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/slab.h>
  27 #include <linux/fs.h>
  28
  29 #include "trace_output.h"
  30 #include "trace.h"
  31
  32 #include <linux/hw_breakpoint.h>
  33 #include <asm/hw_breakpoint.h>
  34
  35 #include <asm/atomic.h>
  36
  37 /*
  38  * For now, let us restrict the no. of symbols traced simultaneously to number
  39  * of available hardware breakpoint registers.
  40  */
  41 #define KSYM_TRACER_MAX HBP_NUM
  42
  43 #define KSYM_TRACER_OP_LEN 3 /* rw- */
  44
  45 struct trace_ksym {
  46         struct perf_event       **ksym_hbp;
  47         struct perf_event_attr  attr;
  48 #ifdef CONFIG_PROFILE_KSYM_TRACER
  49         atomic64_t              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->attr.bp_addr == hbp_hit_addr) {
  75                         atomic64_inc(&entry->counter);
  76                         break;
  77                 }
  78         }
  79         rcu_read_unlock();
  80 }
  81 #endif /* CONFIG_PROFILE_KSYM_TRACER */
  82
  83 void ksym_hbp_handler(struct perf_event *hbp, int nmi,
  84                       struct perf_sample_data *data,
  85                       struct pt_regs *regs)
  86 {
  87         struct ring_buffer_event *event;
  88         struct ksym_trace_entry *entry;
  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_R:
 140         case HW_BREAKPOINT_W:
 141         case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
 142                 return access;
 143         default:
 144                 return -EINVAL;
 145         }
 146 }
 147
 148 /*
 149  * There can be several possible malformed requests and we attempt to capture
 150  * all of them. We enumerate some of the rules
 151  * 1. We will not allow kernel symbols with ':' since it is used as a delimiter.
 152  *    i.e. multiple ':' symbols disallowed. Possible uses are of the form
 153  *    <module>:<ksym_name>:<op>.
 154  * 2. No delimiter symbol ':' in the input string
 155  * 3. Spurious operator symbols or symbols not in their respective positions
 156  * 4. <ksym_name>:--- i.e. clear breakpoint request when ksym_name not in file
 157  * 5. Kernel symbol not a part of /proc/kallsyms
 158  * 6. Duplicate requests
 159  */
 160 static int parse_ksym_trace_str(char *input_string, char **ksymname,
 161                                                         unsigned long *addr)
 162 {
 163         int ret;
 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         hw_breakpoint_init(&entry->attr);
 196
 197         entry->attr.bp_type = op;
 198         entry->attr.bp_addr = addr;
 199         entry->attr.bp_len = HW_BREAKPOINT_LEN_4;
 200
 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 (!input_string[0] || !strcmp(input_string, "0") ||
 304             !strcmp(input_string, "*:---")) {
 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 #ifdef CONFIG_PROFILE_KSYM_TRACER
 448 static int ksym_profile_show(struct seq_file *m, void *v)
 449 {
 450         struct hlist_node *node;
 451         struct trace_ksym *entry;
 452         int access_type = 0;
 453         char fn_name[KSYM_NAME_LEN];
 454
 455         seq_puts(m, "  Access Type ");
 456         seq_puts(m, "  Symbol                                       Counter\n");
 457         seq_puts(m, "  ----------- ");
 458         seq_puts(m, "  ------                                       -------\n");
 459
 460         rcu_read_lock();
 461         hlist_for_each_entry_rcu(entry, node, &ksym_filter_head, ksym_hlist) {
 462
 463                 access_type = entry->attr.bp_type;
 464
 465                 switch (access_type) {
 466                 case HW_BREAKPOINT_R:
 467                         seq_puts(m, "  R           ");
 468                         break;
 469                 case HW_BREAKPOINT_W:
 470                         seq_puts(m, "  W           ");
 471                         break;
 472                 case HW_BREAKPOINT_R | HW_BREAKPOINT_W:
 473                         seq_puts(m, "  RW          ");
 474                         break;
 475                 default:
 476                         seq_puts(m, "  NA          ");
 477                 }
 478
 479                 if (lookup_symbol_name(entry->attr.bp_addr, fn_name) >= 0)
 480                         seq_printf(m, "  %-36s", fn_name);
 481                 else
 482                         seq_printf(m, "  %-36s", "<NA>");
 483                 seq_printf(m, " %15llu\n",
 484                            (unsigned long long)atomic64_read(&entry->counter));
 485         }
 486         rcu_read_unlock();
 487
 488         return 0;
 489 }
 490
 491 static int ksym_profile_open(struct inode *node, struct file *file)
 492 {
 493         return single_open(file, ksym_profile_show, NULL);
 494 }
 495
 496 static const struct file_operations ksym_profile_fops = {
 497         .open           = ksym_profile_open,
 498         .read           = seq_read,
 499         .llseek         = seq_lseek,
 500         .release        = single_release,
 501 };
 502 #endif /* CONFIG_PROFILE_KSYM_TRACER */
 503
 504 __init static int init_ksym_trace(void)
 505 {
 506         struct dentry *d_tracer;
 507
 508         d_tracer = tracing_init_dentry();
 509
 510         trace_create_file("ksym_trace_filter", 0644, d_tracer,
 511                           NULL, &ksym_tracing_fops);
 512
 513 #ifdef CONFIG_PROFILE_KSYM_TRACER
 514         trace_create_file("ksym_profile", 0444, d_tracer,
 515                           NULL, &ksym_profile_fops);
 516 #endif
 517
 518         return register_tracer(&ksym_tracer);
 519 }
 520 device_initcall(init_ksym_trace);