I'm afraid you all already hate me, but let me continue to spam your
mailboxes.
On 08/25, Oleg Nesterov wrote:
>
> I'll try to play with copy_from_user_in_atomic(), if nothing else just
> to complete the discussion and see how the code can look in this case.
OK, to complete the discussion, the code looks simple unless I missed
something,
if (ia32_fxstate) {
/*
* For 32-bit frames with fxstate, copy the user state to the
* thread's fpu state, reconstruct fxstate from the fsave
* header. Sanitize the copied state etc.
*/
struct xsave_struct *xsave = &tsk->thread.fpu.state->xsave;
struct user_i387_ia32_struct env;
bool done;
if (__copy_from_user(&env, buf, sizeof(env))
return -1;
for (done = false; !done; ) {
if (fatal_signal_pending(current) ||
fault_in_pages_readable(buf_fx, state_size))
return -1;
preempt_disable();
pagefault_disable(); /* not really needed */
done = !__copy_from_user_inatomic(xsave, buf_fx,
state_size);
pagefault_enable();
if (likely(done)) {
sanitize_restored_xstate(tsk, &env, xstate_bv,
fx_only);
if (__thread_has_fpu(tsk))
math_state_restore();
} else {
fpu_finit(&tsk->thread.fpu);
}
preempt_enable();
}
return 0;
}
and in some sense it is even simpler because we do not care about
use_eager_fpu() or set/clear_used_math().
Does it look better than switch_fpu_xstate() hack?
However, this code can race with kernel_fpu_begin() if use_eager_fpu().
I _think_ that kernel_fpu_begin/end and irq_fpu_usable() need cleanups
too and in any case. Will try to do, but I am not sure.
And to spam you even more, I'll send you a couple of other, more simple
cleanups.
Oleg.
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