#include <sys/mman.h> int
minherit (void *addr size_t len int inherit);
DESCRIPTION
The
minherit ();
system call
changes the specified pages to have the inheritance characteristic
Fa inherit .
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.
Fx is capable of adjusting inheritance characteristics on a page basis.
Inheritance only effects children created by
fork (.);
It has no effect on
exec (.);
exec'd processes replace their address space entirely.
This system call also
has no effect on the parent's address space (other than to potentially
share the address space with its children).
Inheritance is a rather esoteric feature largely superseded by the
MAP_SHARED
feature of
mmap (.);
However, it is possible to use
minherit ();
to share a block of memory between parent and child that has been mapped
MAP_PRIVATE
That is, modifications made by parent or child are shared but
the original underlying file is left untouched.
INHERIT_SHARE
This option causes the address space in question to be shared between
parent and child.
It has no effect on how the original underlying backing
store was mapped.
INHERIT_NONE
This option prevents the address space in question from being inherited
at all.
The address space will be unmapped in the child.
INHERIT_COPY
This option causes the child to inherit the address space as copy-on-write.
This option also has an unfortunate side effect of causing the parent
address space to become copy-on-write when the parent forks.
If the original mapping was
MAP_SHARED
it will no longer be shared in the parent
after the parent forks and there is no way to get the previous
shared-backing-store mapping without unmapping and remapping the address
space in the parent.
RETURN VALUES
Rv -std minherit
ERRORS
The
minherit ();
system call will fail if:
Bq Er EINVAL
The virtual address range specified by the
Fa addr
and
Fa len
arguments is not valid.
Bq Er EACCES
The flags specified by the
Fa inherit
argument were not valid for the pages specified
by the
Fa addr
and
Fa len
arguments.
The
minherit ();
system call first appeared in
Ox and then in
Fx 2.2.0 .
BUGS
Once you set inheritance to
MAP_PRIVATE
or
MAP_SHARED
there is no way to recover the original copy-on-write semantics
short of unmapping and remapping the area.
