Several fixes/improvements for the gcc plugin infrastructure:

- Fixes a problem with gcc plugins interfering with cc-option tests.
 - Aborts more gracefully when gcc plugin headers or compiler support is
   missing.
 - Improves the gcc plugin rule generation to be more dynamic, pass arguments,
   and build from subdirectories.
 -----BEGIN PGP SIGNATURE-----
 Version: GnuPG v1
 Comment: Kees Cook <kees@outflux.net>
 
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 -----END PGP SIGNATURE-----

Merge tag 'gcc-plugin-infrastructure-v4.8-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull gcc plugin improvements from Kees Cook:
 "Several fixes/improvements for the gcc plugin infrastructure:

   - fix a problem with gcc plugins interfering with cc-option tests.

   - abort more gracefully when gcc plugin headers or compiler support
     is missing.

   - improve the gcc plugin rule generation to be more dynamic, pass
     arguments, and build from subdirectories"

* tag 'gcc-plugin-infrastructure-v4.8-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  gcc-plugins: Add support for plugin subdirectories
  gcc-plugins: Automate make rule generation
  gcc-plugins: Add support for passing plugin arguments
  gcc-plugins: abort builds cleanly when not supported
  kbuild: no gcc-plugins during cc-option tests

Makefile

@@ -635,13 +635,6 @@ endif
 # Tell gcc to never replace conditional load with a non-conditional one
 KBUILD_CFLAGS	+= $(call cc-option,--param=allow-store-data-races=0)
 
-PHONY += gcc-plugins
-gcc-plugins: scripts_basic
-ifdef CONFIG_GCC_PLUGINS
-	$(Q)$(MAKE) $(build)=scripts/gcc-plugins
-endif
-	@:
-
 include scripts/Makefile.gcc-plugins
 
 ifdef CONFIG_READABLE_ASM

scripts/Kbuild.include

@@ -108,16 +108,20 @@ as-option = $(call try-run,\
 as-instr = $(call try-run,\
 	printf "%b\n" "$(1)" | $(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" -,$(2),$(3))
 
+# Do not attempt to build with gcc plugins during cc-option tests.
+# (And this uses delayed resolution so the flags will be up to date.)
+CC_OPTION_CFLAGS = $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS))
+
 # cc-option
 # Usage: cflags-y += $(call cc-option,-march=winchip-c6,-march=i586)
 
 cc-option = $(call try-run,\
-	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(1) -c -x c /dev/null -o "$$TMP",$(1),$(2))
+	$(CC) $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) $(1) -c -x c /dev/null -o "$$TMP",$(1),$(2))
 
 # cc-option-yn
 # Usage: flag := $(call cc-option-yn,-march=winchip-c6)
 cc-option-yn = $(call try-run,\
-	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(1) -c -x c /dev/null -o "$$TMP",y,n)
+	$(CC) $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) $(1) -c -x c /dev/null -o "$$TMP",y,n)
 
 # cc-option-align
 # Prefix align with either -falign or -malign
@@ -127,7 +131,7 @@ cc-option-align = $(subst -functions=0,,\
 # cc-disable-warning
 # Usage: cflags-y += $(call cc-disable-warning,unused-but-set-variable)
 cc-disable-warning = $(call try-run,\
-	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -W$(strip $(1)) -c -x c /dev/null -o "$$TMP",-Wno-$(strip $(1)))
+	$(CC) $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) -W$(strip $(1)) -c -x c /dev/null -o "$$TMP",-Wno-$(strip $(1)))
 
 # cc-name
 # Expands to either gcc or clang

scripts/Makefile.gcc-plugins

@@ -19,25 +19,42 @@ ifdef CONFIG_GCC_PLUGINS
     endif
   endif
 
-  GCC_PLUGINS_CFLAGS := $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y))
+  GCC_PLUGINS_CFLAGS := $(strip $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y)) $(gcc-plugin-cflags-y))
 
-  export PLUGINCC GCC_PLUGINS_CFLAGS GCC_PLUGIN SANCOV_PLUGIN
+  export PLUGINCC GCC_PLUGINS_CFLAGS GCC_PLUGIN GCC_PLUGIN_SUBDIR SANCOV_PLUGIN
 
