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>

4 files changed, 6 insertions, 106 deletions

diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 88c144787e57..3da8321efb74 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -164,12 +164,6 @@ ld-ifversion = $(shell [ $(ld-version) $(1) $(2) ] && echo $(3) || echo $(4))
 build := -f $(srctree)/scripts/Makefile.build obj
 
 ###
-# Shorthand for $(Q)$(MAKE) -f scripts/Makefile.modbuiltin obj=
-# Usage:
-# $(Q)$(MAKE) $(modbuiltin)=dir
-modbuiltin := -f $(srctree)/scripts/Makefile.modbuiltin obj
-
-###
 # Shorthand for $(Q)$(MAKE) -f scripts/Makefile.dtbinst obj=
 # Usage:
 # $(Q)$(MAKE) $(dtbinst)=dir
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)
diff --git a/scripts/kconfig/confdata.c b/scripts/kconfig/confdata.c
index 3569d2dec37c..fb675bd9a809 100644
--- a/scripts/kconfig/confdata.c
+++ b/scripts/kconfig/confdata.c
@@ -710,25 +710,6 @@ static struct conf_printer header_printer_cb =
 	.print_comment = header_print_comment,
 };
 
-/*
- * Tristate printer
- *
- * This printer is used when generating the `include/config/tristate.conf' file.
- */
-static void
-tristate_print_symbol(FILE *fp, struct symbol *sym, const char *value, void *arg)
-{
-
-	if (sym->type == S_TRISTATE && *value != 'n')
-		fprintf(fp, "%s%s=%c\n", CONFIG_, sym->name, (char)toupper(*value));
-}
-
-static struct conf_printer tristate_printer_cb =
-{
-	.print_symbol = tristate_print_symbol,
-	.print_comment = kconfig_print_comment,
-};
-
 static void conf_write_symbol(FILE *fp, struct symbol *sym,
 			      struct conf_printer *printer, void *printer_arg)
 {
@@ -1062,7 +1043,7 @@ int conf_write_autoconf(int overwrite)
 	struct symbol *sym;
 	const char *name;
 	const char *autoconf_name = conf_get_autoconfig_name();
-	FILE *out, *tristate, *out_h;
+	FILE *out, *out_h;
 	int i;
 
 	if (!overwrite && is_present(autoconf_name))
@@ -1077,23 +1058,13 @@ int conf_write_autoconf(int overwrite)
 	if (!out)
 		return 1;
 
-	tristate = fopen(".tmpconfig_tristate", "w");
-	if (!tristate) {
-		fclose(out);
-		return 1;
-	}
-
 	out_h = fopen(".tmpconfig.h", "w");
 	if (!out_h) {
 		fclose(out);
-		fclose(tristate);
 		return 1;
 	}
 
 	conf_write_heading(out, &kconfig_printer_cb, NULL);
-
-	conf_write_heading(tristate, &tristate_printer_cb, NULL);
-
 	conf_write_heading(out_h, &header_printer_cb, NULL);
 
 	for_all_symbols(i, sym) {
@@ -1101,15 +1072,11 @@ int conf_write_autoconf(int overwrite)
 		if (!(sym->flags & SYMBOL_WRITE) || !sym->name)
 			continue;
 
-		/* write symbol to auto.conf, tristate and header files */
+		/* write symbols to auto.conf and autoconf.h */
 		conf_write_symbol(out, sym, &kconfig_printer_cb, (void *)1);
-
-		conf_write_symbol(tristate, sym, &tristate_printer_cb, (void *)1);
-
 		conf_write_symbol(out_h, sym, &header_printer_cb, NULL);
 	}
 	fclose(out);
-	fclose(tristate);
 	fclose(out_h);
 
 	name = getenv("KCONFIG_AUTOHEADER");
@@ -1120,14 +1087,6 @@ int conf_write_autoconf(int overwrite)
 	if (rename(".tmpconfig.h", name))
 		return 1;
 
-	name = getenv("KCONFIG_TRISTATE");
-	if (!name)
-		name = "include/config/tristate.conf";
-	if (make_parent_dir(name))
-		return 1;
-	if (rename(".tmpconfig_tristate", name))
-		return 1;
-
 	if (make_parent_dir(autoconf_name))
 		return 1;
 	/*
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 436379940356..bf0bf9063aaf 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -250,6 +250,10 @@ ${MAKE} -f "${srctree}/scripts/Makefile.modpost" MODPOST_VMLINUX=1
 
 info MODINFO modules.builtin.modinfo
 ${OBJCOPY} -j .modinfo -O binary vmlinux.o modules.builtin.modinfo
+info GEN modules.builtin
+# The second line aids cases where multiple modules share the same object.
+tr '\0' '\n' < modules.builtin.modinfo | sed -n 's/^[[:alnum:]:_]*\.file=//p' |
+	tr ' ' '\n' | uniq | sed -e 's:^:kernel/:' -e 's/$/.ko/' > modules.builtin
 
 btf_vmlinux_bin_o=""
 if [ -n "${CONFIG_DEBUG_INFO_BTF}" ]; then