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34 .\" @(#)minherit.2 8.1 (Berkeley) 6/9/93
41 .Nd control the inheritance of pages
48 .Fn minherit "void *addr" "size_t len" "int inherit"
53 changes the specified pages to have the inheritance characteristic
55 Not all implementations will guarantee that the inheritance characteristic
56 can be set on a page basis;
57 the granularity of changes may be as large as an entire region.
59 is capable of adjusting inheritance characteristics on a page basis.
60 Inheritance only effects children created by
64 exec'd processes replace their address space entirely.
66 has no effect on the parent's address space (other than to potentially
67 share the address space with its children).
69 Inheritance is a rather esoteric feature largely superseded by the
73 However, it is possible to use
75 to share a block of memory between parent and child that has been mapped
77 That is, modifications made by parent or child are shared but
78 the original underlying file is left untouched.
79 .Bl -tag -width ".Dv INHERIT_SHARE"
81 This option causes the address space in question to be shared between
83 It has no effect on how the original underlying backing
86 This option prevents the address space in question from being inherited
88 The address space will be unmapped in the child.
90 This option causes the child to inherit the address space as copy-on-write.
91 This option also has an unfortunate side effect of causing the parent
92 address space to become copy-on-write when the parent forks.
93 If the original mapping was
95 it will no longer be shared in the parent
96 after the parent forks and there is no way to get the previous
97 shared-backing-store mapping without unmapping and remapping the address
105 function will fail if:
108 The virtual address range specified by the
112 arguments is not valid.
114 The flags specified by the
116 argument were not valid for the pages specified
124 Once you set inheritance to
128 there is no way to recover the original copy-on-write semantics
129 short of unmapping and remapping the area.
141 function first appeared in