Refactor DSi_NAND (#1844)

* Refactor diskio's contents

- Change ff_disk_read_cb/write_cb into a std::function instead of a raw pointer
- Add const specifiers as needed

* Refactor DSi_NAND to manage the file system's mounted lifetime with RAII

* Split NANDMount into NANDMount and NANDImage

- NANDImage is used for information about the NAND that doesn't require decryption or filesystem access
- NANDMount is used to actually access the file system
- Both classes manage their respective resources (the NAND file handle and the NAND's mount) with RAII
- Also split the file loading into another function that I will remove in a later PR

* Make NANDMount immovable

* Remove NAND-loading code that I had sectioned off into a function

- Incomplete copypasta
- I must have gotten distracted

* Tidy up NANDImage's initialization

- Don't unmount the disk image if the constructor fails (that's NANDMount's job now)
- Only assign CurFile if the constructor succeeds

* Add some const-correctness

* Move DSi NAND initialization to the frontend

- The NANDImage is now installed via a unique_ptr in DSi

* Remove Platform::DSi_NANDPath

- Not Config::DSiNANDPath; that can still be configured as usual
- The core no longer needs to care

20 files changed, 443 insertions, 292 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 850ec7c..0fa9684 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -25,6 +25,7 @@ add_library(core STATIC
     DSi_NWifi.cpp
     DSi_SD.cpp
     DSi_SPI_TSC.cpp
+    FATIO.cpp
     FATStorage.cpp
     FIFO.h
     GBACart.cpp
@@ -51,7 +52,6 @@ add_library(core STATIC
     Wifi.cpp
     WifiAP.cpp
 
-    fatfs/diskio.c
     fatfs/ff.c
     fatfs/ffsystem.c
     fatfs/ffunicode.c
diff --git a/src/DSi.cpp b/src/DSi.cpp
index cdec819..17d79a6 100644
--- a/src/DSi.cpp
+++ b/src/DSi.cpp
@@ -75,12 +75,10 @@ u32 NWRAMMask[2][3];
 u32 NDMACnt[2];
 DSi_NDMA* NDMAs[8];
 
+std::unique_ptr<DSi_NAND::NANDImage> NANDImage;
 DSi_SDHost* SDMMC;
 DSi_SDHost* SDIO;
 
-u64 ConsoleID;
-u8 eMMC_CID[16];
-
 // FIXME: these currently have no effect (and aren't stored in a savestate)
 //        ... not that they matter all that much
 u8 GPIO_Data;
@@ -149,6 +147,10 @@ void DeInit()
     SDMMC = nullptr;
     delete SDIO;
     SDIO = nullptr;
+
+    NANDImage = nullptr;
+    // The NANDImage is cleaned up (and its underlying file closed)
+    // as part of unique_ptr's destructor
 }
 
 void Reset()
@@ -528,24 +530,25 @@ void SetupDirectBoot()
             ARM9Write32(0x02FFE000+i, tmp);
         }
 
-        if (DSi_NAND::Init(&DSi::ARM7iBIOS[0x8308]))
-        {
-            DSi_NAND::DSiFirmwareSystemSettings userdata {};
-            DSi_NAND::ReadUserData(userdata);
-            for (u32 i = 0; i < 0x128; i+=4)
-                ARM9Write32(0x02000400+i, *(u32*)&userdata.Bytes[0x88+i]);
-
-            DSi_NAND::DSiSerialData hwinfoS {};
-            DSi_NAND::DSiHardwareInfoN hwinfoN;
-            DSi_NAND::ReadHardwareInfo(hwinfoS, hwinfoN);
+        if (NANDImage && *NANDImage)
+        { // If a NAND image is installed, and it's valid...
+            if (DSi_NAND::NANDMount nand = DSi_NAND::NANDMount(*NANDImage))
+            {
+                DSi_NAND::DSiFirmwareSystemSettings userdata {};
+                nand.ReadUserData(userdata);
+                for (u32 i = 0; i < 0x128; i+=4)
+                    ARM9Write32(0x02000400+i, *(u32*)&userdata.Bytes[0x88+i]);
 
-            for (u32 i = 0; i < 0x14; i+=4)
-                ARM9Write32(0x02000600+i, *(u32*)&hwinfoN[0x88+i]);
+                DSi_NAND::DSiSerialData hwinfoS {};
+                DSi_NAND::DSiHardwareInfoN hwinfoN;
+                nand.ReadHardwareInfo(hwinfoS, hwinfoN);
 
-            for (u32 i = 0; i < 0x18; i+=4)
-                ARM9Write32(0x02FFFD68+i, *(u32*)&hwinfoS.Bytes[0x88+i]);
+                for (u32 i = 0; i < 0x14; i+=4)
+                    ARM9Write32(0x02000600+i, *(u32*)&hwinfoN[0x88+i]);
 
-            DSi_NAND::DeInit();
+                for (u32 i = 0; i < 0x18; i+=4)
+                    ARM9Write32(0x02FFFD68+i, *(u32*)&hwinfoS.Bytes[0x88+i]);
+            }
         }
 
         SPI_Firmware::WifiBoard nwifiver = SPI_Firmware::GetFirmware()->Header().WifiBoard;
@@ -728,15 +731,21 @@ void SoftReset()
 
 bool LoadNAND()
 {
+    if (!NANDImage)
+    {
+        Log(LogLevel::Error, "No NAND image loaded\n");
+        return false;
+    }
     Log(LogLevel::Info, "Loading DSi NAND\n");
 
