[IA64] unwind.c uses wrong unat from switch_stack

unwind.c can read the wrong unat bits from switch_stack.
sw->caller_unat is the value of ar.unat when the task was blocked.
sw->ar_unat is the value of ar.unat after doing st8.spill for r4-7.
IOW, ar_unat is caller_unat with 4 bits changed.

unw_access_gr() uses sw->ar_unat for r4-7 (correct), but it also uses
sw->ar_unat for other scratch registers (incorrect).  sw->ar_unat
should only be used for r4-7, everything else should use
sw->caller_unat, unless modified by unwind info.  Using sw->ar_unat
risks picking up the 4 bits that were overwritten when r4-7 were saved.

Also this line is wrong
	unw.sw_off[unw.preg_index[UNW_REG_PFS]] = SW(AR_UNAT);
and should be
	unw.sw_off[unw.preg_index[UNW_REG_PFS]] = SW(AR_PFS);
Signed-off-by: Keith Owens <kaos@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/kernel/unwind.c

@@ -362,7 +362,7 @@ unw_access_gr (struct unw_frame_info *info, int regnum, unsigned long *val, char
 			if (info->pri_unat_loc)
 				nat_addr = info->pri_unat_loc;
 			else
-				nat_addr = &info->sw->ar_unat;
+				nat_addr = &info->sw->caller_unat;
 			nat_mask = (1UL << ((long) addr & 0x1f8)/8);
 		}
 	} else {
@@ -524,7 +524,7 @@ unw_access_ar (struct unw_frame_info *info, int regnum, unsigned long *val, int
 	      case UNW_AR_UNAT:
 		addr = info->unat_loc;
 		if (!addr)
-			addr = &info->sw->ar_unat;
+			addr = &info->sw->caller_unat;
 		break;
 
 	      case UNW_AR_LC:
@@ -1775,7 +1775,7 @@ run_script (struct unw_script *script, struct unw_frame_info *state)
 
 		      case UNW_INSN_SETNAT_MEMSTK:
 			if (!state->pri_unat_loc)
-				state->pri_unat_loc = &state->sw->ar_unat;
+				state->pri_unat_loc = &state->sw->caller_unat;
 			/* register off. is a multiple of 8, so the least 3 bits (type) are 0 */
 			s[dst+1] = ((unsigned long) state->pri_unat_loc - s[dst]) | UNW_NAT_MEMSTK;
 			break;
@@ -2243,11 +2243,11 @@ unw_init (void)
 	if (8*sizeof(unw_hash_index_t) < UNW_LOG_HASH_SIZE)
 		unw_hash_index_t_is_too_narrow();
 
-	unw.sw_off[unw.preg_index[UNW_REG_PRI_UNAT_GR]] = SW(AR_UNAT);
+	unw.sw_off[unw.preg_index[UNW_REG_PRI_UNAT_GR]] = SW(CALLER_UNAT);
 	unw.sw_off[unw.preg_index[UNW_REG_BSPSTORE]] = SW(AR_BSPSTORE);
-	unw.sw_off[unw.preg_index[UNW_REG_PFS]] = SW(AR_UNAT);
+	unw.sw_off[unw.preg_index[UNW_REG_PFS]] = SW(AR_PFS);
 	unw.sw_off[unw.preg_index[UNW_REG_RP]] = SW(B0);
-	unw.sw_off[unw.preg_index[UNW_REG_UNAT]] = SW(AR_UNAT);
+	unw.sw_off[unw.preg_index[UNW_REG_UNAT]] = SW(CALLER_UNAT);
 	unw.sw_off[unw.preg_index[UNW_REG_PR]] = SW(PR);
 	unw.sw_off[unw.preg_index[UNW_REG_LC]] = SW(AR_LC);
 	unw.sw_off[unw.preg_index[UNW_REG_FPSR]] = SW(AR_FPSR);