aboutsummaryrefslogtreecommitdiffstats
path: root/arch/xtensa/kernel/align.S
blob: 890004af03a927fb8768a4d3e7878ccd3c6a1ddf (plain) (blame)
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
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
/*
 * arch/xtensa/kernel/align.S
 *
 * Handle unalignment exceptions in kernel space.
 *
 * This file is subject to the terms and conditions of the GNU General
 * Public License.  See the file "COPYING" in the main directory of
 * this archive for more details.
 *
 * Copyright (C) 2001 - 2005 Tensilica, Inc.
 * Copyright (C) 2014 Cadence Design Systems Inc.
 *
 * Rewritten by Chris Zankel <chris@zankel.net>
 *
 * Based on work from Joe Taylor <joe@tensilica.com, joetylr@yahoo.com>
 * and Marc Gauthier <marc@tensilica.com, marc@alimni.uwaterloo.ca>
 */

#include <linux/linkage.h>
#include <asm/current.h>
#include <asm/asm-offsets.h>
#include <asm/processor.h>

#if XCHAL_UNALIGNED_LOAD_EXCEPTION || XCHAL_UNALIGNED_STORE_EXCEPTION

/*  First-level exception handler for unaligned exceptions.
 *
 *  Note: This handler works only for kernel exceptions.  Unaligned user
 *        access should get a seg fault.
 */

/* Big and little endian 16-bit values are located in
 * different halves of a register.  HWORD_START helps to
 * abstract the notion of extracting a 16-bit value from a
 * register.
 * We also have to define new shifting instructions because
 * lsb and msb are on 'opposite' ends in a register for
 * different endian machines.
 *
 * Assume a memory region in ascending address:
 *   	0 1 2 3|4 5 6 7
 *
 * When loading one word into a register, the content of that register is:
 *  LE	3 2 1 0, 7 6 5 4
 *  BE  0 1 2 3, 4 5 6 7
 *
 * Masking the bits of the higher/lower address means:
 *  LE  X X 0 0, 0 0 X X
 *  BE	0 0 X X, X X 0 0
 *
 * Shifting to higher/lower addresses, means:
 *  LE  shift left / shift right
 *  BE  shift right / shift left
 *
 * Extracting 16 bits from a 32 bit reg. value to higher/lower address means:
 *  LE  mask 0 0 X X / shift left
 *  BE  shift left / mask 0 0 X X
 */

#define UNALIGNED_USER_EXCEPTION

#if XCHAL_HAVE_BE

#define HWORD_START	16
#define	INSN_OP0	28
#define	INSN_T		24
#define	INSN_OP1	16

.macro __src_b	r, w0, w1;	src	\r, \w0, \w1;	.endm
.macro __ssa8	r;		ssa8b	\r;		.endm
.macro __ssa8r	r;		ssa8l	\r;		.endm
.macro __sh	r, s;		srl	\r, \s;		.endm
.macro __sl	r, s;		sll	\r, \s;		.endm
.macro __exth	r, s;		extui	\r, \s, 0, 16;	.endm
.macro __extl	r, s;		slli	\r, \s, 16;	.endm

#else

#define HWORD_START	0
#define	INSN_OP0	0
#define	INSN_T		4
#define	INSN_OP1	12

.macro __src_b	r, w0, w1;	src	\r, \w1, \w0;	.endm
.macro __ssa8	r;		ssa8l	\r;		.endm
.macro __ssa8r	r;		ssa8b	\r;		.endm
.macro __sh	r, s;		sll	\r, \s;		.endm
.macro __sl	r, s;		srl	\r, \s;		.endm
.macro __exth	r, s;		slli	\r, \s, 16;	.endm
.macro __extl	r, s;		extui	\r, \s, 0, 16;	.endm

#endif

/*
 *	xxxx xxxx = imm8 field
 *	     yyyy = imm4 field
 *	     ssss = s field
 *	     tttt = t field
 *
 *	       		 16		    0
 *		          -------------------
 *	L32I.N		  yyyy ssss tttt 1000
 *	S32I.N	          yyyy ssss tttt 1001
 *
 *	       23			    0
 *		-----------------------------
 *	res	          0000           0010
 *	L16UI	xxxx xxxx 0001 ssss tttt 0010
 *	L32I	xxxx xxxx 0010 ssss tttt 0010
 *	XXX	          0011 ssss tttt 0010
 *	XXX	          0100 ssss tttt 0010
 *	S16I	xxxx xxxx 0101 ssss tttt 0010
 *	S32I	xxxx xxxx 0110 ssss tttt 0010
 *	XXX	          0111 ssss tttt 0010
 *	XXX	          1000 ssss tttt 0010
 *	L16SI	xxxx xxxx 1001 ssss tttt 0010
 *	XXX	          1010           0010
 *      **L32AI	xxxx xxxx 1011 ssss tttt 0010 unsupported
 *	XXX	          1100           0010
 *	XXX	          1101           0010
 *	XXX	          1110           0010
 *	**S32RI	xxxx xxxx 1111 ssss tttt 0010 unsupported
 *		-----------------------------
 *                           ^         ^    ^
 *    sub-opcode (NIBBLE_R) -+         |    |
 *       t field (NIBBLE_T) -----------+    |
 *  major opcode (NIBBLE_OP0) --------------+
 */

