linux/arch/x86/include/asm/bitops.h
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   1#ifndef _ASM_X86_BITOPS_H
   2#define _ASM_X86_BITOPS_H
   3
   4/*
   5 * Copyright 1992, Linus Torvalds.
   6 *
   7 * Note: inlines with more than a single statement should be marked
   8 * __always_inline to avoid problems with older gcc's inlining heuristics.
   9 */
  10
  11#ifndef _LINUX_BITOPS_H
  12#error only <linux/bitops.h> can be included directly
  13#endif
  14
  15#include <linux/compiler.h>
  16#include <asm/alternative.h>
  17#include <asm/rmwcc.h>
  18#include <asm/barrier.h>
  19
  20#if BITS_PER_LONG == 32
  21# define _BITOPS_LONG_SHIFT 5
  22#elif BITS_PER_LONG == 64
  23# define _BITOPS_LONG_SHIFT 6
  24#else
  25# error "Unexpected BITS_PER_LONG"
  26#endif
  27
  28#define BIT_64(n)                       (U64_C(1) << (n))
  29
  30/*
  31 * These have to be done with inline assembly: that way the bit-setting
  32 * is guaranteed to be atomic. All bit operations return 0 if the bit
  33 * was cleared before the operation and != 0 if it was not.
  34 *
  35 * bit 0 is the LSB of addr; bit 32 is the LSB of (addr+1).
  36 */
  37
  38#if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 1)
  39/* Technically wrong, but this avoids compilation errors on some gcc
  40   versions. */
  41#define BITOP_ADDR(x) "=m" (*(volatile long *) (x))
  42#else
  43#define BITOP_ADDR(x) "+m" (*(volatile long *) (x))
  44#endif
  45
  46#define ADDR                            BITOP_ADDR(addr)
  47
  48/*
  49 * We do the locked ops that don't return the old value as
  50 * a mask operation on a byte.
  51 */
  52#define IS_IMMEDIATE(nr)                (__builtin_constant_p(nr))
  53#define CONST_MASK_ADDR(nr, addr)       BITOP_ADDR((void *)(addr) + ((nr)>>3))
  54#define CONST_MASK(nr)                  (1 << ((nr) & 7))
  55
  56/**
  57 * set_bit - Atomically set a bit in memory
  58 * @nr: the bit to set
  59 * @addr: the address to start counting from
  60 *
  61 * This function is atomic and may not be reordered.  See __set_bit()
  62 * if you do not require the atomic guarantees.
  63 *
  64 * Note: there are no guarantees that this function will not be reordered
  65 * on non x86 architectures, so if you are writing portable code,
  66 * make sure not to rely on its reordering guarantees.
  67 *
  68 * Note that @nr may be almost arbitrarily large; this function is not
  69 * restricted to acting on a single-word quantity.
  70 */
  71static __always_inline void
  72set_bit(long nr, volatile unsigned long *addr)
  73{
  74        if (IS_IMMEDIATE(nr)) {
  75                asm volatile(LOCK_PREFIX "orb %1,%0"
  76                        : CONST_MASK_ADDR(nr, addr)
  77                        : "iq" ((u8)CONST_MASK(nr))
  78                        : "memory");
  79        } else {
  80                asm volatile(LOCK_PREFIX "bts %1,%0"
  81                        : BITOP_ADDR(addr) : "Ir" (nr) : "memory");
  82        }
  83}
  84
  85/**
  86 * __set_bit - Set a bit in memory
  87 * @nr: the bit to set
  88 * @addr: the address to start counting from
  89 *
  90 * Unlike set_bit(), this function is non-atomic and may be reordered.
  91 * If it's called on the same region of memory simultaneously, the effect
  92 * may be that only one operation succeeds.
  93 */
  94static __always_inline void __set_bit(long nr, volatile unsigned long *addr)
  95{
  96        asm volatile("bts %1,%0" : ADDR : "Ir" (nr) : "memory");
  97}
  98
  99/**
 100 * clear_bit - Clears a bit in memory
 101 * @nr: Bit to clear
 102 * @addr: Address to start counting from
 103 *
 104 * clear_bit() is atomic and may not be reordered.  However, it does
 105 * not contain a memory barrier, so if it is used for locking purposes,
 106 * you should call smp_mb__before_atomic() and/or smp_mb__after_atomic()
 107 * in order to ensure changes are visible on other processors.
