linux/kernel/trace/trace_ksym.c
Frederic Weisbecker dd1853c3f4 hw-breakpoints: Use struct perf_event_attr to define kernel breakpoints
Kernel breakpoints are created using functions in which we pass
breakpoint parameters as individual variables: address, length
and type.

Although it fits well for x86, this just does not scale across
architectures that may support this api later as these may have
more or different needs. Pass in a perf_event_attr structure
instead because it is meant to evolve as much as possible into
a generic hardware breakpoint parameter structure.

Reported-by: K.Prasad <prasad@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1259294154-5197-2-git-send-regression-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-11-27 06:22:59 +01:00

551 lines
13 KiB
C

/*
* trace_ksym.c - Kernel Symbol Tracer
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Copyright (C) IBM Corporation, 2009
*/
#include <linux/kallsyms.h>
#include <linux/uaccess.h>
#include <linux/debugfs.h>
#include <linux/ftrace.h>
#include <linux/module.h>
#include <linux/fs.h>
#include "trace_output.h"
#include "trace_stat.h"
#include "trace.h"
#include <linux/hw_breakpoint.h>
#include <asm/hw_breakpoint.h>
/*
* For now, let us restrict the no. of symbols traced simultaneously to number
* of available hardware breakpoint registers.
*/
#define KSYM_TRACER_MAX HBP_NUM
#define KSYM_TRACER_OP_LEN 3 /* rw- */
struct trace_ksym {
struct perf_event **ksym_hbp;
struct perf_event_attr attr;
#ifdef CONFIG_PROFILE_KSYM_TRACER
unsigned long counter;
#endif
struct hlist_node ksym_hlist;
};
static struct trace_array *ksym_trace_array;
static unsigned int ksym_filter_entry_count;
static unsigned int ksym_tracing_enabled;
static HLIST_HEAD(ksym_filter_head);
static DEFINE_MUTEX(ksym_tracer_mutex);
#ifdef CONFIG_PROFILE_KSYM_TRACER
#define MAX_UL_INT 0xffffffff
void ksym_collect_stats(unsigned long hbp_hit_addr)
{
struct hlist_node *node;
struct trace_ksym *entry;
rcu_read_lock();
hlist_for_each_entry_rcu(entry, node, &ksym_filter_head, ksym_hlist) {
if ((entry->attr.bp_addr == hbp_hit_addr) &&
(entry->counter <= MAX_UL_INT)) {
entry->counter++;
break;
}
}
rcu_read_unlock();
}
#endif /* CONFIG_PROFILE_KSYM_TRACER */
void ksym_hbp_handler(struct perf_event *hbp, void *data)
{
struct ring_buffer_event *event;
struct ksym_trace_entry *entry;
struct pt_regs *regs = data;
struct ring_buffer *buffer;
int pc;
if (!ksym_tracing_enabled)
return;
buffer = ksym_trace_array->buffer;
pc = preempt_count();
event = trace_buffer_lock_reserve(buffer, TRACE_KSYM,
sizeof(*entry), 0, pc);
if (!event)
return;
entry = ring_buffer_event_data(event);
entry->ip = instruction_pointer(regs);
entry->type = hw_breakpoint_type(hbp);
entry->addr = hw_breakpoint_addr(hbp);
strlcpy(entry->cmd, current->comm, TASK_COMM_LEN);
#ifdef CONFIG_PROFILE_KSYM_TRACER
ksym_collect_stats(hw_breakpoint_addr(hbp));
#endif /* CONFIG_PROFILE_KSYM_TRACER */
trace_buffer_unlock_commit(buffer, event, 0, pc);
}
/* Valid access types are represented as
*
* rw- : Set Read/Write Access Breakpoint
* -w- : Set Write Access Breakpoint
* --- : Clear Breakpoints
* --x : Set Execution Break points (Not available yet)
*
*/
static int ksym_trace_get_access_type(char *str)
{
int access = 0;
if (str[0] == 'r')
access |= HW_BREAKPOINT_R;
if (str[1] == 'w')
access |= HW_BREAKPOINT_W;
if (str[2] == 'x')
access |= HW_BREAKPOINT_X;
switch (access) {
case HW_BREAKPOINT_R:
case HW_BREAKPOINT_W:
case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
return access;
default:
return -EINVAL;
}
}
/*
* There can be several possible malformed requests and we attempt to capture
* all of them. We enumerate some of the rules
* 1. We will not allow kernel symbols with ':' since it is used as a delimiter.
