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KERN_CPTIME2: set ENODEV if the CPU is offline.

This lets userspace distinguish between idle CPUs and those that are
not schedulable because hw.smt=0.

A subsequent commit probably needs to add documentation for this
to sysctl.2 (and perhaps elsewhere) after the dust settles.

Also included here are changes to systat(1) and top(1) that account
for the ENODEV case and adjust behavior accordingly:

 - systat(1)'s cpu view prints placeholder marks ('-') instead of
   percentages for each state if the given CPU is offline.

 - systat(1)'s vmstat view checks for offline CPUs when computing the
   machine state total and excludes them, so the CPU usage graph
   only represents the states for online CPUs.

 - top(1) does not draw CPU rows for offline CPUs when the view is
   redrawn.  If CPUs "go offline", percentages for each state are
   replaced by placeholder marks ('-'); the view will need to be
   redrawn to remove these rows.  If CPUs "go online" the view will
   need to be redrawn to show these new CPUs.  In "combined CPU" mode,
   the count and the state totals only represent online CPUs.

Ports using KERN_CPTIME2 will need to be updated.  The changes
described above to make systat(1) and top(1) aware of the ENODEV
case *and* gracefully handle a changing HW_NCPUONLINE while the
application is running are not necessarily appropriate for each
and every port.

The changes described above are so extensive in part to demonstrate
one way a program *might* be made robust to changing CPU availability.
In particular, changing hw.smt after boot is an extremely rare event,
and this needs to be weighed when updating ports.

The logic needed to account for the KERN_CPTIME2 ENODEV case is
very roughly:

	if (sysctl(...) == -1) {
		if (errno != ENODEV) {
			/* Actual error occurred. */
		} else {
			/* CPU is offline. */
		}
	} else {
		/* CPU is online and CPU states were set by sysctl(2). */
	}

Prompted by deraadt@.  Basic idea for ENODEV from kettenis@.  Discussed at
length with kettenis@.  Additional testing by tb@.

No complaints from hackers@ after a week.

ok kettenis@, "I think you should commit [now]" deraadt@

/*	$OpenBSD: cpu.c,v 1.7 2018/09/26 17:23:13 cheloha Exp $	*/

/*
 * Copyright (c) 2013 Reyk Floeter <reyk@openbsd.org>
 * Copyright (c) 2001, 2007 Can Erkin Acar <canacar@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/* CPU percentages() function from usr.bin/top/util.c:
 *
 *  Top users/processes display for Unix
 *  Version 3
 *
 * Copyright (c) 1984, 1989, William LeFebvre, Rice University
 * Copyright (c) 1989, 1990, 1992, William LeFebvre, Northwestern University
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR OR HIS EMPLOYER BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/signal.h>
#include <sys/sched.h>
#include <sys/sysctl.h>

#include <errno.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <unistd.h>
#include "systat.h"

void		 print_cpu(void);
int		 read_cpu(void);
int		 select_cpu(void);
static void	 cpu_info(void);
static void	 print_fld_percentage(field_def *, double);
static int	 percentages(int, int64_t *, int64_t *, int64_t *, int64_t *);

field_def fields_cpu[] = {
	{ "CPU", 4, 8, 1, FLD_ALIGN_LEFT, -1, 0, 0, 0 },
	{ "User", 10, 20, 1, FLD_ALIGN_RIGHT, -1, 0, 0, 0 },
	{ "Nice", 10, 20, 1, FLD_ALIGN_RIGHT, -1, 0, 0, 0 },
	{ "System", 10, 20, 1, FLD_ALIGN_RIGHT, -1, 0, 0, 0 },
	{ "Spin", 10, 20, 1, FLD_ALIGN_RIGHT, -1, 0, 0, 0 },
	{ "Interrupt", 10, 20, 1, FLD_ALIGN_RIGHT, -1, 0, 0, 0 },
	{ "Idle", 10, 20, 1, FLD_ALIGN_RIGHT, -1, 0, 0, 0 },
};

