         movl %cr0,%eax                  # CR0 to
 608                 movl %eax,0x1c(%ebp)            #  saved EAX
 609                 incl %esi                       # Adjust IP
 610 #
 611 # Return from emulating a 0x0f prefixed instruction
 612 #
 613 v86preret:      incl %esi                       # Adjust IP
 614                 jmp v86mon.7                    # Finish up
 615 #
 616 # Emulate WBINVD
 617 #
 618 v86wbinvd:      wbinvd                          # Write back and invalidate
 619                                                 #  cache
 620                 jmp v86preret                   # Finish up
 621 #
 622 # Emulate WRMSR
 623 #
 624 v86wrmsr:       movl 0x18(%ebp),%ecx            # Get user's %ecx (MSR to write)
 625                 movl 0x14(%ebp),%edx            # Load the value
 626                 movl 0x1c(%ebp),%eax            #  to write
 627                 wrmsr                           # Write MSR
 628                 jmp v86preret                   # Finish up
 629 #
 630 # Emulate RDMSR
 631 #
 632 v86rdmsr:       movl 0x18(%ebp),%ecx            # MSR to read
 633                 rdmsr                           # Read the MSR
 634                 movl %eax,0x1c(%ebp)            # Return the value of
 635                 movl %edx,0x14(%ebp)            #  the MSR to the user
 636                 jmp v86preret                   # Finish up
 637 #
 638 # Emulate CLI.
 639 #
 640 v86cli:         andb $~0x2,0x31(%ebp)           # Clear IF
 641                 jmp v86mon.7                    # Finish up
 642 #
 643 # Emulate STI.
 644 #
 645 v86sti:         orb $0x2,0x31(%ebp)             # Set IF
 646                 jmp v86mon.7                    # Finish up
 647 #
 648 # Emulate PUSHF/PUSHFD.
 649 #
 650 v86pushf:       subl %ecx,%ebx                  # Adjust SP
 651                 cmpb $0x4,%cl                   # 32-bit
 652                 je v86pushf.1                   # Yes
 653                 data16                          # 16-bit
 654 v86pushf.1:     movl %edx,(%ebx)                # Save flags
 655                 jmp v86mon.6                    # Finish up
 656 #
 657 # Emulate IRET/IRETD.
 658 #
 659 v86iret:        movzwl (%ebx),%esi              # Load V86 IP
 660                 movzwl 0x2(%ebx),%edi           # Load V86 CS
 661                 leal 0x4(%ebx),%ebx             # Adjust SP
 662                 movl %edi,0x2c(%ebp)            # Save V86 CS
 663                 xorl %edi,%edi                  # No ESI adjustment
 664 #
 665 # Emulate POPF/POPFD (and remainder of IRET/IRETD).
 666 #
 667 v86popf:        cmpb $0x4,%cl                   # 32-bit?
 668                 je v86popf.1                    # Yes
 669                 movl %edx,%eax                  # Initialize
 670                 data16                          # 16-bit
 671 v86popf.1:      movl (%ebx),%eax                # Load flags
 672                 addl %ecx,%ebx                  # Adjust SP
 673                 andl $V86_FLG,%eax              # Merge
 674                 andl $~V86_FLG,%edx             #  the
 675                 orl %eax,%edx                   #  flags
 676                 jmp v86mon.5                    # Finish up
 677 #
 678 # trap int 15, function 87
 679 # reads %es:%si from saved registers on stack to find a GDT containing
 680 # source and destination locations
 681 # reads count of words from saved %cx
 682 # returns success by setting %ah to 0
 683 #
 684 int15_87:       pushl %eax                      # Save
 685                 pushl %ebx                      #  some information
 686                 pushl %esi                      #  onto the stack.
 687                 pushl %edi
 688                 xorl %eax,%eax                  # clean EAX
 689                 xorl %ebx,%ebx                  # clean EBX
 690                 movl 0x4(%ebp),%esi             # Get user's ESI
 691                 movl 0x3C(%ebp),%ebx            # store ES
 692                 movw %si,%ax                    # store SI
 693                 shll $0x4,%ebx                  # Make it a seg.
