1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * dmi-sysfs.c
4 *
5 * This module exports the DMI tables read-only to userspace through the
6 * sysfs file system.
7 *
8 * Data is currently found below
9 *    /sys/firmware/dmi/...
10 *
11 * DMI attributes are presented in attribute files with names
12 * formatted using %d-%d, so that the first integer indicates the
13 * structure type (0-255), and the second field is the instance of that
14 * entry.
15 *
16 * Copyright 2011 Google, Inc.
17 */
18
19#include <linux/kernel.h>
20#include <linux/init.h>
21#include <linux/module.h>
22#include <linux/types.h>
23#include <linux/kobject.h>
24#include <linux/dmi.h>
25#include <linux/capability.h>
26#include <linux/slab.h>
27#include <linux/list.h>
28#include <linux/io.h>
29#include <asm/dmi.h>
30
31#define MAX_ENTRY_TYPE 255 /* Most of these aren't used, but we consider
32			      the top entry type is only 8 bits */
33
34struct dmi_sysfs_entry {
35	struct dmi_header dh;
36	struct kobject kobj;
37	int instance;
38	int position;
39	struct list_head list;
40	struct kobject *child;
41};
42
43/*
44 * Global list of dmi_sysfs_entry.  Even though this should only be
45 * manipulated at setup and teardown, the lazy nature of the kobject
46 * system means we get lazy removes.
47 */
48static LIST_HEAD(entry_list);
49static DEFINE_SPINLOCK(entry_list_lock);
50
51/* dmi_sysfs_attribute - Top level attribute. used by all entries. */
52struct dmi_sysfs_attribute {
53	struct attribute attr;
54	ssize_t (*show)(struct dmi_sysfs_entry *entry, char *buf);
55};
56
57#define DMI_SYSFS_ATTR(_entry, _name) \
58struct dmi_sysfs_attribute dmi_sysfs_attr_##_entry##_##_name = { \
59	.attr = {.name = __stringify(_name), .mode = 0400}, \
60	.show = dmi_sysfs_##_entry##_##_name, \
61}
62
63/*
64 * dmi_sysfs_mapped_attribute - Attribute where we require the entry be
65 * mapped in.  Use in conjunction with dmi_sysfs_specialize_attr_ops.
66 */
67struct dmi_sysfs_mapped_attribute {
68	struct attribute attr;
69	ssize_t (*show)(struct dmi_sysfs_entry *entry,
70			const struct dmi_header *dh,
71			char *buf);
72};
73
74#define DMI_SYSFS_MAPPED_ATTR(_entry, _name) \
75struct dmi_sysfs_mapped_attribute dmi_sysfs_attr_##_entry##_##_name = { \
76	.attr = {.name = __stringify(_name), .mode = 0400}, \
77	.show = dmi_sysfs_##_entry##_##_name, \
78}
79
80/*************************************************
81 * Generic DMI entry support.
