1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * TLB Exception Handling for ARC
4 *
5 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
6 *
7 * Vineetg: April 2011 :
8 *  -MMU v1: moved out legacy code into a separate file
9 *  -MMU v3: PD{0,1} bits layout changed: They don't overlap anymore,
10 *      helps avoid a shift when preparing PD0 from PTE
11 *
12 * Vineetg: July 2009
13 *  -For MMU V2, we need not do heuristics at the time of committing a D-TLB
14 *   entry, so that it doesn't knock out its I-TLB entry
15 *  -Some more fine tuning:
16 *   bmsk instead of add, asl.cc instead of branch, delay slot utilise etc
17 *
18 * Vineetg: July 2009
19 *  -Practically rewrote the I/D TLB Miss handlers
20 *   Now 40 and 135 instructions apiece as compared to 131 and 449 resp.
21 *   Hence Leaner by 1.5 K
22 *   Used Conditional arithmetic to replace excessive branching
23 *   Also used short instructions wherever possible
24 *
25 * Vineetg: Aug 13th 2008
26 *  -Passing ECR (Exception Cause REG) to do_page_fault( ) for printing
27 *   more information in case of a Fatality
28 *
29 * Vineetg: March 25th Bug #92690
30 *  -Added Debug Code to check if sw-ASID == hw-ASID
31
32 * Rahul Trivedi, Amit Bhor: Codito Technologies 2004
33 */
34
35#include <linux/linkage.h>
36#include <linux/pgtable.h>
37#include <asm/entry.h>
38#include <asm/mmu.h>
39#include <asm/arcregs.h>
40#include <asm/cache.h>
41#include <asm/processor.h>
42
43#ifdef CONFIG_ISA_ARCOMPACT
44;-----------------------------------------------------------------
45; ARC700 Exception Handling doesn't auto-switch stack and it only provides
46; ONE scratch AUX reg "ARC_REG_SCRATCH_DATA0"
47;
48; For Non-SMP, the scratch AUX reg is repurposed to cache task PGD, so a
49; "global" is used to free-up FIRST core reg to be able to code the rest of
50; exception prologue (IRQ auto-disabled on Exceptions, so it's IRQ-safe).
51; Since the Fast Path TLB Miss handler is coded with 4 regs, the remaining 3
52; need to be saved as well by extending the "global" to be 4 words. Hence
53;	".size   ex_saved_reg1, 16"
54; [All of this dance is to avoid stack switching for each TLB Miss, since we
55; only need to save only a handful of regs, as opposed to complete reg file]
56;
57; For ARC700 SMP, the "global" obviously can't be used for free up the FIRST
58; core reg as it will not be SMP safe.
59; Thus scratch AUX reg is used (and no longer used to cache task PGD).
60; To save the rest of 3 regs - per cpu, the global is made "per-cpu".
61; Epilogue thus has to locate the "per-cpu" storage for regs.
62; To avoid cache line bouncing the per-cpu global is aligned/sized per
63; L1_CACHE_SHIFT, despite fundamentally needing to be 12 bytes only. Hence
64;	".size   ex_saved_reg1, (CONFIG_NR_CPUS << L1_CACHE_SHIFT)"
65
66; As simple as that....
