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Commit f22f9a89 authored by Abhishek Sagar's avatar Abhishek Sagar Committed by Ingo Molnar
Browse files

ftrace: avoid modifying kprobe'd records 



Avoid modifying the mcount call-site if there is a kprobe installed on it.
These records are not marked as failed however. This allowed the filter
rules on them to remain up-to-date. Whenever the kprobe on the corresponding
record is removed, the record gets updated as normal.

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 ecea656d

kernel/trace/ftrace.c

+31 −4
Original line number Original line Diff line number Diff line
@@ -21,6 +21,7 @@ 
#include <linux/hardirq.h>

#include <linux/hardirq.h>

#include <linux/kthread.h>

#include <linux/kthread.h>

#include <linux/uaccess.h>

#include <linux/uaccess.h>

#include <linux/kprobes.h>

#include <linux/ftrace.h>

#include <linux/ftrace.h>

#include <linux/sysctl.h>

#include <linux/sysctl.h>

#include <linux/ctype.h>

#include <linux/ctype.h>
@@ -500,6 +501,10 @@ static void ftrace_replace_code(int enable) 
			if (rec->flags & FTRACE_FL_FAILED)

			if (rec->flags & FTRACE_FL_FAILED)

				continue;

				continue;





			/* ignore updates to this record's mcount site */

			if (get_kprobe((void *)rec->ip))

				continue;



			failed = __ftrace_replace_code(rec, old, new, enable);

			failed = __ftrace_replace_code(rec, old, new, enable);

			if (failed && (rec->flags & FTRACE_FL_CONVERTED)) {

			if (failed && (rec->flags & FTRACE_FL_CONVERTED)) {

				rec->flags |= FTRACE_FL_FAILED;

				rec->flags |= FTRACE_FL_FAILED;
@@ -692,11 +697,11 @@ unsigned long ftrace_update_tot_cnt; 




static int __ftrace_update_code(void *ignore)

static int __ftrace_update_code(void *ignore)

{

{

	int i, save_ftrace_enabled;

	cycle_t start, stop;

	struct dyn_ftrace *p;

	struct dyn_ftrace *p;

	struct hlist_node *t, *n;

	struct hlist_node *t, *n;

	int save_ftrace_enabled;

	struct hlist_head *head, temp_list;

	cycle_t start, stop;

	int i;





	/* Don't be recording funcs now */

	/* Don't be recording funcs now */

	ftrace_record_suspend++;

	ftrace_record_suspend++;
@@ -708,8 +713,11 @@ static int __ftrace_update_code(void *ignore) 




	/* No locks needed, the machine is stopped! */

	/* No locks needed, the machine is stopped! */

	for (i = 0; i < FTRACE_HASHSIZE; i++) {

	for (i = 0; i < FTRACE_HASHSIZE; i++) {

		INIT_HLIST_HEAD(&temp_list);

		head = &ftrace_hash[i];



		/* all CPUS are stopped, we are safe to modify code */

		/* all CPUS are stopped, we are safe to modify code */

		hlist_for_each_entry_safe(p, t, n, &ftrace_hash[i], node) {

		hlist_for_each_entry_safe(p, t, n, head, node) {

			/* Skip over failed records which have not been

			/* Skip over failed records which have not been

			 * freed. */

			 * freed. */

			if (p->flags & FTRACE_FL_FAILED)

			if (p->flags & FTRACE_FL_FAILED)
@@ -723,6 +731,19 @@ static int __ftrace_update_code(void *ignore) 
			if (p->flags & (FTRACE_FL_CONVERTED))

			if (p->flags & (FTRACE_FL_CONVERTED))

				break;

				break;





			/* Ignore updates to this record's mcount site.

			 * Reintroduce this record at the head of this

			 * bucket to attempt to "convert" it again if

			 * the kprobe on it is unregistered before the

			 * next run. */

			if (get_kprobe((void *)p->ip)) {

				ftrace_del_hash(p);

				INIT_HLIST_NODE(&p->node);

				hlist_add_head(&p->node, &temp_list);

				continue;

			}



			/* convert record (i.e, patch mcount-call with NOP) */

			if (ftrace_code_disable(p)) {

			if (ftrace_code_disable(p)) {

				p->flags |= FTRACE_FL_CONVERTED;

				p->flags |= FTRACE_FL_CONVERTED;

				ftrace_update_cnt++;

				ftrace_update_cnt++;
@@ -734,6 +755,12 @@ static int __ftrace_update_code(void *ignore) 
				}

				}

			}

			}

		}

		}



		hlist_for_each_entry_safe(p, t, n, &temp_list, node) {

			hlist_del(&p->node);

			INIT_HLIST_NODE(&p->node);

			hlist_add_head(&p->node, head);

		}

	}

	}





	stop = ftrace_now(raw_smp_processor_id());

	stop = ftrace_now(raw_smp_processor_id());