Commit 4e9903b0 authored by Masahiro Yamada's avatar Masahiro Yamada Committed by Kees Cook
Browse files

fortify: refactor test_fortify Makefile to fix some build problems 



There are some issues in the test_fortify Makefile code.

Problem 1: cc-disable-warning invokes compiler dozens of times

To see how many times the cc-disable-warning is evaluated, change
this code:

  $(call cc-disable-warning,fortify-source)

to:

  $(call cc-disable-warning,$(shell touch /tmp/fortify-$$$$)fortify-source)

Then, build the kernel with CONFIG_FORTIFY_SOURCE=y. You will see a
large number of '/tmp/fortify-<PID>' files created:

  $ ls -1 /tmp/fortify-* | wc
       80      80    1600

This means the compiler was invoked 80 times just for checking the
-Wno-fortify-source flag support.

$(call cc-disable-warning,fortify-source) should be added to a simple
variable instead of a recursive variable.

Problem 2: do not recompile string.o when the test code is updated

The test cases are independent of the kernel. However, when the test
code is updated, $(obj)/string.o is rebuilt and vmlinux is relinked
due to this dependency:

  $(obj)/string.o: $(obj)/$(TEST_FORTIFY_LOG)

always-y is suitable for building the log files.

Problem 3: redundant code

  clean-files += $(addsuffix .o, $(TEST_FORTIFY_LOGS))

... is unneeded because the top Makefile globally cleans *.o files.

This commit fixes these issues and makes the code readable.

Signed-off-by: default avatarMasahiro Yamada <masahiroy@kernel.org>
Link: https://lore.kernel.org/r/20240727150302.1823750-2-masahiroy@kernel.org


Signed-off-by: default avatarKees Cook <kees@kernel.org>
parent de9c2c66

lib/.gitignore

+0 −2
Original line number Diff line number Diff line
@@ -5,5 +5,3 @@ 
/gen_crc32table

/gen_crc64table

/oid_registry_data.c
 
/test_fortify.log

/test_fortify/*.log

lib/Makefile

+1 −37
Original line number Diff line number Diff line
@@ -393,40 +393,4 @@ obj-$(CONFIG_GENERIC_LIB_DEVMEM_IS_ALLOWED) += devmem_is_allowed.o 


obj-$(CONFIG_FIRMWARE_TABLE) += fw_table.o



# FORTIFY_SOURCE compile-time behavior tests

TEST_FORTIFY_SRCS = $(wildcard $(src)/test_fortify/*-*.c)

TEST_FORTIFY_LOGS = $(patsubst $(src)/%.c, %.log, $(TEST_FORTIFY_SRCS))

TEST_FORTIFY_LOG = test_fortify.log



quiet_cmd_test_fortify = TEST    $@

      cmd_test_fortify = $(CONFIG_SHELL) $(srctree)/scripts/test_fortify.sh \

			$< $@ "$(NM)" $(CC) $(c_flags) \

			$(call cc-disable-warning,fortify-source) \

			-DKBUILD_EXTRA_WARN1



targets += $(TEST_FORTIFY_LOGS)

clean-files += $(TEST_FORTIFY_LOGS)

clean-files += $(addsuffix .o, $(TEST_FORTIFY_LOGS))

$(obj)/test_fortify/%.log: $(src)/test_fortify/%.c \

			   $(src)/test_fortify/test_fortify.h \

			   $(srctree)/include/linux/fortify-string.h \

			   $(srctree)/scripts/test_fortify.sh \

			   FORCE

	$(call if_changed,test_fortify)



quiet_cmd_gen_fortify_log = GEN     $@

      cmd_gen_fortify_log = cat </dev/null $(filter-out FORCE,$^) 2>/dev/null > $@ || true



targets += $(TEST_FORTIFY_LOG)

clean-files += $(TEST_FORTIFY_LOG)

$(obj)/$(TEST_FORTIFY_LOG): $(addprefix $(obj)/, $(TEST_FORTIFY_LOGS)) FORCE

	$(call if_changed,gen_fortify_log)



# Fake dependency to trigger the fortify tests.

ifeq ($(CONFIG_FORTIFY_SOURCE),y)

$(obj)/string.o: $(obj)/$(TEST_FORTIFY_LOG)

endif



# Some architectures define __NO_FORTIFY if __SANITIZE_ADDRESS__ is undefined.

# Pass CFLAGS_KASAN to avoid warnings.

$(foreach x, $(patsubst %.log,%.o,$(TEST_FORTIFY_LOGS)), $(eval KASAN_SANITIZE_$(x) := y))
 
subdir-$(CONFIG_FORTIFY_SOURCE) += test_fortify

lib/test_fortify/.gitignore

0 → 100644
+2 −0
Original line number Diff line number Diff line 
# SPDX-License-Identifier: GPL-2.0-only

/*.log

lib/test_fortify/Makefile

0 → 100644
+28 −0
Original line number Diff line number Diff line 
# SPDX-License-Identifier: GPL-2.0



ccflags-y := $(call cc-disable-warning,fortify-source)



quiet_cmd_test_fortify = TEST    $@

      cmd_test_fortify = $(CONFIG_SHELL) $(srctree)/scripts/test_fortify.sh \

			$< $@ "$(NM)" $(CC) $(c_flags) -DKBUILD_EXTRA_WARN1



$(obj)/%.log: $(src)/%.c $(srctree)/scripts/test_fortify.sh \

	      $(src)/test_fortify.h \

	      $(srctree)/include/linux/fortify-string.h \

	      FORCE

	$(call if_changed,test_fortify)



logs = $(patsubst $(src)/%.c, %.log, $(wildcard $(src)/*-*.c))

targets += $(logs)



quiet_cmd_gen_fortify_log = CAT     $@

      cmd_gen_fortify_log = cat $(or $(real-prereqs),/dev/null) > $@



$(obj)/test_fortify.log: $(addprefix $(obj)/, $(logs)) FORCE

	$(call if_changed,gen_fortify_log)



always-y += test_fortify.log



# Some architectures define __NO_FORTIFY if __SANITIZE_ADDRESS__ is undefined.

# Pass CFLAGS_KASAN to avoid warnings.

KASAN_SANITIZE := y

scripts/remove-stale-files

+2 −0
Original line number Diff line number Diff line
@@ -21,3 +21,5 @@ set -e 
# then will be really dead and removed from the code base entirely.



rm -f *.spec



rm -f lib/test_fortify.log