[PATCH 07/10] : Add support for architecture-specific functions

George Spelvin
2016-05-25T07:33:12Z

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/archhash.h>.

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

Signed-off-by: George Spelvin <linux@sciencehorizons.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greg Ungerer <gerg@linux-m68k.org>
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
---
arch/Kconfig | 8 ++++++++
fs/namei.c | 6 +++++-
include/linux/hash.h | 11 +++++++++++
3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 81869a5e..33e8d7b1 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -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/archhash.h>
+ file which provides platform-specific implementations of some
+ functions in <linux/hash.h> or fs/namei.c.
+
#
# ABI hall of shame
#
diff --git a/fs/namei.c b/fs/namei.c
index 2b8d0650..380e8057 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -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 <linux/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
diff --git a/include/linux/hash.h b/include/linux/hash.h
index 8926f369..838bc84b 100644
--- a/include/linux/hash.h
+++ b/include/linux/hash.h
@@ -41,17 +41,27 @@
#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/archhash.h>
+#endif
+
+#ifndef HAVE_ARCH__HASH_32
static inline u32 __hash_32(u32 val)
{
return val * GOLDEN_RATIO_32;
}
+#endif

+#ifndef HAVE_ARCH_HASH_32
static inline u32 hash_32(u32 val, unsigned int bits)
{
/* High bits are more random, so use them. */
return __hash_32(val) >> (32 - bits);
}
+#endif

+#ifndef HAVE_ARCH_HASH_64
static __always_inline u32 hash_64(u64 val, unsigned int bits)
{
if (__builtin_constant_p(bits > 32 || bits == 0)) {
@@ -74,6 +84,7 @@ static __always_inline u32 hash_64(u64 val, unsigned int bits)
return hash_32((u32)val - __hash_32(val >> 32), bits);
#endif
}
+#endif

static inline u32 hash_ptr(const void *ptr, unsigned int bits)
{
--
2.8.1