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
 142static __always_inline bool clear_bit_unlock_is_negative_byte(long nr, volatile unsigned long *addr)
 143{
 144        bool negative;
 145        asm volatile(LOCK_PREFIX "andb %2,%1\n\t"
 146                CC_SET(s)
 147                : CC_OUT(s) (negative), ADDR
 148                : "ir" ((char) ~(1 << nr)) : "memory");
 149        return negative;
 150}
 151
 152// Let everybody know we have it
 153#define clear_bit_unlock_is_negative_byte clear_bit_unlock_is_negative_byte
 154
 155/*
 156 * __clear_bit_unlock - Clears a bit in memory
 157 * @nr: Bit to clear
 158 * @addr: Address to start counting from
 159 *
 160 * __clear_bit() is non-atomic and implies release semantics before the memory
 161 * operation. It can be used for an unlock if no other CPUs can concurrently
 162 * modify other bits in the word.
 163 *
 164 * No memory barrier is required here, because x86 cannot reorder stores past
 165 * older loads. Same principle as spin_unlock.
 166 */
 167static __always_inline void __clear_bit_unlock(long nr, volatile unsigned long *addr)
 168{
 169        barrier();
 170        __clear_bit(nr, addr);
 171}
 172
 173/**
 174 * __change_bit - Toggle a bit in memory
 175 * @nr: the bit to change
 176 * @addr: the address to start counting from
 177 *
 178 * Unlike change_bit(), this function is non-atomic and may be reordered.
 179 * If it's called on the same region of memory simultaneously, the effect
 180 * may be that only one operation succeeds.
 181 */
 182static __always_inline void __change_bit(long nr, volatile unsigned long *addr)
 183{
 184        asm volatile("btc %1,%0" : ADDR : "Ir" (nr));
 185}
 186
 187/**
 188 * change_bit - Toggle a bit in memory
 189 * @nr: Bit to change
 190 * @addr: Address to start counting from
 191 *
 192 * change_bit() is atomic and may not be reordered.
 193 * Note that @nr may be almost arbitrarily large; this function is not
 194 * restricted to acting on a single-word quantity.
 195 */
 196static __always_inline void change_bit(long nr, volatile unsigned long *addr)
 197{
 198        if (IS_IMMEDIATE(nr)) {
 199                asm volatile(LOCK_PREFIX "xorb %1,%0"
 200                        : CONST_MASK_ADDR(nr, addr)
 201                        : "iq" ((u8)CONST_MASK(nr)));
 202        } else {
 203                asm volatile(LOCK_PREFIX "btc %1,%0"
 204                        : BITOP_ADDR(addr)
 205                        : "Ir" (nr));
 206        }
 207}
 208
 209/**
 210 * test_and_set_bit - Set a bit and return its old value
 211 * @nr: Bit to set
 212 * @addr: Address to count from
 213 *
 214 * This operation is atomic and cannot be reordered.
 215 * It also implies a memory barrier.
 216 */
 217static __always_inline bool test_and_set_bit(long nr, volatile unsigned long *addr)
 218{
 219        GEN_BINARY_RMWcc(LOCK_PREFIX "bts", *addr, "Ir", nr, "%0", c);
 220}
 221
 222/**
 223 * test_and_set_bit_lock - Set a bit and return its old value for lock
 224 * @nr: Bit to set
 225 * @addr: Address to count from
 226 *
 227 * This is the same as test_and_set_bit on x86.
 228 */
 229static __always_inline bool
 230test_and_set_bit_lock(long nr, volatile unsigned long *addr)
 231{
 232        return test_and_set_bit(nr, addr);
 233}
 234
 235/**
 236 * __test_and_set_bit - Set a bit and return its old value
 237 * @nr: Bit to set
 238 * @addr: Address to count from
 239 *
 240 * This operation is non-atomic and can be reordered.
 241 * If two examples of this operation race, one can appear to succeed
 242 * but actually fail.  You must protect multiple accesses with a lock.
 243 */
 244static __always_inline bool __test_and_set_bit(long nr, volatile unsigned long *addr)
 245{
 246        bool oldbit;
 247
 248        asm("bts %2,%1\n\t"
 249            CC_SET(c)
 250            : CC_OUT(c) (oldbit), ADDR
 251            : "Ir" (nr));
 252        return oldbit;
 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 atomic and cannot be reordered.
 261 * It also implies a memory barrier.
