1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Error log support on PowerNV.
4 *
5 * Copyright 2013,2014 IBM Corp.
6 */
7#include <linux/kernel.h>
8#include <linux/init.h>
9#include <linux/interrupt.h>
10#include <linux/of.h>
11#include <linux/slab.h>
12#include <linux/sysfs.h>
13#include <linux/fs.h>
14#include <linux/vmalloc.h>
15#include <linux/fcntl.h>
16#include <linux/kobject.h>
17#include <linux/uaccess.h>
18#include <asm/opal.h>
19
20struct elog_obj {
21	struct kobject kobj;
22	struct bin_attribute raw_attr;
23	uint64_t id;
24	uint64_t type;
25	size_t size;
26	char *buffer;
27};
28#define to_elog_obj(x) container_of(x, struct elog_obj, kobj)
29
30struct elog_attribute {
31	struct attribute attr;
32	ssize_t (*show)(struct elog_obj *elog, struct elog_attribute *attr,
33			char *buf);
34	ssize_t (*store)(struct elog_obj *elog, struct elog_attribute *attr,
35			 const char *buf, size_t count);
36};
37#define to_elog_attr(x) container_of(x, struct elog_attribute, attr)
38
39static ssize_t elog_id_show(struct elog_obj *elog_obj,
40			    struct elog_attribute *attr,
41			    char *buf)
42{
43	return sprintf(buf, "0x%llx\n", elog_obj->id);
44}
45
46static const char *elog_type_to_string(uint64_t type)
47{
48	switch (type) {
49	case 0: return "PEL";
50	default: return "unknown";
51	}
52}
53
54static ssize_t elog_type_show(struct elog_obj *elog_obj,
55			      struct elog_attribute *attr,
56			      char *buf)
57{
58	return sprintf(buf, "0x%llx %s\n",
59		       elog_obj->type,
60		       elog_type_to_string(elog_obj->type));
61}
62
63static ssize_t elog_ack_show(struct elog_obj *elog_obj,
64			     struct elog_attribute *attr,
65			     char *buf)
66{
67	return sprintf(buf, "ack - acknowledge log message\n");
68}
69
70static ssize_t elog_ack_store(struct elog_obj *elog_obj,
71			      struct elog_attribute *attr,
72			      const char *buf,
73			      size_t count)
74{
75	/*
76	 * Try to self remove this attribute. If we are successful,
77	 * delete the kobject itself.
78	 */
79	if (sysfs_remove_file_self(&elog_obj->kobj, &attr->attr)) {
80		opal_send_ack_elog(elog_obj->id);
81		kobject_put(&elog_obj->kobj);
82	}
83	return count;
84}
85
86static struct elog_attribute id_attribute =
87	__ATTR(id, 0444, elog_id_show, NULL);
88static struct elog_attribute type_attribute =
89	__ATTR(type, 0444, elog_type_show, NULL);
90static struct elog_attribute ack_attribute =
91	__ATTR(acknowledge, 0660, elog_ack_show, elog_ack_store);
92
93static struct kset *elog_kset;
94
95static ssize_t elog_attr_show(struct kobject *kobj,
96			      struct attribute *attr,
97			      char *buf)
98{
99	struct elog_attribute *attribute;
100	struct elog_obj *elog;
101
102	attribute = to_elog_attr(attr);
103	elog = to_elog_obj(kobj);
104
105	if (!attribute->show)
106		return -EIO;
107
108	return attribute->show(elog, attribute, buf);
109}
110
111static ssize_t elog_attr_store(struct kobject *kobj,
112			       struct attribute *attr,
113			       const char *buf, size_t len)
114{
115	struct elog_attribute *attribute;
116	struct elog_obj *elog;
117
118	attribute = to_elog_attr(attr);
119	elog = to_elog_obj(kobj);
120
121	if (!attribute->store)
122		return -EIO;
123
124	return attribute->store(elog, attribute, buf, len);
125}
126
127static const struct sysfs_ops elog_sysfs_ops = {
128	.show = elog_attr_show,
129	.store = elog_attr_store,
130};
131
132static void elog_release(struct kobject *kobj)
133{
134	struct elog_obj *elog;
135
136	elog = to_elog_obj(kobj);
137	kfree(elog->buffer);
138	kfree(elog);
139}
140
141static struct attribute *elog_default_attrs[] = {
142	&id_attribute.attr,
143	&type_attribute.attr,
144	&ack_attribute.attr,
145	NULL,
146};
147
148static struct kobj_type elog_ktype = {
149	.sysfs_ops = &elog_sysfs_ops,
150	.release = &elog_release,
151	.default_attrs = elog_default_attrs,
152};
153
154/* Maximum size of a single log on FSP is 16KB */
155#define OPAL_MAX_ERRLOG_SIZE	16384
156
157static ssize_t raw_attr_read(struct file *filep, struct kobject *kobj,
158			     struct bin_attribute *bin_attr,
159			     char *buffer, loff_t pos, size_t count)
160{
161	int opal_rc;
162
163	struct elog_obj *elog = to_elog_obj(kobj);
164
165	/* We may have had an error reading before, so let's retry */
166	if (!elog->buffer) {
167		elog->buffer = kzalloc(elog->size, GFP_KERNEL);
168		if (!elog->buffer)
169			return -EIO;
170
171		opal_rc = opal_read_elog(__pa(elog->buffer),
