linux/kernel/trace/trace_printk.c
Steven Rostedt 4c739ff043 tracing: show proper address for trace-printk format
Since the trace_printk may use pointers to the format fields
in the buffer, they are exported via debugfs/tracing/printk_formats.
This is used by utilities that read the ring buffer in binary format.
It helps the utilities map the address of the format in the binary
buffer to what the printf format looks like.

Unfortunately, the way the output code works, it exports the address
of the pointer to the format address, and not the format address
itself. This makes the file totally useless in trying to figure
out what format string a binary address belongs to.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-07-23 10:07:17 -04:00

253 lines
5.0 KiB
C

/*
* trace binary printk
*
* Copyright (C) 2008 Lai Jiangshan <laijs@cn.fujitsu.com>
*
*/
#include <linux/seq_file.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/kernel.h>
#include <linux/ftrace.h>
#include <linux/string.h>
#include <linux/module.h>
#include <linux/marker.h>
#include <linux/mutex.h>
#include <linux/ctype.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include "trace.h"
#ifdef CONFIG_MODULES
/*
* modules trace_printk()'s formats are autosaved in struct trace_bprintk_fmt
* which are queued on trace_bprintk_fmt_list.
*/
static LIST_HEAD(trace_bprintk_fmt_list);
/* serialize accesses to trace_bprintk_fmt_list */
static DEFINE_MUTEX(btrace_mutex);
struct trace_bprintk_fmt {
struct list_head list;
char fmt[0];
};
static inline struct trace_bprintk_fmt *lookup_format(const char *fmt)
{
struct trace_bprintk_fmt *pos;
list_for_each_entry(pos, &trace_bprintk_fmt_list, list) {
if (!strcmp(pos->fmt, fmt))
return pos;
}
return NULL;
}
static
void hold_module_trace_bprintk_format(const char **start, const char **end)
{
const char **iter;
mutex_lock(&btrace_mutex);
for (iter = start; iter < end; iter++) {
struct trace_bprintk_fmt *tb_fmt = lookup_format(*iter);
if (tb_fmt) {
*iter = tb_fmt->fmt;
continue;
}
tb_fmt = kmalloc(offsetof(struct trace_bprintk_fmt, fmt)
+ strlen(*iter) + 1, GFP_KERNEL);
if (tb_fmt) {
list_add_tail(&tb_fmt->list, &trace_bprintk_fmt_list);
strcpy(tb_fmt->fmt, *iter);
*iter = tb_fmt->fmt;
} else
*iter = NULL;
}
mutex_unlock(&btrace_mutex);
}
static int module_trace_bprintk_format_notify(struct notifier_block *self,
unsigned long val, void *data)
{
struct module *mod = data;
if (mod->num_trace_bprintk_fmt) {
const char **start = mod->trace_bprintk_fmt_start;
const char **end = start + mod->num_trace_bprintk_fmt;
if (val == MODULE_STATE_COMING)
hold_module_trace_bprintk_format(start, end);
}
return 0;
}
#else /* !CONFIG_MODULES */
__init static int
module_trace_bprintk_format_notify(struct notifier_block *self,
unsigned long val, void *data)
{
return 0;
}
#endif /* CONFIG_MODULES */
__initdata_or_module static
struct notifier_block module_trace_bprintk_format_nb = {
.notifier_call = module_trace_bprintk_format_notify,
};
int __trace_bprintk(unsigned long ip, const char *fmt, ...)
{
int ret;
va_list ap;
if (unlikely(!fmt))
return 0;
if (!(trace_flags & TRACE_ITER_PRINTK))
return 0;
va_start(ap, fmt);
ret = trace_vbprintk(ip, fmt, ap);
va_end(ap);
return ret;
}
EXPORT_SYMBOL_GPL(__trace_bprintk);
int __ftrace_vbprintk(unsigned long ip, const char *fmt, va_list ap)
{
if (unlikely(!fmt))
return 0;
if (!(trace_flags & TRACE_ITER_PRINTK))
return 0;
return trace_vbprintk(ip, fmt, ap);
}
EXPORT_SYMBOL_GPL(__ftrace_vbprintk);
int __trace_printk(unsigned long ip, const char *fmt, ...)
{
int ret;
va_list ap;
if (!(trace_flags & TRACE_ITER_PRINTK))
return 0;
va_start(ap, fmt);
ret = trace_vprintk(ip, fmt, ap);
va_end(ap);
return ret;
}
EXPORT_SYMBOL_GPL(__trace_printk);
int __ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap)
{
if (!(trace_flags & TRACE_ITER_PRINTK))
return 0;
return trace_vprintk(ip, fmt, ap);
}
EXPORT_SYMBOL_GPL(__ftrace_vprintk);
static void *
t_start(struct seq_file *m, loff_t *pos)
{
const char **fmt = __start___trace_bprintk_fmt + *pos;
if ((unsigned long)fmt >= (unsigned long)__stop___trace_bprintk_fmt)
return NULL;
return fmt;
}
static void *t_next(struct seq_file *m, void * v, loff_t *pos)
{
(*pos)++;
return t_start(m, pos);
}
static int t_show(struct seq_file *m, void *v)
{
const char **fmt = v;
const char *str = *fmt;
int i;
seq_printf(m, "0x%lx : \"", *(unsigned long *)fmt);
/*
* Tabs and new lines need to be converted.
*/
for (i = 0; str[i]; i++) {
switch (str[i]) {
case '\n':
seq_puts(m, "\\n");
break;
case '\t':
seq_puts(m, "\\t");
break;
case '\\':
seq_puts(m, "\\");
break;
case '"':
seq_puts(m, "\\\"");
break;
default:
seq_putc(m, str[i]);
}
}
seq_puts(m, "\"\n");
return 0;
}
static void t_stop(struct seq_file *m, void *p)
{
}
static const struct seq_operations show_format_seq_ops = {
.start = t_start,
.next = t_next,
.show = t_show,
.stop = t_stop,
};
static int
ftrace_formats_open(struct inode *inode, struct file *file)
{
return seq_open(file, &show_format_seq_ops);
}
static const struct file_operations ftrace_formats_fops = {
.open = ftrace_formats_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release,
};
static __init int init_trace_printk_function_export(void)
{
struct dentry *d_tracer;
d_tracer = tracing_init_dentry();
if (!d_tracer)
return 0;
trace_create_file("printk_formats", 0444, d_tracer,
NULL, &ftrace_formats_fops);
return 0;
}
fs_initcall(init_trace_printk_function_export);
static __init int init_trace_printk(void)
{
return register_module_notifier(&module_trace_bprintk_format_nb);
}
early_initcall(init_trace_printk);