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
23 .set MEM_BTX,0x1000 # Start of BTX memory
24 .set MEM_ESP0,0x1800 # Supervisor stack
25 .set MEM_BUF,0x1800 # Scratch buffer
26 .set MEM_ESPR,0x5e00 # Real mode stack
27 .set MEM_IDT,0x5e00 # IDT
28 .set MEM_TSS,0x5f98 # TSS
29 .set MEM_MAP,0x6000 # I/O bit map
30 .set MEM_TSS_END,0x7fff # End of TSS
31 .set MEM_ORG,0x9000 # BTX code
32 .set MEM_USR,0xa000 # Start of user memory
36 .set PAG_SIZ,0x1000 # Page size
37 .set PAG_CNT,0x1000 # Pages to map
41 .set PSL_RESERVED_DEFAULT,0x00000002
42 .set PSL_T,0x00000100 # Trap flag
43 .set PSL_I,0x00000200 # Interrupt enable flag
44 .set PSL_VM,0x00020000 # Virtual 8086 mode flag
45 .set PSL_AC,0x00040000 # Alignment check flag
49 .set SEL_SCODE,0x8 # Supervisor code
50 .set SEL_SDATA,0x10 # Supervisor data
51 .set SEL_RCODE,0x18 # Real mode code
52 .set SEL_RDATA,0x20 # Real mode data
53 .set SEL_UCODE,0x28|3 # User code
54 .set SEL_UDATA,0x30|3 # User data
55 .set SEL_TSS,0x38 # TSS
57 * Task state segment fields.
59 .set TSS_ESP0,0x4 # PL 0 ESP
60 .set TSS_SS0,0x8 # PL 0 SS
61 .set TSS_MAP,0x66 # I/O bit map base
65 .set SYS_EXIT,0x0 # Exit
66 .set SYS_EXEC,0x1 # Exec
68 * Fields in V86 interface structure.
70 .set V86_CTL,0x0 # Control flags
71 .set V86_ADDR,0x4 # Int number/address
72 .set V86_ES,0x8 # V86 ES
73 .set V86_DS,0xc # V86 DS
74 .set V86_FS,0x10 # V86 FS
75 .set V86_GS,0x14 # V86 GS
79 .set V86F_ADDR,0x10000 # Segment:offset address
80 .set V86F_CALLF,0x20000 # Emulate far call
81 .set V86F_FLAGS,0x40000 # Return flags
83 * Dump format control bytes.
85 .set DMP_X16,0x1 # Word
86 .set DMP_X32,0x2 # Long
87 .set DMP_MEM,0x4 # Memory
88 .set DMP_EOL,0x8 # End of line
90 * Screen defaults and assumptions.
92 .set SCR_MAT,0xe1 # Mode/attribute
93 .set SCR_COL,0x50 # Columns per row
94 .set SCR_ROW,0x19 # Rows per screen
96 * BIOS Data Area locations.
98 .set BDA_MEM,0x501 # Free memory
99 .set BDA_POS,0x53e # Cursor position
101 * Derivations, for brevity.
103 .set _ESP0H,MEM_ESP0>>0x8 # Byte 1 of ESP0
104 .set _TSSIO,MEM_MAP-MEM_TSS # TSS I/O base
105 .set _TSSLM,MEM_TSS_END-MEM_TSS # TSS limit
106 .set _IDTLM,MEM_TSS-MEM_IDT-1 # IDT limit
112 start: # Start of code
116 btx_hdr: .byte 0xeb # Machine ID
117 .byte 0xe # Header size
119 .byte 0x1 # Major version
120 .byte 0x2 # Minor version
121 .byte BTX_FLAGS # Flags
122 .word PAG_CNT-MEM_ORG>>0xc # Paging control
123 .word break-start # Text size
124 .long 0x0 # Entry address
126 * Initialization routine.
128 init: cli # Disable interrupts
129 xor %ax,%ax # Zero/segment
131 mov $MEM_ESP0,%sp # stack
132 mov %ax,%es # Address
139 mov $MEM_IDT,%di # Memory to initialize
140 mov $(MEM_ORG-MEM_IDT)/2,%cx # Words to zero
144 * Update real mode IDT for reflecting hardware interrupts.
