Boot Linux faster!

Check our new training course

Boot Linux faster!

Check our new training course
and Creative Commons CC-BY-SA
lecture and lab materials

Bootlin logo

Elixir Cross Referencer

  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
/*
 * Copyright (c) 2013-2014 Wind River Systems, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @file
 * @brief ARM atomic operations library
 *
 * This library provides routines to perform a number of atomic operations
 * on a memory location: add, subtract, increment, decrement, bitwise OR,
 * bitwise NOR, bitwise AND, bitwise NAND, set, clear and compare-and-swap.
 */

#define _ASMLANGUAGE

#include <toolchain.h>
#include <sections.h>

_ASM_FILE_PROLOGUE

/* exports */

GTEXT(atomic_set)
GTEXT(atomic_get)
GTEXT(atomic_add)
GTEXT(atomic_nand)
GTEXT(atomic_and)
GTEXT(atomic_or)
GTEXT(atomic_xor)
GTEXT(atomic_clear)
GTEXT(atomic_dec)
GTEXT(atomic_inc)
GTEXT(atomic_sub)
GTEXT(atomic_cas)

/**
 *
 * @brief Atomically clear a memory location
 *
 * This routine atomically clears the contents of <target> and returns the old
 * value that was in <target>.
 *
 * This routine can be used from both task and interrupt level.
 *
 * @return Contents of <target> before the atomic operation
 *
 * ERRNO: N/A
 *
 * atomic_val_t atomic_clear
 *    (
 *    atomic_t *target	/@ memory location to clear @/
 *    )
 */

SECTION_SUBSEC_FUNC(TEXT, atomic_clear_set, atomic_clear)
	MOV	r1, #0
	/* fall through into atomic_set */

/**
 *
 * @brief Atomically set a memory location
 *
 * This routine atomically sets the contents of <target> to <value> and returns
 * the old value that was in <target>.
 *
 * This routine can be used from both task and interrupt level.
 *
 * @return Contents of <target> before the atomic operation
 *
 * ERRNO: N/A
 *
 * atomic_val_t atomic_set
 *    (
 *    atomic_t *target,	/@ memory location to set @/
 *    atomic_val_t value	/@ set with this value @/
 *    )
 *
 */

SECTION_SUBSEC_FUNC(TEXT, atomic_clear_set, atomic_set)

	LDREX	r2, [r0]	/* load old value and mark exclusive access */
	STREX	r12, r1, [r0]	/* try to store new value */
	TEQ	r12, #0		/* store successful? */

	BNE	atomic_set	/* if not, retry */

	MOV	r0, r2		/* return old value */
	MOV	pc, lr

/**
 *
 * @brief Get the value of a shared memory atomically
 *
 * This routine atomically retrieves the value in *target
 *
 * long atomic_get
 *     (
 *     atomic_t * target    /@ address of atom to be retrieved @/
 *     )
 *
 * RETURN: value read from address target.
 *
 */

SECTION_FUNC(TEXT, atomic_get)
	LDR	r0, [r0]
	MOV	pc, lr

/**
 *
 * @brief Atomically increment a memory location
 *
 * This routine atomically increments the value in <target>.  The operation is
 * done using unsigned integer arithmetic.  Various CPU architectures may impose
 * restrictions with regards to the alignment and cache attributes of the
 * atomic_t type.
 *
 * This routine can be used from both task and interrupt level.
 *
 * @return Contents of <target> before the atomic operation
 *
 * ERRNO: N/A
 *
 * atomic_val_t atomic_inc
 *    (
 *    atomic_t *target,	/@ memory location to increment @/
 *    )
 *
 */

SECTION_SUBSEC_FUNC(TEXT, atomic_inc_add, atomic_inc)
	MOV	r1, #1
	/* fall through into atomic_add */

/**
 *
 * @brief Atomically add a value to a memory location
 *
 * This routine atomically adds the contents of <target> and <value>, placing
 * the result in <target>. The operation is done using signed integer arithmetic.
 * Various CPU architectures may impose restrictions with regards to the
 * alignment and cache attributes of the atomic_t type.
 *
 * This routine can be used from both task and interrupt level.
 *
 * @return Contents of <target> before the atomic operation
 *
 * ERRNO: N/A
 *
 * atomic_val_t atomic_add
 *    (
 *    atomic_t *target,	/@ memory location to add to @/
 *    atomic_val_t value	/@ value to add @/
 *    )
 */

