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

[Alexander Graf]

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.


Alex