Re: [PATCH 3/9] x86/entry/32: fix the end of the stack for newly forked tasks

From: Josh Poimboeuf
Date: Tue Sep 20 2016 - 23:25:23 EST

On Tue, Sep 20, 2016 at 09:10:55PM -0400, Brian Gerst wrote:
> Dropping asmlinkage from schedule_tail() would be a better option if possible.

My understanding is that it's still needed for ia64. AFAICT, ia64
relies on schedule_tail() having the syscall_linkage function attribute.
>From the gcc manual:

This attribute is used to modify the IA64 calling convention by
marking all input registers as live at all function exits. This makes
it possible to restart a system call after an interrupt without having
to save/restore the input registers. This also prevents kernel data
from leaking into application code.

And the ia64 entry code has some similar language:

* Invoke schedule_tail(task) while preserving in0-in7, which may be needed
* in case a system call gets restarted.