SECTION_SUBSEC_FUNC(TEXT, atomic_inc_add, atomic_add)

	LDREX	r2, [r0]	/* load old value and mark exclusive access */
	ADD	r3, r2, r1	/* add word */
	STREX	r12, r3, [r0]	/* try to store new value */
	TEQ	r12, #0		/* store successful? */

	BNE	atomic_add	/* if not, retry */

	MOV	r0, r2		/* return old value */
	MOV	pc, lr

/**
 *
 * @brief Atomically decrement a memory location
 *
 * This routine atomically decrements the value in <target>.  The operation is
 * done using unsigned integer arithmetic.  Various CPU architectures may impose
 * restrictions with regards to the alignment and cache attributes of the
 * atomic_t type.
 *
 * This routine can be used from both task and interrupt level.
 *
 * @return Contents of <target> before the atomic operation
 *
 * ERRNO: N/A
 *
 * atomic_val_t atomic_dec
 *    (
 *    atomic_t *target,	/@ memory location to decrement @/
 *    )
 *
 */

SECTION_SUBSEC_FUNC(TEXT, atomic_decSub, atomic_dec)
	MOV   r1, #1
	/* fall through into atomic_sub */

/**
 *
 * @brief Atomically subtract a value from a memory location
 *
 * This routine atomically subtracts <value> from the contents of <target>,
 * placing the result in <target>.  The operation is done using signed integer
 * arithmetic. Various CPU architectures may impose restrictions with regards to
 * the alignment and cache attributes of the atomic_t type.
 *
 * This routine can be used from both task and interrupt level.
 *
 * @return Contents of <target> before the atomic operation
 *
 * ERRNO: N/A
 *
 * atomic_val_t atomic_sub
 *    (
 *    atomic_t *target,	/@ memory location to subtract from @/
 *    atomic_val_t value	/@ value to subtract @/
 *    )
 *
 */

SECTION_SUBSEC_FUNC(TEXT, atomic_decSub, atomic_sub)

	LDREX	r2, [r0]	/* load old value and mark exclusive access */
	SUB	r3, r2, r1	/* subtract word */
	STREX	r12, r3, [r0]	/* try to store new value */
	TEQ	r12, #0		/* store successful? */
	BNE	atomic_sub	/* if not, retry */

	MOV	r0, r2		/* return old value */
	MOV	pc, lr

/**
 *
 * @brief Atomically perform a bitwise NAND on a memory location
 *
 * This routine atomically performs a bitwise NAND operation of the contents of
 * <target> and <value>, placing the result in <target>.
 * Various CPU architectures may impose restrictions with regards to the
 * alignment and cache attributes of the atomic_t type.
 *
 * This routine can be used from both task and interrupt level.
 *
 * @return Contents of <target> before the atomic operation
 *
 * ERRNO: N/A
 *
 * atomic_val_t atomic_nand
 *    (
 *    atomic_t *target,	/@ memory location to NAND @/
 *    atomic_val_t value	/@ NAND with this value @/
 *    )
 *
 */

SECTION_FUNC(TEXT, atomic_nand)

	LDREX	r2, [r0]	/* load old value and mark exclusive access */
	AND	r3, r2, r1	/* AND word */
	MVN	r3, r3		/* invert */
	STREX	r12, r3, [r0]	/* try to store new value */
	TEQ	r12, #0		/* store successful? */
	BNE	atomic_nand	/* if not, retry */

	MOV	r0, r2		/* return old value */
	MOV	pc, lr

/**
 *
 * @brief Atomically perform a bitwise AND on a memory location
 *
 * This routine atomically performs a bitwise AND operation of the contents of
 * <target> and <value>, placing the result in <target>.
 * Various CPU architectures may impose restrictions with regards to the
 * alignment and cache attributes of the atomic_t type.
 *
 * This routine can be used from both task and interrupt level.
 *
 * @return Contents of <target> before the atomic operation
 *
 * ERRNO: N/A
 *
 * atomic_val_t atomic_and
 *    (
 *    atomic_t *target,	/@ memory location to AND @/
 *    atomic_val_t value	/@ AND with this value @/
 *    )
 *
 */

