2 * Copyright (c) 1998 Robert Nordier
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
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
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_ESPR,0x5e00 # Real mode stack
25 .set MEM_IDT,0x5e00 # IDT
26 .set MEM_TSS,0x5f98 # TSS
27 .set MEM_MAP,0x6000 # I/O bit map
28 .set MEM_TSS_END,0x7fff # End of TSS
29 .set MEM_ORG,0x9000 # BTX code
30 .set MEM_USR,0xa000 # Start of user memory
34 .set PAG_SIZ,0x1000 # Page size
35 .set PAG_CNT,0x1000 # Pages to map
39 .set PSL_RESERVED_DEFAULT,0x00000002
40 .set PSL_T,0x00000100 # Trap flag
41 .set PSL_I,0x00000200 # Interrupt enable flag
42 .set PSL_VM,0x00020000 # Virtual 8086 mode flag
43 .set PSL_AC,0x00040000 # Alignment check flag
47 .set SEL_SCODE,0x8 # Supervisor code
48 .set SEL_SDATA,0x10 # Supervisor data
49 .set SEL_RCODE,0x18 # Real mode code
50 .set SEL_RDATA,0x20 # Real mode data
51 .set SEL_UCODE,0x28|3 # User code
52 .set SEL_UDATA,0x30|3 # User data
53 .set SEL_TSS,0x38 # TSS
55 * Task state segment fields.
57 .set TSS_ESP0,0x4 # PL 0 ESP
58 .set TSS_SS0,0x8 # PL 0 SS
59 .set TSS_MAP,0x66 # I/O bit map base
63 .set SYS_EXIT,0x0 # Exit
64 .set SYS_EXEC,0x1 # Exec
66 * Fields in V86 interface structure.
68 .set V86_CTL,0x0 # Control flags
69 .set V86_ADDR,0x4 # Int number/address
70 .set V86_ES,0x8 # V86 ES
71 .set V86_DS,0xc # V86 DS
72 .set V86_FS,0x10 # V86 FS
73 .set V86_GS,0x14 # V86 GS
77 .set V86F_ADDR,0x10000 # Segment:offset address
78 .set V86F_CALLF,0x20000 # Emulate far call
79 .set V86F_FLAGS,0x40000 # Return flags
81 * Dump format control bytes.
83 .set DMP_X16,0x1 # Word
84 .set DMP_X32,0x2 # Long
85 .set DMP_MEM,0x4 # Memory
86 .set DMP_EOL,0x8 # End of line
88 * Screen defaults and assumptions.
90 .set SCR_MAT,0xe1 # Mode/attribute
91 .set SCR_COL,0x50 # Columns per row
92 .set SCR_ROW,0x19 # Rows per screen
94 * BIOS Data Area locations.
96 .set BDA_MEM,0x501 # Free memory
97 .set BDA_POS,0x53e # Cursor position
99 * Derivations, for brevity.
101 .set _ESP0H,MEM_ESP0>>0x8 # Byte 1 of ESP0
102 .set _TSSIO,MEM_MAP-MEM_TSS # TSS I/O base
103 .set _TSSLM,MEM_TSS_END-MEM_TSS # TSS limit
104 .set _IDTLM,MEM_TSS-MEM_IDT-1 # IDT limit
110 start: # Start of code
114 btx_hdr: .byte 0xeb # Machine ID
115 .byte 0xe # Header size
117 .byte 0x1 # Major version
118 .byte 0x2 # Minor version
119 .byte BTX_FLAGS # Flags
120 .word PAG_CNT-MEM_ORG>>0xc # Paging control
121 .word break-start # Text size
122 .long 0x0 # Entry address
124 * Initialization routine.
126 init: cli # Disable interrupts
127 xor %ax,%ax # Zero/segment
129 mov $MEM_ESP0,%sp # stack
130 mov %ax,%es # Address
137 mov $MEM_IDT,%di # Memory to initialize
138 mov $(MEM_ORG-MEM_IDT)/2,%cx # Words to zero
142 * Update real mode IDT for reflecting hardware interrupts.
144 mov $intr20,%bx # Address first handler
145 mov $0x10,%cx # Number of handlers
146 mov $0x20*4,%di # First real mode IDT entry
147 init.0: mov %bx,(%di) # Store IP
148 inc %di # Address next
151 add $4,%bx # Next handler
152 loop init.0 # Next IRQ
157 mov $idtctl,%si # Control string
158 init.1: lodsb # Get entry
160 xchg %ax,%cx # as word
161 jcxz init.4 # If done
163 xchg %ax,%dx # P:DPL:type
166 lodsw # Get handler offset
167 mov $SEL_SCODE,%dh # Segment selector
168 init.2: shr %bx # Handle this int?