* i.e. multiple ':' symbols disallowed. Possible uses are of the form
* <module>:<ksym_name>:<op>.
* 2. No delimiter symbol ':' in the input string
* 3. Spurious operator symbols or symbols not in their respective positions
* 4. <ksym_name>:--- i.e. clear breakpoint request when ksym_name not in file
* 5. Kernel symbol not a part of /proc/kallsyms
* 6. Duplicate requests
*/
static int parse_ksym_trace_str(char *input_string, char **ksymname,
unsigned long *addr)
{
int ret;
*ksymname = strsep(&input_string, ":");
*addr = kallsyms_lookup_name(*ksymname);
/* Check for malformed request: (2), (1) and (5) */
if ((!input_string) ||
(strlen(input_string) != KSYM_TRACER_OP_LEN) ||
(*addr == 0))
return -EINVAL;;
ret = ksym_trace_get_access_type(input_string);
return ret;
}
int process_new_ksym_entry(char *ksymname, int op, unsigned long addr)
{
struct trace_ksym *entry;
int ret = -ENOMEM;
if (ksym_filter_entry_count >= KSYM_TRACER_MAX) {
printk(KERN_ERR "ksym_tracer: Maximum limit:(%d) reached. No"
" new requests for tracing can be accepted now.\n",
KSYM_TRACER_MAX);
return -ENOSPC;
}
entry = kzalloc(sizeof(struct trace_ksym), GFP_KERNEL);
if (!entry)
return -ENOMEM;
hw_breakpoint_init(&entry->attr);
entry->attr.bp_type = op;
entry->attr.bp_addr = addr;
entry->attr.bp_len = HW_BREAKPOINT_LEN_4;
ret = -EAGAIN;
entry->ksym_hbp = register_wide_hw_breakpoint(&entry->attr,
ksym_hbp_handler);
if (IS_ERR(entry->ksym_hbp)) {
ret = PTR_ERR(entry->ksym_hbp);
printk(KERN_INFO "ksym_tracer request failed. Try again"
" later!!\n");
goto err;
}
hlist_add_head_rcu(&(entry->ksym_hlist), &ksym_filter_head);
ksym_filter_entry_count++;
return 0;
err:
kfree(entry);
return ret;
}
static ssize_t ksym_trace_filter_read(struct file *filp, char __user *ubuf,
size_t count, loff_t *ppos)
{
struct trace_ksym *entry;
struct hlist_node *node;
struct trace_seq *s;
ssize_t cnt = 0;
int ret;
s = kmalloc(sizeof(*s), GFP_KERNEL);
if (!s)
return -ENOMEM;
trace_seq_init(s);
mutex_lock(&ksym_tracer_mutex);
hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) {
ret = trace_seq_printf(s, "%pS:", (void *)entry->attr.bp_addr);
if (entry->attr.bp_type == HW_BREAKPOINT_R)
ret = trace_seq_puts(s, "r--\n");
else if (entry->attr.bp_type == HW_BREAKPOINT_W)
ret = trace_seq_puts(s, "-w-\n");
else if (entry->attr.bp_type == (HW_BREAKPOINT_W | HW_BREAKPOINT_R))
ret = trace_seq_puts(s, "rw-\n");
WARN_ON_ONCE(!ret);
}
cnt = simple_read_from_buffer(ubuf, count, ppos, s->buffer, s->len);
mutex_unlock(&ksym_tracer_mutex);
kfree(s);
return cnt;
}
static void __ksym_trace_reset(void)
{
struct trace_ksym *entry;
struct hlist_node *node, *node1;
mutex_lock(&ksym_tracer_mutex);
hlist_for_each_entry_safe(entry, node, node1, &ksym_filter_head,
ksym_hlist) {
unregister_wide_hw_breakpoint(entry->ksym_hbp);
ksym_filter_entry_count--;