-    if (!DSi_NAND::Init(&DSi::ARM7iBIOS[0x8308]))
+    DSi_NAND::NANDMount nandmount(*NANDImage);
+    if (!nandmount)
     {
         Log(LogLevel::Error, "Failed to load DSi NAND\n");
         return false;
     }
 
-    FileHandle* nand = DSi_NAND::GetFile();
+    FileHandle* nand = NANDImage->GetFile();
 
     // Make sure NWRAM is accessible.
     // The Bits are set to the startup values in Reset() and we might
@@ -892,13 +901,9 @@ bool LoadNAND()
         }
     }
 
-#define printhex(str, size) { for (int z = 0; z < (size); z++) printf("%02X", (str)[z]); printf("\n"); }
-#define printhex_rev(str, size) { for (int z = (size)-1; z >= 0; z--) printf("%02X", (str)[z]); printf("\n"); }
-
-    DSi_NAND::GetIDs(eMMC_CID, ConsoleID);
-
-    Log(LogLevel::Debug, "eMMC CID: "); printhex(eMMC_CID, 16);
-    Log(LogLevel::Debug, "Console ID: %" PRIx64 "\n", ConsoleID);
+    const DSi_NAND::DSiKey& emmccid = NANDImage->GetEMMCID();
+    Log(LogLevel::Debug, "eMMC CID: %08llX%08llX\n", *(const u64*)&emmccid[0], *(const u64*)&emmccid[8]);
+    Log(LogLevel::Debug, "Console ID: %" PRIx64 "\n", NANDImage->GetConsoleID());
 
     if (Platform::GetConfigBool(Platform::DSi_FullBIOSBoot))
     {
@@ -909,10 +914,10 @@ bool LoadNAND()
     else
     {
         u32 eaddr = 0x03FFE6E4;
-        ARM7Write32(eaddr+0x00, *(u32*)&eMMC_CID[0]);
-        ARM7Write32(eaddr+0x04, *(u32*)&eMMC_CID[4]);
-        ARM7Write32(eaddr+0x08, *(u32*)&eMMC_CID[8]);
-        ARM7Write32(eaddr+0x0C, *(u32*)&eMMC_CID[12]);
+        ARM7Write32(eaddr+0x00, *(const u32*)&emmccid[0]);
+        ARM7Write32(eaddr+0x04, *(const u32*)&emmccid[4]);
+        ARM7Write32(eaddr+0x08, *(const u32*)&emmccid[8]);
+        ARM7Write32(eaddr+0x0C, *(const u32*)&emmccid[12]);
         ARM7Write16(eaddr+0x2C, 0x0001);
         ARM7Write16(eaddr+0x2E, 0x0001);
         ARM7Write16(eaddr+0x3C, 0x0100);
@@ -939,9 +944,7 @@ bool LoadNAND()
         NDS::ARM7->JumpTo(bootparams[6]);
     }
 
-    DSi_NAND::PatchUserData();
-
-    DSi_NAND::DeInit();
+    nandmount.PatchUserData();
 
     return true;
 }
@@ -2690,6 +2693,7 @@ void ARM9IOWrite32(u32 addr, u32 val)
 
 u8 ARM7IORead8(u32 addr)
 {
+
     switch (addr)
     {
     case 0x04004000:
@@ -2710,14 +2714,14 @@ u8 ARM7IORead8(u32 addr)
     case 0x04004500: return DSi_I2C::ReadData();
     case 0x04004501: return DSi_I2C::Cnt;
 
-    case 0x04004D00: if (SCFG_BIOS & (1<<10)) return 0; return ConsoleID & 0xFF;
-    case 0x04004D01: if (SCFG_BIOS & (1<<10)) return 0; return (ConsoleID >> 8) & 0xFF;
-    case 0x04004D02: if (SCFG_BIOS & (1<<10)) return 0; return (ConsoleID >> 16) & 0xFF;
-    case 0x04004D03: if (SCFG_BIOS & (1<<10)) return 0; return (ConsoleID >> 24) & 0xFF;
-    case 0x04004D04: if (SCFG_BIOS & (1<<10)) return 0; return (ConsoleID >> 32) & 0xFF;
-    case 0x04004D05: if (SCFG_BIOS & (1<<10)) return 0; return (ConsoleID >> 40) & 0xFF;
-    case 0x04004D06: if (SCFG_BIOS & (1<<10)) return 0; return (ConsoleID >> 48) & 0xFF;
-    case 0x04004D07: if (SCFG_BIOS & (1<<10)) return 0; return ConsoleID >> 56;
+    case 0x04004D00: if (SCFG_BIOS & (1<<10)) return 0; return NANDImage->GetConsoleID() & 0xFF;
+    case 0x04004D01: if (SCFG_BIOS & (1<<10)) return 0; return (NANDImage->GetConsoleID() >> 8) & 0xFF;
+    case 0x04004D02: if (SCFG_BIOS & (1<<10)) return 0; return (NANDImage->GetConsoleID() >> 16) & 0xFF;
+    case 0x04004D03: if (SCFG_BIOS & (1<<10)) return 0; return (NANDImage->GetConsoleID() >> 24) & 0xFF;
+    case 0x04004D04: if (SCFG_BIOS & (1<<10)) return 0; return (NANDImage->GetConsoleID() >> 32) & 0xFF;
+    case 0x04004D05: if (SCFG_BIOS & (1<<10)) return 0; return (NANDImage->GetConsoleID() >> 40) & 0xFF;
+    case 0x04004D06: if (SCFG_BIOS & (1<<10)) return 0; return (NANDImage->GetConsoleID() >> 48) & 0xFF;
+    case 0x04004D07: if (SCFG_BIOS & (1<<10)) return 0; return NANDImage->GetConsoleID() >> 56;
     case 0x04004D08: return 0;
 
     case 0x4004700: return DSi_DSP::SNDExCnt;
@@ -2757,10 +2761,10 @@ u16 ARM7IORead16(u32 addr)
     CASE_READ16_32BIT(0x0400405C, MBK[1][7])
     CASE_READ16_32BIT(0x04004060, MBK[1][8])
 
