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.h"
  30
  31 #include <linux/hw_breakpoint.h>
  32 #include <asm/hw_breakpoint.h>
  33
  34 #include <asm/atomic.h>
  35
  36 /*
  37  * For now, let us restrict the no. of symbols traced simultaneously to number
  38  * of available hardware breakpoint registers.
  39  */
  40 #define KSYM_TRACER_MAX HBP_NUM
  41
  42 #define KSYM_TRACER_OP_LEN 3 /* rw- */
  43
  44 struct trace_ksym {
  45         struct perf_event       **ksym_hbp;
  46         struct perf_event_attr  attr;
  47 #ifdef CONFIG_PROFILE_KSYM_TRACER
  48         atomic64_t              counter;
  49 #endif
  50         struct hlist_node       ksym_hlist;
  51 };
  52
  53 static struct trace_array *ksym_trace_array;
  54
  55 static unsigned int ksym_filter_entry_count;
  56 static unsigned int ksym_tracing_enabled;
  57
  58 static HLIST_HEAD(ksym_filter_head);
  59
  60 static DEFINE_MUTEX(ksym_tracer_mutex);
  61
  62 #ifdef CONFIG_PROFILE_KSYM_TRACER
  63
  64 #define MAX_UL_INT 0xffffffff
  65
  66 void ksym_collect_stats(unsigned long hbp_hit_addr)
  67 {
  68         struct hlist_node *node;
  69         struct trace_ksym *entry;
  70
  71         rcu_read_lock();
  72         hlist_for_each_entry_rcu(entry, node, &ksym_filter_head, ksym_hlist) {
  73                 if (entry->attr.bp_addr == hbp_hit_addr) {
  74                         atomic64_inc(&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         entry->ksym_hbp = register_wide_hw_breakpoint(&entry->attr,
 201                                         ksym_hbp_handler);
 202
 203         if (IS_ERR(entry->ksym_hbp)) {
 204                 ret = PTR_ERR(entry->ksym_hbp);
 205                 printk(KERN_INFO "ksym_tracer request failed. Try again"
 206                                         " later!!\n");
 207                 goto err;
 208         }
 209
 210         hlist_add_head_rcu(&(entry->ksym_hlist), &ksym_filter_head);
 211         ksym_filter_entry_count++;
 212
 213         return 0;
 214
 215 err:
 216         kfree(entry);
 217
 218         return ret;
 219 }
 220
 221 static ssize_t ksym_trace_filter_read(struct file *filp, char __user *ubuf,
 222                                                 size_t count, loff_t *ppos)
 223 {
 224         struct trace_ksym *entry;
 225         struct hlist_node *node;
 226         struct trace_seq *s;
 227         ssize_t cnt = 0;
 228         int ret;
 229
 230         s = kmalloc(sizeof(*s), GFP_KERNEL);
 231         if (!s)
 232                 return -ENOMEM;
 233         trace_seq_init(s);
 234
 235         mutex_lock(&ksym_tracer_mutex);
 236
 237         hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) {
 238                 ret = trace_seq_printf(s, "%pS:",
 239                                 (void *)(unsigned long)entry->attr.bp_addr);
 240                 if (entry->attr.bp_type == HW_BREAKPOINT_R)
 241                         ret = trace_seq_puts(s, "r--\n");
 242                 else if (entry->attr.bp_type == HW_BREAKPOINT_W)
 243                         ret = trace_seq_puts(s, "-w-\n");
 244                 else if (entry->attr.bp_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 *buf, *input_string, *ksymname = NULL;
 282         unsigned long ksym_addr = 0;
 283         int ret, op, changed = 0;
 284
 285         buf = kzalloc(count + 1, GFP_KERNEL);
 286         if (!buf)
 287                 return -ENOMEM;
 288
 289         ret = -EFAULT;
 290         if (copy_from_user(buf, buffer, count))
 291                 goto out;
 292
 293         buf[count] = '\0';
 294         input_string = strstrip(buf);
 295
 296         /*
 297          * Clear all breakpoints if:
 298          * 1: echo > ksym_trace_filter
 299          * 2: echo 0 > ksym_trace_filter
 300          * 3: echo "*:---" > ksym_trace_filter
 301          */
 302         if (!input_string[0] || !strcmp(input_string, "0") ||
