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
  19#if BITS_PER_LONG == 32
  20# define _BITOPS_LONG_SHIFT 5
  21#elif BITS_PER_LONG == 64
  22# define _BITOPS_LONG_SHIFT 6
  23#else
  24# error "Unexpected BITS_PER_LONG"
  25#endif
  26
  27#define BIT_64(n)                       (U64_C(1) << (n))
  28
  29/*
  30 * These have to be done with inline assembly: that way the bit-setting
  31 * is guaranteed to be atomic. All bit operations return 0 if the bit
  32 * was cleared before the operation and != 0 if it was not.
  33 *
  34 * bit 0 is the LSB of addr; bit 32 is the LSB of (addr+1).
  35 */
  36
  37#if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 1)
  38/* Technically wrong, but this avoids compilation errors on some gcc
  39   versions. */
  40#define BITOP_ADDR(x) "=m" (*(volatile long *) (x))
  41#else
  42#define BITOP_ADDR(x) "+m" (*(volatile long *) (x))
  43#endif
  44
  45#define ADDR                            BITOP_ADDR(addr)
  46
  47/*
  48 * We do the locked ops that don't return the old value as
  49 * a mask operation on a byte.
  50 */
  51#define IS_IMMEDIATE(nr)                (__builtin_constant_p(nr))
  52#define CONST_MASK_ADDR(nr, addr)       BITOP_ADDR((void *)(addr) + ((nr)>>3))
  53#define CONST_MASK(nr)                  (1 << ((nr) & 7))
  54
  55/**
  56 * set_bit - Atomically set a bit in memory
  57 * @nr: the bit to set
  58 * @addr: the address to start counting from
  59 *
  60 * This function is atomic and may not be reordered.  See __set_bit()
  61 * if you do not require the atomic guarantees.
  62 *
  63 * Note: there are no guarantees that this function will not be reordered
  64 * on non x86 architectures, so if you are writing portable code,
  65 * make sure not to rely on its reordering guarantees.
  66 *
  67 * Note that @nr may be almost arbitrarily large; this function is not
  68 * restricted to acting on a single-word quantity.
  69 */
  70static __always_inline void
  71set_bit(long nr, volatile unsigned long *addr)
  72{
  73        if (IS_IMMEDIATE(nr)) {
  74                asm volatile(LOCK_PREFIX "orb %1,%0"
  75                        : CONST_MASK_ADDR(nr, addr)
  76                        : "iq" ((u8)CONST_MASK(nr))
  77                        : "memory");
  78        } else {
  79                asm volatile(LOCK_PREFIX "bts %1,%0"
  80                        : BITOP_ADDR(addr) : "Ir" (nr) : "memory");
  81        }
  82}
  83
  84/**
  85 * __set_bit - Set a bit in memory
  86 * @nr: the bit to set
  87 * @addr: the address to start counting from
  88 *
  89 * Unlike set_bit(), this function is non-atomic and may be reordered.
  90 * If it's called on the same region of memory simultaneously, the effect
  91 * may be that only one operation succeeds.
  92 */
  93static inline void __set_bit(long nr, volatile unsigned long *addr)
  94{
  95        asm volatile("bts %1,%0" : ADDR : "Ir" (nr) : "memory");
  96}
  97
  98/**
  99 * clear_bit - Clears a bit in memory
 100 * @nr: Bit to clear
 101 * @addr: Address to start counting from
 102 *
 103 * clear_bit() is atomic and may not be reordered.  However, it does
 104 * not contain a memory barrier, so if it is used for locking purposes,
 105 * you should call smp_mb__before_clear_bit() and/or smp_mb__after_clear_bit()
 106 * in order to ensure changes are visible on other processors.
 107 */
 108static __always_inline void
 109clear_bit(long nr, volatile unsigned long *addr)
 110{
 111        if (IS_IMMEDIATE(nr)) {
 112                asm volatile(LOCK_PREFIX "andb %1,%0"
 113                        : CONST_MASK_ADDR(nr, addr)
 114                        : "iq" ((u8)~CONST_MASK(nr)));
 115        } else {
 116                asm volatile(LOCK_PREFIX "btr %1,%0"
 117                        : BITOP_ADDR(addr)
 118                        : "Ir" (nr));
 119        }
 120}
 121
 122/*
 123 * clear_bit_unlock - Clears a bit in memory
 124 * @nr: Bit to clear
 125 * @addr: Address to start counting from
 126 *
 127 * clear_bit() is atomic and implies release semantics before the memory
 128 * operation. It can be used for an unlock.