-    case 0x04004D00: if (SCFG_BIOS & (1<<10)) return 0; return ConsoleID & 0xFFFF;
-    case 0x04004D02: if (SCFG_BIOS & (1<<10)) return 0; return (ConsoleID >> 16) & 0xFFFF;
-    case 0x04004D04: if (SCFG_BIOS & (1<<10)) return 0; return (ConsoleID >> 32) & 0xFFFF;
-    case 0x04004D06: if (SCFG_BIOS & (1<<10)) return 0; return ConsoleID >> 48;
+    case 0x04004D00: if (SCFG_BIOS & (1<<10)) return 0; return NANDImage->GetConsoleID() & 0xFFFF;
+    case 0x04004D02: if (SCFG_BIOS & (1<<10)) return 0; return (NANDImage->GetConsoleID() >> 16) & 0xFFFF;
+    case 0x04004D04: if (SCFG_BIOS & (1<<10)) return 0; return (NANDImage->GetConsoleID() >> 32) & 0xFFFF;
+    case 0x04004D06: if (SCFG_BIOS & (1<<10)) return 0; return NANDImage->GetConsoleID() >> 48;
     case 0x04004D08: return 0;
 
     case 0x4004700: return DSi_DSP::SNDExCnt;
@@ -2836,8 +2840,8 @@ u32 ARM7IORead32(u32 addr)
     case 0x04004400: return DSi_AES::ReadCnt();
     case 0x0400440C: return DSi_AES::ReadOutputFIFO();
 
-    case 0x04004D00: if (SCFG_BIOS & (1<<10)) return 0; return ConsoleID & 0xFFFFFFFF;
-    case 0x04004D04: if (SCFG_BIOS & (1<<10)) return 0; return ConsoleID >> 32;
+    case 0x04004D00: if (SCFG_BIOS & (1<<10)) return 0; return NANDImage->GetConsoleID() & 0xFFFFFFFF;
+    case 0x04004D04: if (SCFG_BIOS & (1<<10)) return 0; return NANDImage->GetConsoleID() >> 32;
     case 0x04004D08: return 0;
 
     case 0x4004700:
diff --git a/src/DSi.h b/src/DSi.h
index 1ea2cca..8822266 100644
--- a/src/DSi.h
+++ b/src/DSi.h
@@ -22,6 +22,11 @@
 #include "NDS.h"
 #include "DSi_SD.h"
 
+namespace DSi_NAND
+{
+    class NANDImage;
+}
+
 namespace DSi
 {
 
@@ -33,9 +38,7 @@ extern u32 SCFG_EXT[2];
 extern u8 ARM9iBIOS[0x10000];
 extern u8 ARM7iBIOS[0x10000];
 
-extern u8 eMMC_CID[16];
-extern u64 ConsoleID;
-
+extern std::unique_ptr<DSi_NAND::NANDImage> NANDImage;
 extern DSi_SDHost* SDMMC;
 extern DSi_SDHost* SDIO;
 
diff --git a/src/DSi_AES.cpp b/src/DSi_AES.cpp
index 5b1fc53..67b84ec 100644
--- a/src/DSi_AES.cpp
+++ b/src/DSi_AES.cpp
@@ -19,6 +19,7 @@
 #include <stdio.h>
 #include <string.h>
 #include "DSi.h"
+#include "DSi_NAND.h"
 #include "DSi_AES.h"
 #include "FIFO.h"
 #include "tiny-AES-c/aes.hpp"
@@ -129,6 +130,7 @@ void Reset()
     OutputMACDue = false;
 
     // initialize keys
+    u64 consoleid = DSi::NANDImage->GetConsoleID();
 
     // slot 0: modcrypt
     *(u32*)&KeyX[0][0] = 0x746E694E;
@@ -137,14 +139,14 @@ void Reset()
     // slot 1: 'Tad'/dev.kp
     *(u32*)&KeyX[1][0] = 0x4E00004A;
     *(u32*)&KeyX[1][4] = 0x4A00004E;
-    *(u32*)&KeyX[1][8] = (u32)(DSi::ConsoleID >> 32) ^ 0xC80C4B72;
-    *(u32*)&KeyX[1][12] = (u32)DSi::ConsoleID;
+    *(u32*)&KeyX[1][8] = (u32)(consoleid >> 32) ^ 0xC80C4B72;
+    *(u32*)&KeyX[1][12] = (u32)consoleid;
 
