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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>
This commit is contained in:
Abhishek Sagar 2008-06-21 23:50:29 +05:30 committed by Ingo Molnar
parent ecea656d1d
commit f22f9a89ce
1 changed files with 31 additions and 4 deletions
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35
kernel/trace/ftrace.c
View File

@ -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 @@ static void ftrace_replace_code(int enable)
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 @@ unsigned long ftrace_update_tot_cnt;
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 @@ static int __ftrace_update_code(void *ignore)
/* 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 @@ static int __ftrace_update_code(void *ignore)
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 @@ 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());