tracing: export trace formats to user space

The binary printk saves a pointer to the format string in the ring buffer.
On output, the format is processed. But if the user is reading the
ring buffer through a binary interface, the pointer is meaningless.

This patch creates a file called printk_formats that maps the pointers
to the formats.

 # cat /debug/tracing/printk_formats
0xffffffff80713d40 : "irq_handler_entry: irq=%d handler=%s\n"
0xffffffff80713d48 : "lock_acquire: %s%s%s\n"
0xffffffff80713d50 : "lock_release: %s\n"

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
This commit is contained in:
Steven Rostedt 2009-03-12 14:23:17 -04:00
parent e9fb2b6d58
commit 7975a2be16
1 changed files with 114 additions and 5 deletions

View File

@ -4,18 +4,19 @@
* 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/mutex.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/fs.h>
#include <linux/marker.h>
#include <linux/uaccess.h>
#include "trace.h"
@ -153,6 +154,114 @@ int __ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap)
}
EXPORT_SYMBOL_GPL(__ftrace_vprintk);
static void *
t_next(struct seq_file *m, void *v, loff_t *pos)
{
const char **fmt = m->private;
const char **next = fmt;
(*pos)++;
if ((unsigned long)fmt >= (unsigned long)__stop___trace_bprintk_fmt)
return NULL;
next = fmt;
m->private = ++next;
return fmt;
}
static void *t_start(struct seq_file *m, loff_t *pos)
{
return t_next(m, NULL, 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)
{
int ret;
ret = seq_open(file, &show_format_seq_ops);
if (!ret) {
struct seq_file *m = file->private_data;
m->private = __start___trace_bprintk_fmt;
}
return ret;
}
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;
struct dentry *entry;
d_tracer = tracing_init_dentry();
if (!d_tracer)
return 0;
entry = debugfs_create_file("printk_formats", 0444, d_tracer,
NULL, &ftrace_formats_fops);
if (!entry)
pr_warning("Could not create debugfs "
"'printk_formats' entry\n");
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);