diff --git a/WhiteMagic/Assembly/StubAssembler.cs b/WhiteMagic/Assembly/StubAssembler.cs
index d9bc236..e470d19 100644
--- a/WhiteMagic/Assembly/StubAssembler.cs
+++ b/WhiteMagic/Assembly/StubAssembler.cs
@@ -46,21 +46,35 @@ public sealed class StubAssembler : IAssembler
///
/// Where the stub lands (for E8 rel32 encoding).
/// Function to call.
- /// Argument values (uint[] — each 4 or 8 bytes per pointerSize).
+ /// Argument values. For x86 each element holds a 32-bit argument;
+ /// for x64 each element holds the full 64-bit pointer-sized argument.
/// 4 (x86) or 8 (x64).
- /// Calling convention.
+ /// Calling convention (ignored on x64; Windows has a single ABI).
/// is not 4 or 8,
/// or is not known, or the distance between stub and target
/// exceeds the E8 rel32 range.
public byte[] BuildCallStub(IntPtr stubAddress, IntPtr targetAddress,
- uint[] arguments, int pointerSize, CallConvention convention)
+ nuint[] arguments, int pointerSize, CallConvention convention)
{
- var buffer = new List(64);
+ var buffer = new List(96);
if (pointerSize == 4)
{
+ // X86 args are 32-bit. Truncate nuint down to uint — callers must pass values
+ // that fit in 32 bits on x86 targets.
+ uint[] args32 = new uint[arguments.Length];
+ for (int i = 0; i < arguments.Length; i++)
+ {
+ ulong v = arguments[i];
+ if (v > uint.MaxValue)
+ {
+ throw new ArgumentOutOfRangeException(nameof(arguments),
+ $"Argument {i} = 0x{v:X} does not fit in 32 bits (x86 target).");
+ }
+ args32[i] = (uint)v;
+ }
BuildX86Stub(buffer, checked((uint)stubAddress), checked((uint)targetAddress),
- arguments, convention);
+ args32, convention);
}
else if (pointerSize == 8)
{
@@ -153,57 +167,113 @@ public sealed class StubAssembler : IAssembler
buffer.Add(0xC3); // ret
}
+ ///
+ /// Builds a Windows x64 call stub that conforms to the Microsoft x64 ABI:
+ /// first 4 integer/pointer args in RCX, RDX, R8, R9 (64-bit loads); stack args
+ /// above 32-byte shadow space; 16-byte stack alignment at the call instruction.
+ ///
+ ///
+ /// The stub frame:
+ ///
+ /// sub rsp, 0x20 ; 32-byte shadow space + restores 16-byte alignment
+ /// mov rcx, arg0 ; 64-bit loads (REX.W mov r64, imm64)
+ /// mov rdx, arg1
+ /// mov r8, arg2
+ /// mov r9, arg3
+ /// mov rax, arg[N]
+ /// mov [rsp + 0x20 + 8*(N-4)], rax ; stack args placed above the shadow slots
+ /// ...
+ /// call target (rel32)
+ /// add rsp, 0x20
+ /// ret
+ ///
+ /// On entry the stub sees rsp ≡ 8 (mod 16) (the caller's call pushed
+ /// the return address). sub rsp, 0x20 moves rsp to ≡ 0 (mod 16). Just before
+ /// the inner call, rsp is still ≡ 0, so target's entry rsp is
+ /// ≡ 8 (mod 16) — no, wait: entry ≡ 0 after sub; call target pushes 8, so
+ /// target's entry is ≡ 0 − 8 ≡ 8; but we want target entry ≡ 0. Re-check:
+ /// Stub entry: rsp ≡ 8 (mod 16). After sub rsp, 0x20:
+ /// 8 − 0x20 = −24 ≡ 8 (mod 16). After the inner call, target entry is
+ /// 8 − 8 ≡ 0 (mod 16). Target is 16-byte aligned — SSE safe.
+ ///
private void BuildX64Stub(List buffer, ulong stubAddr,
- ulong target, uint[] args)
+ ulong target, nuint[] args)
{
- // Windows x64 single ABI: first 4 args in RCX, RDX, R8D, R9D.
ulong current = stubAddr;
- var regCodes = new byte[] { 0xB9, 0xBA, 0xB8, 0xB9 };
- var rexBytes = new byte[] { 0x00, 0x00, 0x41, 0x41 };
+ // 1. Allocate shadow space.
+ // sub rsp, 0x20 ; 32 bytes = 4 shadow slots AND (entry − 0x20) ≡ 8 (mod 16),
+ // so rsp after the sub ≡ 8 (mod 16); `call target` will push 8 and land target
+ // at ≡ 0 (mod 16).
+ buffer.Add(0x48); buffer.Add(0x81); buffer.Add(0xEC); // sub rsp, imm32
+ EmitU32(buffer, 0x20);
+ current += 7;
+
+ // 2. 64-bit register loads.
+ // RCX = REX.W 0xB9 + imm64 (10 bytes)
+ // RDX = REX.W 0xBA + imm64 (10 bytes)
+ // R8 = REX.WB 0xB8 + imm64 (11 bytes, REX.W|R = 0x49)
+ // R9 = REX.WB 0xB9 + imm64 (11 bytes)
+ byte[][] regMoves =
+ [
+ [0x48, 0xB9], // mov rcx, imm64
+ [0x48, 0xBA], // mov rdx, imm64
+ [0x49, 0xB8], // mov r8, imm64
+ [0x49, 0xB9], // mov r9, imm64
+ ];
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);
+ byte[] prefix = regMoves[i];
+ buffer.Add(prefix[0]);
+ buffer.Add(prefix[1]);
+ EmitU64(buffer, args[i]);
+ current += (uint)(prefix.Length + 8);
}
- // Push remaining args in reverse order
- for (int i = args.Length - 1; i >= 4; i--)
+ // 3. Stack args (args 4+): placed at [rsp + 0x20 + 8*(i-4)].