#define OP0_L32I_N	0x8		/* load immediate narrow */
#define OP0_S32I_N	0x9		/* store immediate narrow */
#define OP1_SI_MASK	0x4		/* OP1 bit set for stores */
#define OP1_SI_BIT	2		/* OP1 bit number for stores */

#define OP1_L32I	0x2
#define OP1_L16UI	0x1
#define OP1_L16SI	0x9
#define OP1_L32AI	0xb

#define OP1_S32I	0x6
#define OP1_S16I	0x5
#define OP1_S32RI	0xf

/*
 * Entry condition:
 *
 *   a0:	trashed, original value saved on stack (PT_AREG0)
 *   a1:	a1
 *   a2:	new stack pointer, original in DEPC
 *   a3:	a3
 *   depc:	a2, original value saved on stack (PT_DEPC)
 *   excsave_1:	dispatch table
 *
 *   PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
 *	     <  VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
 */


ENTRY(fast_unaligned)

	/* Note: We don't expect the address to be aligned on a word
	 *       boundary. After all, the processor generated that exception
	 *       and it would be a hardware fault.
	 */

	/* Save some working register */

	s32i	a4, a2, PT_AREG4
	s32i	a5, a2, PT_AREG5
	s32i	a6, a2, PT_AREG6
	s32i	a7, a2, PT_AREG7
	s32i	a8, a2, PT_AREG8

	rsr	a0, depc
	s32i	a0, a2, PT_AREG2
	s32i	a3, a2, PT_AREG3

	rsr	a3, excsave1
	movi	a4, fast_unaligned_fixup
	s32i	a4, a3, EXC_TABLE_FIXUP

	/* Keep value of SAR in a0 */

	rsr	a0, sar
	rsr	a8, excvaddr		# load unaligned memory address

	/* Now, identify one of the following load/store instructions.
	 *
	 * The only possible danger of a double exception on the
	 * following l32i instructions is kernel code in vmalloc
	 * memory. The processor was just executing at the EPC_1
	 * address, and indeed, already fetched the instruction.  That
	 * guarantees a TLB mapping, which hasn't been replaced by
	 * this unaligned exception handler that uses only static TLB
	 * mappings. However, high-level interrupt handlers might
	 * modify TLB entries, so for the generic case, we register a
	 * TABLE_FIXUP handler here, too.
	 */

	/* a3...a6 saved on stack, a2 = SP */

	/* Extract the instruction that caused the unaligned access. */

	rsr	a7, epc1	# load exception address
	movi	a3, ~3
	and	a3, a3, a7	# mask lower bits

	l32i	a4, a3, 0	# load 2 words
	l32i	a5, a3, 4

	__ssa8	a7
	__src_b	a4, a4, a5	# a4 has the instruction

	/* Analyze the instruction (load or store?). */

	extui	a5, a4, INSN_OP0, 4	# get insn.op0 nibble

#if XCHAL_HAVE_DENSITY
	_beqi	a5, OP0_L32I_N, .Lload	# L32I.N, jump
	addi	a6, a5, -OP0_S32I_N
	_beqz	a6, .Lstore		# S32I.N, do a store
#endif
	/* 'store indicator bit' not set, jump */
	_bbci.l	a4, OP1_SI_BIT + INSN_OP1, .Lload

	/* Store: Jump to table entry to get the value in the source register.*/

.Lstore:movi	a5, .Lstore_table	# table
	extui	a6, a4, INSN_T, 4	# get source register
	addx8	a5, a6, a5
	jx	a5			# jump into table

	/* Load: Load memory address. */

.Lload: movi	a3, ~3
	and	a3, a3, a8		# align memory address

	__ssa8	a8
#ifdef UNALIGNED_USER_EXCEPTION
	addi	a3, a3, 8
	l32e	a5, a3, -8
	l32e	a6, a3, -4
#else
	l32i	a5, a3, 0
	l32i	a6, a3, 4
#endif
	__src_b	a3, a5, a6		# a3 has the data word

