module_init(), module_exit() をみる

モジュールのロード/アンロードで使われているらしい
module_init(), module_exit() をみる。

/usr/src/linux-2.6.16/include/linux/init.h をみる

/**
 * module_init() - driver initialization entry point
 * @x: function to be run at kernel boot time or module insertion
 *
 * module_init() will either be called during do_initcalls (if
 * builtin) or at module insertion time (if a module).  There can only
 * be one per module.
 */
#define module_init(x)  __initcall(x);

/**
 * module_exit() - driver exit entry point
 * @x: function to be run when driver is removed
 *
 * module_exit() will wrap the driver clean-up code
 * with cleanup_module() when used with rmmod when
 * the driver is a module.  If the driver is statically
 * compiled into the kernel, module_exit() has no effect.
 * There can only be one per module.
 */
#define module_exit(x)  __exitcall(x);

マクロ関数だった。
ふむふむ。

/usr/src/linux-2.6.16/include/linux/module.h をみる

Hello, Worldプログラムでは
あとひとつ、module.hをインクルードしているので、みてみる。

module構造体に、module_initでポインタが用意されている。
ふむふむ。

struct module
{
    enum module_state state;

    /* Member of list of modules */
    struct list_head list;

    /* Unique handle for this module */
    char name[MODULE_NAME_LEN];

    /* Sysfs stuff. */
    struct module_kobject mkobj;
    struct module_param_attrs *param_attrs;
    const char *version;
    const char *srcversion;

    /* Exported symbols */
    const struct kernel_symbol *syms;
    unsigned int num_syms;
    const unsigned long *crcs;

    /* GPL-only exported symbols. */
    const struct kernel_symbol *gpl_syms;
    unsigned int num_gpl_syms;
    const unsigned long *gpl_crcs;

    /* Exception table */
    unsigned int num_exentries;
    const struct exception_table_entry *extable;

    /* Startup function. */
    int (*init)(void);

    /* If this is non-NULL, vfree after init() returns */
    void *module_init;

    /* Here is the actual code + data, vfree'd on unload. */
    void *module_core;

    /* Here are the sizes of the init and core sections */
    unsigned long init_size, core_size;

    /* The size of the executable code in each section.  */
    unsigned long init_text_size, core_text_size;

    /* Arch-specific module values */
    struct mod_arch_specific arch;

    /* Am I unsafe to unload? */
    int unsafe;

    /* Am I GPL-compatible */
    int license_gplok;

#ifdef CONFIG_MODULE_UNLOAD
    /* Reference counts */
    struct module_ref ref[NR_CPUS];

    /* What modules depend on me? */
    struct list_head modules_which_use_me;

    /* Who is waiting for us to be unloaded */
    struct task_struct *waiter;

    /* Destruction function. */
    void (*exit)(void);
#endif

#ifdef CONFIG_KALLSYMS
    /* We keep the symbol and string tables for kallsyms. */
    Elf_Sym *symtab;
    unsigned long num_symtab;
    char *strtab;

    /* Section attributes */
    struct module_sect_attrs *sect_attrs;
#endif

    /* Per-cpu data. */
    void *percpu;

    /* The command line arguments (may be mangled).  People like
       keeping pointers to this stuff */
    char *args;
};