Commit 1813dc37 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt

tracing: Print trace_bprintk() formats for modules too

The file debugfs/tracing/printk_formats maps the addresses
to the formats that are used by trace_bprintk() so that userspace
tools can read the buffer and be able to decode trace_bprintk events
to get the format saved when reading the ring buffer directly.

This is because trace_bprintk() does not store the format into the
buffer, but just the address of the format, which is hidden in
the kernel memory.

But currently it only exports trace_bprintk()s from the kernel core
and not for modules. The modules need their formats exported
as well.
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 0588fa30
......@@ -89,6 +89,76 @@ static int module_trace_bprintk_format_notify(struct notifier_block *self,
return 0;
}
/*
* The debugfs/tracing/printk_formats file maps the addresses with
* the ASCII formats that are used in the bprintk events in the
* buffer. For userspace tools to be able to decode the events from
* the buffer, they need to be able to map the address with the format.
*
* The addresses of the bprintk formats are in their own section
* __trace_printk_fmt. But for modules we copy them into a link list.
* The code to print the formats and their addresses passes around the
* address of the fmt string. If the fmt address passed into the seq
* functions is within the kernel core __trace_printk_fmt section, then
* it simply uses the next pointer in the list.
*
* When the fmt pointer is outside the kernel core __trace_printk_fmt
* section, then we need to read the link list pointers. The trick is
* we pass the address of the string to the seq function just like
* we do for the kernel core formats. To get back the structure that
* holds the format, we simply use containerof() and then go to the
* next format in the list.
*/
static const char **
find_next_mod_format(int start_index, void *v, const char **fmt, loff_t *pos)
{
struct trace_bprintk_fmt *mod_fmt;
if (list_empty(&trace_bprintk_fmt_list))
return NULL;
/*
* v will point to the address of the fmt record from t_next
* v will be NULL from t_start.
* If this is the first pointer or called from start
* then we need to walk the list.
*/
if (!v || start_index == *pos) {
struct trace_bprintk_fmt *p;
/* search the module list */
list_for_each_entry(p, &trace_bprintk_fmt_list, list) {
if (start_index == *pos)
return &p->fmt;
start_index++;
}
/* pos > index */
return NULL;
}
/*
* v points to the address of the fmt field in the mod list
* structure that holds the module print format.
*/
mod_fmt = container_of(v, typeof(*mod_fmt), fmt);
if (mod_fmt->list.next == &trace_bprintk_fmt_list)
return NULL;
mod_fmt = container_of(mod_fmt->list.next, typeof(*mod_fmt), list);
return &mod_fmt->fmt;
}
static void format_mod_start(void)
{
mutex_lock(&btrace_mutex);
}
static void format_mod_stop(void)
{
mutex_unlock(&btrace_mutex);
}
#else /* !CONFIG_MODULES */
__init static int
module_trace_bprintk_format_notify(struct notifier_block *self,
......@@ -96,6 +166,13 @@ module_trace_bprintk_format_notify(struct notifier_block *self,
{
return 0;
}
static inline const char **
find_next_mod_format(int start_index, void *v, const char **fmt, loff_t *pos)
{
return NULL;
}
static inline void format_mod_start(void) { }
static inline void format_mod_stop(void) { }
#endif /* CONFIG_MODULES */
......@@ -158,20 +235,33 @@ int __ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap)
}
EXPORT_SYMBOL_GPL(__ftrace_vprintk);
static const char **find_next(void *v, loff_t *pos)
{
const char **fmt = v;
int start_index;
if (!fmt)
fmt = __start___trace_bprintk_fmt + *pos;
start_index = __stop___trace_bprintk_fmt - __start___trace_bprintk_fmt;
if (*pos < start_index)
return fmt;
return find_next_mod_format(start_index, v, fmt, pos);
}
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;
format_mod_start();
return find_next(NULL, pos);
}
static void *t_next(struct seq_file *m, void * v, loff_t *pos)
{
(*pos)++;
return t_start(m, pos);
return find_next(v, pos);
}
static int t_show(struct seq_file *m, void *v)
......@@ -210,6 +300,7 @@ static int t_show(struct seq_file *m, void *v)
static void t_stop(struct seq_file *m, void *p)
{
format_mod_stop();
}
static const struct seq_operations show_format_seq_ops = {
......
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