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

<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
......@@ -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
#
......
......@@ -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
......
......@@ -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 */
......
......@@ -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
......
......@@ -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
......
/*
* Test cases for <linux/hash.h> and <linux/stringhash.h>
* This just verifies that various ways of computing a hash
* produce the same thing and, for cases where a k-bit hash
* value is requested, is of the requested size.
*
* We fill a buffer with a 255-byte null-terminated string,
* and use both full_name_hash() and hashlen_string() to hash the
* substrings from i to j, where 0 <= i < j < 256.
*
* The returned values are used to check that __hash_32() and
* __hash_32_generic() compute the same thing. Likewise hash_32()
* and hash_64().
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt "\n"
#include <linux/compiler.h>
#include <linux/types.h>
#include <linux/module.h>
#include <linux/hash.h>
#include <linux/stringhash.h>
#include <linux/printk.h>
/* 32-bit XORSHIFT generator. Seed must not be zero. */
static u32 __init __attribute_const__
xorshift(u32 seed)
{
seed ^= seed << 13;
seed ^= seed >> 17;
seed ^= seed << 5;
return seed;
}
/* Given a non-zero x, returns a non-zero byte. */
static u8 __init __attribute_const__
mod255(u32 x)
{
x = (x & 0xffff) + (x >> 16); /* 1 <= x <= 0x1fffe */
x = (x & 0xff) + (x >> 8); /* 1 <= x <= 0x2fd */
x = (x & 0xff) + (x >> 8); /* 1 <= x <= 0x100 */
x = (x & 0xff) + (x >> 8); /* 1 <= x <= 0xff */
return x;
}
/* Fill the buffer with non-zero bytes. */
static void __init
fill_buf(char *buf, size_t len, u32 seed)
{
size_t i;
for (i = 0; i < len; i++) {
seed = xorshift(seed);
buf[i] = mod255(seed);
}
}
/*
* Test the various integer hash functions. h64 (or its low-order bits)
* is the integer to hash. hash_or accumulates the OR of the hash values,
* which are later checked to see that they cover all the requested bits.
*
* Because these functions (as opposed to the string hashes) are all
* inline, the code being tested is actually in the module, and you can
* recompile and re-test the module without rebooting.
*/
static bool __init
test_int_hash(unsigned long long h64, u32 hash_or[2][33])
{
int k;
u32 h0 = (u32)h64, h1, h2;
/* Test __hash32 */
hash_or[0][0] |= h1 = __hash_32(h0);
#ifdef HAVE_ARCH__HASH_32
hash_or[1][0] |= h2 = __hash_32_generic(h0);
#if HAVE_ARCH__HASH_32 == 1
if (h1 != h2) {
pr_err("__hash_32(%#x) = %#x != __hash_32_generic() = %#x",
h0, h1, h2);
return false;
}
#endif
#endif
/* Test k = 1..32 bits */
for (k = 1; k <= 32; k++) {
u32 const m = ((u32)2 << (k-1)) - 1; /* Low k bits set */
/* Test hash_32 */
hash_or[0][k] |= h1 = hash_32(h0, k);
if (h1 > m) {
pr_err("hash_32(%#x, %d) = %#x > %#x", h0, k, h1, m);
return false;
}
#ifdef HAVE_ARCH_HASH_32
h2 = hash_32_generic(h0, k);
#if HAVE_ARCH_HASH_32 == 1
if (h1 != h2) {
pr_err("hash_32(%#x, %d) = %#x != hash_32_generic() "
" = %#x", h0, k, h1, h2);
return false;
}
#else
if (h2 > m) {
pr_err("hash_32_generic(%#x, %d) = %#x > %#x",
h0, k, h1, m);
return false;
}
#endif
