xref: /linux/kernel/module/sysfs.c (revision 908fc4c2) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Module sysfs support
4  *
5  * Copyright (C) 2008 Rusty Russell
6  */
7 
8 #include <linux/module.h>
9 #include <linux/kernel.h>
10 #include <linux/fs.h>
11 #include <linux/sysfs.h>
12 #include <linux/slab.h>
13 #include <linux/kallsyms.h>
14 #include <linux/mutex.h>
15 #include "internal.h"
16 
17 /*
18  * /sys/module/foo/sections stuff
19  * J. Corbet <corbet@lwn.net>
20  */
21 #ifdef CONFIG_KALLSYMS
22 struct module_sect_attr {
23 	struct bin_attribute battr;
24 	unsigned long address;
25 };
26 
27 struct module_sect_attrs {
28 	struct attribute_group grp;
29 	unsigned int nsections;
30 	struct module_sect_attr attrs[];
31 };
32 
33 #define MODULE_SECT_READ_SIZE (3 /* "0x", "\n" */ + (BITS_PER_LONG / 4))
34 static ssize_t module_sect_read(struct file *file, struct kobject *kobj,
35 				struct bin_attribute *battr,
36 				char *buf, loff_t pos, size_t count)
37 {
38 	struct module_sect_attr *sattr =
39 		container_of(battr, struct module_sect_attr, battr);
40 	char bounce[MODULE_SECT_READ_SIZE + 1];
41 	size_t wrote;
42 
43 	if (pos != 0)
44 		return -EINVAL;
45 
46 	/*
47 	 * Since we're a binary read handler, we must account for the
48 	 * trailing NUL byte that sprintf will write: if "buf" is
49 	 * too small to hold the NUL, or the NUL is exactly the last
50 	 * byte, the read will look like it got truncated by one byte.
51 	 * Since there is no way to ask sprintf nicely to not write
52 	 * the NUL, we have to use a bounce buffer.
53 	 */
54 	wrote = scnprintf(bounce, sizeof(bounce), "0x%px\n",
55 			  kallsyms_show_value(file->f_cred)
56 				? (void *)sattr->address : NULL);
57 	count = min(count, wrote);
58 	memcpy(buf, bounce, count);
59 
60 	return count;
61 }
62 
63 static void free_sect_attrs(struct module_sect_attrs *sect_attrs)
64 {
65 	unsigned int section;
66 
67 	for (section = 0; section < sect_attrs->nsections; section++)
68 		kfree(sect_attrs->attrs[section].battr.attr.name);
69 	kfree(sect_attrs);
70 }
71 
72 static void add_sect_attrs(struct module *mod, const struct load_info *info)
73 {
74 	unsigned int nloaded = 0, i, size[2];
75 	struct module_sect_attrs *sect_attrs;
76 	struct module_sect_attr *sattr;
77 	struct bin_attribute **gattr;
78 
79 	/* Count loaded sections and allocate structures */
80 	for (i = 0; i < info->hdr->e_shnum; i++)
81 		if (!sect_empty(&info->sechdrs[i]))
82 			nloaded++;
83 	size[0] = ALIGN(struct_size(sect_attrs, attrs, nloaded),
84 			sizeof(sect_attrs->grp.bin_attrs[0]));
85 	size[1] = (nloaded + 1) * sizeof(sect_attrs->grp.bin_attrs[0]);
86 	sect_attrs = kzalloc(size[0] + size[1], GFP_KERNEL);
87 	if (!sect_attrs)
88 		return;
89 
90 	/* Setup section attributes. */
91 	sect_attrs->grp.name = "sections";
92 	sect_attrs->grp.bin_attrs = (void *)sect_attrs + size[0];
93 
94 	sect_attrs->nsections = 0;
95 	sattr = &sect_attrs->attrs[0];
96 	gattr = &sect_attrs->grp.bin_attrs[0];
97 	for (i = 0; i < info->hdr->e_shnum; i++) {
