powerpc/booke64: Critical and machine check exception support

Add special state saving for critical and machine check exceptions.

Most of this code could be used to handle debug exceptions taken from
kernel space, but actually doing so is outside the scope of this patch.

The various critical and machine check exceptions now point to their
real handlers, rather than hanging the kernel.
Signed-off-by: Scott Wood <scottwood@freescale.com>

arch/powerpc/include/asm/paca.h

@@ -116,8 +116,11 @@ struct paca_struct {
 	/* Shared by all threads of a core -- points to tcd of first thread */
 	struct tlb_core_data *tcd_ptr;
 
-	/* We can have up to 3 levels of reentrancy in the TLB miss handler */
-	u64 extlb[3][EX_TLB_SIZE / sizeof(u64)];
+	/*
+	 * We can have up to 3 levels of reentrancy in the TLB miss handler,
+	 * in each of four exception levels (normal, crit, mcheck, debug).
+	 */
+	u64 extlb[12][EX_TLB_SIZE / sizeof(u64)];
 	u64 exmc[8];		/* used for machine checks */
 	u64 excrit[8];		/* used for crit interrupts */
 	u64 exdbg[8];		/* used for debug interrupts */

arch/powerpc/mm/tlb_nohash.c

@@ -144,6 +144,15 @@ int mmu_vmemmap_psize;		/* Page size used for the virtual mem map */
 int book3e_htw_mode;		/* HW tablewalk?  Value is PPC_HTW_* */
 unsigned long linear_map_top;	/* Top of linear mapping */
 
+
+/*
+ * Number of bytes to add to SPRN_SPRG_TLB_EXFRAME on crit/mcheck/debug
+ * exceptions.  This is used for bolted and e6500 TLB miss handlers which
+ * do not modify this SPRG in the TLB miss code; for other TLB miss handlers,
+ * this is set to zero.
+ */
+int extlb_level_exc;
+
 #endif /* CONFIG_PPC64 */
 
 #ifdef CONFIG_PPC_FSL_BOOK3E
@@ -559,6 +568,7 @@ static void setup_mmu_htw(void)
 		break;
 #ifdef CONFIG_PPC_FSL_BOOK3E
 	case PPC_HTW_E6500:
+		extlb_level_exc = EX_TLB_SIZE;
 		patch_exception(0x1c0, exc_data_tlb_miss_e6500_book3e);
 		patch_exception(0x1e0, exc_instruction_tlb_miss_e6500_book3e);
 		break;
@@ -652,6 +662,7 @@ static void __early_init_mmu(int boot_cpu)
 		memblock_enforce_memory_limit(linear_map_top);
 
 		if (book3e_htw_mode == PPC_HTW_NONE) {
+			extlb_level_exc = EX_TLB_SIZE;
 			patch_exception(0x1c0, exc_data_tlb_miss_bolted_book3e);
 			patch_exception(0x1e0,
 				exc_instruction_tlb_miss_bolted_book3e);