[U-Boot] [PATCH v2 1/2] efi_loader: correctly call images

[Alexander Graf]

On 18.01.18 10:52, Heinrich Schuchardt wrote:
> 
> 
> On 01/18/2018 10:24 AM, Alexander Graf wrote:
>>
>>
>> On 18.01.18 08:24, Heinrich Schuchardt wrote:
>>> Avoid a failed assertion when an EFI app calls an EFI app.
>>>
>>> Avoid that the indent level increases when calling 'bootefi hello'
>>> repeatedly.
>>>
>>> Avoid negative indent level when an EFI app calls an EFI app that
>>> calls an EFI app (e.g. iPXE loads grub which starts the kernel).
>>>
>>> Return the status code of a loaded image that returns without
>>> calling the Exit boot service.
>>>
>>> Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
>>> ---
>>>   lib/efi_loader/efi_boottime.c | 21 ++++++++++++++-------
>>>   1 file changed, 14 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/lib/efi_loader/efi_boottime.c
>>> b/lib/efi_loader/efi_boottime.c
>>> index 2c5499e0c8..538cc55d20 100644
>>> --- a/lib/efi_loader/efi_boottime.c
>>> +++ b/lib/efi_loader/efi_boottime.c
>>> @@ -1537,6 +1537,7 @@ static efi_status_t EFIAPI
>>> efi_start_image(efi_handle_t image_handle,
>>>       asmlinkage ulong (*entry)(efi_handle_t image_handle,
>>>                     struct efi_system_table *st);
>>>       struct efi_loaded_image *info = image_handle;
>>> +    efi_status_t ret;
>>>         EFI_ENTRY("%p, %p, %p", image_handle, exit_data_size,
>>> exit_data);
>>>       entry = info->reserved;
>>> @@ -1546,17 +1547,23 @@ static efi_status_t EFIAPI
>>> efi_start_image(efi_handle_t image_handle,
>>>       /* call the image! */
>>>       if (setjmp(&info->exit_jmp)) {
>>>           /* We returned from the child image */
>>> +#ifdef CONFIG_ARM
>>> +        /* efi_exit() called efi_restore_gd() */
>>> +        gd = app_gd;
>>> +#endif
>>> +        /* Execute the return part of EFI_CALL */
>>> +        assert(__efi_entry_check());
>>> +        debug("%sEFI: %lu returned by started image\n",
>>> +              __efi_nesting_dec(),
>>
>> I don't understand why you need to decrease the nesting level here after
>> the other rework. You're now calling EFI_ENTRY/EFI_EXIT in all normal
>> paths when going in/out of an application, no?
> 
> bootefi -> level 0
> ** EFI application running at level 0
> LoadImage EFI_ENTRY -> level 1
> LoadImage EFI_EXIT -> level 0
> ** EFI application running at  level 0

-- base level at 0

> StartImage EFI_ENTRY -> level 1

This is decreased in EFI_EXIT of StartImage

> StartImage EFI_CALL -> level 2

This is the one that needs manual decrease then?

> Exit EFI_ENTRY -> level 3

Gets decreased right below in Exit again

> Exit EFI_EXIT -> level 2
> longjmp -> level 2
> __efi_nesting_dec() -> level 1
> StartImage EFI_EXIT -> level 0

--- base level again


So I guess the problem is that we never get into the second half of
EFI_CALL when ->exit() gets called because of the longjmp.

Can you please add a comment explaining that rationale with a hint to
EFI_CALL and that all we do is execute the lower half of it manually
again because it got interrupted by the longjmp?


Alex