commit Bart's patch to fix CP/M call psp:05h compatibility call along with some comments to explain the call trampoline
git-svn-id: https://svn.code.sf.net/p/freedos/svn/kernel/trunk@1372 6ac86273-5f31-0410-b378-82cca8765d1b
This commit is contained in:
Kenneth J Davis
parent
497a2337ef
commit
240bcc30e2
@ -65,14 +65,22 @@ typedef struct {
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UWORD ps_exit; /* 00 CP/M-like exit point: int 20 */
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UWORD ps_size; /* 02 segment of first byte beyond */
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/* memory allocated to program */
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BYTE ps_fill1; /* 04 single char fill */
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BYTE ps_fill1; /* 04 single char fill=0 */
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/* CP/M-like entry point */
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UBYTE ps_farcall; /* 05 far call opcode */
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/* CP/M-like entry point */
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/* offsets 5-9 are a far call to absolute address 0:000Ch
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coded so that CP/M apps can do a near call to psp:5, does a
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far call but ensures word at offset 6 is size of COM file
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e.g. FEF0h by using 1MB wrap around address 0F01D:FEF0
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(jmp code stored at 0:000C should be duplicated in HMA FFFF:00D0)
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Note: MS-DOS has value as FEEE which wraps to 0:00BEh */
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UBYTE ps_farcall; /* 05 far call opcode */
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VOID(FAR ASMCFUNC * ps_reentry) (void); /* 06 re-entry point */
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intvec ps_isv22, /* 0a terminate address */
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ps_isv23, /* 0e break address */
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ps_isv24; /* 12 critical error address */
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intvec ps_isv22, /* 0a terminate address */
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ps_isv23, /* 0e break address */
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ps_isv24; /* 12 critical error address */
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UWORD ps_parent; /* 16 parent psp segment */
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UBYTE ps_files[20]; /* 18 file table - 0xff is unused */
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UWORD ps_environ; /* 2c environment paragraph */
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106
kernel/entry.asm
106
kernel/entry.asm
@ -28,10 +28,10 @@
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; $Id$
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;
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%include "segs.inc"
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%include "segs.inc"
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%include "stacks.inc"
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segment HMA_TEXT
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segment HMA_TEXT
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extern _int21_syscall
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extern _int21_service
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extern _int2526_handler
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@ -50,7 +50,7 @@ segment HMA_TEXT
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extern _Int21AX:wrt DGROUP
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extern _DGROUP_
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extern _DGROUP_
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global reloc_call_cpm_entry
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global reloc_call_int20_handler
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@ -65,9 +65,14 @@ segment HMA_TEXT
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; VOID FAR
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; cpm_entry(iregs UserRegs)
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;
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; This one is a strange one. The call is to psp:0005h but it returns to the
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; function after the call. What we do is convert it to a normal call and
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; fudge the stack to look like an int 21h call.
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; For CP/M compatibility allow a program to invoke any DOS API function
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; between 0 and 24h by doing a near call to psp:0005h which embeds a far call
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; to absolute address 0:00C0h (int vector 30h & 31h) or FFFF:00D0 (hma).
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; Note: int 31h is also used for DPMI
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; Upon entry the stack has a near return offset (desired return address) and
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; far return seg:offset (useless return to data at offset 0ah after far call
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; in psp). We convert it to a normal call and correct the stack to appear same
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; as if invoked via an int 21h call including proper return address.
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;
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reloc_call_cpm_entry:
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; Stack is:
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@ -75,10 +80,7 @@ reloc_call_cpm_entry:
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; psp seg
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; 000ah
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;
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push bp ; trash old return address
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mov bp,sp
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xchg bp,[2+bp]
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pop bp
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add sp, 2 ; remove unneeded far return offset 0ah
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pushf ; start setting up int 21h stack
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;
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; now stack is
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@ -107,12 +109,12 @@ reloc_call_cpm_entry:
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; psp seg (alias .COM cs)
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; return offset
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;
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cmp cl,024h
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jbe cpm_error
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cmp cl,024h ; restrict calls to functions 0-24h
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ja cpm_error
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mov ah,cl ; get the call # from cl to ah
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jmp reloc_call_int21_handler ; do the system call
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cpm_error: mov al,0
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iret
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iret ; cleanup stack and return to caller
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;
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; interrupt zero divide handler:
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@ -123,20 +125,20 @@ cpm_error: mov al,0
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; int20_handler(iregs UserRegs)
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;
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print_hex: mov cl, 12
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print_hex: mov cl, 12
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hex_loop:
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mov ax, dx
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shr ax, cl
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and al, 0fh
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cmp al, 10
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sbb al, 69h
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das
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mov bx, 0070h
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mov ah, 0eh
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int 10h
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sub cl, 4
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jae hex_loop
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ret
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mov ax, dx
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shr ax, cl
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and al, 0fh
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cmp al, 10
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sbb al, 69h
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das
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mov bx, 0070h
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mov ah, 0eh
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int 10h
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sub cl, 4
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jae hex_loop
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ret
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divide_by_zero_message db 0dh,0ah,'Interrupt divide by zero, stack:',0dh,0ah,0
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@ -159,27 +161,27 @@ zero_message_loop:
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jmp short zero_message_loop
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zero_done:
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mov bp, sp
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xor si, si ; print 13 words of stack for debugging LUDIV etc.
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stack_loop:
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mov bp, sp
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xor si, si ; print 13 words of stack for debugging LUDIV etc.
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stack_loop:
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mov dx, [bp+si]
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call print_hex
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mov al, ' '
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int 10h
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inc si
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inc si
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cmp si, 13*2
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jb stack_loop
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mov al, 0dh
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int 10h
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mov al, 0ah
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int 10h
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call print_hex
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mov al, ' '
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int 10h
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inc si
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inc si
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cmp si, 13*2
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jb stack_loop
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mov al, 0dh
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int 10h
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mov al, 0ah
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int 10h
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mov ax,04c7fh ; terminate with errorlevel 127
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int 21h
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sti
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thats_it: hlt
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jmp short thats_it ; it might be command.com that nukes
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sti
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thats_it: hlt
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jmp short thats_it ; it might be command.com that nukes
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invalid_opcode_message db 0dh,0ah,'Invalid Opcode at ',0
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@ -299,7 +301,7 @@ int21_1:
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; I don't know who needs that, but ... (TE)
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;
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mov word [_user_r+2],ss
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mov word [_user_r],bp ; store and init
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mov word [_user_r],bp ; store and init
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;
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; Decide which stack to run on.
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@ -377,9 +379,9 @@ int21_exit_nodec:
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%ifdef WATCOM
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sub bp, 4 ; for fs and gs only
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%else
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sub bp, 6 ; high parts of eax, ebx or ecx, edx
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sub bp, 6 ; high parts of eax, ebx or ecx, edx
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%endif
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%endif
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%endif
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cli
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mov ss,si
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@ -387,7 +389,7 @@ int21_exit_nodec:
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int21_ret:
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Restore386Registers
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POP$ALL
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POP$ALL
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;
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; ... and return.
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@ -466,8 +468,8 @@ int2526:
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Protect386Registers
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push dx
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push cx ; save user stack
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push dx
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push cx ; save user stack
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push dx ; SS:SP -> user stack
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push cx
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@ -475,8 +477,8 @@ int2526:
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call _int2526_handler
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add sp, byte 6
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pop cx
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pop dx ; restore user stack
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pop cx
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pop dx ; restore user stack
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Restore386Registers
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