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[PATCH v8 1/4] kbuild: add mod(name,file)_flags to assembler flags for module objects

From: Kris Van Hees <hidden>
Date: 2024-08-22 18:21:02
Also in: linux-kbuild, linux-modules, lkml
Subsystem: kernel build + files below scripts/ (unless maintained elsewhere), the rest · Maintainers: Nathan Chancellor, Nicolas Schier, Linus Torvalds

In order to create the file at build time, modules.builtin.ranges, that
contains the range of addresses for all built-in modules, there needs to
be a way to identify what code is compiled into modules.

To identify what code is compiled into modules during a kernel build,
one can look for the presence of the -DKBUILD_MODFILE and -DKBUILD_MODNAME
options in the compile command lines.  A simple grep in .*.cmd files for
those options is sufficient for this.

Unfortunately, these options are only passed when compiling C source files.
Various modules also include objects built from assembler source, and these
options are not passed in that case.

Adding $(modfile_flags) to modkern_aflags (similar to modkern_cflahs), and
adding $(modname_flags) to a_flags (similar to c_flags) makes it possible
to identify which objects are compiled into modules for both C and
assembler soure files.

Signed-off-by: Kris Van Hees <redacted>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 scripts/Makefile.lib | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index fe3668dc4954..170f462537a8 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -238,7 +238,7 @@ modkern_rustflags =                                              \
 
 modkern_aflags = $(if $(part-of-module),				\
 			$(KBUILD_AFLAGS_MODULE) $(AFLAGS_MODULE),	\
-			$(KBUILD_AFLAGS_KERNEL) $(AFLAGS_KERNEL))
+			$(KBUILD_AFLAGS_KERNEL) $(AFLAGS_KERNEL) $(modfile_flags))
 
 c_flags        = -Wp,-MMD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \
 		 -include $(srctree)/include/linux/compiler_types.h       \
@@ -248,7 +248,7 @@ c_flags        = -Wp,-MMD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \
 rust_flags     = $(_rust_flags) $(modkern_rustflags) @$(objtree)/include/generated/rustc_cfg
 
 a_flags        = -Wp,-MMD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \
-		 $(_a_flags) $(modkern_aflags)
+		 $(_a_flags) $(modkern_aflags) $(modname_flags)
 
 cpp_flags      = -Wp,-MMD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \
 		 $(_cpp_flags)
-- 
2.45.2
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