spd: dispatcher for interacting with the Trusty TEE

This patch adds the secure payload dispatcher for interacting
with Google's Trusty TEE. Documentation for Trusty can be found
at https://source.android.com/security/trusty

Original authors:
-----------------
* Arve Hjønnevåg <arve@android.com>
* Michael Ryleev <gmar@google.com>

Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>
diff --git a/services/spd/trusty/trusty_helpers.S b/services/spd/trusty/trusty_helpers.S
new file mode 100644
index 0000000..9bbb044
--- /dev/null
+++ b/services/spd/trusty/trusty_helpers.S
@@ -0,0 +1,81 @@
+/*
+ * Copyright (c) 2016, ARM Limited and Contributors. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * Neither the name of ARM nor the names of its contributors may be used
+ * to endorse or promote products derived from this software without specific
+ * prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <asm_macros.S>
+
+.macro push ra, rb, sp=sp
+	stp \ra, \rb, [\sp,#-16]!
+.endm
+
+.macro pop ra, rb, sp=sp
+	ldp \ra, \rb, [\sp], #16
+.endm
+
+	.global trusty_context_switch_helper
+func trusty_context_switch_helper
+	push	x8, xzr
+	push	x19, x20
+	push	x21, x22
+	push	x23, x24
+	push	x25, x26
+	push	x27, x28
+	push	x29, x30
+
+	mov	x9, sp
+	ldr	x10, [x0]
+	mov	sp, x10
+	str	x9, [x0]
+
+	pop	x29, x30
+	pop	x27, x28
+	pop	x25, x26
+	pop	x23, x24
+	pop	x21, x22
+	pop	x19, x20
+	pop	x8, xzr
+	stp	x1, x2, [x8]
+	stp	x3, x4, [x8, #16]
+
+	ret
+endfunc trusty_context_switch_helper
+
+	.global trusty_init_context_stack
+func trusty_init_context_stack
+	push	x8, xzr, x1
+	push	xzr, xzr, x1
+	push	xzr, xzr, x1
+	push	xzr, xzr, x1
+	push	xzr, xzr, x1
+	push	xzr, xzr, x1
+	adr	x9, el3_exit
+	push	xzr, x9, x1
+	str	x1, [x0]
+	ret
+endfunc trusty_init_context_stack