module.c

Kernel code of linux kernel

static inline unsigned int find_pcpusec(Elf_Ehdr *hdr,
					Elf_Shdr *sechdrs,
					const char *secstrings)
{
	return 0;
}
static inline void percpu_modcopy(void *pcpudst, const void *src,
				  unsigned long size)
{
	/* pcpusec should be 0, and size of that section should be 0. */
	BUG_ON(size != 0);
}
#endif /* CONFIG_SMP */

#define MODINFO_ATTR(field)	\
static void setup_modinfo_##field(struct module *mod, const char *s)  \
{                                                                     \
	mod->field = kstrdup(s, GFP_KERNEL);                          \
}                                                                     \
static ssize_t show_modinfo_##field(struct module_attribute *mattr,   \
	                struct module *mod, char *buffer)             \
{                                                                     \
	return sprintf(buffer, "%s\n", mod->field);                   \
}                                                                     \
static int modinfo_##field##_exists(struct module *mod)               \
{                                                                     \
	return mod->field != NULL;                                    \
}                                                                     \
static void free_modinfo_##field(struct module *mod)                  \
{                                                                     \
	kfree(mod->field);                                            \
	mod->field = NULL;                                            \
}                                                                     \
static struct module_attribute modinfo_##field = {                    \
	.attr = { .name = __stringify(field), .mode = 0444 },         \
	.show = show_modinfo_##field,                                 \
	.setup = setup_modinfo_##field,                               \
	.test = modinfo_##field##_exists,                             \
	.free = free_modinfo_##field,                                 \
};

MODINFO_ATTR(version);
MODINFO_ATTR(srcversion);

static char last_unloaded_module[MODULE_NAME_LEN+1];

#ifdef CONFIG_MODULE_UNLOAD
/* Init the unload section of the module. */
static void module_unload_init(struct module *mod)
{
	unsigned int i;

	INIT_LIST_HEAD(&mod->modules_which_use_me);
	for (i = 0; i < NR_CPUS; i++)
		local_set(&mod->ref[i].count, 0);
	/* Hold reference count during initialization. */
	local_set(&mod->ref[raw_smp_processor_id()].count, 1);
	/* Backwards compatibility macros put refcount during init. */
	mod->waiter = current;
}

/* modules using other modules */
struct module_use
{
	struct list_head list;
	struct module *module_which_uses;
};

/* Does a already use b? */
static int already_uses(struct module *a, struct module *b)
{
	struct module_use *use;

	list_for_each_entry(use, &b->modules_which_use_me, list) {
		if (use->module_which_uses == a) {
			DEBUGP("%s uses %s!\n", a->name, b->name);
			return 1;
		}
	}
	DEBUGP("%s does not use %s!\n", a->name, b->name);
	return 0;
}

/* Module a uses b */
static int use_module(struct module *a, struct module *b)
{
	struct module_use *use;
	int no_warn, err;

	if (b == NULL || already_uses(a, b)) return 1;

	/* If we're interrupted or time out, we fail. */
	if (wait_event_interruptible_timeout(
		    module_wq, (err = strong_try_module_get(b)) != -EBUSY,
		    30 * HZ) <= 0) {
		printk("%s: gave up waiting for init of module %s.\n",
		       a->name, b->name);
		return 0;
	}

	/* If strong_try_module_get() returned a different error, we fail. */
	if (err)
		return 0;

	DEBUGP("Allocating new usage for %s.\n", a->name);
	use = kmalloc(sizeof(*use), GFP_ATOMIC);
	if (!use) {
		printk("%s: out of memory loading\n", a->name);
		module_put(b);
		return 0;
	}

	use->module_which_uses = a;
	list_add(&use->list, &b->modules_which_use_me);
	no_warn = sysfs_create_link(b->holders_dir, &a->mkobj.kobj, a->name);
	return 1;
}

/* Clear the unload stuff of the module. */
static void module_unload_free(struct module *mod)
{
	struct module *i;

	list_for_each_entry(i, &modules, list) {
		struct module_use *use;

		list_for_each_entry(use, &i->modules_which_use_me, list) {
			if (use->module_which_uses == mod) {
				DEBUGP("%s unusing %s\n", mod->name, i->name);
				module_put(i);
				list_del(&use->list);
				kfree(use);
				sysfs_remove_link(i->holders_dir, mod->name);
				/* There can be at most one match. */
				break;
			}
		}
	}
}

#ifdef CONFIG_MODULE_FORCE_UNLOAD
static inline int try_force_unload(unsigned int flags)
{
	int ret = (flags & O_TRUNC);
	if (ret)
		add_taint(TAINT_FORCED_RMMOD);
	return ret;
}
#else
static inline int try_force_unload(unsigned int flags)
{
	return 0;
}
#endif /* CONFIG_MODULE_FORCE_UNLOAD */

struct stopref
{
	struct module *mod;
	int flags;
	int *forced;
};

