1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 *  c 2001 PPC 64 Team, IBM Corp
4 *
5 * scan-log-data driver for PPC64  Todd Inglett <tinglett@vnet.ibm.com>
6 *
7 * When ppc64 hardware fails the service processor dumps internal state
8 * of the system.  After a reboot the operating system can access a dump
9 * of this data using this driver.  A dump exists if the device-tree
10 * /chosen/ibm,scan-log-data property exists.
11 *
12 * This driver exports /proc/powerpc/scan-log-dump which can be read.
13 * The driver supports only sequential reads.
14 *
15 * The driver looks at a write to the driver for the single word "reset".
16 * If given, the driver will reset the scanlog so the platform can free it.
17 */
18
19#include <linux/module.h>
20#include <linux/types.h>
21#include <linux/errno.h>
22#include <linux/proc_fs.h>
23#include <linux/init.h>
24#include <linux/delay.h>
25#include <linux/slab.h>
26#include <linux/uaccess.h>
27#include <asm/rtas.h>
28#include <asm/prom.h>
29
30#define MODULE_VERS "1.0"
31#define MODULE_NAME "scanlog"
32
33/* Status returns from ibm,scan-log-dump */
34#define SCANLOG_COMPLETE 0
35#define SCANLOG_HWERROR -1
36#define SCANLOG_CONTINUE 1
37
38
39static unsigned int ibm_scan_log_dump;			/* RTAS token */
40static unsigned int *scanlog_buffer;			/* The data buffer */
41
42static ssize_t scanlog_read(struct file *file, char __user *buf,
43			    size_t count, loff_t *ppos)
44{
45	unsigned int *data = scanlog_buffer;
46	int status;
47	unsigned long len, off;
48	unsigned int wait_time;
49
50	if (count > RTAS_DATA_BUF_SIZE)
51		count = RTAS_DATA_BUF_SIZE;
52
53	if (count < 1024) {
54		/* This is the min supported by this RTAS call.  Rather
55		 * than do all the buffering we insist the user code handle
56		 * larger reads.  As long as cp works... :)
57		 */
58		printk(KERN_ERR "scanlog: cannot perform a small read (%ld)\n", count);
59		return -EINVAL;
60	}
61
62	if (!access_ok(buf, count))
63		return -EFAULT;
64
65	for (;;) {
66		wait_time = 500;	/* default wait if no data */
67		spin_lock(&rtas_data_buf_lock);
68		memcpy(rtas_data_buf, data, RTAS_DATA_BUF_SIZE);
69		status = rtas_call(ibm_scan_log_dump, 2, 1, NULL,
70				   (u32) __pa(rtas_data_buf), (u32) count);
71		memcpy(data, rtas_data_buf, RTAS_DATA_BUF_SIZE);
72		spin_unlock(&rtas_data_buf_lock);
73
74		pr_debug("scanlog: status=%d, data[0]=%x, data[1]=%x, " \
75			 "data[2]=%x\n", status, data[0], data[1], data[2]);
76		switch (status) {
77		    case SCANLOG_COMPLETE:
78			pr_debug("scanlog: hit eof\n");
79			return 0;
80		    case SCANLOG_HWERROR:
81			pr_debug("scanlog: hardware error reading data\n");
82			return -EIO;
83		    case SCANLOG_CONTINUE:
84			/* We may or may not have data yet */
85			len = data[1];
86			off = data[2];
87			if (len > 0) {
88				if (copy_to_user(buf, ((char *)data)+off, len))
89					return -EFAULT;
90				return len;
91			}
92			/* Break to sleep default time */
93			break;
94		    default:
95			/* Assume extended busy */
96			wait_time = rtas_busy_delay_time(status);
97			if (!wait_time) {
98				printk(KERN_ERR "scanlog: unknown error " \
99				       "from rtas: %d\n", status);
100				return -EIO;
101			}
102		}
103		/* Apparently no data yet.  Wait and try again. */
104		msleep_interruptible(wait_time);
105	}
106	/*NOTREACHED*/
107}
108
109static ssize_t scanlog_write(struct file * file, const char __user * buf,
110			     size_t count, loff_t *ppos)
111{
112	char stkbuf[20];
113	int status;
114
115	if (count > 19) count = 19;
116	if (copy_from_user (stkbuf, buf, count)) {
117		return -EFAULT;
118	}
119	stkbuf[count] = 0;
120
121	if (buf) {
122		if (strncmp(stkbuf, "reset", 5) == 0) {
123			pr_debug("scanlog: reset scanlog\n");
124			status = rtas_call(ibm_scan_log_dump, 2, 1, NULL, 0, 0);
125			pr_debug("scanlog: rtas returns %d\n", status);
126		}
127	}
128	return count;
129}
130
131static int scanlog_open(struct inode * inode, struct file * file)
132{
133	unsigned int *data = scanlog_buffer;
134
135	if (data[0] != 0) {
136		/* This imperfect test stops a second copy of the
137		 * data (or a reset while data is being copied)
138		 */
139		return -EBUSY;
140	}
141
142	data[0] = 0;	/* re-init so we restart the scan */
143
144	return 0;
145}
146
147static int scanlog_release(struct inode * inode, struct file * file)
148{
149	unsigned int *data = scanlog_buffer;
150
151	data[0] = 0;
152	return 0;
153}
154
155static const struct proc_ops scanlog_proc_ops = {
156	.proc_read	= scanlog_read,
157	.proc_write	= scanlog_write,
158	.proc_open	= scanlog_open,
159	.proc_release	= scanlog_release,
160	.proc_lseek	= noop_llseek,
161};
162
163static int __init scanlog_init(void)
164{
165	struct proc_dir_entry *ent;
166	int err = -ENOMEM;
167
168	ibm_scan_log_dump = rtas_token("ibm,scan-log-dump");
169	if (ibm_scan_log_dump == RTAS_UNKNOWN_SERVICE)
170		return -ENODEV;
171
172	/* Ideally we could allocate a buffer < 4G */
173	scanlog_buffer = kzalloc(RTAS_DATA_BUF_SIZE, GFP_KERNEL);
174	if (!scanlog_buffer)
175		goto err;
176
177	ent = proc_create("powerpc/rtas/scan-log-dump", 0400, NULL,
178			  &scanlog_proc_ops);
179	if (!ent)
180		goto err;
181	return 0;
182err:
183	kfree(scanlog_buffer);
184	return err;
185}
186
187static void __exit scanlog_cleanup(void)
188{
189	remove_proc_entry("powerpc/rtas/scan-log-dump", NULL);
190	kfree(scanlog_buffer);
191}
192
193module_init(scanlog_init);
194module_exit(scanlog_cleanup);
195MODULE_LICENSE("GPL");
196