Hi!
25-Июл-2006 21:48 [EMAIL PROTECTED] (Japheth) wrote to
freedos-devel@lists.sourceforge.net:
>> QEMU has never liked CTMOUSE under FreeDOS, and possibly MS-DOS. I don't
>> know why.
J> when I modify emm386.asm, proc v86_monitor, so that the IF in real-mode is
J> cleared for all interrupts routed to v86-mode, not just the IRQs, it works
J> with CTMOUSE in qemu.
Do you wish to say, that IF doesn't cleared by FD-EMM386? This is bug.
Excerpt from "IA-32 Intel Architecture Software Developer's Manual, Volume
2: Instruction Set":
"
---------------------------------------------------------------------
INT n/INTO/INT 3 - Call to Interrupt Procedure
Opcode Instruction Description
CC INT 3 Interrupt 3 - trap to debugger
CD ib INT imm8 Interrupt vector number specified by immediate byte
CE INTO Interrupt 4 - if overflow flag is 1
Description
[...]
Operation
[...]
REAL-ADDRESS-MODE:
IF DEST * 4 + 3 outside IDT limit THEN #GP; FI;
IF stack not large enough for a 6-byte return information THEN #SS; FI;
Push(EFLAGS[15:0]);
>IF <- 0; (* Clear interrupt flag *)
TF <- 0; (* Clear trap flag *)
AC <- 0; (* Clear AC flag *)
Push(CS);
Push(IP);
(* No error codes are pushed *)
CS <- IDT(Descriptor(vector_number * 4), selector));
EIP <- IDT(Descriptor(vector_number * 4), offset)); (* 16-bit offset AND
0000FFFFH *)
END;
"
Or, may be I'm wrong?
"
INTERRUPT-FROM-VIRTUAL-8086-MODE:
(* Check segment selector and descriptor for privilege level 0 stack in
current TSS *)
[...]
tempEFLAGS <- EFLAGS;
>IF service through interrupt gate THEN IF <- 0; FI;
TF <- 0;
VM <- 0;
RF <- 0;
TempSS <- SS;
TempESP <- ESP;
SS:ESP <- TSS(SS0:ESP0); (* Change to level 0 stack segment *)
(* Following pushes are 16 bits for 16-bit gate and 32 bits for 32-bit gates *)
(* Segment selector pushes in 32-bit mode are padded to two words *)
Push(GS);
Push(FS);
[...]
"
But isn't _inside_ V86 behavior of flags shouldn't be changed (in compare
with real mode)?
J> There might be good reasons to clear IF for IRQs only, as it is done in
J> current source code. But IIRC, isn't in real-mode the IF cleared when
J> entering
J> *any* interrupt handler? It's just in protected mode that there exist 2 kind
J> of gates, "interrupt gates" and "task gates", where only the first disables
J> interrupts.
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