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.\"	@(#)minherit.2	8.1 (Berkeley) 6/9/93
.\"
.Dd September 8, 2019
.Dt MINHERIT 2
.Os
.Sh NAME
.Nm minherit
.Nd control the inheritance of pages
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/mman.h
.Ft int
.Fn minherit "void *addr" "size_t len" "int inherit"
.Sh DESCRIPTION
The
.Fn minherit
system call changes the specified range of virtual addresses to have
the inheritance characteristic
.Fa inherit ,
which determines how
.Xr fork 2
will map the region in the child process.
The supported inheritance characteristics are:
.Bl -tag -offset abcd -width MAP_INHERIT_DEFAULT
.It MAP_INHERIT_COPY
The child is given a private copy of the region: writes from parent or
child are not seen by the other.
.It MAP_INHERIT_NONE
The region is unmapped in the child.
.It MAP_INHERIT_SHARE
The child is shares the region with the parent: writes from parent and
child are seen by both.
.It MAP_INHERIT_ZERO
The region is mapped in the child to anonymous pages filled with
zeros.
.El
.Pp
Normally, the parent's virtual address space is copied for the child
as if with
.Dv MAP_INHERIT_COPY ,
for which the alias
.Dv MAP_INHERIT_DEFAULT
is provided.
Regions in the parent mapped using
.Xr mmap 2
with the
.Dv MAP_SHARED
flag are by default shared with the child as if with
.Dv MAP_INHERIT_SHARED .
.Pp
Not all implementations will guarantee that the inheritance characteristic
can be set on a page basis;
the granularity of changes may be as large as an entire region.
.Sh RETURN VALUES
.Rv -std minherit
.Sh ERRORS
.Fn minherit
will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
An invalid region or invalid parameters were specified.
.El
.Sh SEE ALSO
.Xr fork 2 ,
.Xr madvise 2 ,
.Xr mincore 2 ,
.Xr mmap 2 ,
.Xr mprotect 2 ,
.Xr msync 2 ,
.Xr munmap 2
.Sh HISTORY
The
.Fn minherit
function first appeared in
.Ox 2.0 ,
then
.Nx 1.3 .
.Sh BUGS
If a particular port does not support page-granularity
inheritance, there's no way to figure out how large a region is
actually affected by
.Fn minherit .