Re: [PATCH 2/7] stm class: Replace uuid_t with plain u8 uuid[16]

From: Andy Shevchenko
Date: Wed Apr 14 2021 - 13:48:00 EST


On Wed, Apr 14, 2021 at 07:33:38PM +0200, Greg Kroah-Hartman wrote:
> On Wed, Apr 14, 2021 at 08:12:46PM +0300, Alexander Shishkin wrote:
> > From: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> >
> > It appears that uuid_t use in STM code abuses UUID API.
>
> How is it being abused?

We are using it against the buffer that is u8, and neither uuid_t nor guid_t.

> Moreover,
> > this type is only useful when we parse user input. Due to above
> > replace uuid_t with u8 uuid[16] and use uuid_t only when parse
> > user input.
> >
> > Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> > Signed-off-by: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
> > ---
> > drivers/hwtracing/stm/p_sys-t.c | 16 ++++++++++------
> > 1 file changed, 10 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/hwtracing/stm/p_sys-t.c b/drivers/hwtracing/stm/p_sys-t.c
> > index 360b5c03df95..04d13b3785d3 100644
> > --- a/drivers/hwtracing/stm/p_sys-t.c
> > +++ b/drivers/hwtracing/stm/p_sys-t.c
> > @@ -76,7 +76,7 @@ enum sys_t_message_string_subtype {
> > MIPI_SYST_SEVERITY(MAX))
> >
> > struct sys_t_policy_node {
> > - uuid_t uuid;
> > + u8 uuid[UUID_SIZE];
>
> This feels wrong, what is wrong with the uuid_t type usage here?

Nothing, just will require additional export_uuid() / import_uuid() call.

> > bool do_len;
> > unsigned long ts_interval;
> > unsigned long clocksync_interval;
> > @@ -92,7 +92,7 @@ static void sys_t_policy_node_init(void *priv)
> > {
> > struct sys_t_policy_node *pn = priv;
> >
> > - generate_random_uuid(pn->uuid.b);
>
> Ok, that's not good, but that looks to be a flaw in the
> generate_random_uuid() api, not this driver implementation.
>
> I don't understand why this change is needed?

Using raw buffer APIs against uuid_t / guid_t.

We can import_uuid() first and call uuid_gen() against it. Will it work for
you?

--
With Best Regards,
Andy Shevchenko