linux-kernel - [PATCH v9 1/4] kbuild: add mod(name,file)_flags to assembler flags for module objects

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Message-ID: <20240824033757.52005-2-kris.van.hees@oracle.com>
Date: Fri, 23 Aug 2024 23:37:54 -0400
From: Kris Van Hees <kris.van.hees@...cle.com>
To: linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        linux-modules@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Cc: Kris Van Hees <kris.van.hees@...cle.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Jiri Olsa <olsajiri@...il.com>,
        Elena Zannoni <elena.zannoni@...cle.com>
Subject: [PATCH v9 1/4] kbuild: add mod(name,file)_flags to assembler flags for module objects

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_cflags), 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 source files.  While KBUILD_MODFILE is sufficient to generate
the modules ranges data, KBUILD_MODNAME is passed as well for consistency
with the C source code case.

Signed-off-by: Kris Van Hees <kris.van.hees@...cle.com>
Reviewed-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
    Changes since v8:
     - Fixed typos.
     - Explained KBUILD_MODNAME being added for consistency.
---
 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