98 		Elf_Shdr *sec = &info->sechdrs[i];
99 
100 		if (sect_empty(sec))
101 			continue;
102 		sysfs_bin_attr_init(&sattr->battr);
103 		sattr->address = sec->sh_addr;
104 		sattr->battr.attr.name =
105 			kstrdup(info->secstrings + sec->sh_name, GFP_KERNEL);
106 		if (!sattr->battr.attr.name)
107 			goto out;
108 		sect_attrs->nsections++;
109 		sattr->battr.read = module_sect_read;
110 		sattr->battr.size = MODULE_SECT_READ_SIZE;
111 		sattr->battr.attr.mode = 0400;
112 		*(gattr++) = &(sattr++)->battr;
113 	}
114 	*gattr = NULL;
115 
116 	if (sysfs_create_group(&mod->mkobj.kobj, &sect_attrs->grp))
117 		goto out;
118 
119 	mod->sect_attrs = sect_attrs;
120 	return;
121 out:
122 	free_sect_attrs(sect_attrs);
123 }
124 
125 static void remove_sect_attrs(struct module *mod)
126 {
127 	if (mod->sect_attrs) {
128 		sysfs_remove_group(&mod->mkobj.kobj,
129 				   &mod->sect_attrs->grp);
130 		/*
131 		 * We are positive that no one is using any sect attrs
132 		 * at this point.  Deallocate immediately.
133 		 */
134 		free_sect_attrs(mod->sect_attrs);
135 		mod->sect_attrs = NULL;
136 	}
137 }
138 
139 /*
140  * /sys/module/foo/notes/.section.name gives contents of SHT_NOTE sections.
141  */
142 
143 struct module_notes_attrs {
144 	struct kobject *dir;
145 	unsigned int notes;
146 	struct bin_attribute attrs[];
147 };
148 
149 static ssize_t module_notes_read(struct file *filp, struct kobject *kobj,
150 				 struct bin_attribute *bin_attr,
151 				 char *buf, loff_t pos, size_t count)
152 {
153 	/*
154 	 * The caller checked the pos and count against our size.
155 	 */
156 	memcpy(buf, bin_attr->private + pos, count);
157 	return count;
158 }
159 
160 static void free_notes_attrs(struct module_notes_attrs *notes_attrs,
161 			     unsigned int i)
162 {
163 	if (notes_attrs->dir) {
164 		while (i-- > 0)
165 			sysfs_remove_bin_file(notes_attrs->dir,
166 					      &notes_attrs->attrs[i]);
167 		kobject_put(notes_attrs->dir);
168 	}
169 	kfree(notes_attrs);
170 }
171 
172 static void add_notes_attrs(struct module *mod, const struct load_info *info)
173 {
174 	unsigned int notes, loaded, i;
175 	struct module_notes_attrs *notes_attrs;
176 	struct bin_attribute *nattr;
177 
178 	/* failed to create section attributes, so can't create notes */
179 	if (!mod->sect_attrs)
180 		return;
181 
182 	/* Count notes sections and allocate structures.  */
183 	notes = 0;
184 	for (i = 0; i < info->hdr->e_shnum; i++)
185 		if (!sect_empty(&info->sechdrs[i]) &&
186 		    info->sechdrs[i].sh_type == SHT_NOTE)
187 			++notes;
188 
189 	if (notes == 0)
190 		return;
191 
192 	notes_attrs = kzalloc(struct_size(notes_attrs, attrs, notes),
193 			      GFP_KERNEL);
194 	if (!notes_attrs)
195 		return;
196 
197 	notes_attrs->notes = notes;
198 	nattr = &notes_attrs->attrs[0];
199 	for (loaded = i = 0; i < info->hdr->e_shnum; ++i) {
200 		if (sect_empty(&info->sechdrs[i]))
201 			continue;
202 		if (info->sechdrs[i].sh_type == SHT_NOTE) {
203 			sysfs_bin_attr_init(nattr);