170 mov %ax,(%di) # Set handler offset
171 mov %dh,0x2(%di) # and selector
172 mov %dl,0x5(%di) # Set P:DPL:type
173 add $0x4,%ax # Next handler
174 init.3: lea 0x8(%di),%di # Next entry
175 loop init.2 # Till set done
176 jmp init.1 # Continue
180 init.4: movb $_ESP0H,TSS_ESP0+1(%di) # Set ESP0
181 movb $SEL_SDATA,TSS_SS0(%di) # Set SS0
182 movb $_TSSIO,TSS_MAP(%di) # Set I/O bit map base
184 * Bring up the system.
186 mov $0x2820,%bx # Set protected mode
187 callw setpic # IRQ offsets
188 lidt idtdesc # Set IDT
189 lgdt gdtdesc # Set GDT
190 mov %cr0,%eax # Switch to protected
193 ljmp $SEL_SCODE,$init.8 # To 32-bit code
195 init.8: xorl %ecx,%ecx # Zero
196 movb $SEL_SDATA,%cl # To 32-bit
201 movb $SEL_TSS,%cl # Set task
203 movl $MEM_USR,%edx # User base address
204 movzwl %ss:BDA_MEM,%eax # Get free memory
207 shll $0x11,%eax # To bytes
208 subl $0x1000,%eax # Less arg space
209 subl %edx,%eax # Less base
210 movb $SEL_UDATA,%cl # User data selector
213 push $0x202 # Set flags (IF set)
214 push $SEL_UCODE # Set CS
215 pushl btx_hdr+0xc # Set EIP
221 movb $0x7,%cl # Set remaining
222 init.9: push $0x0 # general
223 loop init.9 # registers
225 call sio_init # setup the serial console
227 popa # and initialize
228 popl %es # Initialize
236 exit: cli # Disable interrupts
237 movl $MEM_ESP0,%esp # Clear stack
241 movl %cr0,%eax # Get CR0
242 andl $~0x80000000,%eax # Disable
243 movl %eax,%cr0 # paging
244 xorl %ecx,%ecx # Zero
245 movl %ecx,%cr3 # Flush TLB
247 * Restore the GDT in case we caught a kernel trap.
249 lgdt gdtdesc # Set GDT
253 ljmpw $SEL_RCODE,$exit.1 # Reload CS
255 exit.1: mov $SEL_RDATA,%cl # 16-bit selector
256 mov %cx,%ss # Reload SS
258 mov %cx,%es # remaining
259 mov %cx,%fs # segment
260 mov %cx,%gs # registers
262 * To real-address mode.
265 mov %eax,%cr0 # real mode
266 ljmp $0x0,$exit.2 # Reload CS
267 exit.2: xor %ax,%ax # Real mode segment
268 mov %ax,%ss # Reload SS
269 mov %ax,%ds # Address data
270 mov $0x1008,%bx # Set real mode
271 callw setpic # IRQ offsets
272 lidt ivtdesc # Set IVT
274 * Reboot or await reset.
276 sti # Enable interrupts
277 testb $0x1,btx_hdr+0x7 # Reboot?
278 exit.3: jz exit.3 # No
282 outb %al,$0xf0 # reboot the machine
285 * Set IRQ offsets by reprogramming 8259A PICs.
287 setpic: in $0x02,%al # Save master
289 in $0x0a,%al # Save slave
291 movb $0x11,%al # ICW1 to
292 outb %al,$0x00 # master,
293 outb %al,$0x08 # slave
294 movb %bl,%al # ICW2 to
295 outb %al,$0x02 # master
296 movb %bh,%al # ICW2 to
297 outb %al,$0x0a # slave
298 movb $0x80,%al # ICW3 to
299 outb %al,$0x02 # master
300 movb $0x7,%al # ICW3 to
301 outb %al,$0x0a # slave
302 movb $0x1d,%al # ICW4 to
303 outb %al,$0x02 # master,
304 movb $0x9,%al # ICW4 to
305 outb %al,$0x0a # slave
306 pop %ax # Restore slave
308 pop %ax # Restore master
313 * Exception jump table.
