From d8285639550578a1bf2d102391d1a9e08e0586ca Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Sun, 25 Jul 2021 03:35:56 +0900 Subject: kbuild: do not require sub-make for separate output tree builds As explained in commit 3204a7fb98a3 ("kbuild: prefix $(srctree)/ to some included Makefiles"), I want to stop using --include-dir some day. I already fixed up the top Makefile, but some arch Makefiles (mips, um, x86) still include check-in Makefiles without $(srctree)/. Fix them up so 'need-sub-make := 1' can go away for this case. Signed-off-by: Masahiro Yamada --- Makefile | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) (limited to 'Makefile') diff --git a/Makefile b/Makefile index eae1314a5b86..185ce47d6734 100644 --- a/Makefile +++ b/Makefile @@ -191,10 +191,9 @@ endif ifneq ($(abs_srctree),$(abs_objtree)) # Look for make include files relative to root of kernel src # -# This does not become effective immediately because MAKEFLAGS is re-parsed -# once after the Makefile is read. We need to invoke sub-make. +# --included-dir is added for backward compatibility, but you should not rely on +# it. Please add $(srctree)/ prefix to include Makefiles in the source tree. MAKEFLAGS += --include-dir=$(abs_srctree) -need-sub-make := 1 endif ifneq ($(filter 3.%,$(MAKE_VERSION)),) -- cgit v1.2.3-70-g09d2 From 6072b2c49d23eb69b6dca06ad095d3a9633b2b80 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Sun, 1 Aug 2021 11:53:46 +0900 Subject: kbuild: warn if a different compiler is used for external module builds It is always safe to use the same compiler for the kernel and external modules, but in reality, some distributions such as Fedora release a different version of GCC from the one used for building the kernel. There was a long discussion about mixing different compilers [1]. I do not repeat it here, but at least, showing a heads up in that case is better than nothing. Linus suggested [2]: And a warning might be more palatable even if different compiler version work fine together. Just a heads up on "it looks like you might be mixing compiler versions" is a valid note, and isn't necessarily wrong. Even when they work well together, maybe you want to have people at least _aware_ of it. This commit shows a warning unless the compiler is exactly the same. warning: the compiler differs from the one used to build the kernel The kernel was built by: gcc (GCC) 11.1.1 20210531 (Red Hat 11.1.1-3) You are using: gcc (GCC) 11.2.1 20210728 (Red Hat 11.2.1-1) Check the difference, and if it is OK with you, please proceed at your risk. To avoid the locale issue as in commit bcbcf50f5218 ("kbuild: fix ld-version.sh to not be affected by locale"), pass LC_ALL=C to "$(CC) --version". [1] https://lore.kernel.org/linux-hardening/efe6b039a544da8215d5e54aa7c4b6d1986fc2b0.1611607264.git.jpoimboe@redhat.com/ [2] https://lore.kernel.org/lkml/CAHk-=wgjwhDy-y4mQh34L+2aF=n6BjzHdqAW2=8wri5x7O04pA@mail.gmail.com/ Acked-by: Josh Poimboeuf Signed-off-by: Masahiro Yamada --- Makefile | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) (limited to 'Makefile') diff --git a/Makefile b/Makefile index 185ce47d6734..a0376430da20 100644 --- a/Makefile +++ b/Makefile @@ -581,7 +581,7 @@ endif # Some architectures define CROSS_COMPILE in arch/$(SRCARCH)/Makefile. # CC_VERSION_TEXT is referenced from Kconfig (so it needs