+ // Each is two instructions:
+ // mov rax, imm64 (10 bytes)
+ // mov [rsp + disp], rax (5..8 bytes depending on disp8/disp32)
+ for (int i = 4; i < args.Length; i++)
{
- current += 5;
- buffer.Add(0x68);
- EmitU32(buffer, args[i]);
+ int offset = 0x20 + (i - 4) * 8;
+ buffer.Add(0x48); buffer.Add(0xB8); // mov rax, imm64
+ EmitU64(buffer, args[i]);
+ current += 10;
+
+ buffer.Add(0x48); buffer.Add(0x89); // mov [rsp + disp], rax
+ if (offset <= 127)
+ {
+ buffer.Add(0x44); buffer.Add(0x24); // ModRM: [rsp + disp8]
+ buffer.Add((byte)offset);
+ current += 5;
+ }
+ else
+ {
+ buffer.Add(0x84); buffer.Add(0x24); // ModRM: [rsp + disp32]
+ EmitU32(buffer, (uint)offset);
+ current += 8;
+ }
}
- // call rel32
+ // 4. call rel32
long distance = (long)target - (long)(current + 5);
- if (distance < int.MinValue || distance > int.MaxValue)
+ if (distance is < int.MinValue or > int.MaxValue)
{
throw new ArgumentOutOfRangeException(
"target and stub are >2 GiB apart; E8 rel32 cannot encode this distance.");
}
buffer.Add(0xE8);
EmitU32(buffer, (uint)distance);
+ current += 5;
- // Pop any args pushed on stack (x64 is caller-clean)
- 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);
- }
+ // 5. add rsp, 0x20 ; tear down shadow space
+ buffer.Add(0x48); buffer.Add(0x81); buffer.Add(0xC4);
+ EmitU32(buffer, 0x20);
+ // 6. ret
buffer.Add(0xC3);
}
diff --git a/WhiteMagic/ExternalReader.cs b/WhiteMagic/ExternalReader.cs
index 62d2979..15a3834 100644
--- a/WhiteMagic/ExternalReader.cs
+++ b/WhiteMagic/ExternalReader.cs
@@ -42,7 +42,8 @@ public sealed class ExternalReader : MemoryBase
}
// Process.MainModule throws Win32Exception for a bitness-mismatched or protected
- // target; a missing image base must not sink the whole reader.
+ // target. A missing image base must not sink the whole reader — callers can still
+ // use absolute addresses when ImageBase is unknown.
try
{
_imageBase = process.MainModule?.BaseAddress ?? IntPtr.Zero;
@@ -65,18 +66,7 @@ public sealed class ExternalReader : MemoryBase
if (isRelative)
address = GetAbsolute(address);
- byte[] buffer = new byte[count];
- if (!NativeMethods.ReadProcessMemory(_handle, address, buffer, count, out nint bytesRead))
- {
- return [];
- }
-
- if ((int)bytesRead != count)
- {
- Array.Resize(ref buffer, (int)bytesRead);
- }
-
- return buffer;
+ return RpmHelper.ReadBytes(_handle, address, count);
}
///
@@ -85,12 +75,7 @@ public sealed class ExternalReader : MemoryBase
if (isRelative)
address = GetAbsolute(address);
- if (!NativeMethods.WriteProcessMemory(_handle, address, bytes, bytes.Length, out nint written))
- {
- return 0;
- }
-
- return (int)written;
+ return RpmHelper.WriteBytes(_handle, address, bytes);
}
///
diff --git a/WhiteMagic/InProcessReader.cs b/WhiteMagic/InProcessReader.cs
index 2e2f947..5079636 100644
--- a/WhiteMagic/InProcessReader.cs
+++ b/WhiteMagic/InProcessReader.cs
@@ -12,6 +12,13 @@ namespace WhiteMagic;
/// empty / zero bytes) on invalid or protected addresses instead of crashing
/// the host process with an .
///
+///
+/// This is functionally equivalent to opened on the current
+/// process. It exists as a distinct type because the design (see
+/// openspec/changes/whitemagic-foundation/design.md D1) treats "injected in-process"
+/// as a separate mode from "external". The two modes will diverge further once the
+/// InProcessInvoker delegate-call path lands.
+///
public sealed class InProcessReader : MemoryBase
{
private readonly SafeMemoryHandle _handle;
@@ -35,7 +42,16 @@ public sealed class InProcessReader : MemoryBase
$"OpenProcess failed for PID {current.Id}: error {error}");
}
- _imageBase = current.MainModule?.BaseAddress ?? IntPtr.Zero;
+ // Process.MainModule rarely throws on the current process, but guard it
+ // nonetheless for parity with ExternalReader.
+ try
+ {
+ _imageBase = current.MainModule?.BaseAddress ?? IntPtr.Zero;
+ }
+ catch (System.ComponentModel.Win32Exception)
+ {
+ _imageBase = IntPtr.Zero;
+ }
}
///
@@ -50,18 +66,7 @@ public sealed class InProcessReader : MemoryBase
if (isRelative)
address = GetAbsolute(address);
- byte[] buffer = new byte[count];
- if (!NativeMethods.ReadProcessMemory(_handle, address, buffer, count, out nint bytesRead))
- {
- return [];
- }
-
- if ((int)bytesRead != count)
- {
- Array.Resize(ref buffer, (int)bytesRead);
- }
-
- return buffer;
+ return RpmHelper.ReadBytes(_handle, address, count);
}
///
@@ -70,12 +75,7 @@ public sealed class InProcessReader : MemoryBase
if (isRelative)
address = GetAbsolute(address);
- if (!NativeMethods.WriteProcessMemory(_handle, address, bytes, bytes.Length, out nint written))
- {
- return 0;
- }
-
- return (int)written;
+ return RpmHelper.WriteBytes(_handle, address, bytes);
}
///
diff --git a/WhiteMagic/MarshalCache.cs b/WhiteMagic/MarshalCache.cs
index 49f1b59..bccbc6f 100644
--- a/WhiteMagic/MarshalCache.cs
+++ b/WhiteMagic/MarshalCache.cs
@@ -1,88 +1,77 @@
using System.Reflection;
+using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
namespace WhiteMagic;
///
-/// Computes and caches marshal-related metadata for type
-/// exactly once. and
-/// branch on these cached flags to decide between blittable Span/MemoryMarshal
-/// paths and the fallback marshal path.
+/// Computes and caches the byte size and marshalling decision for type
+/// exactly once. and
+/// branch on
+/// to decide between the blittable Span /
+/// path and the
+/// path.
///
/// The type to cache metadata for.
public static class MarshalCache
{
- /// The unmanaged size of in bytes.
+ ///
+ /// The byte size of . For the blittable path this is
+ /// the managed layout size — the width that
+ /// /
+ /// actually consume. For primitive-sized types (, ,
+ /// and the underlying of enums) the size matches the CLR primitive width.
+ ///
public static readonly int Size;
- /// The unmanaged size of as an unsigned integer.
- public static readonly uint SizeU;
-
///
- /// when cannot be copied through the
- /// blittable path and must
- /// use / instead.
- /// This is the case when a top-level field carries , or
- /// when contains a managed reference
- /// ().
+ /// when cannot be copied through
+ /// the blittable path
+ /// and must fall back to /
+ /// . This is the case when a top-level field
+ /// carries , or when
+ /// contains a managed reference
+ /// ().
///
///
/// The check inspects only top-level fields; a
/// on a field of a nested struct is not detected.
- /// Reference-containing nested structs are still caught, because the reference check
- /// propagates through nested value types.
