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libsecp256k1/src/util.h  view on Meta::CPAN

#define TEST_FAILURE(msg) do { \
    fprintf(stderr, "%s\n", msg); \
    abort(); \
} while(0);
#else
#define TEST_FAILURE(msg) do { \
    fprintf(stderr, "%s:%d: %s\n", __FILE__, __LINE__, msg); \
    abort(); \
} while(0)
#endif

#if SECP256K1_GNUC_PREREQ(3, 0)
#define EXPECT(x,c) __builtin_expect((x),(c))
#else
#define EXPECT(x,c) (x)
#endif

#ifdef DETERMINISTIC
#define CHECK(cond) do { \
    if (EXPECT(!(cond), 0)) { \
        TEST_FAILURE("test condition failed"); \
    } \
} while(0)
#else
#define CHECK(cond) do { \
    if (EXPECT(!(cond), 0)) { \
        TEST_FAILURE("test condition failed: " #cond); \
    } \
} while(0)
#endif

/* Like assert(), but when VERIFY is defined. */
#if defined(VERIFY)
#define VERIFY_CHECK CHECK
#else
#define VERIFY_CHECK(cond)
#endif

static SECP256K1_INLINE void *checked_malloc(const secp256k1_callback* cb, size_t size) {
    void *ret = malloc(size);
    if (ret == NULL) {
        secp256k1_callback_call(cb, "Out of memory");
    }
    return ret;
}

#if defined(__BIGGEST_ALIGNMENT__)
#define ALIGNMENT __BIGGEST_ALIGNMENT__
#else
/* Using 16 bytes alignment because common architectures never have alignment
 * requirements above 8 for any of the types we care about. In addition we
 * leave some room because currently we don't care about a few bytes. */
#define ALIGNMENT 16
#endif

/* ceil(x/y) for integers x > 0 and y > 0. Here, / denotes rational division. */
#define CEIL_DIV(x, y) (1 + ((x) - 1) / (y))

#define ROUND_TO_ALIGN(size) (CEIL_DIV(size, ALIGNMENT) * ALIGNMENT)

/* Macro for restrict, when available and not in a VERIFY build. */
#if defined(SECP256K1_BUILD) && defined(VERIFY)
# define SECP256K1_RESTRICT
#else
# if (!defined(__STDC_VERSION__) || (__STDC_VERSION__ < 199901L) )
#  if SECP256K1_GNUC_PREREQ(3,0)
#   define SECP256K1_RESTRICT __restrict__
#  elif (defined(_MSC_VER) && _MSC_VER >= 1400)
#   define SECP256K1_RESTRICT __restrict
#  else
#   define SECP256K1_RESTRICT
#  endif
# else
#  define SECP256K1_RESTRICT restrict
# endif
#endif

#if defined(__GNUC__)
# define SECP256K1_GNUC_EXT __extension__
#else
# define SECP256K1_GNUC_EXT
#endif

/* Zero memory if flag == 1. Flag must be 0 or 1. Constant time. */
static SECP256K1_INLINE void secp256k1_memczero(void *s, size_t len, int flag) {
    unsigned char *p = (unsigned char *)s;
    /* Access flag with a volatile-qualified lvalue.
       This prevents clang from figuring out (after inlining) that flag can
       take only be 0 or 1, which leads to variable time code. */
    volatile int vflag = flag;
    unsigned char mask = -(unsigned char) vflag;
    while (len) {
        *p &= ~mask;
        p++;
        len--;
    }
}

/* Cleanses memory to prevent leaking sensitive info. Won't be optimized out. */
static SECP256K1_INLINE void secp256k1_memclear(void *ptr, size_t len) {
#if defined(_MSC_VER)
    /* SecureZeroMemory is guaranteed not to be optimized out by MSVC. */
    SecureZeroMemory(ptr, len);
#elif defined(__GNUC__)
    /* We use a memory barrier that scares the compiler away from optimizing out the memset.
     *
     * Quoting Adam Langley <agl@google.com> in commit ad1907fe73334d6c696c8539646c21b11178f20f
     * in BoringSSL (ISC License):
     *    As best as we can tell, this is sufficient to break any optimisations that
     *    might try to eliminate "superfluous" memsets.
     * This method is used in memzero_explicit() the Linux kernel, too. Its advantage is that it
     * is pretty efficient, because the compiler can still implement the memset() efficently,
     * just not remove it entirely. See "Dead Store Elimination (Still) Considered Harmful" by
     * Yang et al. (USENIX Security 2017) for more background.
     */
    memset(ptr, 0, len);
    __asm__ __volatile__("" : : "r"(ptr) : "memory");
#else
    void *(*volatile const volatile_memset)(void *, int, size_t) = memset;
    volatile_memset(ptr, 0, len);
#endif