export), # and from include/config/auto.conf.cmd to detect the compiler upgrade. -CC_VERSION_TEXT = $(subst $(pound),,$(shell $(CC) --version 2>/dev/null | head -n 1)) +CC_VERSION_TEXT = $(subst $(pound),,$(shell LC_ALL=C $(CC) --version 2>/dev/null | head -n 1)) ifneq ($(findstring clang,$(CC_VERSION_TEXT)),) ifneq ($(CROSS_COMPILE),) @@ -1739,6 +1739,16 @@ clean-dirs := $(KBUILD_EXTMOD) clean: rm-files := $(KBUILD_EXTMOD)/Module.symvers $(KBUILD_EXTMOD)/modules.nsdeps \ $(KBUILD_EXTMOD)/compile_commands.json $(KBUILD_EXTMOD)/.thinlto-cache +PHONY += prepare +# now expand this into a simple variable to reduce the cost of shell evaluations +prepare: CC_VERSION_TEXT := $(CC_VERSION_TEXT) +prepare: + @if [ "$(CC_VERSION_TEXT)" != $(CONFIG_CC_VERSION_TEXT) ]; then \ + echo >&2 "warning: the compiler differs from the one used to build the kernel"; \ + echo >&2 " The kernel was built by: "$(CONFIG_CC_VERSION_TEXT); \ + echo >&2 " You are using: $(CC_VERSION_TEXT)"; \ + fi + PHONY += help help: @echo ' Building external modules.' @@ -1750,7 +1760,7 @@ help: @echo '' # no-op for external module builds -PHONY += prepare modules_prepare +PHONY += modules_prepare endif # KBUILD_EXTMOD -- cgit v1.2.3-70-g09d2 From 6f5b41a2f5a6314614e286274eb8e985248aac60 Mon Sep 17 00:00:00 2001 From: Nick Desaulniers Date: Mon, 2 Aug 2021 11:39:08 -0700 Subject: Makefile: move initial clang flag handling into scripts/Makefile.clang With some of the changes we'd like to make to CROSS_COMPILE, the initial block of clang flag handling which controls things like the target triple, whether or not to use the integrated assembler and how to find GAS, and erroring on unknown warnings is becoming unwieldy. Move it into its own file under scripts/. Reviewed-by: Nathan Chancellor Signed-off-by: Nick Desaulniers Signed-off-by: Masahiro Yamada --- MAINTAINERS | 1 + Makefile | 15 +-------------- scripts/Makefile.clang | 14 ++++++++++++++ 3 files changed, 16 insertions(+), 14 deletions(-) create mode 100644 scripts/Makefile.clang (limited to 'Makefile') diff --git a/MAINTAINERS b/MAINTAINERS index c9467d2839f5..3105fc57689e 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -4501,6 +4501,7 @@ B: https://github.com/ClangBuiltLinux/linux/issues C: irc://chat.freenode.net/clangbuiltlinux F: Documentation/kbuild/llvm.rst F: include/linux/compiler-clang.h +F: scripts/Makefile.clang F: scripts/clang-tools/ K: \b(?i:clang|llvm)\b diff --git a/Makefile b/Makefile index a0376430da20..f5419ce69ce8 100644 --- a/Makefile +++ b/Makefile @@ -584,20 +584,7 @@ endif CC_VERSION_TEXT = $(subst $(pound),,$(shell LC_ALL=C $(CC) --version 2>/dev/null | head -n 1)) ifneq ($(findstring clang,$(CC_VERSION_TEXT)),) -ifneq ($(CROSS_COMPILE),) -CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) -endif -ifeq ($(LLVM_IAS),1) -CLANG_FLAGS += -integrated-as -else -CLANG_FLAGS += -no-integrated-as -GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit)) -CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE)) -endif -CLANG_FLAGS += -Werror=unknown-warning-option -KBUILD_CFLAGS += $(CLANG_FLAGS) -KBUILD_AFLAGS += $(CLANG_FLAGS) -export CLANG_FLAGS +include $(srctree)/scripts/Makefile.clang endif # Include this also for config targets because some architectures need diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang new file mode 100644 