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