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Re: [Qemu-devel] [PATCH] ARM (Thumb) read from R15

From: Paul Brook
Subject: Re: [Qemu-devel] [PATCH] ARM (Thumb) read from R15
Date: Mon, 2 Jul 2007 14:17:23 +0100
User-agent: KMail/1.9.7

On Monday 02 July 2007, Ulrich Hecht wrote:
> On Saturday 30 June 2007 04:19, Paul Brook wrote:
> > > QEMU does not set the Thumb bit when reading from R15 in Thumb mode.
> >
> > Neither does real hardware.
> You are, unsurprisingly, right. The problem seems to be a different one.
> Quoting the ARM on "pop pc":
> "In ARM architecture 5 and above, bit[0] of the loaded value determines
> whether execution continues after this branch in ARM state or in Thumb
> state[...] In T variants of architecture version 4, bit[0] of the loaded
> value is ignored and execution continues in Thumb state[...]"
> My code is supposed to run on a 4T. I guess I'll have to implement an

As you have found out, qemu doesn't currently emulate v4t. There are a couple 
of other instructions that should be disabled (blx) if you do this.


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