315 intx00: push $0x0 # Int 0x0: #DE
316 jmp ex_noc # Divide error
317 push $0x1 # Int 0x1: #DB
319 push $0x3 # Int 0x3: #BP
320 jmp ex_noc # Breakpoint
321 push $0x4 # Int 0x4: #OF
322 jmp ex_noc # Overflow
323 push $0x5 # Int 0x5: #BR
324 jmp ex_noc # BOUND range exceeded
325 push $0x6 # Int 0x6: #UD
326 jmp ex_noc # Invalid opcode
327 push $0x7 # Int 0x7: #NM
328 jmp ex_noc # Device not available
329 push $0x8 # Int 0x8: #DF
330 jmp except # Double fault
331 push $0xa # Int 0xa: #TS
332 jmp except # Invalid TSS
333 push $0xb # Int 0xb: #NP
334 jmp except # Segment not present
335 push $0xc # Int 0xc: #SS
336 jmp except # Stack segment fault
337 push $0xd # Int 0xd: #GP
338 jmp except # General protection
339 push $0xe # Int 0xe: #PF
340 jmp except # Page fault
341 intx10: push $0x10 # Int 0x10: #MF
342 jmp ex_noc # Floating-point error
344 * Save a zero error code.
346 ex_noc: pushl (%esp,1) # Duplicate int no
347 movb $0x0,0x4(%esp,1) # Fake error code
351 except: cld # String ops inc
359 cmpw $SEL_SCODE,0x44(%esp,1) # Supervisor mode?
362 jmp except.2 # Join common code
363 except.1: pushl 0x50(%esp,1) # Set SS
364 except.2: pushl 0x50(%esp,1) # Set ESP
365 push $SEL_SDATA # Set up
369 movl %esp,%ebx # Stack frame
370 movl $dmpfmt,%esi # Dump format string
371 movl $MEM_BUF,%edi # Buffer
374 wait.1: inb $0x60,%al
379 wait.2: inb $0x60,%al
399 call putstr # display
400 leal 0x18(%esp,1),%esp # Discard frame
404 cmpb $0x3,(%esp,1) # Breakpoint?
406 cmpb $0x1,(%esp,1) # Debug?
408 testl $PSL_T,0x10(%esp,1) # Trap flag set?
410 except.2a: jmp exit # Exit
411 except.3: leal 0x8(%esp,1),%esp # Discard err, int no
412 iret # From interrupt
415 * Reboot the machine by setting the reboot flag and exiting
417 reboot: orb $0x1,btx_hdr+0x7 # Set the reboot flag
418 jmp exit # Terminate BTX and reboot
421 * Protected Mode Hardware interrupt jump table.
423 intx20: push $0x8 # Int 0x20: IRQ0
424 jmp int_hw # V86 int 0x8
425 push $0x9 # Int 0x21: IRQ1
426 jmp int_hw # V86 int 0x9
427 push $0xa # Int 0x22: IRQ2
428 jmp int_hw # V86 int 0xa
429 push $0xb # Int 0x23: IRQ3
430 jmp int_hw # V86 int 0xb
431 push $0xc # Int 0x24: IRQ4
432 jmp int_hw # V86 int 0xc
433 push $0xd # Int 0x25: IRQ5
434 jmp int_hw # V86 int 0xd
435 push $0xe # Int 0x26: IRQ6
436 jmp int_hw # V86 int 0xe
437 push $0xf # Int 0x27: IRQ7
438 jmp int_hw # V86 int 0xf
439 push $0x10 # Int 0x28: IRQ8
440 jmp int_hw # V86 int 0x10
441 push $0x11 # Int 0x29: IRQ9
442 jmp int_hw # V86 int 0x11
443 push $0x12 # Int 0x2a: IRQ10
444 jmp int_hw # V86 int 0x12
445 push $0x13 # Int 0x2b: IRQ11
446 jmp int_hw # V86 int 0x13
447 push $0x14 # Int 0x2c: IRQ12
448 jmp int_hw # V86 int 0x14
449 push $0x15 # Int 0x2d: IRQ13
450 jmp int_hw # V86 int 0x15
451 push $0x16 # Int 0x2e: IRQ14
452 jmp int_hw # V86 int 0x16
453 push $0x17 # Int 0x2f: IRQ15
454 jmp int_hw # V86 int 0x17
457 * Invoke real mode interrupt/function call from user mode with arguments.
