// SPDX-License-Identifier: LGPL-2.1-or-later

/*

 * Safe memory utilities

 *

 * Copyright (C) 2024-2025 Milan Broz

 */

#include "crypto_backend_internal.h"

#define ATTR_NOINLINE __attribute__ ((noinline))

#define ATTR_ZERO_REGS

#if HAVE_ATTRIBUTE_ZEROCALLUSEDREGS

#    undef ATTR_ZERO_REGS

#    define ATTR_ZERO_REGS __attribute__ ((zero_call_used_regs("used")))

#endif

/* Workaround for https://github.com/google/sanitizers/issues/1507 */

#if defined __has_feature

# if __has_feature (memory_sanitizer)

#   undef HAVE_EXPLICIT_BZERO

# endif

#endif

/* Memzero helper (memset on stack can be optimized out) */

ATTR_NOINLINE ATTR_ZERO_REGS

void crypt_backend_memzero(void *s, size_t n)

{

#if HAVE_EXPLICIT_BZERO

  explicit_bzero(s, n);

#else

  volatile uint8_t *p = (volatile uint8_t *)s;

  while(n--) *p++ = 0;

#endif

}

/* Memcpy helper to avoid spilling sensitive data through additional registers */

ATTR_NOINLINE ATTR_ZERO_REGS

void *crypt_backend_memcpy(void *dst, const void *src, size_t n)

{

  volatile uint8_t *d = (volatile uint8_t *)dst;

  const volatile uint8_t *s = (const volatile uint8_t *)src;

  while(n--) *d++ = *s++;

  return dst;

}

/* Internal implementation for constant time memory comparison */

ATTR_NOINLINE ATTR_ZERO_REGS

int crypt_internal_memeq(const void *m1, const void *m2, size_t n)

{

  const unsigned char *_m1 = (const unsigned char *) m1;

  const unsigned char *_m2 = (const unsigned char *) m2;

  unsigned char result = 0;

  size_t i;

  for (i = 0; i < n; i++)

    result |= _m1[i] ^ _m2[i];

  return result;

}