kbuild: compile constant module information only once

Various information about modules is compiled into the info sections.
For that a dedicated .mod.c file is generated by modpost for each module
and then linked into the module.
However most of the information in the .mod.c is the same for all
modules, internal and external.
Split the shared information into a dedicated source file that is
compiled once and then linked into all modules.

This avoids frequent rebuilds for all .mod.c files when using
CONFIG_LOCALVERSION_AUTO because the local version ends up in .mod.c
through UTS_RELEASE and VERMAGIC_STRING.
The modules are still relinked in this case.

The code is also easier to maintain as it's now in a proper source file
instead of an inline string literal.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
index 306a6bb86e4dc80dc8eaec5836ffa2c20f4b45f6..6b1b72257b29cf0411d14cac81f1ab4694d75a7e 100644 (file)
--- a/scripts/Makefile.modfinal
+++ b/scripts/Makefile.modfinal
@@ -30,6 +30,9 @@ quiet_cmd_cc_o_c = CC [M]  $@
 %.mod.o: %.mod.c FORCE
        $(call if_changed_dep,cc_o_c)
 
+$(extmod_prefix).module-common.o: $(srctree)/scripts/module-common.c FORCE
+       $(call if_changed_dep,cc_o_c)
+
 quiet_cmd_ld_ko_o = LD [M]  $@
       cmd_ld_ko_o +=                                                   \
        $(LD) -r $(KBUILD_LDFLAGS)                                      \
@@ -54,13 +57,13 @@ if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check),      \
        printf '%s\n' 'savedcmd_$@ := $(make-cmd)' > $(dot-target).cmd, @:)
 
 # Re-generate module BTFs if either module's .ko or vmlinux changed
-%.ko: %.o %.mod.o scripts/module.lds $(and $(CONFIG_DEBUG_INFO_BTF_MODULES),$(KBUILD_BUILTIN),vmlinux) FORCE
+%.ko: %.o %.mod.o $(extmod_prefix).module-common.o scripts/module.lds $(and $(CONFIG_DEBUG_INFO_BTF_MODULES),$(KBUILD_BUILTIN),vmlinux) FORCE
        +$(call if_changed_except,ld_ko_o,vmlinux)
 ifdef CONFIG_DEBUG_INFO_BTF_MODULES
        +$(if $(newer-prereqs),$(call cmd,btf_ko))
 endif
 
-targets += $(modules:%.o=%.ko) $(modules:%.o=%.mod.o)
+targets += $(modules:%.o=%.ko) $(modules:%.o=%.mod.o) $(extmod_prefix).module-common.o
 
 # Add FORCE to the prerequisites of a target to force it to be always rebuilt.
 # ---------------------------------------------------------------------------

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index c8cd5d822bb64cd95d0a3c5c9e5473e89c8ce9dd..107393a8c48a5993dbe456702fec0652a967ee86 100644 (file)
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -1755,26 +1755,9 @@ static void check_modname_len(struct module *mod)
 static void add_header(struct buffer *b, struct module *mod)
 {
        buf_printf(b, "#include <linux/module.h>\n");
-       /*
-        * Include build-salt.h after module.h in order to
-        * inherit the definitions.
-        */
-       buf_printf(b, "#define INCLUDE_VERMAGIC\n");
-       buf_printf(b, "#include <linux/build-salt.h>\n");
-       buf_printf(b, "#include <linux/elfnote-lto.h>\n");
        buf_printf(b, "#include <linux/export-internal.h>\n");
-       buf_printf(b, "#include <linux/vermagic.h>\n");
        buf_printf(b, "#include <linux/compiler.h>\n");
        buf_printf(b, "\n");
-       buf_printf(b, "#ifdef CONFIG_UNWINDER_ORC\n");
-       buf_printf(b, "#include <asm/orc_header.h>\n");
-       buf_printf(b, "ORC_HEADER;\n");
-       buf_printf(b, "#endif\n");
-       buf_printf(b, "\n");
-       buf_printf(b, "BUILD_SALT;\n");
-       buf_printf(b, "BUILD_LTO_INFO;\n");
-       buf_printf(b, "\n");
-       buf_printf(b, "MODULE_INFO(vermagic, VERMAGIC_STRING);\n");
        buf_printf(b, "MODULE_INFO(name, KBUILD_MODNAME);\n");
        buf_printf(b, "\n");
        buf_printf(b, "__visible struct module __this_module\n");
@@ -1792,12 +1775,6 @@ static void add_header(struct buffer *b, struct module *mod)
        if (!external_module)
                buf_printf(b, "\nMODULE_INFO(intree, \"Y\");\n");
 
-       buf_printf(b,
-                  "\n"
-                  "#ifdef CONFIG_MITIGATION_RETPOLINE\n"
-                  "MODULE_INFO(retpoline, \"Y\");\n"
-                  "#endif\n");
-
        if (strstarts(mod->name, "drivers/staging"))
                buf_printf(b, "\nMODULE_INFO(staging, \"Y\");\n");
 

diff --git a/scripts/module-common.c b/scripts/module-common.c
new file mode 100644 (file)
index 0000000..12fbc6d
--- /dev/null
+++ b/scripts/module-common.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/module.h>
+/*
+ * Include build-salt.h after module.h in order to
+ * inherit the definitions.
+ */
+#define INCLUDE_VERMAGIC
+#include <linux/build-salt.h>
+#include <linux/elfnote-lto.h>
+#include <linux/vermagic.h>
+
+#ifdef CONFIG_UNWINDER_ORC
+#include <asm/orc_header.h>
+ORC_HEADER;
+#endif
+
+BUILD_SALT;
+BUILD_LTO_INFO;
+
+MODULE_INFO(vermagic, VERMAGIC_STRING);
+
+#ifdef CONFIG_MITIGATION_RETPOLINE
+MODULE_INFO(retpoline, "Y");
+#endif