From: Mark Harris <mark.hsj@gmail.com>
To: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Cc: libc-alpha@sourceware.org, Florian Weimer <fweimer@redhat.com>
Subject: Re: [PATCH v9 9/9] manual: Add documentation for arc4random functions
Date: Thu, 14 Jul 2022 03:03:08 -0700 [thread overview]
Message-ID: <CAMdZqKEfu9MvTUnr7+awbAQCtpSvE8sfpgod4wuLFFwaZac8XQ@mail.gmail.com> (raw)
In-Reply-To: <20220713173657.516725-10-adhemerval.zanella@linaro.org>
Adhemerval Zanella via Libc-alpha wrote:
> diff --git a/manual/math.texi b/manual/math.texi
> index 477a18b6d1..ab96726e57 100644
> --- a/manual/math.texi
> +++ b/manual/math.texi
> @@ -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 +1986,50 @@ 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 reseed with kernel entropy on @code{fork}
s/reseed/reseeded/
> +and @code{_Fork}. It is not cleared for either direct @code{clone} syscall
s/for either/on either a/
> +or when using @theglibc{} @code{syscall} function.
> +
> +The prototypes for these functions are in @file{stdlib.h}.
> +@pindex stdlib.h
> +
> +@deftypefun int32_t arc4random (void)
s/int32_t/uint32_t/
> +@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 (void *@var{buffer}, size_t @var{length})
s/arc4random/arc4random_buf/
> +@standards{BSD, stdlib.h}
> +@safety{@mtsafe{}@asunsafe{@asucorrupt{}}@acsafe{}}
> +This function fills the region @var{buffer} of @var{length} with random data.
s/of @var{length}/of length @var{length} bytes/
> +@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
> --
> 2.34.1
>
next prev parent reply other threads:[~2022-07-14 10:03 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-13 17:36 [PATCH v9 0/9] Add arc4random support Adhemerval Zanella
2022-07-13 17:36 ` [PATCH v9 1/9] stdlib: Add arc4random, arc4random_buf, and arc4random_uniform (BZ #4417) Adhemerval Zanella
2022-07-13 17:36 ` [PATCH v9 2/9] stdlib: Add arc4random tests Adhemerval Zanella
2022-07-13 17:36 ` [PATCH v9 3/9] benchtests: Add arc4random benchtest Adhemerval Zanella
2022-07-13 17:36 ` [PATCH v9 4/9] aarch64: Add optimized chacha20 Adhemerval Zanella
2022-07-13 17:36 ` [PATCH v9 5/9] x86: Add SSE2 " Adhemerval Zanella
2022-07-13 18:12 ` Noah Goldstein
2022-07-13 18:20 ` Adhemerval Zanella Netto
2022-07-13 18:22 ` Noah Goldstein
2022-07-13 18:27 ` Noah Goldstein
2022-07-13 18:29 ` Adhemerval Zanella Netto
2022-07-13 18:53 ` Noah Goldstein
2022-07-13 17:36 ` [PATCH v9 6/9] x86: Add AVX2 " Adhemerval Zanella
2022-07-13 18:07 ` Noah Goldstein
2022-07-13 19:31 ` Adhemerval Zanella Netto
2022-07-13 20:24 ` Noah Goldstein
2022-07-13 20:16 ` Florian Weimer
2022-07-13 20:23 ` Noah Goldstein
2022-07-13 17:36 ` [PATCH v9 7/9] powerpc64: Add " Adhemerval Zanella
2022-07-13 17:36 ` [PATCH v9 8/9] s390x: " Adhemerval Zanella
2022-07-13 17:36 ` [PATCH v9 9/9] manual: Add documentation for arc4random functions Adhemerval Zanella
2022-07-14 10:03 ` Mark Harris [this message]
2022-07-14 11:08 ` Adhemerval Zanella Netto
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