1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_X86_BITOPS_H
3 #define _ASM_X86_BITOPS_H
6 * Copyright 1992, Linus Torvalds.
8 * Note: inlines with more than a single statement should be marked
9 * __always_inline to avoid problems with older gcc's inlining heuristics.
12 #ifndef _LINUX_BITOPS_H
13 #error only <linux/bitops.h> can be included directly
16 #include <linux/compiler.h>
17 #include <asm/alternative.h>
18 #include <asm/rmwcc.h>
19 #include <asm/barrier.h>
21 #if BITS_PER_LONG == 32
22 # define _BITOPS_LONG_SHIFT 5
23 #elif BITS_PER_LONG == 64
24 # define _BITOPS_LONG_SHIFT 6
26 # error "Unexpected BITS_PER_LONG"
29 #define BIT_64(n) (U64_C(1) << (n))
32 * These have to be done with inline assembly: that way the bit-setting
33 * is guaranteed to be atomic. All bit operations return 0 if the bit
34 * was cleared before the operation and != 0 if it was not.
36 * bit 0 is the LSB of addr; bit 32 is the LSB of (addr+1).
39 #define RLONG_ADDR(x) "m" (*(volatile long *) (x))
40 #define WBYTE_ADDR(x) "+m" (*(volatile char *) (x))
42 #define ADDR RLONG_ADDR(addr)
45 * We do the locked ops that don't return the old value as
46 * a mask operation on a byte.
48 #define IS_IMMEDIATE(nr) (__builtin_constant_p(nr))
49 #define CONST_MASK_ADDR(nr, addr) WBYTE_ADDR((void *)(addr) + ((nr)>>3))
50 #define CONST_MASK(nr) (1 << ((nr) & 7))
53 * set_bit - Atomically set a bit in memory
55 * @addr: the address to start counting from
57 * This function is atomic and may not be reordered. See __set_bit()
58 * if you do not require the atomic guarantees.
60 * Note: there are no guarantees that this function will not be reordered
61 * on non x86 architectures, so if you are writing portable code,
62 * make sure not to rely on its reordering guarantees.
64 * Note that @nr may be almost arbitrarily large; this function is not
65 * restricted to acting on a single-word quantity.
67 static __always_inline
void
68 set_bit(long nr
, volatile unsigned long *addr
)
70 if (IS_IMMEDIATE(nr
)) {
71 asm volatile(LOCK_PREFIX
"orb %1,%0"
72 : CONST_MASK_ADDR(nr
, addr
)
73 : "iq" ((u8
)CONST_MASK(nr
))
76 asm volatile(LOCK_PREFIX
__ASM_SIZE(bts
) " %1,%0"
77 : : RLONG_ADDR(addr
), "Ir" (nr
) : "memory");
82 * __set_bit - Set a bit in memory
84 * @addr: the address to start counting from
86 * Unlike set_bit(), this function is non-atomic and may be reordered.
87 * If it's called on the same region of memory simultaneously, the effect
88 * may be that only one operation succeeds.
90 static __always_inline
void __set_bit(long nr
, volatile unsigned long *addr
)
92 asm volatile(__ASM_SIZE(bts
) " %1,%0" : : ADDR
, "Ir" (nr
) : "memory");
96 * clear_bit - Clears a bit in memory
98 * @addr: Address to start counting from
100 * clear_bit() is atomic and may not be reordered. However, it does
101 * not contain a memory barrier, so if it is used for locking purposes,
102 * you should call smp_mb__before_atomic() and/or smp_mb__after_atomic()
103 * in order to ensure changes are visible on other processors.
105 static __always_inline
void
106 clear_bit(long nr
, volatile unsigned long *addr
)
108 if (IS_IMMEDIATE(nr
)) {
109 asm volatile(LOCK_PREFIX
"andb %1,%0"
110 : CONST_MASK_ADDR(nr
, addr
)
111 : "iq" ((u8
)~CONST_MASK(nr
)));
113 asm volatile(LOCK_PREFIX
__ASM_SIZE(btr
) " %1,%0"
114 : : RLONG_ADDR(addr
), "Ir" (nr
) : "memory");
119 * clear_bit_unlock - Clears a bit in memory
121 * @addr: Address to start counting from
123 * clear_bit() is atomic and implies release semantics before the memory
124 * operation. It can be used for an unlock.
126 static __always_inline
void clear_bit_unlock(long nr
, volatile unsigned long *addr
)
132 static __always_inline
void __clear_bit(long nr
, volatile unsigned long *addr
)
134 asm volatile(__ASM_SIZE(btr
) " %1,%0" : : ADDR
, "Ir" (nr
) : "memory");
137 static __always_inline
bool clear_bit_unlock_is_negative_byte(long nr
, volatile unsigned long *addr
)
140 asm volatile(LOCK_PREFIX
"andb %2,%1"
142 : CC_OUT(s
) (negative
), WBYTE_ADDR(addr
)
143 : "ir" ((char) ~(1 << nr
)) : "memory");
147 // Let everybody know we have it
148 #define clear_bit_unlock_is_negative_byte clear_bit_unlock_is_negative_byte
151 * __clear_bit_unlock - Clears a bit in memory
153 * @addr: Address to start counting from
155 * __clear_bit() is non-atomic and implies release semantics before the memory
156 * operation. It can be used for an unlock if no other CPUs can concurrently
157 * modify other bits in the word.