index 000000000000..297932e973d4 --- /dev/null +++ b/scripts/Makefile.clang @@ -0,0 +1,14 @@ +ifneq ($(CROSS_COMPILE),) +CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) +endif +ifeq ($(LLVM_IAS),1) +CLANG_FLAGS += -integrated-as +else +CLANG_FLAGS += -no-integrated-as +GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit)) +CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE)) +endif +CLANG_FLAGS += -Werror=unknown-warning-option +KBUILD_CFLAGS += $(CLANG_FLAGS) +KBUILD_AFLAGS += $(CLANG_FLAGS) +export CLANG_FLAGS -- cgit v1.2.3-70-g09d2 From 52cc02b910284d6bddba46cce402044ab775f314 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Fri, 6 Aug 2021 00:01:02 +0900 Subject: kbuild: check CONFIG_AS_IS_LLVM instead of LLVM_IAS LLVM_IAS is the user interface to set the -(no-)integrated-as flag, and it should be used only for that purpose. LLVM_IAS is checked in some places to determine the assembler type, but it is not precise. For example, $ make CC=gcc LLVM_IAS=1 ... will use the GNU assembler (i.e. binutils) since LLVM_IAS=1 is effective only when $(CC) is clang. Of course, 'CC=gcc LLVM_IAS=1' is an odd combination, but the build system can be more robust against such insane input. Commit ba64beb17493a ("kbuild: check the minimum assembler version in Kconfig") introduced CONFIG_AS_IS_GNU/LLVM, which is more precise because Kconfig checks the version string from the assembler in use. Signed-off-by: Masahiro Yamada Reviewed-by: Nick Desaulniers Reviewed-by: Nathan Chancellor --- Makefile | 2 +- arch/riscv/Makefile | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) (limited to 'Makefile') diff --git a/Makefile b/Makefile index f5419ce69ce8..891866af0787 100644 --- a/Makefile +++ b/Makefile @@ -843,7 +843,7 @@ else DEBUG_CFLAGS += -g endif -ifneq ($(LLVM_IAS),1) +ifndef CONFIG_AS_IS_LLVM KBUILD_AFLAGS += -Wa,-gdwarf-2 endif diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile index bc74afdbf31e..dcfbd2a87d41 100644 --- a/arch/riscv/Makefile +++ b/arch/riscv/Makefile @@ -41,7 +41,7 @@ endif ifeq ($(CONFIG_LD_IS_LLD),y) KBUILD_CFLAGS += -mno-relax KBUILD_AFLAGS += -mno-relax -ifneq ($(LLVM_IAS),1) +ifndef CONFIG_AS_IS_LLVM KBUILD_CFLAGS += -Wa,-mno-relax KBUILD_AFLAGS += -Wa,-mno-relax endif -- cgit v1.2.3-70-g09d2 From 7d73c3e9c51400d3e0e755488050804e4d44737a Mon Sep 17 00:00:00 2001 From: Nick Desaulniers Date: Mon, 16 Aug 2021 13:25:01 -0700 Subject: Makefile: remove stale cc-option checks cc-option, cc-option-yn, and cc-disable-warning all invoke the compiler during build time, and can slow down the build when these checks become stale for our supported compilers, whose minimally supported versions increases over time. See Documentation/process/changes.rst for the current supported minimal versions (GCC 4.9+, clang 10.0.1+). Compiler version support for these flags may be verified on godbolt.org. The following flags are GCC only and supported since at least GCC 4.9. Remove cc-option and cc-disable-warning tests. * -fno-tree-loop-im * -Wno-maybe-uninitialized * -fno-reorder-blocks * -fno-ipa-cp-clone * -fno-partial-inlining * -femit-struct-debug-baseonly * -fno-inline-functions-called-once * -fconserve-stack The following flags are supported by all supported versions of GCC and Clang. Remove their cc-option, cc-option-yn, and cc-disable-warning