lib/string.c: add multibyte memset functions

Patch series "Multibyte memset variations", v4.

A relatively common idiom we're missing is a function to fill an area of
memory with a pattern which is larger than a single byte.  I first
noticed this with a zram patch which wanted to fill a page with an
'unsigned long' value.  There turn out to be quite a few places in the
kernel which can benefit from using an optimised function rather than a
loop; sometimes text size, sometimes speed, and sometimes both.  The
optimised PowerPC version (not included here) improves performance by
about 30% on POWER8 on just the raw memset_l().

Most of the extra lines of code come from the three testcases I added.

This patch (of 8):

memset16(), memset32() and memset64() are like memset(), but allow the
caller to fill the destination with a value larger than a single byte.
memset_l() and memset_p() allow the caller to use unsigned long and
pointer values respectively.

Link: http://lkml.kernel.org/r/20170720184539.31609-2-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: David Miller <davem@davemloft.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Russell King <rmk+kernel@armlinux.org.uk>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Matthew Wilcox 2017-09-08 16:13:48 -07:00 committed by Linus Torvalds
parent 604df32236
commit 3b3c4babd8
2 changed files with 96 additions and 0 deletions

View file

@ -99,6 +99,36 @@ extern __kernel_size_t strcspn(const char *,const char *);
#ifndef __HAVE_ARCH_MEMSET
extern void * memset(void *,int,__kernel_size_t);
#endif
#ifndef __HAVE_ARCH_MEMSET16
extern void *memset16(uint16_t *, uint16_t, __kernel_size_t);
#endif
#ifndef __HAVE_ARCH_MEMSET32
extern void *memset32(uint32_t *, uint32_t, __kernel_size_t);
#endif
#ifndef __HAVE_ARCH_MEMSET64
extern void *memset64(uint64_t *, uint64_t, __kernel_size_t);
#endif
static inline void *memset_l(unsigned long *p, unsigned long v,
__kernel_size_t n)
{
if (BITS_PER_LONG == 32)
return memset32((uint32_t *)p, v, n);
else
return memset64((uint64_t *)p, v, n);
}
static inline void *memset_p(void **p, void *v, __kernel_size_t n)
{
if (BITS_PER_LONG == 32)
return memset32((uint32_t *)p, (uintptr_t)v, n);
else
return memset64((uint64_t *)p, (uintptr_t)v, n);
}
#ifndef __HAVE_ARCH_MEMCPY
extern void * memcpy(void *,const void *,__kernel_size_t);
#endif

View file

@ -723,6 +723,72 @@ void memzero_explicit(void *s, size_t count)
}
EXPORT_SYMBOL(memzero_explicit);
#ifndef __HAVE_ARCH_MEMSET16
/**
* memset16() - Fill a memory area with a uint16_t
* @s: Pointer to the start of the area.
* @v: The value to fill the area with
* @count: The number of values to store
*
* Differs from memset() in that it fills with a uint16_t instead
* of a byte. Remember that @count is the number of uint16_ts to
* store, not the number of bytes.
*/
void *memset16(uint16_t *s, uint16_t v, size_t count)
{
uint16_t *xs = s;
while (count--)
*xs++ = v;
return s;
}
EXPORT_SYMBOL(memset16);
#endif
#ifndef __HAVE_ARCH_MEMSET32
/**
* memset32() - Fill a memory area with a uint32_t
* @s: Pointer to the start of the area.
* @v: The value to fill the area with
* @count: The number of values to store
*
* Differs from memset() in that it fills with a uint32_t instead
* of a byte. Remember that @count is the number of uint32_ts to
* store, not the number of bytes.
*/
void *memset32(uint32_t *s, uint32_t v, size_t count)
{
uint32_t *xs = s;
while (count--)
*xs++ = v;
return s;
}
EXPORT_SYMBOL(memset32);
#endif
#ifndef __HAVE_ARCH_MEMSET64
/**
* memset64() - Fill a memory area with a uint64_t
* @s: Pointer to the start of the area.
* @v: The value to fill the area with
* @count: The number of values to store
*
* Differs from memset() in that it fills with a uint64_t instead
* of a byte. Remember that @count is the number of uint64_ts to
* store, not the number of bytes.
*/
void *memset64(uint64_t *s, uint64_t v, size_t count)
{
uint64_t *xs = s;
while (count--)
*xs++ = v;
return s;
}
EXPORT_SYMBOL(memset64);
#endif
#ifndef __HAVE_ARCH_MEMCPY
/**
* memcpy - Copy one area of memory to another