82 *************************************************/
83static void dmi_entry_free(struct kobject *kobj)
84{
85	kfree(kobj);
86}
87
88static struct dmi_sysfs_entry *to_entry(struct kobject *kobj)
89{
90	return container_of(kobj, struct dmi_sysfs_entry, kobj);
91}
92
93static struct dmi_sysfs_attribute *to_attr(struct attribute *attr)
94{
95	return container_of(attr, struct dmi_sysfs_attribute, attr);
96}
97
98static ssize_t dmi_sysfs_attr_show(struct kobject *kobj,
99				   struct attribute *_attr, char *buf)
100{
101	struct dmi_sysfs_entry *entry = to_entry(kobj);
102	struct dmi_sysfs_attribute *attr = to_attr(_attr);
103
104	/* DMI stuff is only ever admin visible */
105	if (!capable(CAP_SYS_ADMIN))
106		return -EACCES;
107
108	return attr->show(entry, buf);
109}
110
111static const struct sysfs_ops dmi_sysfs_attr_ops = {
112	.show = dmi_sysfs_attr_show,
113};
114
115typedef ssize_t (*dmi_callback)(struct dmi_sysfs_entry *,
116				const struct dmi_header *dh, void *);
117
118struct find_dmi_data {
119	struct dmi_sysfs_entry	*entry;
120	dmi_callback		callback;
121	void			*private;
122	int			instance_countdown;
123	ssize_t			ret;
124};
125
126static void find_dmi_entry_helper(const struct dmi_header *dh,
127				  void *_data)
128{
129	struct find_dmi_data *data = _data;
130	struct dmi_sysfs_entry *entry = data->entry;
131
132	/* Is this the entry we want? */
133	if (dh->type != entry->dh.type)
134		return;
135
136	if (data->instance_countdown != 0) {
137		/* try the next instance? */
138		data->instance_countdown--;
139		return;
140	}
141
142	/*
143	 * Don't ever revisit the instance.  Short circuit later
144	 * instances by letting the instance_countdown run negative
145	 */
146	data->instance_countdown--;
147
148	/* Found the entry */
149	data->ret = data->callback(entry, dh, data->private);
150}
151
152/* State for passing the read parameters through dmi_find_entry() */
153struct dmi_read_state {
154	char *buf;
155	loff_t pos;
156	size_t count;
157};
158
159static ssize_t find_dmi_entry(struct dmi_sysfs_entry *entry,
160			      dmi_callback callback, void *private)
161{
162	struct find_dmi_data data = {
163		.entry = entry,
164		.callback = callback,
165		.private = private,
166		.instance_countdown = entry->instance,
167		.ret = -EIO,  /* To signal the entry disappeared */
168	};
169	int ret;
170
171	ret = dmi_walk(find_dmi_entry_helper, &data);
172	/* This shouldn't happen, but just in case. */
173	if (ret)
174		return -EINVAL;
175	return data.ret;
176}
177
178/*
179 * Calculate and return the byte length of the dmi entry identified by
180 * dh.  This includes both the formatted portion as well as the
181 * unformatted string space, including the two trailing nul characters.
182 */
183static size_t dmi_entry_length(const struct dmi_header *dh)
184{
185	const char *p = (const char *)dh;
186
187	p += dh->length;
188
189	while (p[0] || p[1])
190		p++;
191
192	return 2 + p - (const char *)dh;
193}
194
195/*************************************************
196 * Support bits for specialized DMI entry support
197 *************************************************/
198struct dmi_entry_attr_show_data {
199	struct attribute *attr;
200	char *buf;
201};
202
203static ssize_t dmi_entry_attr_show_helper(struct dmi_sysfs_entry *entry,
204					  const struct dmi_header *dh,
205					  void *_data)
206{
207	struct dmi_entry_attr_show_data *data = _data;
208	struct dmi_sysfs_mapped_attribute *attr;
209
210	attr = container_of(data->attr,
211			    struct dmi_sysfs_mapped_attribute, attr);
212	return attr->show(entry, dh, data->buf);
213}
214
215static ssize_t dmi_entry_attr_show(struct kobject *kobj,
216				   struct attribute *attr,
217				   char *buf)
218{
219	struct dmi_entry_attr_show_data data = {
220		.attr = attr,
221		.buf  = buf,
222	};
223	/* Find the entry according to our parent and call the
224	 * normalized show method hanging off of the attribute */
225	return find_dmi_entry(to_entry(kobj->parent),
226			      dmi_entry_attr_show_helper, &data);
227}
228
229static const struct sysfs_ops dmi_sysfs_specialize_attr_ops = {
230	.show = dmi_entry_attr_show,
231};
232
233/*************************************************
234 * Specialized DMI entry support.