146 mov $intr20,%bx # Address first handler
147 mov $0x10,%cx # Number of handlers
148 mov $0x20*4,%di # First real mode IDT entry
149 init.0: mov %bx,(%di) # Store IP
150 inc %di # Address next
153 add $4,%bx # Next handler
154 loop init.0 # Next IRQ
159 mov $idtctl,%si # Control string
160 init.1: lodsb # Get entry
162 xchg %ax,%cx # as word
163 jcxz init.4 # If done
165 xchg %ax,%dx # P:DPL:type
168 lodsw # Get handler offset
169 mov $SEL_SCODE,%dh # Segment selector
170 init.2: shr %bx # Handle this int?
172 mov %ax,(%di) # Set handler offset
173 mov %dh,0x2(%di) # and selector
174 mov %dl,0x5(%di) # Set P:DPL:type
175 add $0x4,%ax # Next handler
176 init.3: lea 0x8(%di),%di # Next entry
177 loop init.2 # Till set done
178 jmp init.1 # Continue
182 init.4: movb $_ESP0H,TSS_ESP0+1(%di) # Set ESP0
183 movb $SEL_SDATA,TSS_SS0(%di) # Set SS0
184 movb $_TSSIO,TSS_MAP(%di) # Set I/O bit map base
186 * Bring up the system.
188 mov $0x2820,%bx # Set protected mode
189 callw setpic # IRQ offsets
190 lidt idtdesc # Set IDT
191 lgdt gdtdesc # Set GDT
192 mov %cr0,%eax # Switch to protected
195 ljmp $SEL_SCODE,$init.8 # To 32-bit code
197 init.8: xorl %ecx,%ecx # Zero
198 movb $SEL_SDATA,%cl # To 32-bit
203 movb $SEL_TSS,%cl # Set task
205 movl $MEM_USR,%edx # User base address
206 movzwl %ss:BDA_MEM,%eax # Get free memory
209 shll $0x11,%eax # To bytes
210 subl $ARGSPACE,%eax # Less arg space
211 subl %edx,%eax # Less base
212 movb $SEL_UDATA,%cl # User data selector
215 push $0x202 # Set flags (IF set)
216 push $SEL_UCODE # Set CS
217 pushl btx_hdr+0xc # Set EIP
223 movb $0x7,%cl # Set remaining
224 init.9: push $0x0 # general
225 loop init.9 # registers
227 call sio_init # setup the serial console
229 popa # and initialize
230 popl %es # Initialize
238 exit: cli # Disable interrupts
239 movl $MEM_ESP0,%esp # Clear stack
243 movl %cr0,%eax # Get CR0
244 andl $~0x80000000,%eax # Disable
245 movl %eax,%cr0 # paging
246 xorl %ecx,%ecx # Zero
247 movl %ecx,%cr3 # Flush TLB
249 * Restore the GDT in case we caught a kernel trap.
251 lgdt %cs:gdtdesc # Set GDT
255 ljmpw $SEL_RCODE,$exit.1 # Reload CS
257 exit.1: mov $SEL_RDATA,%cl # 16-bit selector
258 mov %cx,%ss # Reload SS
260 mov %cx,%es # remaining
261 mov %cx,%fs # segment
262 mov %cx,%gs # registers
264 * To real-address mode.
267 mov %eax,%cr0 # real mode
268 ljmp $0x0,$exit.2 # Reload CS
269 exit.2: xor %ax,%ax # Real mode segment
270 mov %ax,%ss # Reload SS
271 mov %ax,%ds # Address data
272 mov $0x1008,%bx # Set real mode
273 callw setpic # IRQ offsets
274 lidt ivtdesc # Set IVT
276 * Reboot or await reset.
278 sti # Enable interrupts
279 testb $0x1,btx_hdr+0x7 # Reboot?
280 exit.3: jz exit.3 # No
284 outb %al,$0xf0 # reboot the machine
287 * Set IRQ offsets by reprogramming 8259A PICs.
289 setpic: in $0x02,%al # Save master
291 in $0x0a,%al # Save slave
293 movb $0x11,%al # ICW1 to
294 outb %al,$0x00 # master,
295 outb %al,$0x08 # slave
296 movb %bl,%al # ICW2 to
297 outb %al,$0x02 # master
298 movb %bh,%al # ICW2 to
299 outb %al,$0x0a # slave
300 movb $0x80,%al # ICW3 to
301 outb %al,$0x02 # master
302 movb $0x7,%al # ICW3 to
303 outb %al,$0x0a # slave
304 movb $0x1d,%al # ICW4 to
305 outb %al,$0x02 # master,
306 movb $0x9,%al # ICW4 to
307 outb %al,$0x0a # slave
308 pop %ax # Restore slave
310 pop %ax # Restore master
315 * Exception jump table.
