2 * trace_ksym.c - Kernel Symbol Tracer
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.
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.
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.
18 * Copyright (C) IBM Corporation, 2009
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>
28 #include "trace_output.h"
29 #include "trace_stat.h"
32 /* For now, let us restrict the no. of symbols traced simultaneously to number
33 * of available hardware breakpoint registers.
35 #define KSYM_TRACER_MAX HBP_NUM
37 #define KSYM_TRACER_OP_LEN 3 /* rw- */
40 struct hw_breakpoint *ksym_hbp;
41 unsigned long ksym_addr;
42 #ifdef CONFIG_PROFILE_KSYM_TRACER
43 unsigned long counter;
45 struct hlist_node ksym_hlist;
48 static struct trace_array *ksym_trace_array;
50 static unsigned int ksym_filter_entry_count;
51 static unsigned int ksym_tracing_enabled;
53 static HLIST_HEAD(ksym_filter_head);
55 static DEFINE_MUTEX(ksym_tracer_mutex);
57 #ifdef CONFIG_PROFILE_KSYM_TRACER
59 #define MAX_UL_INT 0xffffffff
61 void ksym_collect_stats(unsigned long hbp_hit_addr)
63 struct hlist_node *node;
64 struct trace_ksym *entry;
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)) {
76 #endif /* CONFIG_PROFILE_KSYM_TRACER */
78 void ksym_hbp_handler(struct hw_breakpoint *hbp, struct pt_regs *regs)
80 struct ring_buffer_event *event;
81 struct trace_array *tr;
82 struct ksym_trace_entry *entry;
85 if (!ksym_tracing_enabled)
88 tr = ksym_trace_array;
91 event = trace_buffer_lock_reserve(tr, TRACE_KSYM,
92 sizeof(*entry), 0, pc);
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);
102 #ifdef CONFIG_PROFILE_KSYM_TRACER
103 ksym_collect_stats(hbp->info.address);
104 #endif /* CONFIG_PROFILE_KSYM_TRACER */
106 trace_buffer_unlock_commit(tr, event, 0, pc);
109 /* Valid access types are represented as
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)
117 static int ksym_trace_get_access_type(char *str)
123 else if (str[0] != '-')
128 else if (str[1] != '-')
136 access = HW_BREAKPOINT_RW;
139 access = HW_BREAKPOINT_WRITE;
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
158 static int parse_ksym_trace_str(char *input_string, char **ksymname,
161 char *delimiter = ":";
165 *ksymname = strsep(&input_string, delimiter);
166 *addr = kallsyms_lookup_name(*ksymname);
168 /* Check for malformed request: (2), (1) and (5) */
169 if ((!input_string) ||
170 (strlen(input_string) != (KSYM_TRACER_OP_LEN + 1)) ||
173 ret = ksym_trace_get_access_type(input_string);
179 int process_new_ksym_entry(char *ksymname, int op, unsigned long addr)
181 struct trace_ksym *entry;
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",
191 entry = kzalloc(sizeof(struct trace_ksym), GFP_KERNEL);
195 entry->ksym_hbp = kzalloc(sizeof(struct hw_breakpoint), GFP_KERNEL);
196 if (!entry->ksym_hbp) {
201 entry->ksym_hbp->info.name = ksymname;
202 entry->ksym_hbp->info.type = op;
203 entry->ksym_addr = entry->ksym_hbp->info.address = addr;
205 entry->ksym_hbp->info.len = HW_BREAKPOINT_LEN_4;
207 entry->ksym_hbp->triggered = (void *)ksym_hbp_handler;
209 ret = register_kernel_hw_breakpoint(entry->ksym_hbp);
