// SPDX-License-Identifier: GPL-2.0-only

  /*
   * 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 "
  "
  
  #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, 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;
  }
  
  static void __exit test_hash_exit(void)
  {
  }
  
  module_init(test_hash_init);	/* Does everything */
  module_exit(test_hash_exit);	/* Does nothing */
  
  MODULE_LICENSE("GPL");