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MINHERIT(2)                   System Calls Manual                  MINHERIT(2)

NAME
     minherit - control the inheritance of pages

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <sys/mman.h>

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

DESCRIPTION
     The minherit() system call changes the specified range of virtual
     addresses to have the inheritance characteristic inherit, which
     determines how fork(2) will map the region in the child process.  The
     supported inheritance characteristics are:

         MAP_INHERIT_COPY     The child is given a private copy of the region:
                              writes from parent or child are not seen by the
                              other.

         MAP_INHERIT_NONE     The region is unmapped in the child.

         MAP_INHERIT_SHARE    The child is shares the region with the parent:
                              writes from parent and child are seen by both.

         MAP_INHERIT_ZERO     The region is mapped in the child to anonymous
                              pages filled with zeros.

     Normally, the parent's virtual address space is copied for the child as
     if with MAP_INHERIT_COPY, for which the alias MAP_INHERIT_DEFAULT is
     provided.  Regions in the parent mapped using mmap(2) with the MAP_SHARED
     flag are by default shared with the child as if with MAP_INHERIT_SHARED.

     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.

RETURN VALUES
     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
     error.

ERRORS
     minherit() will fail if:

     [EINVAL]           An invalid region or invalid parameters were
                        specified.

SEE ALSO
     fork(2), madvise(2), mincore(2), mmap(2), mprotect(2), msync(2),
     munmap(2)

HISTORY
     The minherit() function first appeared in OpenBSD 2.0, then NetBSD 1.3.

BUGS
     If a particular port does not support page-granularity inheritance,
     there's no way to figure out how large a region is actually affected by
     minherit().

NetBSD 10.99                   September 8, 2019                  NetBSD 10.99