Re: Why is irq_stack_union a union?

From: Andy Lutomirski
Date: Mon Aug 31 2015 - 18:02:09 EST

On Mon, Aug 31, 2015 at 2:47 PM, Brian Gerst <brgerst@xxxxxxxxx> wrote:
> On Mon, Aug 31, 2015 at 5:00 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> 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.

Would a struct not make more sense, then?


> --
> Brian Gerst

Andy Lutomirski
AMA Capital Management, LLC
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