Introduce new section reference annotations tags: __ref, __refdata, __refconst

Today we have the following annotations for functions/data
referencing __init/__exit functions / data:

__init_refok     => for init functions
__initdata_refok => for init data
__exit_refok     => for exit functions

There is really no difference between the __init and __exit
versions and simplify it and to introduce a shorter annotation
the following new annotations are introduced:

__ref      => for functions (code) that
              references __*init / __*exit
__refdata  => for variables
__refconst => for const variables

Whit this annotation is it more obvious what the annotation
is for and there is no longer the arbitary division
between __init and __exit code.

The mechanishm is the same as before - a special section
is created which is made part of the usual sections
in the linker script.

We will start to see annotations like this:

-static struct pci_serial_quirk pci_serial_quirks[] = {
+static const struct pci_serial_quirk pci_serial_quirks[] __refconst = {
-----------------
-static struct notifier_block __cpuinitdata cpuid_class_cpu_notifier =
+static struct notifier_block cpuid_class_cpu_notifier __refdata =
----------------
-static int threshold_cpu_callback(struct notifier_block *nfb,
+static int __ref threshold_cpu_callback(struct notifier_block *nfb,

[The above is just random samples].

Note: No modifications were needed in modpost
to support the new sections due to the newly introduced
blacklisting.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

include/asm-generic/vmlinux.lds.h

@@ -42,6 +42,7 @@
 #define DATA_DATA							\
 	*(.data)							\
 	*(.data.init.refok)						\
+	*(.ref.data)							\
 	DEV_KEEP(init.data)						\
 	DEV_KEEP(exit.data)						\
 	CPU_KEEP(init.data)						\
@@ -169,6 +170,7 @@
 									\
 	/* __*init sections */						\
 	__init_rodata : AT(ADDR(__init_rodata) - LOAD_OFFSET) {		\
+		*(.ref.rodata)						\
 		DEV_KEEP(init.rodata)					\
 		DEV_KEEP(exit.rodata)					\
 		CPU_KEEP(init.rodata)					\
@@ -202,6 +204,7 @@
 #define TEXT_TEXT							\
 		ALIGN_FUNCTION();					\
 		*(.text)						\
+		*(.ref.text)						\
 		*(.text.init.refok)					\
 		*(.exit.text.refok)					\
 	DEV_KEEP(init.text)						\