[U-Boot] [PATCH v9 12/18] sandbox: Enhance map_to_sysmem() to handle foreign pointers

[Alexander Graf]

On 08.08.18 11:54, Simon Glass wrote:
> At present map_sysmem() maps an address into the sandbox RAM buffer,
> return a pointer, while map_to_sysmem() goes the other way.
> 
> The mapping is currently just 1:1 since a case was not found where a more
> flexible mapping was needed. PCI does have a separate and more complex
> mapping, but uses its own mechanism.
> 
> However this arrange cannot handle one important case, which is where a
> test declares a stack variable and passes a pointer to it into a U-Boot
> function which uses map_to_sysmem() to turn it into a address. Since the
> pointer is not inside emulated DRAM, this will fail.
> 
> Add a mapping feature which can handle any such pointer, mapping it to a
> simple tag value which can be passed around in U-Boot as an address.
> 
> Signed-off-by: Simon Glass <sjg at chromium.org>

I think you are aware that this logic will fall apart spectacularly if
any arithmetic operation happens on the virtual (U-Boot) address, right?
So simple code like

  readl(vaddr + 1);

will just fail (hopefully) or (more likely) return a completely
incorrect value.

I assume this is intentional, but shouldn't the tag increment be
something slightly larger then?


Alex