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: Abhishek Sagar <sagar.abhishek@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index d123816..85e8413 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -21,6 +21,7 @@
#include <linux/hardirq.h>
#include <linux/kthread.h>
#include <linux/uaccess.h>
+#include <linux/kprobes.h>
#include <linux/ftrace.h>
#include <linux/sysctl.h>
#include <linux/ctype.h>
@@ -500,6 +501,10 @@
if (rec->flags & FTRACE_FL_FAILED)
continue;
+ /* ignore updates to this record's mcount site */
+ if (get_kprobe((void *)rec->ip))
+ continue;
+
failed = __ftrace_replace_code(rec, old, new, enable);
if (failed && (rec->flags & FTRACE_FL_CONVERTED)) {
rec->flags |= FTRACE_FL_FAILED;
@@ -692,11 +697,11 @@
static int __ftrace_update_code(void *ignore)
{
+ int i, save_ftrace_enabled;
+ cycle_t start, stop;
struct dyn_ftrace *p;
struct hlist_node *t, *n;
- int save_ftrace_enabled;
- cycle_t start, stop;
- int i;
+ struct hlist_head *head, temp_list;
/* Don't be recording funcs now */
ftrace_record_suspend++;
@@ -708,8 +713,11 @@
/* No locks needed, the machine is stopped! */
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 */
- 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
* freed. */
if (p->flags & FTRACE_FL_FAILED)
@@ -723,6 +731,19 @@
if (p->flags & (FTRACE_FL_CONVERTED))
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)) {
p->flags |= FTRACE_FL_CONVERTED;
ftrace_update_cnt++;
@@ -734,6 +755,12 @@
}
}
}
+
+ 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());