317 intx00: push $0x0 # Int 0x0: #DE
318 jmp ex_noc # Divide error
319 push $0x1 # Int 0x1: #DB
321 push $0x3 # Int 0x3: #BP
322 jmp ex_noc # Breakpoint
323 push $0x4 # Int 0x4: #OF
324 jmp ex_noc # Overflow
325 push $0x5 # Int 0x5: #BR
326 jmp ex_noc # BOUND range exceeded
327 push $0x6 # Int 0x6: #UD
328 jmp ex_noc # Invalid opcode
329 push $0x7 # Int 0x7: #NM
330 jmp ex_noc # Device not available
331 push $0x8 # Int 0x8: #DF
332 jmp except # Double fault
333 push $0xa # Int 0xa: #TS
334 jmp except # Invalid TSS
335 push $0xb # Int 0xb: #NP
336 jmp except # Segment not present
337 push $0xc # Int 0xc: #SS
338 jmp except # Stack segment fault
339 push $0xd # Int 0xd: #GP
340 jmp except # General protection
341 push $0xe # Int 0xe: #PF
342 jmp except # Page fault
343 intx10: push $0x10 # Int 0x10: #MF
344 jmp ex_noc # Floating-point error
346 * Save a zero error code.
348 ex_noc: pushl (%esp,1) # Duplicate int no
349 movb $0x0,0x4(%esp,1) # Fake error code
353 except: cld # String ops inc
361 cmpw $SEL_SCODE,0x44(%esp,1) # Supervisor mode?
364 jmp except.2 # Join common code
365 except.1: pushl 0x50(%esp,1) # Set SS
366 except.2: pushl 0x50(%esp,1) # Set ESP
367 push $SEL_SDATA # Set up
371 movl %esp,%ebx # Stack frame
372 movl $dmpfmt,%esi # Dump format string
373 movl $MEM_BUF,%edi # Buffer
376 wait.1: inb $0x60,%al
381 wait.2: inb $0x60,%al
401 call putstr # display
402 leal 0x18(%esp,1),%esp # Discard frame
406 cmpb $0x3,(%esp,1) # Breakpoint?
408 cmpb $0x1,(%esp,1) # Debug?
410 testl $PSL_T,0x10(%esp,1) # Trap flag set?
412 except.2a: jmp exit # Exit
413 except.3: leal 0x8(%esp,1),%esp # Discard err, int no
414 iret # From interrupt
417 * Reboot the machine by setting the reboot flag and exiting
419 reboot: orb $0x1,btx_hdr+0x7 # Set the reboot flag
420 jmp exit # Terminate BTX and reboot
423 * Protected Mode Hardware interrupt jump table.
425 intx20: push $0x8 # Int 0x20: IRQ0
426 jmp int_hw # V86 int 0x8
427 push $0x9 # Int 0x21: IRQ1
428 jmp int_hw # V86 int 0x9
429 push $0xa # Int 0x22: IRQ2
430 jmp int_hw # V86 int 0xa
431 push $0xb # Int 0x23: IRQ3
432 jmp int_hw # V86 int 0xb
433 push $0xc # Int 0x24: IRQ4
434 jmp int_hw # V86 int 0xc
435 push $0xd # Int 0x25: IRQ5
436 jmp int_hw # V86 int 0xd
437 push $0xe # Int 0x26: IRQ6
438 jmp int_hw # V86 int 0xe
439 push $0xf # Int 0x27: IRQ7
440 jmp int_hw # V86 int 0xf
441 push $0x10 # Int 0x28: IRQ8
442 jmp int_hw # V86 int 0x10
443 push $0x11 # Int 0x29: IRQ9
444 jmp int_hw # V86 int 0x11
445 push $0x12 # Int 0x2a: IRQ10
446 jmp int_hw # V86 int 0x12
447 push $0x13 # Int 0x2b: IRQ11
448 jmp int_hw # V86 int 0x13
449 push $0x14 # Int 0x2c: IRQ12
450 jmp int_hw # V86 int 0x14
451 push $0x15 # Int 0x2d: IRQ13
452 jmp int_hw # V86 int 0x15
453 push $0x16 # Int 0x2e: IRQ14
454 jmp int_hw # V86 int 0x16
455 push $0x17 # Int 0x2f: IRQ15
456 jmp int_hw # V86 int 0x17
459 * Invoke real mode interrupt/function call from user mode with arguments.
