kernel/trace/trace_ksym.c

   1 /*
   2  * trace_ksym.c - Kernel Symbol Tracer
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17  *
  18  * Copyright (C) IBM Corporation, 2009
  19  */
  20
  21 #include <linux/kallsyms.h>
  22 #include <linux/uaccess.h>
  23 #include <linux/debugfs.h>
  24 #include <linux/ftrace.h>
  25 #include <linux/module.h>
  26 #include <linux/fs.h>
  27
  28 #include "trace_output.h"
  29 #include "trace_stat.h"
  30 #include "trace.h"
  31
  32 /* For now, let us restrict the no. of symbols traced simultaneously to number
  33  * of available hardware breakpoint registers.
  34  */
  35 #define KSYM_TRACER_MAX HBP_NUM
  36
  37 #define KSYM_TRACER_OP_LEN 3 /* rw- */
  38
  39 struct trace_ksym {
  40         struct hw_breakpoint    *ksym_hbp;
  41         unsigned long           ksym_addr;
  42 #ifdef CONFIG_PROFILE_KSYM_TRACER
  43         unsigned long           counter;
  44 #endif
  45         struct hlist_node       ksym_hlist;
  46 };
  47
  48 static struct trace_array *ksym_trace_array;
  49
  50 static unsigned int ksym_filter_entry_count;
  51 static unsigned int ksym_tracing_enabled;
  52
  53 static HLIST_HEAD(ksym_filter_head);
  54
  55 static DEFINE_MUTEX(ksym_tracer_mutex);
  56
  57 #ifdef CONFIG_PROFILE_KSYM_TRACER
  58
  59 #define MAX_UL_INT 0xffffffff
  60
  61 void ksym_collect_stats(unsigned long hbp_hit_addr)
  62 {
  63         struct hlist_node *node;
  64         struct trace_ksym *entry;
  65
  66         rcu_read_lock();
  67         hlist_for_each_entry_rcu(entry, node, &ksym_filter_head, ksym_hlist) {
  68                 if ((entry->ksym_addr == hbp_hit_addr) &&
  69                     (entry->counter <= MAX_UL_INT)) {
  70                         entry->counter++;
  71                         break;
  72                 }
  73         }
  74         rcu_read_unlock();
  75 }
  76 #endif /* CONFIG_PROFILE_KSYM_TRACER */
  77
  78 void ksym_hbp_handler(struct hw_breakpoint *hbp, struct pt_regs *regs)
  79 {
  80         struct ring_buffer_event *event;
  81         struct trace_array *tr;
  82         struct ksym_trace_entry *entry;
  83         int pc;
  84
  85         if (!ksym_tracing_enabled)
  86                 return;
  87
  88         tr = ksym_trace_array;
  89         pc = preempt_count();
  90
  91         event = trace_buffer_lock_reserve(tr, TRACE_KSYM,
  92                                                         sizeof(*entry), 0, pc);
  93         if (!event)
  94                 return;
  95
  96         entry           = ring_buffer_event_data(event);
  97         entry->ip       = instruction_pointer(regs);
  98         entry->type     = hbp->info.type;
  99         strlcpy(entry->ksym_name, hbp->info.name, KSYM_SYMBOL_LEN);
 100         strlcpy(entry->cmd, current->comm, TASK_COMM_LEN);
 101
 102 #ifdef CONFIG_PROFILE_KSYM_TRACER
 103         ksym_collect_stats(hbp->info.address);
 104 #endif /* CONFIG_PROFILE_KSYM_TRACER */
 105
 106         trace_buffer_unlock_commit(tr, event, 0, pc);
 107 }
 108
 109 /* Valid access types are represented as
 110  *
 111  * rw- : Set Read/Write Access Breakpoint
 112  * -w- : Set Write Access Breakpoint
 113  * --- : Clear Breakpoints
 114  * --x : Set Execution Break points (Not available yet)
 115  *
 116  */
 117 static int ksym_trace_get_access_type(char *str)
 118 {
 119         int access = 0;
 120
 121         if (str[0] == 'r')
 122                 access += 4;
 123         else if (str[0] != '-')
 124                 return -EINVAL;
 125
 126         if (str[1] == 'w')
 127                 access += 2;
 128         else if (str[1] != '-')
 129                 return -EINVAL;
 130
 131         if (str[2] != '-')
 132                 return -EINVAL;
 133
 134         switch (access) {
 135         case 6:
 136                 access = HW_BREAKPOINT_RW;
 137                 break;
 138         case 4:
 139                 access = -EINVAL;
 140                 break;
 141         case 2:
 142                 access = HW_BREAKPOINT_WRITE;
 143                 break;
 144         }
 145
 146         return access;
 147 }
 148
 149 /*
 150  * There can be several possible malformed requests and we attempt to capture
 151  * all of them. We enumerate some of the rules
 152  * 1. We will not allow kernel symbols with ':' since it is used as a delimiter.
