include/asm-i386/bitops.h

   1 #ifndef _I386_BITOPS_H
   2 #define _I386_BITOPS_H
   3
   4 /*
   5  * Copyright 1992, Linus Torvalds.
   6  */
   7
   8
   9 /*
  10  * These have to be done with inline assembly: that way the bit-setting
  11  * is guaranteed to be atomic. All bit operations return 0 if the bit
  12  * was cleared before the operation and != 0 if it was not.
  13  *
  14  * bit 0 is the LSB of addr; bit 32 is the LSB of (addr+1).
  15  */
  16
  17 #ifdef CONFIG_SMP
  18 #define LOCK_PREFIX "lock ; "
  19 #else
  20 #define LOCK_PREFIX ""
  21 #endif
  22
  23 #define ADDR (*(volatile long *) addr)
  24
  25 /**
  26  * set_bit - Atomically set a bit in memory
  27  * @nr: the bit to set
  28  * @addr: the address to start counting from
  29  *
  30  * This function is atomic and may not be reordered.  See __set_bit()
  31  * if you do not require the atomic guarantees.
  32  * Note that @nr may be almost arbitrarily large; this function is not
  33  * restricted to acting on a single-word quantity.
  34  */
  35 static __inline__ void set_bit(int nr, volatile void * addr)
  36 {
  37         __asm__ __volatile__( LOCK_PREFIX
  38                 "btsl %1,%0"
  39                 :"=m" (ADDR)
  40                 :"Ir" (nr));
  41 }
  42
  43 /**
  44  * __set_bit - Set a bit in memory
  45  * @nr: the bit to set
  46  * @addr: the address to start counting from
  47  *
  48  * Unlike set_bit(), this function is non-atomic and may be reordered.
  49  * If it's called on the same region of memory simultaneously, the effect
  50  * may be that only one operation succeeds.
  51  */
  52 static __inline__ void __set_bit(int nr, volatile void * addr)
  53 {
  54         __asm__(
  55                 "btsl %1,%0"
  56                 :"=m" (ADDR)
  57                 :"Ir" (nr));
  58 }
  59
  60 /**
  61  * clear_bit - Clears a bit in memory
  62  * @nr: Bit to clear
  63  * @addr: Address to start counting from
  64  *
  65  * clear_bit() is atomic and may not be reordered.  However, it does
  66  * not contain a memory barrier, so if it is used for locking purposes,
  67  * you should call smp_mb__before_clear_bit() and/or smp_mb__after_clear_bit()
  68  * in order to ensure changes are visible on other processors.
  69  */
  70 static __inline__ void clear_bit(int nr, volatile void * addr)
  71 {
  72         __asm__ __volatile__( LOCK_PREFIX
  73                 "btrl %1,%0"
  74                 :"=m" (ADDR)
  75                 :"Ir" (nr));
  76 }
  77 #define smp_mb__before_clear_bit()      barrier()
  78 #define smp_mb__after_clear_bit()       barrier()
  79
  80 /**
  81  * __change_bit - Toggle a bit in memory
  82  * @nr: the bit to set
  83  * @addr: the address to start counting from
  84  *
  85  * Unlike change_bit(), this function is non-atomic and may be reordered.
  86  * If it's called on the same region of memory simultaneously, the effect
  87  * may be that only one operation succeeds.
  88  */
  89 static __inline__ void __change_bit(int nr, volatile void * addr)
  90 {
  91         __asm__ __volatile__(
  92                 "btcl %1,%0"
  93                 :"=m" (ADDR)
  94                 :"Ir" (nr));
  95 }
  96
  97 /**
  98  * change_bit - Toggle a bit in memory
  99  * @nr: Bit to clear
 100  * @addr: Address to start counting from
 101  *
 102  * change_bit() is atomic and may not be reordered.
 103  * Note that @nr may be almost arbitrarily large; this function is not
 104  * restricted to acting on a single-word quantity.
 105  */
 106 static __inline__ void change_bit(int nr, volatile void * addr)
 107 {
 108         __asm__ __volatile__( LOCK_PREFIX
 109                 "btcl %1,%0"
 110                 :"=m" (ADDR)
 111                 :"Ir" (nr));
 112 }
 113
 114 /**
 115  * test_and_set_bit - Set a bit and return its old value
 116  * @nr: Bit to set
 117  * @addr: Address to count from
 118  *
 119  * This operation is atomic and cannot be reordered.
 120  * It also implies a memory barrier.
 121  */
 122 static __inline__ int test_and_set_bit(int nr, volatile void * addr)
 123 {
 124         int oldbit;
 125
 126         __asm__ __volatile__( LOCK_PREFIX
 127                 "btsl %2,%1\n\tsbbl %0,%0"
 128                 :"=r" (oldbit),"=m" (ADDR)
 129                 :"Ir" (nr) : "memory");
 130         return oldbit;
 131 }
 132
 133 /**
 134  * __test_and_set_bit - Set a bit and return its old value
 135  * @nr: Bit to set
 136  * @addr: Address to count from
 137  *
 138  * This operation is non-atomic and can be reordered.