     // slot 3: console-unique eMMC crypto
-    *(u32*)&KeyX[3][0] = (u32)DSi::ConsoleID;
-    *(u32*)&KeyX[3][4] = (u32)DSi::ConsoleID ^ 0x24EE6906;
-    *(u32*)&KeyX[3][8] = (u32)(DSi::ConsoleID >> 32) ^ 0xE65B601D;
-    *(u32*)&KeyX[3][12] = (u32)(DSi::ConsoleID >> 32);
+    *(u32*)&KeyX[3][0] = (u32)consoleid;
+    *(u32*)&KeyX[3][4] = (u32)consoleid ^ 0x24EE6906;
+    *(u32*)&KeyX[3][8] = (u32)(consoleid >> 32) ^ 0xE65B601D;
+    *(u32*)&KeyX[3][12] = (u32)(consoleid >> 32);
     *(u32*)&KeyY[3][0] = 0x0AB9DC76;
     *(u32*)&KeyY[3][4] = 0xBD4DC4D3;
     *(u32*)&KeyY[3][8] = 0x202DDD1D;
diff --git a/src/DSi_AES.h b/src/DSi_AES.h
index f3aa550..4ee9bdd 100644
--- a/src/DSi_AES.h
+++ b/src/DSi_AES.h
@@ -26,12 +26,12 @@
 #pragma GCC diagnostic ignored "-Wattributes"
 #if defined(__GNUC__) && (__GNUC__ >= 11) // gcc 11.*
 // NOTE: Yes, the compiler does *not* recognize this code pattern, so it is indeed an optimization.
-__attribute((always_inline)) static void Bswap128(void* Dst, void* Src)
+__attribute((always_inline)) static void Bswap128(void* Dst, const void* Src)
 {
     *(__int128*)Dst = __builtin_bswap128(*(__int128*)Src);
 }
 #else
-__attribute((always_inline)) static void Bswap128(void* Dst, void* Src)
+__attribute((always_inline)) static void Bswap128(void* Dst, const void* Src)
 {
     for (int i = 0; i < 16; ++i) 
     { 
diff --git a/src/DSi_NAND.cpp b/src/DSi_NAND.cpp
index 7c3e745..03bed9b 100644
--- a/src/DSi_NAND.cpp
+++ b/src/DSi_NAND.cpp
@@ -22,6 +22,7 @@
 #include "DSi.h"
 #include "DSi_AES.h"
 #include "DSi_NAND.h"
+#include "FATIO.h"
 #include "Platform.h"
 
 #include "sha1/sha1.hpp"
@@ -34,78 +35,16 @@ using namespace Platform;
 namespace DSi_NAND
 {
 
-FileHandle* CurFile;
-FATFS CurFS;
-
-u8 eMMC_CID[16];
-u64 ConsoleID;
-
-u8 FATIV[16];
-u8 FATKey[16];
-
-u8 ESKey[16];
-
-
-UINT FF_ReadNAND(BYTE* buf, LBA_t sector, UINT num);
-UINT FF_WriteNAND(BYTE* buf, LBA_t sector, UINT num);
-
-
-bool Init(u8* es_keyY)
+NANDImage::NANDImage(Platform::FileHandle* nandfile, const DSiKey& es_keyY) noexcept : NANDImage(nandfile, es_keyY.data())
 {
-    CurFile = nullptr;
-
-    std::string nandpath = Platform::GetConfigString(Platform::DSi_NANDPath);
-    std::string instnand = nandpath + Platform::InstanceFileSuffix();
-
-    FileHandle* nandfile = Platform::OpenLocalFile(instnand, FileMode::ReadWriteExisting);
-    if ((!nandfile) && (Platform::InstanceID() > 0))
-    {
-        FileHandle* orig = Platform::OpenLocalFile(nandpath, FileMode::Read);
-        if (!orig)
-        {
-            Log(LogLevel::Error, "Failed to open DSi NAND\n");
-            return false;
-        }
-
-        long len = FileLength(orig);
-
-        nandfile = Platform::OpenLocalFile(instnand, FileMode::ReadWrite);
-        if (nandfile)
-        {
-            u8* tmpbuf = new u8[0x10000];
-            for (long i = 0; i < len; i+=0x10000)
-            {
-                long blklen = 0x10000;
-                if ((i+blklen) > len) blklen = len-i;
-
-                FileRead(tmpbuf, blklen, 1, orig);
-                FileWrite(tmpbuf, blklen, 1, nandfile);
-            }
-            delete[] tmpbuf;
-        }
-
-        Platform::CloseFile(orig);
-        Platform::CloseFile(nandfile);
-
-        nandfile = Platform::OpenLocalFile(instnand, FileMode::ReadWriteExisting);
-    }
+}
 
+NANDImage::NANDImage(Platform::FileHandle* nandfile, const u8* es_keyY) noexcept
+{
     if (!nandfile)
-        return false;
-
-    u64 nandlen = FileLength(nandfile);
-
-    ff_disk_open(FF_ReadNAND, FF_WriteNAND, (LBA_t)(nandlen>>9));
+        return;
 
-    FRESULT res;
-    res = f_mount(&CurFS, "0:", 0);
-    if (res != FR_OK)
-    {
-        Log(LogLevel::Error, "NAND mounting failed: %d\n", res);
-        f_unmount("0:");
-        ff_disk_close();
-        return false;
-    }
+    Length = FileLength(nandfile);
 
