// SPDX-License-Identifier: GPL-2.0

#define _GNU_SOURCE
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <sched.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <locale.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/wait.h>

#include <bpf/bpf.h>
#include <bpf/libbpf.h>

static int cstate_map_fd, pstate_map_fd;

#define MAX_CPU			8
#define MAX_PSTATE_ENTRIES	5
#define MAX_CSTATE_ENTRIES	3
#define MAX_STARS		40

#define CPUFREQ_MAX_SYSFS_PATH	"/sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq"
#define CPUFREQ_LOWEST_FREQ	"208000"
#define CPUFREQ_HIGHEST_FREQ	"12000000"

struct cpu_stat_data {
	unsigned long cstate[MAX_CSTATE_ENTRIES];
	unsigned long pstate[MAX_PSTATE_ENTRIES];
};

static struct cpu_stat_data stat_data[MAX_CPU];

static void cpu_stat_print(void)
{
	int i, j;
	char state_str[sizeof("cstate-9")];
	struct cpu_stat_data *data;

	/* Clear screen */
	printf("\033[2J");

	/* Header */
	printf("\nCPU states statistics:\n");
	printf("%-10s ", "state(ms)");

	for (i = 0; i < MAX_CSTATE_ENTRIES; i++) {
		sprintf(state_str, "cstate-%d", i);
		printf("%-11s ", state_str);
	}

	for (i = 0; i < MAX_PSTATE_ENTRIES; i++) {
		sprintf(state_str, "pstate-%d", i);
		printf("%-11s ", state_str);
	}

	printf("\n");

	for (j = 0; j < MAX_CPU; j++) {
		data = &stat_data[j];

		printf("CPU-%-6d ", j);
		for (i = 0; i < MAX_CSTATE_ENTRIES; i++)
			printf("%-11ld ", data->cstate[i] / 1000000);

		for (i = 0; i < MAX_PSTATE_ENTRIES; i++)
			printf("%-11ld ", data->pstate[i] / 1000000);

		printf("\n");
	}
}

static void cpu_stat_update(int cstate_fd, int pstate_fd)
{
	unsigned long key, value;
	int c, i;

	for (c = 0; c < MAX_CPU; c++) {
		for (i = 0; i < MAX_CSTATE_ENTRIES; i++) {
			key = c * MAX_CSTATE_ENTRIES + i;
			bpf_map_lookup_elem(cstate_fd, &key, &value);
			stat_data[c].cstate[i] = value;
		}

		for (i = 0; i < MAX_PSTATE_ENTRIES; i++) {
			key = c * MAX_PSTATE_ENTRIES + i;
			bpf_map_lookup_elem(pstate_fd, &key, &value);
			stat_data[c].pstate[i] = value;
		}
	}
}

/*
 * This function is copied from 'idlestat' tool function
 * idlestat_wake_all() in idlestate.c.
 *
 * It sets the self running task affinity to cpus one by one so can wake up
 * the specific CPU to handle scheduling; this results in all cpus can be
 * waken up once and produce ftrace event 'trace_cpu_idle'.
 */
static int cpu_stat_inject_cpu_idle_event(void)
{
	int rcpu, i, ret;
	cpu_set_t cpumask;
	cpu_set_t original_cpumask;

	ret = sysconf(_SC_NPROCESSORS_CONF);
	if (ret < 0)
		return -1;

	rcpu = sched_getcpu();
	if (rcpu < 0)
		return -1;

	/* Keep track of the CPUs we will run on */
	sched_getaffinity(0, sizeof(original_cpumask), &original_cpumask);

	for (i = 0; i < ret; i++) {

		/* Pointless to wake up ourself */
		if (i == rcpu)
			continue;

		/* Pointless to wake CPUs we will not run on */
		if (!CPU_ISSET(i, &original_cpumask))
			continue;

		CPU_ZERO(&cpumask);
		CPU_SET(i, &cpumask);

		sched_setaffinity(0, sizeof(cpumask), &cpumask);
	}

	/* Enable all the CPUs of the original mask */
	sched_setaffinity(0, sizeof(original_cpumask), &original_cpumask);
	return 0;
}

/*
 * It's possible to have no any frequency change for long time and cannot
 * get ftrace event 'trace_cpu_frequency' for long period, this introduces
 * big deviation for pstate statistics.
 *
 * To solve this issue, below code forces to set 'scaling_max_freq' to 208MHz
 * for triggering ftrace event 'trace_cpu_frequency' and then recovery back to
 * the maximum frequency value 1.2GHz.
 */
static int cpu_stat_inject_cpu_frequency_event(void)
{
	int len, fd;

	fd = open(CPUFREQ_MAX_SYSFS_PATH, O_WRONLY);
	if (fd < 0) {
		printf("failed to open scaling_max_freq, errno=%d\n", errno);
		return fd;
	}

	len = write(fd, CPUFREQ_LOWEST_FREQ, strlen(CPUFREQ_LOWEST_FREQ));
	if (len < 0) {
		printf("failed to open scaling_max_freq, errno=%d\n", errno);
		goto err;
	}

	len = write(fd, CPUFREQ_HIGHEST_FREQ, strlen(CPUFREQ_HIGHEST_FREQ));
	if (len < 0) {
		printf("failed to open scaling_max_freq, errno=%d\n", errno);
		goto err;
	}

err:
	close(fd);
	return len;
}

static void int_exit(int sig)
{
	cpu_stat_inject_cpu_idle_event();
	cpu_stat_inject_cpu_frequency_event();
	cpu_stat_update(cstate_map_fd, pstate_map_fd);
	cpu_stat_print();
	exit(0);
}

int main(int argc, char **argv)
{
	struct bpf_link *link = NULL;
	struct bpf_program *prog;
	struct bpf_object *obj;
	char filename[256];
	int ret;

	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
	obj = bpf_object__open_file(filename, NULL);
	if (libbpf_get_error(obj)) {
		fprintf(stderr, "ERROR: opening BPF object file failed\n");
		return 0;
	}

	prog = bpf_object__find_program_by_name(obj, "bpf_prog1");
	if (!prog) {
		printf("finding a prog in obj file failed\n");
		goto cleanup;
	}

	/* load BPF program */
	if (bpf_object__load(obj)) {
		fprintf(stderr, "ERROR: loading BPF object file failed\n");
		goto cleanup;
	}

	cstate_map_fd = bpf_object__find_map_fd_by_name(obj, "cstate_duration");
	pstate_map_fd = bpf_object__find_map_fd_by_name(obj, "pstate_duration");
	if (cstate_map_fd < 0 || pstate_map_fd < 0) {
		fprintf(stderr, "ERROR: finding a map in obj file failed\n");
		goto cleanup;
	}

	link = bpf_program__attach(prog);
	if (libbpf_get_error(link)) {
		fprintf(stderr, "ERROR: bpf_program__attach failed\n");
		link = NULL;
		goto cleanup;
	}

	ret = cpu_stat_inject_cpu_idle_event();
	if (ret < 0)
		return 1;

	ret = cpu_stat_inject_cpu_frequency_event();
	if (ret < 0)
		return 1;

	signal(SIGINT, int_exit);
	signal(SIGTERM, int_exit);

	while (1) {
		cpu_stat_update(cstate_map_fd, pstate_map_fd);
		cpu_stat_print();
		sleep(5);
	}

cleanup:
	bpf_link__destroy(link);
	bpf_object__close(obj);
	return 0;
}