SAFE public projects git trees. - safe/jmp/linux-2.6/blob - 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 2:
 139                 access = HW_BREAKPOINT_WRITE;
 140                 break;
 141         }
 142
 143         return access;
 144 }
 145
 146 /*
 147  * There can be several possible malformed requests and we attempt to capture
 148  * all of them. We enumerate some of the rules
 149  * 1. We will not allow kernel symbols with ':' since it is used as a delimiter.
 150  *    i.e. multiple ':' symbols disallowed. Possible uses are of the form
 151  *    <module>:<ksym_name>:<op>.
 152  * 2. No delimiter symbol ':' in the input string
 153  * 3. Spurious operator symbols or symbols not in their respective positions
 154  * 4. <ksym_name>:--- i.e. clear breakpoint request when ksym_name not in file
 155  * 5. Kernel symbol not a part of /proc/kallsyms
 156  * 6. Duplicate requests
 157  */
 158 static int parse_ksym_trace_str(char *input_string, char **ksymname,
 159                                                         unsigned long *addr)
 160 {
 161         int ret;
 162
 163         strstrip(input_string);
 164
 165         *ksymname = strsep(&input_string, ":");
 166         *addr = kallsyms_lookup_name(*ksymname);
 167
 168         /* Check for malformed request: (2), (1) and (5) */
 169         if ((!input_string) ||
 170             (strlen(input_string) != KSYM_TRACER_OP_LEN) ||
 171             (*addr == 0))
 172                 return -EINVAL;;
 173
 174         ret = ksym_trace_get_access_type(input_string);
 175
 176         return ret;
 177 }
 178
 179 int process_new_ksym_entry(char *ksymname, int op, unsigned long addr)
 180 {
 181         struct trace_ksym *entry;
 182         int ret = -ENOMEM;
 183
 184         if (ksym_filter_entry_count >= KSYM_TRACER_MAX) {
 185                 printk(KERN_ERR "ksym_tracer: Maximum limit:(%d) reached. No"
 186                 " new requests for tracing can be accepted now.\n",
 187                         KSYM_TRACER_MAX);
 188                 return -ENOSPC;
 189         }
 190
 191         entry = kzalloc(sizeof(struct trace_ksym), GFP_KERNEL);
 192         if (!entry)
 193                 return -ENOMEM;
 194
 195         entry->ksym_hbp = kzalloc(sizeof(struct hw_breakpoint), GFP_KERNEL);
 196         if (!entry->ksym_hbp)
 197                 goto err;
 198
 199         entry->ksym_hbp->info.name = kstrdup(ksymname, GFP_KERNEL);
 200         if (!entry->ksym_hbp->info.name)
 201                 goto err;
 202
 203         entry->ksym_hbp->info.type = op;
 204         entry->ksym_addr = entry->ksym_hbp->info.address = addr;
 205 #ifdef CONFIG_X86
 206         entry->ksym_hbp->info.len = HW_BREAKPOINT_LEN_4;
 207 #endif
 208         entry->ksym_hbp->triggered = (void *)ksym_hbp_handler;
 209
 210         ret = register_kernel_hw_breakpoint(entry->ksym_hbp);
 211         if (ret < 0) {
 212                 printk(KERN_INFO "ksym_tracer request failed. Try again"
 213                                         " later!!\n");
 214                 ret = -EAGAIN;
 215                 goto err;
 216         }
 217         hlist_add_head_rcu(&(entry->ksym_hlist), &ksym_filter_head);
 218         ksym_filter_entry_count++;
 219         return 0;
 220 err:
 221         if (entry->ksym_hbp)
 222                 kfree(entry->ksym_hbp->info.name);
 223         kfree(entry->ksym_hbp);
 224         kfree(entry);
 225         return ret;
 226 }
 227
 228 static ssize_t ksym_trace_filter_read(struct file *filp, char __user *ubuf,
 229                                                 size_t count, loff_t *ppos)
 230 {
 231         struct trace_ksym *entry;
 232         struct hlist_node *node;
 233         struct trace_seq *s;
 234         ssize_t cnt = 0;
 235         int ret;
 236
 237         s = kmalloc(sizeof(*s), GFP_KERNEL);
 238         if (!s)
 239                 return -ENOMEM;
 240         trace_seq_init(s);
 241
 242         mutex_lock(&ksym_tracer_mutex);
 243
 244         hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) {
 245                 ret = trace_seq_printf(s, "%s:", entry->ksym_hbp->info.name);
 246                 if (entry->ksym_hbp->info.type == HW_BREAKPOINT_WRITE)
 247                         ret = trace_seq_puts(s, "-w-\n");
 248                 else if (entry->ksym_hbp->info.type == HW_BREAKPOINT_RW)
 249                         ret = trace_seq_puts(s, "rw-\n");
 250                 WARN_ON_ONCE(!ret);
 251         }
 252
 253         cnt = simple_read_from_buffer(ubuf, count, ppos, s->buffer, s->len);
 254
 255         mutex_unlock(&ksym_tracer_mutex);
 256
 257         kfree(s);
 258
