Module Name: src
Committed By: riastradh
Date: Tue Aug 5 15:01:03 UTC 2014
Modified Files:
src/lib/libc/sys: minherit.2
Log Message:
Rework minherit(2) man page into a table.
XXX Do we not guarantee page-granularity inheritance? Cursory glance
at uvm suggests we do -- can we nix the caveats about regions vs
pages?
To generate a diff of this commit:
cvs rdiff -u -r1.19 -r1.20 src/lib/libc/sys/minherit.2
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/lib/libc/sys/minherit.2
diff -u src/lib/libc/sys/minherit.2:1.19 src/lib/libc/sys/minherit.2:1.20
--- src/lib/libc/sys/minherit.2:1.19 Fri Jul 18 12:39:17 2014
+++ src/lib/libc/sys/minherit.2 Tue Aug 5 15:01:03 2014
@@ -1,4 +1,4 @@
-.\" $NetBSD: minherit.2,v 1.19 2014/07/18 12:39:17 christos Exp $
+.\" $NetBSD: minherit.2,v 1.20 2014/08/05 15:01:03 riastradh Exp $
.\"
.\" Copyright (c) 1991, 1993
.\" The Regents of the University of California. All rights reserved.
@@ -29,7 +29,7 @@
.\"
.\" @(#)minherit.2 8.1 (Berkeley) 6/9/93
.\"
-.Dd July 18, 2014
+.Dd August 5, 2014
.Dt MINHERIT 2
.Os
.Sh NAME
@@ -44,38 +44,43 @@
.Sh DESCRIPTION
The
.Fn minherit
-system call
-changes the specified range of virtual addresses to have the specified
-fork-time inheritance characteristic
+system call changes the specified range of virtual addresses to have
+the inheritance characteristic
.Fa inherit ,
-which can be set to
-.Dv MAP_INHERIT_NONE ,
+which determines how
+.Xr fork 2
+will map the region in the child process.
+The supported inheritance characteristics are:
+.Bl -tag -offset abcd -width MAP_INHERIT_DEFAULT
+.It MAP_INHERIT_COPY
+The child is given a private copy of the region: writes from parent or
+child are not seen by the other.
+.It MAP_INHERIT_NONE
+The region is unmapped in the child.
+.It MAP_INHERIT_SHARE
+The child is shares the region with the parent: writes from parent and
+child are seen by both.
+.It MAP_INHERIT_ZERO
+The region is mapped in the child to anonymous pages filled with
+zeros.
+.El
+.Pp
+Normally, the parent's virtual address space is copied for the child
+as if with
.Dv MAP_INHERIT_COPY ,
-.Dv MAP_INHERIT_SHARE ,
-or
-.Dv MAP_INHERIT_ZERO .
-Also possible is
-.Dv MAP_INHERIT_DEFAULT ,
-which defaults to
-.Dv MAP_INHERIT_COPY .
+for which the alias
+.Dv MAP_INHERIT_DEFAULT
+is provided.
+Regions in the parent mapped using
+.Xr mmap 2
+with the
+.Dv MAP_SHARED
+flag are by default shared with the child as if with
+.Dv MAP_INHERIT_SHARED .
+.Pp
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.
-.Pp
-Normally, the entire address space is marked
-.Dv MAP_INHERIT_COPY ;
-when the process calls
-.Fn fork ,
-the child receives a (virtual) copy of the entire address space.
-Pages or regions marked
-.Dv MAP_INHERIT_SHARE
-are shared between the address spaces, while pages or regions marked
-.Dv MAP_INHERIT_NONE
-will be unmapped in the child.
-Finally pages or regions marked
-.Dv MAP_INHERIT_ZERO
-will still be present at the child, but will be initialized to
-.Dv 0 .
.Sh RETURN VALUES
.Rv -std minherit
.Sh ERRORS
@@ -89,6 +94,7 @@ An invalid region or invalid parameters
.Xr fork 2 ,
.Xr madvise 2 ,
.Xr mincore 2 ,
+.Xr mmap 2 ,
.Xr mprotect 2 ,
.Xr msync 2 ,
.Xr munmap 2
