// SPDX-License-Identifier: GPL-2.0
#include <linux/kernel.h>
#include <linux/smp.h>
#include <linux/reboot.h>
#include <linux/kexec.h>
#include <linux/memblock.h>
#include <linux/crash_dump.h>
#include <linux/delay.h>
#include <linux/irq.h>
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>

/* This keeps a track of which one is crashing cpu. */
static int crashing_cpu = -1;
static cpumask_t cpus_in_crash = CPU_MASK_NONE;

#ifdef CONFIG_SMP
static void crash_shutdown_secondary(void *passed_regs)
{
        struct pt_regs *regs = passed_regs;
        int cpu = smp_processor_id();

        /*
         * If we are passed registers, use those.  Otherwise get the
         * regs from the last interrupt, which should be correct, as
         * we are in an interrupt.  But if the regs are not there,
         * pull them from the top of the stack.  They are probably
         * wrong, but we need something to keep from crashing again.
         */
        if (!regs)
                regs = get_irq_regs();
        if (!regs)
                regs = task_pt_regs(current);

        if (!cpu_online(cpu))
                return;

        /* We won't be sent IPIs any more. */
        set_cpu_online(cpu, false);

        local_irq_disable();
        if (!cpumask_test_cpu(cpu, &cpus_in_crash))
                crash_save_cpu(regs, cpu);
        cpumask_set_cpu(cpu, &cpus_in_crash);

        while (!atomic_read(&kexec_ready_to_reboot))
                cpu_relax();

        kexec_reboot();

        /* NOTREACHED */
}

static void crash_kexec_prepare_cpus(void)
{
        static int cpus_stopped;
        unsigned int msecs;
        unsigned int ncpus;

        if (cpus_stopped)
                return;

        ncpus = num_online_cpus() - 1;/* Excluding the panic cpu */

        smp_call_function(crash_shutdown_secondary, NULL, 0);
        smp_wmb();

        /*
         * The crash CPU sends an IPI and wait for other CPUs to
         * respond. Delay of at least 10 seconds.
         */
        pr_emerg("Sending IPI to other cpus...\n");
        msecs = 10000;
        while ((cpumask_weight(&cpus_in_crash) < ncpus) && (--msecs > 0)) {
                cpu_relax();
                mdelay(1);
        }

        cpus_stopped = 1;
}

/* Override the weak function in kernel/panic.c */
void crash_smp_send_stop(void)
{
        if (_crash_smp_send_stop)
                _crash_smp_send_stop();

        crash_kexec_prepare_cpus();
}

#else /* !defined(CONFIG_SMP)  */
static void crash_kexec_prepare_cpus(void) {}
#endif /* !defined(CONFIG_SMP)  */

void default_machine_crash_shutdown(struct pt_regs *regs)
{
        local_irq_disable();
        crashing_cpu = smp_processor_id();
        crash_save_cpu(regs, crashing_cpu);
        crash_kexec_prepare_cpus();
        cpumask_set_cpu(crashing_cpu, &cpus_in_crash);
}