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cc562d2e VG |
1 | /* |
2 | * TLB Exception Handling for ARC | |
3 | * | |
4 | * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or modify | |
7 | * it under the terms of the GNU General Public License version 2 as | |
8 | * published by the Free Software Foundation. | |
9 | * | |
10 | * Vineetg: April 2011 : | |
11 | * -MMU v1: moved out legacy code into a seperate file | |
12 | * -MMU v3: PD{0,1} bits layout changed: They don't overlap anymore, | |
13 | * helps avoid a shift when preparing PD0 from PTE | |
14 | * | |
15 | * Vineetg: July 2009 | |
16 | * -For MMU V2, we need not do heuristics at the time of commiting a D-TLB | |
17 | * entry, so that it doesn't knock out it's I-TLB entry | |
18 | * -Some more fine tuning: | |
19 | * bmsk instead of add, asl.cc instead of branch, delay slot utilise etc | |
20 | * | |
21 | * Vineetg: July 2009 | |
22 | * -Practically rewrote the I/D TLB Miss handlers | |
23 | * Now 40 and 135 instructions a peice as compared to 131 and 449 resp. | |
24 | * Hence Leaner by 1.5 K | |
25 | * Used Conditional arithmetic to replace excessive branching | |
26 | * Also used short instructions wherever possible | |
27 | * | |
28 | * Vineetg: Aug 13th 2008 | |
29 | * -Passing ECR (Exception Cause REG) to do_page_fault( ) for printing | |
30 | * more information in case of a Fatality | |
31 | * | |
32 | * Vineetg: March 25th Bug #92690 | |
33 | * -Added Debug Code to check if sw-ASID == hw-ASID | |
34 | ||
35 | * Rahul Trivedi, Amit Bhor: Codito Technologies 2004 | |
36 | */ | |
37 | ||
38 | .cpu A7 | |
39 | ||
40 | #include <linux/linkage.h> | |
41 | #include <asm/entry.h> | |
42 | #include <asm/tlb.h> | |
43 | #include <asm/pgtable.h> | |
44 | #include <asm/arcregs.h> | |
45 | #include <asm/cache.h> | |
46 | #include <asm/processor.h> | |
47 | #if (CONFIG_ARC_MMU_VER == 1) | |
48 | #include <asm/tlb-mmu1.h> | |
49 | #endif | |
50 | ||
51 | ;-------------------------------------------------------------------------- | |
52 | ; scratch memory to save the registers (r0-r3) used to code TLB refill Handler | |
53 | ; For details refer to comments before TLBMISS_FREEUP_REGS below | |
54 | ;-------------------------------------------------------------------------- | |
55 | ||
56 | .section .data | |
57 | .global ex_saved_reg1 | |
58 | .align 1 << L1_CACHE_SHIFT ; IMP: Must be Cache Line aligned | |
59 | .type ex_saved_reg1, @object | |
60 | .size ex_saved_reg1, 16 | |
61 | ex_saved_reg1: | |
62 | .zero 16 | |
63 | ||
64 | ;============================================================================ | |
65 | ; Troubleshooting Stuff | |
66 | ;============================================================================ | |
67 | ||
68 | ; Linux keeps ASID (Address Space ID) in task->active_mm->context.asid | |
69 | ; When Creating TLB Entries, instead of doing 3 dependent loads from memory, | |
70 | ; we use the MMU PID Reg to get current ASID. | |
