gcc-plugins: test plugin support in Kconfig and clean up Makefile

Run scripts/gcc-plugin.sh from Kconfig so that users can enable
GCC_PLUGINS only when the compiler supports building plugins.

Kconfig defines a new symbol, PLUGIN_HOSTCC.  This will contain
the compiler (g++ or gcc) used for building plugins, or empty
if the plugin can not be supported at all.

This allows us to remove all ugly testing in Makefile.gcc-plugins.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Kees Cook <keescook@chromium.org>

4 files changed, 36 insertions, 57 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index 2c7c3cf8adfc..e4a47d640a87 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -398,6 +398,15 @@ config SECCOMP_FILTER
 
           See Documentation/prctl/seccomp_filter.txt for details.
 
+preferred-plugin-hostcc := $(if-success,[ $(gcc-version) -ge 40800 ],$(HOSTCXX),$(HOSTCC))
+
+config PLUGIN_HOSTCC
+        string
+        default "$(shell,$(srctree)/scripts/gcc-plugin.sh "$(preferred-plugin-hostcc)" "$(HOSTCXX)" "$(CC)")"
+        help
+          Host compiler used to build GCC plugins.  This can be $(HOSTCXX),
+          $(HOSTCC), or a null string if GCC plugin is unsupported.
+
 config HAVE_GCC_PLUGINS
         bool
         help
@@ -407,6 +416,7 @@ config HAVE_GCC_PLUGINS
 menuconfig GCC_PLUGINS
         bool "GCC plugins"
         depends on HAVE_GCC_PLUGINS
+        depends on PLUGIN_HOSTCC != ""
         depends on !COMPILE_TEST
         help
           GCC plugins are loadable modules that provide extra features to the
diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
index bf7c0c9fa3a4..dad5583451af 100644
--- a/scripts/Kconfig.include
+++ b/scripts/Kconfig.include
@@ -25,3 +25,6 @@ cc-option = $(success,$(CC) -Werror $(1) -E -x c /dev/null -o /dev/null)
 # $(ld-option,<flag>)
 # Return y if the linker supports <flag>, n otherwise
 ld-option = $(success,$(LD) -v $(1))
+
+# gcc version including patch level
+gcc-version := $(shell,$(srctree)/scripts/gcc-version.sh -p $(CC) | sed 's/^0*//')
diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
index 32bdf184eced..c961b9a65d11 100644
--- a/scripts/Makefile.gcc-plugins
+++ b/scripts/Makefile.gcc-plugins
@@ -1,72 +1,37 @@
 # SPDX-License-Identifier: GPL-2.0
-ifdef CONFIG_GCC_PLUGINS
-  __PLUGINCC := $(call cc-ifversion, -ge, 0408, $(HOSTCXX), $(HOSTCC))
-  PLUGINCC := $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-plugin.sh "$(__PLUGINCC)" "$(HOSTCXX)" "$(CC)")
-
-  SANCOV_PLUGIN := -fplugin=$(objtree)/scripts/gcc-plugins/sancov_plugin.so
-
-  gcc-plugin-$(CONFIG_GCC_PLUGIN_CYC_COMPLEXITY)        += cyc_complexity_plugin.so
+gcc-plugin-$(CONFIG_GCC_PLUGIN_CYC_COMPLEXITY)  += cyc_complexity_plugin.so
 
-  gcc-plugin-$(CONFIG_GCC_PLUGIN_LATENT_ENTROPY)        += latent_entropy_plugin.so
-  gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_LATENT_ENTROPY) += -DLATENT_ENTROPY_PLUGIN
-  ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY
+gcc-plugin-$(CONFIG_GCC_PLUGIN_LATENT_ENTROPY)  += latent_entropy_plugin.so
+gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_LATENT_ENTROPY)   += -DLATENT_ENTROPY_PLUGIN
+ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY
     DISABLE_LATENT_ENTROPY_PLUGIN                       += -fplugin-arg-latent_entropy_plugin-disable
-  endif
-
-  ifdef CONFIG_GCC_PLUGIN_SANCOV
-      # It is needed because of the gcc-plugin.sh and gcc version checks.
-      gcc-plugin-$(CONFIG_GCC_PLUGIN_SANCOV)           += sancov_plugin.so
-
-      ifeq ($(PLUGINCC),)
-        $(warning warning: cannot use CONFIG_KCOV: -fsanitize-coverage=trace-pc is not supported by compiler)
-      endif
-  endif
-
-  gcc-plugin-$(CONFIG_GCC_PLUGIN_STRUCTLEAK)    += structleak_plugin.so
-  gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK_VERBOSE)     += -fplugin-arg-structleak_plugin-verbose
-  gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL)   += -fplugin-arg-structleak_plugin-byref-all
-  gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK)     += -DSTRUCTLEAK_PLUGIN
+endif
 
