cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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ledtrig-cpu.c (4039B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * ledtrig-cpu.c - LED trigger based on CPU activity
      4 *
      5 * This LED trigger will be registered for first 8 CPUs and named
      6 * as cpu0..cpu7. There's additional trigger called cpu that
      7 * is on when any CPU is active.
      8 *
      9 * If you want support for arbitrary number of CPUs, make it one trigger,
     10 * with additional sysfs file selecting which CPU to watch.
     11 *
     12 * It can be bound to any LED just like other triggers using either a
     13 * board file or via sysfs interface.
     14 *
     15 * An API named ledtrig_cpu is exported for any user, who want to add CPU
     16 * activity indication in their code.
     17 *
     18 * Copyright 2011 Linus Walleij <linus.walleij@linaro.org>
     19 * Copyright 2011 - 2012 Bryan Wu <bryan.wu@canonical.com>
     20 */
     21
     22#include <linux/kernel.h>
     23#include <linux/init.h>
     24#include <linux/slab.h>
     25#include <linux/percpu.h>
     26#include <linux/syscore_ops.h>
     27#include <linux/rwsem.h>
     28#include <linux/cpu.h>
     29#include "../leds.h"
     30
     31#define MAX_NAME_LEN	8
     32
     33struct led_trigger_cpu {
     34	bool is_active;
     35	char name[MAX_NAME_LEN];
     36	struct led_trigger *_trig;
     37};
     38
     39static DEFINE_PER_CPU(struct led_trigger_cpu, cpu_trig);
     40
     41static struct led_trigger *trig_cpu_all;
     42static atomic_t num_active_cpus = ATOMIC_INIT(0);
     43
     44/**
     45 * ledtrig_cpu - emit a CPU event as a trigger
     46 * @ledevt: CPU event to be emitted
     47 *
     48 * Emit a CPU event on a CPU core, which will trigger a
     49 * bound LED to turn on or turn off.
     50 */
     51void ledtrig_cpu(enum cpu_led_event ledevt)
     52{
     53	struct led_trigger_cpu *trig = this_cpu_ptr(&cpu_trig);
     54	bool is_active = trig->is_active;
     55
     56	/* Locate the correct CPU LED */
     57	switch (ledevt) {
     58	case CPU_LED_IDLE_END:
     59	case CPU_LED_START:
     60		/* Will turn the LED on, max brightness */
     61		is_active = true;
     62		break;
     63
     64	case CPU_LED_IDLE_START:
     65	case CPU_LED_STOP:
     66	case CPU_LED_HALTED:
     67		/* Will turn the LED off */
     68		is_active = false;
     69		break;
     70
     71	default:
     72		/* Will leave the LED as it is */
     73		break;
     74	}
     75
     76	if (is_active != trig->is_active) {
     77		unsigned int active_cpus;
     78		unsigned int total_cpus;
     79
     80		/* Update trigger state */
     81		trig->is_active = is_active;
     82		atomic_add(is_active ? 1 : -1, &num_active_cpus);
     83		active_cpus = atomic_read(&num_active_cpus);
     84		total_cpus = num_present_cpus();
     85
     86		led_trigger_event(trig->_trig,
     87			is_active ? LED_FULL : LED_OFF);
     88
     89
     90		led_trigger_event(trig_cpu_all,
     91			DIV_ROUND_UP(LED_FULL * active_cpus, total_cpus));
     92
     93	}
     94}
     95EXPORT_SYMBOL(ledtrig_cpu);
     96
     97static int ledtrig_cpu_syscore_suspend(void)
     98{
     99	ledtrig_cpu(CPU_LED_STOP);
    100	return 0;
    101}
    102
    103static void ledtrig_cpu_syscore_resume(void)
    104{
    105	ledtrig_cpu(CPU_LED_START);
    106}
    107
    108static void ledtrig_cpu_syscore_shutdown(void)
    109{
    110	ledtrig_cpu(CPU_LED_HALTED);
    111}
    112
    113static struct syscore_ops ledtrig_cpu_syscore_ops = {
    114	.shutdown	= ledtrig_cpu_syscore_shutdown,
    115	.suspend	= ledtrig_cpu_syscore_suspend,
    116	.resume		= ledtrig_cpu_syscore_resume,
    117};
    118
    119static int ledtrig_online_cpu(unsigned int cpu)
    120{
    121	ledtrig_cpu(CPU_LED_START);
    122	return 0;
    123}
    124
    125static int ledtrig_prepare_down_cpu(unsigned int cpu)
    126{
    127	ledtrig_cpu(CPU_LED_STOP);
    128	return 0;
    129}
    130
    131static int __init ledtrig_cpu_init(void)
    132{
    133	int cpu;
    134	int ret;
    135
    136	/* Supports up to 9999 cpu cores */
    137	BUILD_BUG_ON(CONFIG_NR_CPUS > 9999);
    138
    139	/*
    140	 * Registering a trigger for all CPUs.
    141	 */
    142	led_trigger_register_simple("cpu", &trig_cpu_all);
    143
    144	/*
    145	 * Registering CPU led trigger for each CPU core here
    146	 * ignores CPU hotplug, but after this CPU hotplug works
    147	 * fine with this trigger.
    148	 */
    149	for_each_possible_cpu(cpu) {
    150		struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);
    151
    152		if (cpu >= 8)
    153			continue;
    154
    155		snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);
    156
    157		led_trigger_register_simple(trig->name, &trig->_trig);
    158	}
    159
    160	register_syscore_ops(&ledtrig_cpu_syscore_ops);
    161
    162	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "leds/trigger:starting",
    163				ledtrig_online_cpu, ledtrig_prepare_down_cpu);
    164	if (ret < 0)
    165		pr_err("CPU hotplug notifier for ledtrig-cpu could not be registered: %d\n",
    166		       ret);
    167
    168	pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n");
    169
    170	return 0;
    171}
    172device_initcall(ledtrig_cpu_init);