[PATCH 3/4] ArmPkg/ArmLib: AARCH64: allow the stack aligment (SA) bit to be managed

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

In preparation of enabling stack alignment checking, which is mandated
by the UEFI spec for AARCH64, add the code to manage this bit to ArmLib.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 ArmPkg/Include/Chipset/AArch64.h               | 12 +++++++
 ArmPkg/Library/ArmLib/AArch64/AArch64Support.S | 34 ++++++++++++++++++++
 2 files changed, 46 insertions(+)

diff --git a/ArmPkg/Include/Chipset/AArch64.h b/ArmPkg/Include/Chipset/AArch64.h
index 9aecb1df81e0..cebfc5da426a 100644
--- a/ArmPkg/Include/Chipset/AArch64.h
+++ b/ArmPkg/Include/Chipset/AArch64.h
@@ -194,6 +194,18 @@ ArmEnableAlignmentCheck (
 
 VOID
 EFIAPI
+ArmDisableStackAlignmentCheck (
+  VOID
+  );
+
+VOID
+EFIAPI
+ArmEnableStackAlignmentCheck (
+  VOID
+  );
+
+VOID
+EFIAPI
 ArmDisableAllExceptions (
   VOID
   );
diff --git a/ArmPkg/Library/ArmLib/AArch64/AArch64Support.S b/ArmPkg/Library/ArmLib/AArch64/AArch64Support.S
index c35c05fdf681..e53b5fdc5986 100644
--- a/ArmPkg/Library/ArmLib/AArch64/AArch64Support.S
+++ b/ArmPkg/Library/ArmLib/AArch64/AArch64Support.S
@@ -20,6 +20,7 @@
 .set CTRL_M_BIT,      (1 << 0)
 .set CTRL_A_BIT,      (1 << 1)
 .set CTRL_C_BIT,      (1 << 2)
+.set CTRL_SA_BIT,     (1 << 3)
 .set CTRL_I_BIT,      (1 << 12)
 .set CTRL_V_BIT,      (1 << 12)
 .set CPACR_VFP_BITS,  (3 << 20)
@@ -259,6 +260,39 @@ ASM_FUNC(ArmDisableAlignmentCheck)
    isb
    ret
 
+ASM_FUNC(ArmEnableStackAlignmentCheck)
+   EL1_OR_EL2(x1)
+1: mrs     x0, sctlr_el1        // Get control register EL1
+   b       3f
+2: mrs     x0, sctlr_el2        // Get control register EL2
+3: orr     x0, x0, #CTRL_SA_BIT // Set SA (stack alignment check) bit
+   EL1_OR_EL2(x1)
+1: msr     sctlr_el1, x0        // Write back control register
+   b       3f
+2: msr     sctlr_el2, x0        // Write back control register
+3: dsb     sy
+   isb
+   ret
+
+
+ASM_FUNC(ArmDisableStackAlignmentCheck)
+   EL1_OR_EL2_OR_EL3(x1)
+1: mrs     x0, sctlr_el1        // Get control register EL1
+   b       4f
+2: mrs     x0, sctlr_el2        // Get control register EL2
+   b       4f
+3: mrs     x0, sctlr_el3        // Get control register EL3
+4: bic     x0, x0, #CTRL_SA_BIT // Clear SA (stack alignment check) bit
+   EL1_OR_EL2_OR_EL3(x1)
+1: msr     sctlr_el1, x0        // Write back control register
+   b       4f
+2: msr     sctlr_el2, x0        // Write back control register
+   b       4f
+3: msr     sctlr_el3, x0        // Write back control register
+4: dsb     sy
+   isb
+   ret
+
 
 // Always turned on in AArch64. Else implementation specific. Leave in for C compatibility for now
 ASM_FUNC(ArmEnableBranchPrediction)
-- 
2.7.4