linux-kernel - [PATCH 5/7] kbuild: get rid of duplication in *.mod files

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Date:   Thu,  7 Apr 2022 00:30:21 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     linux-kbuild@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: [PATCH 5/7] kbuild: get rid of duplication in *.mod files

It is allowed to add the same objects multiple times to obj-y / obj-m:

  obj-y += foo.o foo.o foo.o
  obj-m += bar.o bar.o bar.o

It is also allowed to add the same objects multiple times to a composite
module:

  obj-m    += foo.o
  foo-objs := foo1.o foo2.o foo2.o foo1.o

This flexibility is useful because the same object might be selected by
different CONFIG options, like this:

  obj-m               += foo.o
  foo-y               := foo1.o
  foo-$(CONFIG_FOO_X) += foo2.o
  foo-$(CONFIG_FOO_Y) += foo2.o

The duplicated objects are omitted at link time. It works naturally in
Makefiles because GNU Make removes duplication in $^ without changing
the order.

It is working well, almost...

A small flaw I notice is, *.mod contains duplication in such a case.

This is probably not a big deal. As far as I know, the only small
problem is scripts/mod/sumversion.c parses the same file multiple
times.

I am fixing this because I plan to reuse *.mod for other purposes,
where the duplication can be problematic.

The code change is quite simple. We already use awk to drop duplicated
lines in modules.order (see cmd_modules_order in the same file).
I copied the code, but changed RS to use spaces as record separators.

I also changed the file format to list one object per line.

Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---

 scripts/Makefile.build   | 3 ++-
 scripts/mod/sumversion.c | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 6ae92d119dfa..f7a30f378e20 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -303,7 +303,8 @@ $(obj)/%.prelink.o: $(obj)/%.o FORCE
 	$(call if_changed,cc_prelink_modules)
 endif

-cmd_mod = echo $(addprefix $(obj)/, $(call real-search, $*.o, .o, -objs -y -m)) > $@
+cmd_mod = echo $(addprefix $(obj)/, $(call real-search, $*.o, .o, -objs -y -m)) | \
+	$(AWK) -v RS='( |\n)' '!x[$$0]++' > $@

 $(obj)/%.mod: $(obj)/%$(mod-prelink-ext).o FORCE
 	$(call if_changed,mod)
diff --git a/scripts/mod/sumversion.c b/scripts/mod/sumversion.c
index 0125698f2037..79bb9eaa65ac 100644
--- a/scripts/mod/sumversion.c
+++ b/scripts/mod/sumversion.c
@@ -398,7 +398,7 @@ void get_src_version(const char *modname, char sum[], unsigned sumlen)
 	buf = read_text_file(filelist);

 	md4_init(&md);
-	while ((fname = strsep(&buf, " \n"))) {
+	while ((fname = strsep(&buf, "\n"))) {
 		if (!*fname)
 			continue;
 		if (!(is_static_library(fname)) &&
-- 
2.32.0