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         struct perf_event_attr  attr;
  46 #ifdef CONFIG_PROFILE_KSYM_TRACER
  47         unsigned long           counter;
  48 #endif
  49         struct hlist_node       ksym_hlist;
  50 };
  51
  52 static struct trace_array *ksym_trace_array;
  53
  54 static unsigned int ksym_filter_entry_count;
  55 static unsigned int ksym_tracing_enabled;
  56
  57 static HLIST_HEAD(ksym_filter_head);
  58
  59 static DEFINE_MUTEX(ksym_tracer_mutex);
  60
  61 #ifdef CONFIG_PROFILE_KSYM_TRACER
  62
  63 #define MAX_UL_INT 0xffffffff
  64
  65 void ksym_collect_stats(unsigned long hbp_hit_addr)
  66 {
  67         struct hlist_node *node;
  68         struct trace_ksym *entry;
  69
  70         rcu_read_lock();
  71         hlist_for_each_entry_rcu(entry, node, &ksym_filter_head, ksym_hlist) {
  72                 if ((entry->attr.bp_addr == hbp_hit_addr) &&
  73                     (entry->counter <= MAX_UL_INT)) {
  74                         entry->counter++;
  75                         break;
  76                 }
  77         }
  78         rcu_read_unlock();
  79 }
  80 #endif /* CONFIG_PROFILE_KSYM_TRACER */
  81
  82 void ksym_hbp_handler(struct perf_event *hbp, int nmi,
  83                       struct perf_sample_data *data,
  84                       struct pt_regs *regs)
  85 {
  86         struct ring_buffer_event *event;
  87         struct ksym_trace_entry *entry;
  88         struct ring_buffer *buffer;
  89         int pc;
  90
  91         if (!ksym_tracing_enabled)
  92                 return;
  93
  94         buffer = ksym_trace_array->buffer;
  95
  96         pc = preempt_count();
  97
  98         event = trace_buffer_lock_reserve(buffer, TRACE_KSYM,
  99                                                         sizeof(*entry), 0, pc);
 100         if (!event)
 101                 return;
 102
 103         entry           = ring_buffer_event_data(event);
 104         entry->ip       = instruction_pointer(regs);
 105         entry->type     = hw_breakpoint_type(hbp);
 106         entry->addr     = hw_breakpoint_addr(hbp);
 107         strlcpy(entry->cmd, current->comm, TASK_COMM_LEN);
 108
 109 #ifdef CONFIG_PROFILE_KSYM_TRACER
 110         ksym_collect_stats(hw_breakpoint_addr(hbp));
 111 #endif /* CONFIG_PROFILE_KSYM_TRACER */
 112
 113         trace_buffer_unlock_commit(buffer, event, 0, pc);
 114 }
 115
 116 /* Valid access types are represented as
 117  *
 118  * rw- : Set Read/Write Access Breakpoint
 119  * -w- : Set Write Access Breakpoint
 120  * --- : Clear Breakpoints
 121  * --x : Set Execution Break points (Not available yet)
 122  *
 123  */
 124 static int ksym_trace_get_access_type(char *str)
 125 {
 126         int access = 0;
 127
 128         if (str[0] == 'r')
 129                 access |= HW_BREAKPOINT_R;
 130
 131         if (str[1] == 'w')
 132                 access |= HW_BREAKPOINT_W;
 133
 134         if (str[2] == 'x')
 135                 access |= HW_BREAKPOINT_X;
 136
 137         switch (access) {
 138         case HW_BREAKPOINT_R:
 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         hw_breakpoint_init(&entry->attr);
 195
 196         entry->attr.bp_type = op;
 197         entry->attr.bp_addr = addr;
 198         entry->attr.bp_len = HW_BREAKPOINT_LEN_4;
 199
 200         ret = -EAGAIN;
 201         entry->ksym_hbp = register_wide_hw_breakpoint(&entry->attr,
 202                                         ksym_hbp_handler);
 203
 204         if (IS_ERR(entry->ksym_hbp)) {
 205                 ret = PTR_ERR(entry->ksym_hbp);
 206                 printk(KERN_INFO "ksym_tracer request failed. Try again"
 207                                         " later!!\n");
 208                 goto err;
 209         }
 210
 211         hlist_add_head_rcu(&(entry->ksym_hlist), &ksym_filter_head);
 212         ksym_filter_entry_count++;
 213
 214         return 0;
 215
 216 err:
 217         kfree(entry);
 218
 219         return ret;
 220 }
 221
 222 static ssize_t ksym_trace_filter_read(struct file *filp, char __user *ubuf,
 223                                                 size_t count, loff_t *ppos)
 224 {
 225         struct trace_ksym *entry;
 226         struct hlist_node *node;
 227         struct trace_seq *s;
 228         ssize_t cnt = 0;
 229         int ret;
 230
 231         s = kmalloc(sizeof(*s), GFP_KERNEL);
 232         if (!s)
 233                 return -ENOMEM;
 234         trace_seq_init(s);
 235
 236         mutex_lock(&ksym_tracer_mutex);
 237
 238         hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) {
