[PATCH v2 18/26] modpost: generate linker script to collect symbol versions

[Masahiro Yamada <masahiroy@xxxxxxxxxx>]

Merge version CRCs per vmlinux or per module.

These linker scripts will be fed to the final link stage.

Add the new option, -r,  to modpost. This is needed to output the
linker scripts in a different format when CONFIG_MODULE_REL_CRCS=y.

Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
---

Changes in v2:
  - Fix CONFIG_MODULE_REL_CRCS=y case

 .gitignore               |  1 +
 Makefile                 |  1 +
 scripts/Makefile.modpost |  1 +
 scripts/mod/modpost.c    | 37 ++++++++++++++++++++++++++++++++++---
 4 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/.gitignore b/.gitignore
index 265959544978..f9dad6b917e6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -42,6 +42,7 @@
 *.so.dbg
 *.su
 *.symtypes
+*.symver.lds
 *.symversions
 *.tab.[ch]
 *.tar
diff --git a/Makefile b/Makefile
index 7a82bbc505f8..79a69ffd5379 100644
--- a/Makefile
+++ b/Makefile
@@ -1867,6 +1867,7 @@ clean: $(clean-dirs)
 		-o -name '*.c.[012]*.*' \
 		-o -name '*.ll' \
 		-o -name '*.gcno' \
+		-o -name '*.symver.lds' \
 		-o -name '*.*.symversions' \) -type f -print | xargs rm -f
 
 # Generate tags for editors
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index 48585c4d04ad..fecd721537c9 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -46,6 +46,7 @@ include $(srctree)/scripts/Makefile.lib
 
 MODPOST = scripts/mod/modpost								\
 	$(if $(CONFIG_MODVERSIONS),-m)							\
+	$(if $(CONFIG_MODULE_REL_CRCS),-r)						\
 	$(if $(CONFIG_MODULE_SRCVERSION_ALL),-a)					\
 	$(if $(CONFIG_SECTION_MISMATCH_WARN_ONLY),,-E)					\
 	-o $@
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index d8df0f8d3def..935f57f73e40 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -24,6 +24,8 @@
 
 /* Are we using CONFIG_MODVERSIONS? */
 static bool modversions;
+/* Is CONFIG_MODULE_REL_CRCS enabled? */
+static bool modversions_rel_crcs;
 /* Is CONFIG_MODULE_SRCVERSION_ALL set? */
 static bool all_versions;
 /* If we are modposting external module set to 1 */
@@ -2554,9 +2556,21 @@ static void write_dump(const char *fname)
 	free(buf.p);
 }
 
-static void check_symversions(struct module *mod)
+static void write_symversions_lds(struct module *mod)
 {
+	struct buffer buf = { };
 	struct symbol *sym;
+	char lds_file[PATH_MAX];
+	int ret;
+
+	ret = snprintf(lds_file, sizeof(lds_file), "%s.symver.lds", mod->name);
+	if (ret >= sizeof(lds_file)) {
+		error("%s: too long path was truncated\n", lds_file);
+		return;
+	}
+
+	if (modversions_rel_crcs)
+		buf_printf(&buf, "SECTIONS { .rodata : ALIGN(4) {\n");
 
 	list_for_each_entry(sym, &mod->exported_symbols, list) {
 		if (!sym->crc_valid) {
@@ -2564,8 +2578,22 @@ static void check_symversions(struct module *mod)
 			     "Is \"%s\" prototyped in <asm/asm-prototypes.h>?\n",
 			     sym->name, mod->name, mod->is_vmlinux ? "" : ".ko",
 			     sym->name);
+			continue;
 		}
+
+		if (modversions_rel_crcs)
+			buf_printf(&buf, "__crc_%s = .; LONG(0x%08x);\n",
+				   sym->name, sym->crc);
+		else
+			buf_printf(&buf, "__crc_%s = 0x%08x;\n",
+				   sym->name, sym->crc);
 	}
+
+	if (modversions_rel_crcs)
+		buf_printf(&buf, "} }\n");
+
+	write_if_changed(&buf, lds_file);
+	free(buf.p);
 }
 
 static void write_namespace_deps_files(const char *fname)
@@ -2606,7 +2634,7 @@ int main(int argc, char **argv)
 	LIST_HEAD(dump_lists);
 	struct dump_list *dl, *dl2;
 
-	while ((opt = getopt(argc, argv, "ei:mnT:o:awENd:")) != -1) {
+	while ((opt = getopt(argc, argv, "ei:mrnT:o:awENd:")) != -1) {
 		switch (opt) {
 		case 'e':
 			external_module = true;
@@ -2619,6 +2647,9 @@ int main(int argc, char **argv)
 		case 'm':
 			modversions = true;
 			break;
+		case 'r':
+			modversions_rel_crcs = true;
+			break;
 		case 'n':
 			ignore_missing_files = true;
 			break;
@@ -2665,7 +2696,7 @@ int main(int argc, char **argv)
 		int ret;
 
 		if (modversions && !mod->from_dump)
-			check_symversions(mod);
+			write_symversions_lds(mod);
 
 		if (mod->is_vmlinux || mod->from_dump)
 			continue;
-- 
2.32.0