summaryrefslogtreecommitdiffstats
path: root/sys/boot/i386/btx
diff options
context:
space:
mode:
authorrnordier <rnordier@FreeBSD.org>1998-09-12 04:29:23 +0000
committerrnordier <rnordier@FreeBSD.org>1998-09-12 04:29:23 +0000
commitb599878e7743304172846c31c8dc0db61c3c6f51 (patch)
treea393431f47e948bbb1be6d6abf69f0460b2d3a9e /sys/boot/i386/btx
parent3c3a03dc00f20f9346832e12f10338ab967b4143 (diff)
downloadFreeBSD-src-b599878e7743304172846c31c8dc0db61c3c6f51.zip
FreeBSD-src-b599878e7743304172846c31c8dc0db61c3c6f51.tar.gz
BTX (aka the boot extender) is an i386 kernel that hosts 32-bit
bootstrap programs, and provides page-level protection, hardware interrupt reflection, a virtual-8086 mode interface to BIOS, etc.
Diffstat (limited to 'sys/boot/i386/btx')
-rw-r--r--sys/boot/i386/btx/btx/btx.S937
1 files changed, 937 insertions, 0 deletions
diff --git a/sys/boot/i386/btx/btx/btx.S b/sys/boot/i386/btx/btx/btx.S
new file mode 100644
index 0000000..2b01359
--- /dev/null
+++ b/sys/boot/i386/btx/btx/btx.S
@@ -0,0 +1,937 @@
+#
+# Copyright (c) 1998 Robert Nordier
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms are freely
+# permitted provided that the above copyright notice and this
+# paragraph and the following disclaimer are duplicated in all
+# such forms.
+#
+# This software is provided "AS IS" and without any express or
+# implied warranties, including, without limitation, the implied
+# warranties of merchantability and fitness for a particular
+# purpose.
+#
+
+# $Id:$
+
+#
+# Memory layout.
+#
+ .set MEM_BTX,0x1000 # Start of BTX memory
+ .set MEM_ESP0,0x1800 # Supervisor stack
+ .set MEM_BUF,0x1800 # Scratch buffer
+ .set MEM_ESP1,0x1e00 # Link stack
+ .set MEM_IDT,0x1e00 # IDT
+ .set MEM_TSS,0x1f98 # TSS
+ .set MEM_MAP,0x2000 # I/O bit map
+ .set MEM_DIR,0x4000 # Page directory
+ .set MEM_TBL,0x5000 # Page tables
+ .set MEM_ORG,0x9000 # BTX code
+ .set MEM_USR,0xa000 # Start of user memory
+#
+# Paging control.
+#
+ .set PAG_SIZ,0x1000 # Page size
+ .set PAG_CNT,0x1000 # Pages to map
+#
+# Segment selectors.
+#
+ .set SEL_SCODE,0x8 # Supervisor code
+ .set SEL_SDATA,0x10 # Supervisor data
+ .set SEL_RCODE,0x18 # Real mode code
+ .set SEL_RDATA,0x20 # Real mode data
+ .set SEL_UCODE,0x28|3 # User code
+ .set SEL_UDATA,0x30|3 # User data
+ .set SEL_TSS,0x38 # TSS
+#
+# Task state segment fields.
+#
+ .set TSS_ESP0,0x4 # PL 0 ESP
+ .set TSS_SS0,0x8 # PL 0 SS
+ .set TSS_ESP1,0xc # PL 1 ESP
+ .set TSS_MAP,0x66 # I/O bit map base
+#
+# V86 constants.
+#
+ .set V86_FLG,0x208eff # V86 flag mask
+ .set V86_STK,0x400 # V86 stack allowance
+#
+# Dump format control bytes.
+#
+ .set DMP_X16,0x1 # Word
+ .set DMP_X32,0x2 # Long
+ .set DMP_MEM,0x4 # Memory
+ .set DMP_EOL,0x8 # End of line
+#
+# Screen defaults and assumptions.
+#
+ .set SCR_MAT,0x7 # Mode/attribute
+ .set SCR_COL,0x50 # Columns per row
+ .set SCR_ROW,0x19 # Rows per screen
+#
+# BIOS Data Area locations.
+#
+ .set BDA_MEM,0x413 # Free memory
+ .set BDA_SCR,0x449 # Video mode
+ .set BDA_POS,0x450 # Cursor position
+#
+# Derivations, for brevity.
+#
+ .set _ESP0H,MEM_ESP0>>0x8 # Byte 1 of ESP0
+ .set _ESP1H,MEM_ESP1>>0x8 # Byte 1 of ESP1
+ .set _TSSIO,MEM_MAP-MEM_TSS # TSS I/O base
+ .set _TSSLM,MEM_DIR-MEM_TSS-1 # TSS limit
+ .set _IDTLM,MEM_TSS-MEM_IDT-1 # IDT limit
+#
+# Code segment.
+#
+ .globl start
+start: # Start of code
+#
+# BTX header.
