[ARM] 3748/3: Correct error check in vfp_raise_exceptions

Patch from Daniel Jacobowitz

The recent fix to hide VFP_NAN_FLAG broke the check in vfp_raise_exceptions;
it would attempt to deliver an exception mask of 0xfffffeff instead of reporting
a serious error condition using printk.  Define a safe constant to use for
an invalid exception maskm, and use it at both ends.
Signed-off-by: NDaniel Jacobowitz <dan@codesourcery.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/vfp/vfp.h

@@ -353,3 +353,11 @@ u32 vfp_estimate_sqrt_significand(u32 exponent, u32 significand);
  * A special flag to tell the normalisation code not to normalise.
  */
 #define VFP_NAN_FLAG	0x100
+
+/*
+ * A bit pattern used to indicate the initial (unset) value of the
+ * exception mask, in case nothing handles an instruction.  This
+ * doesn't include the NAN flag, which get masked out before
+ * we check for an error.
+ */
+#define VFP_EXCEPTION_ERROR	((u32)-1 & ~VFP_NAN_FLAG)

arch/arm/vfp/vfpmodule.c

@@ -131,7 +131,7 @@ static void vfp_raise_exceptions(u32 exceptions, u32 inst, u32 fpscr, struct pt_
 
 	pr_debug("VFP: raising exceptions %08x\n", exceptions);
 
-	if (exceptions == (u32)-1) {
+	if (exceptions == VFP_EXCEPTION_ERROR) {
 		vfp_panic("unhandled bounce");
 		vfp_raise_sigfpe(0, regs);
 		return;
@@ -170,7 +170,7 @@ static void vfp_raise_exceptions(u32 exceptions, u32 inst, u32 fpscr, struct pt_
  */
 static u32 vfp_emulate_instruction(u32 inst, u32 fpscr, struct pt_regs *regs)
 {
-	u32 exceptions = (u32)-1;
+	u32 exceptions = VFP_EXCEPTION_ERROR;
 
 	pr_debug("VFP: emulate: INST=0x%08x SCR=0x%08x\n", inst, fpscr);