[NAND]: Fix a bug with metadata

xenon-emu · Mar 4, 2025 · eb06132 · eb06132
1 parent 4b4fee0
commit eb06132
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Showing 2 changed files with 43 additions and 19 deletions.
diff --git a/Xenon/Core/NAND/NAND.cpp b/Xenon/Core/NAND/NAND.cpp
@@ -77,33 +77,36 @@ void NAND::Write(u64 writeAddress, u64 data, u8 byteCount) {
 
 //*Checks ECD Page.
 bool NAND::CheckPageECD(u8 *data, s32 offset) {
-  u8 actualData[4]{};
-  u8 calculatedECD[4]{};
+  NANDMetadata metadata{};
+  NANDMetadata calculatedMetadata{};
 
   // This directly takes the NAND block's metadata
-  // and skips to the last 4 ECC bytes, calculates the error corrrecting data on it, 
+  // and calculates the error corrrecting data on the ECC bytes 
   // and checks against what the nand provided
-  memcpy(actualData, rawNANDData.data() + (offset + 0x200 + 0xC), sizeof(actualData));
+  memcpy(&metadata, rawNANDData.data() + (offset + 0x200), sizeof(metadata));
 
-  CalculateECD(data, offset, calculatedECD);
+  CalculateECD(data, offset, calculatedMetadata);
 
   return (
-      calculatedECD[0] == actualData[0] && calculatedECD[1] == actualData[1] &&
-      calculatedECD[2] == actualData[2] && calculatedECD[3] == actualData[3]);
+    metadata.ECC3 == calculatedMetadata.ECC3 &&
+    metadata.ECC2 == calculatedMetadata.ECC2 &&
+    metadata.ECC1 == calculatedMetadata.ECC1 &&
+    metadata.ECC0 == calculatedMetadata.ECC0
+  );
 }
 
 //*Calculates the ECD.
-void NAND::CalculateECD(u8 *data, int offset, u8 ret[]) {
+void NAND::CalculateECD(u8 *data, int offset, NANDMetadata &metadata) {
   u32 i, val = 0, v = 0;
   u32 count = 0;
   for (i = 0; i < 0x1066; i++) {
     if ((i & 31) == 0) {
-      u32 value = u32((u8)(data[count + offset]) << 24 |
-                      (u8)(data[count + offset + 1]) << 16 |
-                      (u8)(data[count + offset + 2]) << 8 |
-                      (u8)(data[count + offset + 3]));
-      value = std::byteswap<u32>(value);
-      v = ~value;
+      v = ~std::byteswap<u32>(
+        (u8)(data[count + offset + 0]) << 24 |
+        (u8)(data[count + offset + 1]) << 16 |
+        (u8)(data[count + offset + 2]) << 8  |
+        (u8)(data[count + offset + 3])
+      );
       count += 4;
     }
     val ^= v & 1;
@@ -113,10 +116,11 @@ void NAND::CalculateECD(u8 *data, int offset, u8 ret[]) {
     val >>= 1;
   }
   val = ~val;
-  ret[0] = (val << 6);
-  ret[1] = (val >> 2) & 0xFF;
-  ret[2] = (val >> 10) & 0xFF;
-  ret[3] = (val >> 18) & 0xFF;
+  // Shift ECC3 to the upper 2 bits
+  metadata.ECC3 = (val << 6);
+  metadata.ECC2 = (val >> 2) & 0xFF;
+  metadata.ECC1 = (val >> 10) & 0xFF;
+  metadata.ECC0 = (val >> 18) & 0xFF;
 }
 
 // Check if the nand provided to us contains a valid metadata or not

diff --git a/Xenon/Core/NAND/NAND.h b/Xenon/Core/NAND/NAND.h
@@ -20,6 +20,26 @@ enum MetaType {
   metaTypeNone = 4           // No spare type or unknown
 };
 
+struct NANDMetadata {
+  u8 BlockID1; // LBA/ID = (((BlockID0 & 0xF) << 8) + (BlockID1))
+  u8 BlockID0 : 4;
+  u8 FsUnused0 : 4;
+  u8 FsSequence0; // Not reversed
+  u8 FsSequence1;
+  u8 FsSequence2;
+  u8 BadBlock;
+  u8 FsSequence3;
+  u8 FsSize1; // ((FsSize0 << 8) + FsSize1) = cert size
+  u8 FsSize0;
+  u8 FsPageCount; // Free pages left in block (ie: If 3 pages are used by cert then this would be 29:0x1D)
+  u8 FsUnused1[0x2];
+  u8 FsBlockType : 6;
+  u8 ECC3 : 2;
+  u8 ECC2; // 14 bit ECD
+  u8 ECC1;
+  u8 ECC0;
+};
+
 class NAND : public SystemDevice {
 public:
   NAND(const char *deviceName, const std::string filePath,
@@ -39,7 +59,7 @@ class NAND : public SystemDevice {
   bool CheckMagic(u8 magicOut[2] = nullptr);
   void CheckSpare();
   bool CheckPageECD(u8 *data, s32 offset);
-  void CalculateECD(u8 *data, int offset, u8 ret[]);
+  void CalculateECD(u8 *data, int offset, NANDMetadata& metadata);
   MetaType DetectSpareType(bool firstTry = true);
 
   // void SeekPos(s32 address);