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x86-64: Clean up vdso/kernel shared variables

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Variables that are shared between the vdso and the kernel are
currently a bit of a mess.  They are each defined with their own
magic, they are accessed differently in the kernel, the vsyscall page,
and the vdso, and one of them (vsyscall_clock) doesn't even really
exist.

This changes them all to use a common mechanism.  All of them are
delcared in vvar.h with a fixed address (validated by the linker
script).  In the kernel (as before), they look like ordinary
read-write variables.  In the vsyscall page and the vdso, they are
accessed through a new macro VVAR, which gives read-only access.

The vdso is now loaded verbatim into memory without any fixups.  As a
side bonus, access from the vdso is faster because a level of
indirection is removed.

While we're at it, pack jiffies and vgetcpu_mode into the same
cacheline.

Signed-off-by: Andy Lutomirski <luto@mit.edu>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Borislav Petkov <bp@amd64.org>
Link: http://lkml.kernel.org/r/%3C7357882fbb51fa30491636a7b6528747301b7ee9.1306156808.git.luto%40mit.edu%3E
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Andy Lutomirski 2011-05-23 09:31:24 -04:00 • committed by Thomas Gleixner
parent d762f43831
commit 8c49d9a74b
15 changed files with 91 additions and 145 deletions
Download patch file Download diff file Expand all files Collapse all files

12
arch/x86/include/asm/vsyscall.h
View file

@ -16,27 +16,19 @@ enum vsyscall_num {
#ifdef __KERNEL__
#include <linux/seqlock.h>
#define __section_vgetcpu_mode __attribute__ ((unused, __section__ (".vgetcpu_mode"), aligned(16)))
#define __section_jiffies __attribute__ ((unused, __section__ (".jiffies"), aligned(16)))
/* Definitions for CONFIG_GENERIC_TIME definitions */
#define __section_vsyscall_gtod_data __attribute__ \
((unused, __section__ (".vsyscall_gtod_data"),aligned(16)))
#define __section_vsyscall_clock __attribute__ \
((unused, __section__ (".vsyscall_clock"),aligned(16)))
#define __vsyscall_fn \
__attribute__ ((unused, __section__(".vsyscall_fn"))) notrace
#define VGETCPU_RDTSCP 1
#define VGETCPU_LSL 2
extern int __vgetcpu_mode;
extern volatile unsigned long __jiffies;
/* kernel space (writeable) */
extern int vgetcpu_mode;
extern struct timezone sys_tz;
#include <asm/vvar.h>
extern void map_vsyscall(void);
#endif /* __KERNEL__ */