ANDROID: clock_gettime(CLOCK_BOOTTIME,) slows down >20x

clock_gettime(CLOCK_BOOTTIME,) slows down after significant
accumulation of suspend time creating a large offset between it and
CLOCK_MONOTONIC time.  The __iter_div_u64_rem() is only for the usage
of adding a few second+nanosecond times and saving cycles on more
expensive remainder and division operations, but iterates one second
at a time which quickly goes out of scale in CLOCK_BOOTTIME's case
since it was specified as nanoseconds only.

The fix is to split off seconds from the boot time and cap the
nanoseconds so that __iter_div_u64_rem does not iterate.

Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Bug: 72406285
Change-Id: Ia647ef1e76b7ba3b0c003028d4b3b955635adabb

Signed-off-by: starlight5234 <ifist2834@gmail.com>
Conflicts:
	arch/arm64/kernel/vdso.c
Signed-off-by: TheSync <repo-sync@outlook.com>

arch/arm/include/asm/vdso_datapage.h

@@ -64,7 +64,8 @@ struct vdso_data {
 	u32 tz_minuteswest;	/* timezone info for gettimeofday(2) */
 	u32 tz_dsttime;
 
-	u64 btm_nsec;		/* monotonic to boot time */
+	u32 btm_sec;		/* monotonic to boot time */
+	u32 btm_nsec;
 	/* Raw clocksource multipler */
 	u32 cs_raw_mult;
 	/* Raw time */

arch/arm/kernel/vdso.c

@@ -320,6 +320,8 @@ void update_vsyscall(struct timekeeper *tk)
 	vdso_data->wtm_clock_nsec		= wtm->tv_nsec;
 
 	if (!vdso_data->use_syscall) {
+		struct timespec btm = ktime_to_timespec(tk->offs_boot);
+
 		vdso_data->cs_cycle_last	= tk->tkr_mono.cycle_last;
 		vdso_data->raw_time_sec		= tk->raw_sec;
 		vdso_data->raw_time_nsec	= tk->tkr_raw.xtime_nsec;
@@ -330,7 +332,8 @@ void update_vsyscall(struct timekeeper *tk)
 		/* tkr_mono.shift == tkr_raw.shift */
 		vdso_data->cs_shift		= tk->tkr_mono.shift;
 		vdso_data->cs_mask		= tk->tkr_mono.mask;
-		vdso_data->btm_nsec		= ktime_to_ns(tk->offs_boot);
+		vdso_data->btm_sec		= btm.tv_sec;
+		vdso_data->btm_nsec		= btm.tv_nsec;
 	}
 
 	vdso_write_end(vdso_data);

arch/arm64/include/asm/vdso_datapage.h

@@ -45,7 +45,8 @@ struct vdso_data {
 	__u64 xtime_coarse_nsec;
 	__u64 wtm_clock_sec;	/* Wall to monotonic time */
 	vdso_wtm_clock_nsec_t wtm_clock_nsec;
-	__u64 btm_nsec;		/* monotonic to boot time */
+	__u32 btm_sec;		/* monotonic to boot time */
+	__u32 btm_nsec;
 	__u32 tb_seq_count;	/* Timebase sequence counter */
 	/* cs_* members must be adjacent and in this order (ldp accesses) */
 	__u32 cs_mono_mult;	/* NTP-adjusted clocksource multiplier */

arch/arm64/kernel/vdso.c

@@ -337,6 +337,8 @@ void update_vsyscall(struct timekeeper *tk)
 	vdso_data->wtm_clock_nsec		= tk->wall_to_monotonic.tv_nsec;
 
 	if (!use_syscall) {
+		struct timespec btm = ktime_to_timespec(tk->offs_boot);
+
 		/* 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_sec;
@@ -347,7 +349,8 @@ void update_vsyscall(struct timekeeper *tk)
 		vdso_data->cs_raw_mult		= tk->tkr_raw.mult;
 		/* tkr_mono.shift == tkr_raw.shift */
 		vdso_data->cs_shift		= tk->tkr_mono.shift;
-		vdso_data->btm_nsec		= ktime_to_ns(tk->offs_boot);
+		vdso_data->btm_sec		= btm.tv_sec;
+		vdso_data->btm_nsec		= btm.tv_nsec;
 	}
 
 	smp_wmb();

arch/arm64/kernel/vdso32/compiler.h

@@ -23,6 +23,8 @@
 #ifndef __VDSO_COMPILER_H
 #define __VDSO_COMPILER_H
 
+#include <generated/autoconf.h>
+#undef CONFIG_64BIT
 #include <asm/barrier.h>	/* for isb() & dmb()	*/
 #include <asm/param.h>		/* for HZ		*/
 #include <asm/unistd32.h>

lib/vdso/vgettimeofday.c

@@ -252,7 +252,8 @@ static notrace int do_monotonic_raw(const struct vdso_data *vd,
 static notrace int do_boottime(const struct vdso_data *vd, struct timespec *ts)
 {
 	u32 seq, mult, shift;
-	u64 nsec, cycle_last, wtm_nsec;
+	u64 nsec, cycle_last;
+	vdso_wtm_clock_nsec_t wtm_nsec;
 #ifdef ARCH_CLOCK_FIXED_MASK
 	static const u64 mask = ARCH_CLOCK_FIXED_MASK;
 #else
@@ -277,7 +278,7 @@ static notrace int do_boottime(const struct vdso_data *vd, struct timespec *ts)
 		sec = vd->xtime_clock_sec;
 		nsec = vd->xtime_clock_snsec;
 
-		sec += vd->wtm_clock_sec;
+		sec += vd->wtm_clock_sec + vd->btm_sec;
 		wtm_nsec = vd->wtm_clock_nsec + vd->btm_nsec;
 
 	} while (unlikely(vdso_read_retry(vd, seq)));