 262 */
 263static __always_inline bool test_and_clear_bit(long nr, volatile unsigned long *addr)
 264{
 265        GEN_BINARY_RMWcc(LOCK_PREFIX "btr", *addr, "Ir", nr, "%0", c);
 266}
 267
 268/**
 269 * __test_and_clear_bit - Clear a bit and return its old value
 270 * @nr: Bit to clear
 271 * @addr: Address to count from
 272 *
 273 * This operation is non-atomic and can be reordered.
 274 * If two examples of this operation race, one can appear to succeed
 275 * but actually fail.  You must protect multiple accesses with a lock.
 276 *
 277 * Note: the operation is performed atomically with respect to
 278 * the local CPU, but not other CPUs. Portable code should not
 279 * rely on this behaviour.
 280 * KVM relies on this behaviour on x86 for modifying memory that is also
 281 * accessed from a hypervisor on the same CPU if running in a VM: don't change
 282 * this without also updating arch/x86/kernel/kvm.c
 283 */
 284static __always_inline bool __test_and_clear_bit(long nr, volatile unsigned long *addr)
 285{
 286        bool oldbit;
 287
 288        asm volatile("btr %2,%1\n\t"
 289                     CC_SET(c)
 290                     : CC_OUT(c) (oldbit), ADDR
 291                     : "Ir" (nr));
 292        return oldbit;
 293}
 294
 295/* WARNING: non atomic and it can be reordered! */
 296static __always_inline bool __test_and_change_bit(long nr, volatile unsigned long *addr)
 297{
 298        bool oldbit;
 299
 300        asm volatile("btc %2,%1\n\t"
 301                     CC_SET(c)
 302                     : CC_OUT(c) (oldbit), ADDR
 303                     : "Ir" (nr) : "memory");
 304
 305        return oldbit;
 306}
 307
 308/**
 309 * test_and_change_bit - Change a bit and return its old value
 310 * @nr: Bit to change
 311 * @addr: Address to count from
 312 *
 313 * This operation is atomic and cannot be reordered.
 314 * It also implies a memory barrier.
 315 */
 316static __always_inline bool test_and_change_bit(long nr, volatile unsigned long *addr)
 317{
 318        GEN_BINARY_RMWcc(LOCK_PREFIX "btc", *addr, "Ir", nr, "%0", c);
 319}
 320
 321static __always_inline bool constant_test_bit(long nr, const volatile unsigned long *addr)
 322{
 323        return ((1UL << (nr & (BITS_PER_LONG-1))) &
 324                (addr[nr >> _BITOPS_LONG_SHIFT])) != 0;
 325}
 326
 327static __always_inline bool variable_test_bit(long nr, volatile const unsigned long *addr)
 328{
 329        bool oldbit;
 330
 331        asm volatile("bt %2,%1\n\t"
 332                     CC_SET(c)
 333                     : CC_OUT(c) (oldbit)
 334                     : "m" (*(unsigned long *)addr), "Ir" (nr));
 335
 336        return oldbit;
 337}
 338
 339#if 0 /* Fool kernel-doc since it doesn't do macros yet */
 340/**
 341 * test_bit - Determine whether a bit is set
 342 * @nr: bit number to test
 343 * @addr: Address to start counting from
 344 */
 345static bool test_bit(int nr, const volatile unsigned long *addr);
 346#endif
 347
 348#define test_bit(nr, addr)                      \
 349        (__builtin_constant_p((nr))             \
 350         ? constant_test_bit((nr), (addr))      \
 351         : variable_test_bit((nr), (addr)))
 352
 353/**
 354 * __ffs - find first set bit in word
 355 * @word: The word to search
 356 *
 357 * Undefined if no bit exists, so code should check against 0 first.
 358 */
 359static __always_inline unsigned long __ffs(unsigned long word)
 360{
 361        asm("rep; bsf %1,%0"
 362                : "=r" (word)
 363                : "rm" (word));
 364        return word;
 365}
 366
 367/**
 368 * ffz - find first zero bit in word
 369 * @word: The word to search
 370 *
 371 * Undefined if no zero exists, so code should check against ~0UL first.
 372 */
 373static __always_inline unsigned long ffz(unsigned long word)
 374{
 375        asm("rep; bsf %1,%0"
 376                : "=r" (word)
 377                : "r" (~word));
 378        return word;
 379}
 380
 381/*
 382 * __fls: find last set bit in word
 383 * @word: The word to search
 384 *
 385 * Undefined if no set bit exists, so code should check against 0 first.
 386 */
 387static __always_inline unsigned long __fls(unsigned long word)
 388{
 389        asm("bsr %1,%0"
 390            : "=r" (word)
 391            : "rm" (word));
 392        return word;
 393}
 394
 395#undef ADDR
 396
 397#ifdef __KERNEL__
 398/**
 399 * ffs - find first set bit in word
 400 * @x: the word to search
 401 *
 402 * This is defined the same way as the libc and compiler builtin ffs
 403 * routines, therefore differs in spirit from the other bitops.
