From be22b15ae2ff8d7fe06b6e14fddf0c5b444a95da Mon Sep 17 00:00:00 2001 From: rgrimes Date: Fri, 27 May 1994 05:00:24 +0000 Subject: BSD 4.4 Lite Lib Sources --- lib/libc/sys/mlock.2 | 161 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 161 insertions(+) create mode 100644 lib/libc/sys/mlock.2 (limited to 'lib/libc/sys/mlock.2') diff --git a/lib/libc/sys/mlock.2 b/lib/libc/sys/mlock.2 new file mode 100644 index 0000000..90bb7c7 --- /dev/null +++ b/lib/libc/sys/mlock.2 @@ -0,0 +1,161 @@ +.\" Copyright (c) 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. +.\" +.\" @(#)mlock.2 8.2 (Berkeley) 12/11/93 +.\" +.Dd June 2, 1993 +.Dt MLOCK 2 +.Os +.Sh NAME +.Nm mlock , +.Nm munlock +.Nd lock (unlock) physical pages in memory +.Sh SYNOPSIS +.Fd #include +.Fd #include +.Ft int +.Fn mlock "caddr_t addr" "size_t len" +.Ft int +.Fn munlock "caddr_t addr" "size_t len" +.Sh DESCRIPTION +The +.Nm mlock +system call +locks into memory the physical pages associated with the virtual address +range starting at +.Fa addr +for +.Fa len +bytes. +The +.Nm munlock +call unlocks pages previously locked by one or more +.Nm mlock +calls. +For both, the +.Fa addr +parameter should be aligned to a multiple of the page size. +If the +.Fa len +parameter is not a multiple of the page size, it will be rounded up +to be so. +The entire range must be allocated. +.Pp +After an +.Nm mlock +call, the indicated pages will cause neither a non-resident page +nor address-translation fault until they are unlocked. +They may still cause protection-violation faults or TLB-miss faults on +architectures with software-managed TLBs. +The physical pages remain in memory until all locked mappings for the pages +are removed. +Multiple processes may have the same physical pages locked via their own +virtual address mappings. +A single process may likewise have pages multiply-locked via different virtual +mappings of the same pages or via nested +.Nm mlock +calls on the same address range. +Unlocking is performed explicitly by +.Nm munlock +or implicitly by a call to +.Nm munmap +which deallocates the unmapped address range. +Locked mappings are not inherited by the child process after a +.Xr fork 2 . +.Pp +Since physical memory is a potentially scarce resource, processes are +limited in how much they can lock down. +A single process can +.Nm mlock +the minimum of +a system-wide ``wired pages'' limit and +the per-process +.Li RLIMIT_MEMLOCK +resource limit. +.Sh RETURN VALUES +A return value of 0 indicates that the call +succeeded and all pages in the range have either been locked or unlocked. +A return value of -1 indicates an error occurred and the locked +status of all pages in the range remains unchanged. +In this case, the global location +.Va errno +is set to indicate the error. +.Sh ERRORS +.Fn Mlock +will fail if: +.Bl -tag -width Er +.It Bq Er EINVAL +The address given is not page aligned or the length is negative. +.It Bq Er EAGAIN +Locking the indicated range would exceed either the system or per-process +limit for locked memory. +.It Bq Er ENOMEM +Some portion of the indicated address range is not allocated. +There was an error faulting/mapping a page. +.El +.Fn Munlock +will fail if: +.Bl -tag -width Er +.It Bq Er EINVAL +The address given is not page aligned or the length is negative. +.It Bq Er ENOMEM +Some portion of the indicated address range is not allocated. +Some portion of the indicated address range is not locked. +.El +.Sh "SEE ALSO" +.Xr fork 2 , +.Xr mmap 2 , +.Xr munmap 2 , +.Xr setrlimit 2 , +.Xr getpagesize 3 +.Sh BUGS +Unlike The Sun implementation, multiple +.Nm mlock +calls on the same address range require the corresponding number of +.Nm munlock +calls to actually unlock the pages, i.e. +.Nm mlock +nests. +This should be considered a consequence of the implementation +and not a feature. +.Pp +The per-process resource limit is a limit on the amount of virtual +memory locked, while the system-wide limit is for the number of locked +physical pages. +Hence a process with two distinct locked mappings of the same physical page +counts as 2 pages against the per-process limit and as only a single page +in the system limit. +.Sh HISTORY +The +.Fn mlock +and +.Fn munlock +functions first appeared in 4.4BSD. -- cgit v1.1