1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3  *  Definitions for use by exception code on Book3-E
4  *
5  *  Copyright (C) 2008 Ben. Herrenschmidt (benh@kernel.crashing.org), IBM Corp.
6  */
7 #ifndef _ASM_POWERPC_EXCEPTION_64E_H
8 #define _ASM_POWERPC_EXCEPTION_64E_H
9 
10 /*
11  * SPRGs usage an other considerations...
12  *
13  * Since TLB miss and other standard exceptions can be interrupted by
14  * critical exceptions which can themselves be interrupted by machine
15  * checks, and since the two later can themselves cause a TLB miss when
16  * hitting the linear mapping for the kernel stacks, we need to be a bit
17  * creative on how we use SPRGs.
18  *
19  * The base idea is that we have one SRPG reserved for critical and one
20  * for machine check interrupts. Those are used to save a GPR that can
21  * then be used to get the PACA, and store as much context as we need
22  * to save in there. That includes saving the SPRGs used by the TLB miss
23  * handler for linear mapping misses and the associated SRR0/1 due to
24  * the above re-entrancy issue.
25  *
26  * So here's the current usage pattern. It's done regardless of which
27  * SPRGs are user-readable though, thus we might have to change some of
28  * this later. In order to do that more easily, we use special constants
29  * for naming them
30  *
31  * WARNING: Some of these SPRGs are user readable. We need to do something
32  * about it as some point by making sure they can't be used to leak kernel
33  * critical data
34  */
35 
36 #define PACA_EXGDBELL PACA_EXGEN
37 
38 /* We are out of SPRGs so we save some things in the PACA. The normal
39  * exception frame is smaller than the CRIT or MC one though
40  */
41 #define EX_R1		(0 * 8)
42 #define EX_CR		(1 * 8)
43 #define EX_R10		(2 * 8)
44 #define EX_R11		(3 * 8)
45 #define EX_R14		(4 * 8)
46 #define EX_R15		(5 * 8)
47 
48 /*
49  * The TLB miss exception uses different slots.
50  *
51  * The bolted variant uses only the first six fields,
52  * which in combination with pgd and kernel_pgd fits in
53  * one 64-byte cache line.
54  */
55 
56 #define EX_TLB_R10	( 0 * 8)
57 #define EX_TLB_R11	( 1 * 8)
58 #define EX_TLB_R14	( 2 * 8)
59 #define EX_TLB_R15	( 3 * 8)
60 #define EX_TLB_R16	( 4 * 8)
61 #define EX_TLB_CR	( 5 * 8)
62 #define EX_TLB_R12	( 6 * 8)
63 #define EX_TLB_R13	( 7 * 8)
64 #define EX_TLB_DEAR	( 8 * 8) /* Level 0 and 2 only */
65 #define EX_TLB_ESR	( 9 * 8) /* Level 0 and 2 only */
66 #define EX_TLB_SRR0	(10 * 8)
67 #define EX_TLB_SRR1	(11 * 8)
68 #define EX_TLB_R7	(12 * 8)
69 #define EX_TLB_SIZE	(13 * 8)
70 
71 #define	START_EXCEPTION(label)						\
72 	.globl exc_##label##_book3e;					\
73 exc_##label##_book3e:
74 
75 /* TLB miss exception prolog
76  *
77  * This prolog handles re-entrancy (up to 3 levels supported in the PACA
78  * though we currently don't test for overflow). It provides you with a
79  * re-entrancy safe working space of r10...r16 and CR with r12 being used
80  * as the exception area pointer in the PACA for that level of re-entrancy
81  * and r13 containing the PACA pointer.
82  *
83  * SRR0 and SRR1 are saved, but DEAR and ESR are not, since they don't apply
84  * as-is for instruction exceptions. It's up to the actual exception code
85  * to save them as well if required.