#define FLD_CPU_CPU	FIELD_ADDR(fields_cpu, 0)
#define FLD_CPU_USR	FIELD_ADDR(fields_cpu, 1)
#define FLD_CPU_NIC	FIELD_ADDR(fields_cpu, 2)
#define FLD_CPU_SYS	FIELD_ADDR(fields_cpu, 3)
#define FLD_CPU_SPIN	FIELD_ADDR(fields_cpu, 4)
#define FLD_CPU_INT	FIELD_ADDR(fields_cpu, 5)
#define FLD_CPU_IDLE	FIELD_ADDR(fields_cpu, 6)

/* Define views */
field_def *view_cpu_0[] = {
	FLD_CPU_CPU, FLD_CPU_USR, FLD_CPU_NIC, FLD_CPU_SYS, FLD_CPU_SPIN,
	FLD_CPU_INT, FLD_CPU_IDLE, NULL
};

/* Define view managers */
struct view_manager cpu_mgr = {
	"cpu", select_cpu, read_cpu, NULL, print_header,
	print_cpu, keyboard_callback, NULL, NULL
};

field_view views_cpu[] = {
	{ view_cpu_0, "cpu", 'C', &cpu_mgr },
	{ NULL, NULL, 0, NULL }
};

int	  cpu_count;
int	 *cpu_online;
int64_t	 *cpu_states;
int64_t	**cpu_tm;
int64_t	**cpu_old;
int64_t	**cpu_diff;

/*
 * percentages(cnt, out, new, old, diffs) - calculate percentage change
 * between array "old" and "new", putting the percentages in "out".
 * "cnt" is size of each array and "diffs" is used for scratch space.
 * The array "old" is updated on each call.
 * The routine assumes modulo arithmetic.  This function is especially
 * useful on BSD machines for calculating cpu state percentages.
 */
static int
percentages(int cnt, int64_t *out, int64_t *new, int64_t *old, int64_t *diffs)
{
	int64_t change, total_change, *dp, half_total;
	int i;

	/* initialization */
	total_change = 0;
	dp = diffs;

	/* calculate changes for each state and the overall change */
	for (i = 0; i < cnt; i++) {
		if ((change = *new - *old) < 0) {
			/* this only happens when the counter wraps */
			change = INT64_MAX - *old + *new;
		}
		total_change += (*dp++ = change);
		*old++ = *new++;
	}

	/* avoid divide by zero potential */
	if (total_change == 0)
		total_change = 1;

	/* calculate percentages based on overall change, rounding up */
	half_total = total_change / 2l;
	for (i = 0; i < cnt; i++)
		*out++ = ((*diffs++ * 1000 + half_total) / total_change);

	/* return the total in case the caller wants to use it */
	return (total_change);
}

static void
cpu_info(void)
{
	int	 cpu_time_mib[] = { CTL_KERN, KERN_CPTIME2, 0 }, i;
	int64_t *tmpstate;
	size_t	 size;

	size = CPUSTATES * sizeof(int64_t);
	for (i = 0; i < cpu_count; i++) {
		cpu_time_mib[2] = i;
		tmpstate = cpu_states + (CPUSTATES * i);
		if (sysctl(cpu_time_mib, 3, cpu_tm[i], &size, NULL, 0) < 0) {
			if (errno != ENODEV)
				error("sysctl KERN_CPTIME2");
			cpu_online[i] = 0;
			continue;
		}
		cpu_online[i] = 1;
		percentages(CPUSTATES, tmpstate, cpu_tm[i],
		    cpu_old[i], cpu_diff[i]);
	}
}

static void
print_fld_percentage(field_def *fld, double val)
{
	if (fld == NULL)
		return;

	tb_start();
	tbprintf(val >= 1000 ? "%4.0f%%" : "%4.1f%%", val / 10.);
	print_fld_tb(fld);
	tb_end();
}