 239                 ret = trace_seq_printf(s, "%pS:",
 240                                 (void *)(unsigned long)entry->attr.bp_addr);
 241                 if (entry->attr.bp_type == HW_BREAKPOINT_R)
 242                         ret = trace_seq_puts(s, "r--\n");
 243                 else if (entry->attr.bp_type == HW_BREAKPOINT_W)
 244                         ret = trace_seq_puts(s, "-w-\n");
 245                 else if (entry->attr.bp_type == (HW_BREAKPOINT_W | HW_BREAKPOINT_R))
 246                         ret = trace_seq_puts(s, "rw-\n");
 247                 WARN_ON_ONCE(!ret);
 248         }
 249
 250         cnt = simple_read_from_buffer(ubuf, count, ppos, s->buffer, s->len);
 251
 252         mutex_unlock(&ksym_tracer_mutex);
 253
 254         kfree(s);
 255
 256         return cnt;
 257 }
 258
 259 static void __ksym_trace_reset(void)
 260 {
 261         struct trace_ksym *entry;
 262         struct hlist_node *node, *node1;
 263
 264         mutex_lock(&ksym_tracer_mutex);
 265         hlist_for_each_entry_safe(entry, node, node1, &ksym_filter_head,
 266                                                                 ksym_hlist) {
 267                 unregister_wide_hw_breakpoint(entry->ksym_hbp);
 268                 ksym_filter_entry_count--;
 269                 hlist_del_rcu(&(entry->ksym_hlist));
 270                 synchronize_rcu();
 271                 kfree(entry);
 272         }
 273         mutex_unlock(&ksym_tracer_mutex);
 274 }
 275
 276 static ssize_t ksym_trace_filter_write(struct file *file,
 277                                         const char __user *buffer,
 278                                                 size_t count, loff_t *ppos)
 279 {
 280         struct trace_ksym *entry;
 281         struct hlist_node *node;
 282         char *buf, *input_string, *ksymname = NULL;
 283         unsigned long ksym_addr = 0;
 284         int ret, op, changed = 0;
 285
 286         buf = kzalloc(count + 1, GFP_KERNEL);
 287         if (!buf)
 288                 return -ENOMEM;
 289
 290         ret = -EFAULT;
 291         if (copy_from_user(buf, buffer, count))
 292                 goto out;
 293
 294         buf[count] = '\0';
 295         input_string = strstrip(buf);
 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 (!buf[0] || !strcmp(buf, "0") ||
 304             !strcmp(buf, "*:---")) {
 305                 __ksym_trace_reset();
 306                 ret = 0;
 307                 goto out;
 308         }
 309
 310         ret = op = parse_ksym_trace_str(input_string, &ksymname, &ksym_addr);
 311         if (ret < 0)
 312                 goto out;
 313
 314         mutex_lock(&ksym_tracer_mutex);
 315
 316         ret = -EINVAL;
 317         hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) {
 318                 if (entry->attr.bp_addr == ksym_addr) {
 319                         /* Check for malformed request: (6) */
 320                         if (entry->attr.bp_type != op)
 321                                 changed = 1;
 322                         else
 323                                 goto out_unlock;
 324                         break;
 325                 }
 326         }
 327         if (changed) {
 328                 unregister_wide_hw_breakpoint(entry->ksym_hbp);
 329                 entry->attr.bp_type = op;
 330                 ret = 0;
 331                 if (op > 0) {
 332                         entry->ksym_hbp =
 333                                 register_wide_hw_breakpoint(&entry->attr,
 334                                         ksym_hbp_handler);
 335                         if (IS_ERR(entry->ksym_hbp))
 336                                 ret = PTR_ERR(entry->ksym_hbp);
 337                         else
 338                                 goto out_unlock;
 339                 }
 340                 /* Error or "symbol:---" case: drop it */
 341                 ksym_filter_entry_count--;
 342                 hlist_del_rcu(&(entry->ksym_hlist));
 343                 synchronize_rcu();
 344                 kfree(entry);
 345                 goto out_unlock;
 346         } else {
 347                 /* Check for malformed request: (4) */
 348                 if (op)
 349                         ret = process_new_ksym_entry(ksymname, op, ksym_addr);
 350         }
 351 out_unlock:
 352         mutex_unlock(&ksym_tracer_mutex);
 353 out:
 354         kfree(buf);
 355         return !ret ? count : ret;
 356 }
 357
 358 static const struct file_operations ksym_tracing_fops = {
