Loading...
1; WARNING : The refill handler has been modified, see below !!!
2
3/*
4 * Copyright (C) 2003 Axis Communications AB
5 *
6 * Authors: Mikael Starvik (starvik@axis.com)
7 *
8 * Code for the fault low-level handling routines.
9 *
10 */
11
12#include <asm/page.h>
13#include <asm/pgtable.h>
14
15; Save all register. Must save in same order as struct pt_regs.
16.macro SAVE_ALL
17 subq 12, $sp
18 move $erp, [$sp]
19 subq 4, $sp
20 move $srp, [$sp]
21 subq 4, $sp
22 move $ccs, [$sp]
23 subq 4, $sp
24 move $spc, [$sp]
25 subq 4, $sp
26 move $mof, [$sp]
27 subq 4, $sp
28 move $srs, [$sp]
29 subq 4, $sp
30 move.d $acr, [$sp]
31 subq 14*4, $sp
32 movem $r13, [$sp]
33 subq 4, $sp
34 move.d $r10, [$sp]
35.endm
36
37; Bus fault handler. Extracts relevant information and calls mm subsystem
38; to handle the fault.
39.macro MMU_BUS_FAULT_HANDLER handler, mmu, we, ex
40 .globl \handler
41 .type \handler,"function"
42\handler:
43 SAVE_ALL
44 move \mmu, $srs ; Select MMU support register bank
45 move.d $sp, $r11 ; regs
46 moveq 1, $r12 ; protection fault
47 moveq \we, $r13 ; write exception?
48 orq \ex << 1, $r13 ; execute?
49 move $s3, $r10 ; rw_mm_cause
50 and.d ~8191, $r10 ; Get faulting page start address
51
52 jsr do_page_fault
53 nop
54 ba ret_from_intr
55 nop
56 .size \handler, . - \handler
57.endm
58
59; Refill handler. Three cases may occur:
60; 1. PMD and PTE exists in mm subsystem but not in TLB
61; 2. PMD exists but not PTE
62; 3. PMD doesn't exist
63; The code below handles case 1 and calls the mm subsystem for case 2 and 3.
64; Do not touch this code without very good reasons and extensive testing.
65; Note that the code is optimized to minimize stalls (makes the code harder
66; to read).
67;
68; WARNING !!!
69; Modified by Mikael Asker 060725: added a workaround for strange TLB
70; behavior. If the same PTE is present in more than one set, the TLB
71; doesn't recognize it and we get stuck in a loop of refill exceptions.
72; The workaround detects such loops and exits them by flushing
73; the TLB contents. The problem and workaround were verified
74; in VCS by Mikael Starvik.
75;
76; Each page is 8 KB. Each PMD holds 8192/4 PTEs (each PTE is 4 bytes) so each
77; PMD holds 16 MB of virtual memory.
78; Bits 0-12 : Offset within a page
79; Bits 13-23 : PTE offset within a PMD
80; Bits 24-31 : PMD offset within the PGD
81
82.macro MMU_REFILL_HANDLER handler, mmu
83 .data
841: .dword 0 ; refill_count
85 ; == 0 <=> last_refill_cause is invalid
862: .dword 0 ; last_refill_cause
87 .text
88 .globl \handler
89 .type \handler, "function"
90\handler:
91 subq 4, $sp
92; (The pipeline stalls for one cycle; $sp used as address in the next cycle.)
93 move $srs, [$sp]
94 subq 4, $sp
95 move \mmu, $srs ; Select MMU support register bank
96 move.d $acr, [$sp]
97 subq 12, $sp
98 move.d 1b, $acr ; Point to refill_count
99 movem $r2, [$sp]
100
101 test.d [$acr] ; refill_count == 0 ?
102 beq 5f ; yes, last_refill_cause is invalid
103 move.d $acr, $r1
104
105 ; last_refill_cause is valid, investigate cause
106 addq 4, $r1 ; Point to last_refill_cause
107 move $s3, $r0 ; Get rw_mm_cause
108 move.d [$r1], $r2 ; Get last_refill_cause
109 cmp.d $r0, $r2 ; rw_mm_cause == last_refill_cause ?
