[PATCH v2 2/2] arm64: Add support for CLOCK_MONOTONIC_RAW in clock_gettime() vDSO
Kevin Brodsky
kevin.brodsky at arm.com
Tue Jul 12 03:24:00 PDT 2016
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 at arm.com>
Signed-off-by: Kevin Brodsky <kevin.brodsky at arm.com>
Reviewed-by: Dave Martin <dave.martin at arm.com>
Acked-by: Will Deacon <will.deacon at arm.com>
---
arch/arm64/include/asm/vdso_datapage.h | 8 +++--
arch/arm64/kernel/asm-offsets.c | 6 +++-
arch/arm64/kernel/vdso.c | 8 ++++-
arch/arm64/kernel/vdso/gettimeofday.S | 57 +++++++++++++++++++++++++++-------
4 files changed, 64 insertions(+), 15 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;
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 2f4ba774488a..c88508b95f87 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -78,6 +78,7 @@ int main(void)
BLANK();
DEFINE(CLOCK_REALTIME, CLOCK_REALTIME);
DEFINE(CLOCK_MONOTONIC, CLOCK_MONOTONIC);
+ DEFINE(CLOCK_MONOTONIC_RAW, CLOCK_MONOTONIC_RAW);
DEFINE(CLOCK_REALTIME_RES, MONOTONIC_RES_NSEC);
DEFINE(CLOCK_REALTIME_COARSE, CLOCK_REALTIME_COARSE);
DEFINE(CLOCK_MONOTONIC_COARSE,CLOCK_MONOTONIC_COARSE);
@@ -85,6 +86,8 @@ int main(void)
DEFINE(NSEC_PER_SEC, NSEC_PER_SEC);
BLANK();
DEFINE(VDSO_CS_CYCLE_LAST, offsetof(struct vdso_data, cs_cycle_last));
+ DEFINE(VDSO_RAW_TIME_SEC, offsetof(struct vdso_data, raw_time_sec));
+ DEFINE(VDSO_RAW_TIME_NSEC, offsetof(struct vdso_data, raw_time_nsec));
DEFINE(VDSO_XTIME_CLK_SEC, offsetof(struct vdso_data, xtime_clock_sec));
DEFINE(VDSO_XTIME_CLK_NSEC, offsetof(struct vdso_data, xtime_clock_nsec));
DEFINE(VDSO_XTIME_CRS_SEC, offsetof(struct vdso_data, xtime_coarse_sec));
@@ -92,7 +95,8 @@ int main(void)
DEFINE(VDSO_WTM_CLK_SEC, offsetof(struct vdso_data, wtm_clock_sec));
DEFINE(VDSO_WTM_CLK_NSEC, offsetof(struct vdso_data, wtm_clock_nsec));
DEFINE(VDSO_TB_SEQ_COUNT, offsetof(struct vdso_data, tb_seq_count));
- DEFINE(VDSO_CS_MULT, offsetof(struct vdso_data, cs_mult));
+ DEFINE(VDSO_CS_MONO_MULT, offsetof(struct vdso_data, cs_mono_mult));
+ DEFINE(VDSO_CS_RAW_MULT, offsetof(struct vdso_data, cs_raw_mult));
DEFINE(VDSO_CS_SHIFT, offsetof(struct vdso_data, cs_shift));
DEFINE(VDSO_TZ_MINWEST, offsetof(struct vdso_data, tz_minuteswest));
DEFINE(VDSO_TZ_DSTTIME, offsetof(struct vdso_data, tz_dsttime));
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 9fefb005812a..076312b17d4f 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -214,10 +214,16 @@ void update_vsyscall(struct timekeeper *tk)
vdso_data->wtm_clock_nsec = tk->wall_to_monotonic.tv_nsec;
if (!use_syscall) {
+ /* tkr_mono.cycle_last == tkr_raw.cycle_last */
vdso_data->cs_cycle_last = tk->tkr_mono.cycle_last;
+ vdso_data->raw_time_sec = tk->raw_time.tv_sec;
+ vdso_data->raw_time_nsec = tk->raw_time.tv_nsec;
vdso_data->xtime_clock_sec = tk->xtime_sec;
vdso_data->xtime_clock_nsec = tk->tkr_mono.xtime_nsec;
- vdso_data->cs_mult = tk->tkr_mono.mult;
+ /* tkr_raw.xtime_nsec == 0 */
+ vdso_data->cs_mono_mult = tk->tkr_mono.mult;
+ vdso_data->cs_raw_mult = tk->tkr_raw.mult;
+ /* tkr_mono.shift == tkr_raw.shift */
vdso_data->cs_shift = tk->tkr_mono.shift;
}
diff --git a/arch/arm64/kernel/vdso/gettimeofday.S b/arch/arm64/kernel/vdso/gettimeofday.S
index c06919ee29e1..e00b4671bd7c 100644
--- a/arch/arm64/kernel/vdso/gettimeofday.S
+++ b/arch/arm64/kernel/vdso/gettimeofday.S
@@ -87,6 +87,15 @@ x_tmp .req x8
msub \res_nsec, x_tmp, \nsec_to_sec, \res_nsec
.endm
+ /*
+ * Returns in res_{sec,nsec} the timespec based on the clock_raw delta,
+ * used for CLOCK_MONOTONIC_RAW.
