| 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 ?
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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