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Re: [dsdp-dd-dev] Memory view and addressable size
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At 09:35 PM 6/20/2006, Daniel Jacobowitz wrote:
On Wed, Jun 21, 2006 at 11:19:24AM +0900, Anthony Berent wrote:
> The ability to control memory read, on some hardware, been
important for us.
> I too have come across examples where the value read depends on the read
> size, including cases where a registers is only readable at all
when read as
> a certain size. In addition to the obvious cases, where this is
specified as
> an obscure feature of the hardware there are two other cases I
can think of:
This has been on the books as a wanted-future-addition to GDB for ages;
pending someone with an active need for it to spec out the details.
However, the really interesting question to me is: does anyone know of
hardware where we would want a debugger to be able to perform reads of
more than one size on a particular address?
Otherwise, this can be handled completely without user interface, based
on a device memory map description.
So, yes, I'd initially thought a debugger backend could use the
target memory description to automatically "do the right thing", but
I've been told that in some architectures, reading a chunk of memory
with different access sizes intentionally produces different results.
For example, read 0x10000 as a byte, and the peripheral will give you
a set of status bits; read it as 16 bits, and it will provide you
data. I've been told this sort of thing is more typical in systems
with a constrained memory space. So, in this case, there is no right
and wrong way to access the memory; it really depends on what the
user is interested in seeing.
John