tests. * -fno-delete-null-pointer-checks * -fno-var-tracking * -Wno-array-bounds The following configs are made dependent on GCC, since they use GCC specific flags. * READABLE_ASM * DEBUG_SECTION_MISMATCH -mfentry was not supported by s390-linux-gnu-gcc until gcc-9+, add a comment. --param=allow-store-data-races=0 was renamed to -fno-allow-store-data-races in the GCC 10 release; add a comment. -Wmaybe-uninitialized (GCC specific) was being added for CONFIG_GCOV, then again unconditionally; add it only once. Also, base RETPOLINE_CFLAGS and RETPOLINE_VDSO_CFLAGS on CONFIC_CC_IS_* then remove cc-option tests for Clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1436 Acked-by: Miguel Ojeda Reviewed-by: Nathan Chancellor Signed-off-by: Nick Desaulniers Signed-off-by: Masahiro Yamada --- Makefile | 50 +++++++++++++++++++++++++++++++------------------- lib/Kconfig.debug | 2 ++ 2 files changed, 33 insertions(+), 19 deletions(-) (limited to 'Makefile') diff --git a/Makefile b/Makefile index 891866af0787..ce5a297ecd7c 100644 --- a/Makefile +++ b/Makefile @@ -669,9 +669,10 @@ endif # KBUILD_EXTMOD # Defaults to vmlinux, but the arch makefile usually adds further targets all: vmlinux -CFLAGS_GCOV := -fprofile-arcs -ftest-coverage \ - $(call cc-option,-fno-tree-loop-im) \ - $(call cc-disable-warning,maybe-uninitialized,) +CFLAGS_GCOV := -fprofile-arcs -ftest-coverage +ifdef CONFIG_CC_IS_GCC +CFLAGS_GCOV += -fno-tree-loop-im +endif export CFLAGS_GCOV # The arch Makefiles can override CC_FLAGS_FTRACE. We may also append it later. @@ -679,12 +680,14 @@ ifdef CONFIG_FUNCTION_TRACER CC_FLAGS_FTRACE := -pg endif -RETPOLINE_CFLAGS_GCC := -mindirect-branch=thunk-extern -mindirect-branch-register -RETPOLINE_VDSO_CFLAGS_GCC := -mindirect-branch=thunk-inline -mindirect-branch-register -RETPOLINE_CFLAGS_CLANG := -mretpoline-external-thunk -RETPOLINE_VDSO_CFLAGS_CLANG := -mretpoline -RETPOLINE_CFLAGS := $(call cc-option,$(RETPOLINE_CFLAGS_GCC),$(call cc-option,$(RETPOLINE_CFLAGS_CLANG))) -RETPOLINE_VDSO_CFLAGS := $(call cc-option,$(RETPOLINE_VDSO_CFLAGS_GCC),$(call cc-option,$(RETPOLINE_VDSO_CFLAGS_CLANG))) +ifdef CONFIG_CC_IS_GCC +RETPOLINE_CFLAGS := $(call cc-option,-mindirect-branch=thunk-extern -mindirect-branch-register) +RETPOLINE_VDSO_CFLAGS := $(call cc-option,-mindirect-branch=thunk-inline -mindirect-branch-register) +endif +ifdef CONFIG_CC_IS_CLANG +RETPOLINE_CFLAGS := -mretpoline-external-thunk +RETPOLINE_VDSO_CFLAGS := -mretpoline +endif export RETPOLINE_CFLAGS export RETPOLINE_VDSO_CFLAGS @@ -737,7 +740,7 @@ include/config/auto.conf: endif # may-sync-config endif # need-config -KBUILD_CFLAGS += $(call cc-option,-fno-delete-null-pointer-checks,) +KBUILD_CFLAGS += -fno-delete-null-pointer-checks KBUILD_CFLAGS += $(call cc-disable-warning,frame-address,) KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation) KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow) @@ -752,17 +755,19 @@ KBUILD_CFLAGS += -Os endif # Tell gcc to never replace conditional load with a non-conditional one +ifdef CONFIG_CC_IS_GCC +# gcc-10 renamed --param=allow-store-data-races=0 to +# -fno-allow-store-data-races. KBUILD_CFLAGS += $(call cc-option,--param=allow-store-data-races=0) KBUILD_CFLAGS += $(call cc-option,-fno-allow-store-data-races) +endif ifdef CONFIG_READABLE_ASM # Disable optimizations that make assembler listings