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review fixes: rename CallingConvention→CallConvention, seal, edge cases

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HIGH: rename CallingConvention to CallConvention to avoid BCL collision
 with System.Runtime.InteropServices.CallingConvention.

FIXES:
- checked(uint) casts for x86 pointer truncation (ArgumentOverflow)
- checked distance for E8 rel32 range (>2 GiB → throw)
- add esp, imm32 (81 /0 id) when cleanup > 127 bytes
- pointerSize validation (throw on != 4 and != 8)
- switch default: throw on unknown convention
- track argIndex instead of args[1..] slicing
- EmitMovRegImm32 helper (avoids manual ip tracking bugs)
- seal StubAssembler
- IAssembler doc: note BuildCallStub is StubAssembler-specific
- thiscall 0-args throws test; fastcall 0-args is valid
- update remote-execution spec example to CallConvention.Cdecl

All passing (total: 93).
This commit is contained in:
kbe
2026-07-21 19:59:48 +02:00
parent f39ecf820d
commit 2ecdd147a7
5 changed files with 185 additions and 60 deletions
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WhiteMagic/Assembly/StubAssembler.cs
+103 -42
View File
@@ -11,7 +11,7 @@ namespace WhiteMagic.Assembly;
/// emitter, not a text assembler). Use <see cref="IcedAssembler"/> (Phase 8) for
/// arbitrary mnemonics.
/// </remarks>
public class StubAssembler : IAssembler
public sealed class StubAssembler : IAssembler
{
/// <inheritdoc />
public byte[] Assemble(string assemblyText, ulong origin = 0)
@@ -41,70 +41,113 @@ public class StubAssembler : IAssembler
// ── Call-stub builders ─────────────────────────────────────────────────
/// <summary>
/// Builds a calling-convention call stub for x86 or x64.
/// </summary>
/// <param name="stubAddress">Where the stub lands (for E8 rel32 encoding).</param>
/// <param name="targetAddress">Function to call.</param>
/// <param name="arguments">Argument values (uint[] — each 4 or 8 bytes per pointerSize).</param>
/// <param name="pointerSize">4 (x86) or 8 (x64).</param>
/// <param name="convention">Calling convention.</param>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="pointerSize"/> is not 4 or 8,
/// or <paramref name="convention"/> is not known, or the distance between stub and target
/// exceeds the E8 rel32 range.</exception>
public byte[] BuildCallStub(IntPtr stubAddress, IntPtr targetAddress,
uint[] arguments, int pointerSize, CallingConvention convention)
uint[] arguments, int pointerSize, CallConvention convention)
{
var buffer = new List<byte>(64);
if (pointerSize == 4)
BuildX86Stub(buffer, (uint)stubAddress, (uint)targetAddress, arguments, convention);
{
BuildX86Stub(buffer, checked((uint)stubAddress), checked((uint)targetAddress),
arguments, convention);
}
else if (pointerSize == 8)
{
// Windows x64 uses a single ABI — the convention parameter is unused.
BuildX64Stub(buffer, (ulong)(nint)stubAddress, (ulong)(nint)targetAddress, arguments);
}
else
BuildX64Stub(buffer, (ulong)stubAddress, (ulong)targetAddress, arguments);
{
throw new ArgumentOutOfRangeException(nameof(pointerSize), pointerSize,
$"Expected 4 (x86) or 8 (x64), got {pointerSize}.");
}
return buffer.ToArray();
}
private void BuildX86Stub(List<byte> buffer, uint stubAddr,
uint target, uint[] args, CallingConvention convention)
uint target, uint[] args, CallConvention convention)
{
uint current = stubAddr;
int argIndex = 0;
switch (convention)
{
case CallingConvention.Thiscall when args.Length >= 1:
buffer.Add(0xB9); // mov ecx, arg0
EmitU32(buffer, args[0]);
current += 5;
args = args[1..];
case CallConvention.Thiscall when args.Length - argIndex >= 1:
EmitMovRegImm32(buffer, 0xB9, args[argIndex], ref current); // mov ecx, arg0
argIndex++;
break;
case CallingConvention.Fastcall:
if (args.Length >= 1)
case CallConvention.Fastcall:
if (args.Length - argIndex >= 1)
{