461 intx31: pushl $-1 # Dummy int no for btx_v86
463 * Invoke real mode interrupt/function call from protected mode.
465 * We place a trampoline on the user stack that will return to rret_tramp
466 * which will reenter protected mode and then finally return to the user
469 * Kernel frame %esi points to: Real mode stack frame at MEM_ESPR:
471 * -0x00 user %ss -0x04 kernel %esp (with full frame)
472 * -0x04 user %esp -0x08 btx_v86 pointer
473 * -0x08 user %eflags -0x0c flags (only used if interrupt)
474 * -0x0c user %cs -0x10 real mode CS:IP return trampoline
475 * -0x10 user %eip -0x12 real mode flags
476 * -0x14 int no -0x16 real mode CS:IP (target)
489 * -0x48 zero %eax (hardware int only)
490 * -0x4c zero %ecx (hardware int only)
491 * -0x50 zero %edx (hardware int only)
492 * -0x54 zero %ebx (hardware int only)
493 * -0x58 zero %esp (hardware int only)
494 * -0x5c zero %ebp (hardware int only)
495 * -0x60 zero %esi (hardware int only)
496 * -0x64 zero %edi (hardware int only)
497 * -0x68 zero %gs (hardware int only)
498 * -0x6c zero %fs (hardware int only)
499 * -0x70 zero %ds (hardware int only)
500 * -0x74 zero %es (hardware int only)
502 int_hw: cld # String ops inc
508 push $SEL_SDATA # Set up
512 leal 0x44(%esp,1),%esi # Base of frame
513 movl %esp,MEM_ESPR-0x04 # Save kernel stack pointer
514 movl -0x14(%esi),%eax # Get Int no
515 cmpl $-1,%eax # Hardware interrupt?
518 * v86 calls save the btx_v86 pointer on the real mode stack and read
519 * the address and flags from the btx_v86 structure. For interrupt
520 * handler invocations (VM86 INTx requests), disable interrupts,
521 * tracing, and alignment checking while the handler runs.
523 movl $MEM_USR,%ebx # User base
524 movl %ebx,%edx # address
525 addl -0x4(%esi),%ebx # User ESP
526 movl (%ebx),%ebp # btx_v86 pointer
527 addl %ebp,%edx # Flatten btx_v86 ptr
528 movl %edx,MEM_ESPR-0x08 # Save btx_v86 ptr
529 movl V86_ADDR(%edx),%eax # Get int no/address
530 movl V86_CTL(%edx),%edx # Get control flags
531 movl -0x08(%esi),%ebx # Save user flags in %ebx
532 testl $V86F_ADDR,%edx # Segment:offset?
534 andl $~(PSL_I|PSL_T|PSL_AC),%ebx # Disable interrupts, tracing,
535 # and alignment checking for
537 jmp intusr.3 # Skip hardware interrupt
539 * Hardware interrupts store a NULL btx_v86 pointer and use the
540 * address (interrupt number) from the stack with empty flags. Also,
541 * push a dummy frame of zeros onto the stack for all the general
542 * purpose and segment registers and clear %eflags. This gives the
543 * hardware interrupt handler a clean slate.
545 intusr.1: xorl %edx,%edx # Control flags
546 movl %edx,MEM_ESPR-0x08 # NULL btx_v86 ptr
547 movl $12,%ecx # Frame is 12 dwords
548 intusr.2: pushl $0x0 # Fill frame
549 loop intusr.2 # with zeros
550 movl $PSL_RESERVED_DEFAULT,%ebx # Set clean %eflags
552 * Look up real mode IDT entry for hardware interrupts and VM86 INTx
555 intusr.3: shll $0x2,%eax # Scale
556 movl (%eax),%eax # Load int vector
557 jmp intusr.5 # Skip CALLF test
559 * Panic if V86F_CALLF isn't set with V86F_ADDR.
561 intusr.4: testl $V86F_CALLF,%edx # Far call?
563 movl %edx,0x30(%esp,1) # Place VM86 flags in int no
564 movl $badvm86,%esi # Display bad
565 call putstr # VM86 call
570 popal # Restore gp regs
573 * %eax now holds the segment:offset of the function.
574 * %ebx now holds the %eflags to pass to real mode.
575 * %edx now holds the V86F_* flags.
577 intusr.5: movw %bx,MEM_ESPR-0x12 # Pass user flags to real mode
580 * If this is a v86 call, copy the seg regs out of the btx_v86 structure.