SECTION_FUNC(TEXT, atomic_and)

	LDREX	r2, [r0]	/* load old value and mark exclusive access */
	AND	r3, r2, r1	/* AND word */
	STREX	r12, r3, [r0]	/* try to store new value */
	TEQ	r12, #0		/* store successful? */
	BNE	atomic_and	/* if not, retry */

	MOV	r0, r2		/* return old value */
	MOV	pc, lr

/**
 *
 * @brief Atomically perform a bitwise OR on memory location
 *
 * This routine atomically performs a bitwise OR operation of the contents of
 * <target> and <value>, placing the result in <target>.
 * Various CPU architectures may impose restrictions with regards to the
 * alignment and cache attributes of the atomic_t type.
 *
 * This routine can be used from both task and interrupt level.
 *
 * @return Contents of <target> before the atomic operation
 *
 * ERRNO: N/A
 *
 * atomic_val_t atomic_or
 *    (
 *    atomic_t *target,	/@ memory location to OR @/
 *    atomic_val_t value	/@ OR with this value @/
 *    )
 *
 */

SECTION_FUNC(TEXT, atomic_or)

	LDREX	r2, [r0]	/* load old value and mark exclusive access */
	ORR	r3, r2, r1	/* OR word */
	STREX	r12, r3, [r0]	/* try to store new value */
	TEQ	r12, #0		/* store successful? */
	BNE	atomic_or	/* if not, retry */

	MOV	r0, r2		/* return old value */
	MOV	pc, lr

/**
 *
 * @brief Atomically perform a bitwise XOR on a memory location
 *
 * This routine atomically performs a bitwise XOR operation of the contents of
 * <target> and <value>, placing the result in <target>.
 * Various CPU architectures may impose restrictions with regards to the
 * alignment and cache attributes of the atomic_t type.
 *
 * This routine can be used from both task and interrupt level.
 *
 * @return Contents of <target> before the atomic operation
 *
 * ERRNO: N/A
 *
 * atomic_val_t atomic_xor
 *    (
 *    atomic_t *target,	/@ memory location to XOR @/
 *    atomic_val_t value	/@ XOR with this value @/
 *    )
 *
 */

SECTION_FUNC(TEXT, atomic_xor)

	LDREX	r2, [r0]	/* load old value and mark exclusive access */
	EOR	r3, r2, r1	/* XOR word */
	STREX	r12, r3, [r0]	/* try to store new value */
	TEQ	r12, #0		/* store successful? */
	BNE	atomic_xor	/* if not, retry */

	MOV	r0, r2		/* return old value */
	MOV	pc, lr

/**
 *
 * @brief Atomically compare-and-swap the contents of a memory location
 *
 * This routine performs an atomic compare-and-swap. testing that the contents of
 * <target> contains <oldValue>, and if it does, setting the value of <target>
 * to <newValue>. Various CPU architectures may impose restrictions with regards
 * to the alignment and cache attributes of the atomic_t type.
 *
 * This routine can be used from both task and interrupt level.
 *
 * @return 1 if the swap is actually executed, 0 otherwise.
 *
 * ERRNO: N/A
 *
 * int atomic_cas
 *    (
 *    atomic_t *target,	        /@ memory location to compare-and-swap @/
 *    atomic_val_t oldValue,	/@ compare to this value @/
 *    atomic_val_t newValue,	/@ swap with this value @/
 *    )
 *
 */

SECTION_FUNC(TEXT, atomic_cas)

	LDREX	r3, [r0]	/* load the value and mark exclusive access */
	CMP	r3, r1		/* if (*target != oldValue) */
	ITT NE
	    MOVNE	r0, #0		/*     return FALSE */
	    MOVNE	pc, lr
	STREX	r12, r2, [r0]	/* try to store if equal */
	TEQ	r12, #0		/* store successful? */
	BNE	atomic_cas	/* if not, retry */

	MOV	r0, #1		/* return TRUE if swap occurred */
	MOV	pc, lr