[PATCH 09/16] tracing: export trace formats to user space

Steven Rostedt
2009-03-13T02:45:24Z

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From: Steven Rostedt <srostedt@redhat.com>

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>
---
kernel/trace/trace_printk.c | 119 +++++++++++++++++++++++++++++++++++++++++--
1 files changed, 114 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/trace_printk.c b/kernel/trace/trace_printk.c
index f307a11..4867852 100644
--- a/kernel/trace/trace_printk.c
+++ b/kernel/trace/trace_printk.c
@@ -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);
--
1.6.1.3

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