powerpc: Add definitions used by exception handling on 64-bit Book3E

This adds various definitions and macros used by the exception and TLB
miss handling on 64-bit BookE

It also adds the definitions of the SPRGs used for various exception types
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/exception-64e.h

+/*
+ *  Definitions for use by exception code on Book3-E
+ *
+ *  Copyright (C) 2008 Ben. Herrenschmidt (benh@kernel.crashing.org), IBM Corp.
+ *
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License
+ *  as published by the Free Software Foundation; either version
+ *  2 of the License, or (at your option) any later version.
+ */
+#ifndef _ASM_POWERPC_EXCEPTION_64E_H
+#define _ASM_POWERPC_EXCEPTION_64E_H
+
+/*
+ * SPRGs usage an other considerations...
+ *
+ * Since TLB miss and other standard exceptions can be interrupted by
+ * critical exceptions which can themselves be interrupted by machine
+ * checks, and since the two later can themselves cause a TLB miss when
+ * hitting the linear mapping for the kernel stacks, we need to be a bit
+ * creative on how we use SPRGs.
+ *
+ * The base idea is that we have one SRPG reserved for critical and one
+ * for machine check interrupts. Those are used to save a GPR that can
+ * then be used to get the PACA, and store as much context as we need
+ * to save in there. That includes saving the SPRGs used by the TLB miss
+ * handler for linear mapping misses and the associated SRR0/1 due to
+ * the above re-entrancy issue.
+ *
+ * So here's the current usage pattern. It's done regardless of which
+ * SPRGs are user-readable though, thus we might have to change some of
+ * this later. In order to do that more easily, we use special constants
+ * for naming them
+ *
+ * WARNING: Some of these SPRGs are user readable. We need to do something
+ * about it as some point by making sure they can't be used to leak kernel
+ * critical data
+ */
+
+
+/* We are out of SPRGs so we save some things in the PACA. The normal
+ * exception frame is smaller than the CRIT or MC one though
+ */
+#define EX_R1		(0 * 8)
+#define EX_CR		(1 * 8)
+#define EX_R10		(2 * 8)
+#define EX_R11		(3 * 8)
+#define EX_R14		(4 * 8)
+#define EX_R15		(5 * 8)
+
+/* The TLB miss exception uses different slots */
+
+#define EX_TLB_R10	( 0 * 8)
+#define EX_TLB_R11	( 1 * 8)
+#define EX_TLB_R12	( 2 * 8)
+#define EX_TLB_R13	( 3 * 8)
+#define EX_TLB_R14	( 4 * 8)
+#define EX_TLB_R15	( 5 * 8)
+#define EX_TLB_R16	( 6 * 8)
+#define EX_TLB_CR	( 7 * 8)
+#define EX_TLB_DEAR	( 8 * 8) /* Level 0 and 2 only */
+#define EX_TLB_ESR	( 9 * 8) /* Level 0 and 2 only */
+#define EX_TLB_SRR0	(10 * 8)
+#define EX_TLB_SRR1	(11 * 8)
+#define EX_TLB_MMUCR0	(12 * 8) /* Level 0 */
+#define EX_TLB_MAS1	(12 * 8) /* Level 0 */
+#define EX_TLB_MAS2	(13 * 8) /* Level 0 */
+#ifdef CONFIG_BOOK3E_MMU_TLB_STATS
+#define EX_TLB_R8	(14 * 8)
+#define EX_TLB_R9	(15 * 8)
+#define EX_TLB_LR	(16 * 8)
+#define EX_TLB_SIZE	(17 * 8)
+#else
+#define EX_TLB_SIZE	(14 * 8)
+#endif
+
+#define	START_EXCEPTION(label)						\
+	.globl exc_##label##_book3e;					\
+exc_##label##_book3e:
+
+/* TLB miss exception prolog
+ *
+ * This prolog handles re-entrancy (up to 3 levels supported in the PACA
+ * though we currently don't test for overflow). It provides you with a
+ * re-entrancy safe working space of r10...r16 and CR with r12 being used
+ * as the exception area pointer in the PACA for that level of re-entrancy
+ * and r13 containing the PACA pointer.
+ *
+ * SRR0 and SRR1 are saved, but DEAR and ESR are not, since they don't apply
+ * as-is for instruction exceptions. It's up to the actual exception code
+ * to save them as well if required.
