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
39 static unsigned int ibm_scan_log_dump; /* RTAS token */
40 static unsigned int *scanlog_buffer; /* The data buffer */
41
scanlog_read(struct file * file,char __user * buf,size_t count,loff_t * ppos)42 static 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
scanlog_write(struct file * file,const char __user * buf,size_t count,loff_t * ppos)109 static 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
scanlog_open(struct inode * inode,struct file * file)131 static 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
scanlog_release(struct inode * inode,struct file * file)147 static 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
155 static 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
scanlog_init(void)163 static 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;
182 err:
183 kfree(scanlog_buffer);
184 return err;
185 }
186
scanlog_cleanup(void)187 static void __exit scanlog_cleanup(void)
188 {
189 remove_proc_entry("powerpc/rtas/scan-log-dump", NULL);
190 kfree(scanlog_buffer);
191 }
192
193 module_init(scanlog_init);
194 module_exit(scanlog_cleanup);
195 MODULE_LICENSE("GPL");
196