 108 */
 109static __always_inline void
 110clear_bit(long nr, volatile unsigned long *addr)
 111{
 112        if (IS_IMMEDIATE(nr)) {
 113                asm volatile(LOCK_PREFIX "andb %1,%0"
 114                        : CONST_MASK_ADDR(nr, addr)
 115                        : "iq" ((u8)~CONST_MASK(nr)));
 116        } else {
 117                asm volatile(LOCK_PREFIX "btr %1,%0"
 118                        : BITOP_ADDR(addr)
 119                        : "Ir" (nr));
 120        }
 121}
 122
 123/*
 124 * clear_bit_unlock - Clears a bit in memory
 125 * @nr: Bit to clear
 126 * @addr: Address to start counting from
 127 *
 128 * clear_bit() is atomic and implies release semantics before the memory
 129 * operation. It can be used for an unlock.
 130 */
 131static __always_inline void clear_bit_unlock(long nr, volatile unsigned long *addr)
 132{
 133        barrier();
 134        clear_bit(nr, addr);
 135}
 136
 137static __always_inline void __clear_bit(long nr, volatile unsigned long *addr)
 138{
 139        asm volatile("btr %1,%0" : ADDR : "Ir" (nr));
 140}
 141
 142/*
 143 * __clear_bit_unlock - Clears a bit in memory
 144 * @nr: Bit to clear
 145 * @addr: Address to start counting from
 146 *
 147 * __clear_bit() is non-atomic and implies release semantics before the memory
 148 * operation. It can be used for an unlock if no other CPUs can concurrently
 149 * modify other bits in the word.
 150 *
 151 * No memory barrier is required here, because x86 cannot reorder stores past
 152 * older loads. Same principle as spin_unlock.
 153 */
 154static __always_inline void __clear_bit_unlock(long nr, volatile unsigned long *addr)
 155{
 156        barrier();
 157        __clear_bit(nr, addr);
 158}
 159
 160/**
 161 * __change_bit - Toggle a bit in memory
 162 * @nr: the bit to change
 163 * @addr: the address to start counting from
 164 *
 165 * Unlike change_bit(), this function is non-atomic and may be reordered.
 166 * If it's called on the same region of memory simultaneously, the effect
 167 * may be that only one operation succeeds.
 168 */
 169static __always_inline void __change_bit(long nr, volatile unsigned long *addr)
 170{
 171        asm volatile("btc %1,%0" : ADDR : "Ir" (nr));
 172}
 173
 174/**
 175 * change_bit - Toggle a bit in memory
 176 * @nr: Bit to change
 177 * @addr: Address to start counting from
 178 *
 179 * change_bit() is atomic and may not be reordered.
 180 * Note that @nr may be almost arbitrarily large; this function is not
 181 * restricted to acting on a single-word quantity.
 182 */
 183static __always_inline void change_bit(long nr, volatile unsigned long *addr)
 184{
 185        if (IS_IMMEDIATE(nr)) {
 186                asm volatile(LOCK_PREFIX "xorb %1,%0"
 187                        : CONST_MASK_ADDR(nr, addr)
 188                        : "iq" ((u8)CONST_MASK(nr)));
 189        } else {
 190                asm volatile(LOCK_PREFIX "btc %1,%0"
 191                        : BITOP_ADDR(addr)
 192                        : "Ir" (nr));
 193        }
 194}
 195
 196/**
 197 * test_and_set_bit - Set a bit and return its old value
 198 * @nr: Bit to set
 199 * @addr: Address to count from
 200 *
 201 * This operation is atomic and cannot be reordered.
 202 * It also implies a memory barrier.
 203 */
 204static __always_inline int test_and_set_bit(long nr, volatile unsigned long *addr)
 205{
 206        GEN_BINARY_RMWcc(LOCK_PREFIX "bts", *addr, "Ir", nr, "%0", "c");
 207}
 208
 209/**
 210 * test_and_set_bit_lock - Set a bit and return its old value for lock
 211 * @nr: Bit to set
 212 * @addr: Address to count from
 213 *
 214 * This is the same as test_and_set_bit on x86.
 215 */
 216static __always_inline int
 217test_and_set_bit_lock(long nr, volatile unsigned long *addr)
 218{
 219        return test_and_set_bit(nr, addr);
 220}
 221
 222/**
 223 * __test_and_set_bit - Set a bit and return its old value
 224 * @nr: Bit to set
 225 * @addr: Address to count from
 226 *
 227 * This operation is non-atomic and can be reordered.
 228 * If two examples of this operation race, one can appear to succeed
 229 * but actually fail.  You must protect multiple accesses with a lock.
 230 */
 231static __always_inline int __test_and_set_bit(long nr, volatile unsigned long *addr)
 232{
 233        int oldbit;
 234
 235        asm("bts %2,%1\n\t"
 236            "sbb %0,%0"
 237            : "=r" (oldbit), ADDR
 238            : "Ir" (nr));
 239        return oldbit;
 240}
 241
 242/**
 243 * test_and_clear_bit - Clear a bit and return its old value
 244 * @nr: Bit to clear
 245 * @addr: Address to count from
 246 *
 247 * This operation is atomic and cannot be reordered.