110 beq 6f ; yes, increment count
111 moveq 1, $r2
112
113 ; rw_mm_cause != last_refill_cause
114 move.d $r2, [$acr] ; refill_count = 1
115 move.d $r0, [$r1] ; last_refill_cause = rw_mm_cause
116
1173: ; Probably not in a loop, continue normal processing
118#ifdef CONFIG_SMP
119 move $s7, $acr ; PGD
120#else
121 move.d current_pgd, $acr ; PGD
122#endif
123 ; Look up PMD in PGD
124 lsrq 24, $r0 ; Get PMD index into PGD (bit 24-31)
125 move.d [$acr], $acr ; PGD for the current process
126 addi $r0.d, $acr, $acr
127 move $s3, $r0 ; rw_mm_cause
128 move.d [$acr], $acr ; Get PMD
129 beq 8f
130 ; Look up PTE in PMD
131 lsrq PAGE_SHIFT, $r0
132 and.w PAGE_MASK, $acr ; Remove PMD flags
133 and.d 0x7ff, $r0 ; Get PTE index into PMD (bit 13-23)
134 addi $r0.d, $acr, $acr
135 move.d [$acr], $acr ; Get PTE
136 beq 9f
137 movem [$sp], $r2 ; Restore r0-r2 in delay slot
138 addq 12, $sp
139 ; Store in TLB
140 move $acr, $s5
1414: ; Return
142 move.d [$sp+], $acr
143 move [$sp], $srs
144 addq 4, $sp
145 rete
146 rfe
147
1485: ; last_refill_cause is invalid
149 moveq 1, $r2
150 addq 4, $r1 ; Point to last_refill_cause
151 move.d $r2, [$acr] ; refill_count = 1
152 move $s3, $r0 ; Get rw_mm_cause
153 ba 3b ; Continue normal processing
154 move.d $r0,[$r1] ; last_refill_cause = rw_mm_cause
155
1566: ; rw_mm_cause == last_refill_cause
157 move.d [$acr], $r2 ; Get refill_count
158 cmpq 4, $r2 ; refill_count > 4 ?
159 bhi 7f ; yes
160 addq 1, $r2 ; refill_count++
161 ba 3b ; Continue normal processing
162 move.d $r2, [$acr]
163
1647: ; refill_count > 4, error
165 move.d $acr, $r0 ; Save pointer to refill_count
166 clear.d [$r0] ; refill_count = 0
167
168 ;; rewind the short stack
169 movem [$sp], $r2 ; Restore r0-r2
170 addq 12, $sp
171 move.d [$sp+], $acr
172 move [$sp], $srs
173 addq 4, $sp
174 ;; Keep it simple (slow), save all the regs.
175 SAVE_ALL
176 jsr __flush_tlb_all
177 nop
178 ba ret_from_intr ; Return
179 nop
180
1818: ; PMD missing, let the mm subsystem fix it up.
182 movem [$sp], $r2 ; Restore r0-r2
1839: ; PTE missing, let the mm subsystem fix it up.
184 addq 12, $sp
185 move.d [$sp+], $acr
186 move [$sp], $srs
187 addq 4, $sp
188 SAVE_ALL
189 move \mmu, $srs
190 move.d $sp, $r11 ; regs
191 clear.d $r12 ; Not a protection fault
192 move.w PAGE_MASK, $acr
193 move $s3, $r10 ; rw_mm_cause
194 btstq 9, $r10 ; Check if write access
195 smi $r13
196 and.w PAGE_MASK, $r10 ; Get VPN (virtual address)
197 jsr do_page_fault
198 and.w $acr, $r10
199 ; Return
200 ba ret_from_intr
201 nop
202 .size \handler, . - \handler
203.endm
204
205 ; This is the MMU bus fault handlers.
206
207MMU_REFILL_HANDLER i_mmu_refill, 1
208MMU_BUS_FAULT_HANDLER i_mmu_invalid, 1, 0, 0
209MMU_BUS_FAULT_HANDLER i_mmu_access, 1, 0, 0
210MMU_BUS_FAULT_HANDLER i_mmu_execute, 1, 0, 1
211MMU_REFILL_HANDLER d_mmu_refill, 2
212MMU_BUS_FAULT_HANDLER d_mmu_invalid, 2, 0, 0
213MMU_BUS_FAULT_HANDLER d_mmu_access, 2, 0, 0
214MMU_BUS_FAULT_HANDLER d_mmu_write, 2, 1, 0