buffer.Add(0xB9); // mov ecx, arg0
EmitU32(buffer, args[0]);
current += 5;
args = args[1..];
EmitMovRegImm32(buffer, 0xB9, args[argIndex], ref current); // mov ecx, arg0
argIndex++;
}
if (args.Length >= 1)
if (args.Length - argIndex >= 1)
{
buffer.Add(0xBA); // mov edx, arg1
EmitU32(buffer, args[0]);
current += 5;
args = args[1..];
EmitMovRegImm32(buffer, 0xBA, args[argIndex], ref current); // mov edx, arg1
argIndex++;
}
break;
case CallConvention.Cdecl:
case CallConvention.Stdcall:
break;
default:
throw new ArgumentOutOfRangeException(nameof(convention), convention,
$"Unsupported calling convention: {convention}.");
}
// Push remaining args in reverse order
for (int i = args.Length - 1; i >= 0; i--)
// Push remaining args in reverse order (right-to-left)
for (int i = args.Length - 1; i >= argIndex; i--)
{
current += 5;
buffer.Add(0x68); // push imm32
EmitU32(buffer, args[i]);
current += 5;
}
// call rel32
uint rel32 = target - (current + 5);
long distance = (long)target - (long)(current + 5);
if (distance < int.MinValue || distance > int.MaxValue)
{
throw new ArgumentOutOfRangeException(
$"target (0x{target:X}) is >2 GiB from stub (0x{stubAddr:X}); " +
"E8 rel32 cannot encode this distance. Place the stub closer to the target.");
}
buffer.Add(0xE8);
EmitU32(buffer, rel32);
EmitU32(buffer, (uint)distance);
current += 5;
// Caller cleanup (cdecl only)
if (convention == CallingConvention.Cdecl && args.Length > 0)
int stackCount = args.Length - argIndex;
if (convention == CallConvention.Cdecl && stackCount > 0)
{
buffer.Add(0x83); // add esp, imm8
buffer.Add(0xC4);
buffer.Add((byte)(args.Length * 4));
int cleanup = stackCount * 4;
if (cleanup <= 127)
{
buffer.Add(0x83); // add esp, imm8
buffer.Add(0xC4);
buffer.Add((byte)cleanup);
}
else
{
buffer.Add(0x81); // add esp, imm32
buffer.Add(0xC4);
EmitU32(buffer, (uint)cleanup);
}
}
buffer.Add(0xC3); // ret
@@ -113,11 +156,11 @@ public class StubAssembler : IAssembler
private void BuildX64Stub(List<byte> buffer, ulong stubAddr,
ulong target, uint[] args)
{
// Windows x64 single ABI: first 4 args in RCX, RDX, R8D, R9D.
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
var regCodes = new byte[] { 0xB9, 0xBA, 0xB8, 0xB9 };
var rexBytes = new byte[] { 0x00, 0x00, 0x41, 0x41 };
int regCount = Math.Min(args.Length, 4);
for (int i = 0; i < regCount; i++)
@@ -129,33 +172,51 @@ public class StubAssembler : IAssembler
current += (rexBytes[i] != 0 ? 6u : 5u);
}
// Push remaining args in reverse order (right-to-left)
// Push remaining args in reverse order
for (int i = args.Length - 1; i >= 4; i--)
{
buffer.Add(0x68); // push imm32
EmitU32(buffer, args[i]);
current += 5;
buffer.Add(0x68);
EmitU32(buffer, args[i]);
}
// call rel32
uint rel32 = (uint)(target - (current + 5));
long distance = (long)target - (long)(current + 5);
if (distance < int.MinValue || distance > int.MaxValue)
{
throw new ArgumentOutOfRangeException(
"target and stub are >2 GiB apart; E8 rel32 cannot encode this distance.");
}
buffer.Add(0xE8);
EmitU32(buffer, rel32);
EmitU32(buffer, (uint)distance);
// Caller cleanup: pop any args pushed on stack
// 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(0x48); // REX.W
buffer.Add(bytes <= 127 ? (byte)0x83 : (byte)0x81); // add r/m64, imm8/imm32
buffer.Add(0xC4); // rsp
buffer.Add(0xC4); // rsp
if (bytes <= 127)
buffer.Add((byte)bytes);
else
EmitU32(buffer, (uint)bytes);
}
buffer.Add(0xC3); // ret
buffer.Add(0xC3);
}
// ── Instruction helpers ────────────────────────────────────────────────
/// <summary>Emit <c>mov reg32, imm32</c> and advances <paramref name="ip"/> by 5.</summary>
private static void EmitMovRegImm32(List<byte> buffer, byte opcode, uint imm32, ref uint ip)
{
buffer.Add(opcode);
buffer.Add((byte)imm32);
buffer.Add((byte)(imm32 >> 8));
buffer.Add((byte)(imm32 >> 16));
buffer.Add((byte)(imm32 >> 24));
ip += 5;
}
}