 303             !strcmp(input_string, "*:---")) {
 304                 __ksym_trace_reset();
 305                 ret = 0;
 306                 goto out;
 307         }
 308
 309         ret = op = parse_ksym_trace_str(input_string, &ksymname, &ksym_addr);
 310         if (ret < 0)
 311                 goto out;
 312
 313         mutex_lock(&ksym_tracer_mutex);
 314
 315         ret = -EINVAL;
 316         hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) {
 317                 if (entry->attr.bp_addr == ksym_addr) {
 318                         /* Check for malformed request: (6) */
 319                         if (entry->attr.bp_type != op)
 320                                 changed = 1;
 321                         else
 322                                 goto out_unlock;
 323                         break;
 324                 }
 325         }
 326         if (changed) {
 327                 unregister_wide_hw_breakpoint(entry->ksym_hbp);
 328                 entry->attr.bp_type = op;
 329                 ret = 0;
 330                 if (op > 0) {
 331                         entry->ksym_hbp =
 332                                 register_wide_hw_breakpoint(&entry->attr,
 333                                         ksym_hbp_handler);
 334                         if (IS_ERR(entry->ksym_hbp))
 335                                 ret = PTR_ERR(entry->ksym_hbp);
 336                         else
 337                                 goto out_unlock;
 338                 }
 339                 /* Error or "symbol:---" case: drop it */
 340                 ksym_filter_entry_count--;
 341                 hlist_del_rcu(&(entry->ksym_hlist));
 342                 synchronize_rcu();
 343                 kfree(entry);
 344                 goto out_unlock;
 345         } else {
 346                 /* Check for malformed request: (4) */
 347                 if (op)
 348                         ret = process_new_ksym_entry(ksymname, op, ksym_addr);
 349         }
 350 out_unlock:
 351         mutex_unlock(&ksym_tracer_mutex);
 352 out:
 353         kfree(buf);
 354         return !ret ? count : ret;
 355 }
 356
 357 static const struct file_operations ksym_tracing_fops = {
 358         .open           = tracing_open_generic,
 359         .read           = ksym_trace_filter_read,
 360         .write          = ksym_trace_filter_write,
 361 };
 362
 363 static void ksym_trace_reset(struct trace_array *tr)
 364 {
 365         ksym_tracing_enabled = 0;
 366         __ksym_trace_reset();
 367 }
 368
 369 static int ksym_trace_init(struct trace_array *tr)
 370 {
 371         int cpu, ret = 0;
 372
 373         for_each_online_cpu(cpu)
 374                 tracing_reset(tr, cpu);
 375         ksym_tracing_enabled = 1;
 376         ksym_trace_array = tr;
 377
 378         return ret;
 379 }
 380
 381 static void ksym_trace_print_header(struct seq_file *m)
 382 {
 383         seq_puts(m,
 384                  "#       TASK-PID   CPU#      Symbol                    "
 385                  "Type    Function\n");
 386         seq_puts(m,
 387                  "#          |        |          |                       "
 388                  " |         |\n");
 389 }
 390
 391 static enum print_line_t ksym_trace_output(struct trace_iterator *iter)
 392 {
 393         struct trace_entry *entry = iter->ent;
 394         struct trace_seq *s = &iter->seq;
 395         struct ksym_trace_entry *field;
 396         char str[KSYM_SYMBOL_LEN];
 397         int ret;
 398
 399         if (entry->type != TRACE_KSYM)
 400                 return TRACE_TYPE_UNHANDLED;
 401
 402         trace_assign_type(field, entry);
 403
 404         ret = trace_seq_printf(s, "%11s-%-5d [%03d] %pS", field->cmd,
 405                                 entry->pid, iter->cpu, (char *)field->addr);
 406         if (!ret)
 407                 return TRACE_TYPE_PARTIAL_LINE;
 408
 409         switch (field->type) {
 410         case HW_BREAKPOINT_R:
