@@ -1447,6 +1447,7 @@ systems.
* ISO Random:: @code{rand} and friends.
* BSD Random:: @code{random} and friends.
* SVID Random:: @code{drand48} and friends.
+* High Quality Random:: @code{arc4random} and friends.
@end menu
@node ISO Random
@@ -1985,6 +1986,51 @@ This function is a GNU extension and should not be used in portable
programs.
@end deftypefun
+@node High Quality Random
+@subsection High Quality Random Number Functions
+
+This section describes the random number functions provided as a GNU
+extension, based on OpenBSD interfaces.
+
+@Theglibc{} uses kernel entropy obtained either through @code{getrandom}
+or by reading @file{/dev/urandom} to seed and periodically re-seed the
+internal state. A per-thread data pool is used, which allows fast output
+generation.
+
+Although these functions provide higher random quality than ISO, BSD, and
+SVID functions, these still use a Pseudo-Random generator and should not
+be used in cryptographic contexts.
+
+The internal state is cleared and reseeded with kernel entropy on @code{fork}
+and @code{_Fork}. It is not cleared on either a direct @code{clone} syscall
+or when using @theglibc{} @code{syscall} function.
+
+The prototypes for these functions are in @file{stdlib.h}.
+@pindex stdlib.h
+
+@deftypefun uint32_t arc4random (void)
+@standards{BSD, stdlib.h}
+@safety{@mtsafe{}@asunsafe{@asucorrupt{}}@acsafe{}}
+This function returns a single 32-bit value in the range of @code{0} to
+@code{2^32−1} (inclusive), which is twice the range of @code{rand} and
+@code{random}.
+@end deftypefun
+
+@deftypefun void arc4random_buf (void *@var{buffer}, size_t @var{length})
+@standards{BSD, stdlib.h}
+@safety{@mtsafe{}@asunsafe{@asucorrupt{}}@acsafe{}}
+This function fills the region @var{buffer} of length @var{length} bytes
+with random data.
+@end deftypefun
+
+@deftypefun uint32_t arc4random_uniform (uint32_t @var{upper_bound})
+@standards{BSD, stdlib.h}
+@safety{@mtsafe{}@asunsafe{@asucorrupt{}}@acsafe{}}
+This function returns a single 32-bit value, uniformly distributed but
+less than the @var{upper_bound}. It avoids the @w{modulo bias} when the
+upper bound is not a power of two.
+@end deftypefun
+
@node FP Function Optimizations
@section Is Fast Code or Small Code preferred?
@cindex Optimization
From: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org> --- manual/math.texi | 46 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+)