linux-kernel - Re: [off-list] a path toward killing thread

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Message-ID: <CALCETrWp6y9WQJ6NvZFZa58=EkobdK7LYzRKk1hOCX-94ck=CA@mail.gmail.com>
Date:	Fri, 17 Jun 2016 16:24:07 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Kees Cook <keescook@...omium.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [off-list] a path toward killing thread_info

On Fri, Jun 17, 2016 at 4:04 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
> On Fri, Jun 17, 2016 at 03:41:49PM -0700, Andy Lutomirski wrote:
>
>> PeterZ, I'm thinking of adding task_ti_flags_ptr to directly find the
>> ti flags word given a task_struct * so the scheduler can use it.  Does
>> that seem reasonable to you?
>
> What are you trying to do?  Merge task_struct and thread_info?

Merge thread_struct and thread_info, actually.  The only functional
thing that thread_info provides is a place for arches to stash stuff.
I also want to end the era of stack overflows smashing data structures
at a fixed offset.

If we kill thread_info (on x86, anyway) and enable virtually mapped
stacks (which I just emailed out v2 of), then a stack overflow will
just OOPS cleanly on x86 without clobbering anything.