[U-Boot] [PATCH 4/6] x86: efi: Add EFI loader support for x86

[Simon Glass]

Hi Alex,

On 25 October 2016 at 15:33, Alexander Graf <agraf at suse.de> wrote:
>
>
> On 10/08/2016 14:56, Simon Glass wrote:
>> Hi Alex,
>>
[...]

>>>>   #endif
>>>>     struct efi_device_path;
>>>> diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
>>>> index 798b566..e027bd3 100644
>>>> --- a/lib/efi_loader/efi_boottime.c
>>>> +++ b/lib/efi_loader/efi_boottime.c
>>>> @@ -39,6 +39,7 @@ static bool efi_is_direct_boot = true;
>>>>    */
>>>>   static struct efi_configuration_table EFI_RUNTIME_DATA
>>>> efi_conf_table[1];
>>>>   +#ifdef CONFIG_ARM
>>>>   /*
>>>>    * The "gd" pointer lives in a register on ARM and AArch64 that we
>>>> declare
>>>>    * fixed when compiling U-Boot. However, the payload does not know about
>>>> that
>>>> @@ -46,16 +47,20 @@ static struct efi_configuration_table EFI_RUNTIME_DATA
>>>> efi_conf_table[1];
>>>>    * EFI callback entry/exit.
>>>>    */
>>>>   static volatile void *efi_gd, *app_gd;
>>>> +#endif
>>>
>>>
>>> So is fs reserved for firmware use on x86?
>>
>> No I don't think so. The correct approach would be to save and restore
>> the FS register, but it seems to work this way, so I haven't taken it
>> any further.
>
> Can you make sure you save/restore %fs on x86 in the next round then?
> Finding bugs like these is very hard once the code is in.

I still haven't done this. In fact I'm starting to wonder what other
registers we might have a problem with. Looking at the
setjmp()/longjmp() that I have, it doesn't save everything.

>
>> This series was just an attempt to get the EFI loader working on x86.
>
> Yes, and it's very very very much appreciated :).
>
>> Since we have the 32/64-bit limitation on x86 and U-Boot runs in
>> 32-bit at present, it's not going to be very useful yet IMO. But it is
>> a start.
>
> I agree. It's a really good start.

I suspect that it will be quite a bit of work to get U-Boot running in
64-bit mode. I sent a series about a month ago, but it still lacks
quite a few features.

Regards,
Simon