582 movl MEM_ESPR-0x08,%ecx # Get btx_v86 ptr
583 jecxz intusr.6 # Skip for hardware ints
584 leal -0x44(%esi),%edi # %edi => kernel stack seg regs
586 leal V86_ES(%ecx),%esi # %esi => btx_v86 seg regs
587 movl $4,%ecx # Copy seg regs
589 movsl # to kernel stack
591 intusr.6: movl -0x08(%esi),%ebx # Copy user flags to real
592 movl %ebx,MEM_ESPR-0x0c # mode return trampoline
593 movl $rret_tramp,%ebx # Set return trampoline
594 movl %ebx,MEM_ESPR-0x10 # CS:IP
595 movl %eax,MEM_ESPR-0x16 # Real mode target CS:IP
596 ljmpw $SEL_RCODE,$intusr.7 # Change to 16-bit segment
598 intusr.7: movl %cr0,%eax # Leave
600 movl %eax,%cr0 # mode
602 intusr.8: xorw %ax,%ax # Reset %ds
605 lidt ivtdesc # Set IVT
610 popal # Restore gp regs
611 movw $MEM_ESPR-0x16,%sp # Switch to real mode stack
612 iret # Call target routine
614 * For the return to real mode we setup a stack frame like this on the real
615 * mode stack. Note that callf calls won't pop off the flags, but we just
616 * ignore that by repositioning %sp to be just above the btx_v86 pointer
617 * so it is aligned. The stack is relative to MEM_ESPR.
635 rret_tramp: movw $MEM_ESPR-0x08,%sp # Reset stack pointer
636 pushal # Save gp regs
641 pushfl # Save %eflags
642 cli # Disable interrupts
644 xorw %ax,%ax # Reset seg
646 movw %ax,%es # (%ss is already 0)
647 lidt idtdesc # Set IDT
648 lgdt gdtdesc # Set GDT
649 mov %cr0,%eax # Switch to protected
652 ljmp $SEL_SCODE,$rret_tramp.1 # To 32-bit code
654 rret_tramp.1: xorl %ecx,%ecx # Zero
655 movb $SEL_SDATA,%cl # Setup
656 movw %cx,%ss # 32-bit
659 movl MEM_ESPR-0x04,%esp # Switch to kernel stack
660 leal 0x44(%esp,1),%esi # Base of frame
661 andb $~0x2,tss_desc+0x5 # Clear TSS busy
662 movb $SEL_TSS,%cl # Set task
665 * Now we are back in protected mode. The kernel stack frame set up
666 * before entering real mode is still intact. For hardware interrupts,
667 * leave the frame unchanged.
669 cmpl $0,MEM_ESPR-0x08 # Leave saved regs unchanged
670 jz rret_tramp.3 # for hardware ints
672 * For V86 calls, copy the registers off of the real mode stack onto
673 * the kernel stack as we want their updated values. Also, initialize
674 * the segment registers on the kernel stack.
676 * Note that the %esp in the kernel stack after this is garbage, but popa
677 * ignores it, so we don't have to fix it up.
679 leal -0x18(%esi),%edi # Kernel stack GP regs
681 movl $MEM_ESPR-0x0c,%esi # Real mode stack GP regs
682 movl $8,%ecx # Copy GP regs from
683 rep # real mode stack
684 movsl # to kernel stack
685 movl $SEL_UDATA,%eax # Selector for data seg regs
686 movl $4,%ecx # Initialize %ds,
690 * For V86 calls, copy the saved seg regs on the real mode stack back
691 * over to the btx_v86 structure. Also, conditionally update the
692 * saved eflags on the kernel stack based on the flags from the user.
694 movl MEM_ESPR-0x08,%ecx # Get btx_v86 ptr
695 leal V86_GS(%ecx),%edi # %edi => btx_v86 seg regs
696 leal MEM_ESPR-0x2c,%esi # %esi => real mode seg regs
697 xchgl %ecx,%edx # Save btx_v86 ptr
698 movl $4,%ecx # Copy seg regs
699 rep # from real mode stack
702 movl V86_CTL(%edx),%edx # Read V86 control flags
703 testl $V86F_FLAGS,%edx # User wants flags?
705 movl MEM_ESPR-0x3c,%eax # Read real mode flags
706 movw %ax,-0x08(%esi) # Update user flags (low 16)
708 * Return to the user task
710 rret_tramp.3: popl %es # Restore
714 popal # Restore gp regs
715 addl $4,%esp # Discard int no
716 iret # Return to user mode
721 intx30: cmpl $SYS_EXEC,%eax # Exec system call?
