Quoting Sukadev Bhattiprolu (sukadev@xxxxxxxxxxxxxxxxxx):
> | I think Suka's suggestion is again inherently limited (in # of
> | clone flags) and will force even uglier syscalls for each arch than the
> | previous one already does.
> |
>
> Yes other architectures are forced to ignore the flags_high and copy-in the
> tid pointers.
>
> But if we want more than 64 bit flags, we may need follow the sigset_t
> model ?
>
> Also, I am listing three approaches below. Do you prefer #2 below ?
I prefer #2 with 'struct pid_set' renamed to clone_ext_data or something,
and either a version # or int num_clone_words so we can add clone flags
later. I know, adding more then 32 more clone flags seems unlikely, but...
> 1. =====
>
> struct clone_tid_info {
> void *parent_tid; /* parent_tid_ptr parameter */
> void *child_tid; /* child_tid_ptr parameter */
> };
>
> struct pid_set {
> int num_pids;
> pid_t *pids;
> };
>
> int clone_extended(int flags_low, int flags_high, void *child_stack,
> void *unused, struct clone_tid_info *tid_ptrs,
> struct pid_set *pid_setp);
>
> 2. ======
>
> struct clone_info {
> int flags_high;
> struct pid_set pid_set;
> }
>
> int clone_extended(int flags_low, void *child_stack, void *unused,
> int *parent_tid, int *child_tid, struct clone_info *clone_info);
>
>
> Pros:
> - copy_from_user() needed only for new flags and pid_set
>
> Cons:
> - splitting the high and low clone-flags is awkward ?
>
> 3. =====
>
> typedef struct {
> unsigned long flags[N_CLONE_FLAGS];
> } clone_flags_t;
>
> int clone_extended(clone_flags_t *flags, void *child_stack, int *unused,
> int *parent_tid, int *child_tid, struct pid_set *pid_set);
>
>
> Pros:
> - extendible clone_flags (like sigset_t)
> - no copy_from_user() when we have 32 clone-flags
> - no copy_from_user for tids
>
> Cons:
> - copy_from_user() needed on 32-bit architectures for all flags
> when they exceed 32.
>
>
> Sukadev
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