/* Whole machine is stopped with interrupts off when this runs. */
static int __try_stop_module(void *_sref)
{
	struct stopref *sref = _sref;

	/* If it's not unused, quit unless we're forcing. */
	if (module_refcount(sref->mod) != 0) {
		if (!(*sref->forced = try_force_unload(sref->flags)))
			return -EWOULDBLOCK;
	}

	/* Mark it as dying. */
	sref->mod->state = MODULE_STATE_GOING;
	return 0;
}

static int try_stop_module(struct module *mod, int flags, int *forced)
{
	if (flags & O_NONBLOCK) {
		struct stopref sref = { mod, flags, forced };

		return stop_machine(__try_stop_module, &sref, NULL);
	} else {
		/* We don't need to stop the machine for this. */
		mod->state = MODULE_STATE_GOING;
		synchronize_sched();
		return 0;
	}
}

unsigned int module_refcount(struct module *mod)
{
	unsigned int i, total = 0;

	for (i = 0; i < NR_CPUS; i++)
		total += local_read(&mod->ref[i].count);
	return total;
}
EXPORT_SYMBOL(module_refcount);

/* This exists whether we can unload or not */
static void free_module(struct module *mod);

static void wait_for_zero_refcount(struct module *mod)
{
	/* Since we might sleep for some time, release the mutex first */
	mutex_unlock(&module_mutex);
	for (;;) {
		DEBUGP("Looking at refcount...\n");
		set_current_state(TASK_UNINTERRUPTIBLE);
		if (module_refcount(mod) == 0)
			break;
		schedule();
	}
	current->state = TASK_RUNNING;
	mutex_lock(&module_mutex);
}

asmlinkage long
sys_delete_module(const char __user *name_user, unsigned int flags)
{
	struct module *mod;
	char name[MODULE_NAME_LEN];
	int ret, forced = 0;

	if (!capable(CAP_SYS_MODULE))
		return -EPERM;

	if (strncpy_from_user(name, name_user, MODULE_NAME_LEN-1) < 0)
		return -EFAULT;
	name[MODULE_NAME_LEN-1] = '\0';

	if (mutex_lock_interruptible(&module_mutex) != 0)
		return -EINTR;

	mod = find_module(name);
	if (!mod) {
		ret = -ENOENT;
		goto out;
	}

	if (!list_empty(&mod->modules_which_use_me)) {
		/* Other modules depend on us: get rid of them first. */
		ret = -EWOULDBLOCK;
		goto out;
	}

	/* Doing init or already dying? */
	if (mod->state != MODULE_STATE_LIVE) {
		/* FIXME: if (force), slam module count and wake up
                   waiter --RR */
		DEBUGP("%s already dying\n", mod->name);
		ret = -EBUSY;
		goto out;
	}

	/* If it has an init func, it must have an exit func to unload */
	if (mod->init && !mod->exit) {
		forced = try_force_unload(flags);
		if (!forced) {
			/* This module can't be removed */
			ret = -EBUSY;
			goto out;
		}
	}

	/* Set this up before setting mod->state */
	mod->waiter = current;

	/* Stop the machine so refcounts can't move and disable module. */
	ret = try_stop_module(mod, flags, &forced);
	if (ret != 0)
		goto out;

	/* Never wait if forced. */
	if (!forced && module_refcount(mod) != 0)
		wait_for_zero_refcount(mod);

	mutex_unlock(&module_mutex);
	/* Final destruction now noone is using it. */
	if (mod->exit != NULL)
		mod->exit();
	blocking_notifier_call_chain(&module_notify_list,
				     MODULE_STATE_GOING, mod);
	mutex_lock(&module_mutex);
	/* Store the name of the last unloaded module for diagnostic purposes */
	strlcpy(last_unloaded_module, mod->name, sizeof(last_unloaded_module));
	free_module(mod);

 out:
	mutex_unlock(&module_mutex);
	return ret;
}

static void print_unload_info(struct seq_file *m, struct module *mod)
{
	struct module_use *use;
	int printed_something = 0;

	seq_printf(m, " %u ", module_refcount(mod));