 139  * If two examples of this operation race, one can appear to succeed
 140  * but actually fail.  You must protect multiple accesses with a lock.
 141  */
 142 static __inline__ int __test_and_set_bit(int nr, volatile void * addr)
 143 {
 144         int oldbit;
 145
 146         __asm__(
 147                 "btsl %2,%1\n\tsbbl %0,%0"
 148                 :"=r" (oldbit),"=m" (ADDR)
 149                 :"Ir" (nr));
 150         return oldbit;
 151 }
 152
 153 /**
 154  * test_and_clear_bit - Clear a bit and return its old value
 155  * @nr: Bit to set
 156  * @addr: Address to count from
 157  *
 158  * This operation is atomic and cannot be reordered.
 159  * It also implies a memory barrier.
 160  */
 161 static __inline__ int test_and_clear_bit(int nr, volatile void * addr)
 162 {
 163         int oldbit;
 164
 165         __asm__ __volatile__( LOCK_PREFIX
 166                 "btrl %2,%1\n\tsbbl %0,%0"
 167                 :"=r" (oldbit),"=m" (ADDR)
 168                 :"Ir" (nr) : "memory");
 169         return oldbit;
 170 }
 171
 172 /**
 173  * __test_and_clear_bit - Clear a bit and return its old value
 174  * @nr: Bit to set
 175  * @addr: Address to count from
 176  *
 177  * This operation is non-atomic and can be reordered.
 178  * If two examples of this operation race, one can appear to succeed
 179  * but actually fail.  You must protect multiple accesses with a lock.
 180  */
 181 static __inline__ int __test_and_clear_bit(int nr, volatile void * addr)
 182 {
 183         int oldbit;
 184
 185         __asm__(
 186                 "btrl %2,%1\n\tsbbl %0,%0"
 187                 :"=r" (oldbit),"=m" (ADDR)
 188                 :"Ir" (nr));
 189         return oldbit;
 190 }
 191
 192 /* WARNING: non atomic and it can be reordered! */
 193 static __inline__ int __test_and_change_bit(int nr, volatile void * addr)
 194 {
 195         int oldbit;
 196
 197         __asm__ __volatile__(
 198                 "btcl %2,%1\n\tsbbl %0,%0"
 199                 :"=r" (oldbit),"=m" (ADDR)
 200                 :"Ir" (nr) : "memory");
 201         return oldbit;
 202 }
 203
 204 /**
 205  * test_and_change_bit - Change a bit and return its new value
 206  * @nr: Bit to set
 207  * @addr: Address to count from
 208  *
 209  * This operation is atomic and cannot be reordered.
 210  * It also implies a memory barrier.
 211  */
 212 static __inline__ int test_and_change_bit(int nr, volatile void * addr)
 213 {
 214         int oldbit;
 215
 216         __asm__ __volatile__( LOCK_PREFIX
 217                 "btcl %2,%1\n\tsbbl %0,%0"
 218                 :"=r" (oldbit),"=m" (ADDR)
 219                 :"Ir" (nr) : "memory");
 220         return oldbit;
 221 }
 222
 223 #if 0 /* Fool kernel-doc since it doesn't do macros yet */
 224 /**
 225  * test_bit - Determine whether a bit is set
 226  * @nr: bit number to test
 227  * @addr: Address to start counting from
 228  */
 229 static int test_bit(int nr, const volatile void * addr);
 230 #endif
 231
 232 static __inline__ int constant_test_bit(int nr, const volatile void * addr)
 233 {
 234         return ((1UL << (nr & 31)) & (((const volatile unsigned int *) addr)[nr >> 5])) != 0;
 235 }
 236
 237 static __inline__ int variable_test_bit(int nr, volatile void * addr)
 238 {
 239         int oldbit;
 240
 241         __asm__ __volatile__(
 242                 "btl %2,%1\n\tsbbl %0,%0"
 243                 :"=r" (oldbit)
 244                 :"m" (ADDR),"Ir" (nr));
 245         return oldbit;
 246 }
 247
 248 #define test_bit(nr,addr) \
 249 (__builtin_constant_p(nr) ? \
 250  constant_test_bit((nr),(addr)) : \
 251  variable_test_bit((nr),(addr)))
 252
 253 /**
 254  * find_first_zero_bit - find the first zero bit in a memory region
 255  * @addr: The address to start the search at
 256  * @size: The maximum size to search
 257  *
 258  * Returns the bit-number of the first zero bit, not the number of the byte
 259  * containing a bit.