hard to read. # reorder blocks reorders the control in the function # ipa clone creates specialized cloned functions # partial inlining inlines only parts of functions -KBUILD_CFLAGS += $(call cc-option,-fno-reorder-blocks,) \ - $(call cc-option,-fno-ipa-cp-clone,) \ - $(call cc-option,-fno-partial-inlining) +KBUILD_CFLAGS += -fno-reorder-blocks -fno-ipa-cp-clone -fno-partial-inlining endif ifneq ($(CONFIG_FRAME_WARN),0) @@ -854,8 +859,10 @@ DEBUG_CFLAGS += -gdwarf-$(dwarf-version-y) endif ifdef CONFIG_DEBUG_INFO_REDUCED -DEBUG_CFLAGS += $(call cc-option, -femit-struct-debug-baseonly) \ - $(call cc-option,-fno-var-tracking) +DEBUG_CFLAGS += -fno-var-tracking +ifdef CONFIG_CC_IS_GCC +DEBUG_CFLAGS += -femit-struct-debug-baseonly +endif endif ifdef CONFIG_DEBUG_INFO_COMPRESSED @@ -889,6 +896,7 @@ ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT endif endif ifdef CONFIG_HAVE_FENTRY + # s390-linux-gnu-gcc did not support -mfentry until gcc-9. ifeq ($(call cc-option-yn, -mfentry),y) CC_FLAGS_FTRACE += -mfentry CC_FLAGS_USING += -DCC_USING_FENTRY @@ -901,7 +909,7 @@ endif # We trigger additional mismatches with less inlining ifdef CONFIG_DEBUG_SECTION_MISMATCH -KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once) +KBUILD_CFLAGS += -fno-inline-functions-called-once endif ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION @@ -980,14 +988,16 @@ KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation) # We'll want to enable this eventually, but it's not going away for 5.7 at least KBUILD_CFLAGS += $(call cc-disable-warning, zero-length-bounds) -KBUILD_CFLAGS += $(call cc-disable-warning, array-bounds) +KBUILD_CFLAGS += -Wno-array-bounds KBUILD_CFLAGS += $(call cc-disable-warning, stringop-overflow) # Another good warning that we'll want to enable eventually KBUILD_CFLAGS += $(call cc-disable-warning, restrict) # Enabled with W=2, disabled by default as noisy -KBUILD_CFLAGS += $(call cc-disable-warning, maybe-uninitialized) +ifdef CONFIG_CC_IS_GCC +KBUILD_CFLAGS += -Wno-maybe-uninitialized +endif # disable invalid "can't wrap" optimizations for signed / pointers KBUILD_CFLAGS += -fno-strict-overflow @@ -996,7 +1006,9 @@ KBUILD_CFLAGS += -fno-strict-overflow KBUILD_CFLAGS += -fno-stack-check # conserve stack if available -KBUILD_CFLAGS += $(call cc-option,-fconserve-stack) +ifdef CONFIG_CC_IS_GCC +KBUILD_CFLAGS += -fconserve-stack +endif # Prohibit date/time macros, which would make the build non-deterministic KBUILD_CFLAGS += -Werror=date-time diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 5ddd575159fb..7d3d29203a72 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -365,6 +365,7 @@ config STRIP_ASM_SYMS config READABLE_ASM bool "Generate readable assembler code" depends on DEBUG_KERNEL + depends on CC_IS_GCC help Disable some compiler optimizations that tend to generate human unreadable assembler output. This may make the kernel slightly slower, but it helps @@ -383,6 +384,7 @@ config HEADERS_INSTALL config DEBUG_SECTION_MISMATCH bool "Enable full Section mismatch analysis" + depends on CC_IS_GCC help The section mismatch analysis checks if there are illegal references from one section to another section. -- cgit v1.2.3-70-g09d2 From a312b60d6c4f09cebb727ffab68754fbf39dc1f1 Mon Sep 17 00:00:00 2001 From: Nathan Chancellor Date: Mon, 16 Aug 2021 13:20:54 -0700 