 129 */
 130static inline void clear_bit_unlock(long nr, volatile unsigned long *addr)
 131{
 132        barrier();
 133        clear_bit(nr, addr);
 134}
 135
 136static inline void __clear_bit(long nr, volatile unsigned long *addr)
 137{
 138        asm volatile("btr %1,%0" : ADDR : "Ir" (nr));
 139}
 140
 141/*
 142 * __clear_bit_unlock - Clears a bit in memory
 143 * @nr: Bit to clear
 144 * @addr: Address to start counting from
 145 *
 146 * __clear_bit() is non-atomic and implies release semantics before the memory
 147 * operation. It can be used for an unlock if no other CPUs can concurrently
 148 * modify other bits in the word.
 149 *
 150 * No memory barrier is required here, because x86 cannot reorder stores past
 151 * older loads. Same principle as spin_unlock.
 152 */
 153static inline void __clear_bit_unlock(long nr, volatile unsigned long *addr)
 154{
 155        barrier();
 156        __clear_bit(nr, addr);
 157}
 158
 159#define smp_mb__before_clear_bit()      barrier()
 160#define smp_mb__after_clear_bit()       barrier()
 161
 162/**
 163 * __change_bit - Toggle a bit in memory
 164 * @nr: the bit to change
 165 * @addr: the address to start counting from
 166 *
 167 * Unlike change_bit(), this function is non-atomic and may be reordered.
 168 * If it's called on the same region of memory simultaneously, the effect
 169 * may be that only one operation succeeds.
 170 */
 171static inline void __change_bit(long nr, volatile unsigned long *addr)
 172{
 173        asm volatile("btc %1,%0" : ADDR : "Ir" (nr));
 174}
 175
 176/**
 177 * change_bit - Toggle a bit in memory
 178 * @nr: Bit to change
 179 * @addr: Address to start counting from
 180 *
 181 * change_bit() is atomic and may not be reordered.
 182 * Note that @nr may be almost arbitrarily large; this function is not
 183 * restricted to acting on a single-word quantity.
 184 */
 185static inline void change_bit(long nr, volatile unsigned long *addr)
 186{
 187        if (IS_IMMEDIATE(nr)) {
 188                asm volatile(LOCK_PREFIX "xorb %1,%0"
 189                        : CONST_MASK_ADDR(nr, addr)
 190                        : "iq" ((u8)CONST_MASK(nr)));
 191        } else {
 192                asm volatile(LOCK_PREFIX "btc %1,%0"
 193                        : BITOP_ADDR(addr)
 194                        : "Ir" (nr));
 195        }
 196}
 197
 198/**
 199 * test_and_set_bit - Set a bit and return its old value
 200 * @nr: Bit to set
 201 * @addr: Address to count from
 202 *
 203 * This operation is atomic and cannot be reordered.
 204 * It also implies a memory barrier.
 205 */
 206static inline int test_and_set_bit(long nr, volatile unsigned long *addr)
 207{
 208        GEN_BINARY_RMWcc(LOCK_PREFIX "bts", *addr, "Ir", nr, "%0", "c");
 209}
 210
 211/**
 212 * test_and_set_bit_lock - Set a bit and return its old value for lock
 213 * @nr: Bit to set
 214 * @addr: Address to count from
 215 *
 216 * This is the same as test_and_set_bit on x86.
 217 */
 218static __always_inline int
 219test_and_set_bit_lock(long nr, volatile unsigned long *addr)
 220{
 221        return test_and_set_bit(nr, addr);
 222}
 223
 224/**
 225 * __test_and_set_bit - Set a bit and return its old value
 226 * @nr: Bit to set
 227 * @addr: Address to count from
 228 *
 229 * This operation is non-atomic and can be reordered.
 230 * If two examples of this operation race, one can appear to succeed
 231 * but actually fail.  You must protect multiple accesses with a lock.
 232 */
 233static inline int __test_and_set_bit(long nr, volatile unsigned long *addr)
 234{
 235        int oldbit;
 236
 237        asm("bts %2,%1\n\t"
 238            "sbb %0,%0"
 239            : "=r" (oldbit), ADDR
 240            : "Ir" (nr));
 241        return oldbit;
 242}
 243
 244/**
 245 * test_and_clear_bit - Clear a bit and return its old value
 246 * @nr: Bit to clear
 247 * @addr: Address to count from
 248 *
 249 * This operation is atomic and cannot be reordered.
 250 * It also implies a memory barrier.