67;--------------------------------------------------------------------------
68
69; scratch memory to save [r0-r3] used to code TLB refill Handler
70ARCFP_DATA ex_saved_reg1
71	.align 1 << L1_CACHE_SHIFT
72	.type   ex_saved_reg1, @object
73#ifdef CONFIG_SMP
74	.size   ex_saved_reg1, (CONFIG_NR_CPUS << L1_CACHE_SHIFT)
75ex_saved_reg1:
76	.zero (CONFIG_NR_CPUS << L1_CACHE_SHIFT)
77#else
78	.size   ex_saved_reg1, 16
79ex_saved_reg1:
80	.zero 16
81#endif
82
83.macro TLBMISS_FREEUP_REGS
84#ifdef CONFIG_SMP
85	sr  r0, [ARC_REG_SCRATCH_DATA0]	; freeup r0 to code with
86	GET_CPU_ID  r0			; get to per cpu scratch mem,
87	asl r0, r0, L1_CACHE_SHIFT	; cache line wide per cpu
88	add r0, @ex_saved_reg1, r0
89#else
90	st    r0, [@ex_saved_reg1]
91	mov_s r0, @ex_saved_reg1
92#endif
93	st_s  r1, [r0, 4]
94	st_s  r2, [r0, 8]
95	st_s  r3, [r0, 12]
96.endm
97
98.macro TLBMISS_RESTORE_REGS
99#ifdef CONFIG_SMP
100	GET_CPU_ID  r0			; get to per cpu scratch mem
101	asl r0, r0, L1_CACHE_SHIFT	; each is cache line wide
102	add r0, @ex_saved_reg1, r0
103	ld_s  r3, [r0,12]
104	ld_s  r2, [r0, 8]
105	ld_s  r1, [r0, 4]
106	lr    r0, [ARC_REG_SCRATCH_DATA0]
107#else
108	mov_s r0, @ex_saved_reg1
109	ld_s  r3, [r0,12]
110	ld_s  r2, [r0, 8]
111	ld_s  r1, [r0, 4]
112	ld_s  r0, [r0]
113#endif
114.endm
115
116#else	/* ARCv2 */
117
118.macro TLBMISS_FREEUP_REGS
119#ifdef CONFIG_ARC_HAS_LL64
120	std   r0, [sp, -16]
121	std   r2, [sp, -8]
122#else
123	PUSH  r0
124	PUSH  r1
125	PUSH  r2
126	PUSH  r3
127#endif
128.endm
129
130.macro TLBMISS_RESTORE_REGS
131#ifdef CONFIG_ARC_HAS_LL64
132	ldd   r0, [sp, -16]
133	ldd   r2, [sp, -8]
134#else
135	POP   r3
136	POP   r2
137	POP   r1
138	POP   r0
139#endif
140.endm
141
142#endif
143
144;============================================================================
145;TLB Miss handling Code
146;============================================================================
147
148#ifndef PMD_SHIFT
149#define PMD_SHIFT PUD_SHIFT
150#endif
151
152#ifndef PUD_SHIFT
153#define PUD_SHIFT PGDIR_SHIFT
154#endif
155
156;-----------------------------------------------------------------------------
157; This macro does the page-table lookup for the faulting address.
158; OUT: r0 = PTE faulted on, r1 = ptr to PTE, r2 = Faulting V-address
159.macro LOAD_FAULT_PTE
160
161	lr  r2, [efa]
162
163#ifdef CONFIG_ISA_ARCV2
164	lr  r1, [ARC_REG_SCRATCH_DATA0] ; current pgd
165#else
166	GET_CURR_TASK_ON_CPU  r1
167	ld  r1, [r1, TASK_ACT_MM]
168	ld  r1, [r1, MM_PGD]
169#endif
170
171	lsr     r0, r2, PGDIR_SHIFT     ; Bits for indexing into PGD
172	ld.as   r3, [r1, r0]            ; PGD entry corresp to faulting addr
173	tst	r3, r3
174	bz	do_slow_path_pf         ; if no Page Table, do page fault
175
176#if CONFIG_PGTABLE_LEVELS > 3
177	lsr     r0, r2, PUD_SHIFT	; Bits for indexing into PUD
178	and	r0, r0, (PTRS_PER_PUD - 1)
179	ld.as	r1, [r3, r0]		; PMD entry
180	tst	r1, r1
181	bz	do_slow_path_pf
182	mov	r3, r1
183#endif
184
185#if CONFIG_PGTABLE_LEVELS > 2
186	lsr     r0, r2, PMD_SHIFT	; Bits for indexing into PMD
187	and	r0, r0, (PTRS_PER_PMD - 1)
188	ld.as	r1, [r3, r0]		; PMD entry
189	tst	r1, r1
190	bz	do_slow_path_pf
191	mov	r3, r1
192#endif
193
194#ifdef CONFIG_TRANSPARENT_HUGEPAGE
