control the inheritance of pages
Standard C Library (libc, -lc)
() system call changes the
specified pages to have the inheritance characteristic
. 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.
is capable of adjusting inheritance
characteristics on a page basis. Inheritance only effects children created by
(). It has no effect on
(). 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
Inheritance is a rather esoteric feature largely superseded by the
(). However, it is possible to use
() to share a block of memory
between parent and child that has been mapped
. That is, modifications made by
parent or child are shared but the original underlying file is left untouched.
- 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.
- This option prevents the address space in question from being inherited at
all. The address space will be unmapped in the child.
- 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
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.
- This option causes the address space in question to be mapped as new
anonymous pages, which would be initialized to all zero bytes, in the
() function returns the
value 0 if successful; otherwise the value -1 is returned and
the global variable errno
is set to indicate
() system call will fail if:
- The virtual address range specified by the
len arguments is not valid.
- The flags specified by the inherit
argument were not valid for the pages specified by the
() system call first appeared in
and then in FreeBSD
support first appeared in
and then in FreeBSD
Once you set inheritance to
, there is no way to recover the
original copy-on-write semantics short of unmapping and remapping the