Document methods people use to load linux shared libraries in FreeBSD

binaries.  A very neat trick.

1 files changed, 21 insertions, 0 deletions

diff --git a/share/man/man5/libmap.conf.5 b/share/man/man5/libmap.conf.5
index f6da1ea..b347f61 100644
--- a/share/man/man5/libmap.conf.5
+++ b/share/man/man5/libmap.conf.5
@@ -95,6 +95,22 @@ The most common use at the date of writing is for allowing multiple
 .Tn POSIX
 threading libraries to be used on a system without relinking or
 changing symlinks.
+.Pp
+This mechanism has also been used to create shims to allow Linux
+shared libraries to be dynamically loaded into
+.Fx
+binaries.
+In this case, an Exact constraint is use for the Linux shared library,
+mapping libraries it depends on to a wrapper.
+The wrapper then defines any needed symbols for the Linux shared library
+and relies on its libraries not being mapped to provide actual
+implementations.
+It appears that only libraries loaded via
+.Xr dlopen 3
+will work correctly.
+The symbol version information in shared libraries is checked at
+link time, but at run time the version information is currently
+ignored.
 .Sh FILES
 .Bl -tag -width ".Pa /etc/libmap.conf" -compact
 .It Pa /etc/libmap.conf
@@ -125,6 +141,11 @@ libpthread.so		libpthread.so
 			# programs with the full pathname
 libpthread.so.1		libthr.so.1
 libpthread.so		libthr.so
+
+# Glue for Linux-only EPSON printer .so to be loaded into cups, etc.
+[/usr/local/lib/pips/libsc80c.so]
+libc.so.6		pluginwrapper/pips.so
+libdl.so.2		pluginwrapper/pips.so
 .Ed
 .Sh SEE ALSO
 .Xr ldd 1 ,