     // read the nocash footer
 
@@ -113,26 +52,24 @@ bool Init(u8* es_keyY)
 
     char nand_footer[16];
     const char* nand_footer_ref = "DSi eMMC CID/CPU";
-    FileRead(nand_footer, 1, 16, nandfile);
-    if (memcmp(nand_footer, nand_footer_ref, 16))
+    FileRead(nand_footer, 1, sizeof(nand_footer), nandfile);
+    if (memcmp(nand_footer, nand_footer_ref, sizeof(nand_footer)))
     {
         // There is another copy of the footer at 000FF800h for the case
         // that by external tools the image was cut off
         // See https://problemkaputt.de/gbatek.htm#dsisdmmcimages
         FileSeek(nandfile, 0x000FF800, FileSeekOrigin::Start);
-        FileRead(nand_footer, 1, 16, nandfile);
-        if (memcmp(nand_footer, nand_footer_ref, 16))
+        FileRead(nand_footer, 1, sizeof(nand_footer), nandfile);
+        if (memcmp(nand_footer, nand_footer_ref, sizeof(nand_footer)))
         {
             Log(LogLevel::Error, "ERROR: NAND missing nocash footer\n");
             CloseFile(nandfile);
-            f_unmount("0:");
-            ff_disk_close();
-            return false;
+            return;
         }
     }
 
-    FileRead(eMMC_CID, 1, 16, nandfile);
-    FileRead(&ConsoleID, 1, 8, nandfile);
+    FileRead(eMMC_CID.data(), 1, sizeof(eMMC_CID), nandfile);
+    FileRead(&ConsoleID, 1, sizeof(ConsoleID), nandfile);
 
     // init NAND crypto
 
@@ -141,10 +78,10 @@ bool Init(u8* es_keyY)
     u8 keyX[16], keyY[16];
 
     SHA1Init(&sha);
-    SHA1Update(&sha, eMMC_CID, 16);
+    SHA1Update(&sha, eMMC_CID.data(), sizeof(eMMC_CID));
     SHA1Final(tmp, &sha);
 
-    Bswap128(FATIV, tmp);
+    Bswap128(FATIV.data(), tmp);
 
     *(u32*)&keyX[0] = (u32)ConsoleID;
     *(u32*)&keyX[4] = (u32)ConsoleID ^ 0x24EE6906;
@@ -157,7 +94,7 @@ bool Init(u8* es_keyY)
     *(u32*)&keyY[12] = 0xE1A00005;
 
     DSi_AES::DeriveNormalKey(keyX, keyY, tmp);
-    Bswap128(FATKey, tmp);
+    Bswap128(FATKey.data(), tmp);
 
 
     *(u32*)&keyX[0] = 0x4E00004A;
@@ -165,42 +102,87 @@ bool Init(u8* es_keyY)
     *(u32*)&keyX[8] = (u32)(ConsoleID >> 32) ^ 0xC80C4B72;
     *(u32*)&keyX[12] = (u32)ConsoleID;
 
-    memcpy(keyY, es_keyY, 16);
+    memcpy(keyY, es_keyY, sizeof(keyY));
 
     DSi_AES::DeriveNormalKey(keyX, keyY, tmp);
-    Bswap128(ESKey, tmp);
+    Bswap128(ESKey.data(), tmp);
 
     CurFile = nandfile;
-    return true;
 }
 
-void DeInit()
+NANDImage::~NANDImage()
 {
-    f_unmount("0:");
-    ff_disk_close();
-
     if (CurFile) CloseFile(CurFile);
     CurFile = nullptr;
 }
 
+NANDImage::NANDImage(NANDImage&& other) noexcept :
+    CurFile(other.CurFile),
+    eMMC_CID(other.eMMC_CID),
+    ConsoleID(other.ConsoleID),
+    FATIV(other.FATIV),
+    FATKey(other.FATKey),
+    ESKey(other.ESKey)
+{
+    other.CurFile = nullptr;
+}
+
+NANDImage& NANDImage::operator=(NANDImage&& other) noexcept
+{
+    if (this != &other)
+    {
+        CurFile = other.CurFile;
+        eMMC_CID = other.eMMC_CID;
+        ConsoleID = other.ConsoleID;
+        FATIV = other.FATIV;
+        FATKey = other.FATKey;
+        ESKey = other.ESKey;
+
+        other.CurFile = nullptr;
+    }
+
+    return *this;
+}
 
-FileHandle* GetFile()
+NANDMount::NANDMount(NANDImage& nand) noexcept : Image(&nand)
 {
-    return CurFile;
+    if (!nand)
+        return;
+
+    CurFS = std::make_unique<FATFS>();
+    ff_disk_open(
+        [this](BYTE* buf, LBA_t sector, UINT num) {
+            return this->FF_ReadNAND(buf, sector, num);
+        },
+        [this](const BYTE* buf, LBA_t sector, UINT num) {
+            return this->FF_WriteNAND(buf, sector, num);
+        },
+        (LBA_t)(nand.GetLength()>>9)
+    );
+
+    FRESULT res;
+    res = f_mount(CurFS.get(), "0:", 0);
+    if (res != FR_OK)
+    {
+        Log(LogLevel::Error, "NAND mounting failed: %d\n", res);
+        f_unmount("0:");
+        ff_disk_close();
+        return;
+    }
 }
 
 
-void GetIDs(u8* emmc_cid, u64& consoleid)
+NANDMount::~NANDMount()
 {
-    memcpy(emmc_cid, eMMC_CID, 16);
-    consoleid = ConsoleID;
+    f_unmount("0:");
+    ff_disk_close();
 }
 
