[patch] vm86: fix IOPL virtualisation

Stas Sergeev (stssppnn@yahoo.com)
Sun, 25 May 2003 21:33:29 +0400

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Hello.

The attached patch implements the following:
http://x86.ddj.com/articles/vme1/vme_overview.htm

---
In addition to moving the VIF to the IF on the stack image, 
PUSHF always pushes an IOPL image of 3 onto the
stack.

---


Many DOS programs, including dos4gw, are
checking if they are in a v86 mode by trying
to alter IOPL. With that patch they are not
get confused under dosemu.
Also the patch fixes what looks like a bug
with an IF flag.


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--- linux/arch/i386/kernel/vm86.c	Sun Aug  4 03:44:30 2002
+++ linux/arch/i386/kernel/vm86.c	Sat May 24 19:30:45 2003
@@ -362,6 +362,9 @@
 
 	if (VEFLAGS & VIF_MASK)
 		flags |= IF_MASK;
+	else
+		flags &= ~IF_MASK;
+	flags |= IOPL_MASK;
 	return flags | (VEFLAGS & current->thread.v86mask);
 }
 


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