munmap.2

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 2 代码 · 共 91 行

.TH munmap 2
.SH Name
munmap \- unmaps memory of a character device
.SH Syntax
#include <sys/types.h>
.br
#include <sys/mman.h>
.nf

caddr_t munmap(\fIaddr\fP, \fIlen\fP)
caddr_t \fIaddr\fP;
size_t \fIlen\fP;
.fi
.SH Arguments
.TP 10
\fIaddr\fP
Specifies the address space of the calling process at which the unmapping
begins.
.TP 10
\fIlen\fP
Specifies the number of bytes to unmap.
.SH Description
.NXR "munmap call"
.NXR "memory unmapping" "munmap call"
The
.PN munmap
system call unmaps a specified number of bytes 
(\fIlen\fP)
starting at a specified address
(\fIaddr\fP)
from the address space of the calling process.
You mapped this device in a previous call to
.PN mmap .
Subsequent access to the unmapped region results in a 
.PN SIGSEGV
signal.
You cannot unmap
data, stack, and text segments using
.PN munmap .
.PP
The
.PN munmap
system call
rounds
\fIlen\fP
to the nearest multiple of page size as returned by
.PN getpagesize .
.PP
The range [\fIaddr\fP, \fIaddr\fP + \fIlen\fP] may contain more than one
mapped region created by
.PN mmap .
In this case,
.PN munmap
unmaps all of the mapped regions.
.SH Restrictions
All of the mapped regions must be wholly contained in the range
[\fIaddr\fP, \fIaddr\fP + \fIlen\fP].
That is,
\fIaddr\fP
must be the beginning of some mapped region and
\fIaddr\fP + \fIlen\fP
must be the end of some (possibly different) mapped region.
.SH Return Value
If successful,
.PN munmap
returns 0.
Otherwise, it returns \-1
and sets the
\fIerrno\fP
argument to one of the errors listed in the Diagnostics section.
.SH Diagnostics
The call to
.PN munmap 
fails if one or more of the following is true:
.TP 10
[EINVAL]
The address you specified in
\fIaddr\fP
is not a multiple of the page size as returned by
.PN getsysinfo .
.TP 10
[EINVAL]
The addresses in the range [\fIaddr\fP, \fIaddr\fP + \fIlen\fP] are not
valid in the process address space.
.TP 10
[EINVAL]
All of the segments being unmapped are not entirely contained in the
range [\fIaddr\fP, \fIaddr\fP + \fIlen\fP]. 
.SH See Also
getpagesize(2), getsysinfo(2), mmap(2)