From: Matt Fleming <matt@codeblueprint.co.uk>
To: Ingo Molnar <mingo@kernel.org>
Cc: Alex Thorlton <athorlton@sgi.com>,
linux-kernel@vger.kernel.org, Dimitri Sivanich <sivanich@sgi.com>,
Russ Anderson <rja@sgi.com>, Mike Travis <travis@sgi.com>,
Borislav Petkov <bp@suse.de>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, linux-efi@vger.kernel.org
Subject: Re: [PATCH 2/2] Fix efi_call
Date: Thu, 12 May 2016 12:43:46 +0100 [thread overview]
Message-ID: <20160512114346.GE2728@codeblueprint.co.uk> (raw)
In-Reply-To: <20160512064835.GB30717@gmail.com>
On Thu, 12 May, at 08:48:35AM, Ingo Molnar wrote:
>
> * Alex Thorlton <athorlton@sgi.com> wrote:
>
> > The efi_call assembly code has a slight error that prevents us from
> > using arguments 7 and higher, which will be passed in on the stack.
> >
> > mov (%rsp), %rax
> > mov 8(%rax), %rax
> > ...
> > mov %rax, 40(%rsp)
> >
> > This code goes and grabs the return address for the current stack frame,
> > and puts it on the stack, next the 5th argument for the EFI runtime
> > call. Considering the fact that having the return address in that
> > position on the stack makes no sense, I'm guessing that the intent of
> > this code was actually to grab an argument off the stack frame for this
> > call and place it into the frame for the next one.
> >
> > The small change to that offset (i.e. 8(%rax) to 16(%rax)) ensures that
> > we grab the 7th argument off the stack, and pass it as the 6th argument
> > to the EFI runtime function that we're about to call. This change gets
> > our EFI runtime calls that need to pass more than 6 arguments working
> > again.
>
> I suppose the SGI/UV code is the only one using 7 arguments or more? Might make
> sense to point that out in the changelog.
Yeah, I included that info when I applied this patch.
next prev parent reply other threads:[~2016-05-12 11:43 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-11 19:55 [RFC PATCH 0/2] Fix EFI runtime calls on SGI UV Alex Thorlton
2016-05-11 19:55 ` [PATCH 1/2] Create UV efi_call macros Alex Thorlton
[not found] ` <1462996545-98387-2-git-send-email-athorlton-sJ/iWh9BUns@public.gmane.org>
2016-05-12 6:46 ` Ingo Molnar
[not found] ` <20160512064606.GA30717-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2016-05-12 7:35 ` Ard Biesheuvel
[not found] ` <CAKv+Gu8Z0faffrN8Jnz9fQPkyn6K69cFaRD348w+m_Lv4Jgynw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-05-12 8:17 ` Ingo Molnar
[not found] ` <20160512081739.GA25826-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2016-05-16 23:00 ` Alex Thorlton
2016-05-12 12:06 ` Matt Fleming
2016-05-16 22:58 ` Alex Thorlton
[not found] ` <20160516225840.GL98477-7ppMa7wkY9tKToyKb8PD+Zs2JHu2awxn0E9HWUfgJXw@public.gmane.org>
2016-05-17 12:11 ` Matt Fleming
[not found] ` <20160517121122.GC21993-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>
2016-05-17 20:14 ` Alex Thorlton
2016-05-11 19:55 ` [PATCH 2/2] Fix efi_call Alex Thorlton
[not found] ` <1462996545-98387-3-git-send-email-athorlton-sJ/iWh9BUns@public.gmane.org>
2016-05-12 6:48 ` Ingo Molnar
2016-05-12 11:43 ` Matt Fleming [this message]
[not found] ` <20160512064835.GB30717-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2016-05-16 16:24 ` Alex Thorlton
2016-05-12 11:41 ` Matt Fleming
[not found] ` <20160512114149.GD2728-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>
2016-05-16 16:25 ` Alex Thorlton
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