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Sam James 5a6b64adc1 gcc-plugins: drop -std=gnu++11 to fix GCC 13 build

The latest GCC 13 snapshot (13.0.1 20230129) gives the following:
```
cc1: error: cannot load plugin ./scripts/gcc-plugins/randomize_layout_plugin.so
 :./scripts/gcc-plugins/randomize_layout_plugin.so: undefined symbol: tree_code_type
```

This ends up being because of https://gcc.gnu.org/git/gitweb.cgi?p=gcc.git;h=b0241ce6e37031
upstream in GCC which changes the visibility of some types used by the kernel's
plugin infrastructure like tree_code_type.

After discussion with the GCC folks, we found that the kernel needs to be building
plugins with the same flags used to build GCC - and GCC defaults to gnu++17
right now. The minimum GCC version needed to build the kernel is GCC 5.1
and GCC 5.1 already defaults to gnu++14 anyway, so just drop the flag, as
all GCCs that could be used to build GCC already default to an acceptable
version which was >= the version we forced via flags until now.

Bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108634
Signed-off-by: Sam James <sam@gentoo.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230201230009.2252783-1-sam@gentoo.org

2023-02-02 16:31:23 +00:00

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SPDX-License-Identifier: GPL-2.0

$(obj)/randomize_layout_plugin.so: $(obj)/randomize_layout_seed.h quiet_cmd_create_randomize_layout_seed = SEEDHDR $@ cmd_create_randomize_layout_seed =
SEED=$$(cat $(filter-out FORCE,$^) </dev/null);
echo '/*' > $@;
echo ' * This file is automatically generated. Keep it private.' >> $@;
echo ' * Exposing this value will expose the layout of randomized structures.' >> $@;
echo ' */' >> $@;
echo "const char *randstruct_seed = "$$SEED";" >> $@ $(obj)/randomize_layout_seed.h: $(objtree)/scripts/basic/randstruct.seed FORCE $(call if_changed,create_randomize_layout_seed) targets += randomize_layout_seed.h

Build rules for plugins

No extra code is needed for single-file plugins.

For multi-file plugins, use *-objs syntax to list the objects.

If the plugin foo.so is compiled from foo.c and foo2.c, you can do:

foo-objs := foo.o foo2.o

always-y += $(GCC_PLUGIN)

GCC_PLUGINS_DIR = $(shell $(CC) -print-file-name=plugin)

plugin_cxxflags = -Wp,-MMD,$(depfile) $(KBUILD_HOSTCXXFLAGS) -fPIC
-include $(srctree)/include/linux/compiler-version.h
-DPLUGIN_VERSION=$(call stringify,$(KERNELVERSION))
-I $(GCC_PLUGINS_DIR)/include -I $(obj)
-fno-rtti -fno-exceptions -fasynchronous-unwind-tables
-ggdb -Wno-narrowing -Wno-unused-variable
-Wno-format-diag

plugin_ldflags = -shared

plugin-single := $(foreach m, $(GCC_PLUGIN), $(if $($(m:%.so=%-objs)),,$(m))) plugin-multi := $(filter-out $(plugin-single), $(GCC_PLUGIN)) plugin-objs := $(sort $(foreach m, $(plugin-multi), $($(m:%.so=%-objs))))

targets += $(plugin-single) $(plugin-multi) $(plugin-objs) clean-files += *.so

plugin-single := $(addprefix $(obj)/, $(plugin-single)) plugin-multi := $(addprefix $(obj)/, $(plugin-multi)) plugin-objs := $(addprefix $(obj)/, $(plugin-objs))

quiet_cmd_plugin_cxx_so_c = HOSTCXX $@ cmd_plugin_cxx_so_c = $(HOSTCXX) $(plugin_cxxflags) $(plugin_ldflags) -o $@ $<

$(plugin-single): $(obj)/%.so: $(src)/%.c FORCE $(call if_changed_dep,plugin_cxx_so_c)

quiet_cmd_plugin_ld_so_o = HOSTLD $@ cmd_plugin_ld_so_o = $(HOSTCXX) $(plugin_ldflags) -o $@
$(addprefix $(obj)/, $($(target-stem)-objs))

$(plugin-multi): FORCE $(call if_changed,plugin_ld_so_o) $(foreach m, $(notdir $(plugin-multi)), $(eval $(obj)/$m: $(addprefix $(obj)/, $($(m:%.so=%-objs)))))

quiet_cmd_plugin_cxx_o_c = HOSTCXX $@ cmd_plugin_cxx_o_c = $(HOSTCXX) $(plugin_cxxflags) -c -o $@ $<

$(plugin-objs): $(obj)/%.o: $(src)/%.c FORCE $(call if_changed_dep,plugin_cxx_o_c)

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