linux-kernel - Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core)

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Message-ID: <CA+55aFyYruc_7Ax-hjh96zXPWmJJpCqm0yqq-fYpT094owSO_Q@mail.gmail.com>
Date:	Thu, 23 Jun 2016 11:46:41 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Andy Lutomirski <luto@...nel.org>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	Borislav Petkov <bp@...en8.de>,
	Nadav Amit <nadav.amit@...il.com>,
	Kees Cook <keescook@...omium.org>,
	Brian Gerst <brgerst@...il.com>,
	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Jann Horn <jann@...jh.net>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core)

On Thu, Jun 23, 2016 at 10:52 AM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Ugh. Looking around at this, it turns out that a great example of this
> kind of legacy issue is the debug_mutex stuff.

Interestingly, the *only* other user of ti->task for a full
allmodconfig build of x86-64 seems to be

  arch/x86/kernel/dumpstack.c

with the print_context_stack() -> print_ftrace_graph_addr() -> task =
tinfo->task chain.

And that doesn't really seem to want thread_info either. The callers
all have 'task', and have to generate thread_info from that anyway.

So this attached patch (which includes the previous one) seems to
build. I didn't actually boot it, but there should be no users left
unless there is some asm code that has hardcoded offsets..

                 Linus

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