 359         .open           = tracing_open_generic,
 360         .read           = ksym_trace_filter_read,
 361         .write          = ksym_trace_filter_write,
 362 };
 363
 364 static void ksym_trace_reset(struct trace_array *tr)
 365 {
 366         ksym_tracing_enabled = 0;
 367         __ksym_trace_reset();
 368 }
 369
 370 static int ksym_trace_init(struct trace_array *tr)
 371 {
 372         int cpu, ret = 0;
 373
 374         for_each_online_cpu(cpu)
 375                 tracing_reset(tr, cpu);
 376         ksym_tracing_enabled = 1;
 377         ksym_trace_array = tr;
 378
 379         return ret;
 380 }
 381
 382 static void ksym_trace_print_header(struct seq_file *m)
 383 {
 384         seq_puts(m,
 385                  "#       TASK-PID   CPU#      Symbol                    "
 386                  "Type    Function\n");
 387         seq_puts(m,
 388                  "#          |        |          |                       "
 389                  " |         |\n");
 390 }
 391
 392 static enum print_line_t ksym_trace_output(struct trace_iterator *iter)
 393 {
 394         struct trace_entry *entry = iter->ent;
 395         struct trace_seq *s = &iter->seq;
 396         struct ksym_trace_entry *field;
 397         char str[KSYM_SYMBOL_LEN];
 398         int ret;
 399
 400         if (entry->type != TRACE_KSYM)
 401                 return TRACE_TYPE_UNHANDLED;
 402
 403         trace_assign_type(field, entry);
 404
 405         ret = trace_seq_printf(s, "%11s-%-5d [%03d] %pS", field->cmd,
 406                                 entry->pid, iter->cpu, (char *)field->addr);
 407         if (!ret)
 408                 return TRACE_TYPE_PARTIAL_LINE;
 409
 410         switch (field->type) {
 411         case HW_BREAKPOINT_R:
 412                 ret = trace_seq_printf(s, " R  ");
 413                 break;
 414         case HW_BREAKPOINT_W:
 415                 ret = trace_seq_printf(s, " W  ");
 416                 break;
 417         case HW_BREAKPOINT_R | HW_BREAKPOINT_W:
 418                 ret = trace_seq_printf(s, " RW ");
 419                 break;
 420         default:
 421                 return TRACE_TYPE_PARTIAL_LINE;
 422         }
 423
 424         if (!ret)
 425                 return TRACE_TYPE_PARTIAL_LINE;
 426
 427         sprint_symbol(str, field->ip);
 428         ret = trace_seq_printf(s, "%s\n", str);
 429         if (!ret)
 430                 return TRACE_TYPE_PARTIAL_LINE;
 431
 432         return TRACE_TYPE_HANDLED;
 433 }
 434
 435 struct tracer ksym_tracer __read_mostly =
 436 {
 437         .name           = "ksym_tracer",
 438         .init           = ksym_trace_init,
 439         .reset          = ksym_trace_reset,
 440 #ifdef CONFIG_FTRACE_SELFTEST
 441         .selftest       = trace_selftest_startup_ksym,
 442 #endif
 443         .print_header   = ksym_trace_print_header,
 444         .print_line     = ksym_trace_output
 445 };
 446
 447 __init static int init_ksym_trace(void)
 448 {
 449         struct dentry *d_tracer;
 450         struct dentry *entry;
 451
 452         d_tracer = tracing_init_dentry();
 453         ksym_filter_entry_count = 0;
 454
 455         entry = debugfs_create_file("ksym_trace_filter", 0644, d_tracer,
 456                                     NULL, &ksym_tracing_fops);
 457         if (!entry)
 458                 pr_warning("Could not create debugfs "
 459                            "'ksym_trace_filter' file\n");
 460
 461         return register_tracer(&ksym_tracer);
 462 }
 463 device_initcall(init_ksym_trace);
 464
 465
 466 #ifdef CONFIG_PROFILE_KSYM_TRACER
 467 static int ksym_tracer_stat_headers(struct seq_file *m)
 468 {
 469         seq_puts(m, "  Access Type ");
 470         seq_puts(m, "  Symbol                                       Counter\n");
 471         seq_puts(m, "  ----------- ");
 472         seq_puts(m, "  ------                                       -------\n");
 473         return 0;
 474 }
 475
 476 static int ksym_tracer_stat_show(struct seq_file *m, void *v)
 477 {
 478         struct hlist_node *stat = v;
 479         struct trace_ksym *entry;
 480         int access_type = 0;
 481         char fn_name[KSYM_NAME_LEN];
 482
 483         entry = hlist_entry(stat, struct trace_ksym, ksym_hlist);
 484
 485         access_type = entry->attr.bp_type;
 486
 487         switch (access_type) {
 488         case HW_BREAKPOINT_R:
 489                 seq_puts(m, "  R           ");
 490                 break;
 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->attr.bp_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 */