+#
+btx_hdr: .byte 0xeb # Machine ID
+ .byte 0xe # Header size
+ .ascii "BTX" # Magic
+ .byte 0x0 # Major version
+ .byte 0x50 # Minor version
+ .byte 0x0 # Flags
+ .word PAG_CNT-MEM_ORG>>0xc # Paging control
+ .word break-start # Text size
+ .long 0x0 # Entry address
+#
+# Initialization routine.
+#
+init: cli # Disable interrupts
+ xorl %eax,%eax # Zero/segment
+ movl %ax,%ss # Set up
+ movwir(MEM_ESP0,_sp) # stack
+ movl %ax,%es # Address
+ movl %ax,%ds # data
+ pushw $0x2 # Clear
+ popfw # flags
+#
+# Initialize memory.
+#
+ movwir(MEM_IDT,_di) # Memory to initialize
+ movwir((MEM_ORG-MEM_IDT)/2,_cx) # Words to zero
+ pushl %edi # Save
+ rep # Zero-fill
+ stosl # memory
+ popl %edi # Restore
+#
+# Create IDT.
+#
+ movwir(idtctl,_si) # Control string
+init.1: lodsb # Get entry
+ cwde # count
+ xchgl %eax,%ecx # as word
+ jecxz init.4 # If done
+ lodsb # Get segment
+ xchgl %eax,%edx # P:DPL:type
+ lodsl # Get control
+ xchgl %eax,%ebx # set
+ lodsl # Get handler offset
+ movb $SEL_SCODE,%dh # Segment selector
+init.2: shrl %ebx # Handle this int?
+ jnc init.3 # No
+ movwr0(_ax,_di_) # Set handler offset
+ movbr1(_dh,0x2,_di_) # and selector
+ movbr1(_dl,0x5,_di_) # Set P:DPL:type
+ addwia(0x4) # Next handler
+init.3: leaw1r(0x8,_di_,_di) # Next entry
+ loop init.2 # Till set done
+ jmp init.1 # Continue
+#
+# Initialize TSS.
+#
+init.4: movbi1(_ESP0H,TSS_ESP0+1,_di_) # Set ESP0
+ movbi1(SEL_SDATA,TSS_SS0,_di_) # Set SS0
+ movbi1(_ESP1H,TSS_ESP1+1,_di_) # Set ESP1
+ movbi1(_TSSIO,TSS_MAP,_di_) # Set I/O bit map base
+#
+# Create page directory.
+#
+ xorw %dx,%dx # Page
+ movb $PAG_SIZ>>0x8,%dh # size
+ xorw %ax,%ax # Zero
+ movwir(MEM_DIR,_di) # Page directory
+ movb $PAG_CNT>>0xa,%cl # Entries
+ movwir(MEM_TBL|0x7,_ax) # First entry
+init.5: stosw # Write entry
+ addl %edx,%eax # To next
+ loop init.5 # Till done
+#
+# Create page tables.
+#
+ movwir(MEM_TBL,_di) # Page table
+ movb $PAG_CNT>>0x8,%ch # Entries
+ xorl %eax,%eax # Start address
+init.6: movb $0x7,%al # Set U:W:P flags
+ cmpwmr(btx_hdr+0x8,_cx) # Standard user page?
+ jb init.8 # Yes
+ cmpwir(PAG_CNT-MEM_BTX>>0xc,_cx)# BTX memory?
+ ja init.8 # No
+ je init.7 # If first page
+ andb $~0x2,%al # Clear W flag
+ cmpwir(PAG_CNT-MEM_ORG>>0xc,_cx)# BTX code?
+ je init.8 # Yes
+ cmpwir(PAG_CNT-MEM_USR>>0xc,_cx)# User memory?
+ jb init.8 # User page >= 1
+ ja init.7 # BTX page
+ tstbim(0x80,btx_hdr+0x7) # Unmap user page 0?
+ jz init.7 # No
+ andb $~0x1,%al # Clear P flag
+init.7: andb $~0x4,%al # Clear U flag
+init.8: stosw # Set entry
+ addw %dx,%ax # Next address
+ loop init.6 # Till done
+#
+# Bring up the system.
+#
+ movwir(0x2820,_bx) # Set protected mode
+ callwi(setpic) # IRQ offsets
+ lidtwm(idtdesc) # Set IDT
+ xorw %ax,%ax # Set base
+ movb $MEM_DIR>>0x8,%ah # of page
+ movl %eax,%cr3 # directory
+ lgdtwm(gdtdesc) # Set GDT
+ movl %cr0,%eax # Switch to
+ o16 # protected mode
+ orl $0x80000001,%eax # and enable
+ movl %eax,%cr0 # paging
+ jmpfwi(SEL_SCODE,init.9) # To 32-bit code
+init.9: xorl %ecx,%ecx # Zero
+ movb $SEL_SDATA,%cl # To 32-bit
+ movl %cx,%ss # stack
+#
+# Launch user task.