159 static __always_inline
void __clear_bit_unlock(long nr
, volatile unsigned long *addr
)
161 __clear_bit(nr
, addr
);
165 * __change_bit - Toggle a bit in memory
166 * @nr: the bit to change
167 * @addr: the address to start counting from
169 * Unlike change_bit(), this function is non-atomic and may be reordered.
170 * If it's called on the same region of memory simultaneously, the effect
171 * may be that only one operation succeeds.
173 static __always_inline
void __change_bit(long nr
, volatile unsigned long *addr
)
175 asm volatile(__ASM_SIZE(btc
) " %1,%0" : : ADDR
, "Ir" (nr
) : "memory");
179 * change_bit - Toggle a bit in memory
181 * @addr: Address to start counting from
183 * change_bit() is atomic and may not be reordered.
184 * Note that @nr may be almost arbitrarily large; this function is not
185 * restricted to acting on a single-word quantity.
187 static __always_inline
void change_bit(long nr
, volatile unsigned long *addr
)
189 if (IS_IMMEDIATE(nr
)) {
190 asm volatile(LOCK_PREFIX
"xorb %1,%0"
191 : CONST_MASK_ADDR(nr
, addr
)
192 : "iq" ((u8
)CONST_MASK(nr
)));
194 asm volatile(LOCK_PREFIX
__ASM_SIZE(btc
) " %1,%0"
195 : : RLONG_ADDR(addr
), "Ir" (nr
) : "memory");
200 * test_and_set_bit - Set a bit and return its old value
202 * @addr: Address to count from
204 * This operation is atomic and cannot be reordered.
205 * It also implies a memory barrier.
207 static __always_inline
bool test_and_set_bit(long nr
, volatile unsigned long *addr
)
209 GEN_BINARY_RMWcc(LOCK_PREFIX
__ASM_SIZE(bts
),
210 *addr
, "Ir", nr
, "%0", c
);
214 * test_and_set_bit_lock - Set a bit and return its old value for lock
216 * @addr: Address to count from
218 * This is the same as test_and_set_bit on x86.
220 static __always_inline
bool
221 test_and_set_bit_lock(long nr
, volatile unsigned long *addr
)
223 return test_and_set_bit(nr
, addr
);
227 * __test_and_set_bit - Set a bit and return its old value
229 * @addr: Address to count from
231 * This operation is non-atomic and can be reordered.
232 * If two examples of this operation race, one can appear to succeed
233 * but actually fail. You must protect multiple accesses with a lock.
235 static __always_inline
bool __test_and_set_bit(long nr
, volatile unsigned long *addr
)
239 asm(__ASM_SIZE(bts
) " %2,%1"
242 : ADDR
, "Ir" (nr
) : "memory");
247 * test_and_clear_bit - Clear a bit and return its old value
249 * @addr: Address to count from
251 * This operation is atomic and cannot be reordered.
252 * It also implies a memory barrier.
254 static __always_inline
bool test_and_clear_bit(long nr
, volatile unsigned long *addr
)
256 GEN_BINARY_RMWcc(LOCK_PREFIX
__ASM_SIZE(btr
),
257 *addr
, "Ir", nr
, "%0", c
);
261 * __test_and_clear_bit - Clear a bit and return its old value
263 * @addr: Address to count from
265 * This operation is non-atomic and can be reordered.
266 * If two examples of this operation race, one can appear to succeed
267 * but actually fail. You must protect multiple accesses with a lock.
269 * Note: the operation is performed atomically with respect to
270 * the local CPU, but not other CPUs. Portable code should not
271 * rely on this behaviour.
272 * KVM relies on this behaviour on x86 for modifying memory that is also
273 * accessed from a hypervisor on the same CPU if running in a VM: don't change
274 * this without also updating arch/x86/kernel/kvm.c
276 static __always_inline
bool __test_and_clear_bit(long nr
, volatile unsigned long *addr
)
280 asm volatile(__ASM_SIZE(btr
) " %2,%1"
283 : ADDR
, "Ir" (nr
) : "memory");
287 /* WARNING: non atomic and it can be reordered! */
288 static __always_inline
bool __test_and_change_bit(long nr
, volatile unsigned long *addr
)
292 asm volatile(__ASM_SIZE(btc
) " %2,%1"
295 : ADDR
, "Ir" (nr
) : "memory");
301 * test_and_change_bit - Change a bit and return its old value
303 * @addr: Address to count from
305 * This operation is atomic and cannot be reordered.
