[PATCH] i386: fix get_segment_eip() with vm86 segments

We need to check for vm86 mode first before looking at selector privilege
bits.

Segment limit is always base + 64k and only the low 16 bits of EIP are
significant in vm86 mode.

Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
Cc: Andi Kleen <ak@muc.de>
Cc: Zachary Amsden <zach@vmware.com>
Cc: Rohit Seth <rohitseth@google.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/mm/fault.c

@@ -77,12 +77,15 @@ static inline unsigned long get_segment_eip(struct pt_regs *regs,
 	unsigned seg = regs->xcs & 0xffff;
 	u32 seg_ar, seg_limit, base, *desc;
 
+	/* Unlikely, but must come before segment checks. */
+	if (unlikely(regs->eflags & VM_MASK)) {
+		base = seg << 4;
+		*eip_limit = base + 0xffff;
+		return base + (eip & 0xffff);
+	}
+
 	/* The standard kernel/user address space limit. */
 	*eip_limit = (seg & 3) ? USER_DS.seg : KERNEL_DS.seg;
-
-	/* Unlikely, but must come before segment checks. */
-	if (unlikely((regs->eflags & VM_MASK) != 0))
-		return eip + (seg << 4);
 
 	/* By far the most common cases. */
 	if (likely(seg == __USER_CS || seg == __KERNEL_CS))