datapath: Check the export of public functions in linux/compat/linux/.

This commit adds check in datapath/Makefile to make sure that all public
functions and exported symbols in linux/compat/ are either rpl_ or ovs_
prefixed, except those defined in compat/build-aux/export-check-whitelist.

Signed-off-by: Alex Wang <[email protected]>
Acked-by: Jesse Gross <[email protected]>

datapath/Makefile.am

@@ -28,4 +28,33 @@ print-build-modules:
 	   echo "Could not find any kernel module."; \
 	   exit 1; \
 	fi
-	@echo "$(build_modules)" | tr '_' '-';
+	@echo "$(build_modules)" | tr '_' '-';
+
+COMPAT_GET_FUNCTIONS := find $(top_srcdir)/datapath/linux/compat -name "*.h" \
+	-exec sed -n '/^[a-z][a-z]* \*\?[A-Za-z0-9_][A-Za-z0-9_]*([a-z]/p; /^struct [a-z0-9_][a-z0-9_]* \*\?[A-Za-z0-9_][A-Za-z0-9_]*([a-z]/p' {} \; | tr -d '*' | cut -d '(' -f1 | rev | cut -d ' ' -f1 | rev
+COMPAT_GET_EXPORTS := find $(top_srcdir)/datapath/linux/compat -name "*.c" \
+	-exec sed -n 's/^EXPORT_SYMBOL[A-Z_]*(\([a-z_][a-z_]*\));$$/\1/p' {} \;
+COMPAT_FUNCTIONS := $(shell $(COMPAT_GET_FUNCTIONS))
+COMPAT_EXPORTS := $(shell $(COMPAT_GET_EXPORTS))
+
+# Checks that all public functions are 'rpl_' or 'ovs_' prefixed.
+# Checks that all EXPORT_SYMBOL_GPL() export 'rpl_' or 'ovs_' prefixed functions.
+check-export-symbol:
+	@for fun_ in $(COMPAT_FUNCTIONS); do \
+	   if ! grep -- $${fun_} $(top_srcdir)/datapath/linux/compat/build-aux/export-check-whitelist > /dev/null; then \
+	      if [[ ! $${fun_} =~ ^rpl_* ]] \
+	         && [[ ! $${fun_} =~ ^ovs_* ]]; then \
+	         echo "Should prefix $${fun_} with rpl_ or ovs_."; \
+	         exit 1; \
+	      fi; \
+	   fi; \
+	done
+	@for fun_ in $(COMPAT_EXPORTS); do \
+	   if [[ ! $${fun_} =~ ^rpl_* ]] \
+	      && [[ ! $${fun_} =~ ^ovs_* ]]; then \
+	      echo "Should prefix $${fun_} with rpl_ or ovs_."; \
+	      exit 1; \
+	   fi; \
+	done
+
+all-local: check-export-symbol

datapath/README.md

@@ -246,3 +246,19 @@ The other rules for flow keys are much less subtle:
     composes it the same way.  This allows userspace to hash and
     compare entire flow keys that it may not be able to fully
     interpret.
+
+
+Coding rules
+============
+
+Compatibility
+-------------
+
+Please implement the headers and codes for compatibility with older kernel
+in linux/compat/ directory.  All public functions should be exported using
+EXPORT_SYMBOL macro.  Public function replacing the same-named kernel
+function should be prefixed with 'rpl_'.  Otherwise, the function should be
+prefixed with 'ovs_'.  For special case when it is not possible to follow
+this rule (e.g., the pskb_expand_head() function), the function name must
+be added to linux/compat/build-aux/export-check-whitelist, otherwise, the
+compilation check 'check-export-symbol' will fail.

datapath/linux/Modules.mk

@@ -77,3 +77,4 @@ openvswitch_headers += \
 	linux/compat/include/net/sock.h \
 	linux/compat/include/net/vxlan.h \
 	linux/compat/include/net/sctp/checksum.h
+EXTRA_DIST += linux/compat/build-aux/export-check-whitelist

datapath/linux/compat/build-aux/export-check-whitelist

@@ -0,0 +1 @@
+pskb_expand_head