kbuild: set correct KBUILD_MODNAME when using well known kernel symbols as module names

This patch fixes a problem when we use well known kernel symbols as module
names.

For example, if module source name is current.c, idle_stack.c or etc.,
we have a bad KBUILD_MODNAME value.
For example, KBUILD_MODNAME will be "get_current()" instead of "current", or
"(init_thread_union.stack)" instead of "idle_task".

The trick is to define a stringify macro on the commandline - named
KBUILD_STR for namespace reasons - and then to stringify the module
name.

There are a few uses of KBUILD_MODNAME throughout the tree but the usage
is for debug and will not be harmed by this change so left untouched for now.

While at it KBUILD_BASENAME was changed too. Any spinlock usage in the
unix module would have created wrong section names without it.
Usage in spinlock.h fixed so it no longer stringify KBUILD_BASENAME.

Original patch from Ustyogov Roman - all bugs introduced by me.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

include/linux/spinlock.h

@@ -59,8 +59,7 @@
 /*
  * Must define these before including other files, inline functions need them
  */
-#define LOCK_SECTION_NAME                       \
-        ".text.lock." __stringify(KBUILD_BASENAME)
+#define LOCK_SECTION_NAME ".text.lock."KBUILD_BASENAME
 
 #define LOCK_SECTION_START(extra)               \
         ".subsection 1\n\t"                     \

scripts/Makefile.lib

@@ -81,8 +81,10 @@ obj-dirs	:= $(addprefix $(obj)/,$(obj-dirs))
 # Note: It's possible that one object gets potentially linked into more
 #       than one module. In that case KBUILD_MODNAME will be set to foo_bar,
 #       where foo and bar are the name of the modules.
-basename_flags = -DKBUILD_BASENAME=$(subst $(comma),_,$(subst -,_,$(*F)))
-modname_flags  = $(if $(filter 1,$(words $(modname))),-DKBUILD_MODNAME=$(subst $(comma),_,$(subst -,_,$(modname))))
+name-fix = $(subst $(comma),_,$(subst -,_,$1))
+basename_flags = -D"KBUILD_BASENAME=KBUILD_STR($(call name-fix,$(*F)))"
+modname_flags  = $(if $(filter 1,$(words $(modname))),\
+                 -D"KBUILD_MODNAME=KBUILD_STR($(call name-fix,$(modname)))")
 
 _c_flags       = $(CFLAGS) $(EXTRA_CFLAGS) $(CFLAGS_$(*F).o)
 _a_flags       = $(AFLAGS) $(EXTRA_AFLAGS) $(AFLAGS_$(*F).o)
@@ -113,7 +115,7 @@ endif
 
 c_flags        = -Wp,-MD,$(depfile) $(NOSTDINC_FLAGS) $(CPPFLAGS) \
 		 $(__c_flags) $(modkern_cflags) \
-		 $(basename_flags) $(modname_flags)
+		 -D"KBUILD_STR(s)=\#s" $(basename_flags) $(modname_flags)
 
 a_flags        = -Wp,-MD,$(depfile) $(NOSTDINC_FLAGS) $(CPPFLAGS) \
 		 $(__a_flags) $(modkern_aflags)

scripts/mod/modpost.c

@@ -539,10 +539,9 @@ add_header(struct buffer *b, struct module *mod)
 	buf_printf(b, "\n");
 	buf_printf(b, "MODULE_INFO(vermagic, VERMAGIC_STRING);\n");
 	buf_printf(b, "\n");
-	buf_printf(b, "#undef unix\n"); /* We have a module called "unix" */
 	buf_printf(b, "struct module __this_module\n");
 	buf_printf(b, "__attribute__((section(\".gnu.linkonce.this_module\"))) = {\n");
-	buf_printf(b, " .name = __stringify(KBUILD_MODNAME),\n");
+	buf_printf(b, " .name = KBUILD_MODNAME,\n");
 	if (mod->has_init)
 		buf_printf(b, " .init = init_module,\n");
 	if (mod->has_cleanup)