profile.c

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#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);