Commit 0cecd37d authored by Kees Cook's avatar Kees Cook
Browse files

gcc-plugins: Force full rebuild when plugins change 

There was no dependency between the plugins changing and the rest of the
kernel being built. This could cause strange behaviors as instrumentation
could vary between targets depending on when they were built.

Generate a new header file, gcc-plugins.h, any time the GCC plugins
change. Include the header file in compiler-version.h when its associated
feature name, GCC_PLUGINS, is defined. This will be picked up by fixdep
and force rebuilds where needed.

Add a generic "touch" kbuild command, which will be used again in
a following patch. Add a "normalize_path" string helper to make the
"TOUCH" output less ugly.

Link: https://lore.kernel.org/r/20250503184623.2572355-1-kees@kernel.org


Tested-by: default avatarNicolas Schier <n.schier@avm.de>
Reviewed-by: default avatarNicolas Schier <n.schier@avm.de>
Signed-off-by: default avatarKees Cook <kees@kernel.org>
parent 5e88c48c

include/linux/compiler-version.h

+11 −0
Original line number Diff line number Diff line
@@ -12,3 +12,14 @@ 
 * and add dependency on include/config/CC_VERSION_TEXT, which is touched

 * by Kconfig when the version string from the compiler changes.

 */



/* Additional tree-wide dependencies start here. */



/*

 * If any of the GCC plugins change, we need to rebuild everything that

 * was built with them, as they may have changed their behavior and those

 * behaviors may need to be synchronized across all translation units.

 */

#ifdef GCC_PLUGINS

#include <generated/gcc-plugins.h>

#endif

scripts/Makefile.gcc-plugins

+1 −1
Original line number Diff line number Diff line
@@ -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)) -DGCC_PLUGINS

export GCC_PLUGINS_CFLAGS



# Add the flags to the build!

scripts/Makefile.lib

+18 −0
Original line number Diff line number Diff line
@@ -296,6 +296,19 @@ $(foreach m, $1, \ 
	$(addprefix $(obj)/, $(call suffix-search, $(patsubst $(obj)/%,%,$m), $2, $3))))

endef



# Remove ".." and "." from a path, without using "realpath"

# Usage:

#   $(call normalize_path,path/to/../file)

define normalize_path

$(strip $(eval elements :=) \

$(foreach elem,$(subst /, ,$1), \

	$(if $(filter-out .,$(elem)), \

	     $(if $(filter ..,$(elem)), \

		  $(eval elements := $(wordlist 2,$(words $(elements)),x $(elements))), \

		  $(eval elements := $(elements) $(elem))))) \

$(subst $(space),/,$(elements)))

endef



# Build commands

# ===========================================================================

# These are shared by some Makefile.* files.
@@ -343,6 +356,11 @@ quiet_cmd_copy = COPY $@ 
$(obj)/%: $(src)/%_shipped

	$(call cmd,copy)



# Touch a file

# ===========================================================================

quiet_cmd_touch = TOUCH   $(call normalize_path,$@)

      cmd_touch = touch $@



# Commands useful for building a boot image

# ===========================================================================

#

scripts/gcc-plugins/Makefile

+4 −0
Original line number Diff line number Diff line
@@ -66,3 +66,7 @@ quiet_cmd_plugin_cxx_o_c = HOSTCXX $@ 


$(plugin-objs): $(obj)/%.o: $(src)/%.c FORCE

	$(call if_changed_dep,plugin_cxx_o_c)



$(obj)/../../include/generated/gcc-plugins.h: $(plugin-single) $(plugin-multi) FORCE

	$(call if_changed,touch)

always-y += ../../include/generated/gcc-plugins.h