diff options
author | rgrimes <rgrimes@FreeBSD.org> | 1994-05-27 05:00:24 +0000 |
---|---|---|
committer | rgrimes <rgrimes@FreeBSD.org> | 1994-05-27 05:00:24 +0000 |
commit | be22b15ae2ff8d7fe06b6e14fddf0c5b444a95da (patch) | |
tree | a18a706dffa5baf86a3b12bbfb4f81caa097f349 /lib/libc/sys/brk.2 | |
parent | 2a27bd86e6002c871e3b5561a5334653bb222a77 (diff) | |
download | FreeBSD-src-be22b15ae2ff8d7fe06b6e14fddf0c5b444a95da.zip FreeBSD-src-be22b15ae2ff8d7fe06b6e14fddf0c5b444a95da.tar.gz |
BSD 4.4 Lite Lib Sources
Diffstat (limited to 'lib/libc/sys/brk.2')
-rw-r--r-- | lib/libc/sys/brk.2 | 146 |
1 files changed, 146 insertions, 0 deletions
diff --git a/lib/libc/sys/brk.2 b/lib/libc/sys/brk.2 new file mode 100644 index 0000000..c84393d --- /dev/null +++ b/lib/libc/sys/brk.2 @@ -0,0 +1,146 @@ +.\" Copyright (c) 1980, 1991, 1993 +.\" The Regents of the University of California. All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 3. All advertising materials mentioning features or use of this software +.\" must display the following acknowledgement: +.\" This product includes software developed by the University of +.\" California, Berkeley and its contributors. +.\" 4. Neither the name of the University nor the names of its contributors +.\" may be used to endorse or promote products derived from this software +.\" without specific prior written permission. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" @(#)brk.2 8.2 (Berkeley) 12/11/93 +.\" +.Dd December 11, 1993 +.Dt BRK 2 +.Os BSD 4 +.Sh NAME +.Nm brk , +.Nm sbrk +.Nd change data segment size +.Sh SYNOPSIS +.Fd #include <sys/types.h> +.Ft char +.Fn *brk "const char *addr" +.Ft char * +.Fn *sbrk "int incr" +.Sh DESCRIPTION +.Bf -symbolic +The brk and sbrk functions are historical curiosities +left over from earlier days before the advent of virtual memory management. +.Ef +The +.Fn brk +function +sets the break or lowest address +of a process's data segment (uninitialized data) to +.Fa addr +(immediately above bss). +Data addressing is restricted between +.Fa addr +and the lowest stack pointer to the stack segment. +Memory is allocated by +.Fa brk +in page size pieces; +if +.Fa addr +is not evenly divisible by the system page size, it is +increased to the next page boundary. +.Pp +.\" The +.\" .Nm sbrk +.\" function +.\" allocates chunks of +.\" .Fa incr +.\" bytes +.\" to the process's data space +.\" and returns an address pointer. +.\" The +.\" .Xr malloc 3 +.\" function utilizes +.\" .Nm sbrk . +.\" .Pp +The current value of the program break is reliably returned by +.Dq Li sbrk(0) +(see also +.Xr end 3 ) . +The +.Xr getrlimit 2 +system call may be used to determine +the maximum permissible size of the +.Em data +segment; +it will not be possible to set the break +beyond the +.Em rlim_max +value returned from a call to +.Xr getrlimit , +e.g. +.Dq qetext + rlp\(->rlim_max. +(see +.Xr end 3 +for the definition of +.Em etext ) . +.Sh RETURN VALUES +.Nm Brk +returns a pointer to the new end of memory if successful; +otherwise -1 with +.Va errno +set to indicate why the allocation failed. +The +.Nm sbrk +returns a pointer to the base of the new storage if successful; +otherwise -1 with +.Va errno +set to indicate why the allocation failed. +.Sh ERRORS +.Xr Sbrk +will fail and no additional memory will be allocated if +one of the following are true: +.Bl -tag -width [ENOMEM] +.It Bq Er ENOMEM +The limit, as set by +.Xr setrlimit 2 , +was exceeded. +.It Bq Er ENOMEM +The maximum possible size of a data segment (compiled into the +system) was exceeded. +.It Bq Er ENOMEM +Insufficient space existed in the swap area +to support the expansion. +.El +.Sh SEE ALSO +.Xr execve 2 , +.Xr getrlimit 2 , +.Xr malloc 3 , +.Xr end 3 +.Sh BUGS +Setting the break may fail due to a temporary lack of +swap space. It is not possible to distinguish this +from a failure caused by exceeding the maximum size of +the data segment without consulting +.Xr getrlimit . +.Sh HISTORY +A +.Nm +function call appeared in Version 7 AT&T UNIX. |