/*
* vvar.h: Shared vDSO/kernel variable declarations
* Copyright (c) 2011 Andy Lutomirski
* Subject to the GNU General Public License, version 2
*
* A handful of variables are accessible (read-only) from userspace
* code in the vsyscall page and the vdso. They are declared here.
* Some other file must define them with DEFINE_VVAR.
*
* In normal kernel code, they are used like any other variable.
* In user code, they are accessed through the VVAR macro.
*
* These variables live in a page of kernel data that has an extra RO
* mapping for userspace. Each variable needs a unique offset within
* that page; specify that offset with the DECLARE_VVAR macro. (If
* you mess up, the linker will catch it.)
*/

/* Base address of vvars. This is not ABI. */
#define VVAR_ADDRESS (-10*1024*1024 - 4096)

#if defined(__VVAR_KERNEL_LDS)

/* The kernel linker script defines its own magic to put vvars in the
* right place.
*/
#define DECLARE_VVAR(offset, type, name) \
EMIT_VVAR(name, offset)

#else

#define DECLARE_VVAR(offset, type, name) \
static type const * const vvaraddr_ ## name = \
(void *)(VVAR_ADDRESS + (offset));

#define DEFINE_VVAR(type, name) \
type name \
__attribute__((section(".vvar_" #name), aligned(16))) __visible

#define VVAR(name) (*vvaraddr_ ## name)

#endif

/* DECLARE_VVAR(offset, type, name) */

DECLARE_VVAR(0, volatile unsigned long, jiffies)
DECLARE_VVAR(16, int, vgetcpu_mode)
DECLARE_VVAR(128, struct vsyscall_gtod_data, vsyscall_gtod_data)

#undef DECLARE_VVAR