 153  *    i.e. multiple ':' symbols disallowed. Possible uses are of the form
 154  *    <module>:<ksym_name>:<op>.
 155  * 2. No delimiter symbol ':' in the input string
 156  * 3. Spurious operator symbols or symbols not in their respective positions
 157  * 4. <ksym_name>:--- i.e. clear breakpoint request when ksym_name not in file
 158  * 5. Kernel symbol not a part of /proc/kallsyms
 159  * 6. Duplicate requests
 160  */
 161 static int parse_ksym_trace_str(char *input_string, char **ksymname,
 162                                                         unsigned long *addr)
 163 {
 164         int ret;
 165
 166         *ksymname = strsep(&input_string, ":");
 167         *addr = kallsyms_lookup_name(*ksymname);
 168
 169         /* Check for malformed request: (2), (1) and (5) */
 170         if ((!input_string) ||
 171             (strlen(input_string) != KSYM_TRACER_OP_LEN) ||
 172             (*addr == 0))
 173                 return -EINVAL;;
 174
 175         ret = ksym_trace_get_access_type(input_string);
 176
 177         return ret;
 178 }
 179
 180 int process_new_ksym_entry(char *ksymname, int op, unsigned long addr)
 181 {
 182         struct trace_ksym *entry;
 183         int ret = -ENOMEM;
 184
 185         if (ksym_filter_entry_count >= KSYM_TRACER_MAX) {
 186                 printk(KERN_ERR "ksym_tracer: Maximum limit:(%d) reached. No"
 187                 " new requests for tracing can be accepted now.\n",
 188                         KSYM_TRACER_MAX);
 189                 return -ENOSPC;
 190         }
 191
 192         entry = kzalloc(sizeof(struct trace_ksym), GFP_KERNEL);
 193         if (!entry)
 194                 return -ENOMEM;
 195
 196         entry->ksym_hbp = kzalloc(sizeof(struct hw_breakpoint), GFP_KERNEL);
 197         if (!entry->ksym_hbp)
 198                 goto err;
 199
 200         entry->ksym_hbp->info.name = kstrdup(ksymname, GFP_KERNEL);
 201         if (!entry->ksym_hbp->info.name)
 202                 goto err;
 203
 204         entry->ksym_hbp->info.type = op;
 205         entry->ksym_addr = entry->ksym_hbp->info.address = addr;
 206 #ifdef CONFIG_X86
 207         entry->ksym_hbp->info.len = HW_BREAKPOINT_LEN_4;
 208 #endif
 209         entry->ksym_hbp->triggered = (void *)ksym_hbp_handler;
 210
 211         ret = register_kernel_hw_breakpoint(entry->ksym_hbp);
 212         if (ret < 0) {
 213                 printk(KERN_INFO "ksym_tracer request failed. Try again"
 214                                         " later!!\n");
 215                 ret = -EAGAIN;
 216                 goto err;
 217         }
 218         hlist_add_head_rcu(&(entry->ksym_hlist), &ksym_filter_head);
 219         ksym_filter_entry_count++;
 220         return 0;
 221 err:
 222         if (entry->ksym_hbp)
 223                 kfree(entry->ksym_hbp->info.name);
 224         kfree(entry->ksym_hbp);
 225         kfree(entry);
 226         return ret;
 227 }
 228
 229 static ssize_t ksym_trace_filter_read(struct file *filp, char __user *ubuf,
 230                                                 size_t count, loff_t *ppos)
 231 {
 232         struct trace_ksym *entry;
 233         struct hlist_node *node;
 234         struct trace_seq *s;
 235         ssize_t cnt = 0;
 236         int ret;
 237
 238         s = kmalloc(sizeof(*s), GFP_KERNEL);
 239         if (!s)
 240                 return -ENOMEM;
 241         trace_seq_init(s);
 242
 243         mutex_lock(&ksym_tracer_mutex);
 244
 245         hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) {
