add: procfs で実装。 read(2) に対応しています。

linux-kernel-procfs-module/Makefile

@@ -0,0 +1,10 @@
+obj-m := sekigae.o
+
+KDIR := /lib/modules/$(shell uname -r)/build
+PWD := $(shell pwd)
+
+all:
+	$(MAKE) -C $(KDIR) SUBDIRS=$(PWD) modules
+
+clean:
+	rm -rf *.o *.ko *.mod.c *~

linux-kernel-procfs-module/sample.md

@@ -0,0 +1,25 @@
+## Build 
+
+```
+$ make 
+$ sudo insmod sekigae.ko
+```
+
+## Usage 
+
+```
+$ ls -hal /proc/sekigae
+-rw-r--r-- 1 root root 0  5月 24 18:51 2013 /proc/sekigae
+
+$ cat /proc/sekigae
+kitak
+keoken
+gussan
+okkun
+
+$ cat /proc/sekigae
+kitak
+keoken
+okkun
+gussan
+```

linux-kernel-procfs-module/sekigae.c

@@ -0,0 +1,78 @@
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/proc_fs.h>
+#include <linux/random.h>
+
+MODULE_DESCRIPTION("Sekigae Module");
+MODULE_AUTHOR("Sekigae");
+MODULE_LICENSE("SUSHI");
+
+#define PROCFS_ENTRY "sekigae"
+
+static struct proc_dir_entry *sekigae_proc_dir_entry = NULL;
+
+static int
+procfile_read(char *buffer,
+          char **buffer_location,
+          off_t offset, int buffer_length, int *eof, void *data)
+{
+    int ret = 0;
+    int length = 0;
+    int i;
+
+    const char *newcomers[] = {
+        "okkun",
+        "keoken",
+        "kitak",
+        "gussan",
+    };
+
+    unsigned int members_count = sizeof(newcomers) / sizeof(char *);
+    for (i = 0; i < members_count; i++) {
+        const char *swapped;
+        unsigned int r;
+        get_random_bytes(&r, sizeof r);
+        r = r % members_count;
+        swapped      = newcomers[r];
+        newcomers[r] = newcomers[i];
+        newcomers[i] = swapped;
+    }
+
+    for (i = 0; i < members_count; i++) {
+        length += sprintf(buffer + length, "%s\n", newcomers[i]);
+    }
+
+    if (length > buffer_length) {
+      ret = -ENOMEM;
+    } else {
+      ret = length;
+    }
+
+    return ret;
+}
+
+static int sekigae_init_module(void)
+{
+    sekigae_proc_dir_entry = create_proc_entry(PROCFS_ENTRY, 0644, NULL);
+    if( sekigae_proc_dir_entry == NULL ) {
+        remove_proc_entry(PROCFS_ENTRY, NULL);
+        printk(KERN_ALERT "Error: Could not initialize /proc/%s\n",
+               PROCFS_ENTRY);
+        return -ENOMEM;
+    }
+
+    sekigae_proc_dir_entry->read_proc = procfile_read;
+    sekigae_proc_dir_entry->uid       = 0;
+    sekigae_proc_dir_entry->gid       = 0;
+
+    return 0;
+}
+
+static void sekigae_cleanup_module(void)
+{
+    remove_proc_entry(PROCFS_ENTRY, NULL);
+    printk("sekigae module is unloaded.\n");
+}
+
+module_init(sekigae_init_module);
+module_exit(sekigae_cleanup_module);