71 | ; In bizzare scenrios SW and HW ASID can get out-of-sync which is trouble. | |
72 | ; So we try to detect this in TLB Mis shandler | |
73 | ||
74 | ||
75 | .macro DBG_ASID_MISMATCH | |
76 | ||
77 | #ifdef CONFIG_ARC_DBG_TLB_PARANOIA | |
78 | ||
79 | ; make sure h/w ASID is same as s/w ASID | |
80 | ||
81 | GET_CURR_TASK_ON_CPU r3 | |
82 | ld r0, [r3, TASK_ACT_MM] | |
83 | ld r0, [r0, MM_CTXT+MM_CTXT_ASID] | |
84 | ||
85 | lr r1, [ARC_REG_PID] | |
86 | and r1, r1, 0xFF | |
87 | breq r1, r0, 5f | |
88 | ||
89 | ; Error if H/w and S/w ASID don't match, but NOT if in kernel mode | |
90 | lr r0, [erstatus] | |
91 | bbit0 r0, STATUS_U_BIT, 5f | |
92 | ||
93 | ; We sure are in troubled waters, Flag the error, but to do so | |
94 | ; need to switch to kernel mode stack to call error routine | |
95 | GET_TSK_STACK_BASE r3, sp | |
96 | ||
97 | ; Call printk to shoutout aloud | |
98 | mov r0, 1 | |
99 | j print_asid_mismatch | |
100 | ||
101 | 5: ; ASIDs match so proceed normally | |
102 | nop | |
103 | ||
104 | #endif | |
105 | ||
106 | .endm | |
107 | ||
108 | ;============================================================================ | |
109 | ;TLB Miss handling Code | |
110 | ;============================================================================ | |
111 | ||
112 | ;----------------------------------------------------------------------------- | |
113 | ; This macro does the page-table lookup for the faulting address. | |
114 | ; OUT: r0 = PTE faulted on, r1 = ptr to PTE, r2 = Faulting V-address | |
115 | .macro LOAD_FAULT_PTE | |
116 | ||
117 | lr r2, [efa] | |
118 | ||
119 | lr r1, [ARC_REG_SCRATCH_DATA0] ; current pgd | |
120 | ||
121 | lsr r0, r2, PGDIR_SHIFT ; Bits for indexing into PGD | |
122 | ld.as r1, [r1, r0] ; PGD entry corresp to faulting addr | |
123 | and.f r1, r1, PAGE_MASK ; Ignoring protection and other flags | |
124 | ; contains Ptr to Page Table | |
125 | bz.d do_slow_path_pf ; if no Page Table, do page fault | |
126 | ||
127 | ; Get the PTE entry: The idea is | |
128 | ; (1) x = addr >> PAGE_SHIFT -> masks page-off bits from @fault-addr | |
129 | ; (2) y = x & (PTRS_PER_PTE - 1) -> to get index | |
130 | ; (3) z = pgtbl[y] | |
131 | ; To avoid the multiply by in end, we do the -2, <<2 below | |
132 | ||
133 | lsr r0, r2, (PAGE_SHIFT - 2) | |
134 | and r0, r0, ( (PTRS_PER_PTE - 1) << 2) | |
135 | ld.aw r0, [r1, r0] ; get PTE and PTE ptr for fault addr | |
0ef88a54 VG |
136 | #ifdef CONFIG_ARC_DBG_TLB_MISS_COUNT |
137 | and.f 0, r0, _PAGE_PRESENT | |
138 | bz 1f | |
139 | ld r2, [num_pte_not_present] | |
140 | add r2, r2, 1 | |
141 | st r2, [num_pte_not_present] | |
142 | 1: | |
143 | #endif | |
cc562d2e VG |
144 | |
145 | .endm | |
146 | ||
147 | ;----------------------------------------------------------------- | |
148 | ; Convert Linux PTE entry into TLB entry | |
149 | ; A one-word PTE entry is programmed as two-word TLB Entry [PD0:PD1] in mmu | |
