[deliverable/linux.git] / arch / x86 / include / asm / vvar.h

/*
 * 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.)
 */

#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

extern char __vvar_page;

/* Base address of vvars.  This is not ABI. */
#ifdef CONFIG_X86_64
#define VVAR_ADDRESS (-10*1024*1024 - 4096)
#else
#define VVAR_ADDRESS (&__vvar_page)
#endif

#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
Commit	Line	Data
8c49d9a7 AL	1	/*
	2	* vvar.h: Shared vDSO/kernel variable declarations
	3	* Copyright (c) 2011 Andy Lutomirski
	4	* Subject to the GNU General Public License, version 2
	5	*
	6	* A handful of variables are accessible (read-only) from userspace
	7	* code in the vsyscall page and the vdso. They are declared here.
	8	* Some other file must define them with DEFINE_VVAR.
	9	*
	10	* In normal kernel code, they are used like any other variable.
	11	* In user code, they are accessed through the VVAR macro.
	12	*
9fd67b4e AL	13	* These variables live in a page of kernel data that has an extra RO
	14	* mapping for userspace. Each variable needs a unique offset within
	15	* that page; specify that offset with the DECLARE_VVAR macro. (If
	16	* you mess up, the linker will catch it.)
8c49d9a7 AL	17	*/
8c49d9a7 AL	18
8c49d9a7 AL	19	#if defined(__VVAR_KERNEL_LDS)
	20
	21	/* The kernel linker script defines its own magic to put vvars in the
	22	* right place.
	23	*/
	24	#define DECLARE_VVAR(offset, type, name) \
9fd67b4e	25	EMIT_VVAR(name, offset)
8c49d9a7 AL	26
	27	#else
	28
d2312e33 SS	29	extern char __vvar_page;
	30
	31	/* Base address of vvars. This is not ABI. */
	32	#ifdef CONFIG_X86_64
	33	#define VVAR_ADDRESS (-1010241024 - 4096)
	34	#else
	35	#define VVAR_ADDRESS (&__vvar_page)
	36	#endif
	37
8c49d9a7 AL	38	#define DECLARE_VVAR(offset, type, name) \
8c49d9a7 AL	39	static type const * const vvaraddr_ ## name = \
9fd67b4e	40	(void *)(VVAR_ADDRESS + (offset));
8c49d9a7 AL	41
8c49d9a7 AL	42	#define DEFINE_VVAR(type, name) \
9fd67b4e	43	type name \
28596b6a	44	__attribute__((section(".vvar_" #name), aligned(16))) __visible
8c49d9a7 AL	45
	46	#define VVAR(name) (*vvaraddr_ ## name)
	47
	48	#endif
	49
	50	/* DECLARE_VVAR(offset, type, name) */
	51
	52	DECLARE_VVAR(0, volatile unsigned long, jiffies)
6879eb2d	53	DECLARE_VVAR(16, int, vgetcpu_mode)
8c49d9a7 AL	54	DECLARE_VVAR(128, struct vsyscall_gtod_data, vsyscall_gtod_data)
	55
	56	#undef DECLARE_VVAR