+.SH Mapping based on operating system and cpu
+Both the
+.B dllmap
+and the
+.B dllentry
+elements allow the following two attributes which make it easy to use a single
+configuration file and support multiple operating systems and architectures with
+different mapping requirements:
+.TP
+.I os
+This is the name of the operating system for which the mapping should be applied.
+Allowed values are: linux, osx, solaris, freebsd, openbsd, netbsd, windows, aix, hpux.
+.TP
+.I cpu
+This is the name of the architecture for which the mapping should be applied.
+Allowed values are: x86, x86-64, sparc, ppc, s390, s390x, arm, mips,
+alpha, hppa, ia64.
+.TP
+.I wordsize
+This is the size of registers on the target architecture, it can be
+either 32 or 64.
+.PP
+The attribute value for both attributes can be a comma-separated list of the allowed
+values. Additionally, the first character may be a
+.I '!'
+to reverse the meaning. An attribute value of "!windows,osx", for example, would mean
+that the entry is considered on all operating systems, except on Windows and OS X.
+No spaces are allowed in any part of the value.
+.PP
+Note that later entries will override the entries defined earlier in the file.