-  gcc-plugin-$(CONFIG_GCC_PLUGIN_RANDSTRUCT)    += randomize_layout_plugin.so
-  gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_RANDSTRUCT)     += -DRANDSTRUCT_PLUGIN
-  gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_RANDSTRUCT_PERFORMANCE) += -fplugin-arg-randomize_layout_plugin-performance-mode
+gcc-plugin-$(CONFIG_GCC_PLUGIN_SANCOV)          += sancov_plugin.so
+gcc-plugin-$(CONFIG_GCC_PLUGIN_STRUCTLEAK)      += structleak_plugin.so
+gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK_VERBOSE)       += -fplugin-arg-structleak_plugin-verbose
+gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL)     += -fplugin-arg-structleak_plugin-byref-all
+gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK)       += -DSTRUCTLEAK_PLUGIN
 
-  GCC_PLUGINS_CFLAGS := $(strip $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y)) $(gcc-plugin-cflags-y))
+gcc-plugin-$(CONFIG_GCC_PLUGIN_RANDSTRUCT)      += randomize_layout_plugin.so
+gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_RANDSTRUCT)       += -DRANDSTRUCT_PLUGIN
+gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_RANDSTRUCT_PERFORMANCE)   += -fplugin-arg-randomize_layout_plugin-performance-mode
 
-  export PLUGINCC GCC_PLUGINS_CFLAGS GCC_PLUGIN GCC_PLUGIN_SUBDIR
-  export DISABLE_LATENT_ENTROPY_PLUGIN
+GCC_PLUGINS_CFLAGS := $(strip $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y)) $(gcc-plugin-cflags-y))
 
-  ifneq ($(PLUGINCC),)
-    # SANCOV_PLUGIN can be only in CFLAGS_KCOV because avoid duplication.
-    GCC_PLUGINS_CFLAGS := $(filter-out $(SANCOV_PLUGIN), $(GCC_PLUGINS_CFLAGS))
-  endif
+export GCC_PLUGINS_CFLAGS GCC_PLUGIN GCC_PLUGIN_SUBDIR
+export DISABLE_LATENT_ENTROPY_PLUGIN
 
-  KBUILD_CFLAGS += $(GCC_PLUGINS_CFLAGS)
-  GCC_PLUGIN := $(gcc-plugin-y)
-  GCC_PLUGIN_SUBDIR := $(gcc-plugin-subdir-y)
-endif
+# sancov_plugin.so can be only in CFLAGS_KCOV because avoid duplication.
+GCC_PLUGINS_CFLAGS := $(filter-out %/sancov_plugin.so, $(GCC_PLUGINS_CFLAGS))
 
-# 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
-        @:
+KBUILD_CFLAGS += $(GCC_PLUGINS_CFLAGS)
+GCC_PLUGIN := $(gcc-plugin-y)
+GCC_PLUGIN_SUBDIR := $(gcc-plugin-subdir-y)
 
 # Actually do the build, if requested.
 PHONY += gcc-plugins
-gcc-plugins: scripts_basic gcc-plugins-check
+gcc-plugins: scripts_basic
 ifdef CONFIG_GCC_PLUGINS
         $(Q)$(MAKE) $(build)=scripts/gcc-plugins
 endif
diff --git a/scripts/gcc-plugins/Makefile b/scripts/gcc-plugins/Makefile
index ea465799ced5..326254653bd0 100644
--- a/scripts/gcc-plugins/Makefile
+++ b/scripts/gcc-plugins/Makefile
@@ -1,4 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
+PLUGINCC := $(CONFIG_PLUGIN_HOSTCC:"%"=%)
 GCC_PLUGINS_DIR := $(shell $(CC) -print-file-name=plugin)
 
 ifeq ($(PLUGINCC),$(HOSTCC))