459 intx31: pushl $-1 # Dummy int no for btx_v86
461 * Invoke real mode interrupt/function call from protected mode.
463 * We place a trampoline on the user stack that will return to rret_tramp
464 * which will reenter protected mode and then finally return to the user
467 * Kernel frame %esi points to: Real mode stack frame at MEM_ESPR:
469 * -0x00 user %ss -0x04 kernel %esp (with full frame)
470 * -0x04 user %esp -0x08 btx_v86 pointer
471 * -0x08 user %eflags -0x0c flags (only used if interrupt)
472 * -0x0c user %cs -0x10 real mode CS:IP return trampoline
473 * -0x10 user %eip -0x12 real mode flags
474 * -0x14 int no -0x16 real mode CS:IP (target)
487 * -0x48 zero %eax (hardware int only)
488 * -0x4c zero %ecx (hardware int only)
489 * -0x50 zero %edx (hardware int only)
490 * -0x54 zero %ebx (hardware int only)
491 * -0x58 zero %esp (hardware int only)
492 * -0x5c zero %ebp (hardware int only)
493 * -0x60 zero %esi (hardware int only)
494 * -0x64 zero %edi (hardware int only)
495 * -0x68 zero %gs (hardware int only)
496 * -0x6c zero %fs (hardware int only)
497 * -0x70 zero %ds (hardware int only)
498 * -0x74 zero %es (hardware int only)
500 int_hw: cld # String ops inc
506 push $SEL_SDATA # Set up
510 leal 0x44(%esp,1),%esi # Base of frame
511 movl %esp,MEM_ESPR-0x04 # Save kernel stack pointer
512 movl -0x14(%esi),%eax # Get Int no
513 cmpl $-1,%eax # Hardware interrupt?
516 * v86 calls save the btx_v86 pointer on the real mode stack and read
517 * the address and flags from the btx_v86 structure. For interrupt
518 * handler invocations (VM86 INTx requests), disable interrupts,
519 * tracing, and alignment checking while the handler runs.
521 movl $MEM_USR,%ebx # User base
522 movl %ebx,%edx # address
523 addl -0x4(%esi),%ebx # User ESP
524 movl (%ebx),%ebp # btx_v86 pointer
525 addl %ebp,%edx # Flatten btx_v86 ptr
526 movl %edx,MEM_ESPR-0x08 # Save btx_v86 ptr
527 movl V86_ADDR(%edx),%eax # Get int no/address
528 movl V86_CTL(%edx),%edx # Get control flags
529 movl -0x08(%esi),%ebx # Save user flags in %ebx
530 testl $V86F_ADDR,%edx # Segment:offset?
532 andl $~(PSL_I|PSL_T|PSL_AC),%ebx # Disable interrupts, tracing,
533 # and alignment checking for
535 jmp intusr.3 # Skip hardware interrupt
537 * Hardware interrupts store a NULL btx_v86 pointer and use the
538 * address (interrupt number) from the stack with empty flags. Also,
539 * push a dummy frame of zeros onto the stack for all the general
540 * purpose and segment registers and clear %eflags. This gives the
541 * hardware interrupt handler a clean slate.
543 intusr.1: xorl %edx,%edx # Control flags
544 movl %edx,MEM_ESPR-0x08 # NULL btx_v86 ptr
545 movl $12,%ecx # Frame is 12 dwords
546 intusr.2: pushl $0x0 # Fill frame
547 loop intusr.2 # with zeros
548 movl $PSL_RESERVED_DEFAULT,%ebx # Set clean %eflags
550 * Look up real mode IDT entry for hardware interrupts and VM86 INTx
553 intusr.3: shll $0x2,%eax # Scale
554 movl (%eax),%eax # Load int vector
555 jmp intusr.5 # Skip CALLF test
557 * Panic if V86F_CALLF isn't set with V86F_ADDR.
559 intusr.4: testl $V86F_CALLF,%edx # Far call?
561 movl %edx,0x30(%esp,1) # Place VM86 flags in int no
562 movl $badvm86,%esi # Display bad
563 call putstr # VM86 call
568 popal # Restore gp regs
571 * %eax now holds the segment:offset of the function.
572 * %ebx now holds the %eflags to pass to real mode.
573 * %edx now holds the V86F_* flags.
575 intusr.5: movw %bx,MEM_ESPR-0x12 # Pass user flags to real mode
578 * If this is a v86 call, copy the seg regs out of the btx_v86 structure.