 694                 addl %eax,%ebx                  # ebx=(es<<4)+si
 695                 movb 0x14(%ebx),%al             # Grab the
 696                 movb 0x17(%ebx),%ah             #  necessary
 697                 shll $0x10,%eax                 #  information
 698                 movw 0x12(%ebx),%ax             #  from
 699                 movl %eax,%esi                  #  the
 700                 movb 0x1c(%ebx),%al             #  GDT in order to
 701                 movb 0x1f(%ebx),%ah             #  have %esi offset
 702                 shll $0x10,%eax                 #  of source and %edi
 703                 movw 0x1a(%ebx),%ax             #  of destination.
 704                 movl %eax,%edi
 705                 pushl %ds                       # Make:
 706                 popl %es                        # es = ds
 707                 pushl %ecx                      # stash ECX
 708                 xorl %ecx,%ecx                  # highw of ECX is clear
 709                 movw 0x18(%ebp),%cx             # Get user's ECX
 710                 shll $0x1,%ecx                  # Convert from num words to num
 711                                                 #  bytes
 712                 rep                             # repeat...
 713                 movsb                           #  perform copy.
 714                 popl %ecx                       # Restore
 715                 popl %edi
 716                 popl %esi                       #  previous
 717                 popl %ebx                       #  register
 718                 popl %eax                       #  values.
 719                 movb $0x0,0x1d(%ebp)            # set ah = 0 to indicate
 720                                                 #  success
 721                 andb $0xfe,%dl                  # clear CF
 722                 jmp v86mon.5                    # Finish up
 723
 724 #
 725 # Reboot the machine by setting the reboot flag and exiting
 726 #
 727 reboot:         orb $0x1,btx_hdr+0x7            # Set the reboot flag
 728                 jmp exit                        # Terminate BTX and reboot
 729
 730 #
 731 # Emulate INT imm8... also make sure to check if it's int 15/87
 732 #
 733 v86intn:        lodsb                           # Get int no
 734                 cmpb $0x19,%al                  # is it int 19?
 735                 je reboot                       #  yes, reboot the machine
 736                 cmpb $0x15,%al                  # is it int 15?
 737                 jne v86intn.3                   #  no, skip parse
 738                 pushl %eax                      # stash EAX
 739                 movl 0x1c(%ebp),%eax            # user's saved EAX
 740                 cmpb $0x87,%ah                  # is it the memcpy subfunction?
 741                 jne v86intn.1                   #  no, keep checking
 742                 popl %eax                       # get the stack straight
 743                 jmp int15_87                    # it's our cue
 744 v86intn.1:      cmpw $0x4f53,%ax                # is it the delete key callout?
 745                 jne v86intn.2                   #  no, handle the int normally
 746                 movb BDA_KEYFLAGS,%al           # get the shift key state
 747 .`ifdef' PC98
 748                 andb $0x18,%al                  # mask off just Ctrl and Alt
 749                 cmpb $0x18,%al                  # are both Ctrl and Alt down?
 750 .else
 751                 andb $0xc,%al                   # mask off just Ctrl and Alt
 752                 cmpb $0xc,%al                   # are both Ctrl and Alt down?
 753 .endif
 754                 jne v86intn.2                   #  no, handle the int normally
 755                 popl %eax                       # restore EAX
 756                 jmp reboot                      # reboot the machine
 757 v86intn.2:      popl %eax                       # restore EAX
 758 v86intn.3:      subl %edi,%esi                  # From
 759                 shrl $0x4,%edi                  #  linear
 760                 movw %dx,-0x2(%ebx)             # Save flags
 761                 movw %di,-0x4(%ebx)             # Save CS
 762                 leal -0x6(%ebx),%ebx            # Adjust SP
 763                 movw %si,(%ebx)                 # Save IP
 764                 shll $0x2,%eax                  # Scale
 765                 movzwl (%eax),%esi              # Load IP
 766                 movzwl 0x2(%eax),%edi           # Load CS
 767                 movl %edi,0x2c(%ebp)            # Save CS
 768                 xorl %edi,%edi                  # No ESI adjustment
 769                 andb $~0x1,%dh                  # Clear TF
 770                 jmp v86mon.5                    # Finish up
 771 #
 772 # Hardware interrupt jump table.
