From: Masahiro Yamada <masahiroy@kernel.org>
Date: Thu, 25 Mar 2021 18:54:09 +0000 (+0900)
Subject: kbuild: generate Module.symvers only when vmlinux exists
X-Git-Tag: accepted/tizen/unified/20230118.172025~7334^2~25
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=69bc8d386aebbd91a6bb44b6d33f77c8dfa9ed8c;p=platform%2Fkernel%2Flinux-rpi.git

kbuild: generate Module.symvers only when vmlinux exists

The external module build shows the following warning if Module.symvers
is missing in the kernel tree.

  WARNING: Symbol version dump "Module.symvers" is missing.
           Modules may not have dependencies or modversions.

I think this is an important heads-up because the resulting modules may
not work as expected. This happens when you did not build the entire
kernel tree, for example, you might have prepared the minimal setups
for external modules by 'make defconfig && make modules_preapre'.

A problem is that 'make modules' creates Module.symvers even without
vmlinux. In this case, that warning is suppressed since Module.symvers
already exists in spite of its incomplete content.

The incomplete (i.e. invalid) Module.symvers should not be created.

This commit changes the second pass of modpost to dump symbols into
modules-only.symvers. The final Module.symvers is created by
concatenating vmlinux.symvers and modules-only.symvers if both exist.

Module.symvers is supposed to collect symbols from both vmlinux and
modules. It might be a bit confusing, and I am not quite sure if it
is an official interface, but presumably it is difficult to rename it
because some tools (e.g. kmod) parse it.

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

diff --git a/.gitignore b/.gitignore
index 3adea59..df8d314 100644
--- a/.gitignore
+++ b/.gitignore
@@ -57,6 +57,7 @@ modules.order
 /tags
 /TAGS
 /linux
+/modules-only.symvers
 /vmlinux
 /vmlinux.32
 /vmlinux.map
diff --git a/Documentation/dontdiff b/Documentation/dontdiff
index ac42ad8..910b30a 100644
--- a/Documentation/dontdiff
+++ b/Documentation/dontdiff
@@ -178,6 +178,7 @@ mktables
 mktree
 mkutf8data
 modpost
+modules-only.symvers
 modules.builtin
 modules.builtin.modinfo
 modules.nsdeps
diff --git a/Makefile b/Makefile
index 2b161f5..ed8bd81 100644
--- a/Makefile
+++ b/Makefile
@@ -1532,7 +1532,7 @@ endif # CONFIG_MODULES
 # make distclean Remove editor backup files, patch leftover files and the like
 
 # Directories & files removed with 'make clean'
-CLEAN_FILES += include/ksym vmlinux.symvers \
+CLEAN_FILES += include/ksym vmlinux.symvers modules-only.symvers \
 	       modules.builtin modules.builtin.modinfo modules.nsdeps \
 	       compile_commands.json .thinlto-cache
 
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index df57e25..3f5b09a 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -68,7 +68,20 @@ else
 ifeq ($(KBUILD_EXTMOD),)
 
 input-symdump := vmlinux.symvers
-output-symdump := Module.symvers
+output-symdump := modules-only.symvers
+
+quiet_cmd_cat = GEN     $@
+      cmd_cat = cat $(real-prereqs) > $@
+
+ifneq ($(wildcard vmlinux.symvers),)
+
+__modpost: Module.symvers
+Module.symvers: vmlinux.symvers modules-only.symvers FORCE
+	$(call if_changed,cat)
+
+targets += Module.symvers
+
+endif
 
 else
 
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 24725e5..10c3fba 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -2423,19 +2423,6 @@ fail:
 	fatal("parse error in symbol dump file\n");
 }
 
-/* For normal builds always dump all symbols.
- * For external modules only dump symbols
- * that are not read from kernel Module.symvers.
- **/
-static int dump_sym(struct symbol *sym)
-{
-	if (!external_module)
-		return 1;
-	if (sym->module->from_dump)
-		return 0;
-	return 1;
-}
-
 static void write_dump(const char *fname)
 {
 	struct buffer buf = { };
@@ -2446,7 +2433,7 @@ static void write_dump(const char *fname)
 	for (n = 0; n < SYMBOL_HASH_SIZE ; n++) {
 		symbol = symbolhash[n];
 		while (symbol) {
-			if (dump_sym(symbol)) {
+			if (!symbol->module->from_dump) {
 				namespace = symbol->namespace;
 				buf_printf(&buf, "0x%08x\t%s\t%s\t%s\t%s\n",
 					   symbol->crc, symbol->name,