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 $(CC_FLAGS_FTRACE)
from all objects in the directory, then adds it back to
trace_selftest_dynamic.o and CFLAGS_trace_kprobe_selftest.o
The same applies to lib/livepatch/Makefile.
Please note ccflags-remove-y has no effect to the sub-directories.
In contrast, the previous notation got rid of compiler flags also from
all the sub-directories.
The following are not affected because they have no sub-directories:
arch/arm/boot/compressed/
arch/powerpc/xmon/
arch/sh/
kernel/trace/
However, lib/ has several sub-directories.
To keep the behavior, I added ccflags-remove-y to all Makefiles
in subdirectories of lib/, except the following:
lib/vdso/Makefile - Kbuild does not descend into this Makefile
lib/raid/test/Makefile - This is not used for the kernel build
I think commit 2464a609ded0 ("ftrace: do not trace library functions")
excluded too much. In the next commit, I will remove ccflags-remove-y
from the sub-directories of lib/.
Suggested-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Acked-by: Brendan Higgins <brendanhiggins@google.com> (KUnit)
Tested-by: Anders Roxell <anders.roxell@linaro.org>
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 8fa9aa2..5cfd377 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -111,12 +111,14 @@
modname_flags = -DKBUILD_MODNAME=$(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)
#