linux-stable/tools/include/linux/hash.h
Ingo Molnar fb7df12d64 tools/headers: Synchronize kernel ABI headers
After the SPDX license tags were added a number of tooling headers got out of
sync with their kernel variants, generating lots of build warnings.

Sync them:

 - tools/arch/x86/include/asm/disabled-features.h,
   tools/arch/x86/include/asm/required-features.h,
   tools/include/linux/hash.h:

     Remove the SPDX tag where the kernel version does not have it.

 - tools/include/asm-generic/bitops/__fls.h,
   tools/include/asm-generic/bitops/arch_hweight.h,
   tools/include/asm-generic/bitops/const_hweight.h,
   tools/include/asm-generic/bitops/fls.h,
   tools/include/asm-generic/bitops/fls64.h,
   tools/include/uapi/asm-generic/ioctls.h,
   tools/include/uapi/asm-generic/mman-common.h,
   tools/include/uapi/sound/asound.h,
   tools/include/uapi/linux/kvm.h,
   tools/include/uapi/linux/perf_event.h,
   tools/include/uapi/linux/sched.h,
   tools/include/uapi/linux/vhost.h,
   tools/include/uapi/sound/asound.h:

     Add the SPDX tag of the respective kernel header.

 - tools/include/uapi/linux/bpf_common.h,
   tools/include/uapi/linux/fcntl.h,
   tools/include/uapi/linux/hw_breakpoint.h,
   tools/include/uapi/linux/mman.h,
   tools/include/uapi/linux/stat.h,

     Change the tag to the kernel header version:

       -/* SPDX-License-Identifier: GPL-2.0 */
       +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */

Also sync other header details:

 - include/uapi/sound/asound.h:

     Fix pointless end of line whitespace noise the header grew in this cycle.

 - tools/arch/x86/lib/memcpy_64.S:

     Sync the code and add tools/include/asm/export.h with dummy wrappers
     to support building the kernel side code in a tooling header environment.

 - tools/include/uapi/asm-generic/mman.h,
   tools/include/uapi/linux/bpf.h:

     Sync other details that don't impact tooling's use of the ABIs.

Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-11-04 09:27:46 +01:00

104 lines
3 KiB
C

#ifndef _LINUX_HASH_H
#define _LINUX_HASH_H
/* Fast hashing routine for ints, longs and pointers.
(C) 2002 Nadia Yvette Chambers, IBM */
#include <asm/types.h>
#include <linux/compiler.h>
/*
* The "GOLDEN_RATIO_PRIME" is used in ifs/btrfs/brtfs_inode.h and
* fs/inode.c. It's not actually prime any more (the previous primes
* were actively bad for hashing), but the name remains.
*/
#if BITS_PER_LONG == 32
#define GOLDEN_RATIO_PRIME GOLDEN_RATIO_32
#define hash_long(val, bits) hash_32(val, bits)
#elif BITS_PER_LONG == 64
#define hash_long(val, bits) hash_64(val, bits)
#define GOLDEN_RATIO_PRIME GOLDEN_RATIO_64
#else
#error Wordsize not 32 or 64
#endif
/*
* This hash multiplies the input by a large odd number and takes the
* high bits. Since multiplication propagates changes to the most
* significant end only, it is essential that the high bits of the
* product be used for the hash value.
*
* Chuck Lever verified the effectiveness of this technique:
* http://www.citi.umich.edu/techreports/reports/citi-tr-00-1.pdf
*
* Although a random odd number will do, it turns out that the golden
* ratio phi = (sqrt(5)-1)/2, or its negative, has particularly nice
* properties. (See Knuth vol 3, section 6.4, exercise 9.)
*
* These are the negative, (1 - phi) = phi**2 = (3 - sqrt(5))/2,
* which is very slightly easier to multiply by and makes no
* difference to the hash distribution.
*/
#define GOLDEN_RATIO_32 0x61C88647
#define GOLDEN_RATIO_64 0x61C8864680B583EBull
#ifdef CONFIG_HAVE_ARCH_HASH
/* This header may use the GOLDEN_RATIO_xx constants */
#include <asm/hash.h>
#endif
/*
* The _generic versions exist only so lib/test_hash.c can compare
* the arch-optimized versions with the generic.
*
* Note that if you change these, any <asm/hash.h> that aren't updated
* to match need to have their HAVE_ARCH_* define values updated so the
* self-test will not false-positive.
*/
#ifndef HAVE_ARCH__HASH_32
#define __hash_32 __hash_32_generic
#endif
static inline u32 __hash_32_generic(u32 val)
{
return val * GOLDEN_RATIO_32;
}
#ifndef HAVE_ARCH_HASH_32
#define hash_32 hash_32_generic
#endif
static inline u32 hash_32_generic(u32 val, unsigned int bits)
{
/* High bits are more random, so use them. */
return __hash_32(val) >> (32 - bits);
}
#ifndef HAVE_ARCH_HASH_64
#define hash_64 hash_64_generic
#endif
static __always_inline u32 hash_64_generic(u64 val, unsigned int bits)
{
#if BITS_PER_LONG == 64
/* 64x64-bit multiply is efficient on all 64-bit processors */
return val * GOLDEN_RATIO_64 >> (64 - bits);
#else
/* Hash 64 bits using only 32x32-bit multiply. */
return hash_32((u32)val ^ __hash_32(val >> 32), bits);
#endif
}
static inline u32 hash_ptr(const void *ptr, unsigned int bits)
{
return hash_long((unsigned long)ptr, bits);
}
/* This really should be called fold32_ptr; it does no hashing to speak of. */
static inline u32 hash32_ptr(const void *ptr)
{
unsigned long val = (unsigned long)ptr;
#if BITS_PER_LONG == 64
val ^= (val >> 32);
#endif
return (u32)val;
}
#endif /* _LINUX_HASH_H */