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>

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 */
+	/* cs_* members must be adjacent and in this order (ldp accesses) */
-	__u32 cs_shift;		/* Clocksource shift */
+	__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

@@ -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

@@ -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

@@ -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
+	cmp	w0, #JUMPSLOT_MAX
-	b.hi 	syscall
+	b.hi	syscall
 	adr	vdso_data, _vdso_data
-	adr 	x_tmp, jumptable
+	adr	x_tmp, jumptable
-	add 	x_tmp, x_tmp, w0, uxtw #2
+	add	x_tmp, x_tmp, w0, uxtw #2
-	br 	x_tmp
+	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
@@ -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