Commit ecea656d authored by Abhishek Sagar's avatar Abhishek Sagar Committed by Ingo Molnar
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ftrace: freeze kprobe'd records 



Let records identified as being kprobe'd be marked as "frozen". The trouble
with records which have a kprobe installed on their mcount call-site is
that they don't get updated. So if such a function which is currently being
traced gets its tracing disabled due to a new filter rule (or because it
was added to the notrace list) then it won't be updated and continue being
traced. This patch allows scanning of all frozen records during tracing to
check if they should be traced.

Signed-off-by: default avatarAbhishek Sagar <sagar.abhishek@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 785656a4

include/linux/ftrace.h

+5 −1
Original line number Diff line number Diff line
@@ -49,6 +49,7 @@ enum { 
	FTRACE_FL_ENABLED	= (1 << 3),

	FTRACE_FL_NOTRACE	= (1 << 4),

	FTRACE_FL_CONVERTED	= (1 << 5),

	FTRACE_FL_FROZEN	= (1 << 6),

};



struct dyn_ftrace {
@@ -73,15 +74,18 @@ extern void ftrace_caller(void); 
extern void ftrace_call(void);

extern void mcount_call(void);



extern int skip_trace(unsigned long ip);



void ftrace_disable_daemon(void);

void ftrace_enable_daemon(void);



#else

# define skip_trace(ip)				({ 0; })

# define ftrace_force_update()			({ 0; })

# define ftrace_set_filter(buf, len, reset)	do { } while (0)

# define ftrace_disable_daemon()		do { } while (0)

# define ftrace_enable_daemon()			do { } while (0)

#endif

#endif /* CONFIG_DYNAMIC_FTRACE */



/* totally disable ftrace - can not re-enable after this */

void ftrace_kill(void);

kernel/trace/ftrace.c

+71 −1
Original line number Diff line number Diff line
@@ -163,6 +163,8 @@ enum { 
};



static int ftrace_filtered;

static int tracing_on;

static int frozen_record_count;



static struct hlist_head ftrace_hash[FTRACE_HASHSIZE];
@@ -195,6 +197,71 @@ static int ftrace_record_suspend; 


static struct dyn_ftrace *ftrace_free_records;





#ifdef CONFIG_KPROBES

static inline void freeze_record(struct dyn_ftrace *rec)

{

	if (!(rec->flags & FTRACE_FL_FROZEN)) {

		rec->flags |= FTRACE_FL_FROZEN;

		frozen_record_count++;

	}

}



static inline void unfreeze_record(struct dyn_ftrace *rec)

{

	if (rec->flags & FTRACE_FL_FROZEN) {

		rec->flags &= ~FTRACE_FL_FROZEN;

		frozen_record_count--;

	}

}



static inline int record_frozen(struct dyn_ftrace *rec)

{

	return rec->flags & FTRACE_FL_FROZEN;

}

#else

# define freeze_record(rec)			({ 0; })

# define unfreeze_record(rec)			({ 0; })

# define record_frozen(rec)			({ 0; })

#endif /* CONFIG_KPROBES */



int skip_trace(unsigned long ip)

{

	unsigned long fl;

	struct dyn_ftrace *rec;

	struct hlist_node *t;

	struct hlist_head *head;



	if (frozen_record_count == 0)

		return 0;



	head = &ftrace_hash[hash_long(ip, FTRACE_HASHBITS)];

	hlist_for_each_entry_rcu(rec, t, head, node) {

		if (rec->ip == ip) {

			if (record_frozen(rec)) {

				if (rec->flags & FTRACE_FL_FAILED)

					return 1;



				if (!(rec->flags & FTRACE_FL_CONVERTED))

					return 1;



				if (!tracing_on || !ftrace_enabled)

					return 1;



				if (ftrace_filtered) {

					fl = rec->flags & (FTRACE_FL_FILTER |

							   FTRACE_FL_NOTRACE);

					if (!fl || (fl & FTRACE_FL_NOTRACE))

						return 1;

				}

			}

			break;

		}

	}



	return 0;

}



static inline int

ftrace_ip_in_hash(unsigned long ip, unsigned long key)

{
@@ -489,8 +556,11 @@ static int __ftrace_modify_code(void *data) 
		 */

		__ftrace_update_code(NULL);

		ftrace_replace_code(1);

	} else if (*command & FTRACE_DISABLE_CALLS)

		tracing_on = 1;

	} else if (*command & FTRACE_DISABLE_CALLS) {

		ftrace_replace_code(0);

		tracing_on = 0;

	}



	if (*command & FTRACE_UPDATE_TRACE_FUNC)

		ftrace_update_ftrace_func(ftrace_trace_function);

kernel/trace/trace.c

+3 −0
Original line number Diff line number Diff line
@@ -988,6 +988,9 @@ function_trace_call(unsigned long ip, unsigned long parent_ip) 
	if (unlikely(!tracer_enabled))

		return;



	if (skip_trace(ip))

		return;



	local_irq_save(flags);

	cpu = raw_smp_processor_id();

	data = tr->data[cpu];

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