[haiku-development] Re: Anyone seen this - Vesa delay
- From: Jan Klötzke <jan.kloetzke@xxxxxxxxxx>
- To: haiku-development@xxxxxxxxxxxxx
- Date: Tue, 8 Jul 2008 19:17:12 +0200
Jan Klötzke <jan.kloetzke@xxxxxxxxxx> wrote:
> Stephan Assmus <superstippi@xxxxxx> wrote:
> > I know that Ingo is experiencing the same behavior. On my system, I just
> > get "General System Error" when I try to change resolution (VESA also)
> > during runtime. But I think if I have a vesa kernel settings file with
> > anything different than the native resolution, my system does not boot. I
> > am not sure, but I thought for the behavior you describe, there is a bug
> > report, but I could be wrong.
> >
> > Jan, any ideas?
>
> Unfortunately not really. I suspect that there is an error in the
> instruction emulation part of the vm86 stuff which confuses the BIOS. Just
> a wild guess. I was not able yet to reproduce it on any of my systems here.
>
> What makes it really interesting and what is new to me is that you get
> a "General System Error". Would you mind to enable TRACE_VM86 in
> src/system/kernel/arch/x86/vm86.cpp and capture the output? Maybe I can
> spot something there because the traces I've got so far did not contain
> anything suspicious...
Wait a minute... I found something. The PUSHF/POPF instructions were not
emulated correctly! The attached patch should fix that. Hope that solves the
problems. At least it should be applied nonetheless.
/Jan
diff --git a/src/system/kernel/arch/x86/vm86.cpp
b/src/system/kernel/arch/x86/vm86.cpp
index dbadced..5e41a9b 100644
--- a/src/system/kernel/arch/x86/vm86.cpp
+++ b/src/system/kernel/arch/x86/vm86.cpp
@@ -44,8 +44,8 @@
#define PUSHF 0x9c
#define STI 0xfb
-#define I_FLAG (1 << 9)
-#define DIRECTION_FLAG (1 << 10)
+#define I_FLAG (1u << 9)
+#define DIRECTION_FLAG (1u << 10)
#define CSEG 0x2e
#define SSEG 0x36
@@ -442,7 +442,7 @@ emulate(struct vm86_state *state)
uint16 flags = state->regs.flags;
/* store real IF */
- flags &= I_FLAG;
+ flags &= ~I_FLAG;
flags |= (uint16)state->if_flag << 9;
pushw(&state->regs, flags);
@@ -475,10 +475,11 @@ emulate(struct vm86_state *state)
case PUSHF:
{
TRACE_NP("PUSHF");
- uint16 flags = state->regs.flags & I_FLAG;
+ uint32 flags = state->regs.flags;
/* store real IF */
- flags |= (uint16)state->if_flag << 9;
+ flags &= ~I_FLAG;
+ flags |= (uint32)state->if_flag << 9;
if (prefix.size)
pushl(&state->regs, flags);
else
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