On Tue, 7 Jul 2020 at 11:21, Masahiro Yamada <masahi...@kernel.org> wrote:
>
> CFLAGS_REMOVE_<file>.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_<file> adds compiler flags per file.
>
> [5] CFLAGS_REMOVE_<file> 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
>
> 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.
>
> arch/arm/boot/compressed/
> arch/powerpc/xmon/
> arch/sh/
> kernel/trace/
>
> ... have no sub-directories.
>
> lib/
>
> ... has several sub-directories.
>
> To keep the behavior, I added ccflags-remove-y to all Makefiles
> in subdirectories of lib/, except:
>
> 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 later commit, I will try to remove ccflags-remove-y
> from sub-directory Makefiles.
>
> Suggested-by: Sami Tolvanen <samitolva...@google.com>
> Signed-off-by: Masahiro Yamada <masahi...@kernel.org>
> Acked-by: Steven Rostedt (VMware) <rost...@goodmis.org>
> Acked-by: Michael Ellerman <m...@ellerman.id.au> (powerpc)
Tested-by: Anders Roxell <anders.rox...@linaro.org>
> ---
>
> Changes in v2:
> - Swap the order of [3] and [4] to keep the current behavior of
> kernel/trace/Makefile.
> - Add ccflags-remove-y to subdir Makefiles of lib/
>
> Documentation/kbuild/makefiles.rst | 14 ++++++++++++++
> arch/arm/boot/compressed/Makefile | 6 +-----
> arch/powerpc/xmon/Makefile | 3 +--
> arch/sh/boot/compressed/Makefile | 5 +----
> kernel/trace/Makefile | 4 ++--
> lib/842/Makefile | 3 +++
> lib/Makefile | 5 +----
> lib/crypto/Makefile | 2 ++
> lib/dim/Makefile | 2 ++
> lib/fonts/Makefile | 2 ++
> lib/kunit/Makefile | 3 +++
> lib/livepatch/Makefile | 2 ++
> lib/lz4/Makefile | 1 +
> lib/lzo/Makefile | 2 ++
> lib/math/Makefile | 2 ++
> lib/mpi/Makefile | 2 ++
> lib/raid6/Makefile | 3 +++
> lib/reed_solomon/Makefile | 2 ++
> lib/xz/Makefile | 3 +++
> lib/zlib_deflate/Makefile | 2 ++
> lib/zlib_dfltcc/Makefile | 2 ++
> lib/zlib_inflate/Makefile | 2 ++
> lib/zstd/Makefile | 1 +
> scripts/Makefile.lib | 14 ++++++++------
> 24 files changed, 64 insertions(+), 23 deletions(-)
>
> diff --git a/Documentation/kbuild/makefiles.rst
> b/Documentation/kbuild/makefiles.rst
> index 6515ebc12b6f..14d8e7d23c04 100644
> --- a/Documentation/kbuild/makefiles.rst
> +++ b/Documentation/kbuild/makefiles.rst
> @@ -368,6 +368,14 @@ more details, with real examples.
>
> subdir-ccflags-y := -Werror
>
> + ccflags-remove-y, asflags-remove-y
> + These flags are used to remove particular flags for the compiler,
> + assembler invocations.
> +
> + Example::
> +
> + ccflags-remove-$(CONFIG_MCOUNT) += -pg
> +
> CFLAGS_$@, AFLAGS_$@
> CFLAGS_$@ and AFLAGS_$@ only apply to commands in current
> kbuild makefile.
> @@ -375,6 +383,9 @@ more details, with real examples.
> $(CFLAGS_$@) specifies per-file options for $(CC). The $@
> part has a literal value which specifies the file that it is for.
>
> + CFLAGS_$@ has the higher priority than ccflags-remove-y; CFLAGS_$@
> + can re-add compiler flags that were removed by ccflags-remove-y.
> +
> Example::
>
> # drivers/scsi/Makefile
> @@ -387,6 +398,9 @@ more details, with real examples.
> $(AFLAGS_$@) is a similar feature for source files in assembly
> languages.
>
> + AFLAGS_$@ has the higher priority than asflags-remove-y; AFLAGS_$@
> + can re-add assembler flags that were removed by asflags-remove-y.
> +
> Example::
>
> # arch/arm/kernel/Makefile
> diff --git a/arch/arm/boot/compressed/Makefile
> b/arch/arm/boot/compressed/Makefile
> index 00602a6fba04..3d5691b23951 100644
> --- a/arch/arm/boot/compressed/Makefile
> +++ b/arch/arm/boot/compressed/Makefile
> @@ -103,13 +103,9 @@ 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.
