<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: George 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
This commit is contained in:
George Spelvin
parent
2a18da7a9c
commit
468a942852
6 changed files with 299 additions and 4 deletions
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@ -589,6 +589,14 @@ config HAVE_STACK_VALIDATION
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Architecture supports the 'objtool check' host tool command, which
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performs compile-time stack metadata validation.
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config HAVE_ARCH_HASH
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bool
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default n
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help
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If this is set, the architecture provides an <asm/hash.h>
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file which provides platform-specific implementations of some
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functions in <linux/hash.h> or fs/namei.c.
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#
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# ABI hall of shame
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#
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@ -1788,7 +1788,11 @@ static int walk_component(struct nameidata *nd, int flags)
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#include <asm/word-at-a-time.h>
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#ifdef CONFIG_64BIT
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#ifdef HASH_MIX
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/* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */
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#elif defined(CONFIG_64BIT)
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/*
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* Register pressure in the mixing function is an issue, particularly
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* on 32-bit x86, but almost any function requires one state value and
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@ -41,19 +41,40 @@
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#define GOLDEN_RATIO_32 0x61C88647
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#define GOLDEN_RATIO_64 0x61C8864680B583EBull
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#ifdef CONFIG_HAVE_ARCH_HASH
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/* This header may use the GOLDEN_RATIO_xx constants */
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#include <asm/hash.h>
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#endif
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static inline u32 __hash_32(u32 val)
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/*
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* The _generic versions exist only so lib/test_hash.c can compare
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* the arch-optimized versions with the generic.
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*
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* Note that if you change these, any <asm/hash.h> that aren't updated
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* to match need to have their HAVE_ARCH_* define values updated so the
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* self-test will not false-positive.
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*/
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#ifndef HAVE_ARCH__HASH_32
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#define __hash_32 __hash_32_generic
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#endif
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static inline u32 __hash_32_generic(u32 val)
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{
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return val * GOLDEN_RATIO_32;
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}
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static inline u32 hash_32(u32 val, unsigned int bits)
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#ifndef HAVE_ARCH_HASH_32
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#define hash_32 hash_32_generic
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#endif
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static inline u32 hash_32_generic(u32 val, unsigned int bits)
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{
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/* High bits are more random, so use them. */
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return __hash_32(val) >> (32 - bits);
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}
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static __always_inline u32 hash_64(u64 val, unsigned int bits)
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#ifndef HAVE_ARCH_HASH_64
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#define hash_64 hash_64_generic
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#endif
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static __always_inline u32 hash_64_generic(u64 val, unsigned int bits)
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{
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#if BITS_PER_LONG == 64
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/* 64x64-bit multiply is efficient on all 64-bit processors */
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@ -1815,6 +1815,17 @@ config TEST_RHASHTABLE
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If unsure, say N.
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config TEST_HASH
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tristate "Perform selftest on hash functions"
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default n
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help
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Enable this option to test the kernel's integer (<linux/hash,h>)
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and string (<linux/stringhash.h>) hash functions on boot
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(or module load).
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This is intended to help people writing architecture-specific
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optimized versions. If unsure, say N.
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endmenu # runtime tests
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config PROVIDE_OHCI1394_DMA_INIT
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@ -48,6 +48,7 @@ obj-$(CONFIG_TEST_HEXDUMP) += test_hexdump.o
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obj-y += kstrtox.o
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obj-$(CONFIG_TEST_BPF) += test_bpf.o
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obj-$(CONFIG_TEST_FIRMWARE) += test_firmware.o
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obj-$(CONFIG_TEST_HASH) += test_hash.o
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obj-$(CONFIG_TEST_KASAN) += test_kasan.o
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obj-$(CONFIG_TEST_KSTRTOX) += test-kstrtox.o
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obj-$(CONFIG_TEST_LKM) += test_module.o
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250
lib/test_hash.c
Normal file
250
lib/test_hash.c
Normal file
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@ -0,0 +1,250 @@
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/*
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* Test cases for <linux/hash.h> and <linux/stringhash.h>
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* This just verifies that various ways of computing a hash
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* produce the same thing and, for cases where a k-bit hash
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* value is requested, is of the requested size.