 
-void SetupFATCrypto(AES_ctx* ctx, u32 ctr)
+void NANDImage::SetupFATCrypto(AES_ctx* ctx, u32 ctr)
 {
     u8 iv[16];
-    memcpy(iv, FATIV, sizeof(iv));
+    memcpy(iv, FATIV.data(), sizeof(iv));
 
     u32 res;
     res = iv[15] + (ctr & 0xFF);
@@ -218,10 +200,10 @@ void SetupFATCrypto(AES_ctx* ctx, u32 ctr)
         else break;
     }
 
-    AES_init_ctx_iv(ctx, FATKey, iv);
+    AES_init_ctx_iv(ctx, FATKey.data(), iv);
 }
 
-u32 ReadFATBlock(u64 addr, u32 len, u8* buf)
+u32 NANDImage::ReadFATBlock(u64 addr, u32 len, u8* buf)
 {
     u32 ctr = (u32)(addr >> 4);
 
@@ -243,7 +225,7 @@ u32 ReadFATBlock(u64 addr, u32 len, u8* buf)
     return len;
 }
 
-u32 WriteFATBlock(u64 addr, u32 len, u8* buf)
+u32 NANDImage::WriteFATBlock(u64 addr, u32 len, const u8* buf)
 {
     u32 ctr = (u32)(addr >> 4);
 
@@ -272,30 +254,30 @@ u32 WriteFATBlock(u64 addr, u32 len, u8* buf)
 }
 
 
-UINT FF_ReadNAND(BYTE* buf, LBA_t sector, UINT num)
+UINT NANDMount::FF_ReadNAND(BYTE* buf, LBA_t sector, UINT num)
 {
     // TODO: allow selecting other partitions?
     u64 baseaddr = 0x10EE00;
 
     u64 blockaddr = baseaddr + (sector * 0x200ULL);
 
-    u32 res = ReadFATBlock(blockaddr, num*0x200, buf);
+    u32 res = Image->ReadFATBlock(blockaddr, num*0x200, buf);
     return res >> 9;
 }
 
-UINT FF_WriteNAND(BYTE* buf, LBA_t sector, UINT num)
+UINT NANDMount::FF_WriteNAND(const BYTE* buf, LBA_t sector, UINT num)
 {
     // TODO: allow selecting other partitions?
     u64 baseaddr = 0x10EE00;
 
     u64 blockaddr = baseaddr + (sector * 0x200ULL);
 
-    u32 res = WriteFATBlock(blockaddr, num*0x200, buf);
+    u32 res = Image->WriteFATBlock(blockaddr, num*0x200, buf);
     return res >> 9;
 }
 
 
-bool ESEncrypt(u8* data, u32 len)
+bool NANDImage::ESEncrypt(u8* data, u32 len) const
 {
     AES_ctx ctx;
     u8 iv[16];
@@ -307,7 +289,7 @@ bool ESEncrypt(u8* data, u32 len)
     iv[14] = 0x00;
     iv[15] = 0x01;
 
-    AES_init_ctx_iv(&ctx, ESKey, iv);
+    AES_init_ctx_iv(&ctx, ESKey.data(), iv);
 
     u32 blklen = (len + 0xF) & ~0xF;
     mac[0] = 0x3A;
@@ -380,7 +362,7 @@ bool ESEncrypt(u8* data, u32 len)
     return true;
 }
 
-bool ESDecrypt(u8* data, u32 len)
+bool NANDImage::ESDecrypt(u8* data, u32 len)
 {
     AES_ctx ctx;
     u8 iv[16];
@@ -392,7 +374,7 @@ bool ESDecrypt(u8* data, u32 len)
     iv[14] = 0x00;
     iv[15] = 0x01;
 
-    AES_init_ctx_iv(&ctx, ESKey, iv);
+    AES_init_ctx_iv(&ctx, ESKey.data(), iv);
 
     u32 blklen = (len + 0xF) & ~0xF;
     mac[0] = 0x3A;
@@ -486,7 +468,7 @@ bool ESDecrypt(u8* data, u32 len)
 }
 
 
-void ReadHardwareInfo(DSiSerialData& dataS, DSiHardwareInfoN& dataN)
+void NANDMount::ReadHardwareInfo(DSiSerialData& dataS, DSiHardwareInfoN& dataN)
 {
     FF_FIL file;
     FRESULT res;
@@ -508,7 +490,7 @@ void ReadHardwareInfo(DSiSerialData& dataS, DSiHardwareInfoN& dataN)
 }
 
 
-void ReadUserData(DSiFirmwareSystemSettings& data)
+void NANDMount::ReadUserData(DSiFirmwareSystemSettings& data)
 {
     FF_FIL file;
     FRESULT res;
@@ -557,7 +539,7 @@ void ReadUserData(DSiFirmwareSystemSettings& data)
     f_close(&file);
 }
 
-void PatchUserData()
+void NANDMount::PatchUserData()
 {
     FRESULT res;
 
@@ -653,7 +635,7 @@ void debug_listfiles(const char* path)
     f_closedir(&dir);
 }
 
-bool ImportFile(const char* path, const u8* data, size_t len)
+bool NANDMount::ImportFile(const char* path, const u8* data, size_t len)
 {
     if (!data || !len || !path)
         return false;
@@ -687,7 +669,7 @@ bool ImportFile(const char* path, const u8* data, size_t len)
     return true;
 }
 
-bool ImportFile(const char* path, const char* in)
+bool NANDMount::ImportFile(const char* path, const char* in)
 {
     FF_FIL file;
     FILE* fin;
@@ -730,7 +712,7 @@ bool ImportFile(const char* path, const char* in)
     return true;
 }
 
