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

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

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
+
 [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
-- 
2.7.4