Commit 49eea433 authored by Kevin Brodsky's avatar Kevin Brodsky Committed by Catalin Marinas
Browse files

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: default avatarKevin Brodsky <kevin.brodsky@arm.com>
Reviewed-by: default avatarDave Martin <dave.martin@arm.com>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent b33f491f

arch/arm64/include/asm/vdso_datapage.h

+6 −2
Original line number Diff line number Diff line
@@ -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;

arch/arm64/kernel/asm-offsets.c

+5 −1
Original line number Diff line number Diff line
@@ -77,6 +77,7 @@ 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);
@@ -84,6 +85,8 @@ 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));
@@ -91,7 +94,8 @@ 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));

arch/arm64/kernel/vdso.c

+7 −1
Original line number Diff line number Diff line
@@ -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;

	}

arch/arm64/kernel/vdso/gettimeofday.S

+46 −11
Original line number Diff line number Diff line
@@ -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
@@ -185,7 +195,7 @@ jumptable: 
	jump_slot jumptable, CLOCK_MONOTONIC, monotonic

	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
@@ -233,6 +245,28 @@ monotonic: 
	add_ts sec=x10, nsec=x11, ts_sec=x3, ts_nsec=x4, nsec_to_sec=x9

	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
@@ -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

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