195	and.f	0, r3, _PAGE_HW_SZ	; Is this Huge PMD (thp)
196	add2.nz	r1, r1, r0
197	bnz.d	2f		; YES: PGD == PMD has THP PTE: stop pgd walk
198	mov.nz	r0, r3
199
200#endif
201	and	r1, r3, PAGE_MASK
202
203	; Get the PTE entry: The idea is
204	; (1) x = addr >> PAGE_SHIFT 	-> masks page-off bits from @fault-addr
205	; (2) y = x & (PTRS_PER_PTE - 1) -> to get index
206	; (3) z = (pgtbl + y * 4)
207
208#ifdef CONFIG_ARC_HAS_PAE40
209#define PTE_SIZE_LOG	3	/* 8 == 2 ^ 3 */
210#else
211#define PTE_SIZE_LOG	2	/* 4 == 2 ^ 2 */
212#endif
213
214	; multiply in step (3) above avoided by shifting lesser in step (1)
215	lsr     r0, r2, ( PAGE_SHIFT - PTE_SIZE_LOG )
216	and     r0, r0, ( (PTRS_PER_PTE - 1) << PTE_SIZE_LOG )
217	ld.aw   r0, [r1, r0]            ; r0: PTE (lower word only for PAE40)
218					; r1: PTE ptr
219
2202:
221
222.endm
223
224;-----------------------------------------------------------------
225; Convert Linux PTE entry into TLB entry
226; A one-word PTE entry is programmed as two-word TLB Entry [PD0:PD1] in mmu
227;    (for PAE40, two-words PTE, while three-word TLB Entry [PD0:PD1:PD1HI])
228; IN: r0 = PTE, r1 = ptr to PTE
229
230.macro CONV_PTE_TO_TLB
231	and    r3, r0, PTE_BITS_RWX	;          r  w  x
232	asl    r2, r3, 3		; Kr Kw Kx 0  0  0 (GLOBAL, kernel only)
233	and.f  0,  r0, _PAGE_GLOBAL
234	or.z   r2, r2, r3		; Kr Kw Kx Ur Uw Ux (!GLOBAL, user page)
235
236	and r3, r0, PTE_BITS_NON_RWX_IN_PD1 ; Extract PFN+cache bits from PTE
237	or  r3, r3, r2
238
239	sr  r3, [ARC_REG_TLBPD1]    	; paddr[31..13] | Kr Kw Kx Ur Uw Ux | C
240#ifdef	CONFIG_ARC_HAS_PAE40
241	ld	r3, [r1, 4]		; paddr[39..32]
242	sr	r3, [ARC_REG_TLBPD1HI]
243#endif
244
245	and r2, r0, PTE_BITS_IN_PD0 ; Extract other PTE flags: (V)alid, (G)lb
246
247	lr  r3,[ARC_REG_TLBPD0]     ; MMU prepares PD0 with vaddr and asid
248
249	or  r3, r3, r2              ; S | vaddr | {sasid|asid}
250	sr  r3,[ARC_REG_TLBPD0]     ; rewrite PD0
251.endm
252
253;-----------------------------------------------------------------
254; Commit the TLB entry into MMU
255
256.macro COMMIT_ENTRY_TO_MMU
257#ifdef CONFIG_ARC_MMU_V3
258
259	/* Get free TLB slot: Set = computed from vaddr, way = random */
260	sr  TLBGetIndex, [ARC_REG_TLBCOMMAND]
261
262	/* Commit the Write */
263	sr TLBWriteNI, [ARC_REG_TLBCOMMAND]
264
265#else
266	sr TLBInsertEntry, [ARC_REG_TLBCOMMAND]
267#endif
268
26988:
270.endm
271
272
273ARCFP_CODE	;Fast Path Code, candidate for ICCM
274
275;-----------------------------------------------------------------------------
276; I-TLB Miss Exception Handler
277;-----------------------------------------------------------------------------
278
279ENTRY(EV_TLBMissI)
280
281	TLBMISS_FREEUP_REGS
282
283	;----------------------------------------------------------------
284	; Get the PTE corresponding to V-addr accessed, r2 is setup with EFA
285	LOAD_FAULT_PTE
286
287	;----------------------------------------------------------------
288	; VERIFY_PTE: Check if PTE permissions approp for executing code
289	cmp_s   r2, VMALLOC_START
290	mov_s   r2, (_PAGE_PRESENT | _PAGE_EXECUTE)
291	or.hs   r2, r2, _PAGE_GLOBAL
292
293	and     r3, r0, r2  ; Mask out NON Flag bits from PTE
294	xor.f   r3, r3, r2  ; check ( ( pte & flags_test ) == flags_test )
