/*
 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
 *
 */
#include <linux/stacktrace.h>
#include <linux/kallsyms.h>
#include <linux/seq_file.h>
#include <linux/spinlock.h>
#include <linux/uaccess.h>
#include <linux/debugfs.h>
#include <linux/ftrace.h>
#include <linux/module.h>
#include <linux/sysctl.h>
#include <linux/init.h>
#include <linux/fs.h>
#include "trace.h"

#define STACK_TRACE_ENTRIES 500

static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
         { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
static unsigned stack_dump_index[STACK_TRACE_ENTRIES];

static struct stack_trace max_stack_trace = {
        .max_entries            = STACK_TRACE_ENTRIES,
        .entries                = stack_dump_trace,
};

static unsigned long max_stack_size;
static arch_spinlock_t max_stack_lock =
        (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;

static int stack_trace_disabled __read_mostly;
static DEFINE_PER_CPU(int, trace_active);
static DEFINE_MUTEX(stack_sysctl_mutex);

int stack_tracer_enabled;
static int last_stack_tracer_enabled;

static inline void check_stack(void)
{
        unsigned long this_size, flags;
        unsigned long *p, *top, *start;
        int i;

        this_size = ((unsigned long)&this_size) & (THREAD_SIZE-1);
        this_size = THREAD_SIZE - this_size;

        if (this_size <= max_stack_size)
                return;

        /* we do not handle interrupt stacks yet */
        if (!object_is_on_stack(&this_size))
                return;

        local_irq_save(flags);
        arch_spin_lock(&max_stack_lock);

        /* a race could have already updated it */
        if (this_size <= max_stack_size)
                goto out;

        max_stack_size = this_size;

        max_stack_trace.nr_entries      = 0;
        max_stack_trace.skip            = 3;

        save_stack_trace(&max_stack_trace);

        /*
         * Now find where in the stack these are.
         */
        i = 0;
        start = &this_size;
        top = (unsigned long *)
                (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);

        /*
         * Loop through all the entries. One of the entries may
         * for some reason be missed on the stack, so we may
         * have to account for them. If they are all there, this
         * loop will only happen once. This code only takes place
         * on a new max, so it is far from a fast path.
         */
        while (i < max_stack_trace.nr_entries) {
                int found = 0;

                stack_dump_index[i] = this_size;
                p = start;

                for (; p < top && i < max_stack_trace.nr_entries; p++) {
                        if (*p == stack_dump_trace[i]) {
                                this_size = stack_dump_index[i++] =
                                        (top - p) * sizeof(unsigned long);
                                found = 1;
                                /* Start the search from here */
                                start = p + 1;
                        }
                }

                if (!found)
                        i++;
        }

 out:
        arch_spin_unlock(&max_stack_lock);
        local_irq_restore(flags);
}

static void
stack_trace_call(unsigned long ip, unsigned long parent_ip)
{
        int cpu;

        if (unlikely(!ftrace_enabled || stack_trace_disabled))
                return;

        preempt_disable_notrace();

        cpu = raw_smp_processor_id();
        /* no atomic needed, we only modify this variable by this cpu */
        if (per_cpu(trace_active, cpu)++ != 0)
                goto out;

        check_stack();

 out:
        per_cpu(trace_active, cpu)--;
        /* prevent recursion in schedule */
        preempt_enable_notrace();
}

static struct ftrace_ops trace_ops __read_mostly =
{
        .func = stack_trace_call,
};

static ssize_t
stack_max_size_read(struct file *filp, char __user *ubuf,
                    size_t count, loff_t *ppos)
{
        unsigned long *ptr = filp->private_data;
        char buf[64];
        int r;

        r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
        if (r > sizeof(buf))
                r = sizeof(buf);
        return simple_read_from_buffer(ubuf, count, ppos, buf, r);
}

static ssize_t
stack_max_size_write(struct file *filp, const char __user *ubuf,
                     size_t count, loff_t *ppos)
{
        long *ptr = filp->private_data;
        unsigned long val, flags;
        char buf[64];
        int ret;
        int cpu;

        if (count >= sizeof(buf))
                return -EINVAL;

        if (copy_from_user(&buf, ubuf, count))
                return -EFAULT;

        buf[count] = 0;

        ret = strict_strtoul(buf, 10, &val);
        if (ret < 0)
                return ret;

        local_irq_save(flags);