235 *************************************************/
236
237/*** Type 15 - System Event Table ***/
238
239#define DMI_SEL_ACCESS_METHOD_IO8	0x00
240#define DMI_SEL_ACCESS_METHOD_IO2x8	0x01
241#define DMI_SEL_ACCESS_METHOD_IO16	0x02
242#define DMI_SEL_ACCESS_METHOD_PHYS32	0x03
243#define DMI_SEL_ACCESS_METHOD_GPNV	0x04
244
245struct dmi_system_event_log {
246	struct dmi_header header;
247	u16	area_length;
248	u16	header_start_offset;
249	u16	data_start_offset;
250	u8	access_method;
251	u8	status;
252	u32	change_token;
253	union {
254		struct {
255			u16 index_addr;
256			u16 data_addr;
257		} io;
258		u32	phys_addr32;
259		u16	gpnv_handle;
260		u32	access_method_address;
261	};
262	u8	header_format;
263	u8	type_descriptors_supported_count;
264	u8	per_log_type_descriptor_length;
265	u8	supported_log_type_descriptos[];
266} __packed;
267
268#define DMI_SYSFS_SEL_FIELD(_field) \
269static ssize_t dmi_sysfs_sel_##_field(struct dmi_sysfs_entry *entry, \
270				      const struct dmi_header *dh, \
271				      char *buf) \
272{ \
273	struct dmi_system_event_log sel; \
274	if (sizeof(sel) > dmi_entry_length(dh)) \
275		return -EIO; \
276	memcpy(&sel, dh, sizeof(sel)); \
277	return sprintf(buf, "%u\n", sel._field); \
278} \
279static DMI_SYSFS_MAPPED_ATTR(sel, _field)
280
281DMI_SYSFS_SEL_FIELD(area_length);
282DMI_SYSFS_SEL_FIELD(header_start_offset);
283DMI_SYSFS_SEL_FIELD(data_start_offset);
284DMI_SYSFS_SEL_FIELD(access_method);
285DMI_SYSFS_SEL_FIELD(status);
286DMI_SYSFS_SEL_FIELD(change_token);
287DMI_SYSFS_SEL_FIELD(access_method_address);
288DMI_SYSFS_SEL_FIELD(header_format);
289DMI_SYSFS_SEL_FIELD(type_descriptors_supported_count);
290DMI_SYSFS_SEL_FIELD(per_log_type_descriptor_length);
291
292static struct attribute *dmi_sysfs_sel_attrs[] = {
293	&dmi_sysfs_attr_sel_area_length.attr,
294	&dmi_sysfs_attr_sel_header_start_offset.attr,
295	&dmi_sysfs_attr_sel_data_start_offset.attr,
296	&dmi_sysfs_attr_sel_access_method.attr,
297	&dmi_sysfs_attr_sel_status.attr,
298	&dmi_sysfs_attr_sel_change_token.attr,
299	&dmi_sysfs_attr_sel_access_method_address.attr,
300	&dmi_sysfs_attr_sel_header_format.attr,
301	&dmi_sysfs_attr_sel_type_descriptors_supported_count.attr,
302	&dmi_sysfs_attr_sel_per_log_type_descriptor_length.attr,
303	NULL,
304};
305ATTRIBUTE_GROUPS(dmi_sysfs_sel);
306
307static const struct kobj_type dmi_system_event_log_ktype = {
308	.release = dmi_entry_free,
309	.sysfs_ops = &dmi_sysfs_specialize_attr_ops,
310	.default_groups = dmi_sysfs_sel_groups,
311};
312
313#ifdef CONFIG_HAS_IOPORT
314typedef u8 (*sel_io_reader)(const struct dmi_system_event_log *sel,
315			    loff_t offset);
316
317static DEFINE_MUTEX(io_port_lock);
318
319static u8 read_sel_8bit_indexed_io(const struct dmi_system_event_log *sel,
320				   loff_t offset)
321{
322	u8 ret;
323
324	mutex_lock(&io_port_lock);
325	outb((u8)offset, sel->io.index_addr);
326	ret = inb(sel->io.data_addr);
327	mutex_unlock(&io_port_lock);
328	return ret;
329}
330
331static u8 read_sel_2x8bit_indexed_io(const struct dmi_system_event_log *sel,
332				     loff_t offset)
333{
334	u8 ret;
335
336	mutex_lock(&io_port_lock);
337	outb((u8)offset, sel->io.index_addr);
338	outb((u8)(offset >> 8), sel->io.index_addr + 1);
339	ret = inb(sel->io.data_addr);
340	mutex_unlock(&io_port_lock);
341	return ret;
342}
343
344static u8 read_sel_16bit_indexed_io(const struct dmi_system_event_log *sel,
345				    loff_t offset)
346{
347	u8 ret;
348
349	mutex_lock(&io_port_lock);
350	outw((u16)offset, sel->io.index_addr);