204 			nattr->attr.name = mod->sect_attrs->attrs[loaded].battr.attr.name;
205 			nattr->attr.mode = 0444;
206 			nattr->size = info->sechdrs[i].sh_size;
207 			nattr->private = (void *)info->sechdrs[i].sh_addr;
208 			nattr->read = module_notes_read;
209 			++nattr;
210 		}
211 		++loaded;
212 	}
213 
214 	notes_attrs->dir = kobject_create_and_add("notes", &mod->mkobj.kobj);
215 	if (!notes_attrs->dir)
216 		goto out;
217 
218 	for (i = 0; i < notes; ++i)
219 		if (sysfs_create_bin_file(notes_attrs->dir,
220 					  &notes_attrs->attrs[i]))
221 			goto out;
222 
223 	mod->notes_attrs = notes_attrs;
224 	return;
225 
226 out:
227 	free_notes_attrs(notes_attrs, i);
228 }
229 
230 static void remove_notes_attrs(struct module *mod)
231 {
232 	if (mod->notes_attrs)
233 		free_notes_attrs(mod->notes_attrs, mod->notes_attrs->notes);
234 }
235 
236 #else /* !CONFIG_KALLSYMS */
237 static inline void add_sect_attrs(struct module *mod, const struct load_info *info) { }
238 static inline void remove_sect_attrs(struct module *mod) { }
239 static inline void add_notes_attrs(struct module *mod, const struct load_info *info) { }
240 static inline void remove_notes_attrs(struct module *mod) { }
241 #endif /* CONFIG_KALLSYMS */
242 
243 static void del_usage_links(struct module *mod)
244 {
245 #ifdef CONFIG_MODULE_UNLOAD
246 	struct module_use *use;
247 
248 	mutex_lock(&module_mutex);
249 	list_for_each_entry(use, &mod->target_list, target_list)
250 		sysfs_remove_link(use->target->holders_dir, mod->name);
251 	mutex_unlock(&module_mutex);
252 #endif
253 }
254 
255 static int add_usage_links(struct module *mod)
256 {
257 	int ret = 0;
258 #ifdef CONFIG_MODULE_UNLOAD
259 	struct module_use *use;
260 
261 	mutex_lock(&module_mutex);
262 	list_for_each_entry(use, &mod->target_list, target_list) {
263 		ret = sysfs_create_link(use->target->holders_dir,
264 					&mod->mkobj.kobj, mod->name);
265 		if (ret)
266 			break;
267 	}
268 	mutex_unlock(&module_mutex);
269 	if (ret)
270 		del_usage_links(mod);
271 #endif
272 	return ret;
273 }
274 
275 static void module_remove_modinfo_attrs(struct module *mod, int end)
276 {
277 	struct module_attribute *attr;
278 	int i;
279 
280 	for (i = 0; (attr = &mod->modinfo_attrs[i]); i++) {
281 		if (end >= 0 && i > end)
282 			break;
283 		/* pick a field to test for end of list */
284 		if (!attr->attr.name)
285 			break;
286 		sysfs_remove_file(&mod->mkobj.kobj, &attr->attr);
287 		if (attr->free)
288 			attr->free(mod);
289 	}
290 	kfree(mod->modinfo_attrs);
291 }
292 
293 static int module_add_modinfo_attrs(struct module *mod)
294 {
295 	struct module_attribute *attr;
296 	struct module_attribute *temp_attr;
297 	int error = 0;
298 	int i;
299 
300 	mod->modinfo_attrs = kzalloc((sizeof(struct module_attribute) *
301 					(modinfo_attrs_count + 1)),
302 					GFP_KERNEL);
303 	if (!mod->modinfo_attrs)
304 		return -ENOMEM;
305 
306 	temp_attr = mod->modinfo_attrs;
307 	for (i = 0; (attr = modinfo_attrs[i]); i++) {
308 		if (!attr->test || attr->test(mod)) {
