[U-Boot] [PATCH v8 22/30] efi: sandbox: Tidy up copy_fdt() to work with sandbox

[Simon Glass]

Hi Alex,

On 21 June 2018 at 04:13, Alexander Graf <agraf at suse.de> wrote:
> On 06/21/2018 04:01 AM, Simon Glass wrote:
>>
>> Hi Alex,
>>
>> On 18 June 2018 at 09:00, Alexander Graf <agraf at suse.de> wrote:
>>>
>>> On 06/18/2018 04:08 PM, Simon Glass wrote:
>>>>
>>>> At present this function takes a pointer as its argument, then passes
>>>> this
>>>> to efi_allocate_pages(), which actually takes an address. It uses casts,
>>>> which are not supported on sandbox.
>>>
>>>
>>> I think this is the big API misunderstanding that caused our
>>> disagreements:
>>> efi_allocate_pages(uint64_t *memory) gets a uint64_t *address as input
>>> parameter, but uses the same field to actually return a void * pointer.
>>> This
>>> is the function that really converts between virtual and physical address
>>> space.
>>>
>>> This is the explicit wording of the spec[1] page 168:
>>>
>>>    The AllocatePages() function allocates the requested number of pages
>>> and
>>> returns a pointer to the base address of the page range in the location
>>> referenced by Memory.
>>
>> The code at present uses *Memory as the address on both input and
>> output. The spec is confusing, but I suspect that is what it meant.
>
>
> The spec means *Memory on IN is an address, on OUT is a pointer. It's quite
> clear on that. Since the functions is available to payloads, we should
> follow that semantic.
>
>>> So yes, we have to cast. There is no other way around it without
>>> completely
>>> creating a trainwreck of the API.
>>
>> efi_allocate_pages_ext() can do this though. We don't need to copy the
>> API to efi_allocate_pages().
>
>
> Yikes. There's no way we'll create a frankenstein not-really-almost EFI API
> inside U-Boot. Either we stick to the standard or we don't.

The API is the _ext() function, right? We can rename the internal
function if you like.

In any case I think you have this confused. From the spec:

     "Pointer to a physical address. On input, the way in which the
address is used depends on the value of Type. See “Description” for
more information. On output the address is set to the base of the page
range that was allocated. See “Related Definitions.”"

The parameter does not turn into a pointer on exit. It is an address,
just as it is on input. What am I missing?

Regards,
Simon