+ /// Reference-containing nested structs are still caught, because the reference
+ /// check propagates through nested value types.
///
public static readonly bool TypeRequiresMarshal;
- /// when is .
- public static readonly bool IsIntPtr;
-
- /// The underlying type code of .
- public static readonly TypeCode TypeCode;
-
- ///
- /// The effective type that the marshaler uses. For an enum this is the underlying
- /// integer type; for all other types it is itself.
- ///
- public static readonly Type RealType;
-
static MarshalCache()
{
- TypeCode = Type.GetTypeCode(typeof(T));
-
if (typeof(T) == typeof(bool))
{
Size = 1;
- RealType = typeof(T);
}
else if (typeof(T) == typeof(char))
{
- // Marshal.SizeOf(char) is 1 (ANSI), but the blittable path reads/writes a
- // char as a 2-byte UTF-16 code unit. Size must match the blittable width.
+ // Marshal.SizeOf reports 1 (ANSI char), but the blittable
+ // MemoryMarshal path reads/writes a char as a 2-byte UTF-16 code unit.
+ // Use the managed layout width so Size matches what the reader actually uses.
Size = 2;
- RealType = typeof(T);
}
else if (typeof(T).IsEnum)
{
- Type underlying = typeof(T).GetEnumUnderlyingType();
- Size = Marshal.SizeOf(underlying);
- RealType = underlying;
- TypeCode = Type.GetTypeCode(underlying);
+ Size = Marshal.SizeOf(typeof(T).GetEnumUnderlyingType());
}
else
{
- Size = Marshal.SizeOf(typeof(T));
- RealType = typeof(T);
+ // The blittable path goes through MemoryMarshal, which uses the CLR managed
+ // layout. Use Unsafe.SizeOf so Size agrees with that layout —
+ // Marshal.SizeOf can disagree when a struct contains a `bool` field
+ // (unmanaged width 4 vs managed width 1).
+ Size = Unsafe.SizeOf();
}
- SizeU = (uint)Size;
- IsIntPtr = RealType == typeof(IntPtr);
-
bool hasMarshalAsField =
- RealType.GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic)
+ typeof(T).GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic)
.Any(f => f.GetCustomAttributes(typeof(MarshalAsAttribute), true).Length != 0);
TypeRequiresMarshal =
- hasMarshalAsField || System.Runtime.CompilerServices.RuntimeHelpers.IsReferenceOrContainsReferences();
+ hasMarshalAsField || RuntimeHelpers.IsReferenceOrContainsReferences();
}
}
diff --git a/WhiteMagicTest/InProcessReaderTests.cs b/WhiteMagicTest/InProcessReaderTests.cs
index 776b5aa..6dd05a6 100644
--- a/WhiteMagicTest/InProcessReaderTests.cs
+++ b/WhiteMagicTest/InProcessReaderTests.cs
@@ -4,9 +4,11 @@ using WhiteMagic;
namespace WhiteMagicTest;
///
-/// Tests for — direct pointer dereference against
-/// the own process. Verifies the shared API works for
-/// both external and in-process readers.
+/// Tests for . The current implementation uses
+/// ReadProcessMemory/WriteProcessMemory on a self-handle (per the D1
+/// revision — unsafe direct-pointer dereference was rejected because .NET cannot
+/// catch ). Verifies the shared
+/// API works for both external and in-process readers.
///
public class InProcessReaderTests
{
diff --git a/WhiteMagicTest/MarshalCacheTests.cs b/WhiteMagicTest/MarshalCacheTests.cs
index 6511eac..263555a 100644
--- a/WhiteMagicTest/MarshalCacheTests.cs
+++ b/WhiteMagicTest/MarshalCacheTests.cs
@@ -1,3 +1,4 @@
+using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using WhiteMagic;
@@ -5,7 +6,7 @@ namespace WhiteMagicTest;
///
/// Tests for : blittable size, marshal-required flag,
-/// IsIntPtr, and computed-once behavior.
+/// and computed-once behavior.
///
public class MarshalCacheTests
{
@@ -45,12 +46,33 @@ public class MarshalCacheTests
Assert.Equal(8, MarshalCache.Size);
}
+ [Fact]
+ public void Size_for_struct_with_bool_is_managed_layout_width()
+ {
+ // Regression for the Marshal.SizeOf / Unsafe.SizeOf disagreement on a struct
+ // whose only field is `bool`: Marshal reports 4 bytes (Win32 BOOL default marshaling),
+ // but the blittable path (MemoryMarshal.Read) actually lays out a bool as 1 byte.
+ // MarshalCache.Size must match what the reader actually touches.
+ Assert.Equal(Unsafe.SizeOf(), MarshalCache.Size);
+ Assert.Equal(1, MarshalCache.Size);
+ }
+
+ [Fact]
+ public void Size_for_struct_with_bools_in_sequence_matches_managed_layout()
+ {
+ // Sequential struct { bool, bool } — managed width is 2, Marshal width is 8 (two BOOLs).
+ // The blittable path uses 1 byte per bool, so Size must equal the managed width.
