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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/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) {
            entry->size = SAMPLE_BUFFER_SIZE;
      }
      prof_running = 1;

      return 0;
}
__initcall(init_cris_profile);


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