 251 */
 252static inline int test_and_clear_bit(long nr, volatile unsigned long *addr)
 253{
 254        GEN_BINARY_RMWcc(LOCK_PREFIX "btr", *addr, "Ir", nr, "%0", "c");
 255}
 256
 257/**
 258 * __test_and_clear_bit - Clear a bit and return its old value
 259 * @nr: Bit to clear
 260 * @addr: Address to count from
 261 *
 262 * This operation is non-atomic and can be reordered.
 263 * If two examples of this operation race, one can appear to succeed
 264 * but actually fail.  You must protect multiple accesses with a lock.
 265 *
 266 * Note: the operation is performed atomically with respect to
 267 * the local CPU, but not other CPUs. Portable code should not
 268 * rely on this behaviour.
 269 * KVM relies on this behaviour on x86 for modifying memory that is also
 270 * accessed from a hypervisor on the same CPU if running in a VM: don't change
 271 * this without also updating arch/x86/kernel/kvm.c
 272 */
 273static inline int __test_and_clear_bit(long nr, volatile unsigned long *addr)
 274{
 275        int oldbit;
 276
 277        asm volatile("btr %2,%1\n\t"
 278                     "sbb %0,%0"
 279                     : "=r" (oldbit), ADDR
 280                     : "Ir" (nr));
 281        return oldbit;
 282}
 283
 284/* WARNING: non atomic and it can be reordered! */
 285static inline int __test_and_change_bit(long nr, volatile unsigned long *addr)
 286{
 287        int oldbit;
 288
 289        asm volatile("btc %2,%1\n\t"
 290                     "sbb %0,%0"
 291                     : "=r" (oldbit), ADDR
 292                     : "Ir" (nr) : "memory");
 293
 294        return oldbit;
 295}
 296
 297/**
 298 * test_and_change_bit - Change a bit and return its old value
 299 * @nr: Bit to change
 300 * @addr: Address to count from
 301 *
 302 * This operation is atomic and cannot be reordered.
 303 * It also implies a memory barrier.
 304 */
 305static inline int test_and_change_bit(long nr, volatile unsigned long *addr)
 306{
 307        GEN_BINARY_RMWcc(LOCK_PREFIX "btc", *addr, "Ir", nr, "%0", "c");
 308}
 309
 310static __always_inline int constant_test_bit(long nr, const volatile unsigned long *addr)
 311{
 312        return ((1UL << (nr & (BITS_PER_LONG-1))) &
 313                (addr[nr >> _BITOPS_LONG_SHIFT])) != 0;
 314}
 315
 316static inline int variable_test_bit(long nr, volatile const unsigned long *addr)
 317{
 318        int oldbit;
 319
 320        asm volatile("bt %2,%1\n\t"
 321                     "sbb %0,%0"
 322                     : "=r" (oldbit)
 323                     : "m" (*(unsigned long *)addr), "Ir" (nr));
 324
 325        return oldbit;
 326}
 327
 328#if 0 /* Fool kernel-doc since it doesn't do macros yet */
 329/**
 330 * test_bit - Determine whether a bit is set
 331 * @nr: bit number to test
 332 * @addr: Address to start counting from
 333 */
 334static int test_bit(int nr, const volatile unsigned long *addr);
 335#endif
 336
 337#define test_bit(nr, addr)                      \
 338        (__builtin_constant_p((nr))             \
 339         ? constant_test_bit((nr), (addr))      \
 340         : variable_test_bit((nr), (addr)))
 341
 342/**
 343 * __ffs - find first set bit in word
 344 * @word: The word to search
 345 *
 346 * Undefined if no bit exists, so code should check against 0 first.
 347 */
 348static inline unsigned long __ffs(unsigned long word)
 349{
 350        asm("rep; bsf %1,%0"
 351                : "=r" (word)
 352                : "rm" (word));
 353        return word;
 354}
 355
 356/**
 357 * ffz - find first zero bit in word
 358 * @word: The word to search
 359 *
 360 * Undefined if no zero exists, so code should check against ~0UL first.
 361 */
 362static inline unsigned long ffz(unsigned long word)
 363{
 364        asm("rep; bsf %1,%0"
 365                : "=r" (word)
 366                : "r" (~word));
 367        return word;
 368}
 369
 370/*
 371 * __fls: find last set bit in word
 372 * @word: The word to search
 373 *
 374 * Undefined if no set bit exists, so code should check against 0 first.
 375 */
 376static inline unsigned long __fls(unsigned long word)
 377{
 378        asm("bsr %1,%0"
 379            : "=r" (word)
 380            : "rm" (word));
 381        return word;
 382}
 383
 384#undef ADDR
 385
 386#ifdef __KERNEL__
 387/**
 388 * ffs - find first set bit in word
 389 * @x: the word to search
 390 *
 391 * This is defined the same way as the libc and compiler builtin ffs
 392 * routines, therefore differs in spirit from the other bitops.