+ Assert.Equal(Unsafe.SizeOf(), MarshalCache.Size);
+ Assert.Equal(2, MarshalCache.Size);
+ }
+
[Fact]
public void TypeRequiresMarshal_is_false_for_blittable_types()
{
Assert.False(MarshalCache.TypeRequiresMarshal);
- Assert.False(MarshalCache.TypeRequiresMarshal);
- Assert.False(MarshalCache.TypeRequiresMarshal);
+ Assert.False(MarshalCache.TypeRequiresMarshal);
+ Assert.False(MarshalCache.TypeRequiresMarshal);
+ Assert.False(MarshalCache.TypeRequiresMarshal);
}
[Fact]
@@ -60,39 +82,23 @@ public class MarshalCacheTests
}
[Fact]
- public void IsIntPtr_is_true_for_IntPtr()
+ public void TypeRequiresMarshal_is_true_for_reference_containing_types()
{
- Assert.True(MarshalCache.IsIntPtr);
+ Assert.True(MarshalCache.TypeRequiresMarshal);
+ Assert.True(MarshalCache.TypeRequiresMarshal);
}
[Fact]
- public void IsIntPtr_is_false_for_non_IntPtr_types()
- {
- Assert.False(MarshalCache.IsIntPtr);
- Assert.False(MarshalCache.IsIntPtr);
- Assert.False(MarshalCache.IsIntPtr);
- }
-
- [Fact]
- public void All_properties_are_computed_once_and_cached()
+ public void Properties_are_computed_once_and_cached()
{
int size1 = MarshalCache.Size;
bool marshal1 = MarshalCache.TypeRequiresMarshal;
- bool intPtr1 = MarshalCache.IsIntPtr;
int size2 = MarshalCache.Size;
bool marshal2 = MarshalCache.TypeRequiresMarshal;
- bool intPtr2 = MarshalCache.IsIntPtr;
Assert.Equal(size1, size2);
Assert.Equal(marshal1, marshal2);
- Assert.Equal(intPtr1, intPtr2);
- }
-
- [Fact]
- public void SizeU_matches_Size_as_uint()
- {
- Assert.Equal((uint)MarshalCache.Size, MarshalCache.SizeU);
}
[StructLayout(LayoutKind.Sequential)]
@@ -108,4 +114,22 @@ public class MarshalCacheTests
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 16)]
public byte[] Data;
}
+
+ [StructLayout(LayoutKind.Sequential)]
+ private struct SingleBoolStruct
+ {
+ public bool Flag;
+ }
+
+ [StructLayout(LayoutKind.Sequential)]
+ private struct SequentialBoolStruct
+ {
+ public bool A;
+ public bool B;
+ }
+
+ private class ClassWithInt
+ {
+ public int Value = 0;
+ }
}
diff --git a/WhiteMagicTest/Native/NativeSurfaceTests.cs b/WhiteMagicTest/Native/NativeSurfaceTests.cs
index 786b48e..bb8e3dd 100644
--- a/WhiteMagicTest/Native/NativeSurfaceTests.cs
+++ b/WhiteMagicTest/Native/NativeSurfaceTests.cs
@@ -57,13 +57,13 @@ public class NativeSurfaceTests
{
using SafeMemoryHandle handle = OpenSelf(
ProcessAccess.VmWrite | ProcessAccess.VmOperation | ProcessAccess.QueryInformation);
- ReadOnlySpan payload = BitConverter.GetBytes(0x5EED);
+ ReadOnlySpan bytes = BitConverter.GetBytes(0x5EED);
bool ok = NativeMethods.WriteProcessMemory(
- handle, pin.AddrOfPinnedObject(), payload, payload.Length, out nint written);
+ handle, pin.AddrOfPinnedObject(), bytes, bytes.Length, out nint written);
Assert.True(ok, $"WriteProcessMemory failed: {Marshal.GetLastPInvokeError()}");
- Assert.Equal(payload.Length, (int)written);
+ Assert.Equal(bytes.Length, (int)written);
Assert.Equal(0x5EED, Marshal.ReadInt32(pin.AddrOfPinnedObject()));
}
finally
diff --git a/WhiteMagicTest/StubAssemblerTests.cs b/WhiteMagicTest/StubAssemblerTests.cs
index acfb6a4..242ec4c 100644
--- a/WhiteMagicTest/StubAssemblerTests.cs
+++ b/WhiteMagicTest/StubAssemblerTests.cs
@@ -90,7 +90,7 @@ public class StubAssemblerTests
{
uint ca=0x10000000u+5,r=0x12345678u-(ca+5);
byte[] s=Create().BuildCallStub((IntPtr)0x10000000,(IntPtr)0x12345678,[0xCAFEBABE],4,CallConvention.Thiscall);
- Assert.Equal(11,s.Length); Assert.Equal(0xB9,s[0]); Assert.Equal(0xCAFEBABE,BitConverter.ToUInt32(s,1));
+ Assert.Equal(11,s.Length); Assert.Equal(0xB9,s[0]); Assert.Equal(0xCAFEBABEu,BitConverter.ToUInt32(s,1));
Assert.Equal(0xE8,s[5]); Assert.Equal(r,BitConverter.ToUInt32(s,6)); Assert.Equal(0xC3,s[10]);
}
@@ -120,8 +120,8 @@ public class StubAssemblerTests
{
uint ca=0x10000000u+10,r=0x12345678u-(ca+5);
byte[] s=Create().BuildCallStub((IntPtr)0x10000000,(IntPtr)0x12345678,[0xAAAAAAAA,0xBBBBBBBB],4,CallConvention.Fastcall);
- Assert.Equal(16,s.Length); Assert.Equal(0xB9,s[0]); Assert.Equal(0xAAAAAAAA,BitConverter.ToUInt32(s,1));
- Assert.Equal(0xBA,s[5]); Assert.Equal(0xBBBBBBBB,BitConverter.ToUInt32(s,6));
+ Assert.Equal(16,s.Length); Assert.Equal(0xB9,s[0]); Assert.Equal(0xAAAAAAAAu,BitConverter.ToUInt32(s,1));
+ Assert.Equal(0xBA,s[5]); Assert.Equal(0xBBBBBBBBu,BitConverter.ToUInt32(s,6));
Assert.Equal(0xE8,s[10]); Assert.Equal(r,BitConverter.ToUInt32(s,11)); Assert.Equal(0xC3,s[15]);
}
@@ -133,52 +133,207 @@ public class StubAssemblerTests
Create().BuildCallStub((IntPtr)0x10000000,(IntPtr)0x12345678,[],4,CallConvention.Fastcall));
}
- // ── x64 ─────────────────────────────────────────────────────────────
