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114 lines
2.6 KiB
NASM
114 lines
2.6 KiB
NASM
; Copyright (C) 1994 DJ Delorie, see COPYING.DJ for details
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;
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; $Id$
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; $Log$
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; Revision 1.1 1998-03-25 11:18:42 root
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; Initial revision
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;
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; Revision 1.2 1997/11/27 16:28:13 michael
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; Change submitted by Pierre Muller.
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;
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; Revision 2.0 1994/03/14 00:47:04 dj
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; initial version
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;
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;
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;-----------------------------------------------------------------------------
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; sbrk 16-bit helper
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;
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; Transferred to 16-bit code segement to run in protected mode.
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; Will make DPMI segment altering requests and update selectors
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; as needed. Image will always need to allocate an exact
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; multiple of 16 bytes, load offset will always be zero.
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; Number of bytes to copy will always be multiple of four.
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;
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; Application must set cs_selector, ds_selector, and local_ds
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; appropriately. Application uses first word in image to find
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; API entry point. Call with FAR call.
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;
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; Call with: BX:CX = new size
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; SI:DI = old handle
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; Returns: BX:CX = new base
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; SI:DI = new handle
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; all others trashed
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.type "bin"
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;-----------------------------------------------------------------------------
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; Start of API header
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offset_of_api: ; offset of API function entry point
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.dw sbrk_16_helper
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cs_selector: ; code selector to be updated
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.dw 0
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ds_selector: ; data selector to be updated
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.dw 0
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local_ds: ; selector mapped to same as local cs
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.dw 0
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bytes_to_allocate: ; number of bytes app allocates for this image
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.dw stack
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;-----------------------------------------------------------------------------
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; Start of local data
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save_ss:
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.dw 0
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save_esp:
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.dd 0
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save_ds:
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.dw 0
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;-----------------------------------------------------------------------------
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; Start of code
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sbrk_16_helper:
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mov ax, ds ; switch to local data segment
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mov ds, cs:[local_ds]
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mov [save_ds], ax
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mov [save_ss], ss ; switch to local stack
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mov [save_esp], esp
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mov ss, [local_ds]
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mov esp, stack
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mov ax, 0x0503 ; realloc memory
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int 0x31
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jc error_return ; bx:cx = base address
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mov dx, cx
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mov cx, bx ; cx:dx = base address
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mov bx, [cs_selector]
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mov ax, 0x0007
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int 0x31 ; set cs to new base
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mov bx, [ds_selector]
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mov ax, 0x0007
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int 0x31 ; set ds to new base
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push es ; reload es
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pop es
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push fs ; reload fs
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pop fs
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push gs ; reload gs
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pop gs
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mov bx, cx
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mov cx, dx ; bx:cx = base address
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error_return:
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mov ss, [save_ss] ; return to old stack
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mov esp, [save_esp]
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mov ds, [save_ds] ; return to old data segment
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.opsize ; 32-bit far return
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retf
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;-----------------------------------------------------------------------------
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; Start of stack
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.align 4 ; so that image size is longwords
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.bss
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.align 16 ; so that alloc size is paragraphs
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.db 512 .dup 0
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stack:
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