linux/kernel/trace/trace_ksym.c
Frederic Weisbecker b326e9560a hw-breakpoints: Use overflow handler instead of the event callback
struct perf_event::event callback was called when a breakpoint
triggers. But this is a rather opaque callback, pretty
tied-only to the breakpoint API and not really integrated into perf
as it triggers even when we don't overflow.

We prefer to use overflow_handler() as it fits into the perf events
rules, being called only when we overflow.

Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: "K. Prasad" <prasad@linux.vnet.ibm.com>
2009-12-06 08:27:18 +01:00

552 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, int nmi,
struct perf_sample_data *data,
struct pt_regs *regs)
{
struct ring_buffer_event *event;
struct ksym_trace_entry *entry;
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 */