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

[Laszlo Ersek <lersek@redhat.com>]

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?

Thanks
Laszlo

>  [LibraryClasses.common]
>    ArmMmuLib|ArmPkg/Library/ArmMmuLib/ArmMmuBaseLib.inf
>  
> @@ -77,6 +80,11 @@ [BuildOptions]
>    GCC:*_*_ARM_PLATFORM_FLAGS == -mcpu=cortex-a15 -I$(WORKSPACE)/ArmVirtPkg/Include
>    *_*_AARCH64_PLATFORM_FLAGS == -I$(WORKSPACE)/ArmVirtPkg/Include
>  
> +[BuildOptions.ARM.EDKII.SEC, BuildOptions.ARM.EDKII.BASE]
> +  # Avoid MOVT/MOVW instruction pairs in code that may end up in the PIE
> +  # executable we build for the relocatable PrePi. They are not runtime
> +  # relocatable in ELF.
> +  *_CLANG35_*_CC_FLAGS = -mno-movt
>  
>  ################################################################################
>  #
> diff --git a/ArmVirtPkg/ArmVirtXen.dsc b/ArmVirtPkg/ArmVirtXen.dsc
> index 5ad1bf630bda..4ebead5ba6e6 100644
> --- a/ArmVirtPkg/ArmVirtXen.dsc
> +++ b/ArmVirtPkg/ArmVirtXen.dsc
> @@ -44,6 +44,9 @@ [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
> +
>  [LibraryClasses.common]
>    ArmMmuLib|ArmPkg/Library/ArmMmuLib/ArmMmuBaseLib.inf
>  
> @@ -77,6 +80,12 @@ [BuildOptions]
>    GCC:*_*_ARM_PLATFORM_FLAGS == -mcpu=cortex-a15 -I$(WORKSPACE)/ArmVirtPkg/Include
>    GCC:*_*_AARCH64_PLATFORM_FLAGS == -I$(WORKSPACE)/ArmVirtPkg/Include
>  
> +[BuildOptions.ARM.EDKII.SEC, BuildOptions.ARM.EDKII.BASE]
> +  # Avoid MOVT/MOVW instruction pairs in code that may end up in the PIE
> +  # executable we build for the relocatable PrePi. They are not runtime
> +  # relocatable in ELF.
> +  *_CLANG35_*_CC_FLAGS = -mno-movt
> +
>  ################################################################################
>  #
>  # Pcd Section - list of all EDK II PCD Entries defined by this Platform
>