306 * It also implies a memory barrier.
308 static __always_inline
bool test_and_change_bit(long nr
, volatile unsigned long *addr
)
310 GEN_BINARY_RMWcc(LOCK_PREFIX
__ASM_SIZE(btc
),
311 *addr
, "Ir", nr
, "%0", c
);
314 static __always_inline
bool constant_test_bit(long nr
, const volatile unsigned long *addr
)
316 return ((1UL << (nr
& (BITS_PER_LONG
-1))) &
317 (addr
[nr
>> _BITOPS_LONG_SHIFT
])) != 0;
320 static __always_inline
bool variable_test_bit(long nr
, volatile const unsigned long *addr
)
324 asm volatile(__ASM_SIZE(bt
) " %2,%1"
327 : "m" (*(unsigned long *)addr
), "Ir" (nr
) : "memory");
332 #if 0 /* Fool kernel-doc since it doesn't do macros yet */
334 * test_bit - Determine whether a bit is set
335 * @nr: bit number to test
336 * @addr: Address to start counting from
338 static bool test_bit(int nr
, const volatile unsigned long *addr
);
341 #define test_bit(nr, addr) \
342 (__builtin_constant_p((nr)) \
343 ? constant_test_bit((nr), (addr)) \
344 : variable_test_bit((nr), (addr)))
347 * __ffs - find first set bit in word
348 * @word: The word to search
350 * Undefined if no bit exists, so code should check against 0 first.
352 static __always_inline
unsigned long __ffs(unsigned long word
)
361 * ffz - find first zero bit in word
362 * @word: The word to search
364 * Undefined if no zero exists, so code should check against ~0UL first.
366 static __always_inline
unsigned long ffz(unsigned long word
)
375 * __fls: find last set bit in word
376 * @word: The word to search
378 * Undefined if no set bit exists, so code should check against 0 first.
380 static __always_inline
unsigned long __fls(unsigned long word
)
392 * ffs - find first set bit in word
393 * @x: the word to search
395 * This is defined the same way as the libc and compiler builtin ffs
396 * routines, therefore differs in spirit from the other bitops.
398 * ffs(value) returns 0 if value is 0 or the position of the first
399 * set bit if value is nonzero. The first (least significant) bit
402 static __always_inline
int ffs(int x
)
408 * AMD64 says BSFL won't clobber the dest reg if x==0; Intel64 says the
409 * dest reg is undefined if x==0, but their CPU architect says its
410 * value is written to set it to the same as before, except that the
411 * top 32 bits will be cleared.
413 * We cannot do this on 32 bits because at the very least some
414 * 486 CPUs did not behave this way.
418 : "rm" (x
), "0" (-1));
419 #elif defined(CONFIG_X86_CMOV)
422 : "=&r" (r
) : "rm" (x
), "r" (-1));
427 "1:" : "=r" (r
) : "rm" (x
));
433 * fls - find last set bit in word
434 * @x: the word to search
436 * This is defined in a similar way as the libc and compiler builtin
437 * ffs, but returns the position of the most significant set bit.
439 * fls(value) returns 0 if value is 0 or the position of the last
440 * set bit if value is nonzero. The last (most significant) bit is
443 static __always_inline
int fls(int x
)
449 * AMD64 says BSRL won't clobber the dest reg if x==0; Intel64 says the
450 * dest reg is undefined if x==0, but their CPU architect says its
451 * value is written to set it to the same as before, except that the
452 * top 32 bits will be cleared.
454 * We cannot do this on 32 bits because at the very least some
455 * 486 CPUs did not behave this way.
459 : "rm" (x
), "0" (-1));
460 #elif defined(CONFIG_X86_CMOV)
463 : "=&r" (r
) : "rm" (x
), "rm" (-1));
468 "1:" : "=r" (r
) : "rm" (x
));
474 * fls64 - find last set bit in a 64-bit word
475 * @x: the word to search
477 * This is defined in a similar way as the libc and compiler builtin
478 * ffsll, but returns the position of the most significant set bit.
480 * fls64(value) returns 0 if value is 0 or the position of the last
481 * set bit if value is nonzero. The last (most significant) bit is
485 static __always_inline
int fls64(__u64 x
)
489 * AMD64 says BSRQ won't clobber the dest reg if x==0; Intel64 says the
490 * dest reg is undefined if x==0, but their CPU architect says its
491 * value is written to set it to the same as before.
499 #include <asm-generic/bitops/fls64.h>
502 #include <asm-generic/bitops/find.h>
504 #include <asm-generic/bitops/sched.h>
506 #include <asm/arch_hweight.h>
508 #include <asm-generic/bitops/const_hweight.h>
510 #include <asm-generic/bitops/le.h>
512 #include <asm-generic/bitops/ext2-atomic-setbit.h>
514 #endif /* __KERNEL__ */
515 #endif /* _ASM_X86_BITOPS_H */