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Commit 468a9428 authored by George Spelvin's avatar George Spelvin
Browse files

<linux/hash.h>: Add support for architecture-specific functions 



This is just the infrastructure; there are no users yet.

This is modelled on CONFIG_ARCH_RANDOM; a CONFIG_ symbol declares
the existence of <asm/hash.h>.

That file may define its own versions of various functions, and define
HAVE_* symbols (no CONFIG_ prefix!) to suppress the generic ones.

Included is a self-test (in lib/test_hash.c) that verifies the basics.
It is NOT in general required that the arch-specific functions compute
the same thing as the generic, but if a HAVE_* symbol is defined with
the value 1, then equality is tested.

Signed-off-by: default avatarGeorge Spelvin <linux@sciencehorizons.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greg Ungerer <gerg@linux-m68k.org>
Cc: Andreas Schwab <schwab@linux-m68k.org>
Cc: Philippe De Muyter <phdm@macq.eu>
Cc: linux-m68k@lists.linux-m68k.org
Cc: Alistair Francis <alistai@xilinx.com>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: uclinux-h8-devel@lists.sourceforge.jp
parent 2a18da7a

arch/Kconfig

+8 −0
Original line number Diff line number Diff line
@@ -589,6 +589,14 @@ config HAVE_STACK_VALIDATION 
	  Architecture supports the 'objtool check' host tool command, which

	  performs compile-time stack metadata validation.



config HAVE_ARCH_HASH

	bool

	default n

	help

	  If this is set, the architecture provides an <asm/hash.h>

	  file which provides platform-specific implementations of some

	  functions in <linux/hash.h> or fs/namei.c.



#

# ABI hall of shame

#

fs/namei.c

+5 −1
Original line number Diff line number Diff line
@@ -1788,7 +1788,11 @@ static int walk_component(struct nameidata *nd, int flags) 


#include <asm/word-at-a-time.h>



#ifdef CONFIG_64BIT

#ifdef HASH_MIX



/* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */



#elif defined(CONFIG_64BIT)

/*

 * Register pressure in the mixing function is an issue, particularly

 * on 32-bit x86, but almost any function requires one state value and

include/linux/hash.h

+24 −3
Original line number Diff line number Diff line
@@ -41,19 +41,40 @@ 
#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



static inline u32 __hash_32(u32 val)

/*

 * 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;

}



static inline u32 hash_32(u32 val, unsigned int bits)

#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);

}



static __always_inline u32 hash_64(u64 val, unsigned int 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 */

lib/Kconfig.debug

+11 −0
Original line number Diff line number Diff line
@@ -1815,6 +1815,17 @@ config TEST_RHASHTABLE 


	  If unsure, say N.



config TEST_HASH

	tristate "Perform selftest on hash functions"

	default n

	help

	  Enable this option to test the kernel's integer (<linux/hash,h>)

	  and string (<linux/stringhash.h>) hash functions on boot

	  (or module load).



	  This is intended to help people writing architecture-specific

	  optimized versions.  If unsure, say N.



endmenu # runtime tests



config PROVIDE_OHCI1394_DMA_INIT

lib/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -48,6 +48,7 @@ obj-$(CONFIG_TEST_HEXDUMP) += test_hexdump.o 
obj-y += kstrtox.o

obj-$(CONFIG_TEST_BPF) += test_bpf.o

obj-$(CONFIG_TEST_FIRMWARE) += test_firmware.o

obj-$(CONFIG_TEST_HASH) += test_hash.o

obj-$(CONFIG_TEST_KASAN) += test_kasan.o

obj-$(CONFIG_TEST_KSTRTOX) += test-kstrtox.o

obj-$(CONFIG_TEST_LKM) += test_module.o