064f007493
converted them into .Fn macros where appropriate. Also fixed up some minor formatting problems.
147 lines
4.2 KiB
Groff
147 lines
4.2 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993
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.\" The Regents of the University of California. 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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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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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.\" @(#)brk.2 8.2 (Berkeley) 12/11/93
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.\"
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.Dd December 11, 1993
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.Dt BRK 2
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.Os BSD 4
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.Sh NAME
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.Nm brk ,
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.Nm sbrk
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.Nd change data segment size
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.Sh SYNOPSIS
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.Fd #include <sys/types.h>
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.Ft int
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.Fn brk "const char *addr"
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.Ft char *
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.Fn *sbrk "int incr"
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.Sh DESCRIPTION
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.Bf -symbolic
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The brk and sbrk functions are historical curiosities
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left over from earlier days before the advent of virtual memory management.
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.Ef
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The
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.Fn brk
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function
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sets the break or lowest address
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of a process's data segment (uninitialized data) to
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.Fa addr
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(immediately above bss).
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Data addressing is restricted between
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.Fa addr
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and the lowest stack pointer to the stack segment.
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Memory is allocated by
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.Fa brk
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in page size pieces;
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if
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.Fa addr
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is not evenly divisible by the system page size, it is
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increased to the next page boundary.
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.Pp
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.\" The
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.\" .Nm sbrk
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.\" function
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.\" allocates chunks of
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.\" .Fa incr
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.\" bytes
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.\" to the process's data space
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.\" and returns an address pointer.
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.\" The
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.\" .Xr malloc 3
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.\" function utilizes
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.\" .Nm sbrk .
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.\" .Pp
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The current value of the program break is reliably returned by
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.Dq Li sbrk(0)
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(see also
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.Xr end 3 ) .
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The
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.Xr getrlimit 2
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system call may be used to determine
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the maximum permissible size of the
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.Em data
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segment;
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it will not be possible to set the break
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beyond the
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.Em rlim_max
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value returned from a call to
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.Xr getrlimit 2 ,
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e.g.
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.Dq qetext + rlp\(->rlim_max.
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(see
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.Xr end 3
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for the definition of
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.Em etext ) .
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.Sh RETURN VALUES
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.Nm Brk
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returns 0 if successful;
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otherwise -1 with
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.Va errno
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set to indicate why the allocation failed.
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The
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.Nm sbrk
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returns a pointer to the base of the new storage if successful;
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otherwise -1 with
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.Va errno
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set to indicate why the allocation failed.
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.Sh ERRORS
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.Fn Sbrk
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will fail and no additional memory will be allocated if
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one of the following are true:
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.Bl -tag -width [ENOMEM]
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.It Bq Er ENOMEM
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The limit, as set by
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.Xr setrlimit 2 ,
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was exceeded.
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.It Bq Er ENOMEM
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The maximum possible size of a data segment (compiled into the
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system) was exceeded.
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.It Bq Er ENOMEM
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Insufficient space existed in the swap area
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to support the expansion.
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.El
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.Sh SEE ALSO
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.Xr execve 2 ,
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.Xr getrlimit 2 ,
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.Xr malloc 3 ,
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.Xr end 3
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.Sh BUGS
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Setting the break may fail due to a temporary lack of
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swap space. It is not possible to distinguish this
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from a failure caused by exceeding the maximum size of
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the data segment without consulting
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.Xr getrlimit 2 .
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.Sh HISTORY
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A
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.Nm
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function call appeared in Version 7 AT&T UNIX.
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