150 | ; IN: r0 = PTE, r1 = ptr to PTE | |
151 | ||
152 | .macro CONV_PTE_TO_TLB | |
153 | and r3, r0, PTE_BITS_IN_PD1 ; Extract permission flags+PFN from PTE | |
154 | sr r3, [ARC_REG_TLBPD1] ; these go in PD1 | |
155 | ||
156 | and r2, r0, PTE_BITS_IN_PD0 ; Extract other PTE flags: (V)alid, (G)lb | |
157 | #if (CONFIG_ARC_MMU_VER <= 2) /* Neednot be done with v3 onwards */ | |
158 | lsr r2, r2 ; shift PTE flags to match layout in PD0 | |
159 | #endif | |
160 | ||
161 | lr r3,[ARC_REG_TLBPD0] ; MMU prepares PD0 with vaddr and asid | |
162 | ||
163 | or r3, r3, r2 ; S | vaddr | {sasid|asid} | |
164 | sr r3,[ARC_REG_TLBPD0] ; rewrite PD0 | |
165 | .endm | |
166 | ||
167 | ;----------------------------------------------------------------- | |
168 | ; Commit the TLB entry into MMU | |
169 | ||
170 | .macro COMMIT_ENTRY_TO_MMU | |
171 | ||
172 | /* Get free TLB slot: Set = computed from vaddr, way = random */ | |
173 | sr TLBGetIndex, [ARC_REG_TLBCOMMAND] | |
174 | ||
175 | /* Commit the Write */ | |
176 | #if (CONFIG_ARC_MMU_VER >= 2) /* introduced in v2 */ | |
177 | sr TLBWriteNI, [ARC_REG_TLBCOMMAND] | |
178 | #else | |
179 | sr TLBWrite, [ARC_REG_TLBCOMMAND] | |
180 | #endif | |
181 | .endm | |
182 | ||
183 | ;----------------------------------------------------------------- | |
184 | ; ARC700 Exception Handling doesn't auto-switch stack and it only provides | |
185 | ; ONE scratch AUX reg "ARC_REG_SCRATCH_DATA0" | |
186 | ; | |
187 | ; For Non-SMP, the scratch AUX reg is repurposed to cache task PGD, so a | |
188 | ; "global" is used to free-up FIRST core reg to be able to code the rest of | |
189 | ; exception prologue (IRQ auto-disabled on Exceptions, so it's IRQ-safe). | |
190 | ; Since the Fast Path TLB Miss handler is coded with 4 regs, the remaining 3 | |
191 | ; need to be saved as well by extending the "global" to be 4 words. Hence | |
192 | ; ".size ex_saved_reg1, 16" | |
193 | ; [All of this dance is to avoid stack switching for each TLB Miss, since we | |
194 | ; only need to save only a handful of regs, as opposed to complete reg file] | |
195 | ||
196 | ; As simple as that.... | |
197 | ||
198 | .macro TLBMISS_FREEUP_REGS | |
199 | st r0, [@ex_saved_reg1] | |
200 | mov_s r0, @ex_saved_reg1 | |
201 | st_s r1, [r0, 4] | |
202 | st_s r2, [r0, 8] | |
203 | st_s r3, [r0, 12] | |
204 | ||
205 | ; VERIFY if the ASID in MMU-PID Reg is same as | |
206 | ; one in Linux data structures | |
207 | ||
208 | DBG_ASID_MISMATCH | |
209 | .endm | |
210 | ||
211 | ;----------------------------------------------------------------- | |
212 | .macro TLBMISS_RESTORE_REGS | |
213 | mov_s r0, @ex_saved_reg1 | |
214 | ld_s r3, [r0,12] | |
215 | ld_s r2, [r0, 8] | |
216 | ld_s r1, [r0, 4] | |
217 | ld_s r0, [r0] | |
218 | .endm | |
219 | ||
220 | .section .text, "ax",@progbits ;Fast Path Code, candidate for ICCM | |
221 | ||
222 | ;----------------------------------------------------------------------------- | |
223 | ; I-TLB Miss Exception Handler | |