+#
+ movb $SEL_TSS,%cl # Set task
+ ltrl %ecx # register
+ movl $MEM_USR,%edx # User base address
+ movzwl %ss:BDA_MEM,%eax # Get free memory
+ shll $0xa,%eax # To bytes
+ subl %edx,%eax # Less base
+ movb $SEL_UDATA,%cl # User data selector
+ pushl %ecx # Set SS
+ pushl %eax # Set ESP
+ pushl $0x202 # Set flags (IF set)
+ pushl $SEL_UCODE # Set CS
+ pushl $0x0 # Set EIP
+ pushl %ecx # Set GS
+ pushl %ecx # Set FS
+ pushl %ecx # Set DS
+ pushl %ecx # Set ES
+ pushl %edx # Set EAX
+ movb $0x7,%cl # Set remaining
+init.10: pushb $0x0 # general
+ loop init.10 # registers
+ popa # and initialize
+ popl %es # Initialize
+ popl %ds # user
+ popl %fs # segment
+ popl %gs # registers
+ iret # To user mode
+#
+# Exit routine.
+#
+exit: cld # String ops inc
+ movl $MEM_ESP0,%esp # Clear stack
+#
+# Turn off paging.
+#
+ movl %cr0,%eax # Get CR0
+ andl $~0x80000000,%eax # Disable
+ movl %eax,%cr0 # paging
+ xorl %ecx,%ecx # Zero
+ movl %ecx,%cr3 # Flush TLB
+#
+# To 16 bits.
+#
+ o16 # Reload
+ jmpfwi(SEL_RCODE,exit.1) # CS
+exit.1: movb $SEL_RDATA,%cl # 16-bit selector
+ movl %cx,%ss # Reload SS
+ movl %cx,%ds # Load
+ movl %cx,%es # remaining
+ movl %cx,%fs # segment
+ movl %cx,%gs # registers
+#
+# To real-address mode.
+#
+ decl %eax # Switch to
+ movl %eax,%cr0 # real mode
+ jmpfwi(0x0,exit.2) # Reload CS
+exit.2: xorl %eax,%eax # Real mode segment
+ movl %ax,%ss # Reload SS
+ movl %ax,%ds # Address data
+ movwir(0x7008,_bx) # Set real mode
+ callwi(setpic) # IRQ offsets
+ lidtwm(ivtdesc) # Set IVT
+#
+# Prompt for reboot.
+#
+ sti # Enable interrupts
+ movwir(prompt,_si) # Display
+ callwi(puts16) # prompt
+ xorb %ah,%ah # BIOS: Get
+ int $0x16 # keypress
+ int $0x19 # BIOS: Reboot
+#
+# Set IRQ offsets by reprogramming 8259A PICs.
+#
+setpic: inb $0x21,%al # Save master
+ pushl %eax # IMR
+ inb $0xa1,%al # Save slave
+ pushl %eax # IMR
+ movb $0x11,%al # ICW1 to
+ outb %al,$0x20 # master,
+ outb %al,$0xa0 # slave
+ movb %bl,%al # ICW2 to
+ outb %al,$0x21 # master
+ movb %bh,%al # ICW2 to
+ outb %al,$0xa1 # slave
+ movb $0x4,%al # ICW3 to
+ outb %al,$0x21 # master
+ movb $0x2,%al # ICW3 to
+ outb %al,$0xa1 # slave
+ movb $0x1,%al # ICW4 to
+ outb %al,$0x21 # master,
+ outb %al,$0xa1 # slave
+ popl %eax # Restore slave
+ outb %al,$0xa1 # IMR
+ popl %eax # Restore master
+ outb %al,$0x21 # IMR
+ ret # To caller
+#
+# Display zero-terminated string [ESI] using BIOS.
+#
+puts16.0: movwir(0x7,_bx) # Page:attribute
+ movb $0xe,%ah # BIOS: Display
+ int $0x10 # char
+puts16: lodsb # Load char
+ testb %al,%al # End of string?
+ jnz puts16.0 # No
+ ret # To caller
+#
+# Initiate return from V86 mode to user mode.
+#
+inthlt: hlt # To supervisor mode
+#
+# Exception jump table.
+#
+intx00: pushb $0x0 # Int 0x0: #DE
+ jmp ex_noc # Divide error
+ pushb $0x1 # Int 0x1: #DB
+ jmp ex_noc # Debug
+ pushb $0x3 # Int 0x3: #BP
+ jmp ex_noc # Breakpoint
+ pushb $0x4 # Int 0x4: #OF
+ jmp ex_noc # Overflow
+ pushb $0x5 # Int 0x5: #BR
+ jmp ex_noc # BOUND range exceeded
+ pushb $0x6 # Int 0x6: #UD
+ jmp ex_noc # Invalid opcode
+ pushb $0x7 # Int 0x7: #NM
+ jmp ex_noc # Device not available
+ pushb $0x8 # Int 0x8: #DF
+ jmp except # Double fault
+ pushb $0xa # Int 0xa: #TS
+ jmp except # Invalid TSS
+ pushb $0xb # Int 0xb: #NP
+ jmp except # Segment not present
+ pushb $0xc # Int 0xc: #SS
+ jmp except # Stack segment fault
+ pushb $0xd # Int 0xd: #GP
+ jmp ex_v86 # General protection
+ pushb $0xe # Int 0xe: #PF
+ jmp except # Page fault
+intx10: pushb $0x10 # Int 0x10: #MF
+ jmp ex_noc # Floating-point error
+#
+#
+#
+ex_v86: testb $0x2,0x12(%esp,1) # V86 mode?