 246                 ret = trace_seq_printf(s, "%s:", entry->ksym_hbp->info.name);
 247                 if (entry->ksym_hbp->info.type == HW_BREAKPOINT_WRITE)
 248                         ret = trace_seq_puts(s, "-w-\n");
 249                 else if (entry->ksym_hbp->info.type == HW_BREAKPOINT_RW)
 250                         ret = trace_seq_puts(s, "rw-\n");
 251                 WARN_ON_ONCE(!ret);
 252         }
 253
 254         cnt = simple_read_from_buffer(ubuf, count, ppos, s->buffer, s->len);
 255
 256         mutex_unlock(&ksym_tracer_mutex);
 257
 258         kfree(s);
 259
 260         return cnt;
 261 }
 262
 263 static void __ksym_trace_reset(void)
 264 {
 265         struct trace_ksym *entry;
 266         struct hlist_node *node, *node1;
 267
 268         mutex_lock(&ksym_tracer_mutex);
 269         hlist_for_each_entry_safe(entry, node, node1, &ksym_filter_head,
 270                                                                 ksym_hlist) {
 271                 unregister_kernel_hw_breakpoint(entry->ksym_hbp);
 272                 ksym_filter_entry_count--;
 273                 hlist_del_rcu(&(entry->ksym_hlist));
 274                 synchronize_rcu();
 275                 kfree(entry->ksym_hbp->info.name);
 276                 kfree(entry->ksym_hbp);
 277                 kfree(entry);
 278         }
 279         mutex_unlock(&ksym_tracer_mutex);
 280 }
 281
 282 static ssize_t ksym_trace_filter_write(struct file *file,
 283                                         const char __user *buffer,
 284                                                 size_t count, loff_t *ppos)
 285 {
 286         struct trace_ksym *entry;
 287         struct hlist_node *node;
 288         char *input_string, *ksymname = NULL;
 289         unsigned long ksym_addr = 0;
 290         int ret, op, changed = 0;
 291
 292         input_string = kzalloc(count + 1, GFP_KERNEL);
 293         if (!input_string)
 294                 return -ENOMEM;
 295
 296         if (copy_from_user(input_string, buffer, count)) {
 297                 kfree(input_string);
 298                 return -EFAULT;
 299         }
 300         input_string[count] = '\0';
 301
 302         strstrip(input_string);
 303
 304         /*
 305          * Clear all breakpoints if:
 306          * 1: echo > ksym_trace_filter
 307          * 2: echo 0 > ksym_trace_filter
 308          * 3: echo "*:---" > ksym_trace_filter
 309          */
 310         if (!input_string[0] || !strcmp(input_string, "0") ||
 311             !strcmp(input_string, "*:---")) {
 312                 __ksym_trace_reset();
 313                 kfree(input_string);
 314                 return count;
 315         }
 316
 317         ret = op = parse_ksym_trace_str(input_string, &ksymname, &ksym_addr);
 318         if (ret < 0) {
 319                 kfree(input_string);
 320                 return ret;
 321         }
 322
 323         mutex_lock(&ksym_tracer_mutex);
 324
 325         ret = -EINVAL;
 326         hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) {
 327                 if (entry->ksym_addr == ksym_addr) {
 328                         /* Check for malformed request: (6) */
 329                         if (entry->ksym_hbp->info.type != op)
 330                                 changed = 1;
 331                         else
 332                                 goto out;
 333                         break;
 334                 }
 335         }
 336         if (changed) {
 337                 unregister_kernel_hw_breakpoint(entry->ksym_hbp);