309 			memcpy(temp_attr, attr, sizeof(*temp_attr));
310 			sysfs_attr_init(&temp_attr->attr);
311 			error = sysfs_create_file(&mod->mkobj.kobj,
312 						  &temp_attr->attr);
313 			if (error)
314 				goto error_out;
315 			++temp_attr;
316 		}
317 	}
318 
319 	return 0;
320 
321 error_out:
322 	if (i > 0)
323 		module_remove_modinfo_attrs(mod, --i);
324 	else
325 		kfree(mod->modinfo_attrs);
326 	return error;
327 }
328 
329 static void mod_kobject_put(struct module *mod)
330 {
331 	DECLARE_COMPLETION_ONSTACK(c);
332 
333 	mod->mkobj.kobj_completion = &c;
334 	kobject_put(&mod->mkobj.kobj);
335 	wait_for_completion(&c);
336 }
337 
338 static int mod_sysfs_init(struct module *mod)
339 {
340 	int err;
341 	struct kobject *kobj;
342 
343 	if (!module_sysfs_initialized) {
344 		pr_err("%s: module sysfs not initialized\n", mod->name);
345 		err = -EINVAL;
346 		goto out;
347 	}
348 
349 	kobj = kset_find_obj(module_kset, mod->name);
350 	if (kobj) {
351 		pr_err("%s: module is already loaded\n", mod->name);
352 		kobject_put(kobj);
353 		err = -EINVAL;
354 		goto out;
355 	}
356 
357 	mod->mkobj.mod = mod;
358 
359 	memset(&mod->mkobj.kobj, 0, sizeof(mod->mkobj.kobj));
360 	mod->mkobj.kobj.kset = module_kset;
361 	err = kobject_init_and_add(&mod->mkobj.kobj, &module_ktype, NULL,
362 				   "%s", mod->name);
363 	if (err)
364 		mod_kobject_put(mod);
365 
366 out:
367 	return err;
368 }
369 
370 int mod_sysfs_setup(struct module *mod,
371 		    const struct load_info *info,
372 			   struct kernel_param *kparam,
373 			   unsigned int num_params)
374 {
375 	int err;
376 
377 	err = mod_sysfs_init(mod);
378 	if (err)
379 		goto out;
380 
381 	mod->holders_dir = kobject_create_and_add("holders", &mod->mkobj.kobj);
382 	if (!mod->holders_dir) {
383 		err = -ENOMEM;
384 		goto out_unreg;
385 	}
386 
387 	err = module_param_sysfs_setup(mod, kparam, num_params);
388 	if (err)
389 		goto out_unreg_holders;
390 
391 	err = module_add_modinfo_attrs(mod);
392 	if (err)
393 		goto out_unreg_param;
394 
395 	err = add_usage_links(mod);
396 	if (err)
397 		goto out_unreg_modinfo_attrs;
398 
399 	add_sect_attrs(mod, info);
400 	add_notes_attrs(mod, info);
401 
402 	return 0;
403 
404 out_unreg_modinfo_attrs:
405 	module_remove_modinfo_attrs(mod, -1);
406 out_unreg_param:
407 	module_param_sysfs_remove(mod);
408 out_unreg_holders:
409 	kobject_put(mod->holders_dir);
410 out_unreg:
411 	mod_kobject_put(mod);
412 out:
413 	return err;
414 }
415 
416 static void mod_sysfs_fini(struct module *mod)
417 {
418 	remove_notes_attrs(mod);
419 	remove_sect_attrs(mod);
420 	mod_kobject_put(mod);
421 }
422 
423 void mod_sysfs_teardown(struct module *mod)
424 {
425 	del_usage_links(mod);
426 	module_remove_modinfo_attrs(mod, -1);
427 	module_param_sysfs_remove(mod);
428 	kobject_put(mod->mkobj.drivers_dir);
429 	kobject_put(mod->holders_dir);
430 	mod_sysfs_fini(mod);
431 }
432 
433 void init_param_lock(struct module *mod)
434 {
435 	mutex_init(&mod->param_lock);
436 }
437