Prevent invalid SaveData writes from damaging guest memory (#444)

Add an optional write monitor so the team can find future memory damage on each supported desktop system.
2026-07-22 19:06:15 +08:00 · 2026-07-19 12:27:17 -05:00
parent d7f6e3f578
commit bc51cc2c4d
8 changed files with 437 additions and 21 deletions
@@ -0,0 +1,77 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+using SharpEmu.HLE;
+using Xunit;
+
+namespace SharpEmu.Libs.Tests.HLE;
+
+public sealed class GuestWriteWatchTests
+{
+    [Theory]
+    [InlineData(0x0000001000000001, "torn")]
+    [InlineData(0x0000FFFF00000001, "torn")]
+    [InlineData(0x0000000008000000, "shift")]
+    [InlineData(0x0000000080015F00, "shift")]
+    [InlineData(0x0000000007FFFFFF, null)]
+    [InlineData(0x0000000009000000, null)]
+    [InlineData(0x000000003F800000, null)]
+    [InlineData(0x0000000080015F01, null)]
+    [InlineData(0x0001000000000001, null)]
+    public void ClassifyBulkValue_RecognizesCorruptionSignatures(ulong value, string? expected)
+    {
+        Assert.Equal(expected, GuestWriteWatch.ClassifyBulkValue(value));
+    }
+
+    [Theory]
+    [InlineData(0, 0)]
+    [InlineData(1, 7)]
+    [InlineData(3, 5)]
+    [InlineData(7, 1)]
+    [InlineData(8, 0)]
+    public void FirstAlignedOffset_ReturnsTheNextEightByteBoundary(ulong address, int expected)
+    {
+        Assert.Equal(expected, GuestWriteWatch.FirstAlignedOffset(address));
+    }
+
+    [Theory]
+    [InlineData(0x1000, 8, 0x1000, true)]
+    [InlineData(0x0FFF, 1, 0x1000, false)]
+    [InlineData(0x0FFF, 2, 0x1000, true)]
+    [InlineData(0x1008, 1, 0x1000, false)]
+    [InlineData(ulong.MaxValue - 3, 4, ulong.MaxValue - 1, true)]
+    [InlineData(ulong.MaxValue, 1, ulong.MaxValue, true)]
+    [InlineData(0x1000, 0, 0x1000, false)]
+    public void Overlaps_HandlesBoundariesWithoutOverflow(
+        ulong address,
+        int length,
+        ulong slot,
+        bool expected)
+    {
+        Assert.Equal(expected, GuestWriteWatch.Overlaps(address, length, slot));
+    }
+
+    [Theory]
+    [InlineData(0x10000, 0xF2, true)]
+    [InlineData(0x10001, 0xF2, false)]
+    [InlineData(0x10000, 0xF1, false)]
+    public void IsPoolMapping_RequiresTheExpectedSizeAndProtection(
+        ulong length,
+        int protection,
+        bool expected)
+    {
+        Assert.Equal(expected, GuestWriteWatch.IsPoolMapping(length, protection));
+    }
+
+    [Theory]
+    [InlineData(null, 0)]
+    [InlineData("", 0)]
+    [InlineData("not-hex", 0)]
+    [InlineData("80", 0x80)]
+    [InlineData("0x80", 0x80)]
+    [InlineData(" 0X801DB3BBB ", 0x801DB3BBB)]
+    public void Parse_HandlesHexadecimalWatchValues(string? text, ulong expected)
+    {
+        Assert.Equal(expected, GuestWriteWatch.Parse(text));
+    }
+}
@@ -31,6 +31,9 @@ public sealed class SaveDataExportsTests : IDisposable
    private const ulong SyncParam = Base + 0xC80;
    private const ulong SetupParam = Base + 0xD00;
    private const ulong SetupResult = Base + 0xD80;
+    private const ulong TransactionOut = Base + 0xE00;
+    private const ulong StaleR8 = Base + 0xE08;
+    private const ulong StaleR9 = Base + 0xE10;

    private const int NoEvent = unchecked((int)0x809F0008);
    private const int ParameterError = unchecked((int)0x809F0000);
@@ -225,4 +228,64 @@ public sealed class SaveDataExportsTests : IDisposable
            unchecked((int)0x809F0008),
            SaveDataExports.SaveDataDelete(Reg(rdi: DeleteParam)));
    }
+
+    [Fact]
+    public void CreateTransactionResource_WithoutOutPointer_DoesNotProbeStaleRegisters()
+    {
+        const uint sentinel = 0xA5A5A5A5;
+        Assert.True(_ctx.TryWriteUInt32(TransactionOut, sentinel));
+        Assert.True(_ctx.TryWriteUInt32(StaleR8, sentinel));
+        Assert.True(_ctx.TryWriteUInt32(StaleR9, sentinel));
+
+        var ctx = Reg(rdi: UserId, rdx: 0, rcx: TransactionOut);
+        ctx[CpuRegister.R8] = StaleR8;
+        ctx[CpuRegister.R9] = StaleR9;
+
+        Assert.Equal(0, SaveDataExports.SaveDataCreateTransactionResource(ctx));
+        Assert.True(_ctx.TryReadUInt32(TransactionOut, out var rcxValue));
+        Assert.True(_ctx.TryReadUInt32(StaleR8, out var r8Value));
+        Assert.True(_ctx.TryReadUInt32(StaleR9, out var r9Value));
+        Assert.Equal(sentinel, rcxValue);
+        Assert.Equal(sentinel, r8Value);
+        Assert.Equal(sentinel, r9Value);
+    }
+
+    [Fact]
+    public void CreateTransactionResource_WithOutPointerFlag_WritesOnlyRcx()
+    {
+        const uint sentinel = 0xA5A5A5A5;
+        Assert.True(_ctx.TryWriteUInt32(TransactionOut, 0));
+        Assert.True(_ctx.TryWriteUInt32(StaleR8, sentinel));
+        Assert.True(_ctx.TryWriteUInt32(StaleR9, sentinel));
+
+        var ctx = Reg(rdi: UserId, rdx: 1, rcx: TransactionOut);
+        ctx[CpuRegister.R8] = StaleR8;
+        ctx[CpuRegister.R9] = StaleR9;
+
+        Assert.Equal(0, SaveDataExports.SaveDataCreateTransactionResource(ctx));
+        Assert.True(_ctx.TryReadUInt32(TransactionOut, out var resource));
+        Assert.True(_ctx.TryReadUInt32(StaleR8, out var r8Value));
+        Assert.True(_ctx.TryReadUInt32(StaleR9, out var r9Value));
+        Assert.NotEqual(0u, resource);
+        Assert.Equal(sentinel, r8Value);
+        Assert.Equal(sentinel, r9Value);
+    }
+
+    [Fact]
+    public void CreateTransactionResource_WithLegacyOutPointer_WritesOnlyRdx()
+    {
+        const uint sentinel = 0xA5A5A5A5;
+        Assert.True(_ctx.TryWriteUInt32(TransactionOut, 0));
+        Assert.True(_ctx.TryWriteUInt32(StaleR8, sentinel));
+
+        Assert.Equal(
+            0,
+            SaveDataExports.SaveDataCreateTransactionResource(
+                Reg(rdi: UserId, rdx: TransactionOut, rcx: StaleR8)));
+
+        Assert.True(_ctx.TryReadUInt32(TransactionOut, out var resource));
+        Assert.True(_ctx.TryReadUInt32(StaleR8, out var rcxValue));
+        Assert.NotEqual(0u, resource);
+        Assert.Equal(sentinel, rcxValue);
+    }
 }