731 movl $MEM_USR,%eax # User base address
732 addl 0xc(%esp,1),%eax # Change to user
733 leal 0x4(%eax),%esp # stack
736 intx30.1: orb $0x1,%ss:btx_hdr+0x7 # Flag reboot
739 * Dump structure [EBX] to [EDI], using format string [ESI].
741 dump.0: stosb # Save char
742 dump: lodsb # Load char
743 testb %al,%al # End of string?
745 testb $0x80,%al # Control?
747 movb %al,%ch # Save control
748 movb $'=',%al # Append
753 addl %ebx,%esi # pointer
754 testb $DMP_X16,%ch # Dump word?
758 dump.1: testb $DMP_X32,%ch # Dump long?
762 dump.2: testb $DMP_MEM,%ch # Dump memory?
765 testl $PSL_VM,0x50(%ebx) # V86 mode?
767 verr 0x4(%esi) # Readable selector?
769 ldsl (%esi),%esi # Load pointer
770 jmp dump.4 # Join common code
771 dump.3: lodsl # Set offset
772 xchgl %eax,%edx # Save
774 shll $0x4,%eax # * 0x10
775 addl %edx,%eax # + offset
776 xchgl %eax,%esi # Set pointer
777 dump.4: movb $2,%dl # Num lines
778 dump.4a: movb $0x10,%cl # Bytes to dump
779 dump.5: lodsb # Get byte and
781 decb %cl # Keep count
783 movb $'-',%al # Separator
784 cmpb $0x8,%cl # Half way?
786 movb $' ',%al # Use space
787 dump.6: stosb # Save separator
788 jmp dump.5 # Continue
789 dump.6a: decb %dl # Keep count
791 movb $0xa,%al # Line feed
793 movb $7,%cl # Leading
794 movb $' ',%al # spaces
795 dump.6b: stosb # Dump
798 jmp dump.4a # Next line
799 dump.7: popl %ds # Restore
800 dump.8: popl %esi # Restore
801 movb $0xa,%al # Line feed
802 testb $DMP_EOL,%ch # End of line?
804 movb $' ',%al # Use spaces
806 dump.9: jmp dump.0 # Continue
807 dump.10: stosb # Terminate string
810 * Convert EAX, AX, or AL to hex, saving the result to [EDI].
812 hex32: pushl %eax # Save
813 shrl $0x10,%eax # Do upper
816 hex16: call hex16.1 # Do upper 8
817 hex16.1: xchgb %ah,%al # Save/restore
818 hex8: pushl %eax # Save
819 shrb $0x4,%al # Do upper
822 hex8.1: andb $0xf,%al # Get lower 4
823 cmpb $0xa,%al # Convert
824 sbbb $0x69,%al # to hex
826 orb $0x20,%al # To lower case
830 * Output zero-terminated string [ESI] to the console.
832 putstr.0: call putchr # Output char
833 putstr: lodsb # Load char
834 testb %al,%al # End of string?
838 .set SIO_PRT,SIOPRT # Base port
839 .set SIO_FMT,SIOFMT # 8N1
840 .set SIO_DIV,(115200/SIOSPD) # 115200 / SPD
845 sio_init: movw $SIO_PRT+0x3,%dx # Data format reg
846 movb $SIO_FMT|0x80,%al # Set format
847 outb %al,(%dx) # and DLAB
849 subb $0x3,%dl # Divisor latch reg
850 movw $SIO_DIV,%ax # Set
853 movb $SIO_FMT,%al # Clear
854 outb %al,(%dx) # DLAB
855 incl %edx # Modem control reg
856 movb $0x3,%al # Set RTS,
858 incl %edx # Line status reg
859 call sio_getc.1 # Get character
862 * int sio_flush(void)
864 sio_flush: xorl %eax,%eax # Return value
865 xorl %ecx,%ecx # Timeout
866 movb $0x80,%ch # counter
867 sio_flush.1: call sio_ischar # Check for character
868 jz sio_flush.2 # Till none
869 loop sio_flush.1 # or counter is zero
870 movb $1, %al # Exhausted all tries
871 sio_flush.2: ret # To caller
874 * void sio_putc(int c)
876 sio_putc: movw $SIO_PRT+0x5,%dx # Line status reg
877 xor %ecx,%ecx # Timeout
878 movb $0x40,%ch # counter
879 sio_putc.1: inb (%dx),%al # Transmitter
880 testb $0x20,%al # buffer empty?
