[RFC] __ref annotation of function/data referencing __init/__exit

Sam Ravnborg
2008-01-26T18:44:45Z

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

__init_refok for functions
__initdata_refok for data

and
_exit_refok for functions

To simplify it and to introduce a shorter annotation I
will suggest the following annotation:

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

This should hopefully make it more intuitive what
the annotation is for.

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 would then start to see annotations like this:

* Specific entries must come before more generic entries.
*/
-static struct pci_serial_quirk pci_serial_quirks[] = {
+static const struct pci_serial_quirk pci_serial_quirks[] __refconst = {
/*
* AFAVLAB cards - these may be called via parport_serial
* It is not clear whether this applies to all products.

-----------------

}

-static struct notifier_block __cpuinitdata cpuid_class_cpu_notifier =
+static struct notifier_block cpuid_class_cpu_notifier __refdata =
{
.notifier_call = cpuid_class_cpu_callback,
};

----------------

/* get notified when a cpu comes on/off */
-static int threshold_cpu_callback(struct notifier_block *nfb,
+static int __ref threshold_cpu_callback(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{

[The above is just samples - please do not comment on their
correctness in this thread].

The patch (on top of kbuild.git) is below.

Sam

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 2948530..76df771 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/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) \
diff --git a/include/linux/init.h b/include/linux/init.h
index dde1eaa..2efbda0 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -52,12 +52,26 @@
* when early init has completed so all such references are potential bugs.
* For exit sections the same issue exists.
* The following markers are used for the cases where the reference to
- * the init/exit section (code or data) is valid and will teach modpost
- * not to issue a warning.
+ * the *init / *exit section (code or data) is valid and will teach
+ * modpost not to issue a warning.
* The markers follow same syntax rules as __init / __initdata. */
-#define __init_refok noinline __section(.text.init.refok)
-#define __initdata_refok __section(.data.init.refok)
-#define __exit_refok noinline __section(.exit.text.refok)
+#define __ref __section(.ref.text) noinline
+#define __refdata __section(.ref.data)
+#define __refconst __section(.ref.rodata)
+
+/* backward compatibility note
+ * A few places hardcode the old section names:
+ * .text.init.refok
+ * .data.init.refok
+ * .exit.text.refok
+ * They should be converted to use the defines from this file
+ */
+
+/* compatibility defines */
+#define __init_refok __ref
+#define __initdata_refok __refdata
+#define __exit_refok __ref
+

#ifdef MODULE
#define __exitused
@@ -93,11 +107,9 @@

/* For assembly routines */
#define __INIT .section ".init.text","ax"
-#define __INIT_REFOK .section ".text.init.refok","ax"
#define __FINIT .previous

#define __INITDATA .section ".init.data","aw"
-#define __INITDATA_REFOK .section ".data.init.refok","aw"

#define __DEVINIT .section ".devinit.text", "ax"
#define __DEVINITDATA .section ".devinit.data", "aw"
@@ -108,6 +120,14 @@
#define __MEMINIT .section ".meminit.text", "ax"
#define __MEMINITDATA .section ".meminit.data", "aw"

+/* silence warnings when references are OK */
+#define __REF .section ".ref.text", "ax"
+#define __REFDATA .section ".ref.data", "aw"
+#define __REFCONST .section ".ref.rodata", "aw"
+/* backward compatibility */
+#define __INIT_REFOK .section __REF
+#define __INITDATA_REFOK .section __REFDATA
+
#ifndef __ASSEMBLY__
/*
* Used for initialization calls..