Subject: kbuild: Remove -Wno-format-invalid-specifier from clang block Turning on -Wformat does not reveal any instances of this warning across several different builds so remove this line to keep the number of disabled warnings as slim as possible. This has been disabled since commit 61163efae020 ("kbuild: LLVMLinux: Add Kbuild support for building kernel with Clang"), which does not explain exactly why it was turned off but since it was so long ago in terms of both the kernel and LLVM so it is possible that some bug got fixed along the way. Signed-off-by: Nathan Chancellor Reviewed-by: Nick Desaulniers Signed-off-by: Masahiro Yamada --- Makefile | 1 - 1 file changed, 1 deletion(-) (limited to 'Makefile') diff --git a/Makefile b/Makefile index ce5a297ecd7c..add32a749860 100644 --- a/Makefile +++ b/Makefile @@ -782,7 +782,6 @@ KBUILD_CFLAGS += $(stackp-flags-y) ifdef CONFIG_CC_IS_CLANG KBUILD_CPPFLAGS += -Qunused-arguments -KBUILD_CFLAGS += -Wno-format-invalid-specifier KBUILD_CFLAGS += -Wno-gnu # CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the # source of a reference will be _MergedGlobals and not on of the whitelisted names. -- cgit v1.2.3-70-g09d2 From 5c6ae0efca8d7aeac02f8734825067cd9475a264 Mon Sep 17 00:00:00 2001 From: Nathan Chancellor Date: Mon, 16 Aug 2021 13:20:55 -0700 Subject: kbuild: Add a comment above -Wno-gnu Whenever a warning is disabled, it is helpful for future travelers to understand why the warning is disabled and why it is acceptable to do so. Add a comment for -Wno-gnu so that people understand why it is disabled. Signed-off-by: Nathan Chancellor Signed-off-by: Masahiro Yamada --- Makefile | 1 + 1 file changed, 1 insertion(+) (limited to 'Makefile') diff --git a/Makefile b/Makefile index add32a749860..8dc6707542a8 100644 --- a/Makefile +++ b/Makefile @@ -782,6 +782,7 @@ KBUILD_CFLAGS += $(stackp-flags-y) ifdef CONFIG_CC_IS_CLANG KBUILD_CPPFLAGS += -Qunused-arguments +# The kernel builds with '-std=gnu89' so use of GNU extensions is acceptable. KBUILD_CFLAGS += -Wno-gnu # CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the # source of a reference will be _MergedGlobals and not on of the whitelisted names. -- cgit v1.2.3-70-g09d2 From 6272cc389fec78d1c0685599b8cad974476d89bb Mon Sep 17 00:00:00 2001 From: Nathan Chancellor Date: Mon, 16 Aug 2021 13:20:56 -0700 Subject: kbuild: Shuffle blank line to improve comment meaning -Wunused-but-set-variable and -Wunused-const-variable are both disabled for the same reason but there is a blank line between them and no blank line between -Wno-unused-const-variable and the block. Shuffle the new line so that it is clear that the comment applied to both flags and the next block is separate from them. Signed-off-by: Nathan Chancellor Signed-off-by: Masahiro Yamada --- Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'Makefile') diff --git a/Makefile b/Makefile index 8dc6707542a8..d1702ade1970 100644 --- a/Makefile +++ b/Makefile @@ -799,8 +799,8 @@ endif # These warnings generated too much noise in a regular build. # Use make W=1 to enable them (see scripts/Makefile.extrawarn) KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) - KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable) + ifdef CONFIG_FRAME_POINTER KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls else -- cgit v1.2.3-70-g09d2