411 lines
9.6 KiB
ArmAsm
411 lines
9.6 KiB
ArmAsm
#
|
|
! $Source$
|
|
! $State$
|
|
! $Revision$
|
|
|
|
! Declare segments (the order is important).
|
|
|
|
.sect .text
|
|
.sect .rom
|
|
.sect .data
|
|
.sect .bss
|
|
|
|
.sect .text
|
|
.use16
|
|
exe_header:
|
|
.data2 0x5a4d ! magic number
|
|
.data2 exe_last_page ! number of bytes in last loadable page
|
|
.data2 exe_text_pages ! size of .exe, in pages
|
|
.data2 0 ! number of relocation entries
|
|
.data2 0 ! start of loadable area, in 16-byte paragraphs
|
|
.data2 exe_ram_paras ! required RAM size, in 16-byte paragraphs
|
|
.data2 exe_ram_paras ! maximum RAM siz, in 16-byte paragraphs
|
|
.data2 0 ! initial SS, relative to program
|
|
.data2 stack ! initial SP
|
|
.data2 0 ! checksum (ignored)
|
|
.data2 exe_start ! initial IP
|
|
.data2 0 ! initial CS, relative to program
|
|
.data2 0 ! offset of relocation table
|
|
.data2 0 ! overlay number
|
|
|
|
exe_start:
|
|
! On entry, DS=ES=PSP. Make DS=CS, so we're running in tiny mode.
|
|
|
|
push cs
|
|
pop ds
|
|
mov (rseg), ds
|
|
mov (pspseg), es
|
|
|
|
! Ensure that at least two handles are available by blindly closing some.
|
|
|
|
mov bx, 19 ! close handle
|
|
movb ah, 0x3e
|
|
int 0x21
|
|
mov bx, 18 ! close handle
|
|
movb ah, 0x3e
|
|
int 0x21
|
|
|
|
! Scan the environment to find the program name.
|
|
|
|
eseg mov es, (0x2c) ! environment pointer segment from PSP
|
|
xor di, di
|
|
xorb al, al
|
|
mov cx, 0xffff
|
|
cld
|
|
1:
|
|
repne scasb ! find end of next string
|
|
eseg cmpb (di), 0
|
|
jnz 1b
|
|
2:
|
|
add di, 3
|
|
mov si, di
|
|
repne scasb
|
|
|
|
! es:si now points at the program name, and es:di at one past the end.
|
|
|
|
mov cx, di
|
|
sub cx, si
|
|
sub sp, cx ! allocate space on stack
|
|
mov di, sp ! es:si source, ds:di dest
|
|
1:
|
|
eseg movb al, (si)
|
|
inc si
|
|
movb (di), al
|
|
inc di
|
|
cmpb al, 0
|
|
jnz 1b
|
|
|
|
! Open the file. (0x5f)
|
|
|
|
mov dx, sp
|
|
mov ax, 0x3d00
|
|
int 0x21
|
|
jc no_file
|
|
mov (fh), ax
|
|
add sp, cx ! don't need filename any more
|
|
|
|
! Get the file length (== text len).
|
|
|
|
mov bx, ax
|
|
mov ax, 0x4202
|
|
xor cx, cx ! high offset
|
|
xor dx, dx ! low offset
|
|
int 0x21 ! lseek
|
|
mov (pmemlen+0), ax
|
|
mov (pmemlen+2), dx
|
|
|
|
! Initialise DPMI.
|
|
|
|
mov ax, 0x1687
|
|
int 0x2f
|
|
or ax, ax
|
|
jnz no_dpmi
|
|
mov (pmode_switch+0), di ! write back PMODE switch routine
|
|
mov (pmode_switch+2), es
|
|
or si, si ! do we need a DPMI private area?
|
|
jz 1f
|
|
|
|
mov bx, si
|
|
movb ah, 0x48
|
|
int 0x21 ! allocate memory from DOS
|
|
mov es, ax ! data area segment -> es
|
|
1:
|
|
! Switch to protected mode.
|
|
|
|
mov ax, 1 ! 32-bit app
|
|
callf (pmode_switch)
|
|
jc bad_dpmi
|
|
|
|
! We're now in protected mode.
|
|
|
|
mov (psegcs), cs
|
|
mov (psegds), ds
|
|
|
|
! Allocate space for the code segment.
