On Wed, Dec 05, 2012 at 04:08:41PM +0000, James Hogan wrote:
> +TBIRES tail_end(TBIRES State, unsigned long orig_syscall)
> +{
> + struct pt_regs *regs = (struct pt_regs *)State.Sig.pCtx;
> + unsigned long flags;
> +
> + if (user_mode(regs)) {
> + local_irq_enable();
> + /* This is actually a crucial little line - if the process
> + * needs swapping out, then this is where it happens!
> + */
> + if (need_resched())
> + schedule();
> +
> + flags = current_thread_info()->flags;
> + if (flags & (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME)) {
> + /* Note the passing in of the original syscall number.
> + * This is used for implementing signal restart.
> + */
> + do_notify_resume(regs, orig_syscall != 0,
> + orig_syscall, flags);
Owww.... So
a) you can't get there with !user_mode(regs)
b) you handle only one signal (what happens if you fail sigframe
allocation, BTW? Sure, you get SIGSEGV delivered. And don't handle it.)
c) you read ->flags with no protection whatsoever. It should be
done *before* you enable interrupts, and rechecked after you've done
do_notify_resume() and redisabled them. The same for schedule(). It really
should be a loop; take a look at how it's done on arm and alpha - there that
loop is in C, not in asm glue.
d) looks like your sigreturn is, indeed, broken. It should *not* have
syscall restart logics triggered at all.
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