        /*
         * In case we trace inside arch_spin_lock() or after (NMI),
         * we will cause circular lock, so we also need to increase
         * the percpu trace_active here.
         */
        cpu = smp_processor_id();
        per_cpu(trace_active, cpu)++;

        arch_spin_lock(&max_stack_lock);
        *ptr = val;
        arch_spin_unlock(&max_stack_lock);

        per_cpu(trace_active, cpu)--;
        local_irq_restore(flags);

        return count;
}

static const struct file_operations stack_max_size_fops = {
        .open           = tracing_open_generic,
        .read           = stack_max_size_read,
        .write          = stack_max_size_write,
        .llseek         = default_llseek,
};

static void *
__next(struct seq_file *m, loff_t *pos)
{
        long n = *pos - 1;

        if (n >= max_stack_trace.nr_entries || stack_dump_trace[n] == ULONG_MAX)
                return NULL;

        m->private = (void *)n;
        return &m->private;
}

static void *
t_next(struct seq_file *m, void *v, loff_t *pos)
{
        (*pos)++;
        return __next(m, pos);
}

static void *t_start(struct seq_file *m, loff_t *pos)
{
        int cpu;

        local_irq_disable();

        cpu = smp_processor_id();
        per_cpu(trace_active, cpu)++;

        arch_spin_lock(&max_stack_lock);

        if (*pos == 0)
                return SEQ_START_TOKEN;

        return __next(m, pos);
}

static void t_stop(struct seq_file *m, void *p)
{
        int cpu;

        arch_spin_unlock(&max_stack_lock);

        cpu = smp_processor_id();
        per_cpu(trace_active, cpu)--;

        local_irq_enable();
}

static int trace_lookup_stack(struct seq_file *m, long i)
{
        unsigned long addr = stack_dump_trace[i];

        return seq_printf(m, "%pS\n", (void *)addr);
}

static void print_disabled(struct seq_file *m)
{
        seq_puts(m, "#\n"
                 "#  Stack tracer disabled\n"
                 "#\n"
                 "# To enable the stack tracer, either add 'stacktrace' to the\n"
                 "# kernel command line\n"
                 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
                 "#\n");
}

static int t_show(struct seq_file *m, void *v)
{
        long i;
        int size;

        if (v == SEQ_START_TOKEN) {
                seq_printf(m, "        Depth    Size   Location"
                           "    (%d entries)\n"
                           "        -----    ----   --------\n",
                           max_stack_trace.nr_entries - 1);

                if (!stack_tracer_enabled && !max_stack_size)
                        print_disabled(m);

                return 0;
        }

        i = *(long *)v;

        if (i >= max_stack_trace.nr_entries ||
            stack_dump_trace[i] == ULONG_MAX)
                return 0;

        if (i+1 == max_stack_trace.nr_entries ||
            stack_dump_trace[i+1] == ULONG_MAX)
                size = stack_dump_index[i];
        else
                size = stack_dump_index[i] - stack_dump_index[i+1];

        seq_printf(m, "%3ld) %8d   %5d   ", i, stack_dump_index[i], size);

        trace_lookup_stack(m, i);

        return 0;
}

static const struct seq_operations stack_trace_seq_ops = {
        .start          = t_start,
        .next           = t_next,
        .stop           = t_stop,
        .show           = t_show,
};

static int stack_trace_open(struct inode *inode, struct file *file)
{
        return seq_open(file, &stack_trace_seq_ops);
}

static const struct file_operations stack_trace_fops = {
        .open           = stack_trace_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = seq_release,
};

int
stack_trace_sysctl(struct ctl_table *table, int write,
                   void __user *buffer, size_t *lenp,
                   loff_t *ppos)
{
        int ret;

        mutex_lock(&stack_sysctl_mutex);

        ret = proc_dointvec(table, write, buffer, lenp, ppos);

        if (ret || !write ||
            (last_stack_tracer_enabled == !!stack_tracer_enabled))
                goto out;

        last_stack_tracer_enabled = !!stack_tracer_enabled;

        if (stack_tracer_enabled)
                register_ftrace_function(&trace_ops);
        else
                unregister_ftrace_function(&trace_ops);

 out:
        mutex_unlock(&stack_sysctl_mutex);
        return ret;
}

static __init int enable_stacktrace(char *str)
{
        stack_tracer_enabled = 1;
        last_stack_tracer_enabled = 1;
        return 1;
}
__setup("stacktrace", enable_stacktrace);

static __init int stack_trace_init(void)
{
        struct dentry *d_tracer;

        d_tracer = tracing_init_dentry();

        trace_create_file("stack_max_size", 0644, d_tracer,
                        &max_stack_size, &stack_max_size_fops);

        trace_create_file("stack_trace", 0444, d_tracer,
                        NULL, &stack_trace_fops);

        if (stack_tracer_enabled)
                register_ftrace_function(&trace_ops);

        return 0;
}

device_initcall(stack_trace_init);