|
|
|
|
mov ax, 0x0000
|
|
mov cx, 1
|
|
int 0x31 ! allocate LDT
|
|
jc bad_dpmi
|
|
mov es, ax
|
|
mov (psegcs32), ax
|
|
|
|
mov cx, (pmemlen+0)
|
|
mov bx, (pmemlen+2)
|
|
mov ax, 0x0501
|
|
int 0x31 ! allocate linear address
|
|
jc bad_dpmi
|
|
mov (pmemhandle+0), di
|
|
mov (pmemhandle+2), si
|
|
|
|
mov dx, cx
|
|
mov cx, bx
|
|
mov bx, es
|
|
mov ax, 0x0007
|
|
int 0x31 ! set segment base address
|
|
jc bad_dpmi
|
|
|
|
mov bx, es
|
|
mov dx, (pmemlen+0)
|
|
mov cx, (pmemlen+2)
|
|
mov ax, 0x0008
|
|
int 0x31 ! set segment limit
|
|
|
|
mov cx, cs
|
|
and cx, 3
|
|
shl cx, 5
|
|
or cx, 0xc09b ! 32-bit, big, code, non-conforming, readable
|
|
mov bx, es
|
|
mov ax, 0x0009
|
|
int 0x31 ! set descriptor access rights
|
|
|
|
! Allocate the data segment (as a simple clone of the code segment). (10e)
|
|
|
|
mov ax, 0x000a
|
|
mov bx, es
|
|
int 0x31
|
|
mov fs, ax
|
|
mov (psegds32), ax
|
|
|
|
mov cx, ax
|
|
and cx, 3
|
|
shl cx, 5
|
|
or cx, 0xc093 ! 32-bit, big, data, r/w, expand-up
|
|
mov bx, fs
|
|
mov ax, 0x0009
|
|
int 0x31 ! set descriptor access rights
|
|
|
|
! Load the program.
|
|
|
|
mov bx, (fh)
|
|
mov ax, 0x4200
|
|
xor cx, cx ! high offset
|
|
mov dx, text_top ! low offset
|
|
int 0x21 ! lseek
|
|
|
|
o32 xor edi, edi ! destination 32-bit register
|
|
1:
|
|
movb ah, 0x3f
|
|
mov bx, (fh)
|
|
mov cx, TRANSFER_BUFFER_SIZE
|
|
mov dx, transfer_buffer
|
|
o32 push edi
|
|
call int21 ! read up to 32kB into transfer buffer
|
|
o32 pop edi
|
|
cmp ax, 0
|
|
je 2f
|
|
|
|
o32 movzx ecx, ax ! number of bytes read
|
|
o32 mov esi, transfer_buffer
|
|
cld
|
|
o32 rep movsb
|
|
jmp 1b
|
|
2:
|
|
|
|
! Close the file.
|
|
|
|
movb ah, 0x3e
|
|
mov bx, (fh)
|
|
int 0x21 ! close
|
|
|
|
! Jump to the new segment and enter 32-bit mode!
|
|
|
|
o32 movzx eax, (psegcs)
|
|
o32 movzx ebx, (psegds)
|
|
o32 movzx ecx, (rseg)
|
|
o32 mov edx, realloc
|
|
o32 mov esi, interruptf
|
|
o32 mov edi, transfer_buffer
|
|
push es
|
|
pop ds
|
|
push es
|
|
push 0
|
|
retf ! 19b
|
|
|
|
! Helper routine which reallocates the linear block that the 32-bit code
|
|
! is running from. This can't happen from inside the 32-bit code itself
|
|
! because it might move.
|
|
!
|
|
! On entry, ds and ss are ignored. On exit, ds is set to the 32-bit segment.
|
|
! eax: new block size
|
|
realloc:
|
|
cseg mov ds, (psegds)
|
|
cli ! atomically switch stacks
|
|
o32 mov (dpmi_ebp), esp ! yes, saving esp into the ebp field
|
|
mov (dpmi_ss), ss
|
|
mov ss, (psegds)
|
|
mov sp, dosstack
|
|
sti
|
|
pusha
|
|
|
|
o32 add eax, 1024*1024 - 1
|
|
o32 and eax, ~[1024*1024 - 1]
|
|
o32 mov (pmemlen), eax
|
|
mov cx, (pmemlen+0)
|
|
mov bx, (pmemlen+2)
|
|
mov di, (pmemhandle+0)
|
|
mov si, (pmemhandle+2)
|
|
mov ax, 0x0503
|
|
int 0x31 ! resize memory block
|
|
jc bad_dpmi
|
|
mov (pmemhandle+0), di
|
|
mov (pmemhandle+2), si
|
|
mov (pmemaddr+0), cx
|
|
mov (pmemaddr+2), bx
|
|
|
|
mov bx, (psegds32)
|
|
mov dx, (pmemlen+0)
|
|
mov cx, (pmemlen+2)
|
|
mov ax, 0x0008
|
|
int 0x31 ! set ds segment limit
|
|
jc bad_dpmi
|
|
mov dx, (pmemaddr+0)
|
|
mov cx, (pmemaddr+2)
|
|
mov ax, 0x0007
|
|
int 0x31 ! set ds linear address
|
|
jc bad_dpmi
|
|
mov bx, (psegcs32)
|
|
int 0x31 ! set cs linear address
|
|
jc bad_dpmi
|
|
|
|
popa
|
|
o32 mov eax, (pmemlen)
|
|
cli ! atomically switch stacks back
|
|
mov ss, (dpmi_ss)
|
|
o32 mov esp, (dpmi_ebp)
|
|
mov ds, (psegds32)
|
|
sti
|
|
|
|
o32 retf
|
|
|
|
bad_dpmi:
|
|
mov si, bad_dpmi_msg
|
|
jmp exit_with_error
|
|
|
|
no_file:
|
|
mov si, no_file_msg
|
|
jmp exit_with_error
|
|
|
|
no_dpmi:
|
|
mov si, no_dpmi_msg
|
|
! fall through
|
|
|
|
! Displays the message in si and exits.
