arch/powerpc/platforms/pseries/scanlog.c

   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
  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
 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
 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
 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
 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
 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");