#endif
/* Test hash_64 */
hash_or[1][k] |= h1 = hash_64(h64, k);
if (h1 > m) {
pr_err("hash_64(%#llx, %d) = %#x > %#x", h64, k, h1, m);
return false;
}
#ifdef HAVE_ARCH_HASH_64
h2 = hash_64_generic(h64, k);
#if HAVE_ARCH_HASH_64 == 1
if (h1 != h2) {
pr_err("hash_64(%#llx, %d) = %#x != hash_64_generic() "
"= %#x", h64, k, h1, h2);
return false;
}
#else
if (h2 > m) {
pr_err("hash_64_generic(%#llx, %d) = %#x > %#x",
h64, k, h1, m);
return false;
}
#endif
#endif
}
(void)h2; /* Suppress unused variable warning */
return true;
}
#define SIZE 256 /* Run time is cubic in SIZE */
static int __init
test_hash_init(void)
{
char buf[SIZE+1];
u32 string_or = 0, hash_or[2][33] = { 0 };
unsigned tests = 0;
unsigned long long h64 = 0;
int i, j;
fill_buf(buf, SIZE, 1);
/* Test every possible non-empty substring in the buffer. */
for (j = SIZE; j > 0; --j) {
buf[j] = '\0';
for (i = 0; i <= j; i++) {
u64 hashlen = hashlen_string(buf+i);
u32 h0 = full_name_hash(buf+i, j-i);
/* Check that hashlen_string gets the length right */
if (hashlen_len(hashlen) != j-i) {
pr_err("hashlen_string(%d..%d) returned length"
" %u, expected %d",
i, j, hashlen_len(hashlen), j-i);
return -EINVAL;
}
/* Check that the hashes match */
if (hashlen_hash(hashlen) != h0) {
pr_err("hashlen_string(%d..%d) = %08x != "
"full_name_hash() = %08x",
i, j, hashlen_hash(hashlen), h0);
return -EINVAL;
}
string_or |= h0;
h64 = h64 << 32 | h0; /* For use with hash_64 */
if (!test_int_hash(h64, hash_or))
return -EINVAL;
tests++;
} /* i */
} /* j */
/* The OR of all the hash values should cover all the bits */
if (~string_or) {
pr_err("OR of all string hash results = %#x != %#x",
string_or, -1u);
return -EINVAL;
}
if (~hash_or[0][0]) {
pr_err("OR of all __hash_32 results = %#x != %#x",
hash_or[0][0], -1u);
return -EINVAL;
}
#ifdef HAVE_ARCH__HASH_32
#if HAVE_ARCH__HASH_32 != 1 /* Test is pointless if results match */
if (~hash_or[1][0]) {
pr_err("OR of all __hash_32_generic results = %#x != %#x",
hash_or[1][0], -1u);
return -EINVAL;
}
#endif
#endif
/* Likewise for all the i-bit hash values */
for (i = 1; i <= 32; i++) {
u32 const m = ((u32)2 << (i-1)) - 1; /* Low i bits set */
if (hash_or[0][i] != m) {
pr_err("OR of all hash_32(%d) results = %#x "
"(%#x expected)", i, hash_or[0][i], m);
return -EINVAL;
}
if (hash_or[1][i] != m) {
pr_err("OR of all hash_64(%d) results = %#x "
"(%#x expected)", i, hash_or[1][i], m);
return -EINVAL;
}
}
/* Issue notices about skipped tests. */
#ifndef HAVE_ARCH__HASH_32
pr_info("__hash_32() has no arch implementation to test.");
#elif HAVE_ARCH__HASH_32 != 1
pr_info("__hash_32() is arch-specific; not compared to generic.");
#endif
#ifndef HAVE_ARCH_HASH_32
pr_info("hash_32() has no arch implementation to test.");
#elif HAVE_ARCH_HASH_32 != 1
pr_info("hash_32() is arch-specific; not compared to generic.");
#endif
#ifndef HAVE_ARCH_HASH_64
pr_info("hash_64() has no arch implementation to test.");
#elif HAVE_ARCH_HASH_64 != 1
pr_info("hash_64() is arch-specific; not compared to generic.");
#endif
pr_notice("%u tests passed.", tests);
return 0;
}
static void __exit test_hash_exit(void)
{
}
module_init(test_hash_init); /* Does everything */
module_exit(test_hash_exit); /* Does nothing */
MODULE_LICENSE("GPL");
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