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Re: [Qemu-devel] bug in new ubfx code


From: Richard Henderson
Subject: Re: [Qemu-devel] bug in new ubfx code
Date: Fri, 13 Jan 2017 09:39:34 -0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.6.0

On 01/13/2017 09:27 AM, Ard Biesheuvel wrote:
> Hi all,
> 
> I tracked down a boot issue I was having with running the kernel under
> AArch64 system emulation to commit
> 
> It appears that ubfx is executing incorrectly: the following code
> 
>     .global _start
> _start:
>     mov x1, #0x1124
>     ubfx x2, x1, #28, #4
> 
> built with
> 
> aarch64-linux-gnu-gcc -o /tmp/ubfx /tmp/ubfx.s -nostartfiles
> aarch64-linux-gnu-objcopy -O binary /tmp/ubfx.bin /tmp/ubfx
> 
> and executed with
> 
> qemu-system-aarch64 -M virt -cpu cortex-a53 -kernel /tmp/ubfx -s -S -nographic
> 
> produces the value 0x1124000000000 in x2 (as can be observed via GDB),
> while the expected value is 0

Ho hum.  Somehow the relevant patch was corrupted.  It has half of
Alex's fix in

  http://lists.nongnu.org/archive/html/qemu-devel/2016-12/msg00137.html

but is also missing half.  I'll fix it up asap.


r~



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