> diff --git a/arch/powerpc/xmon/Makefile b/arch/powerpc/xmon/Makefile
> index 89c76ca35640..eb25d7554ffd 100644
> --- a/arch/powerpc/xmon/Makefile
> +++ b/arch/powerpc/xmon/Makefile
> @@ -7,8 +7,7 @@ UBSAN_SANITIZE := n
> KASAN_SANITIZE := n
>
> # Disable ftrace for the entire directory
> -ORIG_CFLAGS := $(KBUILD_CFLAGS)
> -KBUILD_CFLAGS = $(subst $(CC_FLAGS_FTRACE),,$(ORIG_CFLAGS))
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
>
> ifdef CONFIG_CC_IS_CLANG
> # clang stores addresses on the stack causing the frame size to blow
> diff --git a/arch/sh/boot/compressed/Makefile
> b/arch/sh/boot/compressed/Makefile
> index ad0e2403e56f..589d2d8a573d 100644
> --- a/arch/sh/boot/compressed/Makefile
> +++ b/arch/sh/boot/compressed/Makefile
> @@ -28,10 +28,7 @@ IMAGE_OFFSET := $(shell /bin/bash -c 'printf "0x%08x" \
> $(CONFIG_BOOT_LINK_OFFSET)]')
> endif
>
> -ifeq ($(CONFIG_MCOUNT),y)
> -ORIG_CFLAGS := $(KBUILD_CFLAGS)
> -KBUILD_CFLAGS = $(subst -pg, , $(ORIG_CFLAGS))
> -endif
> +ccflags-remove-$(CONFIG_MCOUNT) += -pg
>
> LDFLAGS_vmlinux := --oformat $(ld-bfd) -Ttext $(IMAGE_OFFSET) -e startup \
> -T $(obj)/../../kernel/vmlinux.lds
> diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
> index 6575bb0a0434..7492844a8b1b 100644
> --- a/kernel/trace/Makefile
> +++ b/kernel/trace/Makefile
> @@ -2,9 +2,9 @@
>
> # Do not instrument the tracer itself:
>
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> +
> ifdef CONFIG_FUNCTION_TRACER
> -ORIG_CFLAGS := $(KBUILD_CFLAGS)
> -KBUILD_CFLAGS = $(subst $(CC_FLAGS_FTRACE),,$(ORIG_CFLAGS))
>
> # Avoid recursion due to instrumentation.
> KCSAN_SANITIZE := n
> diff --git a/lib/842/Makefile b/lib/842/Makefile
> index 6f7aad269288..b815e824ae37 100644
> --- a/lib/842/Makefile
> +++ b/lib/842/Makefile
> @@ -1,3 +1,6 @@
> # SPDX-License-Identifier: GPL-2.0-only
> +
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> +
> obj-$(CONFIG_842_COMPRESS) += 842_compress.o
> obj-$(CONFIG_842_DECOMPRESS) += 842_decompress.o
> diff --git a/lib/Makefile b/lib/Makefile
> index b1c42c10073b..b2ed4beddd68 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -3,10 +3,7 @@
> # Makefile for some libs needed in the kernel.
> #
>
> -ifdef CONFIG_FUNCTION_TRACER
> -ORIG_CFLAGS := $(KBUILD_CFLAGS)
> -KBUILD_CFLAGS = $(subst $(CC_FLAGS_FTRACE),,$(ORIG_CFLAGS))
> -endif
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
>
> # These files are disabled because they produce lots of non-interesting
> and/or
> # flaky coverage that is not a function of syscall inputs. For example,
> diff --git a/lib/crypto/Makefile b/lib/crypto/Makefile
> index 3a435629d9ce..b557ef0b07c2 100644
> --- a/lib/crypto/Makefile
> +++ b/lib/crypto/Makefile
> @@ -1,5 +1,7 @@
> # SPDX-License-Identifier: GPL-2.0
>
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> +
> # chacha is used by the /dev/random driver which is always builtin
> obj-y += chacha.o
> obj-$(CONFIG_CRYPTO_LIB_CHACHA_GENERIC) += libchacha.o
> diff --git a/lib/dim/Makefile b/lib/dim/Makefile
> index 1d6858a108cb..97fc3e89d34e 100644
> --- a/lib/dim/Makefile
> +++ b/lib/dim/Makefile
> @@ -2,6 +2,8 @@
> # DIM Dynamic Interrupt Moderation library
> #
>
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> +
> obj-$(CONFIG_DIMLIB) += dim.o
>
> dim-y := dim.o net_dim.o rdma_dim.o
> diff --git a/lib/fonts/Makefile b/lib/fonts/Makefile
> index ed95070860de..f951750c179e 100644
> --- a/lib/fonts/Makefile
> +++ b/lib/fonts/Makefile
> @@ -1,6 +1,8 @@
> # SPDX-License-Identifier: GPL-2.0
> # Font handling
>
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> +
> font-objs := fonts.o
>
> font-objs-$(CONFIG_FONT_SUN8x16) += font_sun8x16.o
> diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile
> index 724b94311ca3..8c847557ab24 100644
> --- a/lib/kunit/Makefile
> +++ b/lib/kunit/Makefile
> @@ -1,3 +1,6 @@
> +
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> +
> obj-$(CONFIG_KUNIT) += kunit.o
>
> kunit-objs += test.o \
> diff --git a/lib/livepatch/Makefile b/lib/livepatch/Makefile
> index 295b94bff370..9abdf615b088 100644
> --- a/lib/livepatch/Makefile
> +++ b/lib/livepatch/Makefile
> @@ -2,6 +2,8 @@
> #
> # Makefile for livepatch test code.
