From 8b41fc4454e36fbfdbb23f940d023d4dece2de29 Mon Sep 17 00:00:00 2001
From: Masahiro Yamada <masahiroy@kernel.org>
Date: Thu, 19 Dec 2019 17:33:29 +0900
Subject: kbuild: create modules.builtin without Makefile.modbuiltin or
 tristate.conf

Commit bc081dd6e9f6 ("kbuild: generate modules.builtin") added
infrastructure to generate modules.builtin, the list of all
builtin modules.

Basically, it works like this:

  - Kconfig generates include/config/tristate.conf, the list of
    tristate CONFIG options with a value in a capital letter.

  - scripts/Makefile.modbuiltin makes Kbuild descend into
    directories to collect the information of builtin modules.

I am not a big fan of it because Kbuild ends up with traversing
the source tree twice.

I am not sure how perfectly it should work, but this approach cannot
avoid false positives; even if the relevant CONFIG option is tristate,
some Makefiles forces obj-m to obj-y.

Some examples are:

  arch/powerpc/platforms/powermac/Makefile:
    obj-$(CONFIG_NVRAM:m=y)         += nvram.o

  net/ipv6/Makefile:
    obj-$(subst m,y,$(CONFIG_IPV6)) += inet6_hashtables.o

  net/netlabel/Makefile:
    obj-$(subst m,y,$(CONFIG_IPV6)) += netlabel_calipso.o

Nobody has complained about (or noticed) it, so it is probably fine to
have false positives in modules.builtin.

This commit simplifies the implementation. Let's exploit the fact
that every module has MODULE_LICENSE(). (modpost shows a warning if
MODULE_LICENSE is missing. If so, 0-day bot would already have blocked
such a module.)

I added MODULE_FILE to <linux/module.h>. When the code is being compiled
as builtin, it will be filled with the file path of the module, and
collected into modules.builtin.info. Then, scripts/link-vmlinux.sh
extracts the list of builtin modules out of it.

This new approach fixes the false-positives above, but adds another
type of false-positives; non-modular code may have MODULE_LICENSE()
by mistake. This is not a big deal, it is just the code is always
orphan. We can clean it up if we like. You can see cleanup examples by:

  $ git log --grep='make.* explicitly non-modular'

To sum up, this commits deletes lots of code, but still produces almost
equivalent results. Please note it does not increase the vmlinux size at
all. As you can see in include/asm-generic/vmlinux.lds.h, the .modinfo
section is discarded in the link stage.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---
 scripts/Makefile.modbuiltin | 57 ---------------------------------------------
 1 file changed, 57 deletions(-)
 delete mode 100644 scripts/Makefile.modbuiltin

(limited to 'scripts/Makefile.modbuiltin')

diff --git a/scripts/Makefile.modbuiltin b/scripts/Makefile.modbuiltin
deleted file mode 100644
index 7d4711b88656..000000000000
--- a/scripts/Makefile.modbuiltin
+++ /dev/null
@@ -1,57 +0,0 @@
-# SPDX-License-Identifier: GPL-2.0
-# ==========================================================================
-# Generating modules.builtin
-# ==========================================================================
-
-src := $(obj)
-
-PHONY := __modbuiltin
-__modbuiltin:
-
-include include/config/auto.conf
-# tristate.conf sets tristate variables to uppercase 'Y' or 'M'
-# That way, we get the list of built-in modules in obj-Y
-include include/config/tristate.conf
-
-include scripts/Kbuild.include
-
-ifdef building_out_of_srctree
-# Create output directory if not already present
-_dummy := $(shell [ -d $(obj) ] || mkdir -p $(obj))
-endif
-
-# The filename Kbuild has precedence over Makefile
-kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
-kbuild-file := $(if $(wildcard $(kbuild-dir)/Kbuild),$(kbuild-dir)/Kbuild,$(kbuild-dir)/Makefile)
-include $(kbuild-file)
-
-include scripts/Makefile.lib
-__subdir-Y     := $(patsubst %/,%,$(filter %/, $(obj-Y)))
-subdir-Y       += $(__subdir-Y)
-subdir-ym      := $(sort $(subdir-y) $(subdir-Y) $(subdir-m))
-subdir-ym      := $(addprefix $(obj)/,$(subdir-ym))
-obj-Y          := $(addprefix $(obj)/,$(obj-Y))
-
-modbuiltin-subdirs := $(patsubst %,%/modules.builtin, $(subdir-ym))
-modbuiltin-mods    := $(filter %.ko, $(obj-Y:.o=.ko))
-modbuiltin-target  := $(obj)/modules.builtin
-
-__modbuiltin: $(modbuiltin-target) $(subdir-ym)
-	@:
-
-$(modbuiltin-target): $(subdir-ym) FORCE
-	$(Q)(for m in $(modbuiltin-mods); do echo $$m; done;	\
-	cat /dev/null $(modbuiltin-subdirs)) > $@
-
-PHONY += FORCE
-
-FORCE:
-
-# Descending
-# ---------------------------------------------------------------------------
-
-PHONY += $(subdir-ym)
-$(subdir-ym):
-	$(Q)$(MAKE) $(modbuiltin)=$@
-
-.PHONY: $(PHONY)
-- 
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