 773 #
 774 intx20:         push $0x8                       # Int 0x20: IRQ0
 775                 jmp int_hw                      # V86 int 0x8
 776                 push $0x9                       # Int 0x21: IRQ1
 777                 jmp int_hw                      # V86 int 0x9
 778                 push $0xa                       # Int 0x22: IRQ2
 779                 jmp int_hw                      # V86 int 0xa
 780                 push $0xb                       # Int 0x23: IRQ3
 781                 jmp int_hw                      # V86 int 0xb
 782                 push $0xc                       # Int 0x24: IRQ4
 783                 jmp int_hw                      # V86 int 0xc
 784                 push $0xd                       # Int 0x25: IRQ5
 785                 jmp int_hw                      # V86 int 0xd
 786                 push $0xe                       # Int 0x26: IRQ6
 787                 jmp int_hw                      # V86 int 0xe
 788                 push $0xf                       # Int 0x27: IRQ7
 789                 jmp int_hw                      # V86 int 0xf
 790 .`ifdef' PC98
 791                 push $0x10                      # Int 0x28: IRQ8
 792                 jmp int_hw                      # V86 int 0x10
 793                 push $0x11                      # Int 0x29: IRQ9
 794                 jmp int_hw                      # V86 int 0x11
 795                 push $0x12                      # Int 0x2a: IRQ10
 796                 jmp int_hw                      # V86 int 0x12
 797                 push $0x13                      # Int 0x2b: IRQ11
 798                 jmp int_hw                      # V86 int 0x13
 799                 push $0x14                      # Int 0x2c: IRQ12
 800                 jmp int_hw                      # V86 int 0x14
 801                 push $0x15                      # Int 0x2d: IRQ13
 802                 jmp int_hw                      # V86 int 0x15
 803                 push $0x16                      # Int 0x2e: IRQ14
 804                 jmp int_hw                      # V86 int 0x16
 805                 push $0x17                      # Int 0x2f: IRQ15
 806                 jmp int_hw                      # V86 int 0x17
 807 .else
 808                 push $0x70                      # Int 0x28: IRQ8
 809                 jmp int_hw                      # V86 int 0x70
 810                 push $0x71                      # Int 0x29: IRQ9
 811                 jmp int_hw                      # V86 int 0x71
 812                 push $0x72                      # Int 0x2a: IRQ10
 813                 jmp int_hw                      # V86 int 0x72
 814                 push $0x73                      # Int 0x2b: IRQ11
 815                 jmp int_hw                      # V86 int 0x73
 816                 push $0x74                      # Int 0x2c: IRQ12
 817                 jmp int_hw                      # V86 int 0x74
 818                 push $0x75                      # Int 0x2d: IRQ13
 819                 jmp int_hw                      # V86 int 0x75
 820                 push $0x76                      # Int 0x2e: IRQ14
 821                 jmp int_hw                      # V86 int 0x76
 822                 push $0x77                      # Int 0x2f: IRQ15
 823                 jmp int_hw                      # V86 int 0x77
 824 .endif
 825 #
 826 # Reflect hardware interrupts.
 827 #
 828 int_hw:         testb $0x2,0xe(%esp,1)          # V86 mode?
