linux-kernel - Re: [PATCH v5 1/4] kbuild: add mod(name,file)_flags to assembler flags for module objects

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Message-ID: <Zr0Im8k6KSqfZLyp@oracle.com>
Date: Wed, 14 Aug 2024 15:42:19 -0400
From: Kris Van Hees <kris.van.hees@...cle.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Kris Van Hees <kris.van.hees@...cle.com>, linux-kernel@...r.kernel.org,
        linux-kbuild@...r.kernel.org, linux-modules@...r.kernel.org,
        linux-trace-kernel@...r.kernel.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: Re: [PATCH v5 1/4] kbuild: add mod(name,file)_flags to assembler
 flags for module objects

On Wed, Aug 14, 2024 at 01:17:46PM -0400, Steven Rostedt wrote:
> On Mon, 15 Jul 2024 23:10:42 -0400
> Kris Van Hees <kris.van.hees@...cle.com> wrote:
> 
> 
> As mentioned before, should start off with the goal.
> 
>   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, ...

Ok, I see what you mean.  Fixing that.  Thanks!

 > In order to be able to identify what code is compiled into modules (even
> > built-in 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.
> 
> The rest looks good.
> 
> Reviewed-by: Steven Rostedt (Google) <rostedt@...dmis.org>

Thanks!

> 
> -- Steve
> 
> > 
> > Signed-off-by: Kris Van Hees <kris.van.hees@...cle.com>
> > ---
> >  scripts/Makefile.lib | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> > index 9f06f6aaf7fc..f4aec3553ff2 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)