mirror of
https://github.com/reactos/reactos.git
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204 lines
4.7 KiB
C
204 lines
4.7 KiB
C
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/*
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* ReactOS kernel
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/*
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* Copyright 1992, Linus Torvalds.
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*/
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/*
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* These have to be done with inline assembly: that way the bit-setting
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* is guaranteed to be atomic. All bit operations return 0 if the bit
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* was cleared before the operation and != 0 if it was not.
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*
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* bit 0 is the LSB of addr; bit 32 is the LSB of (addr+1).
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*/
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#ifdef __SMP__
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#define LOCK_PREFIX "lock ; "
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#else
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#define LOCK_PREFIX ""
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#endif
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/*
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* Function prototypes to keep gcc -Wall happy
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*/
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extern void set_bit(int nr, volatile void * addr);
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extern void clear_bit(int nr, volatile void * addr);
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extern void change_bit(int nr, volatile void * addr);
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extern int test_and_set_bit(int nr, volatile void * addr);
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extern int test_and_clear_bit(int nr, volatile void * addr);
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extern int test_and_change_bit(int nr, volatile void * addr);
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extern int __constant_test_bit(int nr, const volatile void * addr);
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extern int __test_bit(int nr, volatile void * addr);
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extern int find_first_zero_bit(void * addr, unsigned size);
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extern int find_next_zero_bit (void * addr, int size, int offset);
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extern unsigned long ffz(unsigned long word);
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/*
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* Some hacks to defeat gcc over-optimizations..
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*/
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struct __dummy { unsigned long a[100]; };
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#define ADDR (*(volatile struct __dummy *) addr)
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#define CONST_ADDR (*(volatile const struct __dummy *) addr)
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void set_bit(int nr, volatile void * addr)
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{
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__asm__ __volatile__( LOCK_PREFIX
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"btsl %1,%0"
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:"=m" (ADDR)
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:"Ir" (nr));
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}
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void clear_bit(int nr, volatile void * addr)
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{
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__asm__ __volatile__( LOCK_PREFIX
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"btrl %1,%0"
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:"=m" (ADDR)
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:"Ir" (nr));
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}
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void change_bit(int nr, volatile void * addr)
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{
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__asm__ __volatile__( LOCK_PREFIX
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"btcl %1,%0"
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:"=m" (ADDR)
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:"Ir" (nr));
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}
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int test_and_set_bit(int nr, volatile void * addr)
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{
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int oldbit;
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__asm__ __volatile__( LOCK_PREFIX
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"btsl %2,%1\n\tsbbl %0,%0"
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:"=r" (oldbit),"=m" (ADDR)
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:"Ir" (nr));
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return oldbit;
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}
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int test_and_clear_bit(int nr, volatile void * addr)
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{
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int oldbit;
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__asm__ __volatile__( LOCK_PREFIX
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"btrl %2,%1\n\tsbbl %0,%0"
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:"=r" (oldbit),"=m" (ADDR)
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:"Ir" (nr));
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return oldbit;
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}
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int test_and_change_bit(int nr, volatile void * addr)
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{
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int oldbit;
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__asm__ __volatile__( LOCK_PREFIX
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"btcl %2,%1\n\tsbbl %0,%0"
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:"=r" (oldbit),"=m" (ADDR)
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:"Ir" (nr));
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return oldbit;
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}
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/*
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* This routine doesn't need to be atomic.
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*/
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int __constant_test_bit(int nr, const volatile void * addr)
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{
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return ((1UL << (nr & 31)) & (((const volatile unsigned int *) addr)[nr >> 5])) != 0;
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}
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int test_bit(int nr, volatile void * addr)
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{
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int oldbit;
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__asm__ __volatile__(
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"btl %2,%1\n\tsbbl %0,%0"
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:"=r" (oldbit)
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:"m" (ADDR),"Ir" (nr));
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return oldbit;
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}
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#if 0
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#define test_bit(nr,addr) \
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(__builtin_constant_p(nr) ? \
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__constant_test_bit((nr),(addr)) : \
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__test_bit((nr),(addr)))
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#endif
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/*
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* Find-bit routines..
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*/
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int find_first_zero_bit(void * addr, unsigned size)
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{
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int d0, d1, d2;
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int res;
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if (!size)
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return 0;
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__asm__("cld\n\t"
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"movl $-1,%%eax\n\t"
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"xorl %%edx,%%edx\n\t"
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"repe; scasl\n\t"
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"je 1f\n\t"
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"xorl -4(%%edi),%%eax\n\t"
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"subl $4,%%edi\n\t"
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"bsfl %%eax,%%edx\n"
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"1:\tsubl %%ebx,%%edi\n\t"
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"shll $3,%%edi\n\t"
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"addl %%edi,%%edx"
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:"=d" (res), "=&c" (d0), "=&D" (d1), "=&a" (d2)
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:"1" ((size + 31) >> 5), "2" (addr), "b" (addr));
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return res;
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}
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int find_next_zero_bit (void * addr, int size, int offset)
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{
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unsigned long * p = ((unsigned long *) addr) + (offset >> 5);
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int set = 0, bit = offset & 31, res;
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if (bit) {
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/*
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* Look for zero in first byte
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*/
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__asm__("bsfl %1,%0\n\t"
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"jne 1f\n\t"
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"movl $32, %0\n"
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"1:"
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: "=r" (set)
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: "r" (~(*p >> bit)));
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if (set < (32 - bit))
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return set + offset;
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set = 32 - bit;
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p++;
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}
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/*
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* No zero yet, search remaining full bytes for a zero
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*/
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res = find_first_zero_bit (p, size - 32 * (p - (unsigned long *) addr));
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return (offset + set + res);
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}
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/*
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* ffz = Find First Zero in word. Undefined if no zero exists,
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* so code should check against ~0UL first..
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*/
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unsigned long ffz(unsigned long word)
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{
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__asm__("bsfl %1,%0"
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:"=r" (word)
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:"r" (~word));
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return word;
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}
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