hlist_del_rcu(&(entry->ksym_hlist));
synchronize_rcu();
kfree(entry);
}
mutex_unlock(&ksym_tracer_mutex);
}
static ssize_t ksym_trace_filter_write(struct file *file,
const char __user *buffer,
size_t count, loff_t *ppos)
{
struct trace_ksym *entry;
struct hlist_node *node;
char *input_string, *ksymname = NULL;
unsigned long ksym_addr = 0;
int ret, op, changed = 0;
input_string = kzalloc(count + 1, GFP_KERNEL);
if (!input_string)
return -ENOMEM;
if (copy_from_user(input_string, buffer, count)) {
kfree(input_string);
return -EFAULT;
}
input_string[count] = '\0';
strstrip(input_string);
/*
* Clear all breakpoints if:
* 1: echo > ksym_trace_filter
* 2: echo 0 > ksym_trace_filter
* 3: echo "*:---" > ksym_trace_filter
*/
if (!input_string[0] || !strcmp(input_string, "0") ||
!strcmp(input_string, "*:---")) {
__ksym_trace_reset();
kfree(input_string);
return count;
}
ret = op = parse_ksym_trace_str(input_string, &ksymname, &ksym_addr);
if (ret < 0) {
kfree(input_string);
return ret;
}
mutex_lock(&ksym_tracer_mutex);
ret = -EINVAL;
hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) {
if (entry->attr.bp_addr == ksym_addr) {
/* Check for malformed request: (6) */
if (entry->attr.bp_type != op)
changed = 1;
else
goto out;
break;
}
}
if (changed) {
unregister_wide_hw_breakpoint(entry->ksym_hbp);
entry->attr.bp_type = op;
ret = 0;
if (op > 0) {
entry->ksym_hbp =
register_wide_hw_breakpoint(&entry->attr,
ksym_hbp_handler);
if (IS_ERR(entry->ksym_hbp))
ret = PTR_ERR(entry->ksym_hbp);
else
goto out;
}
/* Error or "symbol:---" case: drop it */
ksym_filter_entry_count--;
hlist_del_rcu(&(entry->ksym_hlist));
synchronize_rcu();
kfree(entry);
goto out;
} else {
/* Check for malformed request: (4) */
if (op == 0)
goto out;
ret = process_new_ksym_entry(ksymname, op, ksym_addr);
}
out:
mutex_unlock(&ksym_tracer_mutex);
kfree(input_string);
if (!ret)
ret = count;
return ret;
}
static const struct file_operations ksym_tracing_fops = {
.open = tracing_open_generic,
.read = ksym_trace_filter_read,
.write = ksym_trace_filter_write,
};
static void ksym_trace_reset(struct trace_array *tr)
{
ksym_tracing_enabled = 0;
__ksym_trace_reset();
}
static int ksym_trace_init(struct trace_array *tr)
{
int cpu, ret = 0;
for_each_online_cpu(cpu)
tracing_reset(tr, cpu);
ksym_tracing_enabled = 1;
ksym_trace_array = tr;
return ret;
}
static void ksym_trace_print_header(struct seq_file *m)
{
seq_puts(m,
"# TASK-PID CPU# Symbol "
"Type Function\n");
seq_puts(m,
"# | | | "
" | |\n");
}
static enum print_line_t ksym_trace_output(struct trace_iterator *iter)
{
struct trace_entry *entry = iter->ent;
struct trace_seq *s = &iter->seq;
struct ksym_trace_entry *field;
char str[KSYM_SYMBOL_LEN];
int ret;
if (entry->type != TRACE_KSYM)
return TRACE_TYPE_UNHANDLED;
trace_assign_type(field, entry);
ret = trace_seq_printf(s, "%11s-%-5d [%03d] %pS", field->cmd,
