kbuild: introduce ccflags-remove-y and asflags-remove-y

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

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 <samitolvanen@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Acked-by: Brendan Higgins <brendanhiggins@google.com> (KUnit)
Tested-by: Anders Roxell <anders.roxell@linaro.org>

18 files changed, 37 insertions, 4 deletions

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 0cda70649f1c..233f6e644eeb 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