+ // ── x64 (Microsoft x64 ABI — shadow space + 16-byte alignment + 64-bit loads) ──
+ //
+ // Stub frame layout:
+ // bytes 0..6 sub rsp, 0x20 (7 bytes — shadow space + realignment)
+ // bytes 7..N mov r64, imm64 ... (10 bytes per reg move: 2-byte prefix + 8-byte imm)
+ // mov rax, imm64 / mov [rsp+0x20+8*(i-4)], rax for stack args (15 bytes each)
+ // E8 rel32 call target (5 bytes)
+ // 48 81 C4 20 00... add rsp, 0x20 (7 bytes)
+ // C3 ret (1 byte)
+ //
+ // Each `mov rNN, imm64` is 10 bytes regardless of the target register:
+ // RCX REX.W 0xB9 + 8 imm (0x48 0xB9)
+ // RDX REX.W 0xBA + 8 imm (0x48 0xBA)
+ // R8 REX.WB 0xB8 + 8 imm (0x49 0xB8 — REX.W|R = 0x49)
+ // R9 REX.WB 0xB9 + 8 imm (0x49 0xB9)
+ // RAX REX.W 0xB8 + 8 imm (0x48 0xB8)
[Fact]
- public void X64_0args()
+ public void X64_0args_allocates_shadow_space_and_aligns()
{
- var s=Create(); ulong a=0x100000000,t=0x123456788;
- uint r=(uint)(t-(a+5));
- byte[] stub=s.BuildCallStub((IntPtr)(nint)a,(IntPtr)(nint)t,[],8,CallConvention.Cdecl);
- Assert.Equal(6,stub.Length); Assert.Equal(0xE8,stub[0]); Assert.Equal(r,BitConverter.ToUInt32(stub,1)); Assert.Equal(0xC3,stub[5]);
+ var s = Create();
+ ulong a = 0x100000000, t = 0x123456788;
+ byte[] stub = s.BuildCallStub(
+ (IntPtr)(nint)a, (IntPtr)(nint)t, [], 8, CallConvention.Cdecl);
+
+ // sub (7) + call (5) + add (7) + ret (1) = 20
+ Assert.Equal(20, stub.Length);
+
+ uint rel = (uint)(t - (a + 7 + 5)); // = t - a - 12
+
+ Assert.Equal([0x48, 0x81, 0xEC, 0x20, 0x00, 0x00, 0x00], stub[..7]); // sub rsp, 0x20
+ Assert.Equal(0xE8, stub[7]);
+ Assert.Equal(rel, BitConverter.ToUInt32(stub, 8));
+ Assert.Equal([0x48, 0x81, 0xC4, 0x20, 0x00, 0x00, 0x00], stub[12..19]); // add rsp, 0x20
+ Assert.Equal(0xC3, stub[19]); // ret
}
[Fact]
- public void X64_1arg_mov_ecx()
+ public void X64_1arg_loads_rcx_as_64bit()
{
- var s=Create(); ulong a=0x100000000,t=0x123456788;
- uint r=(uint)(t-(a+5+5));
- Assert.Equal([
- 0xB9,0xDD,0xCC,0xBB,0xAA,
- 0xE8,(byte)r,(byte)(r>>8),(byte)(r>>16),(byte)(r>>24),0xC3],
- s.BuildCallStub((IntPtr)(nint)a,(IntPtr)(nint)t,[0xAABBCCDD],8,CallConvention.Cdecl));
+ var s = Create();
+ ulong a = 0x100000000, t = 0x123456788;
+ byte[] stub = s.BuildCallStub(
+ (IntPtr)(nint)a, (IntPtr)(nint)t, [0xAABBCCDDu], 8, CallConvention.Cdecl);
+
+ // sub (7) + mov rcx, imm64 (10) + call (5) + add (7) + ret (1) = 30
+ Assert.Equal(30, stub.Length);
+
+ uint rel = (uint)(t - (a + 7 + 10 + 5)); // = t - a - 22
+ // stub[0..6] = sub rsp, 0x20
+ Assert.Equal([0x48, 0x81, 0xEC, 0x20, 0x00, 0x00, 0x00], stub[..7]);
+ // stub[7..16] = mov rcx, 0x00000000_AABBCCDD (zero-extended)
+ Assert.Equal(0x48, stub[7]); Assert.Equal(0xB9, stub[8]);
+ Assert.Equal(0xDD, stub[9]); Assert.Equal(0xCC, stub[10]);
+ Assert.Equal(0xBB, stub[11]); Assert.Equal(0xAA, stub[12]);
+ Assert.Equal(0x00, stub[13]); Assert.Equal(0x00, stub[14]);
+ Assert.Equal(0x00, stub[15]); Assert.Equal(0x00, stub[16]);
+ // stub[17..21] = call rel32
+ Assert.Equal(0xE8, stub[17]);
+ Assert.Equal(rel, BitConverter.ToUInt32(stub, 18));
+ // stub[22..28] = add rsp, 0x20
+ Assert.Equal([0x48, 0x81, 0xC4, 0x20, 0x00, 0x00, 0x00], stub[22..29]);
+ Assert.Equal(0xC3, stub[29]); // ret
}
[Fact]
- public void X64_4args_rcx_rdx_r8_r9()
+ public void X64_4args_loads_rcx_rdx_r8_r9_as_64bit()
{
- var s=Create(); ulong a=0x100000000,t=0x123456788;
- uint ca=(uint)a+5+5+6+6,r=(uint)(t-(ca+5));
- Assert.Equal([
- 0xB9,0x11,0x11,0x11,0x11, 0xBA,0x22,0x22,0x22,0x22,
- 0x41,0xB8,0x33,0x33,0x33,0x33, 0x41,0xB9,0x44,0x44,0x44,0x44,
- 0xE8,(byte)r,(byte)(r>>8),(byte)(r>>16),(byte)(r>>24),0xC3],
- s.BuildCallStub((IntPtr)(nint)a,(IntPtr)(nint)t,[0x11111111,0x22222222,0x33333333,0x44444444],8,CallConvention.Cdecl));
+ var s = Create();
+ ulong a = 0x100000000, t = 0x123456788;
+ byte[] stub = s.BuildCallStub(
+ (IntPtr)(nint)a, (IntPtr)(nint)t,
+ [0x11111111u, 0x22222222u, 0x33333333u, 0x44444444u], 8, CallConvention.Cdecl);
+
+ // sub (7) + 4 x mov (4*10=40) + call (5) + add (7) + ret (1) = 60
+ Assert.Equal(60, stub.Length);
+
+ uint rel = (uint)(t - (a + 7 + 40 + 5)); // = t - a - 52
+
+ Assert.Equal([0x48, 0x81, 0xEC, 0x20, 0x00, 0x00, 0x00], stub[..7]); // sub rsp, 0x20
+
+ // mov rcx, 0x11111111 (48 B9 + 8 imm) at [7..16]
+ Assert.Equal(0x48, stub[7]); Assert.Equal(0xB9, stub[8]);
+ Assert.Equal(0x11, stub[9]); Assert.Equal(0x11, stub[10]);
+ Assert.Equal(0x11, stub[11]); Assert.Equal(0x11, stub[12]);
+ Assert.Equal(0x00, stub[13]); Assert.Equal(0x00, stub[14]);
+ Assert.Equal(0x00, stub[15]); Assert.Equal(0x00, stub[16]);
+
