Re: [PATCH 2/2] ArmVirtPkg ARM: make relocatable PrePi users build with CLANG35

[Laszlo Ersek <lersek@redhat.com>]

On 08/03/16 12:02, Ard Biesheuvel wrote:
> On 3 August 2016 at 12:00, Laszlo Ersek <lersek@redhat.com> wrote:
>> On 08/03/16 10:21, Ard Biesheuvel wrote:
>>> The clang developers have made a backward incompatible change to the
>>> command line arguments, and have replaced '-mllvm -arm-use-movt=0'
>>> with '-mno-movt'. This does not matter for most ARM platforms, and
>>> therefore it has been removed from the default CLANG35/ARM CC flags
>>> in patch 1c63516075b3 ("BaseTools CLANG35: drop problematic use-movt
>>> and save-temps options"), but as it turns out, the relocatable PrePi
>>> implementation used by ArmVirtQemuKernel and ArmVirtXen will fail to
>>> build if it contains MOVT/MOVW pairs, due to the fact that these are
>>> not runtime relocatable under ELF.
>>>
>>> Since they are runtime relocatable under PE/COFF, and GenFw does the
>>> right thing when encountering them, selectively controlling their
>>> use is more appropriate than disabling them altogether. Therefore,
>>> this patch adds the -mno-movt argument only for the platforms that
>>> use the relocatable PrePi, and only for the module types that may
>>> be pulled into its build.
>>>
>>> Contributed-under: TianoCore Contribution Agreement 1.0
>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>>> ---
>>>  ArmVirtPkg/ArmVirtQemuKernel.dsc | 8 ++++++++
>>>  ArmVirtPkg/ArmVirtXen.dsc        | 9 +++++++++
>>>  2 files changed, 17 insertions(+)
>>>
>>> diff --git a/ArmVirtPkg/ArmVirtQemuKernel.dsc b/ArmVirtPkg/ArmVirtQemuKernel.dsc
>>> index 01a1d9b4613b..6c536d9bbd2d 100644
>>> --- a/ArmVirtPkg/ArmVirtQemuKernel.dsc
>>> +++ b/ArmVirtPkg/ArmVirtQemuKernel.dsc
>>> @@ -45,6 +45,9 @@ [LibraryClasses.ARM]
>>>    ArmLib|ArmPkg/Library/ArmLib/ArmV7/ArmV7Lib.inf
>>>    ArmCpuLib|ArmPkg/Drivers/ArmCpuLib/ArmCortexA15Lib/ArmCortexA15Lib.inf
>>>
>>> +[LibraryClasses.ARM.SEC]
>>> +  ArmLib|ArmPkg/Library/ArmLib/ArmV7/ArmV7LibSec.inf
>>> +
>>
>> How does this library resolution change relate to the stated purpose of
>> the patch?
>>
> 
> It prevents a version of ArmLib being pulled into the build of the
> relocatable PrePi that was built using the BuildOptions for DXE_DRIVER
> type modules.
> 

I think it would be reasonable to add this one paragraph to the commit
message as well. If you disagree, I won't insist. :)

Reviewed-by: Laszlo Ersek <lersek@redhat.com>