211 printk(KERN_INFO "ksym_tracer request failed. Try again"
213 kfree(entry->ksym_hbp);
217 hlist_add_head_rcu(&(entry->ksym_hlist), &ksym_filter_head);
218 ksym_filter_entry_count++;
223 static ssize_t ksym_trace_filter_read(struct file *filp, char __user *ubuf,
224 size_t count, loff_t *ppos)
226 struct trace_ksym *entry;
227 struct hlist_node *node;
232 s = kmalloc(sizeof(*s), GFP_KERNEL);
237 mutex_lock(&ksym_tracer_mutex);
239 hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) {
240 ret = trace_seq_printf(s, "%s:", entry->ksym_hbp->info.name);
241 if (entry->ksym_hbp->info.type == HW_BREAKPOINT_WRITE)
242 ret = trace_seq_puts(s, "-w-\n");
243 else if (entry->ksym_hbp->info.type == HW_BREAKPOINT_RW)
244 ret = trace_seq_puts(s, "rw-\n");
248 cnt = simple_read_from_buffer(ubuf, count, ppos, s->buffer, s->len);
250 mutex_unlock(&ksym_tracer_mutex);
257 static ssize_t ksym_trace_filter_write(struct file *file,
258 const char __user *buffer,
259 size_t count, loff_t *ppos)
261 struct trace_ksym *entry;
262 struct hlist_node *node;
263 char *input_string, *ksymname = NULL;
264 unsigned long ksym_addr = 0;
265 int ret, op, changed = 0;
267 /* Ignore echo "" > ksym_trace_filter */
271 input_string = kzalloc(count, GFP_KERNEL);
275 if (copy_from_user(input_string, buffer, count)) {
280 ret = op = parse_ksym_trace_str(input_string, &ksymname, &ksym_addr);
286 mutex_lock(&ksym_tracer_mutex);
289 hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) {
290 if (entry->ksym_addr == ksym_addr) {
291 /* Check for malformed request: (6) */
292 if (entry->ksym_hbp->info.type != op)
300 unregister_kernel_hw_breakpoint(entry->ksym_hbp);
301 entry->ksym_hbp->info.type = op;
303 ret = register_kernel_hw_breakpoint(entry->ksym_hbp);
306 goto unlock_ret_path;
309 ksym_filter_entry_count--;
310 hlist_del_rcu(&(entry->ksym_hlist));
312 kfree(entry->ksym_hbp);
317 /* Check for malformed request: (4) */
320 ret = process_new_ksym_entry(ksymname, op, ksym_addr);
325 goto unlock_ret_path;
331 mutex_unlock(&ksym_tracer_mutex);
335 static const struct file_operations ksym_tracing_fops = {
336 .open = tracing_open_generic,
337 .read = ksym_trace_filter_read,
338 .write = ksym_trace_filter_write,
341 static void ksym_trace_reset(struct trace_array *tr)
343 struct trace_ksym *entry;
344 struct hlist_node *node, *node1;
346 ksym_tracing_enabled = 0;
348 mutex_lock(&ksym_tracer_mutex);
349 hlist_for_each_entry_safe(entry, node, node1, &ksym_filter_head,
351 unregister_kernel_hw_breakpoint(entry->ksym_hbp);
352 ksym_filter_entry_count--;
353 hlist_del_rcu(&(entry->ksym_hlist));
355 /* Free the 'input_string' only if reset
356 * after startup self-test
358 #ifdef CONFIG_FTRACE_SELFTEST
359 if (strncmp(entry->ksym_hbp->info.name, KSYM_SELFTEST_ENTRY,
360 strlen(KSYM_SELFTEST_ENTRY)) != 0)
361 #endif /* CONFIG_FTRACE_SELFTEST*/
362 kfree(entry->ksym_hbp->info.name);
363 kfree(entry->ksym_hbp);
366 mutex_unlock(&ksym_tracer_mutex);
369 static int ksym_trace_init(struct trace_array *tr)
373 for_each_online_cpu(cpu)
374 tracing_reset(tr, cpu);
375 ksym_tracing_enabled = 1;