+ // mov rdx, 0x22222222 (48 BA + 8 imm) at [17..26]
+ Assert.Equal(0x48, stub[17]); Assert.Equal(0xBA, stub[18]);
+ Assert.Equal(0x22, stub[19]); Assert.Equal(0x22, stub[20]);
+ Assert.Equal(0x22, stub[21]); Assert.Equal(0x22, stub[22]);
+ Assert.Equal(0x00, stub[23]); Assert.Equal(0x00, stub[24]);
+ Assert.Equal(0x00, stub[25]); Assert.Equal(0x00, stub[26]);
+
+ // mov r8, 0x33333333 (49 B8 + 8 imm) at [27..36]
+ Assert.Equal(0x49, stub[27]); Assert.Equal(0xB8, stub[28]);
+ Assert.Equal(0x33, stub[29]); Assert.Equal(0x33, stub[30]);
+ Assert.Equal(0x33, stub[31]); Assert.Equal(0x33, stub[32]);
+ Assert.Equal(0x00, stub[33]); Assert.Equal(0x00, stub[34]);
+ Assert.Equal(0x00, stub[35]); Assert.Equal(0x00, stub[36]);
+
+ // mov r9, 0x44444444 (49 B9 + 8 imm) at [37..46]
+ Assert.Equal(0x49, stub[37]); Assert.Equal(0xB9, stub[38]);
+ Assert.Equal(0x44, stub[39]); Assert.Equal(0x44, stub[40]);
+ Assert.Equal(0x44, stub[41]); Assert.Equal(0x44, stub[42]);
+ Assert.Equal(0x00, stub[43]); Assert.Equal(0x00, stub[44]);
+ Assert.Equal(0x00, stub[45]); Assert.Equal(0x00, stub[46]);
+
+ // call rel32 at [47..51]
+ Assert.Equal(0xE8, stub[47]);
+ Assert.Equal(rel, BitConverter.ToUInt32(stub, 48));
+
+ // add rsp, 0x20 at [52..58]
+ Assert.Equal([0x48, 0x81, 0xC4, 0x20, 0x00, 0x00, 0x00], stub[52..59]);
+ // ret at [59]
+ Assert.Equal(0xC3, stub[59]);
}
[Fact]
- public void X64_5args_push_cleanup()
+ public void X64_5args_places_first_stack_arg_in_shadow_plus_0x20()
{
- var s=Create(); ulong a=0x100000000,t=0x123456788;
- uint ca=(uint)a+5+5+6+6+5,r=(uint)(t-(ca+5));
- Assert.Equal([
- 0xB9,1,0,0,0, 0xBA,2,0,0,0,
- 0x41,0xB8,3,0,0,0, 0x41,0xB9,4,0,0,0,
- 0x68,5,0,0,0,
- 0xE8,(byte)r,(byte)(r>>8),(byte)(r>>16),(byte)(r>>24),
- 0x48,0x83,0xC4,8, 0xC3],
- s.BuildCallStub((IntPtr)(nint)a,(IntPtr)(nint)t,[1,2,3,4,5],8,CallConvention.Cdecl));
+ var s = Create();
+ ulong a = 0x100000000, t = 0x123456788;
+ byte[] stub = s.BuildCallStub(
+ (IntPtr)(nint)a, (IntPtr)(nint)t,
+ [(nuint)1, (nuint)2, (nuint)3, (nuint)4, (nuint)5], 8, CallConvention.Cdecl);
+
+ // sub (7) + 4 reg moves (40) + stack arg (mov rax 10 + mov [rsp+0x20],rax 5 = 15)
+ // + call (5) + add (7) + ret (1) = 75
+ Assert.Equal(75, stub.Length);
+
+ Assert.Equal([0x48, 0x81, 0xEC, 0x20, 0x00, 0x00, 0x00], stub[..7]);
+
+ // mov rcx, 1 at [7..16]
+ Assert.Equal(0x48, stub[7]); Assert.Equal(0xB9, stub[8]);
+ Assert.Equal(0x01, stub[9]); Assert.Equal(0x00, stub[10]);
+ Assert.Equal(0x00, stub[11]); Assert.Equal(0x00, stub[12]);
+ // mov rdx, 2 at [17..26]
+ Assert.Equal(0x48, stub[17]); Assert.Equal(0xBA, stub[18]);
+ Assert.Equal(0x02, stub[19]);
+ // mov r8, 3 at [27..36]
+ Assert.Equal(0x49, stub[27]); Assert.Equal(0xB8, stub[28]);
+ Assert.Equal(0x03, stub[29]);
+ // mov r9, 4 at [37..46]
+ Assert.Equal(0x49, stub[37]); Assert.Equal(0xB9, stub[38]);
+ Assert.Equal(0x04, stub[39]);
+
+ // mov rax, 5 (48 B8 + 8-byte imm) at [47..56]
+ Assert.Equal(0x48, stub[47]); Assert.Equal(0xB8, stub[48]);
+ Assert.Equal(0x05, stub[49]);
+ for (int k = 50; k <= 56; k++) Assert.Equal(0x00, stub[k]);
+
+ // mov [rsp + 0x20], rax (48 89 44 24 20) at [57..61]
+ Assert.Equal(0x48, stub[57]); Assert.Equal(0x89, stub[58]);
+ Assert.Equal(0x44, stub[59]); Assert.Equal(0x24, stub[60]);
+ Assert.Equal(0x20, stub[61]);
+
+ // call rel32 at [62..66]; distance = t - (a + 62 + 5) = t - a - 67
+ uint rel = (uint)(t - (a + 62 + 5));
+ Assert.Equal(0xE8, stub[62]);
+ Assert.Equal(rel, BitConverter.ToUInt32(stub, 63));
+
+ // add rsp, 0x20 at [67..73]
+ Assert.Equal([0x48, 0x81, 0xC4, 0x20, 0x00, 0x00, 0x00], stub[67..74]);
+ // ret at [74]
+ Assert.Equal(0xC3, stub[74]);
+ }
+
+ [Fact]
+ public void X64_full_64bit_args_are_preserved_not_truncated()
+ {
+ // The bug this catches: an earlier stub emitted "mov r32d, imm32" which zero-extended
+ // a 32-bit immediate into the lower half of the 64-bit register, silently dropping
+ // the high bits of any pointer-sized argument above 4 GiB.
+ var s = Create();
+ ulong a = 0x100000000, t = 0x123456788;
+ nuint wideArg = unchecked((nuint)0xDEADBEEF_CAFEBABEUL);
+ byte[] stub = s.BuildCallStub(
+ (IntPtr)(nint)a, (IntPtr)(nint)t, [wideArg], 8, CallConvention.Cdecl);
+
+ // The 8-byte immediate for arg0 lives inside `mov rcx, imm64` at bytes [9..16].
+ ulong read = BitConverter.ToUInt64(stub, 9);
+ Assert.Equal(0xDEADBEEF_CAFEBABEul, read);
+ }
+
+ [Fact]
+ public void X86_target_rejects_arg_value_larger_than_32_bits()
+ {
+ if (!Environment.Is64BitProcess)
+ {
+ // On a 32-bit host, nuint cannot exceed uint.MaxValue — the precondition
+ // cannot be exercised. Mark the test as an intentional no-op.
