x86/module: Use text_mutex in apply_relocate_add()

Now that the livepatch code no longer needs the text_mutex for changing
module permissions, move its usage down to apply_relocate_add().

Note the s390 version of apply_relocate_add() doesn't need to use the
text_mutex because it already uses s390_kernel_write_lock, which
accomplishes the same task.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

Author: jpoimboe

arch/x86/kernel/module.c

@@ -18,6 +18,7 @@
 #include <linux/gfp.h>
 #include <linux/jump_label.h>
 #include <linux/random.h>
+#include <linux/memory.h>
 
 #include <asm/text-patching.h>
 #include <asm/page.h>
@@ -227,14 +228,18 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
 	bool early = me->state == MODULE_STATE_UNFORMED;
 	void *(*write)(void *, const void *, size_t) = memcpy;
 
-	if (!early)
+	if (!early) {
 		write = text_poke;
+		mutex_lock(&text_mutex);
+	}
 
 	ret = __apply_relocate_add(sechdrs, strtab, symindex, relsec, me,
 				   write);
 
-	if (!early)
+	if (!early) {
 		text_poke_sync();
+		mutex_unlock(&text_mutex);
+	}
 
 	return ret;
 }

kernel/livepatch/core.c

@@ -775,19 +775,13 @@ static int klp_init_object_loaded(struct klp_patch *patch,
 	int ret;
 
 	if (klp_is_module(obj)) {
-
-		mutex_lock(&text_mutex);
-
 		/*
 		 * Only write module-specific relocations here
 		 * (.klp.rela.{module}.*).  vmlinux-specific relocations were
 		 * written earlier during the initialization of the klp module
 		 * itself.
 		 */
 		ret = klp_apply_object_relocs(patch, obj);
-
-		mutex_unlock(&text_mutex);
-
 		if (ret)
 			return ret;
 	}