+ */
+#define TLB_MISS_PROLOG							    \
+	mtspr	SPRN_SPRG_TLB_SCRATCH,r12;				    \
+	mfspr	r12,SPRN_SPRG_TLB_EXFRAME;				    \
+	std	r10,EX_TLB_R10(r12);					    \
+	mfcr	r10;							    \
+	std	r11,EX_TLB_R11(r12);					    \
+	mfspr	r11,SPRN_SPRG_TLB_SCRATCH;				    \
+	std	r13,EX_TLB_R13(r12);					    \
+	mfspr	r13,SPRN_SPRG_PACA;					    \
+	std	r14,EX_TLB_R14(r12);					    \
+	addi	r14,r12,EX_TLB_SIZE;					    \
+	std	r15,EX_TLB_R15(r12);					    \
+	mfspr	r15,SPRN_SRR1;						    \
+	std	r16,EX_TLB_R16(r12);					    \
+	mfspr	r16,SPRN_SRR0;						    \
+	std	r10,EX_TLB_CR(r12);					    \
+	std	r11,EX_TLB_R12(r12);					    \
+	mtspr	SPRN_SPRG_TLB_EXFRAME,r14;				    \
+	std	r15,EX_TLB_SRR1(r12);					    \
+	std	r16,EX_TLB_SRR0(r12);					    \
+	TLB_MISS_PROLOG_STATS
+
+/* And these are the matching epilogs that restores things
+ *
+ * There are 3 epilogs:
+ *
+ * - SUCCESS       : Unwinds one level
+ * - ERROR         : restore from level 0 and reset
+ * - ERROR_SPECIAL : restore from current level and reset
+ *
+ * Normal errors use ERROR, that is, they restore the initial fault context
+ * and trigger a fault. However, there is a special case for linear mapping
+ * errors. Those should basically never happen, but if they do happen, we
+ * want the error to point out the context that did that linear mapping
+ * fault, not the initial level 0 (basically, we got a bogus PGF or something
+ * like that). For userland errors on the linear mapping, there is no
+ * difference since those are always level 0 anyway
+ */
+
+#define TLB_MISS_RESTORE(freg)						    \
+	ld	r14,EX_TLB_CR(r12);					    \
+	ld	r10,EX_TLB_R10(r12);					    \
+	ld	r15,EX_TLB_SRR0(r12);					    \
+	ld	r16,EX_TLB_SRR1(r12);					    \
+	mtspr	SPRN_SPRG_TLB_EXFRAME,freg;				    \
+	ld	r11,EX_TLB_R11(r12);					    \
+	mtcr	r14;							    \
+	ld	r13,EX_TLB_R13(r12);					    \
+	ld	r14,EX_TLB_R14(r12);					    \
+	mtspr	SPRN_SRR0,r15;						    \
+	ld	r15,EX_TLB_R15(r12);					    \
+	mtspr	SPRN_SRR1,r16;						    \
+	TLB_MISS_RESTORE_STATS						    \
+	ld	r16,EX_TLB_R16(r12);					    \
+	ld	r12,EX_TLB_R12(r12);					    \
+
+#define TLB_MISS_EPILOG_SUCCESS						    \
+	TLB_MISS_RESTORE(r12)
+
+#define TLB_MISS_EPILOG_ERROR						    \
+	addi	r12,r13,PACA_EXTLB;					    \
+	TLB_MISS_RESTORE(r12)
+
+#define TLB_MISS_EPILOG_ERROR_SPECIAL					    \
+	addi	r11,r13,PACA_EXTLB;					    \
+	TLB_MISS_RESTORE(r11)
+
+#ifdef CONFIG_BOOK3E_MMU_TLB_STATS
+#define TLB_MISS_PROLOG_STATS						    \
+	mflr	r10;							    \
+	std	r8,EX_TLB_R8(r12);					    \
+	std	r9,EX_TLB_R9(r12);					    \
+	std	r10,EX_TLB_LR(r12);
+#define TLB_MISS_RESTORE_STATS					            \
+	ld	r16,EX_TLB_LR(r12);					    \
+	ld	r9,EX_TLB_R9(r12);					    \
+	ld	r8,EX_TLB_R8(r12);					    \
+	mtlr	r16;
+#define TLB_MISS_STATS_D(name)						    \
+	addi	r9,r13,MMSTAT_DSTATS+name;				    \
+	bl	.tlb_stat_inc;
+#define TLB_MISS_STATS_I(name)						    \
+	addi	r9,r13,MMSTAT_ISTATS+name;				    \
+	bl	.tlb_stat_inc;
+#define TLB_MISS_STATS_X(name)						    \
+	ld	r8,PACA_EXTLB+EX_TLB_ESR(r13);				    \
+	cmpdi	cr2,r8,-1;						    \
+	beq	cr2,61f;						    \
+	addi	r9,r13,MMSTAT_DSTATS+name;				    \
+	b	62f;							    \
+61:	addi	r9,r13,MMSTAT_ISTATS+name;				    \
+62:	bl	.tlb_stat_inc;
+#define TLB_MISS_STATS_SAVE_INFO					    \
+	std	r14,EX_TLB_ESR(r12);	/* save ESR */			    \
+
+
+#else
+#define TLB_MISS_PROLOG_STATS
+#define TLB_MISS_RESTORE_STATS
+#define TLB_MISS_STATS_D(name)
+#define TLB_MISS_STATS_I(name)
+#define TLB_MISS_STATS_X(name)
+#define TLB_MISS_STATS_Y(name)
+#define TLB_MISS_STATS_SAVE_INFO
+#endif
+
+
+#endif /* _ASM_POWERPC_EXCEPTION_64E_H */
+

