Eliminate the use of commons in the kernel and modules,

simplifying the module linking process and eliminating the risks
associated with doubly-defined variables.

Cases where commons were legitimately used (detection of
compiled-in subsystems) have been converted to use sysinits, and
any new code should use this or an equivalent practice as a
matter of course.

Modules can override this behaviour by substituting -fno-common
out of ${CFLAGS} in cases where commons are necessary
(eg. third-party object modules).  Commons will be resolved and
allocated space when the kld is linked as part of the module
build process, so they will not pose a risk to the kernel or
other modules.

Provide a mechanism for controlling the export of symbols from
the module namespace.  The EXPORT_SYMS variable may be set in the
Makefile to NO (export no symbols), a list of symbols to export,
or the name of a file containing a newline-seperated list of
symbols to be exported.  Non-exported symbols are converted to
local symbols.  If EXPORT_SYMS is not set, all global symbols are
currently exported.  This behaviour is expected to change (to
exporting no symbols) once modules have been converted.

Reviewed by:	peter (in principle)
Obtained from:	green (kmod_syms.awk)

1 files changed, 27 insertions, 0 deletions

diff --git a/sys/conf/kmod_syms.awk b/sys/conf/kmod_syms.awk
new file mode 100644
index 000000000000..3aa3eeb61f52
--- /dev/null
+++ b/sys/conf/kmod_syms.awk
@@ -0,0 +1,27 @@
+# $FreeBSD$
+
+# Read global symbols from object file.
+BEGIN {
+        while ("nm -g " ARGV[1] | getline) {
+                if (match($0, /^[^[:space:]]+ [^AU] (.*)$/)) {
+                        syms[$3] = $2
+                }
+        }
+}
+
+# De-list symbols from the export list.
+// {
+        if (ARGIND == 1)
+                nextfile
+        delete syms[$0]
+}
+
+# Strip commons, make everything else local.
+END {
+        for (member in syms) {
+                if (syms[member] == "C")
+                        print "-N" member
+                else
+                        print "-L" member
+        }
+}