erst-dbg.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * APEI Error Record Serialization Table debug support
  4 *
  5 * ERST is a way provided by APEI to save and retrieve hardware error
  6 * information to and from a persistent store. This file provide the
  7 * debugging/testing support for ERST kernel support and firmware
  8 * implementation.
  9 *
 10 * Copyright 2010 Intel Corp.
 11 *   Author: Huang Ying <ying.huang@intel.com>
 12 */
 13
 14#include <linux/kernel.h>
 15#include <linux/module.h>
 16#include <linux/uaccess.h>
 17#include <acpi/apei.h>
 18#include <linux/miscdevice.h>
 19
 20#include "apei-internal.h"
 21
 22#define ERST_DBG_PFX			"ERST DBG: "
 23
 24#define ERST_DBG_RECORD_LEN_MAX		0x4000
 25
 26static void *erst_dbg_buf;
 27static unsigned int erst_dbg_buf_len;
 28
 29/* Prevent erst_dbg_read/write from being invoked concurrently */
 30static DEFINE_MUTEX(erst_dbg_mutex);
 31
 32static int erst_dbg_open(struct inode *inode, struct file *file)
 33{
 34	int rc, *pos;
 35
 36	if (erst_disable)
 37		return -ENODEV;
 38
 39	pos = (int *)&file->private_data;
 40
 41	rc = erst_get_record_id_begin(pos);
 42	if (rc)
 43		return rc;
 44
 45	return nonseekable_open(inode, file);
 46}
 47
 48static int erst_dbg_release(struct inode *inode, struct file *file)
 49{
 50	erst_get_record_id_end();
 51
 52	return 0;
 53}
 54
 55static long erst_dbg_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
 56{
 57	int rc;
 58	u64 record_id;
 59	u32 record_count;
 60
 61	switch (cmd) {
 62	case APEI_ERST_CLEAR_RECORD:
 63		if (copy_from_user(&record_id, (void __user *)arg,
 64				   sizeof(record_id)))
 65			return -EFAULT;
 66		return erst_clear(record_id);
 67	case APEI_ERST_GET_RECORD_COUNT:
 68		rc = erst_get_record_count();
 69		if (rc < 0)
 70			return rc;
 71		record_count = rc;
 72		rc = put_user(record_count, (u32 __user *)arg);
 73		if (rc)
 74			return rc;
 75		return 0;
 76	default:
 77		return -ENOTTY;
 78	}
 79}
 80
 81static ssize_t erst_dbg_read(struct file *filp, char __user *ubuf,
 82			     size_t usize, loff_t *off)
 83{
 84	int rc, *pos;
 85	ssize_t len = 0;
 86	u64 id;
 87
 88	if (*off)
 89		return -EINVAL;
 90
 91	if (mutex_lock_interruptible(&erst_dbg_mutex) != 0)
 92		return -EINTR;
 93
 94	pos = (int *)&filp->private_data;
 95
 96retry_next:
 97	rc = erst_get_record_id_next(pos, &id);
 98	if (rc)
 99		goto out;
100	/* no more record */
101	if (id == APEI_ERST_INVALID_RECORD_ID) {
102		/*
103		 * If the persistent store is empty initially, the function
104		 * 'erst_read' below will return "-ENOENT" value. This causes
105		 * 'retry_next' label is entered again. The returned value
106		 * should be zero indicating the read operation is EOF.
107		 */
108		len = 0;
109
110		goto out;
111	}
112retry:
113	rc = len = erst_read_record(id, erst_dbg_buf, erst_dbg_buf_len,
114			erst_dbg_buf_len, NULL);
115	/* The record may be cleared by others, try read next record */
116	if (rc == -ENOENT)
117		goto retry_next;
118	if (rc < 0)
119		goto out;
120	if (len > ERST_DBG_RECORD_LEN_MAX) {
121		pr_warn(ERST_DBG_PFX
122			"Record (ID: 0x%llx) length is too long: %zd\n", id, len);
123		rc = -EIO;
124		goto out;
125	}
126	if (len > erst_dbg_buf_len) {
127		void *p;
128		rc = -ENOMEM;
129		p = kmalloc(len, GFP_KERNEL);
130		if (!p)
131			goto out;
132		kfree(erst_dbg_buf);
133		erst_dbg_buf = p;
134		erst_dbg_buf_len = len;
135		goto retry;
136	}
137
138	rc = -EINVAL;
139	if (len > usize)
140		goto out;
141
142	rc = -EFAULT;
143	if (copy_to_user(ubuf, erst_dbg_buf, len))
144		goto out;
145	rc = 0;
146out:
147	mutex_unlock(&erst_dbg_mutex);
148	return rc ? rc : len;
149}
150
151static ssize_t erst_dbg_write(struct file *filp, const char __user *ubuf,
152			      size_t usize, loff_t *off)
153{
154	int rc;
155	struct cper_record_header *rcd;
156
157	if (!capable(CAP_SYS_ADMIN))
158		return -EPERM;
159
160	if (usize > ERST_DBG_RECORD_LEN_MAX) {
161		pr_err(ERST_DBG_PFX "Too long record to be written\n");
162		return -EINVAL;
163	}
164
165	if (mutex_lock_interruptible(&erst_dbg_mutex))
166		return -EINTR;
167	if (usize > erst_dbg_buf_len) {
168		void *p;
169		rc = -ENOMEM;
170		p = kmalloc(usize, GFP_KERNEL);
171		if (!p)
172			goto out;
173		kfree(erst_dbg_buf);
174		erst_dbg_buf = p;
175		erst_dbg_buf_len = usize;
176	}
177	if (copy_from_user(erst_dbg_buf, ubuf, usize)) {
178		rc = -EFAULT;
179		goto out;
180	}
181	rcd = erst_dbg_buf;
182	rc = -EINVAL;
183	if (rcd->record_length != usize)
184		goto out;
185
186	rc = erst_write(erst_dbg_buf);
187
188out:
189	mutex_unlock(&erst_dbg_mutex);
190	return rc < 0 ? rc : usize;
191}
192
193static const struct file_operations erst_dbg_ops = {
194	.owner		= THIS_MODULE,
195	.open		= erst_dbg_open,
196	.release	= erst_dbg_release,
197	.read		= erst_dbg_read,
198	.write		= erst_dbg_write,
199	.unlocked_ioctl	= erst_dbg_ioctl,
200};
201
202static struct miscdevice erst_dbg_dev = {
203	.minor	= MISC_DYNAMIC_MINOR,
204	.name	= "erst_dbg",
205	.fops	= &erst_dbg_ops,
206};
207
208static __init int erst_dbg_init(void)
209{
210	if (erst_disable) {
211		pr_info(ERST_DBG_PFX "ERST support is disabled.\n");
212		return -ENODEV;
213	}
214	return misc_register(&erst_dbg_dev);
215}
216
217static __exit void erst_dbg_exit(void)
218{
219	misc_deregister(&erst_dbg_dev);
220	kfree(erst_dbg_buf);
221}
222
223module_init(erst_dbg_init);
224module_exit(erst_dbg_exit);
225
226MODULE_AUTHOR("Huang Ying");
227MODULE_DESCRIPTION("APEI Error Record Serialization Table debug support");
228MODULE_LICENSE("GPL");