881 loopz sio_putc.1 # No
882 jz sio_putc.2 # If timeout
883 movb 0x4(%esp,1),%al # Get character
884 subb $0x5,%dl # Transmitter hold reg
885 outb %al,(%dx) # Write character
886 sio_putc.2: ret $0x4 # To caller
891 sio_getc: call sio_ischar # Character available?
893 sio_getc.1: subb $0x5,%dl # Receiver buffer reg
894 inb (%dx),%al # Read character
898 * int sio_ischar(void)
900 sio_ischar: movw $SIO_PRT+0x5,%dx # Line status register
901 xorl %eax,%eax # Zero
902 inb (%dx),%al # Received data
903 andb $0x1,%al # ready?
907 * Output character AL to the serial console.
910 cmpb $10, %al # is it a newline?
911 jne putchr.1 # no?, then leave
912 push $13 # output a carriage
913 call sio_putc # return first
914 movb $10, %al # restore %al
915 putchr.1: pushl %eax # Push the character
917 call sio_putc # Output the character
922 * Output character AL to the console.
925 xorl %ecx,%ecx # Zero for loops
926 movb $SCR_MAT,%ah # Mode/attribute
927 movl $BDA_POS,%ebx # BDA pointer
928 movw (%ebx),%dx # Cursor position
930 putchr.1: cmpb $0xa,%al # New line?
933 movb %al,(%edi,%ecx,1) # Write char
935 movb %ah,(%edi,%ecx,1) # Write attr
938 putchr.2: movw %dx,%ax
944 putchr.3: cmpw $SCR_ROW*SCR_COL*2,%dx
946 leal 2*SCR_COL(%edi),%esi # New top line
947 movw $(SCR_ROW-1)*SCR_COL/2,%cx # Words to move
950 movb $0x20,%al # Space
952 movb $SCR_COL,%cl # Columns to clear
955 movw $(SCR_ROW-1)*SCR_COL*2,%dx
956 putchr.4: movw %dx,(%ebx) # Update position
963 * Real Mode Hardware interrupt jump table.
965 intr20: push $0x8 # Int 0x20: IRQ0
966 jmp int_hwr # V86 int 0x8
967 push $0x9 # Int 0x21: IRQ1
968 jmp int_hwr # V86 int 0x9
969 push $0xa # Int 0x22: IRQ2
970 jmp int_hwr # V86 int 0xa
971 push $0xb # Int 0x23: IRQ3
972 jmp int_hwr # V86 int 0xb
973 push $0xc # Int 0x24: IRQ4
974 jmp int_hwr # V86 int 0xc
975 push $0xd # Int 0x25: IRQ5
976 jmp int_hwr # V86 int 0xd
977 push $0xe # Int 0x26: IRQ6
978 jmp int_hwr # V86 int 0xe
979 push $0xf # Int 0x27: IRQ7
980 jmp int_hwr # V86 int 0xf
981 push $0x10 # Int 0x28: IRQ8
982 jmp int_hwr # V86 int 0x10
983 push $0x11 # Int 0x29: IRQ9
984 jmp int_hwr # V86 int 0x11
985 push $0x12 # Int 0x2a: IRQ10
986 jmp int_hwr # V86 int 0x12
987 push $0x13 # Int 0x2b: IRQ11
988 jmp int_hwr # V86 int 0x13
989 push $0x14 # Int 0x2c: IRQ12
990 jmp int_hwr # V86 int 0x14
991 push $0x15 # Int 0x2d: IRQ13
992 jmp int_hwr # V86 int 0x15
993 push $0x16 # Int 0x2e: IRQ14
994 jmp int_hwr # V86 int 0x16
995 push $0x17 # Int 0x2f: IRQ15
996 jmp int_hwr # V86 int 0x17
998 * Reflect hardware interrupts in real mode.
1000 int_hwr: push %ax # Save
1003 mov %sp,%bp # Address stack frame
1004 xchg %bx,6(%bp) # Swap BX, int no
1005 xor %ax,%ax # Set %ds:%bx to
1006 shl $2,%bx # point to
1007 mov %ax,%ds # IDT entry
1008 mov (%bx),%ax # Load IP
1009 mov 2(%bx),%bx # Load CS
1010 xchg %ax,4(%bp) # Swap saved %ax,%bx with
1011 xchg %bx,6(%bp) # CS:IP of handler
1014 lret # Jump to handler
1018 * Global descriptor table.
