Re: [PATCH v5 03/15] sched.h: introduce TASK_COMM_LEN_16

[Yafang Shao]

On Fri, Oct 22, 2021 at 5:55 AM Andrii Nakryiko
<andrii.nakryiko@xxxxxxxxx> wrote:
>
> On Wed, Oct 20, 2021 at 8:45 PM Yafang Shao <laoar.shao@xxxxxxxxx> wrote:
> >
> > There're many hard-coded 16 used to store task comm in the kernel, that
> > makes it error prone if we want to change the value of TASK_COMM_LEN. A
> > new marco TASK_COMM_LEN_16 is introduced to replace these old ones, then
> > we can easily grep them.
> >
> > Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> > Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> > Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> > Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> > Cc: Petr Mladek <pmladek@xxxxxxxx>
> > ---
> >  include/linux/sched.h | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/include/linux/sched.h b/include/linux/sched.h
> > index c1a927ddec64..62d5b30d310c 100644
> > --- a/include/linux/sched.h
> > +++ b/include/linux/sched.h
> > @@ -274,6 +274,8 @@ struct task_group;
> >
> >  #define get_current_state()    READ_ONCE(current->__state)
> >
> > +/* To replace the old hard-coded 16 */
> > +#define TASK_COMM_LEN_16               16
> >  /* Task command name length: */
> >  #define TASK_COMM_LEN                  16
>
> Can we please convert these two constants into enum? That will allow
> BPF applications to deal with such kernel change more easily because
> these constants will now be available as part of kernel BTF.
>
> Something like this should be completely equivalent for all the kernel uses:
>
> enum {
>     TASK_COMM_LEN = 16,
>     TASK_COMM_LEN_16 = 16,
> };
>
> When later TASK_COMM_LEN is defined as = 24, BPF applications will be
> able to deal with that by querying BTF through BPF CO-RE.
>

Sure. I will convert it to enum.


-- 
Thanks
Yafang