On Wed, 2013-03-20 at 12:18 +0900, kpark3...@gmail.com wrote:
> From: Sahara <keun-o.p...@windriver.com>
>
> Somehow tracepoint_entry_add/remove_probe functions allow a null probe
> function.
You actually hit this in practice, or is this just something that you
observe from code review?
> Especially on getting a null probe in remove function, it seems
> to be used to remove all probe functions in the entry.
Hmm, that actually sounds like a feature.
> But, the code is not handled as expected. Since the tracepoint_entry
> maintains funcs array's last func as NULL in order to mark it as the end
> of the array. Also NULL func is used in for-loop to check out the end of
> the loop. So if there's NULL func in the entry's funcs, the for-loop
> will be abruptly ended in the middle of operation.
> Also checking out if probe is null in for-loop is not efficient.
>
> Signed-off-by: Sahara <keun-o.p...@windriver.com>
> ---
> kernel/tracepoint.c | 18 ++++++++++++------
> 1 files changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
> index 0c05a45..30f427e 100644
> --- a/kernel/tracepoint.c
> +++ b/kernel/tracepoint.c
> @@ -112,7 +112,10 @@ tracepoint_entry_add_probe(struct tracepoint_entry
> *entry,
> int nr_probes = 0;
> struct tracepoint_func *old, *new;
>
> - WARN_ON(!probe);
> + if (unlikely(!probe)) {
> + WARN_ON(!probe);
> + return ERR_PTR(-EINVAL);
> + }
Um, you want:
if (WARN_ON(!probe))
return ERR_PTR(-EINVAL);
>
> debug_print_probes(entry);
> old = entry->funcs;
> @@ -147,15 +150,19 @@ tracepoint_entry_remove_probe(struct tracepoint_entry
> *entry,
>
> old = entry->funcs;
>
> + if (unlikely(!probe)) {
> + WARN_ON(!probe);
> + return ERR_PTR(-EINVAL);
> + }
Here too if it wasn't intended to allow removal of all probes from a
tracepoint.
> +
> if (!old)
> return ERR_PTR(-ENOENT);
>
> debug_print_probes(entry);
> /* (N -> M), (N > 1, M >= 0) probes */
> for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
> - if (!probe ||
> - (old[nr_probes].func == probe &&
> - old[nr_probes].data == data))
> + if (old[nr_probes].func == probe &&
> + old[nr_probes].data == data)
> nr_del++;
> }
>
> @@ -173,8 +180,7 @@ tracepoint_entry_remove_probe(struct tracepoint_entry
> *entry,
> if (new == NULL)
> return ERR_PTR(-ENOMEM);
> for (i = 0; old[i].func; i++)
> - if (probe &&
> - (old[i].func != probe || old[i].data != data))
> + if (old[i].func != probe || old[i].data != data)
This makes it look like the null probe was intentional.
-- Steve
> new[j++] = old[i];
> new[nr_probes - nr_del].func = NULL;
> entry->refcount = nr_probes - nr_del;
--
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