580 movl MEM_ESPR-0x08,%ecx # Get btx_v86 ptr
581 jecxz intusr.6 # Skip for hardware ints
582 leal -0x44(%esi),%edi # %edi => kernel stack seg regs
584 leal V86_ES(%ecx),%esi # %esi => btx_v86 seg regs
585 movl $4,%ecx # Copy seg regs
587 movsl # to kernel stack
589 intusr.6: movl -0x08(%esi),%ebx # Copy user flags to real
590 movl %ebx,MEM_ESPR-0x0c # mode return trampoline
591 movl $rret_tramp,%ebx # Set return trampoline
592 movl %ebx,MEM_ESPR-0x10 # CS:IP
593 movl %eax,MEM_ESPR-0x16 # Real mode target CS:IP
594 ljmpw $SEL_RCODE,$intusr.7 # Change to 16-bit segment
596 intusr.7: movl %cr0,%eax # Leave
598 movl %eax,%cr0 # mode
600 intusr.8: xorw %ax,%ax # Reset %ds
603 lidt ivtdesc # Set IVT
608 popal # Restore gp regs
609 movw $MEM_ESPR-0x16,%sp # Switch to real mode stack
610 iret # Call target routine
612 * For the return to real mode we setup a stack frame like this on the real
613 * mode stack. Note that callf calls won't pop off the flags, but we just
614 * ignore that by repositioning %sp to be just above the btx_v86 pointer
615 * so it is aligned. The stack is relative to MEM_ESPR.
633 rret_tramp: movw $MEM_ESPR-0x08,%sp # Reset stack pointer
634 pushal # Save gp regs
639 pushfl # Save %eflags
640 cli # Disable interrupts
642 xorw %ax,%ax # Reset seg
644 movw %ax,%es # (%ss is already 0)
645 lidt idtdesc # Set IDT
646 lgdt gdtdesc # Set GDT
647 mov %cr0,%eax # Switch to protected
650 ljmp $SEL_SCODE,$rret_tramp.1 # To 32-bit code
652 rret_tramp.1: xorl %ecx,%ecx # Zero
653 movb $SEL_SDATA,%cl # Setup
654 movw %cx,%ss # 32-bit
657 movl MEM_ESPR-0x04,%esp # Switch to kernel stack
658 leal 0x44(%esp,1),%esi # Base of frame
659 andb $~0x2,tss_desc+0x5 # Clear TSS busy
660 movb $SEL_TSS,%cl # Set task
663 * Now we are back in protected mode. The kernel stack frame set up
664 * before entering real mode is still intact. For hardware interrupts,
665 * leave the frame unchanged.
667 cmpl $0,MEM_ESPR-0x08 # Leave saved regs unchanged
668 jz rret_tramp.3 # for hardware ints
670 * For V86 calls, copy the registers off of the real mode stack onto
671 * the kernel stack as we want their updated values. Also, initialize
672 * the segment registers on the kernel stack.
674 * Note that the %esp in the kernel stack after this is garbage, but popa
675 * ignores it, so we don't have to fix it up.
677 leal -0x18(%esi),%edi # Kernel stack GP regs
679 movl $MEM_ESPR-0x0c,%esi # Real mode stack GP regs
680 movl $8,%ecx # Copy GP regs from
681 rep # real mode stack
682 movsl # to kernel stack
683 movl $SEL_UDATA,%eax # Selector for data seg regs
684 movl $4,%ecx # Initialize %ds,
688 * For V86 calls, copy the saved seg regs on the real mode stack back
689 * over to the btx_v86 structure. Also, conditionally update the
690 * saved eflags on the kernel stack based on the flags from the user.
692 movl MEM_ESPR-0x08,%ecx # Get btx_v86 ptr
693 leal V86_GS(%ecx),%edi # %edi => btx_v86 seg regs
694 leal MEM_ESPR-0x2c,%esi # %esi => real mode seg regs
695 xchgl %ecx,%edx # Save btx_v86 ptr
696 movl $4,%ecx # Copy seg regs
697 rep # from real mode stack
700 movl V86_CTL(%edx),%edx # Read V86 control flags
701 testl $V86F_FLAGS,%edx # User wants flags?