	/* Always include a trailing , so userspace can differentiate
           between this and the old multi-field proc format. */
	list_for_each_entry(use, &mod->modules_which_use_me, list) {
		printed_something = 1;
		seq_printf(m, "%s,", use->module_which_uses->name);
	}

	if (mod->init != NULL && mod->exit == NULL) {
		printed_something = 1;
		seq_printf(m, "[permanent],");
	}

	if (!printed_something)
		seq_printf(m, "-");
}

void __symbol_put(const char *symbol)
{
	struct module *owner;

	preempt_disable();
	if (IS_ERR_VALUE(find_symbol(symbol, &owner, NULL, true, false)))
		BUG();
	module_put(owner);
	preempt_enable();
}
EXPORT_SYMBOL(__symbol_put);

void symbol_put_addr(void *addr)
{
	struct module *modaddr;

	if (core_kernel_text((unsigned long)addr))
		return;

	if (!(modaddr = module_text_address((unsigned long)addr)))
		BUG();
	module_put(modaddr);
}
EXPORT_SYMBOL_GPL(symbol_put_addr);

static ssize_t show_refcnt(struct module_attribute *mattr,
			   struct module *mod, char *buffer)
{
	return sprintf(buffer, "%u\n", module_refcount(mod));
}

static struct module_attribute refcnt = {
	.attr = { .name = "refcnt", .mode = 0444 },
	.show = show_refcnt,
};

void module_put(struct module *module)
{
	if (module) {
		unsigned int cpu = get_cpu();
		local_dec(&module->ref[cpu].count);
		/* Maybe they're waiting for us to drop reference? */
		if (unlikely(!module_is_live(module)))
			wake_up_process(module->waiter);
		put_cpu();
	}
}
EXPORT_SYMBOL(module_put);

#else /* !CONFIG_MODULE_UNLOAD */
static void print_unload_info(struct seq_file *m, struct module *mod)
{
	/* We don't know the usage count, or what modules are using. */
	seq_printf(m, " - -");
}

static inline void module_unload_free(struct module *mod)
{
}

static inline int use_module(struct module *a, struct module *b)
{
	return strong_try_module_get(b) == 0;
}

static inline void module_unload_init(struct module *mod)
{
}
#endif /* CONFIG_MODULE_UNLOAD */

static ssize_t show_initstate(struct module_attribute *mattr,
			   struct module *mod, char *buffer)
{
	const char *state = "unknown";

	switch (mod->state) {
	case MODULE_STATE_LIVE:
		state = "live";
		break;
	case MODULE_STATE_COMING:
		state = "coming";
		break;
	case MODULE_STATE_GOING:
		state = "going";
		break;
	}
	return sprintf(buffer, "%s\n", state);
}

static struct module_attribute initstate = {
	.attr = { .name = "initstate", .mode = 0444 },
	.show = show_initstate,
};

static struct module_attribute *modinfo_attrs[] = {
	&modinfo_version,
	&modinfo_srcversion,
	&initstate,
#ifdef CONFIG_MODULE_UNLOAD
	&refcnt,
#endif
	NULL,
};

static const char vermagic[] = VERMAGIC_STRING;

static int try_to_force_load(struct module *mod, const char *symname)
{
#ifdef CONFIG_MODULE_FORCE_LOAD
	if (!(tainted & TAINT_FORCED_MODULE))
		printk("%s: no version for \"%s\" found: kernel tainted.\n",
		       mod->name, symname);
	add_taint_module(mod, TAINT_FORCED_MODULE);
	return 0;
#else
	return -ENOEXEC;
#endif
}

#ifdef CONFIG_MODVERSIONS
static int check_version(Elf_Shdr *sechdrs,
			 unsigned int versindex,
			 const char *symname,
			 struct module *mod, 
			 const unsigned long *crc)
{
	unsigned int i, num_versions;
	struct modversion_info *versions;

	/* Exporting module didn't supply crcs?  OK, we're already tainted. */
	if (!crc)
		return 1;

	/* No versions at all?  modprobe --force does this. */
	if (versindex == 0)
		return try_to_force_load(mod, symname) == 0;

	versions = (void *) sechdrs[versindex].sh_addr;
	num_versions = sechdrs[versindex].sh_size
		/ sizeof(struct modversion_info);

	for (i = 0; i < num_versions; i++) {
		if (strcmp(versions[i].name, symname) != 0)
			continue;

		if (versions[i].crc == *crc)
			return 1;
		DEBUGP("Found checksum %lX vs module %lX\n",
		       *crc, versions[i].crc);
		goto bad_version;
	}

	printk(KERN_WARNING "%s: no symbol version for %s\n",
	       mod->name, symname);
	return 0;

bad_version:
	printk("%s: disagrees about version of symbol %s\n",
	       mod->name, symname);
	return 0;
}

static inline int check_modstruct_version(Elf_Shdr *sechdrs,
					  unsigned int versindex,
					  struct module *mod)
{
	const unsigned long *crc;

	if (IS_ERR_VALUE(find_symbol("struct_module", NULL, &crc, true, false)))
		BUG();
	return check_version(sechdrs, versindex, "struct_module", mod, crc);
}

/* First part is kernel version, which we ignore if module has crcs. */
static inline int same_magic(const char *amagic, const char *bmagic,
			     bool has_crcs)
{
	if (has_crcs) {