Message-Id: <20200329110832.19961-1-masahiroy@kernel.org>
Date:   Sun, 29 Mar 2020 20:08:32 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     linux-kbuild@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Emese Revfy <re.emese@...il.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        kernel-hardening@...ts.openwall.com
Subject: [PATCH] gcc-plugins: drop support for GCC <= 4.7

Nobody was opposed to raising minimum GCC version to 4.8 [1]
So, we will drop GCC <= 4.7 support sooner or later.

We always use C++ compiler for building plugins for GCC >= 4.8.

This commit drops the plugin support for GCC <= 4.7 a bit earlier,
which allows us to dump lots of code.

[1] https://lkml.org/lkml/2020/1/23/545

Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---

This patch depends on this:
https://patchwork.kernel.org/patch/11456871/

 scripts/Kconfig.include      |  3 --
 scripts/Makefile.build       |  2 +-
 scripts/Makefile.clean       |  1 -
 scripts/Makefile.host        | 23 +--------------
 scripts/gcc-plugin.sh        | 55 +++---------------------------------
 scripts/gcc-plugins/Kconfig  | 12 ++------
 scripts/gcc-plugins/Makefile | 21 ++++----------
 7 files changed, 14 insertions(+), 103 deletions(-)

diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
index 496d11c92c97..033f6efd92d3 100644
--- a/scripts/Kconfig.include
+++ b/scripts/Kconfig.include
@@ -42,9 +42,6 @@ $(error-if,$(failure,command -v $(LD)),linker '$(LD)' not found)
 # Fail if the linker is gold as it's not capable of linking the kernel proper
 $(error-if,$(success, $(LD) -v | grep -q gold), gold linker '$(LD)' not supported)
 
-# gcc version including patch level
-gcc-version := $(shell,$(srctree)/scripts/gcc-version.sh $(CC))
-
 # machine bit flags
 #  $(m32-flag): -m32 if the compiler supports it, or an empty string otherwise.
 #  $(m64-flag): -m64 if the compiler supports it, or an empty string otherwise.
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 356601994f3a..9fcbfac15d1d 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -46,7 +46,7 @@ include $(kbuild-file)
 include scripts/Makefile.lib
 
 # Do not include host rules unless needed
-ifneq ($(hostprogs)$(hostlibs-y)$(hostlibs-m)$(hostcxxlibs-y)$(hostcxxlibs-m),)
+ifneq ($(hostprogs)$(hostcxxlibs-y)$(hostcxxlibs-m),)
 include scripts/Makefile.host
 endif
 
diff --git a/scripts/Makefile.clean b/scripts/Makefile.clean
index 1e4206566a82..075f0cc2d8d7 100644
--- a/scripts/Makefile.clean
+++ b/scripts/Makefile.clean
@@ -30,7 +30,6 @@ subdir-ymn	:= $(addprefix $(obj)/,$(subdir-ymn))
 __clean-files	:= $(extra-y) $(extra-m) $(extra-)       \
 		   $(always) $(always-y) $(always-m) $(always-) $(targets) $(clean-files)   \
 		   $(hostprogs) $(hostprogs-y) $(hostprogs-m) $(hostprogs-) \
-		   $(hostlibs-y) $(hostlibs-m) $(hostlibs-) \
 		   $(hostcxxlibs-y) $(hostcxxlibs-m)
 
 __clean-files   := $(filter-out $(no-clean-files), $(__clean-files))
diff --git a/scripts/Makefile.host b/scripts/Makefile.host
index 3b7121d43324..2045855d0b75 100644
--- a/scripts/Makefile.host
+++ b/scripts/Makefile.host
@@ -39,7 +39,6 @@ $(obj)/%.tab.c $(obj)/%.tab.h: $(src)/%.y FORCE
 # They are linked as C++ code to the executable qconf
 
 __hostprogs := $(sort $(hostprogs))
-host-cshlib := $(sort $(hostlibs-y) $(hostlibs-m))
 host-cxxshlib := $(sort $(hostcxxlibs-y) $(hostcxxlibs-m))
 
 # C code
@@ -63,7 +62,6 @@ host-cxxmulti	:= $(foreach m,$(__hostprogs),$(if $($(m)-cxxobjs),$(m)))
 host-cxxobjs	:= $(sort $(foreach m,$(host-cxxmulti),$($(m)-cxxobjs)))
 
