Re: [Qemu-devel] Better Cortex-M support?

[Peter Maydell]

On 28 October 2014 14:37, Liviu Ionescu <address@hidden> wrote:
> On 28 Oct 2014, at 16:18, Peter Maydell <address@hidden> wrote:
>> Thanks. I've identified what's happening here, and
>> it's not a bug in QEMU as such. The 'lm3s6965evb'
>> model is of a microcontroller with 64KB of SRAM,
>> so valid RAM is only from 0x20000000 to 0x20010000,
>> but your binary is trying to use the area beyond that
>> as RAM as well, and is therefore misbehaving.

>> (We ignore any attempt to specify RAM size via the
>> command line -m switch, so your '-m 513M' has no effect).
>
> that explains it. my linker script assumes 1MB of flash and 1MB of RAM.
>
> what would be the recommended solution for a generic Cortex-M3 emulation, 
> make it back work with '-cpu cortex-m3' or do you mandate to use add a 
> generic '-machine cortex-m3'?

There's no such thing as a "generic Cortex-M3 emulation".
We model actual hardware (though in this case not a very
useful set of boards).

>> I suggest you relink your binary to fit in the 64K
>> of RAM this board has. (There's also flash at address
>> zero.)
>
> yeah, the flash issue is another item on my features list.
>
> the behaviour that I expect is to have the flash as a read only
> area, where gdb will be allowed to write in a similar way as when
> writing the physical flash (same as J-Link does).

I think writes via gdb will be treated in the same way as
writes by the CPU (ie interpreted as attempts to program
the flash device). QEMU doesn't support a "debug access"
abstraction.

-- PMM