-bool ExportFile(const char* path, const char* out)
+bool NANDMount::ExportFile(const char* path, const char* out)
 {
     FF_FIL file;
     FILE* fout;
@@ -771,7 +753,7 @@ bool ExportFile(const char* path, const char* out)
     return true;
 }
 
-void RemoveFile(const char* path)
+void NANDMount::RemoveFile(const char* path)
 {
     FF_FILINFO info;
     FRESULT res = f_stat(path, &info);
@@ -784,7 +766,7 @@ void RemoveFile(const char* path)
     Log(LogLevel::Debug, "Removed file at %s\n", path);
 }
 
-void RemoveDir(const char* path)
+void NANDMount::RemoveDir(const char* path)
 {
     FF_DIR dir;
     FF_FILINFO info;
@@ -839,7 +821,7 @@ void RemoveDir(const char* path)
 }
 
 
-u32 GetTitleVersion(u32 category, u32 titleid)
+u32 NANDMount::GetTitleVersion(u32 category, u32 titleid)
 {
     FRESULT res;
     char path[256];
@@ -859,7 +841,7 @@ u32 GetTitleVersion(u32 category, u32 titleid)
     return version;
 }
 
-void ListTitles(u32 category, std::vector<u32>& titlelist)
+void NANDMount::ListTitles(u32 category, std::vector<u32>& titlelist)
 {
     FRESULT res;
     FF_DIR titledir;
@@ -908,7 +890,7 @@ void ListTitles(u32 category, std::vector<u32>& titlelist)
     f_closedir(&titledir);
 }
 
-bool TitleExists(u32 category, u32 titleid)
+bool NANDMount::TitleExists(u32 category, u32 titleid)
 {
     char path[256];
     snprintf(path, sizeof(path), "0:/title/%08x/%08x/content/title.tmd", category, titleid);
@@ -917,7 +899,7 @@ bool TitleExists(u32 category, u32 titleid)
     return (res == FR_OK);
 }
 
-void GetTitleInfo(u32 category, u32 titleid, u32& version, NDSHeader* header, NDSBanner* banner)
+void NANDMount::GetTitleInfo(u32 category, u32 titleid, u32& version, NDSHeader* header, NDSBanner* banner)
 {
     version = GetTitleVersion(category, titleid);
     if (version == 0xFFFFFFFF)
@@ -953,7 +935,7 @@ void GetTitleInfo(u32 category, u32 titleid, u32& version, NDSHeader* header, ND
 }
 
 
-bool CreateTicket(const char* path, u32 titleid0, u32 titleid1, u8 version)
+bool NANDMount::CreateTicket(const char* path, u32 titleid0, u32 titleid1, u8 version)
 {
     FF_FIL file;
     FRESULT res;
@@ -979,7 +961,7 @@ bool CreateTicket(const char* path, u32 titleid0, u32 titleid1, u8 version)
 
     memset(&ticket[0x222], 0xFF, 0x20);
 
-    ESEncrypt(ticket, 0x2A4);
+    Image->ESEncrypt(ticket, 0x2A4);
 
     f_write(&file, ticket, 0x2C4, &nwrite);
 
@@ -988,7 +970,7 @@ bool CreateTicket(const char* path, u32 titleid0, u32 titleid1, u8 version)
     return true;
 }
 
-bool CreateSaveFile(const char* path, u32 len)
+bool NANDMount::CreateSaveFile(const char* path, u32 len)
 {
     if (len == 0) return true;
     if (len < 0x200) return false;
@@ -1078,7 +1060,7 @@ bool CreateSaveFile(const char* path, u32 len)
     return true;
 }
 
-bool InitTitleFileStructure(const NDSHeader& header, const DSi_TMD::TitleMetadata& tmd, bool readonly)
+bool NANDMount::InitTitleFileStructure(const NDSHeader& header, const DSi_TMD::TitleMetadata& tmd, bool readonly)
 {
     u32 titleid0 = tmd.GetCategory();
     u32 titleid1 = tmd.GetID();
@@ -1158,7 +1140,7 @@ bool InitTitleFileStructure(const NDSHeader& header, const DSi_TMD::TitleMetadat
     return true;
 }
 
-bool ImportTitle(const char* appfile, const DSi_TMD::TitleMetadata& tmd, bool readonly)
+bool NANDMount::ImportTitle(const char* appfile, const DSi_TMD::TitleMetadata& tmd, bool readonly)
 {
     NDSHeader header {};
     {
@@ -1196,7 +1178,7 @@ bool ImportTitle(const char* appfile, const DSi_TMD::TitleMetadata& tmd, bool re
     return true;
 }
 
-bool ImportTitle(const u8* app, size_t appLength, const DSi_TMD::TitleMetadata& tmd, bool readonly)
+bool NANDMount::ImportTitle(const u8* app, size_t appLength, const DSi_TMD::TitleMetadata& tmd, bool readonly)
 {
     if (!app || appLength < sizeof(NDSHeader))
         return false;
@@ -1232,7 +1214,7 @@ bool ImportTitle(const u8* app, size_t appLength, const DSi_TMD::TitleMetadata&
     return true;
 }
 
-void DeleteTitle(u32 category, u32 titleid)
+void NANDMount::DeleteTitle(u32 category, u32 titleid)
 {
     char fname[128];
 