 259         return cnt;
 260 }
 261
 262 static ssize_t ksym_trace_filter_write(struct file *file,
 263                                         const char __user *buffer,
 264                                                 size_t count, loff_t *ppos)
 265 {
 266         struct trace_ksym *entry;
 267         struct hlist_node *node;
 268         char *input_string, *ksymname = NULL;
 269         unsigned long ksym_addr = 0;
 270         int ret, op, changed = 0;
 271
 272         input_string = kzalloc(count + 1, GFP_KERNEL);
 273         if (!input_string)
 274                 return -ENOMEM;
 275
 276         if (copy_from_user(input_string, buffer, count)) {
 277                 kfree(input_string);
 278                 return -EFAULT;
 279         }
 280         input_string[count] = '\0';
 281
 282         ret = op = parse_ksym_trace_str(input_string, &ksymname, &ksym_addr);
 283         if (ret < 0) {
 284                 kfree(input_string);
 285                 return ret;
 286         }
 287
 288         mutex_lock(&ksym_tracer_mutex);
 289
 290         ret = -EINVAL;
 291         hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) {
 292                 if (entry->ksym_addr == ksym_addr) {
 293                         /* Check for malformed request: (6) */
 294                         if (entry->ksym_hbp->info.type != op)
 295                                 changed = 1;
 296                         else
 297                                 goto out;
 298                         break;
 299                 }
 300         }
 301         if (changed) {
 302                 unregister_kernel_hw_breakpoint(entry->ksym_hbp);
 303                 entry->ksym_hbp->info.type = op;
 304                 if (op > 0) {
 305                         ret = register_kernel_hw_breakpoint(entry->ksym_hbp);
 306                         if (ret == 0)
 307                                 goto out;
 308                 }
 309                 ksym_filter_entry_count--;
 310                 hlist_del_rcu(&(entry->ksym_hlist));
 311                 synchronize_rcu();
 312                 kfree(entry->ksym_hbp->info.name);
 313                 kfree(entry->ksym_hbp);
 314                 kfree(entry);
 315                 goto out;
 316         } else {
 317                 /* Check for malformed request: (4) */
 318                 if (op == 0)
 319                         goto out;
 320                 ret = process_new_ksym_entry(ksymname, op, ksym_addr);
 321         }
 322 out:
 323         mutex_unlock(&ksym_tracer_mutex);
 324
 325         kfree(input_string);
 326
 327         if (!ret)
 328                 ret = count;
 329         return ret;
 330 }
 331
 332 static const struct file_operations ksym_tracing_fops = {
 333         .open           = tracing_open_generic,
 334         .read           = ksym_trace_filter_read,
 335         .write          = ksym_trace_filter_write,
 336 };
 337
 338 static void ksym_trace_reset(struct trace_array *tr)
 339 {
 340         struct trace_ksym *entry;
 341         struct hlist_node *node, *node1;
 342
 343         ksym_tracing_enabled = 0;
 344
 345         mutex_lock(&ksym_tracer_mutex);
 346         hlist_for_each_entry_safe(entry, node, node1, &ksym_filter_head,
 347                                                                 ksym_hlist) {
 348                 unregister_kernel_hw_breakpoint(entry->ksym_hbp);
 349                 ksym_filter_entry_count--;
 350                 hlist_del_rcu(&(entry->ksym_hlist));
 351                 synchronize_rcu();
 352                 kfree(entry->ksym_hbp->info.name);
 353                 kfree(entry->ksym_hbp);
 354                 kfree(entry);
 355         }
 356         mutex_unlock(&ksym_tracer_mutex);
 357 }
 358
 359 static int ksym_trace_init(struct trace_array *tr)
 360 {
 361         int cpu, ret = 0;
 362
 363         for_each_online_cpu(cpu)
 364                 tracing_reset(tr, cpu);
 365         ksym_tracing_enabled = 1;
 366         ksym_trace_array = tr;
 367
 368         return ret;
 369 }
 370
 371 static void ksym_trace_print_header(struct seq_file *m)
 372 {
 373
 374         seq_puts(m,
 375                  "#       TASK-PID      CPU#      Symbol         Type    "
 376                  "Function         \n");
 377         seq_puts(m,
 378                  "#          |           |          |              |         "
 379                  "|            \n");
 380 }
 381
 382 static enum print_line_t ksym_trace_output(struct trace_iterator *iter)
 383 {
 384         struct trace_entry *entry = iter->ent;
 385         struct trace_seq *s = &iter->seq;
 386         struct ksym_trace_entry *field;