+ */
+ .macro get_ts_clock_raw res_sec, res_nsec, clock_nsec, nsec_to_sec
+ udiv \res_sec, \clock_nsec, \nsec_to_sec
+ msub \res_nsec, \res_sec, \nsec_to_sec, \clock_nsec
+ .endm
+
/* sec and nsec are modified in place. */
.macro add_ts sec, nsec, ts_sec, ts_nsec, nsec_to_sec
/* Add timespec. */
@@ -135,7 +144,8 @@ ENTRY(__kernel_gettimeofday)
1: seqcnt_acquire
syscall_check fail=4f
ldr x10, [vdso_data, #VDSO_CS_CYCLE_LAST]
- ldp w11, w12, [vdso_data, #VDSO_CS_MULT]
+ /* w11 = cs_mono_mult, w12 = cs_shift */
+ ldp w11, w12, [vdso_data, #VDSO_CS_MONO_MULT]
ldp x13, x14, [vdso_data, #VDSO_XTIME_CLK_SEC]
seqcnt_check fail=1b
@@ -172,20 +182,20 @@ ENDPROC(__kernel_gettimeofday)
/* int __kernel_clock_gettime(clockid_t clock_id, struct timespec *tp); */
ENTRY(__kernel_clock_gettime)
.cfi_startproc
- cmp w0, #JUMPSLOT_MAX
- b.hi syscall
+ cmp w0, #JUMPSLOT_MAX
+ b.hi syscall
adr vdso_data, _vdso_data
- adr x_tmp, jumptable
- add x_tmp, x_tmp, w0, uxtw #2
- br x_tmp
+ adr x_tmp, jumptable
+ add x_tmp, x_tmp, w0, uxtw #2
+ br x_tmp
ALIGN
jumptable:
jump_slot jumptable, CLOCK_REALTIME, realtime
jump_slot jumptable, CLOCK_MONOTONIC, monotonic
- b syscall
- b syscall
- b syscall
+ b syscall
+ b syscall
+ jump_slot jumptable, CLOCK_MONOTONIC_RAW, monotonic_raw
jump_slot jumptable, CLOCK_REALTIME_COARSE, realtime_coarse
jump_slot jumptable, CLOCK_MONOTONIC_COARSE, monotonic_coarse
@@ -198,7 +208,8 @@ realtime:
seqcnt_acquire
syscall_check fail=syscall
ldr x10, [vdso_data, #VDSO_CS_CYCLE_LAST]
- ldp w11, w12, [vdso_data, #VDSO_CS_MULT]
+ /* w11 = cs_mono_mult, w12 = cs_shift */
+ ldp w11, w12, [vdso_data, #VDSO_CS_MONO_MULT]
ldp x13, x14, [vdso_data, #VDSO_XTIME_CLK_SEC]
seqcnt_check fail=realtime
@@ -216,7 +227,8 @@ monotonic:
seqcnt_acquire
syscall_check fail=syscall
ldr x10, [vdso_data, #VDSO_CS_CYCLE_LAST]
- ldp w11, w12, [vdso_data, #VDSO_CS_MULT]
+ /* w11 = cs_mono_mult, w12 = cs_shift */
+ ldp w11, w12, [vdso_data, #VDSO_CS_MONO_MULT]
ldp x13, x14, [vdso_data, #VDSO_XTIME_CLK_SEC]
ldp x3, x4, [vdso_data, #VDSO_WTM_CLK_SEC]
seqcnt_check fail=monotonic
@@ -234,6 +246,28 @@ monotonic:
clock_gettime_return, shift=1
ALIGN
+monotonic_raw:
+ seqcnt_acquire
+ syscall_check fail=syscall
+ ldr x10, [vdso_data, #VDSO_CS_CYCLE_LAST]
+ /* w11 = cs_raw_mult, w12 = cs_shift */
+ ldp w12, w11, [vdso_data, #VDSO_CS_SHIFT]
+ ldp x13, x14, [vdso_data, #VDSO_RAW_TIME_SEC]
+ seqcnt_check fail=monotonic_raw
+
+ /* All computations are done with left-shifted nsecs. */
+ lsl x14, x14, x12
+ get_nsec_per_sec res=x9
+ lsl x9, x9, x12
+
+ get_clock_shifted_nsec res=x15, cycle_last=x10, mult=x11
+ get_ts_clock_raw res_sec=x10, res_nsec=x11, \
+ clock_nsec=x15, nsec_to_sec=x9
+
+ add_ts sec=x10, nsec=x11, ts_sec=x13, ts_nsec=x14, nsec_to_sec=x9
+ clock_gettime_return, shift=1
+
+ ALIGN
realtime_coarse:
seqcnt_acquire
ldp x10, x11, [vdso_data, #VDSO_XTIME_CRS_SEC]
@@ -265,6 +299,7 @@ ENTRY(__kernel_clock_getres)
.cfi_startproc
cmp w0, #CLOCK_REALTIME
ccmp w0, #CLOCK_MONOTONIC, #0x4, ne
+ ccmp w0, #CLOCK_MONOTONIC_RAW, #0x4, ne
b.ne 1f
ldr x2, 5f
--
2.9.0
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