Commit 7975a2be authored by Steven Rostedt's avatar Steven Rostedt
Browse files

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: default avatarSteven Rostedt <srostedt@redhat.com>
parent e9fb2b6d

kernel/trace/trace_printk.c

+114 −5
Original line number Diff line number Diff line
@@ -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);

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