vgettimeofday.c

/*
 * Copyright 2012 Tilera Corporation. All Rights Reserved.
 *
 *   This program is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU General Public License
 *   as published by the Free Software Foundation, version 2.
 *
 *   This program is distributed in the hope that it will be useful, but
 *   WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 *   NON INFRINGEMENT.  See the GNU General Public License for
 *   more details.
 */

#define VDSO_BUILD  /* avoid some shift warnings for -m32 in <asm/page.h> */
#include <linux/time.h>
#include <asm/timex.h>
#include <asm/unistd.h>
#include <asm/vdso.h>

#if CHIP_HAS_SPLIT_CYCLE()
static inline cycles_t get_cycles_inline(void)
{
	unsigned int high = __insn_mfspr(SPR_CYCLE_HIGH);
	unsigned int low = __insn_mfspr(SPR_CYCLE_LOW);
	unsigned int high2 = __insn_mfspr(SPR_CYCLE_HIGH);

	while (unlikely(high != high2)) {
		low = __insn_mfspr(SPR_CYCLE_LOW);
		high = high2;
		high2 = __insn_mfspr(SPR_CYCLE_HIGH);
	}

	return (((cycles_t)high) << 32) | low;
}
#define get_cycles get_cycles_inline
#endif

struct syscall_return_value {
	long value;
	long error;
};

/*
 * Find out the vDSO data page address in the process address space.
 */
inline unsigned long get_datapage(void)
{
	unsigned long ret;

	/* vdso data page located in the 2nd vDSO page. */
	asm volatile ("lnk %0" : "=r"(ret));
	ret &= ~(PAGE_SIZE - 1);
	ret += PAGE_SIZE;

	return ret;
}

static inline u64 vgetsns(struct vdso_data *vdso)
{
	return ((get_cycles() - vdso->cycle_last) & vdso->mask) * vdso->mult;
}

static inline int do_realtime(struct vdso_data *vdso, struct timespec *ts)
{
	unsigned count;
	u64 ns;

	do {
		count = raw_read_seqcount_begin(&vdso->tb_seq);
		ts->tv_sec = vdso->wall_time_sec;
		ns = vdso->wall_time_snsec;
		ns += vgetsns(vdso);
		ns >>= vdso->shift;
	} while (unlikely(read_seqcount_retry(&vdso->tb_seq, count)));

	ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
	ts->tv_nsec = ns;

	return 0;
}

static inline int do_monotonic(struct vdso_data *vdso, struct timespec *ts)
{
	unsigned count;
	u64 ns;

	do {
		count = raw_read_seqcount_begin(&vdso->tb_seq);
		ts->tv_sec = vdso->monotonic_time_sec;
		ns = vdso->monotonic_time_snsec;
		ns += vgetsns(vdso);
		ns >>= vdso->shift;
	} while (unlikely(read_seqcount_retry(&vdso->tb_seq, count)));

	ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
	ts->tv_nsec = ns;

	return 0;
}

static inline int do_realtime_coarse(struct vdso_data *vdso,
				     struct timespec *ts)
{
	unsigned count;

	do {
		count = raw_read_seqcount_begin(&vdso->tb_seq);
		ts->tv_sec = vdso->wall_time_coarse_sec;
		ts->tv_nsec = vdso->wall_time_coarse_nsec;
	} while (unlikely(read_seqcount_retry(&vdso->tb_seq, count)));

	return 0;
}

static inline int do_monotonic_coarse(struct vdso_data *vdso,
				      struct timespec *ts)
{
	unsigned count;

	do {
		count = raw_read_seqcount_begin(&vdso->tb_seq);
		ts->tv_sec = vdso->monotonic_time_coarse_sec;
		ts->tv_nsec = vdso->monotonic_time_coarse_nsec;
	} while (unlikely(read_seqcount_retry(&vdso->tb_seq, count)));

	return 0;
}

struct syscall_return_value __vdso_gettimeofday(struct timeval *tv,
						struct timezone *tz)
{
	struct syscall_return_value ret = { 0, 0 };
	unsigned count;
	struct vdso_data *vdso = (struct vdso_data *)get_datapage();

	/* The use of the timezone is obsolete, normally tz is NULL. */
	if (unlikely(tz != NULL)) {
		do {
			count = raw_read_seqcount_begin(&vdso->tz_seq);
			tz->tz_minuteswest = vdso->tz_minuteswest;
			tz->tz_dsttime = vdso->tz_dsttime;
		} while (unlikely(read_seqcount_retry(&vdso->tz_seq, count)));
	}

	if (unlikely(tv == NULL))
		return ret;

	do_realtime(vdso, (struct timespec *)tv);
	tv->tv_usec /= 1000;

	return ret;
}

int gettimeofday(struct timeval *tv, struct timezone *tz)
	__attribute__((weak, alias("__vdso_gettimeofday")));

static struct syscall_return_value vdso_fallback_gettime(long clock,
							 struct timespec *ts)
{
	struct syscall_return_value ret;
	__asm__ __volatile__ (
		"swint1"
		: "=R00" (ret.value), "=R01" (ret.error)
		: "R10" (__NR_clock_gettime), "R00" (clock), "R01" (ts)
		: "r2", "r3", "r4", "r5", "r6", "r7",
		"r8",  "r9", "r11", "r12", "r13", "r14", "r15",
		"r16", "r17", "r18", "r19", "r20", "r21", "r22", "r23",
		"r24", "r25", "r26", "r27", "r28", "r29", "memory");
	return ret;
}

struct syscall_return_value __vdso_clock_gettime(clockid_t clock,
						 struct timespec *ts)
{
	struct vdso_data *vdso = (struct vdso_data *)get_datapage();
	struct syscall_return_value ret = { 0, 0 };

	switch (clock) {
	case CLOCK_REALTIME:
		do_realtime(vdso, ts);
		return ret;
	case CLOCK_MONOTONIC:
		do_monotonic(vdso, ts);
		return ret;
	case CLOCK_REALTIME_COARSE:
		do_realtime_coarse(vdso, ts);
		return ret;
	case CLOCK_MONOTONIC_COARSE:
		do_monotonic_coarse(vdso, ts);
		return ret;
	default:
		return vdso_fallback_gettime(clock, ts);
	}
}

int clock_gettime(clockid_t clock, struct timespec *ts)
	__attribute__((weak, alias("__vdso_clock_gettime")));