376 ksym_trace_array = tr;
381 static void ksym_trace_print_header(struct seq_file *m)
385 "# TASK-PID CPU# Symbol Type "
392 static enum print_line_t ksym_trace_output(struct trace_iterator *iter)
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];
400 if (entry->type != TRACE_KSYM)
401 return TRACE_TYPE_UNHANDLED;
403 trace_assign_type(field, entry);
405 ret = trace_seq_printf(s, "%-15s %-5d %-3d %-20s ", field->cmd,
406 entry->pid, iter->cpu, field->ksym_name);
408 return TRACE_TYPE_PARTIAL_LINE;
410 switch (field->type) {
411 case HW_BREAKPOINT_WRITE:
412 ret = trace_seq_printf(s, " W ");
414 case HW_BREAKPOINT_RW:
415 ret = trace_seq_printf(s, " RW ");
418 return TRACE_TYPE_PARTIAL_LINE;
422 return TRACE_TYPE_PARTIAL_LINE;
424 sprint_symbol(str, field->ip);
425 ret = trace_seq_printf(s, "%-20s\n", str);
427 return TRACE_TYPE_PARTIAL_LINE;
429 return TRACE_TYPE_HANDLED;
432 struct tracer ksym_tracer __read_mostly =
434 .name = "ksym_tracer",
435 .init = ksym_trace_init,
436 .reset = ksym_trace_reset,
437 #ifdef CONFIG_FTRACE_SELFTEST
438 .selftest = trace_selftest_startup_ksym,
440 .print_header = ksym_trace_print_header,
441 .print_line = ksym_trace_output
444 __init static int init_ksym_trace(void)
446 struct dentry *d_tracer;
447 struct dentry *entry;
449 d_tracer = tracing_init_dentry();
450 ksym_filter_entry_count = 0;
452 entry = debugfs_create_file("ksym_trace_filter", 0644, d_tracer,
453 NULL, &ksym_tracing_fops);
455 pr_warning("Could not create debugfs "
456 "'ksym_trace_filter' file\n");
458 return register_tracer(&ksym_tracer);
460 device_initcall(init_ksym_trace);
463 #ifdef CONFIG_PROFILE_KSYM_TRACER
464 static int ksym_tracer_stat_headers(struct seq_file *m)
466 seq_printf(m, " Access type ");
467 seq_printf(m, " Symbol Counter \n");
471 static int ksym_tracer_stat_show(struct seq_file *m, void *v)
473 struct hlist_node *stat = v;
474 struct trace_ksym *entry;
476 char fn_name[KSYM_NAME_LEN];
478 entry = hlist_entry(stat, struct trace_ksym, ksym_hlist);
481 access_type = entry->ksym_hbp->info.type;
483 switch (access_type) {
484 case HW_BREAKPOINT_WRITE:
485 seq_printf(m, " W ");
487 case HW_BREAKPOINT_RW:
488 seq_printf(m, " RW ");
491 seq_printf(m, " NA ");
494 if (lookup_symbol_name(entry->ksym_addr, fn_name) >= 0)
495 seq_printf(m, " %s ", fn_name);
497 seq_printf(m, " <NA> ");
499 seq_printf(m, "%15lu\n", entry->counter);
503 static void *ksym_tracer_stat_start(struct tracer_stat *trace)
505 return &(ksym_filter_head.first);
509 ksym_tracer_stat_next(void *v, int idx)
511 struct hlist_node *stat = v;
516 static struct tracer_stat ksym_tracer_stats = {
517 .name = "ksym_tracer",
518 .stat_start = ksym_tracer_stat_start,
519 .stat_next = ksym_tracer_stat_next,
520 .stat_headers = ksym_tracer_stat_headers,
521 .stat_show = ksym_tracer_stat_show
524 __init static int ksym_tracer_stat_init(void)
528 ret = register_stat_tracer(&ksym_tracer_stats);
530 printk(KERN_WARNING "Warning: could not register "
531 "ksym tracer stats\n");
537 fs_initcall(ksym_tracer_stat_init);
538 #endif /* CONFIG_PROFILE_KSYM_TRACER */