.\"	$NetBSD: mremap.2,v 1.5 2017/05/06 21:34:51 joerg Exp $
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.\" Copyright (c) 2007 Thomas Klausner and Joerg Sonnenberger
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.\" ------------------------------------------------------------
.Dd April 28, 2017
.Dt MREMAP 2
.Os
.Sh NAME
.Nm mremap
.Nd re-map a virtual memory address
.\" ------------------------------------------------------------
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/mman.h
.Ft void *
.Fn mremap "void *oldp" "size_t oldsize" "void *newp" "size_t newsize" \
"int flags"
.\" ------------------------------------------------------------
.Sh DESCRIPTION
The
.Fn mremap
function resizes the mapped range (see
.Xr mmap 2 )
starting at
.Ar oldp
and having size
.Ar oldsize
to
.Ar newsize .
The following arguments can be
.Dv OR Ap ed
together in the
.Ar flags
argument:
.Bl -tag -width XXMAPXALIGNEDXnXX
.It Dv MAP_ALIGNED Ns Pq Ar n
The allocation should be aligned to the given boundary, i.e. ensure
that the lowest
.Ar n
bits of the address are zero.
The parameter
.Ar n
should be the base 2 logarithm of the desired alignment (e.g., to
request alignment to 16K, use 14 as the value for n).
The alignment must be equal to or greater than the platform's page
size as returned by
.Xr sysconf 3
with the
.Dv _SC_PAGESIZE
request.
.It Dv MAP_FIXED
.Ar newp
is tried and
.Fn mremap
fails if that address can't be used as new base address for the range.
Otherwise,
.Ar oldp
and
.Ar newp
are used as hints for the position, factoring in the given alignment.
.It Dv MAP_REMAPDUP
Duplicate the mapping.
Both address ranges reference the same pages, but can have different protection flags.
.El
.Sh RETURN VALUES
.Fn mremap
returns the new address or
.Dv MAP_FAILED ,
if the remap failed.
.Sh COMPATIBILITY
The semantics of
.Fn mremap
differ from the one provided by glibc on Linux in that the
.Ar newp
argument was added and a different set of
.Ar flags
are implemented.
.Sh SEE ALSO
.Xr mmap 2 ,
.Xr munmap 2
.Sh HISTORY
The
.Fn mremap
system call appeared in
.Nx 5.0 .
It was based on the code that supports
.Fn mremap
compatibility for Linux binaries.