172					 elog->size, elog->id);
173		if (opal_rc != OPAL_SUCCESS) {
174			pr_err("ELOG: log read failed for log-id=%llx\n",
175			       elog->id);
176			kfree(elog->buffer);
177			elog->buffer = NULL;
178			return -EIO;
179		}
180	}
181
182	memcpy(buffer, elog->buffer + pos, count);
183
184	return count;
185}
186
187static void create_elog_obj(uint64_t id, size_t size, uint64_t type)
188{
189	struct elog_obj *elog;
190	int rc;
191
192	elog = kzalloc(sizeof(*elog), GFP_KERNEL);
193	if (!elog)
194		return;
195
196	elog->kobj.kset = elog_kset;
197
198	kobject_init(&elog->kobj, &elog_ktype);
199
200	sysfs_bin_attr_init(&elog->raw_attr);
201
202	elog->raw_attr.attr.name = "raw";
203	elog->raw_attr.attr.mode = 0400;
204	elog->raw_attr.size = size;
205	elog->raw_attr.read = raw_attr_read;
206
207	elog->id = id;
208	elog->size = size;
209	elog->type = type;
210
211	elog->buffer = kzalloc(elog->size, GFP_KERNEL);
212
213	if (elog->buffer) {
214		rc = opal_read_elog(__pa(elog->buffer),
215					 elog->size, elog->id);
216		if (rc != OPAL_SUCCESS) {
217			pr_err("ELOG: log read failed for log-id=%llx\n",
218			       elog->id);
219			kfree(elog->buffer);
220			elog->buffer = NULL;
221		}
222	}
223
224	rc = kobject_add(&elog->kobj, NULL, "0x%llx", id);
225	if (rc) {
226		kobject_put(&elog->kobj);
227		return;
228	}
229
230	/*
231	 * As soon as the sysfs file for this elog is created/activated there is
232	 * a chance the opal_errd daemon (or any userspace) might read and
233	 * acknowledge the elog before kobject_uevent() is called. If that
234	 * happens then there is a potential race between
235	 * elog_ack_store->kobject_put() and kobject_uevent() which leads to a
236	 * use-after-free of a kernfs object resulting in a kernel crash.
237	 *
238	 * To avoid that, we need to take a reference on behalf of the bin file,
239	 * so that our reference remains valid while we call kobject_uevent().
240	 * We then drop our reference before exiting the function, leaving the
241	 * bin file to drop the last reference (if it hasn't already).
242	 */
243
244	/* Take a reference for the bin file */
245	kobject_get(&elog->kobj);
246	rc = sysfs_create_bin_file(&elog->kobj, &elog->raw_attr);
247	if (rc == 0) {
248		kobject_uevent(&elog->kobj, KOBJ_ADD);
249	} else {
250		/* Drop the reference taken for the bin file */
251		kobject_put(&elog->kobj);
252	}
253
254	/* Drop our reference */
255	kobject_put(&elog->kobj);
256
257	return;
258}
259
260static irqreturn_t elog_event(int irq, void *data)
261{
262	__be64 size;
263	__be64 id;
264	__be64 type;
265	uint64_t elog_size;
266	uint64_t log_id;
267	uint64_t elog_type;
268	int rc;
269	char name[2+16+1];
270	struct kobject *kobj;
271
272	rc = opal_get_elog_size(&id, &size, &type);
273	if (rc != OPAL_SUCCESS) {
274		pr_err("ELOG: OPAL log info read failed\n");
275		return IRQ_HANDLED;
276	}
277
278	elog_size = be64_to_cpu(size);
279	log_id = be64_to_cpu(id);
280	elog_type = be64_to_cpu(type);
281
282	WARN_ON(elog_size > OPAL_MAX_ERRLOG_SIZE);
283
284	if (elog_size >= OPAL_MAX_ERRLOG_SIZE)
285		elog_size  =  OPAL_MAX_ERRLOG_SIZE;
286
287	sprintf(name, "0x%llx", log_id);
288
289	/* we may get notified twice, let's handle
290	 * that gracefully and not create two conflicting
291	 * entries.
292	 */
293	kobj = kset_find_obj(elog_kset, name);
294	if (kobj) {
295		/* Drop reference added by kset_find_obj() */
296		kobject_put(kobj);
297		return IRQ_HANDLED;
298	}
299
300	create_elog_obj(log_id, elog_size, elog_type);
301
302	return IRQ_HANDLED;
303}
304
305int __init opal_elog_init(void)
306{
307	int rc = 0, irq;
308
309	/* ELOG not supported by firmware */
310	if (!opal_check_token(OPAL_ELOG_READ))
311		return -1;
312
313	elog_kset = kset_create_and_add("elog", NULL, opal_kobj);
314	if (!elog_kset) {
315		pr_warn("%s: failed to create elog kset\n", __func__);
316		return -1;
317	}
318
319	irq = opal_event_request(ilog2(OPAL_EVENT_ERROR_LOG_AVAIL));
320	if (!irq) {
321		pr_err("%s: Can't register OPAL event irq (%d)\n",
322		       __func__, irq);
323		return irq;
324	}
325
326	rc = request_threaded_irq(irq, NULL, elog_event,
327			IRQF_TRIGGER_HIGH | IRQF_ONESHOT, "opal-elog", NULL);
328	if (rc) {
329		pr_err("%s: Can't request OPAL event irq (%d)\n",
330		       __func__, rc);
331		return rc;
332	}
333
334	/* We are now ready to pull error logs from opal. */
335	if (opal_check_token(OPAL_ELOG_RESEND))
336		opal_resend_pending_logs();
337
338	return 0;
339}
340