351	ret = inb(sel->io.data_addr);
352	mutex_unlock(&io_port_lock);
353	return ret;
354}
355
356static sel_io_reader sel_io_readers[] = {
357	[DMI_SEL_ACCESS_METHOD_IO8]	= read_sel_8bit_indexed_io,
358	[DMI_SEL_ACCESS_METHOD_IO2x8]	= read_sel_2x8bit_indexed_io,
359	[DMI_SEL_ACCESS_METHOD_IO16]	= read_sel_16bit_indexed_io,
360};
361
362static ssize_t dmi_sel_raw_read_io(struct dmi_sysfs_entry *entry,
363				   const struct dmi_system_event_log *sel,
364				   char *buf, loff_t pos, size_t count)
365{
366	ssize_t wrote = 0;
367
368	sel_io_reader io_reader = sel_io_readers[sel->access_method];
369
370	while (count && pos < sel->area_length) {
371		count--;
372		*(buf++) = io_reader(sel, pos++);
373		wrote++;
374	}
375
376	return wrote;
377}
378#endif
379
380static ssize_t dmi_sel_raw_read_phys32(struct dmi_sysfs_entry *entry,
381				       const struct dmi_system_event_log *sel,
382				       char *buf, loff_t pos, size_t count)
383{
384	u8 __iomem *mapped;
385	ssize_t wrote = 0;
386
387	mapped = dmi_remap(sel->access_method_address, sel->area_length);
388	if (!mapped)
389		return -EIO;
390
391	while (count && pos < sel->area_length) {
392		count--;
393		*(buf++) = readb(mapped + pos++);
394		wrote++;
395	}
396
397	dmi_unmap(mapped);
398	return wrote;
399}
400
401static ssize_t dmi_sel_raw_read_helper(struct dmi_sysfs_entry *entry,
402				       const struct dmi_header *dh,
403				       void *_state)
404{
405	struct dmi_read_state *state = _state;
406	struct dmi_system_event_log sel;
407
408	if (sizeof(sel) > dmi_entry_length(dh))
409		return -EIO;
410
411	memcpy(&sel, dh, sizeof(sel));
412
413	switch (sel.access_method) {
414#ifdef CONFIG_HAS_IOPORT
415	case DMI_SEL_ACCESS_METHOD_IO8:
416	case DMI_SEL_ACCESS_METHOD_IO2x8:
417	case DMI_SEL_ACCESS_METHOD_IO16:
418		return dmi_sel_raw_read_io(entry, &sel, state->buf,
419					   state->pos, state->count);
420#endif
421	case DMI_SEL_ACCESS_METHOD_PHYS32:
422		return dmi_sel_raw_read_phys32(entry, &sel, state->buf,
423					       state->pos, state->count);
424	case DMI_SEL_ACCESS_METHOD_GPNV:
425		pr_info_ratelimited("dmi-sysfs: GPNV support missing.\n");
426		return -EIO;
427	default:
428		pr_info_ratelimited("dmi-sysfs: Unknown access method %02x\n",
429			sel.access_method);
430		return -EIO;
431	}
432}
433
434static ssize_t dmi_sel_raw_read(struct file *filp, struct kobject *kobj,
435				struct bin_attribute *bin_attr,
436				char *buf, loff_t pos, size_t count)
437{
438	struct dmi_sysfs_entry *entry = to_entry(kobj->parent);
439	struct dmi_read_state state = {
440		.buf = buf,
441		.pos = pos,
442		.count = count,
443	};
444
445	return find_dmi_entry(entry, dmi_sel_raw_read_helper, &state);
446}
447
448static struct bin_attribute dmi_sel_raw_attr = {
449	.attr = {.name = "raw_event_log", .mode = 0400},
450	.read = dmi_sel_raw_read,
451};
452
453static int dmi_system_event_log(struct dmi_sysfs_entry *entry)
454{
455	int ret;
456
457	entry->child = kzalloc(sizeof(*entry->child), GFP_KERNEL);
458	if (!entry->child)
459		return -ENOMEM;
460	ret = kobject_init_and_add(entry->child,
461				   &dmi_system_event_log_ktype,
462				   &entry->kobj,
463				   "system_event_log");
464	if (ret)
465		goto out_free;
466
467	ret = sysfs_create_bin_file(entry->child, &dmi_sel_raw_attr);
468	if (ret)
469		goto out_del;
470
471	return 0;
472
473out_del:
474	kobject_del(entry->child);
475out_free:
476	kfree(entry->child);
477	return ret;
478}
479
480/*************************************************
481 * Generic DMI entry support.