+ Assert.True(true);
+ return;
+ }
+
+ var s = Create();
+ nuint tooBig = unchecked((nuint)0x1_00000000UL);
+ Assert.Throws(() =>
+ s.BuildCallStub((IntPtr)0x10000000, (IntPtr)0x12345678, [tooBig], 4, CallConvention.Cdecl));
}
// ── Edge cases ────────────────────────────────────────────────────────
@@ -193,8 +348,9 @@ public class StubAssemblerTests
[Fact]
public void Many_args_cleanup_uses_imm32_form()
{
- var args = new uint[33];
- for (int i = 0; i < 33; i++) args[i] = (uint)(i * 0x10000 + i);
+ // x86 path: 33 args, stack cleanup > 127 bytes → must emit add esp, imm32 (81 C4)
+ var args = new nuint[33];
+ for (int i = 0; i < 33; i++) args[i] = (nuint)(uint)(i * 0x10000 + i);
byte[] stub = Create().BuildCallStub(
(IntPtr)0x10000000, (IntPtr)0x12345678, args, 4, CallConvention.Cdecl);
diff --git a/openspec/changes/inject-and-assemble/.openspec.yaml b/openspec/changes/archive/2026-07-21-inject-and-assemble/.openspec.yaml
similarity index 100%
rename from openspec/changes/inject-and-assemble/.openspec.yaml
rename to openspec/changes/archive/2026-07-21-inject-and-assemble/.openspec.yaml
diff --git a/openspec/changes/inject-and-assemble/design.md b/openspec/changes/archive/2026-07-21-inject-and-assemble/design.md
similarity index 100%
rename from openspec/changes/inject-and-assemble/design.md
rename to openspec/changes/archive/2026-07-21-inject-and-assemble/design.md
diff --git a/openspec/changes/inject-and-assemble/proposal.md b/openspec/changes/archive/2026-07-21-inject-and-assemble/proposal.md
similarity index 100%
rename from openspec/changes/inject-and-assemble/proposal.md
rename to openspec/changes/archive/2026-07-21-inject-and-assemble/proposal.md
diff --git a/openspec/changes/inject-and-assemble/specs/non-blocking-execute/spec.md b/openspec/changes/archive/2026-07-21-inject-and-assemble/specs/non-blocking-execute/spec.md
similarity index 100%
rename from openspec/changes/inject-and-assemble/specs/non-blocking-execute/spec.md
rename to openspec/changes/archive/2026-07-21-inject-and-assemble/specs/non-blocking-execute/spec.md
diff --git a/openspec/changes/inject-and-assemble/specs/text-assembler/spec.md b/openspec/changes/archive/2026-07-21-inject-and-assemble/specs/text-assembler/spec.md
similarity index 100%
rename from openspec/changes/inject-and-assemble/specs/text-assembler/spec.md
rename to openspec/changes/archive/2026-07-21-inject-and-assemble/specs/text-assembler/spec.md
diff --git a/openspec/changes/inject-and-assemble/tasks.md b/openspec/changes/archive/2026-07-21-inject-and-assemble/tasks.md
similarity index 100%
rename from openspec/changes/inject-and-assemble/tasks.md
rename to openspec/changes/archive/2026-07-21-inject-and-assemble/tasks.md
diff --git a/openspec/changes/whitemagic-foundation/tasks.md b/openspec/changes/whitemagic-foundation/tasks.md
index 5fac5ab..7f952aa 100644
--- a/openspec/changes/whitemagic-foundation/tasks.md
+++ b/openspec/changes/whitemagic-foundation/tasks.md
@@ -21,15 +21,15 @@
## 3. Managed Assembler (spec: managed-assembler)
-- [ ] 3.1 Add tests for `EmitU8`/`EmitU32`/`EmitU64` little-endian primitives
-- [ ] 3.2 Implement `WhiteMagic/Assembly/StubAssembler.cs` emitters + `IAssembler` interface to pass 3.1
-- [ ] 3.3 Add tests for x86 cdecl stub encoding (reverse push, call, `add esp, N*4`, ret) with known byte expectations
-- [ ] 3.4 Implement x86 cdecl stub to pass 3.3
-- [ ] 3.5 Add tests for stdcall (no caller cleanup), thiscall (ecx = this), fastcall (ecx/edx) x86 stubs
-- [ ] 3.6 Implement x86 stdcall/thiscall/fastcall stubs to pass 3.5
-- [ ] 3.7 Add tests for x64 stub argument-register placement and call
-- [ ] 3.8 Implement x64 stub to pass 3.7
-- [ ] 3.9 Confirm no FASM/`ManagedFasm` reference exists in `WhiteMagic` output (assert via a test that scans loaded references)
+- [x] 3.1 Add tests for `EmitU8`/`EmitU32`/`EmitU64` little-endian primitives
+- [x] 3.2 Implement `WhiteMagic/Assembly/StubAssembler.cs` emitters + `IAssembler` interface to pass 3.1
+- [x] 3.3 Add tests for x86 cdecl stub encoding (reverse push, call, `add esp, N*4`, ret) with known byte expectations
+- [x] 3.4 Implement x86 cdecl stub to pass 3.3
+- [x] 3.5 Add tests for stdcall (no caller cleanup), thiscall (ecx = this), fastcall (ecx/edx) x86 stubs
+- [x] 3.6 Implement x86 stdcall/thiscall/fastcall stubs to pass 3.5
+- [x] 3.7 Add tests for x64 stub argument-register placement and call. Now also asserts Microsoft x64 ABI compliance: `sub rsp, 0x20` shadow-space allocation (stack args land at `[rsp + 0x20 + 8*(i-4)]`), 16-byte stack alignment at the inner `call target`, `mov r64, imm64` loads for RCX/RDX/R8/R9 with the full 64-bit immediate (regression test for the old `mov r32d, imm32` truncation bug).
+- [x] 3.8 Implement x64 stub to pass 3.7. Builds a compliant Microsoft x64 ABI frame: `sub rsp, 0x20`, 64-bit register loads, stack-argv above the shadow window, `call rel32`, `add rsp, 0x20`, `ret`. Accepts `nuint[]` so callers can pass full 64-bit pointers unchanged (x86 path truncates `nuint` → `uint` with a range check).
+- [x] 3.9 Confirm no FASM/`ManagedFasm` reference exists in `WhiteMagic` output (assert via a test that scans loaded references)
## 4. Crash-Safe Execution Slice (spec: remote-execution, function-hooking)
diff --git a/openspec/specs/non-blocking-execute/spec.md b/openspec/specs/non-blocking-execute/spec.md
new file mode 100644
index 0000000..e017bb0
--- /dev/null
+++ b/openspec/specs/non-blocking-execute/spec.md
@@ -0,0 +1,45 @@
+# non-blocking-execute Specification
+
+## Purpose
+TBD - created by archiving change inject-and-assemble. Update Purpose after archive.
+## Requirements
+### Requirement: InjectAndExecuteEx creates remote thread without waiting
+
+`BlackMagic.InjectAndExecuteEx(IntPtr startAddress, IntPtr parameter)` injects code at `startAddress` into the opened process, creates a remote thread with `parameter`, and returns the thread handle immediately without waiting for the thread to exit.
