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18e776a6c1
mainly to get control over new features. E.g., ext2fs filesystems may now have a type field in directory entries (like ufs has had for 20 years or so). Current versions of FreeBSD ext2fs panic on this. ext2fs filesystem code is supposed to check the feature flags in the superblock and take appropriate actions for unsupported features. The other new features are sparse superblocks, large file support, and btree'd directories.
162 lines
3.4 KiB
C
162 lines
3.4 KiB
C
/* $FreeBSD$ */
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/*
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* this is mixture of i386/bitops.h and asm/string.h
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* taken from the Linux source tree
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*
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* XXX replace with Mach routines or reprogram in C
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*/
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#ifndef _SYS_GNU_EXT2FS_I386_BITOPS_H_
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#define _SYS_GNU_EXT2FS_I386_BITOPS_H_
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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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/*
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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 (*(struct __dummy *) addr)
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static __inline__ int set_bit(int nr, void * addr)
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{
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int oldbit;
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__asm__ __volatile__("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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static __inline__ int clear_bit(int nr, void * addr)
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{
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int oldbit;
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__asm__ __volatile__("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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static __inline__ int change_bit(int nr, void * addr)
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{
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int oldbit;
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__asm__ __volatile__("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, but it's faster to code it
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* this way.
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*/
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static __inline__ int test_bit(int nr, void * addr)
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{
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int oldbit;
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__asm__ __volatile__("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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/*
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* Find-bit routines..
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*/
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static __inline__ int find_first_zero_bit(void * addr, unsigned size)
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{
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int res;
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int _count = (size + 31) >> 5;
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if (!size)
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return 0;
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__asm__(" \n\
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cld \n\
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movl $-1,%%eax \n\
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xorl %%edx,%%edx \n\
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repe; scasl \n\
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je 1f \n\
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xorl -4(%%edi),%%eax \n\
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subl $4,%%edi \n\
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bsfl %%eax,%%edx \n\
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1: subl %%ebx,%%edi \n\
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shll $3,%%edi \n\
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addl %%edi,%%edx"
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: "=c" (_count), "=D" (addr), "=d" (res)
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: "0" (_count), "1" (addr), "b" (addr)
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: "ax");
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return res;
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}
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static __inline__ 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__(" \n\
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bsfl %1,%0 \n\
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jne 1f \n\
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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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static __inline__ 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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/*
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* memscan() taken from linux asm/string.h
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*/
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/*
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* find the first occurrence of byte 'c', or 1 past the area if none
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*/
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static __inline__ char * memscan(void * addr, unsigned char c, int size)
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{
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if (!size)
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return addr;
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__asm__(" \n\
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cld \n\
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repnz; scasb \n\
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jnz 1f \n\
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dec %%edi \n\
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1: "
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: "=D" (addr), "=c" (size)
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: "0" (addr), "1" (size), "a" (c));
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return addr;
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}
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#endif /* !_SYS_GNU_EXT2FS_I386_BITOPS_H_ */
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