 338                 entry->ksym_hbp->info.type = op;
 339                 if (op > 0) {
 340                         ret = register_kernel_hw_breakpoint(entry->ksym_hbp);
 341                         if (ret == 0)
 342                                 goto out;
 343                 }
 344                 ksym_filter_entry_count--;
 345                 hlist_del_rcu(&(entry->ksym_hlist));
 346                 synchronize_rcu();
 347                 kfree(entry->ksym_hbp->info.name);
 348                 kfree(entry->ksym_hbp);
 349                 kfree(entry);
 350                 ret = 0;
 351                 goto out;
 352         } else {
 353                 /* Check for malformed request: (4) */
 354                 if (op == 0)
 355                         goto out;
 356                 ret = process_new_ksym_entry(ksymname, op, ksym_addr);
 357         }
 358 out:
 359         mutex_unlock(&ksym_tracer_mutex);
 360
 361         kfree(input_string);
 362
 363         if (!ret)
 364                 ret = count;
 365         return ret;
 366 }
 367
 368 static const struct file_operations ksym_tracing_fops = {
 369         .open           = tracing_open_generic,
 370         .read           = ksym_trace_filter_read,
 371         .write          = ksym_trace_filter_write,
 372 };
 373
 374 static void ksym_trace_reset(struct trace_array *tr)
 375 {
 376         ksym_tracing_enabled = 0;
 377         __ksym_trace_reset();
 378 }
 379
 380 static int ksym_trace_init(struct trace_array *tr)
 381 {
 382         int cpu, ret = 0;
 383
 384         for_each_online_cpu(cpu)
 385                 tracing_reset(tr, cpu);
 386         ksym_tracing_enabled = 1;
 387         ksym_trace_array = tr;
 388
 389         return ret;
 390 }
 391
 392 static void ksym_trace_print_header(struct seq_file *m)
 393 {
 394         seq_puts(m,
 395                  "#       TASK-PID   CPU#      Symbol                    "
 396                  "Type    Function\n");
 397         seq_puts(m,
 398                  "#          |        |          |                       "
 399                  " |         |\n");
 400 }
 401
 402 static enum print_line_t ksym_trace_output(struct trace_iterator *iter)
 403 {
 404         struct trace_entry *entry = iter->ent;
 405         struct trace_seq *s = &iter->seq;
 406         struct ksym_trace_entry *field;
 407         char str[KSYM_SYMBOL_LEN];
 408         int ret;
 409
 410         if (entry->type != TRACE_KSYM)
 411                 return TRACE_TYPE_UNHANDLED;
 412
 413         trace_assign_type(field, entry);
 414
 415         ret = trace_seq_printf(s, "%11s-%-5d [%03d] %-30s ", field->cmd,
 416                                 entry->pid, iter->cpu, field->ksym_name);
 417         if (!ret)
 418                 return TRACE_TYPE_PARTIAL_LINE;
 419
 420         switch (field->type) {
 421         case HW_BREAKPOINT_WRITE:
 422                 ret = trace_seq_printf(s, " W  ");
 423                 break;
 424         case HW_BREAKPOINT_RW:
 425                 ret = trace_seq_printf(s, " RW ");
 426                 break;
 427         default:
 428                 return TRACE_TYPE_PARTIAL_LINE;
 429         }
 430
 431         if (!ret)
 432                 return TRACE_TYPE_PARTIAL_LINE;
 433
 434         sprint_symbol(str, field->ip);
 435         ret = trace_seq_printf(s, "%s\n", str);
 436         if (!ret)
 437                 return TRACE_TYPE_PARTIAL_LINE;
 438
 439         return TRACE_TYPE_HANDLED;
 440 }
 441
 442 struct tracer ksym_tracer __read_mostly =
 443 {
