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34 .Nd control the inheritance of pages
40 .Fn minherit "void *addr" "size_t len" "int inherit"
45 changes the specified pages to have the inheritance characteristic
47 Not all implementations will guarantee that the inheritance characteristic
48 can be set on a page basis;
49 the granularity of changes may be as large as an entire region.
51 is capable of adjusting inheritance characteristics on a page basis.
52 Inheritance only effects children created by
56 exec'd processes replace their address space entirely.
58 has no effect on the parent's address space (other than to potentially
59 share the address space with its children).
61 Inheritance is a rather esoteric feature largely superseded by the
65 However, it is possible to use
67 to share a block of memory between parent and child that has been mapped
69 That is, modifications made by parent or child are shared but
70 the original underlying file is left untouched.
71 .Bl -tag -width ".Dv INHERIT_SHARE"
73 This option causes the address space in question to be shared between
75 It has no effect on how the original underlying backing
78 This option prevents the address space in question from being inherited
80 The address space will be unmapped in the child.
82 This option causes the child to inherit the address space as copy-on-write.
83 This option also has an unfortunate side effect of causing the parent
84 address space to become copy-on-write when the parent forks.
85 If the original mapping was
87 it will no longer be shared in the parent
88 after the parent forks and there is no way to get the previous
89 shared-backing-store mapping without unmapping and remapping the address
92 This option causes the address space in question to be mapped as new
94 which would be initialized to all zero bytes,
102 system call will fail if:
105 The virtual address range specified by the
109 arguments is not valid.
111 The flags specified by the
113 argument were not valid for the pages specified
131 system call first appeared in
138 support first appeared in
143 Once you set inheritance to
147 there is no way to recover the original copy-on-write semantics
148 short of unmapping and remapping the area.