ArmPkg/Library/ArmLib: add ArmWriteSctlr

This currently isn't needed by anything in the edk2 tree but
it's useful for externally maintained platforms which have
to set this register e.g. to disable alignment aborts.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Michael Zimmermann <sigmaepsilon92@gmail.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

ArmPkg/Include/Library/ArmLib.h

@@ -558,6 +558,12 @@ ArmReadSctlr (
   VOID
   );
 
+VOID
+EFIAPI
+ArmWriteSctlr (
+  IN  UINT32   Value
+  );
+
 UINTN
 EFIAPI
 ArmReadHVBar (

ArmPkg/Library/ArmLib/AArch64/ArmLibSupport.S

@@ -187,4 +187,13 @@ ASM_FUNC(ArmReadSctlr)
 3:mrs   x0, sctlr_el3
 4:ret
 
+ASM_FUNC(ArmWriteSctlr)
+  EL1_OR_EL2_OR_EL3(x1)
+1:msr   sctlr_el1, x0
+  ret
+2:msr   sctlr_el2, x0
+  ret
+3:msr   sctlr_el3, x0
+4:ret
+
 ASM_FUNCTION_REMOVE_IF_UNREFERENCED

ArmPkg/Library/ArmLib/Arm/ArmLibSupport.S

@@ -153,6 +153,10 @@ ASM_FUNC(ArmReadSctlr)
   mrc     p15, 0, r0, c1, c0, 0      @ Read SCTLR into R0 (Read control register configuration data)
   bx      lr
 
+ASM_FUNC(ArmWriteSctlr)
+  mcr     p15, 0, r0, c1, c0, 0
+  bx      lr
+
 ASM_FUNC(ArmReadCpuActlr)
   mrc     p15, 0, r0, c1, c0, 1
   bx      lr

ArmPkg/Library/ArmLib/Arm/ArmLibSupport.asm

@@ -155,6 +155,9 @@
   mrc     p15, 0, r0, c1, c0, 0      // Read SCTLR into R0 (Read control register configuration data)
   bx      lr
 
+ RVCT_ASM_EXPORT ArmWriteSctlr
+  mcr     p15, 0, r0, c1, c0, 0
+  bx      lr
 
  RVCT_ASM_EXPORT ArmReadCpuActlr
   mrc     p15, 0, r0, c1, c0, 1