703 movl MEM_ESPR-0x3c,%eax # Read real mode flags
704 movw %ax,-0x08(%esi) # Update user flags (low 16)
706 * Return to the user task
708 rret_tramp.3: popl %es # Restore
712 popal # Restore gp regs
713 addl $4,%esp # Discard int no
714 iret # Return to user mode
719 intx30: cmpl $SYS_EXEC,%eax # Exec system call?
729 movl $MEM_USR,%eax # User base address
730 addl 0xc(%esp,1),%eax # Change to user
731 leal 0x4(%eax),%esp # stack
734 intx30.1: orb $0x1,%ss:btx_hdr+0x7 # Flag reboot
737 * Dump structure [EBX] to [EDI], using format string [ESI].
739 dump.0: stosb # Save char
740 dump: lodsb # Load char
741 testb %al,%al # End of string?
743 testb $0x80,%al # Control?
745 movb %al,%ch # Save control
746 movb $'=',%al # Append
751 addl %ebx,%esi # pointer
752 testb $DMP_X16,%ch # Dump word?
756 dump.1: testb $DMP_X32,%ch # Dump long?
760 dump.2: testb $DMP_MEM,%ch # Dump memory?
763 testl $PSL_VM,0x50(%ebx) # V86 mode?
765 verr 0x4(%esi) # Readable selector?
767 ldsl (%esi),%esi # Load pointer
768 jmp dump.4 # Join common code
769 dump.3: lodsl # Set offset
770 xchgl %eax,%edx # Save
772 shll $0x4,%eax # * 0x10
773 addl %edx,%eax # + offset
774 xchgl %eax,%esi # Set pointer
775 dump.4: movb $2,%dl # Num lines
776 dump.4a: movb $0x10,%cl # Bytes to dump
777 dump.5: lodsb # Get byte and
779 decb %cl # Keep count
781 movb $'-',%al # Separator
782 cmpb $0x8,%cl # Half way?
784 movb $' ',%al # Use space
785 dump.6: stosb # Save separator
786 jmp dump.5 # Continue
787 dump.6a: decb %dl # Keep count
789 movb $0xa,%al # Line feed
791 movb $7,%cl # Leading
792 movb $' ',%al # spaces
793 dump.6b: stosb # Dump
796 jmp dump.4a # Next line
797 dump.7: popl %ds # Restore
798 dump.8: popl %esi # Restore
799 movb $0xa,%al # Line feed
800 testb $DMP_EOL,%ch # End of line?
802 movb $' ',%al # Use spaces
804 dump.9: jmp dump.0 # Continue
805 dump.10: stosb # Terminate string
808 * Convert EAX, AX, or AL to hex, saving the result to [EDI].
810 hex32: pushl %eax # Save
811 shrl $0x10,%eax # Do upper
814 hex16: call hex16.1 # Do upper 8
815 hex16.1: xchgb %ah,%al # Save/restore
816 hex8: pushl %eax # Save
817 shrb $0x4,%al # Do upper
820 hex8.1: andb $0xf,%al # Get lower 4
821 cmpb $0xa,%al # Convert
822 sbbb $0x69,%al # to hex
824 orb $0x20,%al # To lower case
828 * Output zero-terminated string [ESI] to the console.
830 putstr.0: call putchr # Output char
831 putstr: lodsb # Load char
832 testb %al,%al # End of string?
836 .set SIO_PRT,SIOPRT # Base port
837 .set SIO_FMT,SIOFMT # 8N1
838 .set SIO_DIV,(115200/SIOSPD) # 115200 / SPD
841 * void sio_init(void)
843 sio_init: movw $SIO_PRT+0x3,%dx # Data format reg
844 movb $SIO_FMT|0x80,%al # Set format
845 outb %al,(%dx) # and DLAB
847 subb $0x3,%dl # Divisor latch reg
848 movw $SIO_DIV,%ax # Set
851 movb $SIO_FMT,%al # Clear
852 outb %al,(%dx) # DLAB
853 incl %edx # Modem control reg
854 movb $0x3,%al # Set RTS,
856 incl %edx # Line status reg
859 * void sio_flush(void)
861 sio_flush.0: call sio_getc.1 # Get character
862 sio_flush: call sio_ischar # Check for character
863 jnz sio_flush.0 # Till none
867 * void sio_putc(int c)
869 sio_putc: movw $SIO_PRT+0x5,%dx # Line status reg
870 xor %ecx,%ecx # Timeout
871 movb $0x40,%ch # counter
872 sio_putc.1: inb (%dx),%al # Transmitter
873 testb $0x20,%al # buffer empty?