 # Object (.o) files used by the shared libaries
-host-cshobjs	:= $(sort $(foreach m,$(host-cshlib),$($(m:.so=-objs))))
 host-cxxshobjs	:= $(sort $(foreach m,$(host-cxxshlib),$($(m:.so=-objs))))
 
 host-csingle	:= $(addprefix $(obj)/,$(host-csingle))
@@ -71,9 +69,7 @@ host-cmulti	:= $(addprefix $(obj)/,$(host-cmulti))
 host-cobjs	:= $(addprefix $(obj)/,$(host-cobjs))
 host-cxxmulti	:= $(addprefix $(obj)/,$(host-cxxmulti))
 host-cxxobjs	:= $(addprefix $(obj)/,$(host-cxxobjs))
-host-cshlib	:= $(addprefix $(obj)/,$(host-cshlib))
 host-cxxshlib	:= $(addprefix $(obj)/,$(host-cxxshlib))
-host-cshobjs	:= $(addprefix $(obj)/,$(host-cshobjs))
 host-cxxshobjs	:= $(addprefix $(obj)/,$(host-cxxshobjs))
 
 #####
@@ -140,13 +136,6 @@ quiet_cmd_host-cxxobjs	= HOSTCXX $@
 $(host-cxxobjs): $(obj)/%.o: $(src)/%.cc FORCE
 	$(call if_changed_dep,host-cxxobjs)
 
-# Compile .c file, create position independent .o file
-# host-cshobjs -> .o
-quiet_cmd_host-cshobjs	= HOSTCC  -fPIC $@
-      cmd_host-cshobjs	= $(HOSTCC) $(hostc_flags) -fPIC -c -o $@ $<
-$(host-cshobjs): $(obj)/%.o: $(src)/%.c FORCE
-	$(call if_changed_dep,host-cshobjs)
-
 # Compile .c file, create position independent .o file
 # Note that plugin capable gcc versions can be either C or C++ based
 # therefore plugin source files have to be compilable in both C and C++ mode.
@@ -157,16 +146,6 @@ quiet_cmd_host-cxxshobjs	= HOSTCXX -fPIC $@
 $(host-cxxshobjs): $(obj)/%.o: $(src)/%.c FORCE
 	$(call if_changed_dep,host-cxxshobjs)
 
-# Link a shared library, based on position independent .o files
-# *.o -> .so shared library (host-cshlib)
-quiet_cmd_host-cshlib	= HOSTLLD -shared $@
-      cmd_host-cshlib	= $(HOSTCC) $(KBUILD_HOSTLDFLAGS) -shared -o $@ \
-			  $(addprefix $(obj)/, $($(target-stem)-objs)) \
-			  $(KBUILD_HOSTLDLIBS) $(HOSTLDLIBS_$(target-stem).so)
-$(host-cshlib): FORCE
-	$(call if_changed,host-cshlib)
-$(call multi_depend, $(host-cshlib), .so, -objs)
-
 # Link a shared library, based on position independent .o files
 # *.o -> .so shared library (host-cxxshlib)
 quiet_cmd_host-cxxshlib	= HOSTLLD -shared $@
@@ -178,4 +157,4 @@ $(host-cxxshlib): FORCE
 $(call multi_depend, $(host-cxxshlib), .so, -objs)
 
 targets += $(host-csingle)  $(host-cmulti) $(host-cobjs)\
-	   $(host-cxxmulti) $(host-cxxobjs) $(host-cshlib) $(host-cshobjs) $(host-cxxshlib) $(host-cxxshobjs)
+	   $(host-cxxmulti) $(host-cxxobjs) $(host-cxxshlib) $(host-cxxshobjs)
diff --git a/scripts/gcc-plugin.sh b/scripts/gcc-plugin.sh
index d3caefe53eab..b79fd0bea838 100755
--- a/scripts/gcc-plugin.sh
+++ b/scripts/gcc-plugin.sh
@@ -1,49 +1,14 @@
 #!/bin/sh
 # SPDX-License-Identifier: GPL-2.0
-srctree=$(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"
-#if BUILDING_GCC_VERSION >= 4008 || defined(ENABLE_BUILD_WITH_CXX)
-#warning $2 CXX
-#else
-#warning $1 CC
-#endif
-EOF
-)
 
-if [ $? -ne 0 ]
-then
-	if [ -n "$SHOW_ERROR" ] ; then
-		echo "${plugincc}" >&2
-	fi
-	exit 1
-fi
+set -e
 
-case "$plugincc" in
-	*"$1 CC"*)
-		echo "$1"
-		exit 0
-		;;
-
-	*"$2 CXX"*)
-		# the c++ compiler needs another test, see below
-		;;
+srctree=$(dirname "$0")
 
-	*)
-		exit 1
-		;;
-esac
+gccplugins_dir=$($* -print-file-name=plugin)
 
