Re: [Qemu-devel] armv7m/stm32f205 not starting if code linked from 0x08000000

[Liviu Ionescu]

> On 08 Jun 2015, at 21:36, Peter Maydell <address@hidden> wrote:
> 
> OK, so the problem diagnosis is right. I'm playing around with
> a patch which postpones PC/SP load until we start execution.

but is this really necessary? 

the configuration at the moment cpu_reset is called is perfectly stable, all 
memory regions are defined, the image was loaded, etc.

why not fetch the msp & pc from the correct location and proceed as now?

my feeling is that this will potentially create other problems.

> There are some awkward issues there, though: if you're running
> QEMU under a debugger and you look at registers before we start
> running the system, what happens if the user reads the PC/SP?
> What happens if they write it?

yes, bad things will happen

> (What happens in this case if you're doing JTAG debugging
> of real hardware?)

a professional debugger (like J-Link) does a great job trying to reset and halt 
the target as early as possible, i.e. at the reset vector, the values shown for 
the registers are correct, and changing them is legal and perfectly functional.


regards,

Liviu