 444         .name           = "ksym_tracer",
 445         .init           = ksym_trace_init,
 446         .reset          = ksym_trace_reset,
 447 #ifdef CONFIG_FTRACE_SELFTEST
 448         .selftest       = trace_selftest_startup_ksym,
 449 #endif
 450         .print_header   = ksym_trace_print_header,
 451         .print_line     = ksym_trace_output
 452 };
 453
 454 __init static int init_ksym_trace(void)
 455 {
 456         struct dentry *d_tracer;
 457         struct dentry *entry;
 458
 459         d_tracer = tracing_init_dentry();
 460         ksym_filter_entry_count = 0;
 461
 462         entry = debugfs_create_file("ksym_trace_filter", 0644, d_tracer,
 463                                     NULL, &ksym_tracing_fops);
 464         if (!entry)
 465                 pr_warning("Could not create debugfs "
 466                            "'ksym_trace_filter' file\n");
 467
 468         return register_tracer(&ksym_tracer);
 469 }
 470 device_initcall(init_ksym_trace);
 471
 472
 473 #ifdef CONFIG_PROFILE_KSYM_TRACER
 474 static int ksym_tracer_stat_headers(struct seq_file *m)
 475 {
 476         seq_puts(m, "  Access Type ");
 477         seq_puts(m, "  Symbol                                       Counter\n");
 478         seq_puts(m, "  ----------- ");
 479         seq_puts(m, "  ------                                       -------\n");
 480         return 0;
 481 }
 482
 483 static int ksym_tracer_stat_show(struct seq_file *m, void *v)
 484 {
 485         struct hlist_node *stat = v;
 486         struct trace_ksym *entry;
 487         int access_type = 0;
 488         char fn_name[KSYM_NAME_LEN];
 489
 490         entry = hlist_entry(stat, struct trace_ksym, ksym_hlist);
 491
 492         if (entry->ksym_hbp)
 493                 access_type = entry->ksym_hbp->info.type;
 494
 495         switch (access_type) {
 496         case HW_BREAKPOINT_WRITE:
 497                 seq_puts(m, "  W           ");
 498                 break;
 499         case HW_BREAKPOINT_RW:
 500                 seq_puts(m, "  RW          ");
 501                 break;
 502         default:
 503                 seq_puts(m, "  NA          ");
 504         }
 505
 506         if (lookup_symbol_name(entry->ksym_addr, fn_name) >= 0)
 507                 seq_printf(m, "  %-36s", fn_name);
 508         else
 509                 seq_printf(m, "  %-36s", "<NA>");
 510         seq_printf(m, " %15lu\n", entry->counter);
 511
 512         return 0;
 513 }
 514
 515 static void *ksym_tracer_stat_start(struct tracer_stat *trace)
 516 {
 517         return ksym_filter_head.first;
 518 }
 519
 520 static void *
 521 ksym_tracer_stat_next(void *v, int idx)
 522 {
 523         struct hlist_node *stat = v;
 524
 525         return stat->next;
 526 }
 527
 528 static struct tracer_stat ksym_tracer_stats = {
 529         .name = "ksym_tracer",
 530         .stat_start = ksym_tracer_stat_start,
 531         .stat_next = ksym_tracer_stat_next,
 532         .stat_headers = ksym_tracer_stat_headers,
 533         .stat_show = ksym_tracer_stat_show
 534 };
 535
 536 __init static int ksym_tracer_stat_init(void)
 537 {
 538         int ret;
 539
 540         ret = register_stat_tracer(&ksym_tracer_stats);
 541         if (ret) {
 542                 printk(KERN_WARNING "Warning: could not register "
 543                                     "ksym tracer stats\n");
 544                 return 1;
 545         }
 546
 547         return 0;
 548 }
 549 fs_initcall(ksym_tracer_stat_init);
 550 #endif /* CONFIG_PROFILE_KSYM_TRACER */