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C/C++, Python, CUDA, Android, Linux kernel, Network, etc.

カーネルモジュールのサンプル

Linux

LinuxのCharacter deviceのひな形。最近はprintkではなく、pr_xxxを使うらしい。

まずMakefile。

KDIR = /lib/modules/$(shell uname -r)/build
obj-m += sample.o

all:
  make -C $(KDIR) M=$(PWD)

clean:
  make -C $(KDIR) M=$(PWD) clean

Character deviceを作るsample.c。

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/slab.h>

#define DEV_NAME "sample"

struct sample_dev_t
{
    dev_t id;
    struct cdev cdev;
    struct class *class;
    struct device *dev;
} *sample_dev;

static int sample_open(struct inode *inode, struct file *filp)
{
    pr_info("open\n");
    return 0;
}

static int sample_close(struct inode *inode, struct file * filp)
{
    pr_info("close\n");
    return 0;
}

static ssize_t sample_read(struct file *filp, char __user *buf,
                size_t size, loff_t *offset)
{
    pr_info("read\n");
    return 0;
}

static ssize_t sample_write(struct file *filp, const char __user *buf,
                size_t size, loff_t *offset)
{
    pr_info("write\n");
    return 0;
}

static long sample_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
    pr_info("ioctl cmd %d arg %ld\n", cmd, arg);
    return 0;
}

struct file_operations sample_fops = {
    .owner          = THIS_MODULE,
    .open           = sample_open,
    .release        = sample_close,
    .read           = sample_read,
    .write          = sample_write,
    .unlocked_ioctl = sample_ioctl,
};

static int __init sample_init(void)
{
    int err;

    pr_info("%s:init\n", DEV_NAME);

    sample_dev = kmalloc(sizeof(struct sample_dev_t), GFP_KERNEL);
    if (!sample_dev) {
        pr_err("kmalloc err\n");
        return -ENOMEM;
    }

    err = alloc_chrdev_region(&sample_dev->id, 0, 1, DEV_NAME);
    if (err) {
        pr_err("alloc_chrdev_region err %d\n", err);
        goto out_free;
    }

    cdev_init(&sample_dev->cdev, &sample_fops);
    sample_dev->cdev.owner = THIS_MODULE;

    err = cdev_add(&sample_dev->cdev, sample_dev->id, 1);
    if (err) {
        pr_err("cdev_add err %d\n", err);
        goto out_unregister;
    }

    sample_dev->class = class_create(THIS_MODULE, DEV_NAME);
    if (IS_ERR(sample_dev->class)) {
        err = PTR_ERR(sample_dev->class);
        pr_err("class_create err %d\n", err);
        goto out_cdev_del;
    }

    sample_dev->dev = device_create(sample_dev->class, NULL,
            sample_dev->id, NULL, DEV_NAME);
    if (IS_ERR(sample_dev->dev)) {
        err = PTR_ERR(sample_dev->dev);
        pr_err("device_create err %d\n", err);
        goto out_class_destroy;
    }

    return 0;

out_class_destroy:
    class_destroy(sample_dev->class);

out_cdev_del:
    cdev_del(&sample_dev->cdev);

out_unregister:
    unregister_chrdev_region(sample_dev->id, 1);

out_free:
    kfree(sample_dev);

    return err;
}

static void __exit sample_exit(void)
{
    pr_info("exit\n");

    device_destroy(sample_dev->class, sample_dev->id);
    class_destroy(sample_dev->class);
    cdev_del(&sample_dev->cdev);
    unregister_chrdev_region(sample_dev->id, 1);
    kfree(sample_dev);
}

module_init(sample_init);
module_exit(sample_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("kernel module sample");

試しに /dev/sample をcatする。

sudo insmod ./sample.ko
sudo cat /dev/sample

syslogに以下のログが出る。

Mar 24 22:31:18 0805LM kernel: [12515.692818] sample:init
Mar 24 22:31:30 0805LM kernel: [12527.303679] open
Mar 24 22:31:30 0805LM kernel: [12527.303690] read
Mar 24 22:31:30 0805LM kernel: [12527.303692] close

Pythonで数値−色変換とPNGの書き出し

Python

ヒートマップのようなものを作るとき用に調べた。

[0, 1]の範囲の値を青ー赤のカラーに変換
http://qiita.com/krsak/items/94fad1d3fffa997cb651

PNGの書き出し
http://danpansa.blog.jp/archives/12901916.html

#!/usr/bin/env python

import math
import Image

def colorscale(v):
    t = math.cos(4 * math.pi * v)
    c = int(((-t / 2) + 0.5) * 255)
    if v >= 1.0:
        return (255, 0, 0)
    elif v >= 0.75:
        return (255, c, 0)
    elif v >= 0.5:
        return (c, 255, 0)
    elif v >= 0.25:
        return (0, 255, c)
    elif v >= 0:
        return (0, c, 255)
    else:
        return (0, 0, 255)


if __name__ == '__main__':
    img = Image.new('RGB', (100, 100), 'white')
    pix = img.load()

    for x in range(100):
        (r, g, b) = colorscale(x / 100.0)
        for y in range(100):
            pix[x, y] = (r, g, b)

    img.save('out.png')

生成したPNG

f:id:trisection:20140315235149p:plain