 387         char str[KSYM_SYMBOL_LEN];
 388         int ret;
 389
 390         if (entry->type != TRACE_KSYM)
 391                 return TRACE_TYPE_UNHANDLED;
 392
 393         trace_assign_type(field, entry);
 394
 395         ret = trace_seq_printf(s, "%-15s %-5d %-3d %-20s ", field->cmd,
 396                                 entry->pid, iter->cpu, field->ksym_name);
 397         if (!ret)
 398                 return TRACE_TYPE_PARTIAL_LINE;
 399
 400         switch (field->type) {
 401         case HW_BREAKPOINT_WRITE:
 402                 ret = trace_seq_printf(s, " W  ");
 403                 break;
 404         case HW_BREAKPOINT_RW:
 405                 ret = trace_seq_printf(s, " RW ");
 406                 break;
 407         default:
 408                 return TRACE_TYPE_PARTIAL_LINE;
 409         }
 410
 411         if (!ret)
 412                 return TRACE_TYPE_PARTIAL_LINE;
 413
 414         sprint_symbol(str, field->ip);
 415         ret = trace_seq_printf(s, "%-20s\n", str);
 416         if (!ret)
 417                 return TRACE_TYPE_PARTIAL_LINE;
 418
 419         return TRACE_TYPE_HANDLED;
 420 }
 421
 422 struct tracer ksym_tracer __read_mostly =
 423 {
 424         .name           = "ksym_tracer",
 425         .init           = ksym_trace_init,
 426         .reset          = ksym_trace_reset,
 427 #ifdef CONFIG_FTRACE_SELFTEST
 428         .selftest       = trace_selftest_startup_ksym,
 429 #endif
 430         .print_header   = ksym_trace_print_header,
 431         .print_line     = ksym_trace_output
 432 };
 433
 434 __init static int init_ksym_trace(void)
 435 {
 436         struct dentry *d_tracer;
 437         struct dentry *entry;
 438
 439         d_tracer = tracing_init_dentry();
 440         ksym_filter_entry_count = 0;
 441
 442         entry = debugfs_create_file("ksym_trace_filter", 0644, d_tracer,
 443                                     NULL, &ksym_tracing_fops);
 444         if (!entry)
 445                 pr_warning("Could not create debugfs "
 446                            "'ksym_trace_filter' file\n");
 447
 448         return register_tracer(&ksym_tracer);
 449 }
 450 device_initcall(init_ksym_trace);
 451
 452
 453 #ifdef CONFIG_PROFILE_KSYM_TRACER
 454 static int ksym_tracer_stat_headers(struct seq_file *m)
 455 {
 456         seq_printf(m, "   Access type    ");
 457         seq_printf(m, "            Symbol                     Counter     \n");
 458         return 0;
 459 }
 460
 461 static int ksym_tracer_stat_show(struct seq_file *m, void *v)
 462 {
 463         struct hlist_node *stat = v;
 464         struct trace_ksym *entry;
 465         int access_type = 0;
 466         char fn_name[KSYM_NAME_LEN];
 467
 468         entry = hlist_entry(stat, struct trace_ksym, ksym_hlist);
 469
 470         if (entry->ksym_hbp)
 471                 access_type = entry->ksym_hbp->info.type;
 472
 473         switch (access_type) {
 474         case HW_BREAKPOINT_WRITE:
 475                 seq_printf(m, "     W     ");
 476                 break;
 477         case HW_BREAKPOINT_RW:
 478                 seq_printf(m, "     RW    ");
 479                 break;
 480         default:
 481                 seq_printf(m, "     NA    ");
 482         }
 483
 484         if (lookup_symbol_name(entry->ksym_addr, fn_name) >= 0)
 485                 seq_printf(m, "               %s                 ", fn_name);
 486         else
 487                 seq_printf(m, "               <NA>                ");
 488
 489         seq_printf(m, "%15lu\n", entry->counter);
 490         return 0;
 491 }
 492
 493 static void *ksym_tracer_stat_start(struct tracer_stat *trace)
 494 {
 495         return &(ksym_filter_head.first);
 496 }
 497
 498 static void *
 499 ksym_tracer_stat_next(void *v, int idx)
 500 {
 501         struct hlist_node *stat = v;
 502
 503         return stat->next;
 504 }
 505
 506 static struct tracer_stat ksym_tracer_stats = {
 507         .name = "ksym_tracer",
 508         .stat_start = ksym_tracer_stat_start,
 509         .stat_next = ksym_tracer_stat_next,
 510         .stat_headers = ksym_tracer_stat_headers,
 511         .stat_show = ksym_tracer_stat_show
 512 };
 513
 514 __init static int ksym_tracer_stat_init(void)
 515 {
 516         int ret;
 517
 518         ret = register_stat_tracer(&ksym_tracer_stats);
 519         if (ret) {
 520                 printk(KERN_WARNING "Warning: could not register "
 521                                     "ksym tracer stats\n");
 522                 return 1;
 523         }
 524
 525         return 0;
 526 }
 527 fs_initcall(ksym_tracer_stat_init);
 528 #endif /* CONFIG_PROFILE_KSYM_TRACER */