implement detour_transaction_begin

arm64/detours_arm64.h

@@ -0,0 +1,53 @@
+// Copyright (c) Microsoft Corporation.  All rights reserved.
+// Copyright (c) Lysann Tranvouez.  All rights reserved.
+
+#pragma once
+#ifndef MACH_DETOURS_ARM64_H
+#define MACH_DETOURS_ARM64_H
+
+typedef struct detour_align
+{
+    uint8_t    obTarget;
+    uint8_t    obTrampoline;
+} detour_align;
+
+typedef struct detour_trampoline
+{
+    // An ARM64 instruction is 4 bytes long.
+    //
+    // The overwrite is always composed of 3 instructions (12 bytes) which perform an indirect jump
+    // using _DETOUR_TRAMPOLINE::pbDetour as the address holding the target location.
+    //
+    // Copied instructions can expand.
+    //
+    // The scheme using MovImmediate can cause an instruction
+    // to grow as much as 6 times.
+    // That would be Bcc or Tbz with a large address space:
+    //   4 instructions to form immediate
+    //   inverted tbz/bcc
+    //   br
+    //
+    // An expansion of 4 is not uncommon -- bl/blr and small address space:
+    //   3 instructions to form immediate
+    //   br or brl
+    //
+    // A theoretical maximum for rbCode is thefore 4*4*6 + 16 = 112 (another 16 for jmp to pbRemain).
+    //
+    // With literals, the maximum expansion is 5, including the literals: 4*4*5 + 16 = 96.
+    //
+    // The number is rounded up to 128. m_rbScratchDst should match this.
+    //
+    uint8_t            rbCode[128];    // target code + jmp to pbRemain
+    uint8_t            cbCode;         // size of moved target code.
+    uint8_t            cbCodeBreak[3]; // padding to make debugging easier.
+    uint8_t            rbRestore[24];  // original target code.
+    uint8_t            cbRestore;      // size of original target code.
+    uint8_t            cbRestoreBreak[3]; // padding to make debugging easier.
+    detour_align   rAlign[8];      // instruction alignment array.
+    uint8_t*          pbRemain;       // first instruction after moved code. [free list]
+    uint8_t*          pbDetour;       // first instruction of detour function.
+} detour_trampoline;
+
+static_assert(sizeof(detour_trampoline) == 192);
+
+#endif //MACH_DETOURS_ARM64_H