[arch][arm64] add some helpful assembly macros for arm64

Pulled from Fuchsia Zircon kernel code.

arch/arm64/include/arch/asm_macros.h

@@ -1,13 +1,18 @@
 /*
  * Copyright (c) 2014 Travis Geiselbrecht
- *
+ * Copyright 2020 The Fuchsia Authors
  * Use of this source code is governed by a MIT-style
  * license that can be found in the LICENSE file or at
  * https://opensource.org/licenses/MIT
  */
 #pragma once
 
-/* *INDENT-OFF* */
+#ifdef __ASSEMBLER__ // clang-format off
+
+#ifndef __has_feature
+#define __has_feature(x) 0
+#endif
+
 .macro push ra, rb
 stp \ra, \rb, [sp,#-16]!
 .endm
@@ -16,6 +21,84 @@ stp \ra, \rb, [sp,#-16]!
 ldp \ra, \rb, [sp], #16
 .endm
 
+/// Fill a register with a wide integer literal.
+///
+/// This emits the one to four instructions required to fill a 64-bit
+/// register with a given bit pattern.  It uses as few instructions as
+/// suffice for the particular value.
+///
+/// Parameters
+///
+///   * reg
+///     - Required: Output 64-bit register.
+///
+///   * literal
+///     - Required: An integer expression that can be evaluated immediately
+///     without relocation.
+///
+.macro movlit reg, literal
+mov \reg, #((\literal) & 0xffff)
+.ifne (((\literal) >> 16) & 0xffff)
+movk \reg, #(((\literal) >> 16) & 0xffff), lsl #16
+.endif
+.ifne (((\literal) >> 32) & 0xffff)
+movk \reg, #(((\literal) >> 32) & 0xffff), lsl #32
+.endif
+.ifne (((\literal) >> 48) & 0xffff)
+movk \reg, #(((\literal) >> 48) & 0xffff), lsl #48
+.endif
+.endm  // movlit
+
+/// Materialize a symbol (with optional addend) into a register.
+///
+/// This emits the `adr` instruction or two-instruction sequence required
+/// to materialize the address of a global variable or function symbol.
+///
+/// Parameters
+///
+///   * reg
+///     - Required: Output 64-bit register.
+///
+///   * symbol
+///     - Required: A symbolic expression requiring at most PC-relative reloc.
+///
+.macro adr_global reg, symbol
+#if __has_feature(hwaddress_sanitizer)
+  adrp \reg, :pg_hi21_nc:\symbol
+  movk \reg, #:prel_g3:\symbol+0x100000000
+  add \reg, \reg, #:lo12:\symbol
+#elif defined(__AARCH64_CMODEL_TINY__)
+  adr \reg, \symbol
+#else
+  adrp \reg, \symbol
+  add \reg, \reg, #:lo12:\symbol
+#endif
+.endm  // adr_global
+
+/// Load a 64-bit fixed global symbol (with optional addend) into a register.
+///
+/// This emits the `ldr` instruction or two-instruction sequence required to
+/// load a global variable.  If multiple words are required, it's more
+/// efficient to use `adr_global` and then `ldp` than to repeat `ldr_global`
+/// with related locations.
+///
+/// Parameters
+///
+///   * reg
+///     - Required: Output 64-bit register.
+///
+///   * symbol
+///     - Required: A symbolic expression requiring at most PC-relative reloc.
+///
+.macro ldr_global reg, symbol
+#ifdef __AARCH64_CMODEL_TINY__
+  ldr \reg, \symbol
+#else
+  adrp \reg, \symbol
+  ldr \reg, [\reg, #:lo12:\symbol]
+#endif
+.endm  // adr_global
+
 .macro tbzmask, reg, mask, label, shift=0
 .if \shift >= 64
     .error "tbzmask: unsupported mask, \mask"
@@ -88,3 +171,5 @@ ldp \ra, \rb, [sp], #16
     .quad    \handler
 .popsection
 .endm
+
+#endif  // __ASSEMBLER__