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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Tue, 7 Mar 2017 09:52:21 -0800
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Subject: Re: v4.10: kernel stack frame pointer .. has bad value (null)
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Pavel Machek <pavel@ucw.cz>,
        kernel list <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@kernel.org>, Andrew Lutomirski <luto@kernel.org>,
        Borislav Petkov <bp@alien8.de>, Brian Gerst <brgerst@gmail.com>,
        Denys Vlasenko <dvlasenk@redhat.com>, Peter Anvin <hpa@zytor.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>
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On Tue, Mar 7, 2017 at 9:38 AM, Josh Poimboeuf <jpoimboe@redhat.com> 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