 248 * It also implies a memory barrier.
 249 */
 250static __always_inline int test_and_clear_bit(long nr, volatile unsigned long *addr)
 251{
 252        GEN_BINARY_RMWcc(LOCK_PREFIX "btr", *addr, "Ir", nr, "%0", "c");
 253}
 254
 255/**
 256 * __test_and_clear_bit - Clear a bit and return its old value
 257 * @nr: Bit to clear
 258 * @addr: Address to count from
 259 *
 260 * This operation is non-atomic and can be reordered.
 261 * If two examples of this operation race, one can appear to succeed
 262 * but actually fail.  You must protect multiple accesses with a lock.
 263 *
 264 * Note: the operation is performed atomically with respect to
 265 * the local CPU, but not other CPUs. Portable code should not
 266 * rely on this behaviour.
 267 * KVM relies on this behaviour on x86 for modifying memory that is also
 268 * accessed from a hypervisor on the same CPU if running in a VM: don't change
 269 * this without also updating arch/x86/kernel/kvm.c
 270 */
 271static __always_inline int __test_and_clear_bit(long nr, volatile unsigned long *addr)
 272{
 273        int oldbit;
 274
 275        asm volatile("btr %2,%1\n\t"
 276                     "sbb %0,%0"
 277                     : "=r" (oldbit), ADDR
 278                     : "Ir" (nr));
 279        return oldbit;
 280}
 281
 282/* WARNING: non atomic and it can be reordered! */
 283static __always_inline int __test_and_change_bit(long nr, volatile unsigned long *addr)
 284{
 285        int oldbit;
 286
 287        asm volatile("btc %2,%1\n\t"
 288                     "sbb %0,%0"
 289                     : "=r" (oldbit), ADDR
 290                     : "Ir" (nr) : "memory");
 291
 292        return oldbit;
 293}
 294
 295/**
 296 * test_and_change_bit - Change a bit and return its old value
 297 * @nr: Bit to change
 298 * @addr: Address to count from
 299 *
 300 * This operation is atomic and cannot be reordered.
 301 * It also implies a memory barrier.
 302 */
 303static __always_inline int test_and_change_bit(long nr, volatile unsigned long *addr)
 304{
 305        GEN_BINARY_RMWcc(LOCK_PREFIX "btc", *addr, "Ir", nr, "%0", "c");
 306}
 307
 308static __always_inline int constant_test_bit(long nr, const volatile unsigned long *addr)
 309{
 310        return ((1UL << (nr & (BITS_PER_LONG-1))) &
 311                (addr[nr >> _BITOPS_LONG_SHIFT])) != 0;
 312}
 313
 314static __always_inline int variable_test_bit(long nr, volatile const unsigned long *addr)
 315{
 316        int oldbit;
 317
 318        asm volatile("bt %2,%1\n\t"
 319                     "sbb %0,%0"
 320                     : "=r" (oldbit)
 321                     : "m" (*(unsigned long *)addr), "Ir" (nr));
 322
 323        return oldbit;
 324}
 325
 326#if 0 /* Fool kernel-doc since it doesn't do macros yet */
 327/**
 328 * test_bit - Determine whether a bit is set
 329 * @nr: bit number to test
 330 * @addr: Address to start counting from
 331 */
 332static int test_bit(int nr, const volatile unsigned long *addr);
 333#endif
 334
 335#define test_bit(nr, addr)                      \
 336        (__builtin_constant_p((nr))             \
 337         ? constant_test_bit((nr), (addr))      \
 338         : variable_test_bit((nr), (addr)))
 339
 340/**
 341 * __ffs - find first set bit in word
 342 * @word: The word to search
 343 *
 344 * Undefined if no bit exists, so code should check against 0 first.
 345 */
 346static __always_inline unsigned long __ffs(unsigned long word)
 347{
 348        asm("rep; bsf %1,%0"
 349                : "=r" (word)
 350                : "rm" (word));
 351        return word;
 352}
 353
 354/**
 355 * ffz - find first zero bit in word
 356 * @word: The word to search
 357 *
 358 * Undefined if no zero exists, so code should check against ~0UL first.
 359 */
 360static __always_inline unsigned long ffz(unsigned long word)
 361{
 362        asm("rep; bsf %1,%0"
 363                : "=r" (word)
 364                : "r" (~word));
 365        return word;
 366}
 367
 368/*
 369 * __fls: find last set bit in word
 370 * @word: The word to search
 371 *
 372 * Undefined if no set bit exists, so code should check against 0 first.
