[PATCH] Add CONFIG_HEADERS_CHECK option to automatically run 'make headers_check'

In order to encourage people to notice when they break the exported
headers, add a config option which automatically runs the sanity checks
when building vmlinux.  That way, those who use allyesconfig will notice
failures.
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Makefile

@@ -741,6 +741,9 @@ endif # ifdef CONFIG_KALLSYMS
 
 # vmlinux image - including updated kernel symbols
 vmlinux: $(vmlinux-lds) $(vmlinux-init) $(vmlinux-main) $(kallsyms.o) FORCE
+ifdef CONFIG_HEADERS_CHECK
+	$(Q)$(MAKE) headers_check
+endif
 	$(call if_changed_rule,vmlinux__)
 	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost $@
 	$(Q)rm -f .old_version

lib/Kconfig.debug

@@ -371,6 +371,19 @@ config FORCED_INLINING
 	  become the default in the future, until then this option is there to
 	  test gcc for this.
 
+config HEADERS_CHECK
+	bool "Run 'make headers_check' when building vmlinux"
+	help
+	  This option will extract the user-visible kernel headers whenever
+	  building the kernel, and will run basic sanity checks on them to
+	  ensure that exported files do not attempt to include files which
+	  were not exported, etc.
+
+	  If you're making modifications to header files which are
+	  relevant for userspace, say 'Y', and check the headers
+	  exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
+	  your build tree), to make sure they're suitable.
+
 config RCU_TORTURE_TEST
 	tristate "torture tests for RCU"
 	depends on DEBUG_KERNEL