 829                 jz intusr                       # No
 830                 pushl $SEL_SDATA                # Address
 831                 popl %ds                        #  data
 832                 xchgl %eax,(%esp,1)             # Swap EAX, int no
 833                 pushl %ebp                      # Address
 834                 movl %esp,%ebp                  #  stack frame
 835                 pushl %ebx                      # Save
 836                 shll $0x2,%eax                  # Get int
 837                 movl (%eax),%eax                #  vector
 838                 subl $0x6,0x14(%ebp)            # Adjust V86 ESP
 839                 movzwl 0x18(%ebp),%ebx          # V86 SS
 840                 shll $0x4,%ebx                  #  * 0x10
 841                 addl 0x14(%ebp),%ebx            #  + V86 ESP
 842                 xchgw %ax,0x8(%ebp)             # Swap V86 IP
 843                 rorl $0x10,%eax                 # Swap words
 844                 xchgw %ax,0xc(%ebp)             # Swap V86 CS
 845                 roll $0x10,%eax                 # Swap words
 846                 movl %eax,(%ebx)                # CS:IP for IRET
 847                 movl 0x10(%ebp),%eax            # V86 flags
 848                 movw %ax,0x4(%ebx)              # Flags for IRET
 849                 andb $~0x3,0x11(%ebp)           # Clear IF, TF
 850                 popl %ebx                       # Restore
 851                 popl %ebp                       #  saved
 852                 popl %eax                       #  registers
 853                 iret                            # To V86 mode
 854 #
 855 # Invoke V86 interrupt from user mode, with arguments.
 856 #
 857 intx31:         stc                             # Have btx_v86
 858                 pushl %eax                      # Missing int no
 859 #
 860 # Invoke V86 interrupt from user mode.
 861 #
 862 intusr:         std                             # String ops dec
 863                 pushl %eax                      # Expand
 864                 pushl %eax                      #  stack
 865                 pushl %eax                      #  frame
 866                 pusha                           # Save
 867                 pushl %gs                       # Save
 868                 movl %esp,%eax                  #  seg regs
 869                 pushl %fs                       #  and
 870                 pushl %ds                       #  point
 871                 pushl %es                       #  to them
 872                 push $SEL_SDATA                 # Set up
 873                 popl %ds                        #  to
 874                 pushl %ds                       #  address
 875                 popl %es                        #  data
 876                 movl $MEM_USR,%ebx              # User base
 877                 movl %ebx,%edx                  #  address
 878                 jc intusr.1                     # If btx_v86
 879                 xorl %edx,%edx                  # Control flags
 880                 xorl %ebp,%ebp                  # btx_v86 pointer
 881 intusr.1:       leal 0x50(%esp,1),%esi          # Base of frame
 882                 pushl %esi                      # Save
 883                 addl -0x4(%esi),%ebx            # User ESP
 884                 movl MEM_TSS+TSS_ESP1,%edi      # Link stack pointer
 885                 leal -0x4(%edi),%edi            # Adjust for push
 886                 xorl %ecx,%ecx                  # Zero
 887                 movb $0x5,%cl                   # Push exception
 888                 rep                             #  frame on
 889                 movsl                           #  link stack
 890                 xchgl %eax,%esi                 # Saved seg regs
 891                 movl 0x40(%esp,1),%eax          # Get int no
 892                 testl %edx,%edx                 # Have btx_v86?
 893                 jz intusr.2                     # No
 894                 movl (%ebx),%ebp                # btx_v86 pointer
 895                 movb $0x4,%cl                   # Count
 896                 addl %ecx,%ebx                  # Adjust for pop
 897                 rep                             # Push saved seg regs
 898                 movsl                           #  on link stack
 899                 addl %ebp,%edx                  # Flatten btx_v86 ptr
 900                 leal 0x14(%edx),%esi            # Seg regs pointer
 901                 movl 0x4(%edx),%eax             # Get int no/address
 902                 movzwl 0x2(%edx),%edx           # Get control flags
 903 intusr.2:       movl %ebp,(%edi)                # Push btx_v86 and
 904                 movl %edi,MEM_TSS+TSS_ESP1      #  save link stack ptr
 905                 popl %edi                       # Base of frame
 906                 xchgl %eax,%ebp                 # Save intno/address
 907                 movl 0x48(%esp,1),%eax          # Get flags
 908                 testb $0x2,%dl                  # Simulate CALLF?