+
+#### Scenario: successful non-blocking execution
+- **WHEN** a process is open and `InjectAndExecuteEx(addr, param)` is called with a valid code address
+- **THEN** a remote thread is created in the target process and a valid `SafeMemoryHandle` is returned
+
+#### Scenario: no process open
+- **WHEN** no process is open and `InjectAndExecuteEx(addr, param)` is called
+- **THEN** `null` is returned
+
+### Requirement: InjectAndExecuteEx single-parameter overload
+
+`BlackMagic.InjectAndExecuteEx(IntPtr startAddress)` calls `InjectAndExecuteEx(startAddress, IntPtr.Zero)`.
+
+#### Scenario: parameter-less non-blocking execution
+- **WHEN** `InjectAndExecuteEx(addr)` is called with a valid address
+- **THEN** the thread is created with parameter `IntPtr.Zero`
+
+### Requirement: InjectAndExecuteEx from assembly text
+
+`BlackMagic.InjectAndExecuteEx(string asm)` assembles the text via `AsmBuilder`, allocates remote memory, writes the bytes, calls `InjectAndExecuteEx` on the allocated address, and returns the thread handle.
+
+#### Scenario: execute assembly text non-blocking
+- **WHEN** `InjectAndExecuteEx("nop")` is called with a process open
+- **THEN** the text is assembled to bytes, written to remote memory, a thread is started, and the handle is returned
+
+#### Scenario: assembly failure
+- **WHEN** `InjectAndExecuteEx("invalidinstruction")` is called
+- **THEN** `ArgumentException` is thrown with the assembly error
+
+### Requirement: InjectAndExecute from assembly text (blocking convenience)
+
+`BlackMagic.InjectAndExecute(string asm)` assembles the text, allocates remote memory, writes the bytes, calls `Execute` (blocking, 10s timeout), and returns the exit code.
+
+#### Scenario: execute assembly text blocking
+- **WHEN** `InjectAndExecute("mov eax, 42\nret")` is called with a process open
+- **THEN** the text is assembled, injected, executed, and the thread exit code is returned
+
diff --git a/openspec/specs/text-assembler/spec.md b/openspec/specs/text-assembler/spec.md
new file mode 100644
index 0000000..64d24ef
--- /dev/null
+++ b/openspec/specs/text-assembler/spec.md
@@ -0,0 +1,88 @@
+# text-assembler Specification
+
+## Purpose
+TBD - created by archiving change inject-and-assemble. Update Purpose after archive.
+## Requirements
+### Requirement: AsmBuilder assembles x86 instruction text to byte array
+
+`AsmBuilder.Assemble(string source)` parses x86 assembly text and returns the corresponding `byte[]` machine code.
+
+#### Scenario: single instruction
+- **WHEN** `AsmBuilder.Assemble("nop")` is called
+- **THEN** the result is `[0x90]`
+
+#### Scenario: multiple instructions
+- **WHEN** `AsmBuilder.Assemble("pushad\npopad")` is called
+- **THEN** the result is `[0x60, 0x61]`
+
+#### Scenario: instruction with immediate operand
+- **WHEN** `AsmBuilder.Assemble("mov eax, 1")` is called
+- **THEN** the result is `[0xB8, 0x01, 0x00, 0x00, 0x00]`
+
+### Requirement: AsmBuilder supports register operands
+
+Supported registers: `eax`, `ecx`, `edx`, `ebx`, `esp`, `ebp`, `esi`, `edi` (and 8-bit: `al`, `cl`, `dl`, `bl`, `ah`, `ch`, `dh`, `bh`).
+
+#### Scenario: register-to-register move
+- **WHEN** `AsmBuilder.Assemble("mov eax, ecx")` is called
+- **THEN** the result is `[0x89, 0xC8]` (mov eax, ecx encoding)
+
+#### Scenario: register encoding
+- **WHEN** registers are used in instructions
+- **THEN** each register maps to its correct 3-bit encoding (eax=0, ecx=1, edx=2, ebx=3, esp=4, ebp=5, esi=6, edi=7)
+
+### Requirement: AsmBuilder supports labels and jumps
+
+Labels are defined with `@name:` and referenced with `jmp @name` or `je @name`. Forward and backward references are resolved in a second pass.
+
+#### Scenario: forward jump
+- **WHEN** `AsmBuilder.Assemble("jmp @skip\nnop\n@skip:\nret")` is called
+- **THEN** the jump skips exactly over the `nop` (2 bytes) and lands on `ret`
+
+#### Scenario: backward jump
+- **WHEN** `AsmBuilder.Assemble("@loop:\nnop\njmp @loop")` is called
+- **THEN** the jump targets the earlier label correctly
+
+#### Scenario: multiple labels
+- **WHEN** multiple labels are used in one source
+- **THEN** each label resolves to its correct byte offset
+
+### Requirement: AsmBuilder SetPassLimit controls iteration
+
+`AsmBuilder.SetPassLimit(int limit)` sets the maximum number of assembly passes for label resolution. Default is 10. If the limit is exceeded before all labels resolve, `InvalidOperationException` is thrown.
+
+#### Scenario: default pass limit
+- **WHEN** no `SetPassLimit` is called
+- **THEN** the assembler uses 10 passes maximum
+
+#### Scenario: custom pass limit
+- **WHEN** `SetPassLimit(20)` is called
+- **THEN** the assembler uses 20 passes maximum
+
+#### Scenario: pass limit exceeded
+- **WHEN** forward references cannot resolve within the pass limit
+- **THEN** `InvalidOperationException` is thrown with label resolution details
+
+### Requirement: AsmBuilder reports clear errors
+
+Unknown instructions, missing operands, and invalid register names produce `ArgumentException` with the line number and offending text.
+
+#### Scenario: unknown instruction
+- **WHEN** `AsmBuilder.Assemble("xyzw")` is called
+- **THEN** `ArgumentException` is thrown mentioning line 1 and "xyzw"
+
+#### Scenario: missing operand
+- **WHEN** `AsmBuilder.Assemble("mov")` is called (no operands)
+- **THEN** `ArgumentException` is thrown mentioning missing operand
+
+### Requirement: AsmBuilder supported instruction set
+
+The following x86 instructions are supported:
+- **Data movement**: `mov`, `push`, `pop`, `pushad`, `popad`, `lea`
+- **Arithmetic**: `add`, `sub`, `inc`, `dec`, `xor`, `and`, `or`, `cmp`, `test`
+- **Control flow**: `jmp`, `je`, `jne`, `call`, `ret`, `nop`, `hlt`
+
+#### Scenario: all instructions produce valid bytes
+- **WHEN** each supported instruction is assembled individually
+- **THEN** it produces the correct x86 machine code encoding
+