#if XCHAL_HAVE_DENSITY
	addi	a7, a7, 2		# increment PC (assume 16-bit insn)

	extui	a5, a4, INSN_OP0, 4
	_beqi	a5, OP0_L32I_N, 1f	# l32i.n: jump

	addi	a7, a7, 1
#else
	addi	a7, a7, 3
#endif

	extui	a5, a4, INSN_OP1, 4
	_beqi	a5, OP1_L32I, 1f	# l32i: jump

	extui	a3, a3, 0, 16		# extract lower 16 bits
	_beqi	a5, OP1_L16UI, 1f
	addi	a5, a5, -OP1_L16SI
	_bnez	a5, .Linvalid_instruction_load

	/* sign extend value */

	slli	a3, a3, 16
	srai	a3, a3, 16

	/* Set target register. */

1:
	extui	a4, a4, INSN_T, 4	# extract target register
	movi	a5, .Lload_table
	addx8	a4, a4, a5
	jx	a4			# jump to entry for target register

	.align	8
.Lload_table:
	s32i	a3, a2, PT_AREG0;	_j .Lexit;	.align 8
	mov	a1, a3;			_j .Lexit;	.align 8 # fishy??
	s32i	a3, a2, PT_AREG2;	_j .Lexit;	.align 8
	s32i	a3, a2, PT_AREG3;	_j .Lexit;	.align 8
	s32i	a3, a2, PT_AREG4;	_j .Lexit;	.align 8
	s32i	a3, a2, PT_AREG5;	_j .Lexit;	.align 8
	s32i	a3, a2, PT_AREG6;	_j .Lexit;	.align 8
	s32i	a3, a2, PT_AREG7;	_j .Lexit;	.align 8
	s32i	a3, a2, PT_AREG8;	_j .Lexit;	.align 8
	mov	a9, a3		;	_j .Lexit;	.align 8
	mov	a10, a3		;	_j .Lexit;	.align 8
	mov	a11, a3		;	_j .Lexit;	.align 8
	mov	a12, a3		;	_j .Lexit;	.align 8
	mov	a13, a3		;	_j .Lexit;	.align 8
	mov	a14, a3		;	_j .Lexit;	.align 8
	mov	a15, a3		;	_j .Lexit;	.align 8

.Lstore_table:
	l32i	a3, a2, PT_AREG0;	_j 1f;	.align 8
	mov	a3, a1;			_j 1f;	.align 8	# fishy??
	l32i	a3, a2, PT_AREG2;	_j 1f;	.align 8
	l32i	a3, a2, PT_AREG3;	_j 1f;	.align 8
	l32i	a3, a2, PT_AREG4;	_j 1f;	.align 8
	l32i	a3, a2, PT_AREG5;	_j 1f;	.align 8
	l32i	a3, a2, PT_AREG6;	_j 1f;	.align 8
	l32i	a3, a2, PT_AREG7;	_j 1f;	.align 8
	l32i	a3, a2, PT_AREG8;	_j 1f;	.align 8
	mov	a3, a9		;	_j 1f;	.align 8
	mov	a3, a10		;	_j 1f;	.align 8
	mov	a3, a11		;	_j 1f;	.align 8
	mov	a3, a12		;	_j 1f;	.align 8
	mov	a3, a13		;	_j 1f;	.align 8
	mov	a3, a14		;	_j 1f;	.align 8
	mov	a3, a15		;	_j 1f;	.align 8

	/* We cannot handle this exception. */

	.extern _kernel_exception
.Linvalid_instruction_load:
.Linvalid_instruction_store:

	movi	a4, 0
	rsr	a3, excsave1
	s32i	a4, a3, EXC_TABLE_FIXUP

	/* Restore a4...a8 and SAR, set SP, and jump to default exception. */

	l32i	a8, a2, PT_AREG8
	l32i	a7, a2, PT_AREG7
	l32i	a6, a2, PT_AREG6
	l32i	a5, a2, PT_AREG5
	l32i	a4, a2, PT_AREG4
	wsr	a0, sar
	mov	a1, a2

	rsr	a0, ps
	bbsi.l  a0, PS_UM_BIT, 2f     # jump if user mode

	movi	a0, _kernel_exception
	jx	a0

2:	movi	a0, _user_exception
	jx	a0

1: 	# a7: instruction pointer, a4: instruction, a3: value

	movi	a6, 0			# mask: ffffffff:00000000

#if XCHAL_HAVE_DENSITY
	addi	a7, a7, 2		# incr. PC,assume 16-bit instruction

	extui	a5, a4, INSN_OP0, 4	# extract OP0
	addi	a5, a5, -OP0_S32I_N
	_beqz	a5, 1f			# s32i.n: jump

	addi	a7, a7, 1		# increment PC, 32-bit instruction
#else
	addi	a7, a7, 3		# increment PC, 32-bit instruction
#endif

	extui	a5, a4, INSN_OP1, 4	# extract OP1
	_beqi	a5, OP1_S32I, 1f	# jump if 32 bit store
	_bnei	a5, OP1_S16I, .Linvalid_instruction_store

	movi	a5, -1
	__extl	a3, a3			# get 16-bit value
	__exth	a6, a5			# get 16-bit mask ffffffff:ffff0000