+ jz except # No
+ jmp v86mon # To monitor
+#
+# Save a zero error code.
+#
+ex_noc: pushl (%esp,1) # Duplicate int no
+ movb $0x0,0x4(%esp,1) # Fake error code
+#
+# Handle exception.
+#
+except: cld # String ops inc
+ pushl %ds # Save
+ pushl %es # most
+ pusha # registers
+ movb $0x6,%al # Push loop count
+ testb $0x2,0x3a(%esp,1) # V86 mode?
+ jnz except.1 # Yes
+ pushl %gs # Set GS
+ pushl %fs # Set FS
+ pushl %ds # Set DS
+ pushl %es # Set ES
+ movb $0x2,%al # Push loop count
+ cmpw $SEL_SCODE,0x44(%esp,1) # Supervisor mode?
+ jne except.1 # No
+ pushl %ss # Set SS
+ leal 0x50(%esp,1),%eax # Set
+ pushl %eax # ESP
+ jmp except.2 # Join common code
+except.1: pushl 0x50(%esp,1) # Set GS, FS, DS, ES
+ decb %al # (if V86 mode), and
+ jne except.1 # SS, ESP
+except.2: pushl $SEL_SDATA # Set up
+ popl %ds # to
+ pushl %ds # address
+ popl %es # data
+ movl %esp,%ebx # Stack frame
+ movl $dmpfmt,%esi # Dump format string
+ movl $MEM_BUF,%edi # Buffer
+ pushl %edi # Dump to
+ call dump # buffer
+ popl %esi # and
+ call putstr # display
+ leal 0x18(%esp,1),%esp # Discard frame
+ popa # Restore
+ popl %es # registers
+ popl %ds # saved
+ cmpb $0x3,(%esp,1) # Breakpoint?
+ je except.3 # Yes
+ jmp exit # Exit
+except.3: leal 0x8(%esp,1),%esp # Discard err, int no
+ iret # From interrupt
+#
+# Return to user mode from V86 mode.
+#
+intrtn: cld # String ops inc
+ pushl %ds # Address
+ popl %es # data
+ leal 0x3c(%ebp),%edx # V86 Segment registers
+ movl MEM_TSS+TSS_ESP1,%esi # Link stack pointer
+ lodsl # INT_V86 args pointer
+ movl %esi,%ebx # Saved exception frame
+ testl %eax,%eax # INT_V86 args?
+ jz intrtn.2 # No
+ movl $MEM_USR,%edi # User base
+ movl 0x1c(%esi),%ebx # User ESP
+ movl %eax,(%edi,%ebx,1) # Restore to user stack
+ leal 0x8(%edi,%eax,1),%edi # Arg segment registers
+ testb $0x4,-0x6(%edi) # Return flags?
+ jz intrtn.1 # No
+ movl 0x30(%ebp),%eax # Get V86 flags
+ movw %ax,0x18(%esi) # Set user flags
+intrtn.1: leal 0x10(%esi),%ebx # Saved exception frame
+ xchgl %edx,%esi # Segment registers
+ movb $0x4,%cl # Update seg regs
+ rep # in INT_V86
+ movsl # args
+intrtn.2: movl %edx,%esi # Segment registers
+ leal 0x28(%ebp),%edi # Set up seg
+ movb $0x4,%cl # regs for
+ rep # later
+ movsl # pop
+ movl %ebx,%esi # Restore exception
+ movb $0x5,%cl # frame to
+ rep # supervisor
+ movsl # stack
+ movl %esi,MEM_TSS+TSS_ESP1 # Link stack pointer
+ popa # Restore
+ leal 0x8(%esp,1),%esp # Discard err, int no
+ popl %es # Restore
+ popl %ds # user
+ popl %fs # segment
+ popl %gs # registers
+ iret # To user mode
+#
+# V86 monitor.
+#
+v86mon: cld # String ops inc
+ pushl $SEL_SDATA # Set up for
+ popl %ds # flat addressing
+ pusha # Save registers
+ movl %esp,%ebp # Address stack frame
+ movzwl 0x2c(%ebp),%edi # Load V86 CS
+ shll $0x4,%edi # To linear
+ movl 0x28(%ebp),%esi # Load V86 IP
+ addl %edi,%esi # Code pointer
+ xorl %ecx,%ecx # Zero
+ movb $0x2,%cl # 16-bit operands
+ xorl %eax,%eax # Zero
+v86mon.1: lodsb # Get opcode
+ cmpb $0x66,%al # Operand size prefix?
+ jne v86mon.2 # No
+ movb $0x4,%cl # 32-bit operands
+ jmp v86mon.1 # Continue
+v86mon.2: cmpb $0xf4,%al # HLT?
+ jne v86mon.3 # No
+ cmpl $inthlt+0x1,%esi # Is inthlt?
+ jne v86mon.4 # No
+ jmp intrtn # Return to user mode
+v86mon.3: cmpb $0xfa,%al # CLI?
+ je v86cli # Yes
+ cmpb $0xfb,%al # STI?