224 | ;----------------------------------------------------------------------------- | |
225 | ||
226 | ARC_ENTRY EV_TLBMissI | |
227 | ||
228 | TLBMISS_FREEUP_REGS | |
229 | ||
0ef88a54 VG |
230 | #ifdef CONFIG_ARC_DBG_TLB_MISS_COUNT |
231 | ld r0, [@numitlb] | |
232 | add r0, r0, 1 | |
233 | st r0, [@numitlb] | |
234 | #endif | |
235 | ||
cc562d2e VG |
236 | ;---------------------------------------------------------------- |
237 | ; Get the PTE corresponding to V-addr accessed | |
238 | LOAD_FAULT_PTE | |
239 | ||
240 | ;---------------------------------------------------------------- | |
241 | ; VERIFY_PTE: Check if PTE permissions approp for executing code | |
242 | cmp_s r2, VMALLOC_START | |
243 | mov.lo r2, (_PAGE_PRESENT | _PAGE_READ | _PAGE_EXECUTE) | |
244 | mov.hs r2, (_PAGE_PRESENT | _PAGE_K_READ | _PAGE_K_EXECUTE) | |
245 | ||
246 | and r3, r0, r2 ; Mask out NON Flag bits from PTE | |
247 | xor.f r3, r3, r2 ; check ( ( pte & flags_test ) == flags_test ) | |
248 | bnz do_slow_path_pf | |
249 | ||
250 | ; Let Linux VM know that the page was accessed | |
251 | or r0, r0, (_PAGE_PRESENT | _PAGE_ACCESSED) ; set Accessed Bit | |
252 | st_s r0, [r1] ; Write back PTE | |
253 | ||
254 | CONV_PTE_TO_TLB | |
255 | COMMIT_ENTRY_TO_MMU | |
256 | TLBMISS_RESTORE_REGS | |
257 | rtie | |
258 | ||
259 | ARC_EXIT EV_TLBMissI | |
260 | ||
261 | ;----------------------------------------------------------------------------- | |
262 | ; D-TLB Miss Exception Handler | |
263 | ;----------------------------------------------------------------------------- | |
264 | ||
265 | ARC_ENTRY EV_TLBMissD | |
266 | ||
267 | TLBMISS_FREEUP_REGS | |
268 | ||
0ef88a54 VG |
269 | #ifdef CONFIG_ARC_DBG_TLB_MISS_COUNT |
270 | ld r0, [@numdtlb] | |
271 | add r0, r0, 1 | |
272 | st r0, [@numdtlb] | |
273 | #endif | |
274 | ||
cc562d2e VG |
275 | ;---------------------------------------------------------------- |
276 | ; Get the PTE corresponding to V-addr accessed | |
277 | ; If PTE exists, it will setup, r0 = PTE, r1 = Ptr to PTE | |
278 | LOAD_FAULT_PTE | |
279 | ||
280 | ;---------------------------------------------------------------- | |
281 | ; VERIFY_PTE: Chk if PTE permissions approp for data access (R/W/R+W) | |
282 | ||
283 | mov_s r2, 0 | |
284 | lr r3, [ecr] | |
285 | btst_s r3, ECR_C_BIT_DTLB_LD_MISS ; Read Access | |
286 | or.nz r2, r2, _PAGE_READ ; chk for Read flag in PTE | |
287 | btst_s r3, ECR_C_BIT_DTLB_ST_MISS ; Write Access | |
288 | or.nz r2, r2, _PAGE_WRITE ; chk for Write flag in PTE | |
289 | ; Above laddering takes care of XCHG access | |
290 | ; which is both Read and Write | |
291 | ||
292 | ; If kernel mode access, ; make _PAGE_xx flags as _PAGE_K_xx | |
293 | ; For copy_(to|from)_user, despite exception taken in kernel mode, | |
294 | ; this code is not hit, because EFA would still be the user mode | |
295 | ; address (EFA < 0x6000_0000). | |
296 | ; This code is for legit kernel mode faults, vmalloc specifically | |
