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Re: [Qemu-devel] qemu-ppc can't run static uClibc binaries.

From: Alexander Graf
Subject: Re: [Qemu-devel] qemu-ppc can't run static uClibc binaries.
Date: Mon, 15 Feb 2010 14:01:02 +0100

On 15.02.2010, at 13:58, Rob Landley wrote:

> On Monday 15 February 2010 05:19:24 Alexander Graf wrote:
>> On 15.02.2010, at 12:10, Rob Landley wrote:
>>> On Sunday 14 February 2010 08:41:00 Alexander Graf wrote:
>>>> So the only case I can imagine that this breaks anything is that
>>>> uClibc requires register state to be 0.
>>> Yes, r3 (which is the exit code from the "exec" syscall, and thus 0 if it
>>> worked).  In the BSD layout, it's argc (which can never be 0).
>>> http://lists.gnu.org/archive/html/qemu-devel/2007-03/msg00720.html
>> So what you really want is something like
>> /* exec return value is always 0 */
>> env->gpr[3] = 0;
>> #endif
>> just after the #endif in your patch. If you had inlined your patch I
>> could've commented it there.
> Unfortunately kmail plays fast and loose with whitespace when I inline stuff. 
> (Not always, but I can't tell by inspection when it's decided it was hungry 
> for tabs or wanted to throw in that horrible UTF8 escaped whitespace.)

git-send-mail is your friend :-).

> I didn't explicitly set it because they're initialized to zero in function 
> main() on line 2654 of linux-user/main.c.  (Any regs we don't explicitly set 
> to some other value start out zeroed in qemu.)

So it should work already?

> If you prefer to make the requirements explicit, that works too, but a 
> comment 
> might do just as well.  (I tend to prefer removing unnecessary work Linux 
> doesn't need done, rather than adding extra code to undo the unnecessary work 
> afterwards.  Force of habit from years on busybox and such.)

Well, I personally prefer to always use the same code paths whenever possible. 
That makes the code less prone to failure in odd configurations. And we have a 
lot of different combinations of those in Qemu.

But this is Riku's call. He's the linux-user maintainer.


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