176 строки
4.4 KiB
C
176 строки
4.4 KiB
C
#include <linux/bitops.h>
|
|
|
|
#undef find_first_zero_bit
|
|
#undef find_next_zero_bit
|
|
#undef find_first_bit
|
|
#undef find_next_bit
|
|
|
|
static inline long
|
|
__find_first_zero_bit(const unsigned long * addr, unsigned long size)
|
|
{
|
|
long d0, d1, d2;
|
|
long res;
|
|
|
|
/*
|
|
* We must test the size in words, not in bits, because
|
|
* otherwise incoming sizes in the range -63..-1 will not run
|
|
* any scasq instructions, and then the flags used by the je
|
|
* instruction will have whatever random value was in place
|
|
* before. Nobody should call us like that, but
|
|
* find_next_zero_bit() does when offset and size are at the
|
|
* same word and it fails to find a zero itself.
|
|
*/
|
|
size += 63;
|
|
size >>= 6;
|
|
if (!size)
|
|
return 0;
|
|
asm volatile(
|
|
" repe; scasq\n"
|
|
" je 1f\n"
|
|
" xorq -8(%%rdi),%%rax\n"
|
|
" subq $8,%%rdi\n"
|
|
" bsfq %%rax,%%rdx\n"
|
|
"1: subq %[addr],%%rdi\n"
|
|
" shlq $3,%%rdi\n"
|
|
" addq %%rdi,%%rdx"
|
|
:"=d" (res), "=&c" (d0), "=&D" (d1), "=&a" (d2)
|
|
:"0" (0ULL), "1" (size), "2" (addr), "3" (-1ULL),
|
|
[addr] "S" (addr) : "memory");
|
|
/*
|
|
* Any register would do for [addr] above, but GCC tends to
|
|
* prefer rbx over rsi, even though rsi is readily available
|
|
* and doesn't have to be saved.
|
|
*/
|
|
return res;
|
|
}
|
|
|
|
/**
|
|
* find_first_zero_bit - find the first zero bit in a memory region
|
|
* @addr: The address to start the search at
|
|
* @size: The maximum size to search
|
|
*
|
|
* Returns the bit-number of the first zero bit, not the number of the byte
|
|
* containing a bit.
|
|
*/
|
|
long find_first_zero_bit(const unsigned long * addr, unsigned long size)
|
|
{
|
|
return __find_first_zero_bit (addr, size);
|
|
}
|
|
|
|
/**
|
|
* find_next_zero_bit - find the first zero bit in a memory region
|
|
* @addr: The address to base the search on
|
|
* @offset: The bitnumber to start searching at
|
|
* @size: The maximum size to search
|
|
*/
|
|
long find_next_zero_bit (const unsigned long * addr, long size, long offset)
|
|
{
|
|
const unsigned long * p = addr + (offset >> 6);
|
|
unsigned long set = 0;
|
|
unsigned long res, bit = offset&63;
|
|
|
|
if (bit) {
|
|
/*
|
|
* Look for zero in first word
|
|
*/
|
|
asm("bsfq %1,%0\n\t"
|
|
"cmoveq %2,%0"
|
|
: "=r" (set)
|
|
: "r" (~(*p >> bit)), "r"(64L));
|
|
if (set < (64 - bit))
|
|
return set + offset;
|
|
set = 64 - bit;
|
|
p++;
|
|
}
|
|
/*
|
|
* No zero yet, search remaining full words for a zero
|
|
*/
|
|
res = __find_first_zero_bit (p, size - 64 * (p - addr));
|
|
|
|
return (offset + set + res);
|
|
}
|
|
|
|
static inline long
|
|
__find_first_bit(const unsigned long * addr, unsigned long size)
|
|
{
|
|
long d0, d1;
|
|
long res;
|
|
|
|
/*
|
|
* We must test the size in words, not in bits, because
|
|
* otherwise incoming sizes in the range -63..-1 will not run
|
|
* any scasq instructions, and then the flags used by the jz
|
|
* instruction will have whatever random value was in place
|
|
* before. Nobody should call us like that, but
|
|
* find_next_bit() does when offset and size are at the same
|
|
* word and it fails to find a one itself.
|
|
*/
|
|
size += 63;
|
|
size >>= 6;
|
|
if (!size)
|
|
return 0;
|
|
asm volatile(
|
|
" repe; scasq\n"
|
|
" jz 1f\n"
|
|
" subq $8,%%rdi\n"
|
|
" bsfq (%%rdi),%%rax\n"
|
|
"1: subq %[addr],%%rdi\n"
|
|
" shlq $3,%%rdi\n"
|
|
" addq %%rdi,%%rax"
|
|
:"=a" (res), "=&c" (d0), "=&D" (d1)
|
|
:"0" (0ULL), "1" (size), "2" (addr),
|
|
[addr] "r" (addr) : "memory");
|
|
return res;
|
|
}
|
|
|
|
/**
|
|
* find_first_bit - find the first set bit in a memory region
|
|
* @addr: The address to start the search at
|
|
* @size: The maximum size to search
|
|
*
|
|
* Returns the bit-number of the first set bit, not the number of the byte
|
|
* containing a bit.
|
|
*/
|
|
long find_first_bit(const unsigned long * addr, unsigned long size)
|
|
{
|
|
return __find_first_bit(addr,size);
|
|
}
|
|
|
|
/**
|
|
* find_next_bit - find the first set bit in a memory region
|
|
* @addr: The address to base the search on
|
|
* @offset: The bitnumber to start searching at
|
|
* @size: The maximum size to search
|
|
*/
|
|
long find_next_bit(const unsigned long * addr, long size, long offset)
|
|
{
|
|
const unsigned long * p = addr + (offset >> 6);
|
|
unsigned long set = 0, bit = offset & 63, res;
|
|
|
|
if (bit) {
|
|
/*
|
|
* Look for nonzero in the first 64 bits:
|
|
*/
|
|
asm("bsfq %1,%0\n\t"
|
|
"cmoveq %2,%0\n\t"
|
|
: "=r" (set)
|
|
: "r" (*p >> bit), "r" (64L));
|
|
if (set < (64 - bit))
|
|
return set + offset;
|
|
set = 64 - bit;
|
|
p++;
|
|
}
|
|
/*
|
|
* No set bit yet, search remaining full words for a bit
|
|
*/
|
|
res = __find_first_bit (p, size - 64 * (p - addr));
|
|
return (offset + set + res);
|
|
}
|
|
|
|
#include <linux/module.h>
|
|
|
|
EXPORT_SYMBOL(find_next_bit);
|
|
EXPORT_SYMBOL(find_first_bit);
|
|
EXPORT_SYMBOL(find_first_zero_bit);
|
|
EXPORT_SYMBOL(find_next_zero_bit);
|