297 | ; (EFA: 0x7000_0000 to 0x7FFF_FFFF) | |
298 | ||
299 | lr r3, [efa] | |
300 | cmp r3, VMALLOC_START - 1 ; If kernel mode access | |
301 | asl.hi r2, r2, 3 ; make _PAGE_xx flags as _PAGE_K_xx | |
302 | or r2, r2, _PAGE_PRESENT ; Common flag for K/U mode | |
303 | ||
304 | ; By now, r2 setup with all the Flags we need to check in PTE | |
305 | and r3, r0, r2 ; Mask out NON Flag bits from PTE | |
306 | brne.d r3, r2, do_slow_path_pf ; is ((pte & flags_test) == flags_test) | |
307 | ||
308 | ;---------------------------------------------------------------- | |
309 | ; UPDATE_PTE: Let Linux VM know that page was accessed/dirty | |
310 | lr r3, [ecr] | |
311 | or r0, r0, (_PAGE_PRESENT | _PAGE_ACCESSED) ; Accessed bit always | |
312 | btst_s r3, ECR_C_BIT_DTLB_ST_MISS ; See if it was a Write Access ? | |
313 | or.nz r0, r0, _PAGE_MODIFIED ; if Write, set Dirty bit as well | |
314 | st_s r0, [r1] ; Write back PTE | |
315 | ||
316 | CONV_PTE_TO_TLB | |
317 | ||
318 | #if (CONFIG_ARC_MMU_VER == 1) | |
319 | ; MMU with 2 way set assoc J-TLB, needs some help in pathetic case of | |
320 | ; memcpy where 3 parties contend for 2 ways, ensuing a livelock. | |
321 | ; But only for old MMU or one with Metal Fix | |
322 | TLB_WRITE_HEURISTICS | |
323 | #endif | |
324 | ||
325 | COMMIT_ENTRY_TO_MMU | |
326 | TLBMISS_RESTORE_REGS | |
327 | rtie | |
328 | ||
329 | ;-------- Common routine to call Linux Page Fault Handler ----------- | |
330 | do_slow_path_pf: | |
331 | ||
332 | ; Restore the 4-scratch regs saved by fast path miss handler | |
333 | TLBMISS_RESTORE_REGS | |
334 | ||
335 | ; Slow path TLB Miss handled as a regular ARC Exception | |
336 | ; (stack switching / save the complete reg-file). | |
337 | ; That requires freeing up r9 | |
338 | EXCPN_PROLOG_FREEUP_REG r9 | |
339 | ||
340 | lr r9, [erstatus] | |
341 | ||
342 | SWITCH_TO_KERNEL_STK | |
343 | SAVE_ALL_SYS | |
344 | ||
345 | ; ------- setup args for Linux Page fault Hanlder --------- | |
346 | mov_s r0, sp | |
347 | lr r2, [efa] | |
348 | lr r3, [ecr] | |
349 | ||
350 | ; Both st and ex imply WRITE access of some sort, hence do_page_fault( ) | |
351 | ; invoked with write=1 for DTLB-st/ex Miss and write=0 for ITLB miss or | |
352 | ; DTLB-ld Miss | |
353 | ; DTLB Miss Cause code is ld = 0x01 , st = 0x02, ex = 0x03 | |
354 | ; Following code uses that fact that st/ex have one bit in common | |
355 | ||
356 | btst_s r3, ECR_C_BIT_DTLB_ST_MISS | |
357 | mov.z r1, 0 | |
358 | mov.nz r1, 1 | |
359 | ||
360 | ; We don't want exceptions to be disabled while the fault is handled. | |
361 | ; Now that we have saved the context we return from exception hence | |
362 | ; exceptions get re-enable | |
363 | ||
364 | FAKE_RET_FROM_EXCPN r9 | |
365 | ||
366 | bl do_page_fault | |
367 | b ret_from_exception | |
368 | ||
369 | ARC_EXIT EV_TLBMissD | |
370 | ||
371 | ARC_ENTRY EV_TLBMissB ; Bogus entry to measure sz of DTLBMiss hdlr |