482 *************************************************/
483
484static ssize_t dmi_sysfs_entry_length(struct dmi_sysfs_entry *entry, char *buf)
485{
486	return sprintf(buf, "%d\n", entry->dh.length);
487}
488
489static ssize_t dmi_sysfs_entry_handle(struct dmi_sysfs_entry *entry, char *buf)
490{
491	return sprintf(buf, "%d\n", entry->dh.handle);
492}
493
494static ssize_t dmi_sysfs_entry_type(struct dmi_sysfs_entry *entry, char *buf)
495{
496	return sprintf(buf, "%d\n", entry->dh.type);
497}
498
499static ssize_t dmi_sysfs_entry_instance(struct dmi_sysfs_entry *entry,
500					char *buf)
501{
502	return sprintf(buf, "%d\n", entry->instance);
503}
504
505static ssize_t dmi_sysfs_entry_position(struct dmi_sysfs_entry *entry,
506					char *buf)
507{
508	return sprintf(buf, "%d\n", entry->position);
509}
510
511static DMI_SYSFS_ATTR(entry, length);
512static DMI_SYSFS_ATTR(entry, handle);
513static DMI_SYSFS_ATTR(entry, type);
514static DMI_SYSFS_ATTR(entry, instance);
515static DMI_SYSFS_ATTR(entry, position);
516
517static struct attribute *dmi_sysfs_entry_attrs[] = {
518	&dmi_sysfs_attr_entry_length.attr,
519	&dmi_sysfs_attr_entry_handle.attr,
520	&dmi_sysfs_attr_entry_type.attr,
521	&dmi_sysfs_attr_entry_instance.attr,
522	&dmi_sysfs_attr_entry_position.attr,
523	NULL,
524};
525ATTRIBUTE_GROUPS(dmi_sysfs_entry);
526
527static ssize_t dmi_entry_raw_read_helper(struct dmi_sysfs_entry *entry,
528					 const struct dmi_header *dh,
529					 void *_state)
530{
531	struct dmi_read_state *state = _state;
532	size_t entry_length;
533
534	entry_length = dmi_entry_length(dh);
535
536	return memory_read_from_buffer(state->buf, state->count,
537				       &state->pos, dh, entry_length);
538}
539
540static ssize_t dmi_entry_raw_read(struct file *filp,
541				  struct kobject *kobj,
542				  struct bin_attribute *bin_attr,
543				  char *buf, loff_t pos, size_t count)
544{
545	struct dmi_sysfs_entry *entry = to_entry(kobj);
546	struct dmi_read_state state = {
547		.buf = buf,
548		.pos = pos,
549		.count = count,
550	};
551
552	return find_dmi_entry(entry, dmi_entry_raw_read_helper, &state);
553}
554
555static const struct bin_attribute dmi_entry_raw_attr = {
556	.attr = {.name = "raw", .mode = 0400},
557	.read = dmi_entry_raw_read,
558};
559
560static void dmi_sysfs_entry_release(struct kobject *kobj)
561{
562	struct dmi_sysfs_entry *entry = to_entry(kobj);
563
564	spin_lock(&entry_list_lock);
565	list_del(&entry->list);
566	spin_unlock(&entry_list_lock);
567	kfree(entry);
568}
569
570static const struct kobj_type dmi_sysfs_entry_ktype = {
571	.release = dmi_sysfs_entry_release,
572	.sysfs_ops = &dmi_sysfs_attr_ops,
573	.default_groups = dmi_sysfs_entry_groups,
574};
575
576static struct kset *dmi_kset;
577
578/* Global count of all instances seen.  Only for setup */
579static int __initdata instance_counts[MAX_ENTRY_TYPE + 1];
580