 909                 jnz intusr.3                    # Yes
 910                 decl %ebx                       # Push flags
 911                 decl %ebx                       #  on V86
 912                 movw %ax,(%ebx)                 #  stack
 913 intusr.3:       movb $0x4,%cl                   # Count
 914                 subl %ecx,%ebx                  # Push return address
 915                 movl $inthlt,(%ebx)             #  on V86 stack
 916                 rep                             # Copy seg regs to
 917                 movsl                           #  exception frame
 918                 xchgl %eax,%ecx                 # Save flags
 919                 movl %ebx,%eax                  # User ESP
 920                 subl $V86_STK,%eax              # Less bytes
 921                 ja intusr.4                     #  to
 922                 xorl %eax,%eax                  #  keep
 923 intusr.4:       shrl $0x4,%eax                  # Gives segment
 924                 stosl                           # Set SS
 925                 shll $0x4,%eax                  # To bytes
 926                 xchgl %eax,%ebx                 # Swap
 927                 subl %ebx,%eax                  # Gives offset
 928                 stosl                           # Set ESP
 929                 xchgl %eax,%ecx                 # Get flags
 930                 btsl $0x11,%eax                 # Set VM
 931                 andb $~0x1,%ah                  # Clear TF
 932                 stosl                           # Set EFL
 933                 xchgl %eax,%ebp                 # Get int no/address
 934                 testb $0x1,%dl                  # Address?
 935                 jnz intusr.5                    # Yes
 936                 shll $0x2,%eax                  # Scale
 937                 movl (%eax),%eax                # Load int vector
 938 intusr.5:       movl %eax,%ecx                  # Save
 939                 shrl $0x10,%eax                 # Gives segment
 940                 stosl                           # Set CS
 941                 movw %cx,%ax                    # Restore
 942                 stosl                           # Set EIP
 943                 leal 0x10(%esp,1),%esp          # Discard seg regs
 944                 popa                            # Restore
 945                 iret                            # To V86 mode
 946 #
 947 # System Call.
 948 #
 949 intx30:         cmpl $SYS_EXEC,%eax             # Exec system call?
 950                 jne intx30.1                    # No
 951                 pushl %ss                       # Set up
 952                 popl %es                        #  all
 953                 pushl %es                       #  segment
 954                 popl %ds                        #  registers
 955                 pushl %ds                       #  for the
 956                 popl %fs                        #  program
 957                 pushl %fs                       #  we're
 958                 popl %gs                        #  invoking
 959                 movl $MEM_USR,%eax              # User base address
 960                 addl 0xc(%esp,1),%eax           # Change to user
 961                 leal 0x4(%eax),%esp             #  stack
 962 ifdef(`PAGING',`
 963                 movl %cr0,%eax                  # Turn
 964                 andl $~0x80000000,%eax          #  off
 965                 movl %eax,%cr0                  #  paging
 966                 xorl %eax,%eax                  # Flush
 967                 movl %eax,%cr3                  #  TLB
 968 ')
 969                 popl %eax                       # Call
 970                 call *%eax                      #  program
 971 intx30.1:       incb %ss:btx_hdr+0x7            # Flag reboot
 972                 jmp exit                        # Exit
 973 #
 974 # Dump structure [EBX] to [EDI], using format string [ESI].
 975 #
 976 dump.0:         stosb                           # Save char
 977 dump:           lodsb                           # Load char
 978                 testb %al,%al                   # End of string?
 979                 jz dump.10                      # Yes
 980                 testb $0x80,%al                 # Control?
 981                 jz dump.0                       # No
 982                 movb %al,%ch                    # Save control
 983                 movb $'=',%al                   # Append
 984                 stosb                           #  '='
 985                 lodsb                           # Get offset
 986                 pushl %esi                      # Save
 987                 movsbl %al,%esi                 # To
 988                 addl %ebx,%esi                  #  pointer
 989                 testb $DMP_X16,%ch              # Dump word?