874 loopz sio_putc.1 # No
875 jz sio_putc.2 # If timeout
876 movb 0x4(%esp,1),%al # Get character
877 subb $0x5,%dl # Transmitter hold reg
878 outb %al,(%dx) # Write character
879 sio_putc.2: ret $0x4 # To caller
884 sio_getc: call sio_ischar # Character available?
886 sio_getc.1: subb $0x5,%dl # Receiver buffer reg
887 inb (%dx),%al # Read character
891 * int sio_ischar(void)
893 sio_ischar: movw $SIO_PRT+0x5,%dx # Line status register
894 xorl %eax,%eax # Zero
895 inb (%dx),%al # Received data
896 andb $0x1,%al # ready?
900 * Output character AL to the serial console.
903 cmpb $10, %al # is it a newline?
904 jne putchr.1 # no?, then leave
905 push $13 # output a carriage
906 call sio_putc # return first
907 movb $10, %al # restore %al
908 putchr.1: pushl %eax # Push the character
910 call sio_putc # Output the character
915 * Output character AL to the console.
918 xorl %ecx,%ecx # Zero for loops
919 movb $SCR_MAT,%ah # Mode/attribute
920 movl $BDA_POS,%ebx # BDA pointer
921 movw (%ebx),%dx # Cursor position
923 putchr.1: cmpb $0xa,%al # New line?
926 movb %al,(%edi,%ecx,1) # Write char
928 movb %ah,(%edi,%ecx,1) # Write attr
931 putchr.2: movw %dx,%ax
937 putchr.3: cmpw $SCR_ROW*SCR_COL*2,%dx
939 leal 2*SCR_COL(%edi),%esi # New top line
940 movw $(SCR_ROW-1)*SCR_COL/2,%cx # Words to move
943 movb $0x20,%al # Space
945 movb $SCR_COL,%cl # Columns to clear
948 movw $(SCR_ROW-1)*SCR_COL*2,%dx
949 putchr.4: movw %dx,(%ebx) # Update position
956 * Real Mode Hardware interrupt jump table.
958 intr20: push $0x8 # Int 0x20: IRQ0
959 jmp int_hwr # V86 int 0x8
960 push $0x9 # Int 0x21: IRQ1
961 jmp int_hwr # V86 int 0x9
962 push $0xa # Int 0x22: IRQ2
963 jmp int_hwr # V86 int 0xa
964 push $0xb # Int 0x23: IRQ3
965 jmp int_hwr # V86 int 0xb
966 push $0xc # Int 0x24: IRQ4
967 jmp int_hwr # V86 int 0xc
968 push $0xd # Int 0x25: IRQ5
969 jmp int_hwr # V86 int 0xd
970 push $0xe # Int 0x26: IRQ6
971 jmp int_hwr # V86 int 0xe
972 push $0xf # Int 0x27: IRQ7
973 jmp int_hwr # V86 int 0xf
974 push $0x10 # Int 0x28: IRQ8
975 jmp int_hwr # V86 int 0x10
976 push $0x11 # Int 0x29: IRQ9
977 jmp int_hwr # V86 int 0x11
978 push $0x12 # Int 0x2a: IRQ10
979 jmp int_hwr # V86 int 0x12
980 push $0x13 # Int 0x2b: IRQ11
981 jmp int_hwr # V86 int 0x13
982 push $0x14 # Int 0x2c: IRQ12
983 jmp int_hwr # V86 int 0x14
984 push $0x15 # Int 0x2d: IRQ13
985 jmp int_hwr # V86 int 0x15
986 push $0x16 # Int 0x2e: IRQ14
987 jmp int_hwr # V86 int 0x16
988 push $0x17 # Int 0x2f: IRQ15
989 jmp int_hwr # V86 int 0x17
991 * Reflect hardware interrupts in real mode.
993 int_hwr: push %ax # Save
996 mov %sp,%bp # Address stack frame
997 xchg %bx,6(%bp) # Swap BX, int no
998 xor %ax,%ax # Set %ds:%bx to
999 shl $2,%bx # point to
1000 mov %ax,%ds # IDT entry
1001 mov (%bx),%ax # Load IP
1002 mov 2(%bx),%bx # Load CS
1003 xchg %ax,4(%bp) # Swap saved %ax,%bx with
1004 xchg %bx,6(%bp) # CS:IP of handler
1007 lret # Jump to handler
1011 * Global descriptor table.
