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Release 4.18 lib/test_hash.c

Directory: lib
/*
 * 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; }

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/* 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; }

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/* 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); } }

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/* * 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; }

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#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, buf+i); u32 h0 = full_name_hash(buf+i, 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. */ #ifdef HAVE_ARCH__HASH_32 #if HAVE_ARCH__HASH_32 != 1 pr_info("__hash_32() is arch-specific; not compared to generic."); #endif #else pr_info("__hash_32() has no arch implementation to test."); #endif #ifdef HAVE_ARCH_HASH_32 #if HAVE_ARCH_HASH_32 != 1 pr_info("hash_32() is arch-specific; not compared to generic."); #endif #else pr_info("hash_32() has no arch implementation to test."); #endif #ifdef HAVE_ARCH_HASH_64 #if HAVE_ARCH_HASH_64 != 1 pr_info("hash_64() is arch-specific; not compared to generic."); #endif #else pr_info("hash_64() has no arch implementation to test."); #endif pr_notice("%u tests passed.", tests); return 0; }

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George Spelvin48391.83%125.00%
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static void __exit test_hash_exit(void) { }

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module_init(test_hash_init); /* Does everything */ module_exit(test_hash_exit); /* Does nothing */ MODULE_LICENSE("GPL");

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Geert Uytterhoeven353.13%250.00%
Linus Torvalds80.72%125.00%
Total1118100.00%4100.00%
Directory: lib
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