+ je v86sti # Yes
+ movzwl 0x38(%ebp),%ebx # Load V86 SS
+ shll $0x4,%ebx # To offset
+ pushl %ebx # Save
+ addl 0x34(%ebp),%ebx # Add V86 SP
+ movl 0x30(%ebp),%edx # Load V86 flags
+ cmpb $0x9c,%al # PUSHF/PUSHFD?
+ je v86pushf # Yes
+ cmpb $0x9d,%al # POPF/POPFD?
+ je v86popf # Yes
+ cmpb $0xcd,%al # INT imm8?
+ je v86intn # Yes
+ cmpb $0xcf,%al # IRET/IRETD?
+ je v86iret # Yes
+ popl %ebx # Restore
+v86mon.4: popa # Restore
+ jmp except # Handle exception
+v86mon.5: movl %edx,0x30(%ebp) # Save V86 flags
+v86mon.6: popl %edx # V86 SS adjustment
+ subl %edx,%ebx # Save V86
+ movl %ebx,0x34(%ebp) # SP
+v86mon.7: subl %edi,%esi # From linear
+ movl %esi,0x28(%ebp) # Save V86 IP
+ popa # Restore
+ leal 0x8(%esp,1),%esp # Discard int no, error
+ iret # To V86 mode
+#
+# Emulate CLI.
+#
+v86cli: andb $~0x2,0x31(%ebp) # Clear IF
+ jmp v86mon.7 # Finish up
+#
+# Emulate STI.
+#
+v86sti: orb $0x2,0x31(%ebp) # Set IF
+ jmp v86mon.7 # Finish up
+#
+# Emulate PUSHF/PUSHFD.
+#
+v86pushf: subl %ecx,%ebx # Adjust SP
+ cmpb $0x4,%cl # 32-bit
+ je v86pushf.1 # Yes
+ o16 # 16-bit
+v86pushf.1: movl %edx,(%ebx) # Save flags
+ jmp v86mon.6 # Finish up
+#
+# Emulate IRET/IRETD.
+#
+v86iret: movzwl (%ebx),%esi # Load V86 IP
+ movzwl 0x2(%ebx),%edi # Load V86 CS
+ leal 0x4(%ebx),%ebx # Adjust SP
+ movl %edi,0x2c(%ebp) # Save V86 CS
+ xorl %edi,%edi # No ESI adjustment
+#
+# Emulate POPF/POPFD (and remainder of IRET/IRETD).
+#
+v86popf: cmpb $0x4,%cl # 32-bit?
+ je v86popf.1 # Yes
+ movl %edx,%eax # Initialize
+ o16 # 16-bit
+v86popf.1: movl (%ebx),%eax # Load flags
+ addl %ecx,%ebx # Adjust SP
+ andl $V86_FLG,%eax # Merge
+ andl $~V86_FLG,%edx # the
+ orl %eax,%edx # flags
+ jmp v86mon.5 # Finish up
+#
+# Emulate INT imm8.
+#
+v86intn: lodsb # Get int no
+ subl %edi,%esi # From
+ shrl $0x4,%edi # linear
+ movw %dx,-0x2(%ebx) # Save flags
+ movw %di,-0x4(%ebx) # Save CS
+ leal -0x6(%ebx),%ebx # Adjust SP
+ movw %si,(%ebx) # Save IP
+ shll $0x2,%eax # Scale
+ movzwl (%eax),%esi # Load IP
+ movzwl 0x2(%eax),%edi # Load CS
+ movl %edi,0x2c(%ebp) # Save CS
+ xorl %edi,%edi # No ESI adjustment
+ andb $~0x3,%dh # Clear IF and TF
+ jmp v86mon.5 # Finish up
+#
+# Hardware interrupt jump table.
+#
+intx20: pushb $0x8 # Int 0x20: IRQ0
+ jmp int_hw # V86 int 0x8
+ pushb $0x9 # Int 0x21: IRQ1
+ jmp int_hw # V86 int 0x9
+ pushb $0xa # Int 0x22: IRQ2
+ jmp int_hw # V86 int 0xa
+ pushb $0xb # Int 0x23: IRQ3
+ jmp int_hw # V86 int 0xb
+ pushb $0xc # Int 0x24: IRQ4
+ jmp int_hw # V86 int 0xc
+ pushb $0xd # Int 0x25: IRQ5
+ jmp int_hw # V86 int 0xd
+ pushb $0xe # Int 0x26: IRQ6
+ jmp int_hw # V86 int 0xe
+ pushb $0xf # Int 0x27: IRQ7
+ jmp int_hw # V86 int 0xf
+ pushb $0x70 # Int 0x28: IRQ8
+ jmp int_hw # V86 int 0x70
+ pushb $0x71 # Int 0x29: IRQ9
+ jmp int_hw # V86 int 0x71
+ pushb $0x72 # Int 0x2a: IRQ10
+ jmp int_hw # V86 int 0x72
+ pushb $0x73 # Int 0x2b: IRQ11
+ jmp int_hw # V86 int 0x73
+ pushb $0x74 # Int 0x2c: IRQ12
+ jmp int_hw # V86 int 0x74
+ pushb $0x75 # Int 0x2d: IRQ13
+ jmp int_hw # V86 int 0x75
+ pushb $0x76 # Int 0x2e: IRQ14
+ jmp int_hw # V86 int 0x76
+ pushb $0x77 # Int 0x2f: IRQ15
+ jmp int_hw # V86 int 0x77
+#
+# Reflect hardware interrupts.
