x86-64: Clean up vdso/kernel shared variables
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>
diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
index dcbb28c..5f6ad03 100644
--- a/arch/x86/kernel/vsyscall_64.c
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -49,15 +49,8 @@
__attribute__ ((unused, __section__(".vsyscall_" #nr))) notrace
#define __syscall_clobber "r11","cx","memory"
-/*
- * vsyscall_gtod_data contains data that is :
- * - readonly from vsyscalls
- * - written by timer interrupt or systcl (/proc/sys/kernel/vsyscall64)
- * Try to keep this structure as small as possible to avoid cache line ping pongs
- */
-int __vgetcpu_mode __section_vgetcpu_mode;
-
-struct vsyscall_gtod_data __vsyscall_gtod_data __section_vsyscall_gtod_data =
+DEFINE_VVAR(int, vgetcpu_mode);
+DEFINE_VVAR(struct vsyscall_gtod_data, vsyscall_gtod_data) =
{
.lock = SEQLOCK_UNLOCKED,
.sysctl_enabled = 1,
@@ -97,7 +90,7 @@
*/
static __always_inline void do_get_tz(struct timezone * tz)
{
- *tz = __vsyscall_gtod_data.sys_tz;
+ *tz = VVAR(vsyscall_gtod_data).sys_tz;
}
static __always_inline int gettimeofday(struct timeval *tv, struct timezone *tz)
@@ -126,23 +119,24 @@
unsigned long mult, shift, nsec;
cycle_t (*vread)(void);
do {
- seq = read_seqbegin(&__vsyscall_gtod_data.lock);
+ seq = read_seqbegin(&VVAR(vsyscall_gtod_data).lock);
- vread = __vsyscall_gtod_data.clock.vread;
- if (unlikely(!__vsyscall_gtod_data.sysctl_enabled || !vread)) {
+ vread = VVAR(vsyscall_gtod_data).clock.vread;
+ if (unlikely(!VVAR(vsyscall_gtod_data).sysctl_enabled ||
+ !vread)) {
gettimeofday(tv,NULL);
return;
}
now = vread();
- base = __vsyscall_gtod_data.clock.cycle_last;
- mask = __vsyscall_gtod_data.clock.mask;
- mult = __vsyscall_gtod_data.clock.mult;
- shift = __vsyscall_gtod_data.clock.shift;
+ base = VVAR(vsyscall_gtod_data).clock.cycle_last;
+ mask = VVAR(vsyscall_gtod_data).clock.mask;
+ mult = VVAR(vsyscall_gtod_data).clock.mult;
+ shift = VVAR(vsyscall_gtod_data).clock.shift;
- tv->tv_sec = __vsyscall_gtod_data.wall_time_sec;
- nsec = __vsyscall_gtod_data.wall_time_nsec;
- } while (read_seqretry(&__vsyscall_gtod_data.lock, seq));
+ tv->tv_sec = VVAR(vsyscall_gtod_data).wall_time_sec;
+ nsec = VVAR(vsyscall_gtod_data).wall_time_nsec;
+ } while (read_seqretry(&VVAR(vsyscall_gtod_data).lock, seq));
/* calculate interval: */
cycle_delta = (now - base) & mask;
@@ -171,15 +165,15 @@
{
unsigned seq;
time_t result;
- if (unlikely(!__vsyscall_gtod_data.sysctl_enabled))
+ if (unlikely(!VVAR(vsyscall_gtod_data).sysctl_enabled))
return time_syscall(t);
do {
- seq = read_seqbegin(&__vsyscall_gtod_data.lock);
+ seq = read_seqbegin(&VVAR(vsyscall_gtod_data).lock);
- result = __vsyscall_gtod_data.wall_time_sec;
+ result = VVAR(vsyscall_gtod_data).wall_time_sec;
- } while (read_seqretry(&__vsyscall_gtod_data.lock, seq));
+ } while (read_seqretry(&VVAR(vsyscall_gtod_data).lock, seq));
if (t)
*t = result;
@@ -208,9 +202,9 @@
We do this here because otherwise user space would do it on
its own in a likely inferior way (no access to jiffies).
If you don't like it pass NULL. */
- if (tcache && tcache->blob[0] == (j = __jiffies)) {
+ if (tcache && tcache->blob[0] == (j = VVAR(jiffies))) {
p = tcache->blob[1];
- } else if (__vgetcpu_mode == VGETCPU_RDTSCP) {
+ } else if (VVAR(vgetcpu_mode) == VGETCPU_RDTSCP) {
/* Load per CPU data from RDTSCP */
native_read_tscp(&p);
} else {