ClabureDB: Classified Bug-Reports Database

  /*
   * 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/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 raw_spinlock_t max_stack_lock =
         (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
 
 static int stack_trace_disabled __read_mostly;
 static DEFINE_PER_CPU(int, trace_active);
 
 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;
 
         raw_local_irq_save(flags);
         __raw_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) {
 
                 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);
                                 /* Start the search from here */
                                 start = p + 1;
                         }
                 }
 
                 i++;
         }
 
  out:
         __raw_spin_unlock(&max_stack_lock);
         raw_local_irq_restore(flags);
}

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

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

        resched = need_resched();
        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 */
        if (resched)
                preempt_enable_no_resched_notrace();
        else
                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;

        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;

        raw_local_irq_save(flags);
        __raw_spin_lock(&max_stack_lock);
        *ptr = val;
        __raw_spin_unlock(&max_stack_lock);
        raw_local_irq_restore(flags);

        return count;
}

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

static void *
t_next(struct seq_file *m, void *v, loff_t *pos)
{
        long i;

        (*pos)++;

        if (v == SEQ_START_TOKEN)
                i = 0;
        else {
                i = *(long *)v;
                i++;
        }

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

        m->private = (void *)i;

        return &m->private;
}

static void *t_start(struct seq_file *m, loff_t *pos)
{
        void *t = SEQ_START_TOKEN;
        loff_t l = 0;

        local_irq_disable();
        __raw_spin_lock(&max_stack_lock);

        if (*pos == 0)
                return SEQ_START_TOKEN;

        for (; t && l < *pos; t = t_next(m, t, &l))
                ;

        return t;
}

static void t_stop(struct seq_file *m, void *p)
{
        __raw_spin_unlock(&max_stack_lock);
        local_irq_enable();
}

static int trace_lookup_stack(struct seq_file *m, long i)
{
        unsigned long addr = stack_dump_trace[i];
#ifdef CONFIG_KALLSYMS
        char str[KSYM_SYMBOL_LEN];

        sprint_symbol(str, addr);

        return seq_printf(m, "%s\n", str);
#else
        return seq_printf(m, "%p\n", (void*)addr);
#endif
}

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);
                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 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)
{
        int ret;

        ret = seq_open(file, &stack_trace_seq_ops);

        return ret;
}

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

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

        d_tracer = tracing_init_dentry();

        entry = debugfs_create_file("stack_max_size", 0644, d_tracer,
                                    &max_stack_size, &stack_max_size_fops);
        if (!entry)
                pr_warning("Could not create debugfs 'stack_max_size' entry\n");

        entry = debugfs_create_file("stack_trace", 0444, d_tracer,
                                    NULL, &stack_trace_fops);
        if (!entry)
                pr_warning("Could not create debugfs 'stack_trace' entry\n");

        register_ftrace_function(&trace_ops);

        return 0;
}

device_initcall(stack_trace_init);