 990                 jz dump.1                       # No
 991                 lodsw                           # Get and
 992                 call hex16                      #  dump it
 993 dump.1:         testb $DMP_X32,%ch              # Dump long?
 994                 jz dump.2                       # No
 995                 lodsl                           # Get and
 996                 call hex32                      #  dump it
 997 dump.2:         testb $DMP_MEM,%ch              # Dump memory?
 998                 jz dump.8                       # No
 999                 pushl %ds                       # Save
1000                 testb $0x2,0x52(%ebx)           # V86 mode?
1001                 jnz dump.3                      # Yes
1002                 verr 0x4(%esi)                  # Readable selector?
1003                 jnz dump.3                      # No
1004                 ldsl (%esi),%esi                # Load pointer
1005                 jmp dump.4                      # Join common code
1006 dump.3:         lodsl                           # Set offset
1007                 xchgl %eax,%edx                 # Save
1008                 lodsl                           # Get segment
1009                 shll $0x4,%eax                  #  * 0x10
1010                 addl %edx,%eax                  #  + offset
1011                 xchgl %eax,%esi                 # Set pointer
1012 dump.4:         movb $0x10,%cl                  # Bytes to dump
1013 dump.5:         lodsb                           # Get byte and
1014                 call hex8                       #  dump it
1015                 decb %cl                        # Keep count
1016                 jz dump.7                       # If done
1017                 movb $'-',%al                   # Separator
1018                 cmpb $0x8,%cl                   # Half way?
1019                 je dump.6                       # Yes
1020                 movb $' ',%al                   # Use space
1021 dump.6:         stosb                           # Save separator
1022                 jmp dump.5                      # Continue
1023 dump.7:         popl %ds                        # Restore
1024 dump.8:         popl %esi                       # Restore
1025                 movb $0xa,%al                   # Line feed
1026                 testb $DMP_EOL,%ch              # End of line?
1027                 jnz dump.9                      # Yes
1028                 movb $' ',%al                   # Use spaces
1029                 stosb                           # Save one
1030 dump.9:         jmp dump.0                      # Continue
1031 dump.10:        stosb                           # Terminate string
1032                 ret                             # To caller
1033 #
1034 # Convert EAX, AX, or AL to hex, saving the result to [EDI].
1035 #
1036 hex32:          pushl %eax                      # Save
1037                 shrl $0x10,%eax                 # Do upper
1038                 call hex16                      #  16
1039                 popl %eax                       # Restore
1040 hex16:          call hex16.1                    # Do upper 8
1041 hex16.1:        xchgb %ah,%al                   # Save/restore
1042 hex8:           pushl %eax                      # Save
1043                 shrb $0x4,%al                   # Do upper
1044                 call hex8.1                     #  4
1045                 popl %eax                       # Restore
1046 hex8.1:         andb $0xf,%al                   # Get lower 4
1047                 cmpb $0xa,%al                   # Convert
1048                 sbbb $0x69,%al                  #  to hex
1049                 das                             #  digit
1050                 orb $0x20,%al                   # To lower case
1051                 stosb                           # Save char
1052                 ret                             # (Recursive)
1053 #
1054 # Output zero-terminated string [ESI] to the console.
1055 #
1056 putstr.0:       call putchr                     # Output char
1057 putstr:         lodsb                           # Load char
1058                 testb %al,%al                   # End of string?
1059                 jnz putstr.0                    # No
1060                 ret                             # To caller
1061 #
1062 # Output character AL to the console.
1063 #
1064 putchr:         pusha                           # Save
1065                 xorl %ecx,%ecx                  # Zero for loops
1066                 movb $SCR_MAT,%ah               # Mode/attribute
1067                 movl $BDA_POS,%ebx              # BDA pointer
1068                 movw (%ebx),%dx                 # Cursor position
1069 .`ifdef' PC98
1070                 movl $0xa0000,%edi
1071 .else
1072                 movl $0xb8000,%edi              # Regen buffer (color)
1073                 cmpb %ah,BDA_SCR-BDA_POS(%ebx)  # Mono mode?