|
|
! This uses a loop because from protected mode any interrupt which
|
|
! takes a pointer parameter requires special treatment.
|
|
exit_with_error:
|
|
movb dl, (si)
|
|
cmpb dl, 0
|
|
je 1f
|
|
inc si
|
|
|
|
movb ah, 2
|
|
int 0x21 ! print character
|
|
jmp exit_with_error
|
|
1:
|
|
mov ax, 0x4cff
|
|
int 0x21 ! terminate with error code al
|
|
|
|
! Simulate DOS interrupt.
|
|
int21:
|
|
o32 or ebx, 0x210000
|
|
! Simulate interrupt in the high half of ebx.
|
|
interrupt:
|
|
mov (dpmi_eax), ax
|
|
mov (dpmi_ebx), bx
|
|
mov (dpmi_ecx), cx
|
|
mov (dpmi_edx), dx
|
|
mov (dpmi_esi), si
|
|
mov (dpmi_edi), di
|
|
mov ax, (rseg)
|
|
mov (dpmi_ds), ax
|
|
mov (dpmi_ss), ax
|
|
push es
|
|
mov (dpmi_sp), dosstack ! auto stack is too small
|
|
push ds
|
|
pop es
|
|
o32 mov edi, dpmi_edi
|
|
mov ax, 0x300
|
|
o32 shr ebx, 16
|
|
int 0x31 ! simulate DOS interrupt
|
|
pop es
|
|
o32 movzx eax, (dpmi_eax)
|
|
o32 movzx ebx, (dpmi_ebx)
|
|
o32 movzx ecx, (dpmi_ecx)
|
|
o32 movzx edx, (dpmi_edx)
|
|
o32 movzx esi, (dpmi_esi)
|
|
o32 movzx edi, (dpmi_edi)
|
|
push (dpmi_flags)
|
|
popf
|
|
ret
|
|
|
|
! Far call wrapper around interrupt.
|
|
interruptf:
|
|
push ds
|
|
cseg mov ds, (psegds)
|
|
call interrupt
|
|
pop ds
|
|
o32 retf
|
|
|
|
bad_dpmi_msg:
|
|
.asciz "DPMI error during setup"
|
|
no_file_msg:
|
|
.asciz "Couldn't open .exe"
|
|
no_dpmi_msg:
|
|
.asciz "No DPMI host installed"
|
|
.align 4
|
|
text_top:
|
|
|
|
exe_text_pages = [text_top - exe_header + 511] / 512
|
|
exe_last_page = [text_top - exe_header] % 512
|
|
|
|
.sect .rom
|
|
|
|
.sect .bss
|
|
bss_start:
|
|
|
|
dpmi_edi: .space 4
|
|
dpmi_esi: .space 4
|
|
dpmi_ebp: .space 4
|
|
.space 4 ! reserved
|
|
dpmi_ebx: .space 4
|
|
dpmi_edx: .space 4
|
|
dpmi_ecx: .space 4
|
|
dpmi_eax: .space 4
|
|
dpmi_flags: .space 2
|
|
dpmi_es: .space 2
|
|
dpmi_ds: .space 2
|
|
dpmi_fs: .space 2
|
|
dpmi_gs: .space 2
|
|
dpmi_ip: .space 2
|
|
dpmi_cs: .space 2
|
|
dpmi_sp: .space 2
|
|
dpmi_ss: .space 2
|
|
|
|
pmode_switch: .space 4
|
|
rseg: .space 2 ! real mode
|
|
pspseg: .space 2 ! real mode
|
|
psegcs: .space 2 ! protected mode 16-bit code segment
|
|
psegds: .space 2 ! protected mode 16-bit data segment
|
|
psegcs32: .space 2 ! protected mode 32-bit code segment
|
|
psegds32: .space 2 ! protected mode 32-bit data segment
|
|
pmemaddr: .space 4 ! protected mode linear memory address
|
|
pmemhandle: .space 4 ! protected mode linear memory handle
|
|
pmemlen: .space 4 ! protected mode linear memory length
|
|
fh: .space 2
|
|
|
|
.space 512
|
|
stack:
|
|
.space 512
|
|
dosstack:
|
|
|
|
TRANSFER_BUFFER_SIZE = 32*1024
|
|
transfer_buffer:
|
|
.space TRANSFER_BUFFER_SIZE
|
|
|
|
bss_top:
|
|
exe_ram_paras = [bss_top - bss_start + 15] / 16
|
|
|
|
! vim: ts=4 sw=4 et ft=asm
|
|
|