2000-01-19 09:47:19 +00:00
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.\" Copyright (c) 2000 David E. O'Brien
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.\" 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 AUTHOR 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 AUTHOR 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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.\" $FreeBSD$
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.\"
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.Dd January 18, 2000
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.Dt UAC 1
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.Os
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.Sh NAME
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.Nm uac
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.Nd Unaligned Access Message Control
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.Sh SYNOPSIS
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.Nm uac
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.Op Fl fprs
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.Sh DESCRIPTION
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.Nm
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sets the per-process handling of "Unaligned Access" events. Unlike many
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other CPU's the DEC Alpha processor cannot access unaligned data. To work
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around this, the Alpha has the ability to fix the UA fault rather than send
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the faulting process a SIGBUS signal. However, doing so does slow down the
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execution of the faulting process.
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2000-01-19 18:36:01 +00:00
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At boot up, the DEC Alpha CPU defaults to printing
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.Bl -diag
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.It pid nnn (<progname>): unaligned access: va=0xADDR pc=0xADDR ra=0xADDR op=ldl
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.El
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.Pp
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when a UA happens along with fixing it so
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2000-01-19 09:47:19 +00:00
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the faulting instruction can continue.
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UA handling settings are inherited by child process.
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Issued with out any options,
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.Mn
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displays the current UA handling for the parent process.
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.Pp
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The options are as follows:
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.Bl -tag -width Fl
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.It Fl f
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Unaligned access errors are not fixed for the parent and its future descendants.
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.It Fl p
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Unaligned access errors are not printed for the parent and its future
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descendants.
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.It Fl r
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Resets the unaligned access error settings back to their bootup defaults.
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.It Fl s
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Unaligned access errors result in a SIGBUS being delivered to the parent and
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its future descendants. This aid in pin pointing the faulting access so it
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debugged.
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.El
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.Sh DIAGNOSTICS
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Exit status is 0 on success, and 1 if the command
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fails for any reason.
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.El
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.Sh COMPATIBILITY
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The
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.Nm
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command syntax is incompatible with the DEC OSF/1 syntax.
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.Sh SEE ALSO
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.Xr signal 3
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.Sh HISTORY
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.Nm
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first appeared in DEC OSF/1.
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.Pp
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.Sh AUTHORS
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The
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.Fx
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version of
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.Nm
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was originally written by
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.An Andrew Gallatin Aq gallatin@cs.duke.edu
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and modified by
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.An David E. O'Brien Aq obrien@FreeBSD.org .
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This
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manual page was written by
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.An David E. O'Brien Aq obrien@FreeBSD.org .
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