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Re: [Qemu-devel] ARM

From: Fabrice Bellard
Subject: Re: [Qemu-devel] ARM
Date: Thu, 10 Jul 2003 10:44:18 +0200
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:0.9.9) Gecko/20020408

Jocelyn Mayer wrote:
> On Wed, 2003-07-09 at 20:35, Daniel Jacobowitz wrote:
>> I was just playing with the ARM support, it's great to see it
>> taking shape :)  Fabrice, are you still investigating it, or does
>> it work for you?  My local ARM setup crashes a few hundred
>> instructions into ld.so; a loop runs for too long and hits the top
>> of the stack.
> Hello,
> Maybe a flag problem.. As I was looking the overflow flag
> calculation, while trying to fix it in my PPC emulation, I noticed
> that this flag should be masked with (1 << 31) to be correct. Fabrice,
> could you confirm this point ?

Yes, the overflow flag should be masked with (1 << 31). For ARM, the
masking does not need to be done as the overflow is computed in a
separate variable.

> It seems to work well in my PPC code...
> It may also comes from the fact that the qemu Elf loader builds a "buggy"
> stack. I don't known anything about the ABI for the ARM, but I noticed
> that the stack wasn't aligned properly on PPC and that some informations
> were missing, but I don't really know if those infos are vital or
> not. Even in x86 emulation, the stack is really different from the
> one built by the Linux kernel (I compared with a linux-2.4.21
> kernel). I fixed some crashes, changing this code to do the same as
> the kernel, but dynamic x86 loading is now buggy with that patch...

Yes, alignment is not done properly yet as the elf loader comes from a very old Linux kernel. If you except the alignment bug, none of the differences should be critical.


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