arm64: Add support for CLOCK_MONOTONIC_RAW in clock_gettime() vDSO

So far the arm64 clock_gettime() vDSO implementation only supported
the following clocks, falling back to the syscall for the others:
- CLOCK_REALTIME{,_COARSE}
- CLOCK_MONOTONIC{,_COARSE}

This patch adds support for the CLOCK_MONOTONIC_RAW clock, taking
advantage of the recent refactoring of the vDSO time functions. Like
the non-_COARSE clocks, this only works when the "arch_sys_counter"
clocksource is in use (allowing us to read the current time from the
virtual counter register), otherwise we also have to fall back to the
syscall.

Most of the data is shared with CLOCK_MONOTONIC, and the algorithm is
similar. The reference implementation in kernel/time/timekeeping.c
shows that:
- CLOCK_MONOTONIC = tk->wall_to_monotonic + tk->xtime_sec +
  timekeeping_get_ns(&tk->tkr_mono)
- CLOCK_MONOTONIC_RAW = tk->raw_time + timekeeping_get_ns(&tk->tkr_raw)
- tkr_mono and tkr_raw are identical (in particular, same
  clocksource), except these members:
  * mult (only mono's multiplier is NTP-adjusted)
  * xtime_nsec (always 0 for raw)

Therefore, tk->raw_time and tkr_raw->mult are now also stored in the
vDSO data page.

Cc: Ali Saidi <ali.saidi@arm.com>
Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Reviewed-by: Dave Martin <dave.martin@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/arch/arm64/include/asm/vdso_datapage.h b/arch/arm64/include/asm/vdso_datapage.h
index de66199673d7..2b9a63771eda 100644
--- a/arch/arm64/include/asm/vdso_datapage.h
+++ b/arch/arm64/include/asm/vdso_datapage.h
@@ -22,6 +22,8 @@
 
 struct vdso_data {
 	__u64 cs_cycle_last;	/* Timebase at clocksource init */
+	__u64 raw_time_sec;	/* Raw time */
+	__u64 raw_time_nsec;
 	__u64 xtime_clock_sec;	/* Kernel time */
 	__u64 xtime_clock_nsec;
 	__u64 xtime_coarse_sec;	/* Coarse time */
@@ -29,8 +31,10 @@ struct vdso_data {
 	__u64 wtm_clock_sec;	/* Wall to monotonic time */
 	__u64 wtm_clock_nsec;
 	__u32 tb_seq_count;	/* Timebase sequence counter */
-	__u32 cs_mult;		/* Clocksource multiplier */
-	__u32 cs_shift;		/* Clocksource shift */
+	/* cs_* members must be adjacent and in this order (ldp accesses) */
+	__u32 cs_mono_mult;	/* NTP-adjusted clocksource multiplier */
+	__u32 cs_shift;		/* Clocksource shift (mono = raw) */
+	__u32 cs_raw_mult;	/* Raw clocksource multiplier */
 	__u32 tz_minuteswest;	/* Whacky timezone stuff */
 	__u32 tz_dsttime;
 	__u32 use_syscall;