86  */
87 #define TLB_MISS_PROLOG							    \
88 	mtspr	SPRN_SPRG_TLB_SCRATCH,r12;				    \
89 	mfspr	r12,SPRN_SPRG_TLB_EXFRAME;				    \
90 	std	r10,EX_TLB_R10(r12);					    \
91 	mfcr	r10;							    \
92 	std	r11,EX_TLB_R11(r12);					    \
93 	mfspr	r11,SPRN_SPRG_TLB_SCRATCH;				    \
94 	std	r13,EX_TLB_R13(r12);					    \
95 	mfspr	r13,SPRN_SPRG_PACA;					    \
96 	std	r14,EX_TLB_R14(r12);					    \
97 	addi	r14,r12,EX_TLB_SIZE;					    \
98 	std	r15,EX_TLB_R15(r12);					    \
99 	mfspr	r15,SPRN_SRR1;						    \
100 	std	r16,EX_TLB_R16(r12);					    \
101 	mfspr	r16,SPRN_SRR0;						    \
102 	std	r10,EX_TLB_CR(r12);					    \
103 	std	r11,EX_TLB_R12(r12);					    \
104 	mtspr	SPRN_SPRG_TLB_EXFRAME,r14;				    \
105 	std	r15,EX_TLB_SRR1(r12);					    \
106 	std	r16,EX_TLB_SRR0(r12);
107 
108 /* And these are the matching epilogs that restores things
109  *
110  * There are 3 epilogs:
111  *
112  * - SUCCESS       : Unwinds one level
113  * - ERROR         : restore from level 0 and reset
114  * - ERROR_SPECIAL : restore from current level and reset
115  *
116  * Normal errors use ERROR, that is, they restore the initial fault context
117  * and trigger a fault. However, there is a special case for linear mapping
118  * errors. Those should basically never happen, but if they do happen, we
119  * want the error to point out the context that did that linear mapping
120  * fault, not the initial level 0 (basically, we got a bogus PGF or something
121  * like that). For userland errors on the linear mapping, there is no
122  * difference since those are always level 0 anyway
123  */
124 
125 #define TLB_MISS_RESTORE(freg)						    \
126 	ld	r14,EX_TLB_CR(r12);					    \
127 	ld	r10,EX_TLB_R10(r12);					    \
128 	ld	r15,EX_TLB_SRR0(r12);					    \
129 	ld	r16,EX_TLB_SRR1(r12);					    \
130 	mtspr	SPRN_SPRG_TLB_EXFRAME,freg;				    \
131 	ld	r11,EX_TLB_R11(r12);					    \
132 	mtcr	r14;							    \
133 	ld	r13,EX_TLB_R13(r12);					    \
134 	ld	r14,EX_TLB_R14(r12);					    \
135 	mtspr	SPRN_SRR0,r15;						    \
136 	ld	r15,EX_TLB_R15(r12);					    \
137 	mtspr	SPRN_SRR1,r16;						    \
138 	ld	r16,EX_TLB_R16(r12);					    \
139 	ld	r12,EX_TLB_R12(r12);					    \
140 
141 #define TLB_MISS_EPILOG_SUCCESS						    \
142 	TLB_MISS_RESTORE(r12)
143 
144 #define TLB_MISS_EPILOG_ERROR						    \
145 	addi	r12,r13,PACA_EXTLB;					    \
146 	TLB_MISS_RESTORE(r12)
147 
148 #define TLB_MISS_EPILOG_ERROR_SPECIAL					    \
149 	addi	r11,r13,PACA_EXTLB;					    \
150 	TLB_MISS_RESTORE(r11)
151 
152 #define SET_IVOR(vector_number, vector_offset)	\
153 	LOAD_REG_ADDR(r3,interrupt_base_book3e);\
154 	ori	r3,r3,vector_offset@l;		\
155 	mtspr	SPRN_IVOR##vector_number,r3;
156 /*
157  * powerpc relies on return from interrupt/syscall being context synchronising
158  * (which rfi is) to support ARCH_HAS_MEMBARRIER_SYNC_CORE without additional
159  * synchronisation instructions.
160  */
161 #define RFI_TO_KERNEL							\
162 	rfi
163 
164 #define RFI_TO_USER							\
165 	rfi
166 
167 #endif /* _ASM_POWERPC_EXCEPTION_64E_H */
168 
169