	/* Get memory address */

1:
	movi	a4, ~3
	and	a4, a4, a8		# align memory address

	/* Insert value into memory */

	movi	a5, -1			# mask: ffffffff:XXXX0000
#ifdef UNALIGNED_USER_EXCEPTION
	addi	a4, a4, 8
#endif

	__ssa8r a8
	__src_b	a8, a5, a6		# lo-mask  F..F0..0 (BE) 0..0F..F (LE)
	__src_b	a6, a6, a5		# hi-mask  0..0F..F (BE) F..F0..0 (LE)
#ifdef UNALIGNED_USER_EXCEPTION
	l32e	a5, a4, -8
#else
	l32i	a5, a4, 0		# load lower address word
#endif
	and	a5, a5, a8		# mask
	__sh	a8, a3 			# shift value
	or	a5, a5, a8		# or with original value
#ifdef UNALIGNED_USER_EXCEPTION
	s32e	a5, a4, -8
	l32e	a8, a4, -4
#else
	s32i	a5, a4, 0		# store
	l32i	a8, a4, 4		# same for upper address word
#endif
	__sl	a5, a3
	and	a6, a8, a6
	or	a6, a6, a5
#ifdef UNALIGNED_USER_EXCEPTION
	s32e	a6, a4, -4
#else
	s32i	a6, a4, 4
#endif

.Lexit:
#if XCHAL_HAVE_LOOPS
	rsr	a4, lend		# check if we reached LEND
	bne	a7, a4, 1f
	rsr	a4, lcount		# and LCOUNT != 0
	beqz	a4, 1f
	addi	a4, a4, -1		# decrement LCOUNT and set
	rsr	a7, lbeg		# set PC to LBEGIN
	wsr	a4, lcount
#endif

1:	wsr	a7, epc1		# skip emulated instruction

	/* Update icount if we're single-stepping in userspace. */
	rsr	a4, icountlevel
	beqz	a4, 1f
	bgeui	a4, LOCKLEVEL + 1, 1f
	rsr	a4, icount
	addi	a4, a4, 1
	wsr	a4, icount
1:
	movi	a4, 0
	rsr	a3, excsave1
	s32i	a4, a3, EXC_TABLE_FIXUP

	/* Restore working register */

	l32i	a8, a2, PT_AREG8
	l32i	a7, a2, PT_AREG7
	l32i	a6, a2, PT_AREG6
	l32i	a5, a2, PT_AREG5
	l32i	a4, a2, PT_AREG4
	l32i	a3, a2, PT_AREG3

	/* restore SAR and return */

	wsr	a0, sar
	l32i	a0, a2, PT_AREG0
	l32i	a2, a2, PT_AREG2
	rfe

ENDPROC(fast_unaligned)

ENTRY(fast_unaligned_fixup)

	l32i	a2, a3, EXC_TABLE_DOUBLE_SAVE
	wsr	a3, excsave1

	l32i	a8, a2, PT_AREG8
	l32i	a7, a2, PT_AREG7
	l32i	a6, a2, PT_AREG6
	l32i	a5, a2, PT_AREG5
	l32i	a4, a2, PT_AREG4
	l32i	a0, a2, PT_AREG2
	xsr	a0, depc			# restore depc and a0
	wsr	a0, sar

	rsr	a0, exccause
	s32i	a0, a2, PT_DEPC			# mark as a regular exception

	rsr	a0, ps
	bbsi.l  a0, PS_UM_BIT, 1f		# jump if user mode

	rsr	a0, exccause
	addx4	a0, a0, a3              	# find entry in table
	l32i	a0, a0, EXC_TABLE_FAST_KERNEL   # load handler
	l32i	a3, a2, PT_AREG3
	jx	a0
1:
	rsr	a0, exccause
	addx4	a0, a0, a3              	# find entry in table
	l32i	a0, a0, EXC_TABLE_FAST_USER     # load handler
	l32i	a3, a2, PT_AREG3
	jx	a0

ENDPROC(fast_unaligned_fixup)

#endif /* XCHAL_UNALIGNED_LOAD_EXCEPTION || XCHAL_UNALIGNED_STORE_EXCEPTION */