Re: [PATCH] x86: entry_32.S: change ESPFIX test to not touch PT_OLDSS(%esp)

[Andy Lutomirski]

On Mon, Mar 9, 2015 at 11:16 AM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Mon, Mar 9, 2015 at 11:04 AM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
>>
>> One option would be to change the NMI entry code to move itself down 8
>> bytes if this happens (came from kernel mode or sp == sp0 - 12,
>> perhaps).
>
> Hmm. That whole code currently depends on the stack setup being just a
> single instruction (the move to esp). And that simplifies things, I'd
> like to keep it that way.
>
> I'd *much* rather just keep the 8-byte padding. What was so
> problematic with that? It worked. It's been around forever. Removing
> it is the bug.

Let's at least fix it, then.  processor.h has:

#define INIT_TSS  {                              \
    .x86_tss = {                              \
        .sp0        = sizeof(init_stack) + (long)&init_stack, \

(moved in -tip)

That's bogus, and this bogosity is why I broke 32-bit -next in the
first place: I assumed it was correct.

I'll get it if no one beats me to it.

--Andy

>
>                         Linus



-- 
Andy Lutomirski
AMA Capital Management, LLC
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/