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*
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* We fill a buffer with a 255-byte null-terminated string,
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* and use both full_name_hash() and hashlen_string() to hash the
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* substrings from i to j, where 0 <= i < j < 256.
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*
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* The returned values are used to check that __hash_32() and
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* __hash_32_generic() compute the same thing. Likewise hash_32()
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* and hash_64().
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt "\n"
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#include <linux/compiler.h>
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#include <linux/types.h>
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#include <linux/module.h>
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#include <linux/hash.h>
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#include <linux/stringhash.h>
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#include <linux/printk.h>
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/* 32-bit XORSHIFT generator. Seed must not be zero. */
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static u32 __init __attribute_const__
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xorshift(u32 seed)
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{
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seed ^= seed << 13;
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seed ^= seed >> 17;
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seed ^= seed << 5;
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return seed;
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}
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/* Given a non-zero x, returns a non-zero byte. */
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static u8 __init __attribute_const__
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mod255(u32 x)
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{
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x = (x & 0xffff) + (x >> 16); /* 1 <= x <= 0x1fffe */
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x = (x & 0xff) + (x >> 8); /* 1 <= x <= 0x2fd */
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x = (x & 0xff) + (x >> 8); /* 1 <= x <= 0x100 */
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x = (x & 0xff) + (x >> 8); /* 1 <= x <= 0xff */
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return x;
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}
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/* Fill the buffer with non-zero bytes. */
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static void __init
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fill_buf(char *buf, size_t len, u32 seed)
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{
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size_t i;
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for (i = 0; i < len; i++) {
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seed = xorshift(seed);
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buf[i] = mod255(seed);
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}
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}
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/*
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* Test the various integer hash functions. h64 (or its low-order bits)
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* is the integer to hash. hash_or accumulates the OR of the hash values,
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* which are later checked to see that they cover all the requested bits.
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*
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* Because these functions (as opposed to the string hashes) are all
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* inline, the code being tested is actually in the module, and you can
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* recompile and re-test the module without rebooting.
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*/
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static bool __init
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test_int_hash(unsigned long long h64, u32 hash_or[2][33])
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{
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int k;
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u32 h0 = (u32)h64, h1, h2;
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/* Test __hash32 */
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hash_or[0][0] |= h1 = __hash_32(h0);
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#ifdef HAVE_ARCH__HASH_32
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hash_or[1][0] |= h2 = __hash_32_generic(h0);
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#if HAVE_ARCH__HASH_32 == 1
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if (h1 != h2) {
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pr_err("__hash_32(%#x) = %#x != __hash_32_generic() = %#x",
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h0, h1, h2);
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return false;
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}
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#endif
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#endif
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/* Test k = 1..32 bits */
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for (k = 1; k <= 32; k++) {
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u32 const m = ((u32)2 << (k-1)) - 1; /* Low k bits set */
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/* Test hash_32 */
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hash_or[0][k] |= h1 = hash_32(h0, k);
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if (h1 > m) {
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pr_err("hash_32(%#x, %d) = %#x > %#x", h0, k, h1, m);
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return false;
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}
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#ifdef HAVE_ARCH_HASH_32
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h2 = hash_32_generic(h0, k);
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#if HAVE_ARCH_HASH_32 == 1
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if (h1 != h2) {
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pr_err("hash_32(%#x, %d) = %#x != hash_32_generic() "
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" = %#x", h0, k, h1, h2);
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return false;
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}
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#else
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if (h2 > m) {
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pr_err("hash_32_generic(%#x, %d) = %#x > %#x",
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h0, k, h1, m);
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return false;
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}
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#endif
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#endif
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/* Test hash_64 */
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hash_or[1][k] |= h1 = hash_64(h64, k);
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if (h1 > m) {
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pr_err("hash_64(%#llx, %d) = %#x > %#x", h64, k, h1, m);
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return false;
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}
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#ifdef HAVE_ARCH_HASH_64
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h2 = hash_64_generic(h64, k);
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#if HAVE_ARCH_HASH_64 == 1
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if (h1 != h2) {
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pr_err("hash_64(%#llx, %d) = %#x != hash_64_generic() "
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"= %#x", h64, k, h1, h2);
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return false;
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}