 # we need a c++ compiler that supports the designated initializer GNU extension
-plugincc=$($2 -c -x c++ -std=gnu++98 - -fsyntax-only -I"${srctree}"/gcc-plugins -I"${gccplugins_dir}"/include 2>&1 <<EOF
+$HOSTCC -c -x c++ -std=gnu++98 - -fsyntax-only -I $srctree/gcc-plugins -I $gccplugins_dir/include 2>/dev/null <<EOF
 #include "gcc-common.h"
 class test {
 public:
@@ -52,15 +17,3 @@ public:
 	.test = 1
 };
 EOF
-)
-
-if [ $? -eq 0 ]
-then
-	echo "$2"
-	exit 0
-fi
-
-if [ -n "$SHOW_ERROR" ] ; then
-	echo "${plugincc}" >&2
-fi
-exit 1
diff --git a/scripts/gcc-plugins/Kconfig b/scripts/gcc-plugins/Kconfig
index 7b63c819610c..a857d69322b4 100644
--- a/scripts/gcc-plugins/Kconfig
+++ b/scripts/gcc-plugins/Kconfig
@@ -1,13 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0-only
-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)")" if CC_IS_GCC
-	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
@@ -17,7 +8,8 @@ config HAVE_GCC_PLUGINS
 menuconfig GCC_PLUGINS
 	bool "GCC plugins"
 	depends on HAVE_GCC_PLUGINS
-	depends on PLUGIN_HOSTCC != ""
+	depends on CC_IS_GCC && GCC_VERSION >= 40800
+	depends on $(success,$(srctree)/scripts/gcc-plugin.sh $(CC))
 	default y
 	help
 	  GCC plugins are loadable modules that provide extra features to the
diff --git a/scripts/gcc-plugins/Makefile b/scripts/gcc-plugins/Makefile
index efff00959a9c..f22858b2c3d6 100644
--- a/scripts/gcc-plugins/Makefile
+++ b/scripts/gcc-plugins/Makefile
@@ -1,18 +1,9 @@
 # SPDX-License-Identifier: GPL-2.0
-PLUGINCC := $(CONFIG_PLUGIN_HOSTCC:"%"=%)
 GCC_PLUGINS_DIR := $(shell $(CC) -print-file-name=plugin)
 
-ifeq ($(PLUGINCC),$(HOSTCC))
-  HOSTLIBS := hostlibs
-  HOST_EXTRACFLAGS += -I$(GCC_PLUGINS_DIR)/include -I$(src) -std=gnu99 -ggdb
-  export HOST_EXTRACFLAGS
-else
-  HOSTLIBS := hostcxxlibs
-  HOST_EXTRACXXFLAGS += -I$(GCC_PLUGINS_DIR)/include -I$(src) -std=gnu++98 -fno-rtti
-  HOST_EXTRACXXFLAGS += -fno-exceptions -fasynchronous-unwind-tables -ggdb
-  HOST_EXTRACXXFLAGS += -Wno-narrowing -Wno-unused-variable -Wno-c++11-compat
-  export HOST_EXTRACXXFLAGS
-endif
+HOST_EXTRACXXFLAGS += -I$(GCC_PLUGINS_DIR)/include -I$(src) -std=gnu++98 -fno-rtti
+HOST_EXTRACXXFLAGS += -fno-exceptions -fasynchronous-unwind-tables -ggdb
+HOST_EXTRACXXFLAGS += -Wno-narrowing -Wno-unused-variable -Wno-c++11-compat
 
 $(obj)/randomize_layout_plugin.o: $(objtree)/$(obj)/randomize_layout_seed.h
 quiet_cmd_create_randomize_layout_seed = GENSEED $@
@@ -22,9 +13,9 @@ $(objtree)/$(obj)/randomize_layout_seed.h: FORCE
 	$(call if_changed,create_randomize_layout_seed)
 targets = randomize_layout_seed.h randomize_layout_hash.h
 
-$(HOSTLIBS)-y := $(foreach p,$(GCC_PLUGIN),$(if $(findstring /,$(p)),,$(p)))
-always-y := $($(HOSTLIBS)-y)
+hostcxxlibs-y := $(foreach p,$(GCC_PLUGIN),$(if $(findstring /,$(p)),,$(p)))
+always-y := $(hostcxxlibs-y)
 
-$(foreach p,$($(HOSTLIBS)-y:%.so=%),$(eval $(p)-objs := $(p).o))
+$(foreach p,$(hostcxxlibs-y:%.so=%),$(eval $(p)-objs := $(p).o))
 
 clean-files += *.so
-- 
2.17.1

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