shared_lib: only export spdk_* symbols

Add a basic linker version script to limit exported symbols to those
intended to be public API.  Currently, many internal-only functions are
also named spdk_*, but this will at least limit exported symbols to
those that will not pollute the global namespace.

This also does not assign a version to any symbols; in the future, we
may want to extend the version script to enable ABI compatibility, but
for now, the version script is just used to control symbol visibility.

Change-Id: I1f020300b3288a026b47e9b1466ebc72952d9401
Signed-off-by: Daniel Verkamp <daniel.verkamp@intel.com>
Reviewed-on: https://review.gerrithub.io/415897
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>

.gitignore

@@ -7,7 +7,6 @@
 *.kdev4
 *.ko
 *.log
-*.map
 *.o
 *.pyc
 *.so

shared_lib/Makefile

@@ -83,13 +83,14 @@ LIBS += $(ENV_LINKER_ARGS)
 
 comma := ,
 
-$(SHARED_LIB): $(SPDK_LIB_FILES) $(SPDK_WHOLE_LIBS) $(BLOCKDEV_MODULES_FILES) $(COPY_MODULES_FILES) $(NET_MODULES_FILES) $(LINKER_MODULES) $(ENV_LIBS) $(MAKEFILE_LIST)
+$(SHARED_LIB): $(SPDK_LIB_FILES) $(SPDK_WHOLE_LIBS) $(BLOCKDEV_MODULES_FILES) $(COPY_MODULES_FILES) $(NET_MODULES_FILES) $(LINKER_MODULES) $(ENV_LIBS) $(MAKEFILE_LIST) spdk.map
 	$(Q)echo "  SO $(notdir $@)"; \
 	rm -f $@; \
 	$(CC) -o $@ -shared $(CPPFLAGS) $(LDFLAGS) \
 		-Wl,--whole-archive \
 		$(filter-out -Wl$(comma)--no-whole-archive,$(LIBS)) \
 		-Wl,--no-whole-archive \
+		-Wl,--version-script=spdk.map \
 		-lcrypto \
 		$(SYS_LIBS)
 

shared_lib/spdk.map

@@ -0,0 +1,4 @@
+{
+	global: spdk_*;
+	local: *;
+};