+#
+int_hw: testb $0x2,0xe(%esp,1) # V86 mode?
+ jz intusr # No
+ pushl $SEL_SDATA # Address
+ popl %ds # data
+ xchgl %eax,(%esp,1) # Swap EAX, int no
+ pushl %ebp # Address
+ movl %esp,%ebp # stack frame
+ pushl %ebx # Save
+ shll $0x2,%eax # Get int
+ movl (%eax),%eax # vector
+ subl $0x6,0x14(%ebp) # Adjust V86 ESP
+ movzwl 0x18(%ebp),%ebx # V86 SS
+ shll $0x4,%ebx # * 0x10
+ addl 0x14(%ebp),%ebx # + V86 ESP
+ xchgw %ax,0x8(%ebp) # Swap V86 IP
+ rorl $0x10,%eax # Swap words
+ xchgw %ax,0xc(%ebp) # Swap V86 CS
+ roll $0x10,%eax # Swap words
+ movl %eax,(%ebx) # CS:IP for IRET
+ movl 0x10(%ebp),%eax # V86 flags
+ movw %ax,0x4(%ebx) # Flags for IRET
+ andb $~0x3,0x11(%ebp) # Clear IF, TF
+ popl %ebx # Restore
+ popl %ebp # saved
+ popl %eax # registers
+ iret # To V86 mode
+#
+# Invoke V86 interrupt from user mode, with arguments.
+#
+intx31: stc # Have btx_v86
+ pushl %eax # Missing int no
+#
+# Invoke V86 interrupt from user mode.
+#
+intusr: std # String ops dec
+ pushl %eax # Expand
+ pushl %eax # stack
+ pushl %eax # frame
+ pusha # Save
+ pushl %gs # Save
+ movl %esp,%eax # seg regs
+ pushl %fs # and
+ pushl %ds # point
+ pushl %es # to them
+ pushb $SEL_SDATA # Set up
+ popl %ds # to
+ pushl %ds # address
+ popl %es # data
+ movl $MEM_USR,%ebx # User base
+ movl %ebx,%edx # address
+ jc intusr.1 # If btx_v86
+ xorl %edx,%edx # Control flags
+ xorl %ebp,%ebp # btx_v86 pointer
+intusr.1: leal 0x50(%esp,1),%esi # Base of frame
+ pushl %esi # Save
+ addl -0x4(%esi),%ebx # User ESP
+ movl MEM_TSS+TSS_ESP1,%edi # Link stack pointer
+ leal -0x4(%edi),%edi # Adjust for push
+ xorl %ecx,%ecx # Zero
+ movb $0x5,%cl # Push exception
+ rep # frame on
+ movsl # link stack
+ xchgl %eax,%esi # Saved seg regs
+ movl 0x40(%esp,1),%eax # Get int no
+ testl %edx,%edx # Have btx_v86?
+ jz intusr.2 # No
+ movl (%ebx),%ebp # btx_v86 pointer
+ movb $0x4,%cl # Count
+ addl %ecx,%ebx # Adjust for pop
+ rep # Push saved seg regs
+ movsl # on link stack
+ addl %ebp,%edx # Flatten btx_v86 ptr
+ leal 0x14(%edx),%esi # Seg regs pointer
+ movl 0x4(%edx),%eax # Get int no/address
+ movzwl 0x2(%edx),%edx # Get control flags
+intusr.2: movl %ebp,(%edi) # Push btx_v86 and
+ movl %edi,MEM_TSS+TSS_ESP1 # save link stack ptr
+ popl %edi # Base of frame
+ xchgl %eax,%ebp # Save intno/address
+ movl 0x48(%esp,1),%eax # Get flags
+ testb $0x2,%dl # Simulate CALLF?
+ jnz intusr.3 # Yes
+ decl %ebx # Push flags
+ decl %ebx # on V86
+ movw %ax,(%ebx) # stack
+intusr.3: movb $0x4,%cl # Count
+ subl %ecx,%ebx # Push return address
+ movl $inthlt,(%ebx) # on V86 stack
+ rep # Copy seg regs to
+ movsl # exception frame
+ xchgl %eax,%ecx # Save flags
+ movl %ebx,%eax # User ESP
+ subl $V86_STK,%eax # Less bytes
+ ja intusr.4 # to
+ xorl %eax,%eax # keep
+intusr.4: shrl $0x4,%eax # Gives segment
+ stosl # Set SS
+ shll $0x4,%eax # To bytes
+ xchgl %eax,%ebx # Swap
+ subl %ebx,%eax # Gives offset
+ stosl # Set ESP
+ xchgl %eax,%ecx # Get flags
+ btsl $0x11,%eax # Set VM
+ andb $~0x3,%ah # Clear IF and TF
+ stosl # Set EFL
+ xchgl %eax,%ebp # Get int no/address
+ testb $0x1,%dl # Address?