entry->pid, iter->cpu, (char *)field->addr);
if (!ret)
return TRACE_TYPE_PARTIAL_LINE;
switch (field->type) {
case HW_BREAKPOINT_R:
ret = trace_seq_printf(s, " R ");
break;
case HW_BREAKPOINT_W:
ret = trace_seq_printf(s, " W ");
break;
case HW_BREAKPOINT_R | HW_BREAKPOINT_W:
ret = trace_seq_printf(s, " RW ");
break;
default:
return TRACE_TYPE_PARTIAL_LINE;
}
if (!ret)
return TRACE_TYPE_PARTIAL_LINE;
sprint_symbol(str, field->ip);
ret = trace_seq_printf(s, "%s\n", str);
if (!ret)
return TRACE_TYPE_PARTIAL_LINE;
return TRACE_TYPE_HANDLED;
}
struct tracer ksym_tracer __read_mostly =
{
.name = "ksym_tracer",
.init = ksym_trace_init,
.reset = ksym_trace_reset,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_ksym,
#endif
.print_header = ksym_trace_print_header,
.print_line = ksym_trace_output
};
__init static int init_ksym_trace(void)
{
struct dentry *d_tracer;
struct dentry *entry;
d_tracer = tracing_init_dentry();
ksym_filter_entry_count = 0;
entry = debugfs_create_file("ksym_trace_filter", 0644, d_tracer,
NULL, &ksym_tracing_fops);
if (!entry)
pr_warning("Could not create debugfs "
"'ksym_trace_filter' file\n");
return register_tracer(&ksym_tracer);
}
device_initcall(init_ksym_trace);
#ifdef CONFIG_PROFILE_KSYM_TRACER
static int ksym_tracer_stat_headers(struct seq_file *m)
{
seq_puts(m, " Access Type ");
seq_puts(m, " Symbol Counter\n");
seq_puts(m, " ----------- ");
seq_puts(m, " ------ -------\n");
return 0;
}
static int ksym_tracer_stat_show(struct seq_file *m, void *v)
{
struct hlist_node *stat = v;
struct trace_ksym *entry;
int access_type = 0;
char fn_name[KSYM_NAME_LEN];
entry = hlist_entry(stat, struct trace_ksym, ksym_hlist);
access_type = entry->attr.bp_type;
switch (access_type) {
case HW_BREAKPOINT_R:
seq_puts(m, " R ");
break;
case HW_BREAKPOINT_W:
seq_puts(m, " W ");
break;
case HW_BREAKPOINT_R | HW_BREAKPOINT_W:
seq_puts(m, " RW ");
break;
default:
seq_puts(m, " NA ");
}
if (lookup_symbol_name(entry->attr.bp_addr, fn_name) >= 0)
seq_printf(m, " %-36s", fn_name);
else
seq_printf(m, " %-36s", "<NA>");
seq_printf(m, " %15lu\n", entry->counter);
return 0;
}
static void *ksym_tracer_stat_start(struct tracer_stat *trace)
{
return ksym_filter_head.first;
}
static void *
ksym_tracer_stat_next(void *v, int idx)
{
struct hlist_node *stat = v;
return stat->next;
}
static struct tracer_stat ksym_tracer_stats = {
.name = "ksym_tracer",
.stat_start = ksym_tracer_stat_start,
.stat_next = ksym_tracer_stat_next,
.stat_headers = ksym_tracer_stat_headers,
.stat_show = ksym_tracer_stat_show
};
__init static int ksym_tracer_stat_init(void)
{
int ret;
ret = register_stat_tracer(&ksym_tracer_stats);
if (ret) {
printk(KERN_WARNING "Warning: could not register "
"ksym tracer stats\n");
return 1;
}
return 0;
}
fs_initcall(ksym_tracer_stat_init);
#endif /* CONFIG_PROFILE_KSYM_TRACER */