MIPS: tlbex: Deal with re-definition of label

The microassembler used in tlbex.c does not notice if a label is redefined
resulting in relocations against such labels silently missrelocated.
The issues exists since commit add6eb04776db4189ea89f596cbcde31b899be9d
[Synthesize TLB exception handlers at runtime.] in 2.6.10 and went unnoticed
for so long because the relocations for the affected branches got computed
to do something *almost* sensible.

The issue affects R4000, R4400, QED/IDT RM5230, RM5231, RM5260, RM5261,
RM5270 and RM5271 processors.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/mm/tlbex.c

@@ -148,8 +148,8 @@ enum label_id {
 	label_leave,
 	label_vmalloc,
 	label_vmalloc_done,
-	label_tlbw_hazard,
-	label_split,
+	label_tlbw_hazard_0,
+	label_split = label_tlbw_hazard_0 + 8,
 	label_tlbl_goaround1,
 	label_tlbl_goaround2,
 	label_nopage_tlbl,
@@ -167,7 +167,7 @@ UASM_L_LA(_second_part)
 UASM_L_LA(_leave)
 UASM_L_LA(_vmalloc)
 UASM_L_LA(_vmalloc_done)
-UASM_L_LA(_tlbw_hazard)
+/* _tlbw_hazard_x is handled differently.  */
 UASM_L_LA(_split)
 UASM_L_LA(_tlbl_goaround1)
 UASM_L_LA(_tlbl_goaround2)
@@ -181,6 +181,30 @@ UASM_L_LA(_large_segbits_fault)
 UASM_L_LA(_tlb_huge_update)
 #endif
 
+static int __cpuinitdata hazard_instance;
+
+static void uasm_bgezl_hazard(u32 **p, struct uasm_reloc **r, int instance)
+{
+	switch (instance) {
+	case 0 ... 7:
+		uasm_il_bgezl(p, r, 0, label_tlbw_hazard_0 + instance);
+		return;
+	default:
+		BUG();
+	}
+}
+
+static void uasm_bgezl_label(struct uasm_label **l, u32 **p, int instance)
+{
+	switch (instance) {
+	case 0 ... 7:
+		uasm_build_label(l, *p, label_tlbw_hazard_0 + instance);
+		break;
+	default:
+		BUG();
+	}
+}
+
 /*
  * For debug purposes.
  */
@@ -478,9 +502,10 @@ static void __cpuinit build_tlb_write_entry(u32 **p, struct uasm_label **l,
 		 * This branch uses up a mtc0 hazard nop slot and saves
 		 * two nops after the tlbw instruction.
 		 */
-		uasm_il_bgezl(p, r, 0, label_tlbw_hazard);
+		uasm_bgezl_hazard(p, r, hazard_instance);
 		tlbw(p);
-		uasm_l_tlbw_hazard(l, *p);
+		uasm_bgezl_label(l, p, hazard_instance);
+		hazard_instance++;
 		uasm_i_nop(p);
 		break;
 
@@ -527,14 +552,16 @@ static void __cpuinit build_tlb_write_entry(u32 **p, struct uasm_label **l,
 		break;
 
 	case CPU_NEVADA:
+		uasm_i_nop(p); /* QED specifies 2 nops hazard */
 		uasm_i_nop(p); /* QED specifies 2 nops hazard */
 		/*
 		 * This branch uses up a mtc0 hazard nop slot and saves
 		 * a nop after the tlbw instruction.
 		 */
-		uasm_il_bgezl(p, r, 0, label_tlbw_hazard);
+		uasm_bgezl_hazard(p, r, hazard_instance);
 		tlbw(p);
-		uasm_l_tlbw_hazard(l, *p);
+		uasm_bgezl_label(l, p, hazard_instance);
+		hazard_instance++;
 		break;
 
 	case CPU_RM7000: