arch/powerpc/platforms/powernv/opal-elog.c

   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
  20 struct 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
  30 struct 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
  39 static 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
  46 static 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
  54 static 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
  63 static 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
  70 static 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
  86 static struct elog_attribute id_attribute =
  87         __ATTR(id, 0444, elog_id_show, NULL);
  88 static struct elog_attribute type_attribute =
  89         __ATTR(type, 0444, elog_type_show, NULL);
  90 static struct elog_attribute ack_attribute =
  91         __ATTR(acknowledge, 0660, elog_ack_show, elog_ack_store);
  92
  93 static struct kset *elog_kset;
  94
  95 static 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
 111 static 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
 127 static const struct sysfs_ops elog_sysfs_ops = {
 128         .show = elog_attr_show,
 129         .store = elog_attr_store,
 130 };
 131
 132 static 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
 141 static struct attribute *elog_default_attrs[] = {
 142         &id_attribute.attr,
 143         &type_attribute.attr,
 144         &ack_attribute.attr,
 145         NULL,
 146 };
 147
 148 static 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
 157 static 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_ratelimited("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
 187 static 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
 260 static 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
 305 int __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 }