>
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> +
> obj-$(CONFIG_TEST_LIVEPATCH) += test_klp_atomic_replace.o \
> test_klp_callbacks_demo.o \
> test_klp_callbacks_demo2.o \
> diff --git a/lib/lz4/Makefile b/lib/lz4/Makefile
> index 5b42242afaa2..53da4cab7015 100644
> --- a/lib/lz4/Makefile
> +++ b/lib/lz4/Makefile
> @@ -1,5 +1,6 @@
> # SPDX-License-Identifier: GPL-2.0-only
> ccflags-y += -O3
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
>
> obj-$(CONFIG_LZ4_COMPRESS) += lz4_compress.o
> obj-$(CONFIG_LZ4HC_COMPRESS) += lz4hc_compress.o
> diff --git a/lib/lzo/Makefile b/lib/lzo/Makefile
> index 2f58fafbbddd..9565a555275b 100644
> --- a/lib/lzo/Makefile
> +++ b/lib/lzo/Makefile
> @@ -1,4 +1,6 @@
> # SPDX-License-Identifier: GPL-2.0-only
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> +
> lzo_compress-objs := lzo1x_compress.o
> lzo_decompress-objs := lzo1x_decompress_safe.o
>
> diff --git a/lib/math/Makefile b/lib/math/Makefile
> index be6909e943bd..49aa50e28185 100644
> --- a/lib/math/Makefile
> +++ b/lib/math/Makefile
> @@ -1,4 +1,6 @@
> # SPDX-License-Identifier: GPL-2.0-only
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> +
> obj-y += div64.o gcd.o lcm.o int_pow.o int_sqrt.o reciprocal_div.o
>
> obj-$(CONFIG_CORDIC) += cordic.o
> diff --git a/lib/mpi/Makefile b/lib/mpi/Makefile
> index d5874a7f5ff9..df7883521619 100644
> --- a/lib/mpi/Makefile
> +++ b/lib/mpi/Makefile
> @@ -3,6 +3,8 @@
> # MPI multiprecision maths library (from gpg)
> #
>
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> +
> obj-$(CONFIG_MPILIB) = mpi.o
>
> mpi-y = \
> diff --git a/lib/raid6/Makefile b/lib/raid6/Makefile
> index b4c0df6d706d..3482d6ae3f3b 100644
> --- a/lib/raid6/Makefile
> +++ b/lib/raid6/Makefile
> @@ -1,4 +1,7 @@
> # SPDX-License-Identifier: GPL-2.0
> +
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> +
> obj-$(CONFIG_RAID6_PQ) += raid6_pq.o
>
> raid6_pq-y += algos.o recov.o tables.o int1.o int2.o int4.o \
> diff --git a/lib/reed_solomon/Makefile b/lib/reed_solomon/Makefile
> index 5d4fa68f26cb..a5c9defdac7f 100644
> --- a/lib/reed_solomon/Makefile
> +++ b/lib/reed_solomon/Makefile
> @@ -3,5 +3,7 @@
> # This is a modified version of reed solomon lib,
> #
>
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> +
> obj-$(CONFIG_REED_SOLOMON) += reed_solomon.o
> obj-$(CONFIG_REED_SOLOMON_TEST) += test_rslib.o
> diff --git a/lib/xz/Makefile b/lib/xz/Makefile
> index fa6af814a8d1..fae9b6c7c389 100644
> --- a/lib/xz/Makefile
> +++ b/lib/xz/Makefile
> @@ -1,4 +1,7 @@
> # SPDX-License-Identifier: GPL-2.0-only
> +
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> +
> obj-$(CONFIG_XZ_DEC) += xz_dec.o
> xz_dec-y := xz_dec_syms.o xz_dec_stream.o xz_dec_lzma2.o
> xz_dec-$(CONFIG_XZ_DEC_BCJ) += xz_dec_bcj.o
> diff --git a/lib/zlib_deflate/Makefile b/lib/zlib_deflate/Makefile
> index 2622e03c0b94..1fcefe73536f 100644
> --- a/lib/zlib_deflate/Makefile
> +++ b/lib/zlib_deflate/Makefile
> @@ -7,6 +7,8 @@
> # decompression code.