 260  */
 261 static __inline__ int find_first_zero_bit(void * addr, unsigned size)
 262 {
 263         int d0, d1, d2;
 264         int res;
 265
 266         if (!size)
 267                 return 0;
 268         /* This looks at memory. Mark it volatile to tell gcc not to move it around */
 269         __asm__ __volatile__(
 270                 "movl $-1,%%eax\n\t"
 271                 "xorl %%edx,%%edx\n\t"
 272                 "repe; scasl\n\t"
 273                 "je 1f\n\t"
 274                 "xorl -4(%%edi),%%eax\n\t"
 275                 "subl $4,%%edi\n\t"
 276                 "bsfl %%eax,%%edx\n"
 277                 "1:\tsubl %%ebx,%%edi\n\t"
 278                 "shll $3,%%edi\n\t"
 279                 "addl %%edi,%%edx"
 280                 :"=d" (res), "=&c" (d0), "=&D" (d1), "=&a" (d2)
 281                 :"1" ((size + 31) >> 5), "2" (addr), "b" (addr));
 282         return res;
 283 }
 284
 285 /**
 286  * find_next_zero_bit - find the first zero bit in a memory region
 287  * @addr: The address to base the search on
 288  * @offset: The bitnumber to start searching at
 289  * @size: The maximum size to search
 290  */
 291 static __inline__ int find_next_zero_bit (void * addr, int size, int offset)
 292 {
 293         unsigned long * p = ((unsigned long *) addr) + (offset >> 5);
 294         int set = 0, bit = offset & 31, res;
 295
 296         if (bit) {
 297                 /*
 298                  * Look for zero in first byte
 299                  */
 300                 __asm__("bsfl %1,%0\n\t"
 301                         "jne 1f\n\t"
 302                         "movl $32, %0\n"
 303                         "1:"
 304                         : "=r" (set)
 305                         : "r" (~(*p >> bit)));
 306                 if (set < (32 - bit))
 307                         return set + offset;
 308                 set = 32 - bit;
 309                 p++;
 310         }
 311         /*
 312          * No zero yet, search remaining full bytes for a zero
 313          */
 314         res = find_first_zero_bit (p, size - 32 * (p - (unsigned long *) addr));
 315         return (offset + set + res);
 316 }
 317
 318 /**
 319  * ffz - find first zero in word.
 320  * @word: The word to search
 321  *
 322  * Undefined if no zero exists, so code should check against ~0UL first.
 323  */
 324 static __inline__ unsigned long ffz(unsigned long word)
 325 {
 326         __asm__("bsfl %1,%0"
 327                 :"=r" (word)
 328                 :"r" (~word));
 329         return word;
 330 }
 331
 332 #ifdef __KERNEL__
 333
 334 /**
 335  * ffs - find first bit set
 336  * @x: the word to search
 337  *
 338  * This is defined the same way as
 339  * the libc and compiler builtin ffs routines, therefore
 340  * differs in spirit from the above ffz (man ffs).
 341  */
 342 static __inline__ int ffs(int x)
 343 {
 344         int r;
 345
 346         __asm__("bsfl %1,%0\n\t"
 347                 "jnz 1f\n\t"
 348                 "movl $-1,%0\n"
 349                 "1:" : "=r" (r) : "g" (x));
 350         return r+1;
 351 }
 352
 353 /**
 354  * hweightN - returns the hamming weight of a N-bit word
 355  * @x: the word to weigh
 356  *
 357  * The Hamming Weight of a number is the total number of bits set in it.
 358  */
 359
 360 #define hweight32(x) generic_hweight32(x)
 361 #define hweight16(x) generic_hweight16(x)
 362 #define hweight8(x) generic_hweight8(x)
 363
 364 #endif /* __KERNEL__ */
 365
 366 #ifdef __KERNEL__
 367
 368 #define ext2_set_bit                 __test_and_set_bit
 369 #define ext2_clear_bit               __test_and_clear_bit
 370 #define ext2_test_bit                test_bit
 371 #define ext2_find_first_zero_bit     find_first_zero_bit
 372 #define ext2_find_next_zero_bit      find_next_zero_bit
 373
 374 /* Bitmap functions for the minix filesystem.  */
 375 #define minix_test_and_set_bit(nr,addr) __test_and_set_bit(nr,addr)
 376 #define minix_set_bit(nr,addr) __set_bit(nr,addr)
 377 #define minix_test_and_clear_bit(nr,addr) __test_and_clear_bit(nr,addr)
 378 #define minix_test_bit(nr,addr) test_bit(nr,addr)
 379 #define minix_find_first_zero_bit(addr,size) find_first_zero_bit(addr,size)
 380
 381 #endif /* __KERNEL__ */
 382
 383 #endif /* _I386_BITOPS_H */