 373 */
 374static __always_inline unsigned long __fls(unsigned long word)
 375{
 376        asm("bsr %1,%0"
 377            : "=r" (word)
 378            : "rm" (word));
 379        return word;
 380}
 381
 382#undef ADDR
 383
 384#ifdef __KERNEL__
 385/**
 386 * ffs - find first set bit in word
 387 * @x: the word to search
 388 *
 389 * This is defined the same way as the libc and compiler builtin ffs
 390 * routines, therefore differs in spirit from the other bitops.
 391 *
 392 * ffs(value) returns 0 if value is 0 or the position of the first
 393 * set bit if value is nonzero. The first (least significant) bit
 394 * is at position 1.
 395 */
 396static __always_inline int ffs(int x)
 397{
 398        int r;
 399
 400#ifdef CONFIG_X86_64
 401        /*
 402         * AMD64 says BSFL won't clobber the dest reg if x==0; Intel64 says the
 403         * dest reg is undefined if x==0, but their CPU architect says its
 404         * value is written to set it to the same as before, except that the
 405         * top 32 bits will be cleared.
 406         *
 407         * We cannot do this on 32 bits because at the very least some
 408         * 486 CPUs did not behave this way.
 409         */
 410        asm("bsfl %1,%0"
 411            : "=r" (r)
 412            : "rm" (x), "0" (-1));
 413#elif defined(CONFIG_X86_CMOV)
 414        asm("bsfl %1,%0\n\t"
 415            "cmovzl %2,%0"
 416            : "=&r" (r) : "rm" (x), "r" (-1));
 417#else
 418        asm("bsfl %1,%0\n\t"
 419            "jnz 1f\n\t"
 420            "movl $-1,%0\n"
 421            "1:" : "=r" (r) : "rm" (x));
 422#endif
 423        return r + 1;
 424}
 425
 426/**
 427 * fls - find last set bit in word
 428 * @x: the word to search
 429 *
 430 * This is defined in a similar way as the libc and compiler builtin
 431 * ffs, but returns the position of the most significant set bit.
 432 *
 433 * fls(value) returns 0 if value is 0 or the position of the last
 434 * set bit if value is nonzero. The last (most significant) bit is
 435 * at position 32.
 436 */
 437static __always_inline int fls(int x)
 438{
 439        int r;
 440
 441#ifdef CONFIG_X86_64
 442        /*
 443         * AMD64 says BSRL won't clobber the dest reg if x==0; Intel64 says the
 444         * dest reg is undefined if x==0, but their CPU architect says its
 445         * value is written to set it to the same as before, except that the
 446         * top 32 bits will be cleared.
 447         *
 448         * We cannot do this on 32 bits because at the very least some
 449         * 486 CPUs did not behave this way.
 450         */
 451        asm("bsrl %1,%0"
 452            : "=r" (r)
 453            : "rm" (x), "0" (-1));
 454#elif defined(CONFIG_X86_CMOV)
 455        asm("bsrl %1,%0\n\t"
 456            "cmovzl %2,%0"
 457            : "=&r" (r) : "rm" (x), "rm" (-1));
 458#else
 459        asm("bsrl %1,%0\n\t"
 460            "jnz 1f\n\t"
 461            "movl $-1,%0\n"
 462            "1:" : "=r" (r) : "rm" (x));
 463#endif
 464        return r + 1;
 465}
 466
 467/**
 468 * fls64 - find last set bit in a 64-bit word
 469 * @x: the word to search
 470 *
 471 * This is defined in a similar way as the libc and compiler builtin
 472 * ffsll, but returns the position of the most significant set bit.
 473 *
 474 * fls64(value) returns 0 if value is 0 or the position of the last
 475 * set bit if value is nonzero. The last (most significant) bit is
 476 * at position 64.
 477 */
 478#ifdef CONFIG_X86_64
 479static __always_inline int fls64(__u64 x)
 480{
 481        int bitpos = -1;
 482        /*
 483         * AMD64 says BSRQ won't clobber the dest reg if x==0; Intel64 says the
 484         * dest reg is undefined if x==0, but their CPU architect says its
 485         * value is written to set it to the same as before.
 486         */
 487        asm("bsrq %1,%q0"
 488            : "+r" (bitpos)
 489            : "rm" (x));
 490        return bitpos + 1;
 491}
 492#else
 493#include <asm-generic/bitops/fls64.h>
 494#endif
 495
 496#include <asm-generic/bitops/find.h>
 497
 498#include <asm-generic/bitops/sched.h>
 499
 500#include <asm/arch_hweight.h>
 501
 502#include <asm-generic/bitops/const_hweight.h>
 503
 504#include <asm-generic/bitops/le.h>
 505
 506#include <asm-generic/bitops/ext2-atomic-setbit.h>
 507
 508#endif /* __KERNEL__ */
 509#endif /* _ASM_X86_BITOPS_H */
 510