295	bnz     do_slow_path_pf
296
297	; Let Linux VM know that the page was accessed
298	or      r0, r0, _PAGE_ACCESSED  ; set Accessed Bit
299	st_s    r0, [r1]                ; Write back PTE
300
301	CONV_PTE_TO_TLB
302	COMMIT_ENTRY_TO_MMU
303	TLBMISS_RESTORE_REGS
304EV_TLBMissI_fast_ret:	; additional label for VDK OS-kit instrumentation
305	rtie
306
307END(EV_TLBMissI)
308
309;-----------------------------------------------------------------------------
310; D-TLB Miss Exception Handler
311;-----------------------------------------------------------------------------
312
313ENTRY(EV_TLBMissD)
314
315	TLBMISS_FREEUP_REGS
316
317	;----------------------------------------------------------------
318	; Get the PTE corresponding to V-addr accessed
319	; If PTE exists, it will setup, r0 = PTE, r1 = Ptr to PTE, r2 = EFA
320	LOAD_FAULT_PTE
321
322	;----------------------------------------------------------------
323	; VERIFY_PTE: Chk if PTE permissions approp for data access (R/W/R+W)
324
325	cmp_s	r2, VMALLOC_START
326	mov_s   r2, _PAGE_PRESENT	; common bit for K/U PTE
327	or.hs	r2, r2, _PAGE_GLOBAL	; kernel PTE only
328
329	; Linux PTE [RWX] bits are semantically overloaded:
330	; -If PAGE_GLOBAL set, they refer to kernel-only flags (vmalloc)
331	; -Otherwise they are user-mode permissions, and those are exactly
332	;  same for kernel mode as well (e.g. copy_(to|from)_user)
333
334	lr      r3, [ecr]
335	btst_s  r3, ECR_C_BIT_DTLB_LD_MISS	; Read Access
336	or.nz   r2, r2, _PAGE_READ      	; chk for Read flag in PTE
337	btst_s  r3, ECR_C_BIT_DTLB_ST_MISS	; Write Access
338	or.nz   r2, r2, _PAGE_WRITE     	; chk for Write flag in PTE
339	; Above laddering takes care of XCHG access (both R and W)
340
341	; By now, r2 setup with all the Flags we need to check in PTE
342	and     r3, r0, r2              ; Mask out NON Flag bits from PTE
343	brne.d  r3, r2, do_slow_path_pf ; is ((pte & flags_test) == flags_test)
344
345	;----------------------------------------------------------------
346	; UPDATE_PTE: Let Linux VM know that page was accessed/dirty
347	or      r0, r0, _PAGE_ACCESSED        ; Accessed bit always
348	or.nz   r0, r0, _PAGE_DIRTY           ; if Write, set Dirty bit as well
349	st_s    r0, [r1]                      ; Write back PTE
350
351	CONV_PTE_TO_TLB
352
353	COMMIT_ENTRY_TO_MMU
354	TLBMISS_RESTORE_REGS
355EV_TLBMissD_fast_ret:	; additional label for VDK OS-kit instrumentation
356	rtie
357
358;-------- Common routine to call Linux Page Fault Handler -----------
359do_slow_path_pf:
360
361#ifdef CONFIG_ISA_ARCV2
362	; Set Z flag if exception in U mode. Hardware micro-ops do this on any
363	; taken interrupt/exception, and thus is already the case at the entry
364	; above, but ensuing code would have already clobbered.
365	; EXCEPTION_PROLOGUE called in slow path, relies on correct Z flag set
366
367	lr	r2, [erstatus]
368	and	r2, r2, STATUS_U_MASK
369	bxor.f	0, r2, STATUS_U_BIT
370#endif
371
372	; Restore the 4-scratch regs saved by fast path miss handler
373	TLBMISS_RESTORE_REGS
374
375	; Slow path TLB Miss handled as a regular ARC Exception
376	; (stack switching / save the complete reg-file).
377	b  call_do_page_fault
378END(EV_TLBMissD)
379