/*
 *  HW NMI watchdog support
 *
 *  started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
 *
 *  Arch specific calls to support NMI watchdog
 *
 *  Bits copied from original nmi.c file
 *
 */
#include <asm/apic.h>
#include <asm/nmi.h>

#include <linux/cpumask.h>
#include <linux/kdebug.h>
#include <linux/notifier.h>
#include <linux/kprobes.h>
#include <linux/nmi.h>
#include <linux/cpu.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/seq_buf.h>

#ifdef CONFIG_HARDLOCKUP_DETECTOR
u64 hw_nmi_get_sample_period(int watchdog_thresh)
{
        return (u64)(cpu_khz) * 1000 * watchdog_thresh;
}
#endif

#ifdef arch_trigger_all_cpu_backtrace
/* For reliability, we're prepared to waste bits here. */
static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
static cpumask_t printtrace_mask;

#define NMI_BUF_SIZE            8192

struct nmi_seq_buf {
        unsigned char           buffer[NMI_BUF_SIZE];
        struct seq_buf          seq;
};

/* Safe printing in NMI context */
static DEFINE_PER_CPU(struct nmi_seq_buf, nmi_print_seq);

/* "in progress" flag of arch_trigger_all_cpu_backtrace */
static unsigned long backtrace_flag;

static void print_seq_line(struct nmi_seq_buf *s, int start, int end)
{
        const char *buf = s->buffer + start;

        printk("%.*s", (end - start) + 1, buf);
}

void arch_trigger_all_cpu_backtrace(bool include_self)
{
        struct nmi_seq_buf *s;
        int len;
        int cpu;
        int i;
        int this_cpu = get_cpu();

        if (test_and_set_bit(0, &backtrace_flag)) {
                /*
                 * If there is already a trigger_all_cpu_backtrace() in progress
                 * (backtrace_flag == 1), don't output double cpu dump infos.
                 */
                put_cpu();
                return;
        }

        cpumask_copy(to_cpumask(backtrace_mask), cpu_online_mask);
        if (!include_self)
                cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask));

        cpumask_copy(&printtrace_mask, to_cpumask(backtrace_mask));
        /*
         * Set up per_cpu seq_buf buffers that the NMIs running on the other
         * CPUs will write to.
         */
        for_each_cpu(cpu, to_cpumask(backtrace_mask)) {
                s = &per_cpu(nmi_print_seq, cpu);
                seq_buf_init(&s->seq, s->buffer, NMI_BUF_SIZE);
        }

        if (!cpumask_empty(to_cpumask(backtrace_mask))) {
                pr_info("sending NMI to %s CPUs:\n",
                        (include_self ? "all" : "other"));
                apic->send_IPI_mask(to_cpumask(backtrace_mask), NMI_VECTOR);
        }

        /* Wait for up to 10 seconds for all CPUs to do the backtrace */
        for (i = 0; i < 10 * 1000; i++) {
                if (cpumask_empty(to_cpumask(backtrace_mask)))
                        break;
                mdelay(1);
                touch_softlockup_watchdog();
        }

        /*
         * Now that all the NMIs have triggered, we can dump out their
         * back traces safely to the console.
         */
        for_each_cpu(cpu, &printtrace_mask) {
                int last_i = 0;

                s = &per_cpu(nmi_print_seq, cpu);
                len = seq_buf_used(&s->seq);
                if (!len)
                        continue;

                /* Print line by line. */
                for (i = 0; i < len; i++) {
                        if (s->buffer[i] == '\n') {
                                print_seq_line(s, last_i, i);
                                last_i = i + 1;
                        }
                }
                /* Check if there was a partial line. */
                if (last_i < len) {
                        print_seq_line(s, last_i, len - 1);
                        pr_cont("\n");
                }
        }

        clear_bit(0, &backtrace_flag);
        smp_mb__after_atomic();
        put_cpu();
}

/*
 * It is not safe to call printk() directly from NMI handlers.
 * It may be fine if the NMI detected a lock up and we have no choice
 * but to do so, but doing a NMI on all other CPUs to get a back trace
 * can be done with a sysrq-l. We don't want that to lock up, which
 * can happen if the NMI interrupts a printk in progress.
 *
 * Instead, we redirect the vprintk() to this nmi_vprintk() that writes
 * the content into a per cpu seq_buf buffer. Then when the NMIs are
 * all done, we can safely dump the contents of the seq_buf to a printk()
 * from a non NMI context.
 */
static int nmi_vprintk(const char *fmt, va_list args)
{
        struct nmi_seq_buf *s = this_cpu_ptr(&nmi_print_seq);
        unsigned int len = seq_buf_used(&s->seq);

        seq_buf_vprintf(&s->seq, fmt, args);
        return seq_buf_used(&s->seq) - len;
}

static int __kprobes
arch_trigger_all_cpu_backtrace_handler(unsigned int cmd, struct pt_regs *regs)
{
        int cpu;

        cpu = smp_processor_id();

        if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
                printk_func_t printk_func_save = this_cpu_read(printk_func);

                /* Replace printk to write into the NMI seq */
                this_cpu_write(printk_func, nmi_vprintk);
                if (regs && cpu_in_idle(instruction_pointer(regs))) {
                        pr_warn("NMI backtrace for cpu %d skipped: idling at pc %#lx\n",
                                cpu, instruction_pointer(regs));
                } else {
                        printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu);
                        show_regs(regs);
                }
                this_cpu_write(printk_func, printk_func_save);

                cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
                return NMI_HANDLED;
        }

        return NMI_DONE;
}

static int __init register_trigger_all_cpu_backtrace(void)
{
        register_nmi_handler(NMI_LOCAL, arch_trigger_all_cpu_backtrace_handler,
                                0, "arch_bt");
        return 0;
}
early_initcall(register_trigger_all_cpu_backtrace);
#endif