1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
|
uses
crt,
go32;
var
r : trealregs;
axreg : Word;
oldint21h : tseginfo;
newint21h : tseginfo;
procedure int21h_handler; assembler;
asm
cmpw $0x3001, %ax
jne .LCallOld
movw $0x3112, %ax
iret
.LCallOld:
ljmp %cs:oldint21h
end;
procedure resume;
begin
Writeln;
Write('-- press any key to resume --'); readkey;
gotoxy(1, wherey); clreol;
end;
begin
clrscr;
Writeln('Executing real mode interrupt');
resume;
r.ah := $30; r.al := $01; realintr($21, r);
Writeln('DOS v', r.al,'.',r.ah, ' detected');
resume;
Writeln('Executing protected mode interrupt without our own',
' handler');
Writeln;
asm
movb $0x30, %ah
movb $0x01, %al
int $0x21
movw %ax, axreg
end;
Writeln('DOS v', r.al,'.',r.ah, ' detected');
resume;
Writeln('As you can see the DPMI hosts default protected mode',
'handler');
Writeln('simply redirects it to the real mode handler');
resume;
Writeln('Now exchanging the protected mode interrupt with our ',
'own handler');
resume;
newint21h.offset := @int21h_handler;
newint21h.segment := get_cs;
get_pm_interrupt($21, oldint21h);
set_pm_interrupt($21, newint21h);
Writeln('Executing real mode interrupt again');
resume;
r.ah := $30; r.al := $01; realintr($21, r);
Writeln('DOS v', r.al,'.',r.ah, ' detected');
Writeln;
Writeln('See, it didn''t change in any way.');
resume;
Writeln('Now calling protected mode interrupt');
resume;
asm
movb $0x30, %ah
movb $0x01, %al
int $0x21
movw %ax, axreg
end;
Writeln('DOS v', lo(axreg),'.',hi(axreg), ' detected');
Writeln;
Writeln('Now you can see that there''s a distinction between ',
'the two ways of calling interrupts...');
set_pm_interrupt($21, oldint21h);
end.
|
