Le 02/06/2017 à 11:26, Michael Ellerman a écrit :
Christophe Leroy <christophe.le...@c-s.fr> writes:
Only the get_user() in store_updates_sp() has to be done outside
the mm semaphore. All the comparison can be done within the semaphore,
so only when really needed.
As we got a DSI exception, the address pointed by regs->nip is
obviously valid, otherwise we would have had a instruction exception.
So __get_user() can be used instead of get_user()
I don't think that part is true.
You took a DSI so there *was* an instruction at NIP, but since then it
may have been unmapped by another thread.
So I don't think you can assume the get_user() will succeed.
The difference between get_user() and __get_user() is that get_user()
performs an access_ok() in addition.
Doesn't access_ok() only checks whether addr is below TASK_SIZE to
ensure it is a valid user address ?
Christophe
