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lib/bitmap.c: conversion routines to/from u32 array

Browse Source 
Aimed at transferring bitmaps to/from user-space in a 32/64-bit agnostic
way.

Tested:
  unit tests (next patch) on qemu i386, x86_64, ppc, ppc64 BE and LE,
  ARM.

Signed-off-by: David Decotigny <decot@googlers.com>
Reviewed-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David Decotigny 2016-02-19 09:23:59 -05:00 committed by David S. Miller
parent 76d13b5687
commit e52bc7c28a
2 changed files with 99 additions and 0 deletions
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10
include/linux/bitmap.h
View File

@ -59,6 +59,8 @@
* bitmap_find_free_region(bitmap, bits, order) Find and allocate bit region
* bitmap_release_region(bitmap, pos, order) Free specified bit region
* bitmap_allocate_region(bitmap, pos, order) Allocate specified bit region
* bitmap_from_u32array(dst, nbits, buf, nwords) *dst = *buf (nwords 32b words)
* bitmap_to_u32array(buf, nwords, src, nbits) *buf = *dst (nwords 32b words)
*/
/*
@ -163,6 +165,14 @@ extern void bitmap_fold(unsigned long *dst, const unsigned long *orig,
extern int bitmap_find_free_region(unsigned long *bitmap, unsigned int bits, int order);
extern void bitmap_release_region(unsigned long *bitmap, unsigned int pos, int order);
extern int bitmap_allocate_region(unsigned long *bitmap, unsigned int pos, int order);
extern unsigned int bitmap_from_u32array(unsigned long *bitmap,
unsigned int nbits,
const u32 *buf,
unsigned int nwords);
extern unsigned int bitmap_to_u32array(u32 *buf,
unsigned int nwords,
const unsigned long *bitmap,
unsigned int nbits);
#ifdef __BIG_ENDIAN
extern void bitmap_copy_le(unsigned long *dst, const unsigned long *src, unsigned int nbits);
#else

89
lib/bitmap.c
View File

@ -12,6 +12,8 @@
#include <linux/bitmap.h>
#include <linux/bitops.h>
#include <linux/bug.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <asm/page.h>
#include <asm/uaccess.h>
@ -1059,6 +1061,93 @@ int bitmap_allocate_region(unsigned long *bitmap, unsigned int pos, int order)
}
EXPORT_SYMBOL(bitmap_allocate_region);
/**
* bitmap_from_u32array - copy the contents of a u32 array of bits to bitmap
* @bitmap: array of unsigned longs, the destination bitmap, non NULL
* @nbits: number of bits in @bitmap
* @buf: array of u32 (in host byte order), the source bitmap, non NULL
* @nwords: number of u32 words in @buf
*
* copy min(nbits, 32*nwords) bits from @buf to @bitmap, remaining
* bits between nword and nbits in @bitmap (if any) are cleared. In
* last word of @bitmap, the bits beyond nbits (if any) are kept
* unchanged.
*
* Return the number of bits effectively copied.
*/
unsigned int
bitmap_from_u32array(unsigned long *bitmap, unsigned int nbits,
const u32 *buf, unsigned int nwords)
{
unsigned int dst_idx, src_idx;
for (src_idx = dst_idx = 0; dst_idx < BITS_TO_LONGS(nbits); ++dst_idx) {
unsigned long part = 0;
if (src_idx < nwords)
part = buf[src_idx++];
#if BITS_PER_LONG == 64
if (src_idx < nwords)
part |= ((unsigned long) buf[src_idx++]) << 32;
#endif
if (dst_idx < nbits/BITS_PER_LONG)
bitmap[dst_idx] = part;
else {
unsigned long mask = BITMAP_LAST_WORD_MASK(nbits);
bitmap[dst_idx] = (bitmap[dst_idx] & ~mask)
| (part & mask);
}
}
return min_t(unsigned int, nbits, 32*nwords);
}
EXPORT_SYMBOL(bitmap_from_u32array);
/**
* bitmap_to_u32array - copy the contents of bitmap to a u32 array of bits
* @buf: array of u32 (in host byte order), the dest bitmap, non NULL
* @nwords: number of u32 words in @buf
* @bitmap: array of unsigned longs, the source bitmap, non NULL
* @nbits: number of bits in @bitmap
*
* copy min(nbits, 32*nwords) bits from @bitmap to @buf. Remaining
* bits after nbits in @buf (if any) are cleared.
*
* Return the number of bits effectively copied.
*/
unsigned int
bitmap_to_u32array(u32 *buf, unsigned int nwords,
const unsigned long *bitmap, unsigned int nbits)
{
unsigned int dst_idx = 0, src_idx = 0;
while (dst_idx < nwords) {
unsigned long part = 0;
if (src_idx < BITS_TO_LONGS(nbits)) {
part = bitmap[src_idx];
if (src_idx >= nbits/BITS_PER_LONG)
part &= BITMAP_LAST_WORD_MASK(nbits);
src_idx++;
}
buf[dst_idx++] = part & 0xffffffffUL;
#if BITS_PER_LONG == 64
if (dst_idx < nwords) {
part >>= 32;
buf[dst_idx++] = part & 0xffffffffUL;
}
#endif
}
return min_t(unsigned int, nbits, 32*nwords);
}
EXPORT_SYMBOL(bitmap_to_u32array);
/**
* bitmap_copy_le - copy a bitmap, putting the bits into little-endian order.
* @dst: destination buffer