arch/powerpc/include/asm/reg.h

@@ -652,6 +652,16 @@
  *	- SPRG2 scratch for exception vectors
  *	- SPRG3 unused (user visible)
  *
+ * 64-bit embedded
+ *	- SPRG0 generic exception scratch
+ *	- SPRG2 TLB exception stack
+ *	- SPRG3 unused (user visible)
+ *	- SPRG4 unused (user visible)
+ *	- SPRG6 TLB miss scratch (user visible, sorry !)
+ *	- SPRG7 critical exception scratch
+ *	- SPRG8 machine check exception scratch
+ *	- SPRG9 debug exception scratch
+ *
  * All 32-bit:
  *	- SPRG3 current thread_info pointer
  *        (virtual on BookE, physical on others)
@@ -705,6 +715,15 @@
 #define SPRN_SPRG_SCRATCH0	SPRN_SPRG2
 #endif
 
+#ifdef CONFIG_PPC_BOOK3E_64
+#define SPRN_SPRG_MC_SCRATCH	SPRN_SPRG8
+#define SPRN_SPRG_CRIT_SCRATCH	SPRN_SPRG7
+#define SPRN_SPRG_DBG_SCRATCH	SPRN_SPRG9
+#define SPRN_SPRG_TLB_EXFRAME	SPRN_SPRG2
+#define SPRN_SPRG_TLB_SCRATCH	SPRN_SPRG6
+#define SPRN_SPRG_GEN_SCRATCH	SPRN_SPRG0
+#endif
+
 #ifdef CONFIG_PPC_BOOK3S_32
 #define SPRN_SPRG_SCRATCH0	SPRN_SPRG0
 #define SPRN_SPRG_SCRATCH1	SPRN_SPRG1