Phase 3 complete: managed assembler

task 3.5-3.6: x86 stdcall/thiscall/fastcall stubs (8 tests) task 3.7-3.8: x64 stub with RCX/RDX/R8/R9 register args + stack push (4 tests) task 3.9: no-FASM reference assertion test All passing (total: 87).
2026-07-21 19:52:04 +02:00
parent 98c53568d9
commit f39ecf820d
2 changed files with 162 additions and 180 deletions
@@ -110,9 +110,52 @@ public class StubAssembler : IAssembler
        buffer.Add(0xC3);                 // ret
    }

-    private static void BuildX64Stub(List<byte> buffer, ulong stubAddr,
+    private void BuildX64Stub(List<byte> buffer, ulong stubAddr,
        ulong target, uint[] args)
    {
-        throw new NotImplementedException("x64 stubs (task 3.7-3.8)");
+        ulong current = stubAddr;
+
+        // First 4 args go in RCX, RDX, R8D, R9D
+        var regCodes = new byte[] { 0xB9, 0xBA, 0xB8, 0xB9 }; // mov ecx/r8d/edx/r9d, imm32
+        var rexBytes = new byte[] { 0x00, 0x00, 0x41, 0x41 }; // 0x00 = no REX, 0x41 = REX.B
+
+        int regCount = Math.Min(args.Length, 4);
+        for (int i = 0; i < regCount; i++)
+        {
+            if (rexBytes[i] != 0)
+                buffer.Add(rexBytes[i]);
+            buffer.Add(regCodes[i]);
+            EmitU32(buffer, args[i]);
+            current += (rexBytes[i] != 0 ? 6u : 5u);
+        }
+
+        // Push remaining args in reverse order (right-to-left)
+        for (int i = args.Length - 1; i >= 4; i--)
+        {
+            buffer.Add(0x68); // push imm32
+            EmitU32(buffer, args[i]);
+            current += 5;
+        }
+
+        // call rel32
+        uint rel32 = (uint)(target - (current + 5));
+        buffer.Add(0xE8);
+        EmitU32(buffer, rel32);
+
+        // Caller cleanup: pop any args pushed on stack
+        int stackArgs = args.Length > 4 ? args.Length - 4 : 0;
+        if (stackArgs > 0)
+        {
+            int bytes = stackArgs * 8;
+            buffer.Add(0x48); // REX.W
+            buffer.Add(bytes <= 127 ? (byte)0x83 : (byte)0x81); // add r/m64, imm8/imm32
+            buffer.Add(0xC4); // rsp
+            if (bytes <= 127)
+                buffer.Add((byte)bytes);
+            else
+                EmitU32(buffer, (uint)bytes);
+        }
+
+        buffer.Add(0xC3); // ret
    }
 }