From 893ab00439a45513cae55781fc8e3b7108ee1cda Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Sat, 27 Jun 2020 03:59:12 +0900 Subject: kbuild: remove cc-option test of -fno-stack-protector Some Makefiles already pass -fno-stack-protector unconditionally. For example, arch/arm64/kernel/vdso/Makefile, arch/x86/xen/Makefile. No problem report so far about hard-coding this option. So, we can assume all supported compilers know -fno-stack-protector. GCC 4.8 and Clang support this option (https://godbolt.org/z/_HDGzN) Get rid of cc-option from -fno-stack-protector. Remove CONFIG_CC_HAS_STACKPROTECTOR_NONE, which is always 'y'. Note: arch/mips/vdso/Makefile adds -fno-stack-protector twice, first unconditionally, and second conditionally. I removed the second one. Signed-off-by: Masahiro Yamada Reviewed-by: Kees Cook Acked-by: Ard Biesheuvel Reviewed-by: Nick Desaulniers --- arch/arm/boot/compressed/Makefile | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'arch/arm') diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile index 00602a6fba04..cb7a56c6723c 100644 --- a/arch/arm/boot/compressed/Makefile +++ b/arch/arm/boot/compressed/Makefile @@ -84,9 +84,8 @@ endif # -fstack-protector-strong triggers protection checks in this code, # but it is being used too early to link to meaningful stack_chk logic. -nossp-flags-$(CONFIG_CC_HAS_STACKPROTECTOR_NONE) := -fno-stack-protector $(foreach o, $(libfdt_objs) atags_to_fdt.o, \ - $(eval CFLAGS_$(o) := -I $(srctree)/scripts/dtc/libfdt $(nossp-flags-y))) + $(eval CFLAGS_$(o) := -I $(srctree)/scripts/dtc/libfdt -fno-stack-protector)) # These were previously generated C files. When you are building the kernel # with O=, make sure to remove the stale files in the output tree. Otherwise, -- cgit v1.2.3 From 15d5761ad31dfb194ebe76554e6af0437eb20424 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Tue, 7 Jul 2020 18:21:16 +0900 Subject: kbuild: introduce ccflags-remove-y and asflags-remove-y CFLAGS_REMOVE_.o filters out flags when compiling a particular object, but there is no convenient way to do that for every object in a directory. Add ccflags-remove-y and asflags-remove-y to make it easily. Use ccflags-remove-y to clean up some Makefiles. The add/remove order works as follows: [1] KBUILD_CFLAGS specifies compiler flags used globally [2] ccflags-y adds compiler flags for all objects in the current Makefile [3] ccflags-remove-y removes compiler flags for all objects in the current Makefile (New feature) [4] CFLAGS_ adds compiler flags per file. [5] CFLAGS_REMOVE_ removes compiler flags per file. Having [3] before [4] allows us to remove flags from most (but not all) objects in the current Makefile. For example, kernel/trace/Makefile removes $(CC_FLAGS_FTRACE) from all objects in the directory, then adds it back to trace_selftest_dynamic.o and CFLAGS_trace_kprobe_selftest.o The same applies to lib/livepatch/Makefile. Please note ccflags-remove-y has no effect to the sub-directories. In contrast, the previous notation got rid of compiler flags also from all the sub-directories. The following are not affected because they have no sub-directories: arch/arm/boot/compressed/ arch/powerpc/xmon/ arch/sh/ kernel/trace/ However, lib/ has several sub-directories. To keep the behavior, I added ccflags-remove-y to all Makefiles in subdirectories of lib/, except the following: lib/vdso/Makefile - Kbuild does not descend into this Makefile lib/raid/test/Makefile - This is not used for the kernel build I think commit 2464a609ded0 ("ftrace: do not trace library functions") excluded too much. In the next commit, I will remove ccflags-remove-y from the sub-directories of lib/. Suggested-by: Sami Tolvanen Signed-off-by: Masahiro Yamada Acked-by: Steven Rostedt (VMware) Acked-by: Michael Ellerman (powerpc) Acked-by: Brendan Higgins (KUnit) Tested-by: Anders Roxell --- arch/arm/boot/compressed/Makefile | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) (limited to 'arch/arm') diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile index cb7a56c6723c..b1147b7f2c8d 100644 --- a/arch/arm/boot/compressed/Makefile +++ b/arch/arm/boot/compressed/Makefile @@ -102,13 +102,9 @@ clean-files += piggy_data lib1funcs.S ashldi3.S bswapsdi2.S hyp-stub.S KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING -ifeq ($(CONFIG_FUNCTION_TRACER),y) -ORIG_CFLAGS := $(KBUILD_CFLAGS) -KBUILD_CFLAGS = $(subst -pg, , $(ORIG_CFLAGS)) -endif - ccflags-y := -fpic $(call cc-option,-mno-single-pic-base,) -fno-builtin \ -I$(obj) $(DISABLE_ARM_SSP_PER_TASK_PLUGIN) +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += -pg asflags-y := -DZIMAGE # Supply kernel BSS size to the decompressor via a linker symbol. -- cgit v1.2.3