1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
|
; WARNING : The refill handler has been modified, see below !!!
/*
* Copyright (C) 2003 Axis Communications AB
*
* Authors: Mikael Starvik (starvik@axis.com)
*
* Code for the fault low-level handling routines.
*
*/
#include <asm/page.h>
#include <asm/pgtable.h>
; Save all register. Must save in same order as struct pt_regs.
.macro SAVE_ALL
subq 12, $sp
move $erp, [$sp]
subq 4, $sp
move $srp, [$sp]
subq 4, $sp
move $ccs, [$sp]
subq 4, $sp
move $spc, [$sp]
subq 4, $sp
move $mof, [$sp]
subq 4, $sp
move $srs, [$sp]
subq 4, $sp
move.d $acr, [$sp]
subq 14*4, $sp
movem $r13, [$sp]
subq 4, $sp
move.d $r10, [$sp]
.endm
; Bus fault handler. Extracts relevant information and calls mm subsystem
; to handle the fault.
.macro MMU_BUS_FAULT_HANDLER handler, mmu, we, ex
.globl \handler
\handler:
SAVE_ALL
move \mmu, $srs ; Select MMU support register bank
move.d $sp, $r11 ; regs
moveq 1, $r12 ; protection fault
moveq \we, $r13 ; write exception?
orq \ex << 1, $r13 ; execute?
move $s3, $r10 ; rw_mm_cause
and.d ~8191, $r10 ; Get faulting page start address
jsr do_page_fault
nop
ba ret_from_intr
nop
.endm
; Refill handler. Three cases may occur:
; 1. PMD and PTE exists in mm subsystem but not in TLB
; 2. PMD exists but not PTE
; 3. PMD doesn't exist
; The code below handles case 1 and calls the mm subsystem for case 2 and 3.
; Do not touch this code without very good reasons and extensive testing.
; Note that the code is optimized to minimize stalls (makes the code harder
; to read).
;
; WARNING !!!
; Modified by Mikael Asker 060725: added a workaround for strange TLB
; behavior. If the same PTE is present in more than one set, the TLB
; doesn't recognize it and we get stuck in a loop of refill exceptions.
; The workaround detects such loops and exits them by flushing
; the TLB contents. The problem and workaround were verified
; in VCS by Mikael Starvik.
;
; Each page is 8 KB. Each PMD holds 8192/4 PTEs (each PTE is 4 bytes) so each
; PMD holds 16 MB of virtual memory.
; Bits 0-12 : Offset within a page
; Bits 13-23 : PTE offset within a PMD
; Bits 24-31 : PMD offset within the PGD
.macro MMU_REFILL_HANDLER handler, mmu
.data
1: .dword 0 ; refill_count
; == 0 <=> last_refill_cause is invalid
2: .dword 0 ; last_refill_cause
.text
.globl \handler
\handler:
subq 4, $sp
; (The pipeline stalls for one cycle; $sp used as address in the next cycle.)
move $srs, [$sp]
subq 4, $sp
move \mmu, $srs ; Select MMU support register bank
move.d $acr, [$sp]
subq 12, $sp
move.d 1b, $acr ; Point to refill_count
movem $r2, [$sp]
test.d [$acr] ; refill_count == 0 ?
beq 5f ; yes, last_refill_cause is invalid
move.d $acr, $r1
; last_refill_cause is valid, investigate cause
addq 4, $r1 ; Point to last_refill_cause
move $s3, $r0 ; Get rw_mm_cause
move.d [$r1], $r2 ; Get last_refill_cause
cmp.d $r0, $r2 ; rw_mm_cause == last_refill_cause ?
beq 6f ; yes, increment count
moveq 1, $r2
; rw_mm_cause != last_refill_cause
move.d $r2, [$acr] ; refill_count = 1
move.d $r0, [$r1] ; last_refill_cause = rw_mm_cause
3: ; Probably not in a loop, continue normal processing
#ifdef CONFIG_SMP
move $s7, $acr ; PGD
#else
move.d per_cpu__current_pgd, $acr ; PGD
#endif
; Look up PMD in PGD
lsrq 24, $r0 ; Get PMD index into PGD (bit 24-31)
move.d [$acr], $acr ; PGD for the current process
addi $r0.d, $acr, $acr
move $s3, $r0 ; rw_mm_cause
move.d [$acr], $acr ; Get PMD
beq 8f
; Look up PTE in PMD
lsrq PAGE_SHIFT, $r0
and.w PAGE_MASK, $acr ; Remove PMD flags
and.d 0x7ff, $r0 ; Get PTE index into PMD (bit 13-23)
addi $r0.d, $acr, $acr
move.d [$acr], $acr ; Get PTE
beq 9f
movem [$sp], $r2 ; Restore r0-r2 in delay slot
addq 12, $sp
; Store in TLB
move $acr, $s5
4: ; Return
move.d [$sp+], $acr
move [$sp], $srs
addq 4, $sp
rete
rfe
5: ; last_refill_cause is invalid
moveq 1, $r2
addq 4, $r1 ; Point to last_refill_cause
move.d $r2, [$acr] ; refill_count = 1
move $s3, $r0 ; Get rw_mm_cause
ba 3b ; Continue normal processing
move.d $r0,[$r1] ; last_refill_cause = rw_mm_cause
6: ; rw_mm_cause == last_refill_cause
move.d [$acr], $r2 ; Get refill_count
cmpq 4, $r2 ; refill_count > 4 ?
bhi 7f ; yes
addq 1, $r2 ; refill_count++
ba 3b ; Continue normal processing
move.d $r2, [$acr]
7: ; refill_count > 4, error
move.d $acr, $r0 ; Save pointer to refill_count
clear.d [$r0] ; refill_count = 0
;; rewind the short stack
movem [$sp], $r2 ; Restore r0-r2
addq 12, $sp
move.d [$sp+], $acr
move [$sp], $srs
addq 4, $sp
;; Keep it simple (slow), save all the regs.
SAVE_ALL
jsr __flush_tlb_all
nop
ba ret_from_intr ; Return
nop
8: ; PMD missing, let the mm subsystem fix it up.
movem [$sp], $r2 ; Restore r0-r2
9: ; PTE missing, let the mm subsystem fix it up.
addq 12, $sp
move.d [$sp+], $acr
move [$sp], $srs
addq 4, $sp
SAVE_ALL
move \mmu, $srs
move.d $sp, $r11 ; regs
clear.d $r12 ; Not a protection fault
move.w PAGE_MASK, $acr
move $s3, $r10 ; rw_mm_cause
btstq 9, $r10 ; Check if write access
smi $r13
and.w PAGE_MASK, $r10 ; Get VPN (virtual address)
jsr do_page_fault
and.w $acr, $r10
; Return
ba ret_from_intr
nop
.endm
; This is the MMU bus fault handlers.
MMU_REFILL_HANDLER i_mmu_refill, 1
MMU_BUS_FAULT_HANDLER i_mmu_invalid, 1, 0, 0
MMU_BUS_FAULT_HANDLER i_mmu_access, 1, 0, 0
MMU_BUS_FAULT_HANDLER i_mmu_execute, 1, 0, 1
MMU_REFILL_HANDLER d_mmu_refill, 2
MMU_BUS_FAULT_HANDLER d_mmu_invalid, 2, 0, 0
MMU_BUS_FAULT_HANDLER d_mmu_access, 2, 0, 0
MMU_BUS_FAULT_HANDLER d_mmu_write, 2, 1, 0
|
