text: #include <linux/init.h>
  #include <linux/errno.h>
  #include <linux/kernel.h>
  #include <linux/proc_fs.h>
  #include <linux/slab.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;
  	ssize_t ret;
  
  	ret = simple_read_from_buffer(buf, count, ppos, sample_buffer,
  						SAMPLE_BUFFER_SIZE);
  	if (ret < 0)
  		return ret;
  
  	memset(sample_buffer + p, 0, ret);
  
  	return ret;
  }
  
  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);
  	return count < SAMPLE_BUFFER_SIZE ? count : SAMPLE_BUFFER_SIZE;
  }
  
  static const struct file_operations cris_proc_profile_operations = {
  	.read		= read_cris_profile,
  	.write		= write_cris_profile,
  	.llseek		= default_llseek,
  };
  
  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 = proc_create("system_profile", S_IWUSR | S_IRUGO, NULL,
  			    &cris_proc_profile_operations);
  	if (entry) {
  		proc_set_size(entry, SAMPLE_BUFFER_SIZE);
  	}
  	prof_running = 1;
  
  	return 0;
  }
  __initcall(init_cris_profile);
  
  