 404 *
 405 * ffs(value) returns 0 if value is 0 or the position of the first
 406 * set bit if value is nonzero. The first (least significant) bit
 407 * is at position 1.
 408 */
 409static __always_inline int ffs(int x)
 410{
 411        int r;
 412
 413#ifdef CONFIG_X86_64
 414        /*
 415         * AMD64 says BSFL won't clobber the dest reg if x==0; Intel64 says the
 416         * dest reg is undefined if x==0, but their CPU architect says its
 417         * value is written to set it to the same as before, except that the
 418         * top 32 bits will be cleared.
 419         *
 420         * We cannot do this on 32 bits because at the very least some
 421         * 486 CPUs did not behave this way.
 422         */
 423        asm("bsfl %1,%0"
 424            : "=r" (r)
 425            : "rm" (x), "0" (-1));
 426#elif defined(CONFIG_X86_CMOV)
 427        asm("bsfl %1,%0\n\t"
 428            "cmovzl %2,%0"
 429            : "=&r" (r) : "rm" (x), "r" (-1));
 430#else
 431        asm("bsfl %1,%0\n\t"
 432            "jnz 1f\n\t"
 433            "movl $-1,%0\n"
 434            "1:" : "=r" (r) : "rm" (x));
 435#endif
 436        return r + 1;
 437}
 438
 439/**
 440 * fls - find last set bit in word
 441 * @x: the word to search
 442 *
 443 * This is defined in a similar way as the libc and compiler builtin
 444 * ffs, but returns the position of the most significant set bit.
 445 *
 446 * fls(value) returns 0 if value is 0 or the position of the last
 447 * set bit if value is nonzero. The last (most significant) bit is
 448 * at position 32.
 449 */
 450static __always_inline int fls(int x)
 451{
 452        int r;
 453
 454#ifdef CONFIG_X86_64
 455        /*
 456         * AMD64 says BSRL won't clobber the dest reg if x==0; Intel64 says the
 457         * dest reg is undefined if x==0, but their CPU architect says its
 458         * value is written to set it to the same as before, except that the
 459         * top 32 bits will be cleared.
 460         *
 461         * We cannot do this on 32 bits because at the very least some
 462         * 486 CPUs did not behave this way.
 463         */
 464        asm("bsrl %1,%0"
 465            : "=r" (r)
 466            : "rm" (x), "0" (-1));
 467#elif defined(CONFIG_X86_CMOV)
 468        asm("bsrl %1,%0\n\t"
 469            "cmovzl %2,%0"
 470            : "=&r" (r) : "rm" (x), "rm" (-1));
 471#else
 472        asm("bsrl %1,%0\n\t"
 473            "jnz 1f\n\t"
 474            "movl $-1,%0\n"
 475            "1:" : "=r" (r) : "rm" (x));
 476#endif
 477        return r + 1;
 478}
 479
 480/**
 481 * fls64 - find last set bit in a 64-bit word
 482 * @x: the word to search
 483 *
 484 * This is defined in a similar way as the libc and compiler builtin
 485 * ffsll, but returns the position of the most significant set bit.
 486 *
 487 * fls64(value) returns 0 if value is 0 or the position of the last
 488 * set bit if value is nonzero. The last (most significant) bit is
 489 * at position 64.
 490 */
 491#ifdef CONFIG_X86_64
 492static __always_inline int fls64(__u64 x)
 493{
 494        int bitpos = -1;
 495        /*
 496         * AMD64 says BSRQ won't clobber the dest reg if x==0; Intel64 says the
 497         * dest reg is undefined if x==0, but their CPU architect says its
 498         * value is written to set it to the same as before.
 499         */
 500        asm("bsrq %1,%q0"
 501            : "+r" (bitpos)
 502            : "rm" (x));
 503        return bitpos + 1;
 504}
 505#else
 506#include <asm-generic/bitops/fls64.h>
 507#endif
 508
 509#include <asm-generic/bitops/find.h>
 510
 511#include <asm-generic/bitops/sched.h>
 512
 513#include <asm/arch_hweight.h>
 514
 515#include <asm-generic/bitops/const_hweight.h>
 516
 517#include <asm-generic/bitops/le.h>
 518
 519#include <asm-generic/bitops/ext2-atomic-setbit.h>
 520
 521#endif /* __KERNEL__ */
 522#endif /* _ASM_X86_BITOPS_H */
 523