1074                 jne putchr.1                    # No
1075                 xorw %di,%di                    # Regen buffer (mono)
1076 .endif
1077 putchr.1:       cmpb $0xa,%al                   # New line?
1078                 je putchr.2                     # Yes
1079 .`ifdef' PC98
1080                 movw %dx,%cx
1081                 movb %al,(%edi,%ecx,1)          # Write char
1082                 addl $0x2000,%ecx
1083                 movb %ah,(%edi,%ecx,1)          # Write attr
1084                 addw $0x02,%dx
1085                 jmp putchr.3
1086 putchr.2:       movw %dx,%ax
1087                 movb $SCR_COL*2,%dl
1088                 div %dl
1089                 incb %al
1090                 mul %dl
1091                 movw %ax,%dx
1092 putchr.3:       cmpw $SCR_ROW*SCR_COL*2,%dx
1093 .else
1094                 xchgl %eax,%ecx                 # Save char
1095                 movb $SCR_COL,%al               # Columns per row
1096                 mulb %dh                        #  * row position
1097                 addb %dl,%al                    #  + column
1098                 adcb $0x0,%ah                   #  position
1099                 shll %eax                       #  * 2
1100                 xchgl %eax,%ecx                 # Swap char, offset
1101                 movw %ax,(%edi,%ecx,1)          # Write attr:char
1102                 incl %edx                       # Bump cursor
1103                 cmpb $SCR_COL,%dl               # Beyond row?
1104                 jb putchr.3                     # No
1105 putchr.2:       xorb %dl,%dl                    # Zero column
1106                 incb %dh                        # Bump row
1107 putchr.3:       cmpb $SCR_ROW,%dh               # Beyond screen?
1108 .endif
1109                 jb putchr.4                     # No
1110                 leal 2*SCR_COL(%edi),%esi       # New top line
1111                 movw $(SCR_ROW-1)*SCR_COL/2,%cx # Words to move
1112                 rep                             # Scroll
1113                 movsl                           #  screen
1114                 movb $' ',%al                   # Space
1115 .`ifdef' PC98
1116                 xorb %ah,%ah
1117 .endif
1118                 movb $SCR_COL,%cl               # Columns to clear
1119                 rep                             # Clear
1120                 stosw                           #  line
1121 .`ifdef' PC98
1122                 movw $(SCR_ROW-1)*SCR_COL*2,%dx
1123 .else
1124                 movb $SCR_ROW-1,%dh             # Bottom line
1125 .endif
1126 putchr.4:       movw %dx,(%ebx)                 # Update position
1127                 popa                            # Restore
1128                 ret                             # To caller
1129
1130                 .p2align 4
1131 #
1132 # Global descriptor table.
1133 #
1134 gdt:            .word 0x0,0x0,0x0,0x0           # Null entry
1135                 .word 0xffff,0x0,0x9a00,0xcf    # SEL_SCODE
1136                 .word 0xffff,0x0,0x9200,0xcf    # SEL_SDATA
1137                 .word 0xffff,0x0,0x9a00,0x0     # SEL_RCODE
1138                 .word 0xffff,0x0,0x9200,0x0     # SEL_RDATA
1139                 .word 0xffff,MEM_USR,0xfa00,0xcf# SEL_UCODE
1140                 .word 0xffff,MEM_USR,0xf200,0xcf# SEL_UDATA
1141                 .word _TSSLM,MEM_TSS,0x8900,0x0 # SEL_TSS
1142 gdt.1:
1143 #
1144 # Pseudo-descriptors.
1145 #
1146 gdtdesc:        .word gdt.1-gdt-1,gdt,0x0       # GDT
1147 idtdesc:        .word _IDTLM,MEM_IDT,0x0        # IDT
1148 ivtdesc:        .word 0x400-0x0-1,0x0,0x0       # IVT
1149 #
1150 # IDT construction control string.