> #
>
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> +
> obj-$(CONFIG_ZLIB_DEFLATE) += zlib_deflate.o
>
> zlib_deflate-objs := deflate.o deftree.o deflate_syms.o
> diff --git a/lib/zlib_dfltcc/Makefile b/lib/zlib_dfltcc/Makefile
> index 8e4d5afbbb10..7a8067f6e772 100644
> --- a/lib/zlib_dfltcc/Makefile
> +++ b/lib/zlib_dfltcc/Makefile
> @@ -6,6 +6,8 @@
> # This is the code for s390 zlib hardware support.
> #
>
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> +
> obj-$(CONFIG_ZLIB_DFLTCC) += zlib_dfltcc.o
>
> zlib_dfltcc-objs := dfltcc.o dfltcc_deflate.o dfltcc_inflate.o dfltcc_syms.o
> diff --git a/lib/zlib_inflate/Makefile b/lib/zlib_inflate/Makefile
> index 27327d3e9f54..a451e96f9845 100644
> --- a/lib/zlib_inflate/Makefile
> +++ b/lib/zlib_inflate/Makefile
> @@ -14,6 +14,8 @@
> # uncompression can be done without blocking on allocation).
> #
>
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> +
> obj-$(CONFIG_ZLIB_INFLATE) += zlib_inflate.o
>
> zlib_inflate-objs := inffast.o inflate.o infutil.o \
> diff --git a/lib/zstd/Makefile b/lib/zstd/Makefile
> index f5d778e7e5c7..01be908a2d94 100644
> --- a/lib/zstd/Makefile
> +++ b/lib/zstd/Makefile
> @@ -3,6 +3,7 @@ obj-$(CONFIG_ZSTD_COMPRESS) += zstd_compress.o
> obj-$(CONFIG_ZSTD_DECOMPRESS) += zstd_decompress.o
>
> ccflags-y += -O3
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
>
> zstd_compress-y := fse_compress.o huf_compress.o compress.o \
> entropy_common.o fse_decompress.o zstd_common.o
> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index 916b2f7f7098..3629f66646d7 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -111,12 +111,14 @@ basename_flags = -DKBUILD_BASENAME=$(call
> name-fix,$(basetarget))
> modname_flags = -DKBUILD_MODNAME=$(call name-fix,$(modname))
> modfile_flags = -DKBUILD_MODFILE=$(call stringify,$(modfile))
>
> -orig_c_flags = $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) \
> - $(ccflags-y) $(CFLAGS_$(target-stem).o)
> -_c_flags = $(filter-out $(CFLAGS_REMOVE_$(target-stem).o),
> $(orig_c_flags))
> -orig_a_flags = $(KBUILD_CPPFLAGS) $(KBUILD_AFLAGS) \
> - $(asflags-y) $(AFLAGS_$(target-stem).o)
> -_a_flags = $(filter-out $(AFLAGS_REMOVE_$(target-stem).o),
> $(orig_a_flags))
> +_c_flags = $(filter-out $(CFLAGS_REMOVE_$(target-stem).o), \
> + $(filter-out $(ccflags-remove-y), \
> + $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(ccflags-y)) \
> + $(CFLAGS_$(target-stem).o))
> +_a_flags = $(filter-out $(AFLAGS_REMOVE_$(target-stem).o), \
> + $(filter-out $(asflags-remove-y), \
> + $(KBUILD_CPPFLAGS) $(KBUILD_AFLAGS) $(asflags-y)) \
> + $(AFLAGS_$(target-stem).o))
> _cpp_flags = $(KBUILD_CPPFLAGS) $(cppflags-y)
> $(CPPFLAGS_$(target-stem).lds)
>
> #
> --
> 2.25.1
>