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#else
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if (h2 > m) {
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pr_err("hash_64_generic(%#llx, %d) = %#x > %#x",
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h64, k, h1, m);
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return false;
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}
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#endif
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#endif
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}
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(void)h2; /* Suppress unused variable warning */
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return true;
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}
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#define SIZE 256 /* Run time is cubic in SIZE */
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static int __init
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test_hash_init(void)
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{
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char buf[SIZE+1];
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u32 string_or = 0, hash_or[2][33] = { 0 };
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unsigned tests = 0;
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unsigned long long h64 = 0;
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int i, j;
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fill_buf(buf, SIZE, 1);
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/* Test every possible non-empty substring in the buffer. */
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for (j = SIZE; j > 0; --j) {
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buf[j] = '\0';
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for (i = 0; i <= j; i++) {
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u64 hashlen = hashlen_string(buf+i);
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u32 h0 = full_name_hash(buf+i, j-i);
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/* Check that hashlen_string gets the length right */
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if (hashlen_len(hashlen) != j-i) {
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pr_err("hashlen_string(%d..%d) returned length"
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" %u, expected %d",
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i, j, hashlen_len(hashlen), j-i);
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return -EINVAL;
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}
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/* Check that the hashes match */
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if (hashlen_hash(hashlen) != h0) {
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pr_err("hashlen_string(%d..%d) = %08x != "
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"full_name_hash() = %08x",
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i, j, hashlen_hash(hashlen), h0);
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return -EINVAL;
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}
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string_or |= h0;
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h64 = h64 << 32 | h0; /* For use with hash_64 */
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if (!test_int_hash(h64, hash_or))
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return -EINVAL;
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tests++;
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} /* i */
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} /* j */
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/* The OR of all the hash values should cover all the bits */
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if (~string_or) {
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pr_err("OR of all string hash results = %#x != %#x",
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string_or, -1u);
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return -EINVAL;
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}
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if (~hash_or[0][0]) {
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pr_err("OR of all __hash_32 results = %#x != %#x",
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hash_or[0][0], -1u);
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return -EINVAL;
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}
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#ifdef HAVE_ARCH__HASH_32
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#if HAVE_ARCH__HASH_32 != 1 /* Test is pointless if results match */
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if (~hash_or[1][0]) {
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pr_err("OR of all __hash_32_generic results = %#x != %#x",
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hash_or[1][0], -1u);
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return -EINVAL;
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}
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#endif
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#endif
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/* Likewise for all the i-bit hash values */
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for (i = 1; i <= 32; i++) {
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u32 const m = ((u32)2 << (i-1)) - 1; /* Low i bits set */
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if (hash_or[0][i] != m) {
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pr_err("OR of all hash_32(%d) results = %#x "
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"(%#x expected)", i, hash_or[0][i], m);
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return -EINVAL;
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}
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if (hash_or[1][i] != m) {
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pr_err("OR of all hash_64(%d) results = %#x "
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"(%#x expected)", i, hash_or[1][i], m);
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return -EINVAL;
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}
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}
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/* Issue notices about skipped tests. */
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#ifndef HAVE_ARCH__HASH_32
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pr_info("__hash_32() has no arch implementation to test.");
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#elif HAVE_ARCH__HASH_32 != 1
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pr_info("__hash_32() is arch-specific; not compared to generic.");
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#endif
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#ifndef HAVE_ARCH_HASH_32
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pr_info("hash_32() has no arch implementation to test.");
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#elif HAVE_ARCH_HASH_32 != 1
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pr_info("hash_32() is arch-specific; not compared to generic.");
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#endif
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#ifndef HAVE_ARCH_HASH_64
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pr_info("hash_64() has no arch implementation to test.");
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#elif HAVE_ARCH_HASH_64 != 1
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pr_info("hash_64() is arch-specific; not compared to generic.");
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#endif
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pr_notice("%u tests passed.", tests);
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return 0;
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}
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static void __exit test_hash_exit(void)
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{
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}
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module_init(test_hash_init); /* Does everything */
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module_exit(test_hash_exit); /* Does nothing */
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MODULE_LICENSE("GPL");
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