ArmPkg: Add ArmHvcLib

This is a utility library closely modeled after ArmSmcLib, that allows
hypervisor call (HVC) instructions to be issued from C code.

Change-Id: I5f5c65f83e910ff98dbb2f5b031dad8c4f663daa
Contributed-under: TianoCore Contribution Agreement 1.0
Acked-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Olivier Martin <olivier.martin@arm.com>



git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16088 6f19259b-4bc3-4df7-8a09-765794883524

ArmPkg/Library/ArmHvcLib/AArch64/ArmHvc.S

@@ -0,0 +1,42 @@
+//
+//  Copyright (c) 2012-2014, ARM Limited. All rights reserved.
+//  Copyright (c) 2014, Linaro Limited. All rights reserved.
+//
+//  This program and the accompanying materials
+//  are licensed and made available under the terms and conditions of the BSD License
+//  which accompanies this distribution.  The full text of the license may be found at
+//  http://opensource.org/licenses/bsd-license.php
+//
+//  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+//
+//
+
+.text
+.align 3
+
+GCC_ASM_EXPORT(ArmCallHvc)
+
+ASM_PFX(ArmCallHvc):
+  // Push x0 on the stack
+  str   x0, [sp, #-8]!
+
+  // Load the HVC arguments values into the appropriate registers
+  ldp   x6, x7, [x0, #48]
+  ldp   x4, x5, [x0, #32]
+  ldp   x2, x3, [x0, #16]
+  ldp   x0, x1, [x0, #0]
+
+  hvc   #0
+
+  // Pop the ARM_HVC_ARGS structure address from the stack into x9
+  ldr   x9, [sp], #8
+
+  // Store the HVC returned values into the appropriate registers
+  // A HVC call can return up to 4 values
+  stp   x2, x3, [x9, #16]
+  stp   x0, x1, [x9, #0]
+
+  mov   x0, x9
+
+  ret