+ jnz intusr.5 # Yes
+ shll $0x2,%eax # XXX Scale
+ movl (%eax),%eax # Load int vector
+intusr.5: movl %eax,%ecx # XXX Save
+ shrl $0x10,%eax # Gives segment
+ stosl # Set CS
+ movw %cx,%ax # XXX Restore
+ stosl # Set EIP
+ leal 0x10(%esp,1),%esp # Discard seg regs
+ popa # Restore
+ iret # To V86 mode
+#
+# System Call.
+#
+intx30: jmp exit # Just exit for now
+#
+# Dump structure [EBX] to [EDI], using format string [ESI].
+#
+dump.0: stosb # Save char
+dump: lodsb # Load char
+ testb %al,%al # End of string?
+ jz dump.10 # Yes
+ testb $0x80,%al # Control?
+ jz dump.0 # No
+ movb %al,%ch # Save control
+ movb $'=',%al # Append
+ stosb # '='
+ lodsb # Get offset
+ pushl %esi # Save
+ movsbl %al,%esi # To
+ addl %ebx,%esi # pointer
+ testb $DMP_X16,%ch # Dump word?
+ jz dump.1 # No
+ lodsw # Get and
+ call hex16 # dump it
+dump.1: testb $DMP_X32,%ch # Dump long?
+ jz dump.2 # No
+ lodsl # Get and
+ call hex32 # dump it
+dump.2: testb $DMP_MEM,%ch # Dump memory?
+ jz dump.8 # No
+ pushl %ds # Save
+ testb $0x2,0x52(%ebx) # XXX V86 mode?
+ jnz dump.3 # Yes
+ verrl 0x4(%esi) # Readable selector?
+ jnz dump.3 # No
+ ldsl (%esi),%esi # Load pointer
+ jmp dump.4 # Join common code
+dump.3: lodsl # Set offset
+ xchgl %eax,%edx # Save
+ lodsl # Get segment
+ shll $0x4,%eax # * 0x10
+ addl %edx,%eax # + offset
+ xchgl %eax,%esi # Set pointer
+dump.4: movb $0x10,%cl # Bytes to dump
+dump.5: lodsb # Get byte and
+ call hex8 # dump it
+ decb %cl # Keep count
+ jz dump.7 # If done
+ movb $'-',%al # Separator
+ cmpb $0x8,%cl # Half way?
+ je dump.6 # Yes
+ movb $' ',%al # Use space
+dump.6: stosb # Save separator
+ jmp dump.5 # Continue
+dump.7: popl %ds # Restore
+dump.8: popl %esi # Restore
+ movb $0xa,%al # Line feed
+ testb $DMP_EOL,%ch # End of line?
+ jnz dump.9 # Yes
+ movb $' ',%al # Use spaces
+ stosb # Save one
+dump.9: jmp dump.0 # Continue
+dump.10: stosb # Terminate string
+ ret # To caller
+#
+# Convert EAX, AX, or AL to hex, saving the result to [EDI].
+#
+hex32: pushl %eax # Save
+ shrl $0x10,%eax # Do upper
+ call hex16 # 16
+ popl %eax # Restore
+hex16: call hex16.1 # Do upper 8
+hex16.1: xchgb %ah,%al # Save/restore
+hex8: pushl %eax # Save
+ shrb $0x4,%al # Do upper
+ call hex8.1 # 4
+ popl %eax # Restore
+hex8.1: andb $0xf,%al # Get lower 4
+ cmpb $0xa,%al # Convert
+ sbbb $0x69,%al # to hex
+ das # digit
+ orb $0x20,%al # To lower case
+ stosb # Save char
+ ret # (Recursive)
+#
+# Output zero-terminated string [ESI] to the console.
+#
+putstr.0: call putchr # Output char
+putstr: lodsb # Load char
+ testb %al,%al # End of string?
+ jnz putstr.0 # No
+ ret # To caller
+#
+# Output character AL to the console.
+#
+putchr: pusha # Save
+ xorl %ecx,%ecx # Zero for loops
+ movb $SCR_MAT,%ah # Mode/attribute
+ movl $BDA_POS,%ebx # BDA pointer
+ movw (%ebx),%dx # Cursor position
+ movl $0xb8000,%edi # Regen buffer (color)
+ cmpb %ah,BDA_SCR-BDA_POS(%ebx) # Mono mode?
+ jne putchr.1 # No
+ xorw %di,%di # Regen buffer (mono)
+putchr.1: cmpb $0xa,%al # New line?
+ je putchr.2 # Yes
+ xchgl %eax,%ecx # Save char
+ movb $SCR_COL,%al # Columns per row
+ mulb %dh # * row position
+ addb %dl,%al # + column
+ adcb $0x0,%ah # position
+ shll %eax # * 2
+ xchgl %eax,%ecx # Swap char, offset
+ movw %ax,(%edi,%ecx,1) # Write attr:char
+ incl %edx # Bump cursor
+ cmpb $SCR_COL,%dl # Beyond row?
+ jb putchr.3 # No
+putchr.2: xorb %dl,%dl # Zero column
+ incb %dh # Bump row
+putchr.3: cmpb $SCR_ROW,%dh # Beyond screen?
