linux-kernel - Re: [PATCH] EFI x86: pass firmware call parameters on the stack

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Message-Id: <20070130111058.db191e07.akpm@osdl.org>
Date:	Tue, 30 Jan 2007 11:10:58 -0800
From:	Andrew Morton <akpm@...l.org>
To:	Frédéric Riss <frederic.riss@...il.com>,
	Matt Domsch <Matt_Domsch@...l.com>
Cc:	linux-kernel@...r.kernel.org, artiom.myaskouvskey@...el.com,
	bjorn.helgaas@...com,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] EFI x86: pass firmware call parameters on the stack

On Tue, 30 Jan 2007 20:01:18 +0100
Frédéric Riss <frederic.riss@...il.com> wrote:

> 
> When calling into an EFI firmware, the parameters need to be passed on
> the stack. The recent change to use -mregparm=3 breaks x86 EFI support.
> This patch is needed to allow the new Intel-based Macs to suspend to ram
> when run in EFI mode (efi.get_time is called during the suspend phase).
> 
> Signed-off-by: Frederic Riss <frederic.riss@...il.com>
> 
> ---
> 
> [As I couldn't find an official maintainer for the linux/efi.h file and
> the file header is quite old, I'm Cc:ing the last 2 commiters.]

Matt normally looks after EFI.

> This patch fixes the issue for x86, but the file is also used by IA64. I
> would have used asmlinkage to force arguments on the stack, but it has a
> special meaning on IA64, thus I used a raw regparm(0) GCC attribute.
> This attribute is documented only for x86, I hope it has no side effect
> on other archs.

hm, this sounds like a fairly serious problem.  Has this been runtime
tested on ia64 and x86_64>


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