On Sun, Aug 04, 2024 at 10:37:43AM +0200, Marco Elver wrote:
>
> Well, what I'm saying, having this info also for FREED objects on the
> free stack can be useful in some debugging scenarios when you get a
> use-after-free, and you want to know the elapsed time since the free
> happened. I have done this calculation manually before, which is why I
> suggested it. Maybe it's not useful for you for finding leaks, but
> that's just one usecase.
>
Agreed with your concern scenarios.
How about the following change with additonal object state info?
+ u64 interval_nsec = local_clock() - meta->alloc_track.ts_nsec;
+ unsigned long rem_interval_nsec = do_div(interval_nsec, NSEC_PER_SEC);
/* Timestamp matches printk timestamp format. */
- seq_con_printf(seq, "%s by task %d on cpu %d at %lu.%06lus:\n",
+ seq_con_printf(seq, "%s by task %d on cpu %d at %lu.%06lus (%lu.%06lus ago) for %s object:\n",
show_alloc ? "allocated" : "freed", track->pid,
- track->cpu, (unsigned long)ts_sec, rem_nsec / 1000);
+ track->cpu, (unsigned long)ts_sec, rem_nsec / 1000,
+ (unsigned long)interval_nsec, rem_interval_nsec / 1000,
+ meta->state == KFENCE_OBJECT_ALLOCATED? "allocated" : "freed");
In this way, we can find leaks by grep "allocated object" and inspect the elapsed time of
use-after-free by grep "freed object".
Thanks
Qiwu
