[PATCH 1/3] gcc-plugins: Force full rebuild when plugins change

[Kees Cook]

There was no dependency between the plugins changing and the rest of the
kernel being built. Enforce this by including a synthetic header file
when using plugins, that is regenerated any time the plugins are built.

Signed-off-by: Kees Cook <kees@xxxxxxxxxx>
---
Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Cc: Nathan Chancellor <nathan@xxxxxxxxxx>
Cc: Nicolas Schier <nicolas.schier@xxxxxxxxx>
Cc: <linux-hardening@xxxxxxxxxxxxxxx>
Cc: <linux-kbuild@xxxxxxxxxxxxxxx>
---
 scripts/Makefile.gcc-plugins | 2 +-
 scripts/gcc-plugins/Makefile | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
index 5b8a8378ca8a..b0d2b9ccf42c 100644
--- a/scripts/Makefile.gcc-plugins
+++ b/scripts/Makefile.gcc-plugins
@@ -38,7 +38,7 @@ export DISABLE_STACKLEAK_PLUGIN
 
 # All the plugin CFLAGS are collected here in case a build target needs to
 # filter them out of the KBUILD_CFLAGS.
-GCC_PLUGINS_CFLAGS := $(strip $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y)) $(gcc-plugin-cflags-y))
+GCC_PLUGINS_CFLAGS := $(strip $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y)) $(gcc-plugin-cflags-y)) -include $(objtree)/scripts/gcc-plugins/deps.h
 export GCC_PLUGINS_CFLAGS
 
 # Add the flags to the build!
diff --git a/scripts/gcc-plugins/Makefile b/scripts/gcc-plugins/Makefile
index 320afd3cf8e8..38fd4c9f9b98 100644
--- a/scripts/gcc-plugins/Makefile
+++ b/scripts/gcc-plugins/Makefile
@@ -66,3 +66,11 @@ quiet_cmd_plugin_cxx_o_c = HOSTCXX $@
 
 $(plugin-objs): $(obj)/%.o: $(src)/%.c FORCE
 	$(call if_changed_dep,plugin_cxx_o_c)
+
+quiet_cmd_gcc_plugins_updated = UPDATE  $@
+      cmd_gcc_plugins_updated = echo '/* $^ */' > $(obj)/deps.h
+
+$(obj)/deps.h: $(plugin-single) $(plugin-multi) FORCE
+	$(call if_changed,gcc_plugins_updated)
+
+always-y += deps.h
-- 
2.34.1