[PATCH 4/5] ftrace: show ftrace_bprintk()'s formats

From: Lai Jiangshan
Date: Tue Dec 30 2008 - 22:01:33 EST



Impact: let user knows the format

Create a file on <debugfs-dir>/tracing/ to show ftrace_bprintk()'s formats.

This formats will help for these condition:
1) User get binary data from core file.(formats are backup before coredump)
2) User splice ring_buffer to a file.
User can use formats for parsing the binary data in userspace.

Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
---
trace.c | 8 +++++
trace.h | 1
trace_bprintk.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 88 insertions(+)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 61c9108..085cc8a 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2944,6 +2944,14 @@ static __init int tracer_init_debugfs(void)
pr_warning("Could not create debugfs "
"'trace_marker' entry\n");

+#ifdef CONFIG_TRACE_BPRINTK
+ entry = debugfs_create_file("trace_bprintk_formats", 0444, d_tracer,
+ NULL, &trace_bprintk_fmt_fops);
+ if (!entry)
+ pr_warning("Could not create debugfs "
+ "'trace_bprintk_formats' entry\n");
+#endif
+
#ifdef CONFIG_DYNAMIC_FTRACE
entry = debugfs_create_file("dyn_ftrace_total_info", 0444, d_tracer,
&ftrace_update_tot_cnt,
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 6885d13..c50826d 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -128,6 +128,7 @@ struct bprintk_entry {
u32 buf[];
};
#ifdef CONFIG_TRACE_BPRINTK
+extern struct file_operations trace_bprintk_fmt_fops;
extern int trace_bprintk_enable;
#endif

diff --git a/kernel/trace/trace_bprintk.c b/kernel/trace/trace_bprintk.c
index 84c7a9c..cbe89dd 100644
--- a/kernel/trace/trace_bprintk.c
+++ b/kernel/trace/trace_bprintk.c
@@ -156,6 +156,85 @@ static struct notifier_block module_trace_bprintk_format_nb = {
.notifier_call = module_trace_bprintk_format_notify,
};

+/* shows ftrace_bprintk()'s format */
+extern char *__start___trace_bprintk_fmt[], *__stop___trace_bprintk_fmt[];
+
+static void *fmt_start(struct seq_file *m, loff_t *pos)
+{
+ loff_t tmp;
+ struct trace_bprintk_fmt *tb_fmt;
+
+ lock_btrace();
+ if (*pos < __stop___trace_bprintk_fmt - __start___trace_bprintk_fmt)
+ return __stop___trace_bprintk_fmt[*pos - 1];
+
+ tmp = __start___trace_bprintk_fmt + *pos - __stop___trace_bprintk_fmt;
+ list_for_each_entry(tb_fmt, &trace_bprintk_fmt_list, list) {
+ if (tmp-- == 0)
+ return tb_fmt->fmt;
+ }
+ return NULL;
+}
+
+static void *fmt_next(struct seq_file *m, void *p, loff_t *pos)
+{
+ char *fmt = p;
+ struct list_head *list;
+
+ ++*pos;
+ if (*pos < __stop___trace_bprintk_fmt - __start___trace_bprintk_fmt)
+ return __stop___trace_bprintk_fmt[*pos - 1];
+
+ if (__start___trace_bprintk_fmt + *pos - __stop___trace_bprintk_fmt)
+ list = &container_of(fmt, struct trace_bprintk_fmt, fmt[0])
+ ->list;
+ else
+ list = &trace_bprintk_fmt_list;
+
+ if (list->next != &trace_bprintk_fmt_list)
+ return list_entry(list->next, struct trace_bprintk_fmt, list)
+ ->fmt;
+ return NULL;
+}
+
+static void fmt_stop(struct seq_file *m, void *p)
+{
+ unlock_btrace();
+}
+
+static int fmt_show(struct seq_file *m, void *p)
+{
+ seq_printf(m, "addr=%p fmt=%s\n", p, (char *)p);
+ return 0;
+}
+
+static struct seq_operations trace_bprintk_fmt_seq_ops = {
+ .start = fmt_start,
+ .next = fmt_next,
+ .stop = fmt_stop,
+ .show = fmt_show,
+};
+
+static int fmt_open(struct inode *inode, struct file *file)
+{
+ int ret = seq_open(file, &trace_bprintk_fmt_seq_ops);
+ if (!ret)
+ get_btrace_metadata();
+ return ret;
+}
+
+static int fmt_release(struct inode *inode, struct file *file)
+{
+ put_btrace_metadata();
+ return seq_release(inode, file);
+}
+
+struct file_operations trace_bprintk_fmt_fops = {
+ .open = fmt_open,
+ .read = seq_read,
+ .release = fmt_release,
+};
+
/* events tracer */
int trace_bprintk_enable;






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