From: Brian Gerst <brgerst@gmail.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
X86 ML <x86@kernel.org>, Steven Rostedt <rostedt@goodmis.org>,
Andi Kleen <andi@firstfloor.org>
Subject: Re: Why is irq_stack_union a union?
Date: Mon, 31 Aug 2015 17:47:46 -0400 [thread overview]
Message-ID: <CAMzpN2iUWaQrYBXrSHM+BuoOKZ3Kc1=ErNEw02tV0K6KUWZLhg@mail.gmail.com> (raw)
In-Reply-To: <CALCETrUUSyfZzQUOya9fLOewehOzm-vkLpPhMriJquFLvSzw6Q@mail.gmail.com>
On Mon, Aug 31, 2015 at 5:00 PM, Andy Lutomirski <luto@amacapital.net> wrote:
> Why not just a struct? Also, why is this all tangled up in gsbase initialization?
It has to do with the fact that the GCC stackprotector is hardcoded to
look for the canary at %gs:40. Since we also use %gs for the percpu
segment, we have to make sure that the canary is placed at the start
of the percpu section. Overlaying it onto the bottom of the IRQ stack
and was the most convenient way to do it, with a side benefit that
overflowing the stack will trip the canary.
--
Brian Gerst
next prev parent reply other threads:[~2015-08-31 21:47 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-31 21:00 Why is irq_stack_union a union? Andy Lutomirski
2015-08-31 21:47 ` Brian Gerst [this message]
2015-08-31 22:01 ` Andy Lutomirski
2015-09-01 3:55 ` Brian Gerst
2015-09-01 21:42 ` Andy Lutomirski
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