int
select_cpu(void)
{
	return (0);
}

int
read_cpu(void)
{
	cpu_info();
	num_disp = cpu_count;
	return (0);
}

int
initcpu(void)
{
	field_view	*v;
	size_t		 size = sizeof(cpu_count);
	int		 mib[2], i;

	mib[0] = CTL_HW;
	mib[1] = HW_NCPU;
	if (sysctl(mib, 2, &cpu_count, &size, NULL, 0) == -1)
		return (-1);
	if ((cpu_online = calloc(cpu_count, sizeof(*cpu_online))) == NULL)
		return (-1);
	if ((cpu_states = calloc(cpu_count,
	    CPUSTATES * sizeof(int64_t))) == NULL)
		return (-1);
	if ((cpu_tm = calloc(cpu_count, sizeof(int64_t *))) == NULL ||
	    (cpu_old = calloc(cpu_count, sizeof(int64_t *))) == NULL ||
	    (cpu_diff = calloc(cpu_count, sizeof(int64_t *))) == NULL)
		return (-1);
	for (i = 0; i < cpu_count; i++) {
		if ((cpu_tm[i] = calloc(CPUSTATES, sizeof(int64_t))) == NULL ||
		    (cpu_old[i] = calloc(CPUSTATES, sizeof(int64_t))) == NULL ||
		    (cpu_diff[i] = calloc(CPUSTATES, sizeof(int64_t))) == NULL)
			return (-1);
	}

	for (v = views_cpu; v->name != NULL; v++)
		add_view(v);

	read_cpu();

	return(1);
}

#define ADD_EMPTY_LINE \
	do {								\
		if (cur >= dispstart && cur < end) 			\
			end_line();					\
		if (++cur >= end)					\
			return;						\
	} while (0)

#define ADD_LINE_CPU(v, cs) \
	do {								\
		if (cur >= dispstart && cur < end) { 			\
			print_fld_size(FLD_CPU_CPU, (v));		\
			print_fld_percentage(FLD_CPU_USR, (cs[CP_USER]));\
			print_fld_percentage(FLD_CPU_NIC, (cs[CP_NICE]));\
			print_fld_percentage(FLD_CPU_SYS, (cs[CP_SYS]));\
			print_fld_percentage(FLD_CPU_SPIN, (cs[CP_SPIN]));\
			print_fld_percentage(FLD_CPU_INT, (cs[CP_INTR]));\
			print_fld_percentage(FLD_CPU_IDLE, (cs[CP_IDLE]));	\
			end_line();					\
		}							\
		if (++cur >= end)					\
			return;						\
	} while (0)

#define ADD_OFFLINE_CPU(v) do {						\
	if (cur >= dispstart && cur < end) { 				\
		print_fld_size(FLD_CPU_CPU, (v));			\
		print_fld_str(FLD_CPU_USR, "-");			\
		print_fld_str(FLD_CPU_NIC, "-");			\
		print_fld_str(FLD_CPU_SYS, "-");			\
		print_fld_str(FLD_CPU_SPIN, "-");			\
		print_fld_str(FLD_CPU_INT, "-");			\
		print_fld_str(FLD_CPU_IDLE, "-");			\
		end_line();						\
	}								\
	if (++cur >= end)						\
		return;							\
} while (0)

void
print_cpu(void)
{
	int		cur = 0, c, i;
	int		end = dispstart + maxprint;
	int64_t		*states;
	double		value[CPUSTATES];

	if (end > num_disp)
		end = num_disp;

	for (c = 0; c < cpu_count; c++) {
		if (!cpu_online[c]) {
			ADD_OFFLINE_CPU(c);
			continue;
		}
		states = cpu_states + (CPUSTATES * c);

		for (i = 0; i < CPUSTATES; i++)
			value[i] = *states++;

		ADD_LINE_CPU(c, value);
	}

	ADD_EMPTY_LINE;
}