1151 #
1152 idtctl:         .byte 0x10,  0x8e               # Int 0x0-0xf
1153                 .word 0x7dfb,intx00             #  (exceptions)
1154                 .byte 0x10,  0x8e               # Int 0x10
1155                 .word 0x1,   intx10             #  (exception)
1156                 .byte 0x10,  0x8e               # Int 0x20-0x2f
1157                 .word 0xffff,intx20             #  (hardware)
1158                 .byte 0x1,   0xee               # int 0x30
1159                 .word 0x1,   intx30             #  (system call)
1160                 .byte 0x2,   0xee               # Int 0x31-0x32
1161                 .word 0x1,   intx31             #  (V86, null)
1162                 .byte 0x0                       # End of string
1163 #
1164 # Dump format string.
1165 #
1166 dmpfmt:         .byte '\n'                      # "\n"
1167                 .ascii "int"                    # "int="
1168                 .byte 0x80|DMP_X32,        0x40 # "00000000  "
1169                 .ascii "err"                    # "err="
1170                 .byte 0x80|DMP_X32,        0x44 # "00000000  "
1171                 .ascii "efl"                    # "efl="
1172                 .byte 0x80|DMP_X32,        0x50 # "00000000  "
1173                 .ascii "eip"                    # "eip="
1174                 .byte 0x80|DMP_X32|DMP_EOL,0x48 # "00000000\n"
1175                 .ascii "eax"                    # "eax="
1176                 .byte 0x80|DMP_X32,        0x34 # "00000000  "
1177                 .ascii "ebx"                    # "ebx="
1178                 .byte 0x80|DMP_X32,        0x28 # "00000000  "
1179                 .ascii "ecx"                    # "ecx="
1180                 .byte 0x80|DMP_X32,        0x30 # "00000000  "
1181                 .ascii "edx"                    # "edx="
1182                 .byte 0x80|DMP_X32|DMP_EOL,0x2c # "00000000\n"
1183                 .ascii "esi"                    # "esi="
1184                 .byte 0x80|DMP_X32,        0x1c # "00000000  "
1185                 .ascii "edi"                    # "edi="
1186                 .byte 0x80|DMP_X32,        0x18 # "00000000  "
1187                 .ascii "ebp"                    # "ebp="
1188                 .byte 0x80|DMP_X32,        0x20 # "00000000  "
1189                 .ascii "esp"                    # "esp="
1190                 .byte 0x80|DMP_X32|DMP_EOL,0x0  # "00000000\n"
1191                 .ascii "cs"                     # "cs="
1192                 .byte 0x80|DMP_X16,        0x4c # "0000  "
1193                 .ascii "ds"                     # "ds="
1194                 .byte 0x80|DMP_X16,        0xc  # "0000  "
1195                 .ascii "es"                     # "es="
1196                 .byte 0x80|DMP_X16,        0x8  # "0000  "
1197                 .ascii "  "                     # "  "
1198                 .ascii "fs"                     # "fs="
1199                 .byte 0x80|DMP_X16,        0x10 # "0000  "
1200                 .ascii "gs"                     # "gs="
1201                 .byte 0x80|DMP_X16,        0x14 # "0000  "
1202                 .ascii "ss"                     # "ss="
1203                 .byte 0x80|DMP_X16|DMP_EOL,0x4  # "0000\n"
1204                 .ascii "cs:eip"                 # "cs:eip="
1205                 .byte 0x80|DMP_MEM|DMP_EOL,0x48 # "00 00 ... 00 00\n"
1206                 .ascii "ss:esp"                 # "ss:esp="
1207                 .byte 0x80|DMP_MEM|DMP_EOL,0x0  # "00 00 ... 00 00\n"
1208                 .asciz "BTX halted"             # End
1209 #
1210 # End of BTX memory.
1211 #
1212                 .p2align 4
1213 break: