Re: vmalloced stacks on x86_64?

[Linus Torvalds]

On Sat, Oct 25, 2014 at 4:16 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
>
> On brief inspection, grsecurity isn't actually vmallocing the stack.
> It seems to be allocating it the normal way and then vmapping it.
> That allows it to modify sg_set_buf to work on stack addresses (sigh).

Perhaps more importantly, the vmalloc space is a limited resource (at
least on 32-bit), and using vmap probably results in less
fragmentation.

I don't think either is really even an option on 32-bit due to the
limited address space. On 64-bit, maybe a virtually remapped stack
would be ok.

                   Linus
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