linux-kernel - [PATCH 2/5] kbuild: define KBUILD_MODNAME even if multiple modules share objects

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Date:   Thu,  8 Mar 2018 10:05:00 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     linux-kbuild@...r.kernel.org
Cc:     Sam Ravnborg <sam@...nborg.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Cao jin <caoj.fnst@...fujitsu.com>,
        Govind Singh <govinds@...eaurora.org>,
        Kalle Valo <kvalo@...eaurora.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/5] kbuild: define KBUILD_MODNAME even if multiple modules share objects

Currently, KBUILD_MODNAME is defined only when $(modname) contains
just one word.  If an object is shared among multiple modules,
undefined KBUILD_MODNAME could cause a build error.  For example,
if CONFIG_DYNAMIC_DEBUG is enabled, any call of printk() populates
.modname, then fails to build due to undefined KBUILD_MODNAME.

Take the following code as an example:

  obj-m += foo.o
  obj-m += bar.o
  foo-objs := foo-bar-common.o foo-main.o
  bar-objs := foo-bar-common.o bar-main.o

In this case, there is room for argument what to define for
KBUILD_MODNAME when foo-bar-common.o is being compiled.
"foo", "bar", or what else?

One idea is to define colon-separated modules that share the object,
in this case, "bar:foo" (modules are sorted alphabetically by
$(sort ...).

Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
---

 scripts/Makefile.lib | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index a7e315f..a1fbd6a 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -92,8 +92,7 @@ subdir-ym	:= $(addprefix $(obj)/,$(subdir-ym))
 #       differ in different configs.
 name-fix = $(squote)$(quote)$(subst $(comma),_,$(subst -,_,$1))$(quote)$(squote)
 basename_flags = -DKBUILD_BASENAME=$(call name-fix,$(basetarget))
-modname_flags  = $(if $(filter 1,$(words $(modname))),\
-                 -DKBUILD_MODNAME=$(call name-fix,$(modname)))
+modname_flags  = -DKBUILD_MODNAME=$(call name-fix,$(modname))
 
 orig_c_flags   = $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) \
                  $(ccflags-y) $(CFLAGS_$(basetarget).o)
@@ -174,8 +173,10 @@ dtc_cpp_flags  = -Wp,-MD,$(depfile).pre.tmp -nostdinc                    \
 		 -undef -D__DTS__
 
 # Finds the multi-part object the current object will be linked into
-modname-multi = $(sort $(foreach m,$(multi-used),\
-		$(if $(filter $*.o, $($(m:.o=-objs)) $($(m:.o=-y))),$(m:.o=))))
+# If the object belongs to two or more multi-part objects, all of them are
+# concatenated with a colon separator.
+modname-multi = $(subst $(space),:,$(sort $(foreach m,$(multi-used),\
+		$(if $(filter $*.o, $($(m:.o=-objs)) $($(m:.o=-y))),$(m:.o=)))))
 
 # Useful for describing the dependency of composite objects
 # Usage:
-- 
2.7.4