 411                 ret = trace_seq_printf(s, " R  ");
 412                 break;
 413         case HW_BREAKPOINT_W:
 414                 ret = trace_seq_printf(s, " W  ");
 415                 break;
 416         case HW_BREAKPOINT_R | HW_BREAKPOINT_W:
 417                 ret = trace_seq_printf(s, " RW ");
 418                 break;
 419         default:
 420                 return TRACE_TYPE_PARTIAL_LINE;
 421         }
 422
 423         if (!ret)
 424                 return TRACE_TYPE_PARTIAL_LINE;
 425
 426         sprint_symbol(str, field->ip);
 427         ret = trace_seq_printf(s, "%s\n", str);
 428         if (!ret)
 429                 return TRACE_TYPE_PARTIAL_LINE;
 430
 431         return TRACE_TYPE_HANDLED;
 432 }
 433
 434 struct tracer ksym_tracer __read_mostly =
 435 {
 436         .name           = "ksym_tracer",
 437         .init           = ksym_trace_init,
 438         .reset          = ksym_trace_reset,
 439 #ifdef CONFIG_FTRACE_SELFTEST
 440         .selftest       = trace_selftest_startup_ksym,
 441 #endif
 442         .print_header   = ksym_trace_print_header,
 443         .print_line     = ksym_trace_output
 444 };
 445
 446 #ifdef CONFIG_PROFILE_KSYM_TRACER
 447 static int ksym_profile_show(struct seq_file *m, void *v)
 448 {
 449         struct hlist_node *node;
 450         struct trace_ksym *entry;
 451         int access_type = 0;
 452         char fn_name[KSYM_NAME_LEN];
 453
 454         seq_puts(m, "  Access Type ");
 455         seq_puts(m, "  Symbol                                       Counter\n");
 456         seq_puts(m, "  ----------- ");
 457         seq_puts(m, "  ------                                       -------\n");
 458
 459         rcu_read_lock();
 460         hlist_for_each_entry_rcu(entry, node, &ksym_filter_head, ksym_hlist) {
 461
 462                 access_type = entry->attr.bp_type;
 463
 464                 switch (access_type) {
 465                 case HW_BREAKPOINT_R:
 466                         seq_puts(m, "  R           ");
 467                         break;
 468                 case HW_BREAKPOINT_W:
 469                         seq_puts(m, "  W           ");
 470                         break;
 471                 case HW_BREAKPOINT_R | HW_BREAKPOINT_W:
 472                         seq_puts(m, "  RW          ");
 473                         break;
 474                 default:
 475                         seq_puts(m, "  NA          ");
 476                 }
 477
 478                 if (lookup_symbol_name(entry->attr.bp_addr, fn_name) >= 0)
 479                         seq_printf(m, "  %-36s", fn_name);
 480                 else
 481                         seq_printf(m, "  %-36s", "<NA>");
 482                 seq_printf(m, " %15llu\n",
 483                            (unsigned long long)atomic64_read(&entry->counter));
 484         }
 485         rcu_read_unlock();
 486
 487         return 0;
 488 }
 489
 490 static int ksym_profile_open(struct inode *node, struct file *file)
 491 {
 492         return single_open(file, ksym_profile_show, NULL);
 493 }
 494
 495 static const struct file_operations ksym_profile_fops = {
 496         .open           = ksym_profile_open,
 497         .read           = seq_read,
 498         .llseek         = seq_lseek,
 499         .release        = single_release,
 500 };
 501 #endif /* CONFIG_PROFILE_KSYM_TRACER */
 502
 503 __init static int init_ksym_trace(void)
 504 {
 505         struct dentry *d_tracer;
 506
 507         d_tracer = tracing_init_dentry();
 508
 509         trace_create_file("ksym_trace_filter", 0644, d_tracer,
 510                           NULL, &ksym_tracing_fops);
 511
 512 #ifdef CONFIG_PROFILE_KSYM_TRACER
 513         trace_create_file("ksym_profile", 0444, d_tracer,
 514                           NULL, &ksym_profile_fops);
 515 #endif
 516
 517         return register_tracer(&ksym_tracer);
 518 }
 519 device_initcall(init_ksym_trace);