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profile.c

#include <linux/init.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/proc_fs.h>
#include <linux/types.h>
#include <asm/ptrace.h>
#include <asm/uaccess.h>

#define SAMPLE_BUFFER_SIZE 8192

static char* sample_buffer;
static char* sample_buffer_pos;
static int prof_running = 0;

void
cris_profile_sample(struct pt_regs* regs)
{
      if (!prof_running)
            return;

      if (user_mode(regs))
            *(unsigned int*)sample_buffer_pos = current->pid;
      else
            *(unsigned int*)sample_buffer_pos = 0;

      *(unsigned int*)(sample_buffer_pos + 4) = instruction_pointer(regs);
      sample_buffer_pos += 8;

      if (sample_buffer_pos == sample_buffer + SAMPLE_BUFFER_SIZE)
            sample_buffer_pos = sample_buffer;
}

static ssize_t
read_cris_profile(struct file *file, char __user *buf,
              size_t count, loff_t *ppos)
{
      unsigned long p = *ppos;

      if (p > SAMPLE_BUFFER_SIZE)
            return 0;

      if (p + count > SAMPLE_BUFFER_SIZE)
            count = SAMPLE_BUFFER_SIZE - p;
      if (copy_to_user(buf, sample_buffer + p,count))
            return -EFAULT;

      memset(sample_buffer + p, 0, count);
      *ppos += count;

      return count;
}

static ssize_t
write_cris_profile(struct file *file, const char __user *buf,
               size_t count, loff_t *ppos)
{
      sample_buffer_pos = sample_buffer;
      memset(sample_buffer, 0, SAMPLE_BUFFER_SIZE);
}

static const struct file_operations cris_proc_profile_operations = {
      .read       = read_cris_profile,
      .write            = write_cris_profile,
};

static int
__init init_cris_profile(void)
{
      struct proc_dir_entry *entry;

      sample_buffer = kmalloc(SAMPLE_BUFFER_SIZE, GFP_KERNEL);
      if (!sample_buffer) {
            return -ENOMEM;
      }

      sample_buffer_pos = sample_buffer;

      entry = create_proc_entry("system_profile", S_IWUSR | S_IRUGO, NULL);
      if (entry) {
            entry->proc_fops = &cris_proc_profile_operations;
            entry->size = SAMPLE_BUFFER_SIZE;
      }
      prof_running = 1;

      return 0;
}

__initcall(init_cris_profile);

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