+ jb putchr.4 # No
+ leal 2*SCR_COL(%edi),%esi # New top line
+ movw $(SCR_ROW-1)*SCR_COL/2,%cx # Words to move
+ rep # Scroll
+ movsl # screen
+ movb $' ',%al # Space
+ movb $SCR_COL,%cl # Columns to clear
+ rep # Clear
+ stosw # line
+ movb $SCR_ROW-1,%dh # Bottom line
+putchr.4: movw %dx,(%ebx) # Update position
+ popa # Restore
+ ret # To caller
+
+ .p2align 4
+#
+# Global descriptor table.
+#
+gdt: .word 0x0,0x0,0x0,0x0 # Null entry
+ .word 0xffff,0x0,0x9a00,0xcf # SEL_SCODE
+ .word 0xffff,0x0,0x9200,0xcf # SEL_SDATA
+ .word 0xffff,0x0,0x9a00,0x0 # SEL_RCODE
+ .word 0xffff,0x0,0x9200,0x0 # SEL_RDATA
+ .word 0xffff,MEM_USR,0xfa00,0xcf# SEL_UCODE
+ .word 0xffff,MEM_USR,0xf200,0xcf# SEL_UDATA
+ .word _TSSLM,MEM_TSS,0x8900,0x0 # SEL_TSS
+gdt.1:
+#
+# Pseudo-descriptors.
+#
+gdtdesc: .word gdt.1-gdt-1,gdt,0x0 # GDT
+idtdesc: .word _IDTLM,MEM_IDT,0x0 # IDT
+ivtdesc: .word 0x400-0x0-1,0x0,0x0 # IVT
+#
+# IDT construction control string.
+#
+idtctl: .byte 0x10, 0x8e # Int 0x0-0xf
+ .word 0x7dfb,intx00 # (exceptions)
+ .byte 0x10, 0x8e # Int 0x10
+ .word 0x1, intx10 # (exception)
+ .byte 0x10, 0x8e # Int 0x20-0x2f
+ .word 0xffff,intx20 # (hardware)
+ .byte 0x1, 0xee # int 0x30
+ .word 0x1, intx30 # (system call)
+ .byte 0x2, 0xee # Int 0x31-0x32
+ .word 0x1, intx31 # (V86, null)
+ .byte 0x0 # End of string
+#
+# Dump format string.
+#
+dmpfmt: .ascii "int" # "int="
+ .byte 0x80|DMP_X32, 0x40 # "00000000 "
+ .ascii "err" # "err="
+ .byte 0x80|DMP_X32, 0x44 # "00000000 "
+ .ascii "efl" # "efl="
+ .byte 0x80|DMP_X32, 0x50 # "00000000 "
+ .ascii "eip" # "eip="
+ .byte 0x80|DMP_X32|DMP_EOL,0x48 # "00000000\n"
+ .ascii "eax" # "eax="
+ .byte 0x80|DMP_X32, 0x34 # "00000000 "
+ .ascii "ebx" # "ebx="
+ .byte 0x80|DMP_X32, 0x28 # "00000000 "
+ .ascii "ecx" # "ecx="
+ .byte 0x80|DMP_X32, 0x30 # "00000000 "
+ .ascii "edx" # "edx="
+ .byte 0x80|DMP_X32|DMP_EOL,0x2c # "00000000\n"
+ .ascii "esi" # "esi="
+ .byte 0x80|DMP_X32, 0x1c # "00000000 "
+ .ascii "edi" # "edi="
+ .byte 0x80|DMP_X32, 0x18 # "00000000 "
+ .ascii "ebp" # "ebp="
+ .byte 0x80|DMP_X32, 0x20 # "00000000 "
+ .ascii "esp" # "esp="
+ .byte 0x80|DMP_X32|DMP_EOL,0x0 # "00000000\n"
+ .ascii "cs" # "cs="
+ .byte 0x80|DMP_X16, 0x4c # "0000 "
+ .ascii "ds" # "ds="
+ .byte 0x80|DMP_X16, 0xc # "0000 "
+ .ascii "es" # "es="
+ .byte 0x80|DMP_X16, 0x8 # "0000 "
+ .ascii " " # " "
+ .ascii "fs" # "fs="
+ .byte 0x80|DMP_X16, 0x10 # "0000 "
+ .ascii "gs" # "gs="
+ .byte 0x80|DMP_X16, 0x14 # "0000 "
+ .ascii "ss" # "ss="
+ .byte 0x80|DMP_X16|DMP_EOL,0x4 # "0000\n"
+ .ascii "cs:eip" # "cs:eip="
+ .byte 0x80|DMP_MEM|DMP_EOL,0x48 # "00 00 ... 00 00\n"
+ .ascii "ss:esp" # "ss:esp="
+ .byte 0x80|DMP_MEM|DMP_EOL,0x0 # "00 00 ... 00 00\n"
+ .byte 0x0 # End of string
+#
+# Messages.
+#
+prompt: .asciz "Press ENTER to reboot"
+#
+# Start of user memory.
+#
+ .p2align 4
+break:
OpenPOWER on IntegriCloud