Re: v4.10: kernel stack frame pointer .. has bad value (null)

From: Linus Torvalds
Date: Tue Mar 07 2017 - 14:44:32 EST


On Tue, Mar 7, 2017 at 9:38 AM, Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote:
>
> So I'm thinking we should have -maccumulate-outgoing-args always enabled
> on x86_32 just like we already do on x86_64.

Ugh. I realize we have workarounds for bugs, but I think
-maccumulate-outgoing-args is nasty. It just generates worse code by
avoiding the much nicer push/pop sequences, afaik.

On x86-64 it's not such a big deal, because we pass the first six
arguments in registers anyway, so the arguments on the stack is a
fairly unusual special case.

But on x86-32, we only have three argument registers, so this
braindamage is potentially worse.

I guess we already do this in most situations due to the gcc bugs, but
I do think it's sad that we would do it for our _own_ bugs too.

Linus