minherit man page on FreeBSD

Man page or keyword search:  
man Server   9747 pages
apropos Keyword Search (all sections)
Output format
FreeBSD logo
[printable version]

MINHERIT(2)		    BSD System Calls Manual		   MINHERIT(2)

     minherit — control the inheritance of pages

     Standard C Library (libc, -lc)

     #include <sys/mman.h>

     minherit(void *addr, size_t len, int inherit);

     The minherit() system call changes the specified pages to have the inher‐
     itance characteristic inherit.  Not all implementations will guarantee
     that the inheritance characteristic can be set on a page basis; the gran‐
     ularity of changes may be as large as an entire region.  FreeBSD is capa‐
     ble of adjusting inheritance characteristics on a page basis.  Inheri‐
     tance 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     Inheritance is a rather esoteric feature largely superseded by the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 map‐
		    ping 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 unmap‐
		    ping and remapping the address space in the parent.

     The minherit() function returns the value 0 if successful; otherwise the
     value -1 is returned and the global variable errno is set to indicate the

     The minherit() system call will fail if:

     [EINVAL]		The virtual address range specified by the addr and
			len arguments is not valid.

     [EACCES]		The flags specified by the inherit argument were not
			valid for the pages specified by the addr and len

     fork(2), madvise(2), mincore(2), mprotect(2), msync(2), munmap(2),

     The minherit() system call first appeared in OpenBSD and then in
     FreeBSD 2.2.

     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.

BSD			       October 30, 2007				   BSD

List of man pages available for FreeBSD

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
Vote for polarhome
Free Shell Accounts :: the biggest list on the net