 393 *
 394 * ffs(value) returns 0 if value is 0 or the position of the first
 395 * set bit if value is nonzero. The first (least significant) bit
 396 * is at position 1.
 397 */
 398static inline int ffs(int x)
 399{
 400        int r;
 401
 402#ifdef CONFIG_X86_64
 403        /*
 404         * AMD64 says BSFL won't clobber the dest reg if x==0; Intel64 says the
 405         * dest reg is undefined if x==0, but their CPU architect says its
 406         * value is written to set it to the same as before, except that the
 407         * top 32 bits will be cleared.
 408         *
 409         * We cannot do this on 32 bits because at the very least some
 410         * 486 CPUs did not behave this way.
 411         */
 412        asm("bsfl %1,%0"
 413            : "=r" (r)
 414            : "rm" (x), "0" (-1));
 415#elif defined(CONFIG_X86_CMOV)
 416        asm("bsfl %1,%0\n\t"
 417            "cmovzl %2,%0"
 418            : "=&r" (r) : "rm" (x), "r" (-1));
 419#else
 420        asm("bsfl %1,%0\n\t"
 421            "jnz 1f\n\t"
 422            "movl $-1,%0\n"
 423            "1:" : "=r" (r) : "rm" (x));
 424#endif
 425        return r + 1;
 426}
 427
 428/**
 429 * fls - find last set bit in word
 430 * @x: the word to search
 431 *
 432 * This is defined in a similar way as the libc and compiler builtin
 433 * ffs, but returns the position of the most significant set bit.
 434 *
 435 * fls(value) returns 0 if value is 0 or the position of the last
 436 * set bit if value is nonzero. The last (most significant) bit is
 437 * at position 32.
 438 */
 439static inline int fls(int x)
 440{
 441        int r;
 442
 443#ifdef CONFIG_X86_64
 444        /*
 445         * AMD64 says BSRL won't clobber the dest reg if x==0; Intel64 says the
 446         * dest reg is undefined if x==0, but their CPU architect says its
 447         * value is written to set it to the same as before, except that the
 448         * top 32 bits will be cleared.
 449         *
 450         * We cannot do this on 32 bits because at the very least some
 451         * 486 CPUs did not behave this way.
 452         */
 453        asm("bsrl %1,%0"
 454            : "=r" (r)
 455            : "rm" (x), "0" (-1));
 456#elif defined(CONFIG_X86_CMOV)
 457        asm("bsrl %1,%0\n\t"
 458            "cmovzl %2,%0"
 459            : "=&r" (r) : "rm" (x), "rm" (-1));
 460#else
 461        asm("bsrl %1,%0\n\t"
 462            "jnz 1f\n\t"
 463            "movl $-1,%0\n"
 464            "1:" : "=r" (r) : "rm" (x));
 465#endif
 466        return r + 1;
 467}
 468
 469/**
 470 * fls64 - find last set bit in a 64-bit word
 471 * @x: the word to search
 472 *
 473 * This is defined in a similar way as the libc and compiler builtin
 474 * ffsll, but returns the position of the most significant set bit.
 475 *
 476 * fls64(value) returns 0 if value is 0 or the position of the last
 477 * set bit if value is nonzero. The last (most significant) bit is
 478 * at position 64.
 479 */
 480#ifdef CONFIG_X86_64
 481static __always_inline int fls64(__u64 x)
 482{
 483        int bitpos = -1;
 484        /*
 485         * AMD64 says BSRQ won't clobber the dest reg if x==0; Intel64 says the
 486         * dest reg is undefined if x==0, but their CPU architect says its
 487         * value is written to set it to the same as before.
 488         */
 489        asm("bsrq %1,%q0"
 490            : "+r" (bitpos)
 491            : "rm" (x));
 492        return bitpos + 1;
 493}
 494#else
 495#include <asm-generic/bitops/fls64.h>
 496#endif
 497
 498#include <asm-generic/bitops/find.h>
 499
 500#include <asm-generic/bitops/sched.h>
 501
 502#define ARCH_HAS_FAST_MULTIPLIER 1
 503
 504#include <asm/arch_hweight.h>
 505
 506#include <asm-generic/bitops/const_hweight.h>
 507
 508#include <asm-generic/bitops/le.h>
 509
 510#include <asm-generic/bitops/ext2-atomic-setbit.h>
 511
 512#endif /* __KERNEL__ */
 513#endif /* _ASM_X86_BITOPS_H */
 514