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8269e7673c
Remove core system call implementations and documentation to lib/libsys and lib/libsys/<arch> from lib/libc/sys and lib/libc/<arch>/<sys>. Update paths to allow libc to find them in their new home. Reviewed by: kib, emaste, imp Pull Request: https://github.com/freebsd/freebsd-src/pull/908
132 lines
3.4 KiB
Groff
132 lines
3.4 KiB
Groff
.\" Copyright 2020, 2018 Conrad Meyer <cem@FreeBSD.org>. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.Dd January 12, 2020
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.Dt GETRANDOM 2
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.Os
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.Sh NAME
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.Nm getrandom
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.Nd get random data
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/random.h
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.Ft ssize_t
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.Fn getrandom "void *buf" "size_t buflen" "unsigned int flags"
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.Sh DESCRIPTION
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.Fn getrandom
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fills
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.Fa buf
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with up to
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.Fa buflen
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bytes of random data.
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.Pp
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The
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.Fa flags
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argument may include zero or more of the following:
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.Bl -tag -width _GRND_NONBLOCK_
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.It Ql GRND_NONBLOCK
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Return
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.Er EAGAIN
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instead of blocking, if the
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.Xr random 4
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device has not yet been seeded.
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By default,
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.Fn getrandom
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will block until the device is seeded.
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.It Ql GRND_RANDOM
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This flag does nothing on
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.Fx .
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.Pa /dev/random
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and
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.Pa /dev/urandom
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are identical.
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.It Ql GRND_INSECURE
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This flag is treated as an alternative name for
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.Dv GRND_NONBLOCK .
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It is provided solely for API compatibility with Linux.
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.El
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.Pp
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If the
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.Xr random 4
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device has been seeded, reads of up to 256 bytes will always return as many
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bytes as requested and will not be interrupted by signals.
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.Sh RETURN VALUES
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Upon successful completion, the number of bytes which were actually read is
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returned.
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For requests larger than 256 bytes, this can be fewer bytes than were
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requested.
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Otherwise, -1 is returned and the global variable
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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The
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.Fn getrandom
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operation returns the following errors:
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.Bl -tag -width Er
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.It Bq Er EAGAIN
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The
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.Ql GRND_NONBLOCK
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(or
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.Ql GRND_INSECURE )
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flag was set and the
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.Xr random 4
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device was not yet seeded.
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.It Bq Er EFAULT
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The
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.Fa buf
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parameter points to an invalid address.
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.It Bq Er EINTR
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The sleep was interrupted by a signal.
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.It Bq Er EINVAL
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An invalid
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.Fa flags
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was specified.
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.It Bq Er EINVAL
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The requested
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.Fa buflen
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was larger than
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.Dv IOSIZE_MAX .
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.El
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.Sh SEE ALSO
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.Xr arc4random 3 ,
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.Xr getentropy 3 ,
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.Xr random 4
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.Sh STANDARDS
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.Fn getrandom
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is non-standard.
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It is present in Linux.
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.Sh HISTORY
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The
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.Fn getrandom
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system call first appeared in
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.Fx 12.0 .
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.Sh CAVEATS
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Unlike Linux, the
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.Dv GRND_INSECURE
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flag on
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.Fx
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does not produce any output before the
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.Xr random 4
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device is seeded.
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