581/* Global positional count of all entries seen.  Only for setup */
582static int __initdata position_count;
583
584static void __init dmi_sysfs_register_handle(const struct dmi_header *dh,
585					     void *_ret)
586{
587	struct dmi_sysfs_entry *entry;
588	int *ret = _ret;
589
590	/* If a previous entry saw an error, short circuit */
591	if (*ret)
592		return;
593
594	/* Allocate and register a new entry into the entries set */
595	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
596	if (!entry) {
597		*ret = -ENOMEM;
598		return;
599	}
600
601	/* Set the key */
602	memcpy(&entry->dh, dh, sizeof(*dh));
603	entry->instance = instance_counts[dh->type]++;
604	entry->position = position_count++;
605
606	entry->kobj.kset = dmi_kset;
607	*ret = kobject_init_and_add(&entry->kobj, &dmi_sysfs_entry_ktype, NULL,
608				    "%d-%d", dh->type, entry->instance);
609
610	/* Thread on the global list for cleanup */
611	spin_lock(&entry_list_lock);
612	list_add_tail(&entry->list, &entry_list);
613	spin_unlock(&entry_list_lock);
614
615	if (*ret) {
616		kobject_put(&entry->kobj);
617		return;
618	}
619
620	/* Handle specializations by type */
621	switch (dh->type) {
622	case DMI_ENTRY_SYSTEM_EVENT_LOG:
623		*ret = dmi_system_event_log(entry);
624		break;
625	default:
626		/* No specialization */
627		break;
628	}
629	if (*ret)
630		goto out_err;
631
632	/* Create the raw binary file to access the entry */
633	*ret = sysfs_create_bin_file(&entry->kobj, &dmi_entry_raw_attr);
634	if (*ret)
635		goto out_err;
636
637	return;
638out_err:
639	kobject_put(entry->child);
640	kobject_put(&entry->kobj);
641	return;
642}
643
644static void cleanup_entry_list(void)
645{
646	struct dmi_sysfs_entry *entry, *next;
647
648	/* No locks, we are on our way out */
649	list_for_each_entry_safe(entry, next, &entry_list, list) {
650		kobject_put(entry->child);
651		kobject_put(&entry->kobj);
652	}
653}
654
655static int __init dmi_sysfs_init(void)
656{
657	int error;
658	int val;
659
660	if (!dmi_kobj) {
661		pr_debug("dmi-sysfs: dmi entry is absent.\n");
662		error = -ENODATA;
663		goto err;
664	}
665
666	dmi_kset = kset_create_and_add("entries", NULL, dmi_kobj);
667	if (!dmi_kset) {
668		error = -ENOMEM;
669		goto err;
670	}
671
672	val = 0;
673	error = dmi_walk(dmi_sysfs_register_handle, &val);
674	if (error)
675		goto err;
676	if (val) {
677		error = val;
678		goto err;
679	}
680
681	pr_debug("dmi-sysfs: loaded.\n");
682
683	return 0;
684err:
685	cleanup_entry_list();
686	kset_unregister(dmi_kset);
687	return error;
688}
689
690/* clean up everything. */
691static void __exit dmi_sysfs_exit(void)
692{
693	pr_debug("dmi-sysfs: unloading.\n");
694	cleanup_entry_list();
695	kset_unregister(dmi_kset);
696}
697
698module_init(dmi_sysfs_init);
699module_exit(dmi_sysfs_exit);
700
701MODULE_AUTHOR("Mike Waychison <mikew@google.com>");
702MODULE_DESCRIPTION("DMI sysfs support");
703MODULE_LICENSE("GPL");
704