1013 gdt: .word 0x0,0x0,0x0,0x0 # Null entry
1014 .word 0xffff,0x0,0x9a00,0xcf # SEL_SCODE
1015 .word 0xffff,0x0,0x9200,0xcf # SEL_SDATA
1016 .word 0xffff,0x0,0x9a00,0x0 # SEL_RCODE
1017 .word 0xffff,0x0,0x9200,0x0 # SEL_RDATA
1018 .word 0xffff,MEM_USR,0xfa00,0xcf# SEL_UCODE
1019 .word 0xffff,MEM_USR,0xf200,0xcf# SEL_UDATA
1020 tss_desc: .word _TSSLM,MEM_TSS,0x8900,0x0 # SEL_TSS
1023 * Pseudo-descriptors.
1025 gdtdesc: .word gdt.1-gdt-1,gdt,0x0 # GDT
1026 idtdesc: .word _IDTLM,MEM_IDT,0x0 # IDT
1027 ivtdesc: .word 0x400-0x0-1,0x0,0x0 # IVT
1029 * IDT construction control string.
1031 idtctl: .byte 0x10, 0x8e # Int 0x0-0xf
1032 .word 0x7dfb,intx00 # (exceptions)
1033 .byte 0x10, 0x8e # Int 0x10
1034 .word 0x1, intx10 # (exception)
1035 .byte 0x10, 0x8e # Int 0x20-0x2f
1036 .word 0xffff,intx20 # (hardware)
1037 .byte 0x1, 0xee # int 0x30
1038 .word 0x1, intx30 # (system call)
1039 .byte 0x2, 0xee # Int 0x31-0x32
1040 .word 0x1, intx31 # (V86, null)
1041 .byte 0x0 # End of string
1043 * Dump format string.
1045 dmpfmt: .byte '\n' # "\n"
1046 .ascii "int" # "int="
1047 .byte 0x80|DMP_X32, 0x40 # "00000000 "
1048 .ascii "err" # "err="
1049 .byte 0x80|DMP_X32, 0x44 # "00000000 "
1050 .ascii "efl" # "efl="
1051 .byte 0x80|DMP_X32, 0x50 # "00000000 "
1052 .ascii "eip" # "eip="
1053 .byte 0x80|DMP_X32|DMP_EOL,0x48 # "00000000\n"
1054 .ascii "eax" # "eax="
1055 .byte 0x80|DMP_X32, 0x34 # "00000000 "
1056 .ascii "ebx" # "ebx="
1057 .byte 0x80|DMP_X32, 0x28 # "00000000 "
1058 .ascii "ecx" # "ecx="
1059 .byte 0x80|DMP_X32, 0x30 # "00000000 "
1060 .ascii "edx" # "edx="
1061 .byte 0x80|DMP_X32|DMP_EOL,0x2c # "00000000\n"
1062 .ascii "esi" # "esi="
1063 .byte 0x80|DMP_X32, 0x1c # "00000000 "
1064 .ascii "edi" # "edi="
1065 .byte 0x80|DMP_X32, 0x18 # "00000000 "
1066 .ascii "ebp" # "ebp="
1067 .byte 0x80|DMP_X32, 0x20 # "00000000 "
1068 .ascii "esp" # "esp="
1069 .byte 0x80|DMP_X32|DMP_EOL,0x0 # "00000000\n"
1071 .byte 0x80|DMP_X16, 0x4c # "0000 "
1073 .byte 0x80|DMP_X16, 0xc # "0000 "
1075 .byte 0x80|DMP_X16, 0x8 # "0000 "
1078 .byte 0x80|DMP_X16, 0x10 # "0000 "
1080 .byte 0x80|DMP_X16, 0x14 # "0000 "
1082 .byte 0x80|DMP_X16|DMP_EOL,0x4 # "0000\n"
1083 .ascii "cs:eip" # "cs:eip="
1084 .byte 0x80|DMP_MEM|DMP_EOL,0x48 # "00 00 ... 00 00\n"
1085 .ascii "ss:esp" # "ss:esp="
1086 .byte 0x80|DMP_MEM|DMP_EOL,0x0 # "00 00 ... 00 00\n"
1087 .asciz "BTX halted\n" # End
1089 * Bad VM86 call panic
1091 badvm86: .asciz "Invalid VM86 Request\n"
1094 * End of BTX memory.