1020 gdt: .word 0x0,0x0,0x0,0x0 # Null entry
1021 .word 0xffff,0x0,0x9a00,0xcf # SEL_SCODE
1022 .word 0xffff,0x0,0x9200,0xcf # SEL_SDATA
1023 .word 0xffff,0x0,0x9a00,0x0 # SEL_RCODE
1024 .word 0xffff,0x0,0x9200,0x0 # SEL_RDATA
1025 .word 0xffff,MEM_USR,0xfa00,0xcf# SEL_UCODE
1026 .word 0xffff,MEM_USR,0xf200,0xcf# SEL_UDATA
1027 tss_desc: .word _TSSLM,MEM_TSS,0x8900,0x0 # SEL_TSS
1030 * Pseudo-descriptors.
1032 gdtdesc: .word gdt.1-gdt-1,gdt,0x0 # GDT
1033 idtdesc: .word _IDTLM,MEM_IDT,0x0 # IDT
1034 ivtdesc: .word 0x400-0x0-1,0x0,0x0 # IVT
1036 * IDT construction control string.
1038 idtctl: .byte 0x10, 0x8e # Int 0x0-0xf
1039 .word 0x7dfb,intx00 # (exceptions)
1040 .byte 0x10, 0x8e # Int 0x10
1041 .word 0x1, intx10 # (exception)
1042 .byte 0x10, 0x8e # Int 0x20-0x2f
1043 .word 0xffff,intx20 # (hardware)
1044 .byte 0x1, 0xee # int 0x30
1045 .word 0x1, intx30 # (system call)
1046 .byte 0x2, 0xee # Int 0x31-0x32
1047 .word 0x1, intx31 # (V86, null)
1048 .byte 0x0 # End of string
1050 * Dump format string.
1052 dmpfmt: .byte '\n' # "\n"
1053 .ascii "int" # "int="
1054 .byte 0x80|DMP_X32, 0x40 # "00000000 "
1055 .ascii "err" # "err="
1056 .byte 0x80|DMP_X32, 0x44 # "00000000 "
1057 .ascii "efl" # "efl="
1058 .byte 0x80|DMP_X32, 0x50 # "00000000 "
1059 .ascii "eip" # "eip="
1060 .byte 0x80|DMP_X32|DMP_EOL,0x48 # "00000000\n"
1061 .ascii "eax" # "eax="
1062 .byte 0x80|DMP_X32, 0x34 # "00000000 "
1063 .ascii "ebx" # "ebx="
1064 .byte 0x80|DMP_X32, 0x28 # "00000000 "
1065 .ascii "ecx" # "ecx="
1066 .byte 0x80|DMP_X32, 0x30 # "00000000 "
1067 .ascii "edx" # "edx="
1068 .byte 0x80|DMP_X32|DMP_EOL,0x2c # "00000000\n"
1069 .ascii "esi" # "esi="
1070 .byte 0x80|DMP_X32, 0x1c # "00000000 "
1071 .ascii "edi" # "edi="
1072 .byte 0x80|DMP_X32, 0x18 # "00000000 "
1073 .ascii "ebp" # "ebp="
1074 .byte 0x80|DMP_X32, 0x20 # "00000000 "
1075 .ascii "esp" # "esp="
1076 .byte 0x80|DMP_X32|DMP_EOL,0x0 # "00000000\n"
1078 .byte 0x80|DMP_X16, 0x4c # "0000 "
1080 .byte 0x80|DMP_X16, 0xc # "0000 "
1082 .byte 0x80|DMP_X16, 0x8 # "0000 "
1085 .byte 0x80|DMP_X16, 0x10 # "0000 "
1087 .byte 0x80|DMP_X16, 0x14 # "0000 "
1089 .byte 0x80|DMP_X16|DMP_EOL,0x4 # "0000\n"
1090 .ascii "cs:eip" # "cs:eip="
1091 .byte 0x80|DMP_MEM|DMP_EOL,0x48 # "00 00 ... 00 00\n"
1092 .ascii "ss:esp" # "ss:esp="
1093 .byte 0x80|DMP_MEM|DMP_EOL,0x0 # "00 00 ... 00 00\n"
1094 .asciz "BTX halted\n" # End
1096 * Bad VM86 call panic
1098 badvm86: .asciz "Invalid VM86 Request\n"
1101 * End of BTX memory.