-  ifeq ($(PLUGINCC),)
-    ifneq ($(GCC_PLUGINS_CFLAGS),)
-      ifeq ($(call cc-ifversion, -ge, 0405, y), y)
-        PLUGINCC := $(shell $(CONFIG_SHELL) -x $(srctree)/scripts/gcc-plugin.sh "$(__PLUGINCC)" "$(HOSTCXX)" "$(CC)")
-        $(warning warning: your gcc installation does not support plugins, perhaps the necessary headers are missing?)
-      else
-        $(warning warning: your gcc version does not support plugins, you should upgrade it to gcc 4.5 at least)
-      endif
-    endif
-  else
+  ifneq ($(PLUGINCC),)
     # SANCOV_PLUGIN can be only in CFLAGS_KCOV because avoid duplication.
     GCC_PLUGINS_CFLAGS := $(filter-out $(SANCOV_PLUGIN), $(GCC_PLUGINS_CFLAGS))
   endif
 
   KBUILD_CFLAGS += $(GCC_PLUGINS_CFLAGS)
   GCC_PLUGIN := $(gcc-plugin-y)
-
+  GCC_PLUGIN_SUBDIR := $(gcc-plugin-subdir-y)
 endif
+
+# If plugins aren't supported, abort the build before hard-to-read compiler
+# errors start getting spewed by the main build.
+PHONY += gcc-plugins-check
+gcc-plugins-check: FORCE
+ifdef CONFIG_GCC_PLUGINS
+  ifeq ($(PLUGINCC),)
+    ifneq ($(GCC_PLUGINS_CFLAGS),)
+      ifeq ($(call cc-ifversion, -ge, 0405, y), y)
+	$(Q)$(srctree)/scripts/gcc-plugin.sh --show-error "$(__PLUGINCC)" "$(HOSTCXX)" "$(CC)" || true
+	@echo "Cannot use CONFIG_GCC_PLUGINS: your gcc installation does not support plugins, perhaps the necessary headers are missing?" >&2 && exit 1
+      else
+	@echo "Cannot use CONFIG_GCC_PLUGINS: your gcc version does not support plugins, you should upgrade it to at least gcc 4.5" >&2 && exit 1
+      endif
+    endif
+  endif
+endif
+	@:
+
+# Actually do the build, if requested.
+PHONY += gcc-plugins
+gcc-plugins: scripts_basic gcc-plugins-check
+ifdef CONFIG_GCC_PLUGINS
+	$(Q)$(MAKE) $(build)=scripts/gcc-plugins
+endif
+	@:

scripts/gcc-plugin.sh

@@ -1,5 +1,12 @@
 #!/bin/sh
 srctree=$(dirname "$0")
+
+SHOW_ERROR=
+if [ "$1" = "--show-error" ] ; then
+	SHOW_ERROR=1
+	shift || true
+fi
+
 gccplugins_dir=$($3 -print-file-name=plugin)
 plugincc=$($1 -E -x c++ - -o /dev/null -I"${srctree}"/gcc-plugins -I"${gccplugins_dir}"/include 2>&1 <<EOF
 #include "gcc-common.h"
@@ -13,6 +20,9 @@ EOF
 
 if [ $? -ne 0 ]
 then
+	if [ -n "$SHOW_ERROR" ] ; then
+		echo "${plugincc}" >&2
+	fi
 	exit 1
 fi
 
@@ -48,4 +58,8 @@ then
 	echo "$2"
 	exit 0
 fi
+
+if [ -n "$SHOW_ERROR" ] ; then
+	echo "${plugincc}" >&2
+fi
 exit 1

scripts/gcc-plugins/Makefile

@@ -12,16 +12,18 @@ else
   export HOST_EXTRACXXFLAGS
 endif
 
-export GCCPLUGINS_DIR HOSTLIBS
-
 ifneq ($(CFLAGS_KCOV), $(SANCOV_PLUGIN))
   GCC_PLUGIN := $(filter-out $(SANCOV_PLUGIN), $(GCC_PLUGIN))
 endif
 
-$(HOSTLIBS)-y := $(GCC_PLUGIN)
+export HOSTLIBS
+
+$(HOSTLIBS)-y := $(foreach p,$(GCC_PLUGIN),$(if $(findstring /,$(p)),,$(p)))
 always := $($(HOSTLIBS)-y)
 
-cyc_complexity_plugin-objs := cyc_complexity_plugin.o
-sancov_plugin-objs := sancov_plugin.o
+$(foreach p,$($(HOSTLIBS)-y:%.so=%),$(eval $(p)-objs := $(p).o))
+
+subdir-y := $(GCC_PLUGIN_SUBDIR)
+subdir-  += $(GCC_PLUGIN_SUBDIR)
 
 clean-files += *.so