@@ -1243,7 +1225,7 @@ void DeleteTitle(u32 category, u32 titleid)
     RemoveDir(fname);
 }
 
-u32 GetTitleDataMask(u32 category, u32 titleid)
+u32 NANDMount::GetTitleDataMask(u32 category, u32 titleid)
 {
     u32 version;
     NDSHeader header;
@@ -1260,7 +1242,7 @@ u32 GetTitleDataMask(u32 category, u32 titleid)
     return ret;
 }
 
-bool ImportTitleData(u32 category, u32 titleid, int type, const char* file)
+bool NANDMount::ImportTitleData(u32 category, u32 titleid, int type, const char* file)
 {
     char fname[128];
 
@@ -1286,7 +1268,7 @@ bool ImportTitleData(u32 category, u32 titleid, int type, const char* file)
     return ImportFile(fname, file);
 }
 
-bool ExportTitleData(u32 category, u32 titleid, int type, const char* file)
+bool NANDMount::ExportTitleData(u32 category, u32 titleid, int type, const char* file)
 {
     char fname[128];
 
diff --git a/src/DSi_NAND.h b/src/DSi_NAND.h
index 9bff8f2..777afe0 100644
--- a/src/DSi_NAND.h
+++ b/src/DSi_NAND.h
@@ -20,6 +20,7 @@
 #define DSI_NAND_H
 
 #include "types.h"
+#include "fatfs/ff.h"
 #include "NDS_Header.h"
 #include "DSi_TMD.h"
 #include "SPI_Firmware.h"
@@ -27,6 +28,8 @@
 #include <vector>
 #include <string>
 
+struct AES_ctx;
+
 namespace DSi_NAND
 {
 
@@ -40,29 +43,95 @@ enum
 union DSiFirmwareSystemSettings;
 union DSiSerialData;
 using DSiHardwareInfoN = std::array<u8, 0x9C>;
+using DSiKey = std::array<u8, 16>;
 
-bool Init(u8* es_keyY);
-void DeInit();
-
-Platform::FileHandle* GetFile();
-
-void GetIDs(u8* emmc_cid, u64& consoleid);
-
-void ReadHardwareInfo(DSiSerialData& dataS, DSiHardwareInfoN& dataN);
+class NANDImage
+{
+public:
+    explicit NANDImage(Platform::FileHandle* nandfile, const DSiKey& es_keyY) noexcept;
+    explicit NANDImage(Platform::FileHandle* nandfile, const u8* es_keyY) noexcept;
+    ~NANDImage();
+    NANDImage(const NANDImage&) = delete;
+    NANDImage& operator=(const NANDImage&) = delete;
+
+    NANDImage(NANDImage&& other) noexcept;
+    NANDImage& operator=(NANDImage&& other) noexcept;
+
+    Platform::FileHandle* GetFile() { return CurFile; }
+
+    [[nodiscard]] const DSiKey& GetEMMCID() const noexcept { return eMMC_CID; }
+    [[nodiscard]] u64 GetConsoleID() const noexcept { return ConsoleID; }
+    [[nodiscard]] u64 GetLength() const noexcept { return Length; }
+
+    explicit operator bool() const { return CurFile != nullptr; }
+private:
+    friend class NANDMount;
+    void SetupFATCrypto(AES_ctx* ctx, u32 ctr);
+    u32 ReadFATBlock(u64 addr, u32 len, u8* buf);
+    u32 WriteFATBlock(u64 addr, u32 len, const u8* buf);
+    bool ESEncrypt(u8* data, u32 len) const;
+    bool ESDecrypt(u8* data, u32 len);
+    Platform::FileHandle* CurFile = nullptr;
+    DSiKey eMMC_CID;
+    u64 ConsoleID;
+    DSiKey FATIV;
+    DSiKey FATKey;
+    DSiKey ESKey;
+    u64 Length;
+};
 
-void ReadUserData(DSiFirmwareSystemSettings& data);
-void PatchUserData();
+class NANDMount
+{
+public:
+    explicit NANDMount(NANDImage& nand) noexcept;
+    ~NANDMount();
+    NANDMount(const NANDMount&) = delete;
+    NANDMount& operator=(const NANDMount&) = delete;
+
+    // Move constructor deleted so that the closure passed to FATFS can't be invalidated
+    NANDMount(NANDMount&&) = delete;
+    NANDMount& operator=(NANDMount&&) = delete;
+
+    void ReadHardwareInfo(DSiSerialData& dataS, DSiHardwareInfoN& dataN);
+
+    void ReadUserData(DSiFirmwareSystemSettings& data);
+    void PatchUserData();
+
+    void ListTitles(u32 category, std::vector<u32>& titlelist);
+    bool TitleExists(u32 category, u32 titleid);
+    void GetTitleInfo(u32 category, u32 titleid, u32& version, NDSHeader* header, NDSBanner* banner);
+    bool ImportTitle(const char* appfile, const DSi_TMD::TitleMetadata& tmd, bool readonly);
+    bool ImportTitle(const u8* app, size_t appLength, const DSi_TMD::TitleMetadata& tmd, bool readonly);
+    void DeleteTitle(u32 category, u32 titleid);
+
+    u32 GetTitleDataMask(u32 category, u32 titleid);
+    bool ImportTitleData(u32 category, u32 titleid, int type, const char* file);
+    bool ExportTitleData(u32 category, u32 titleid, int type, const char* file);
+
+    bool ImportFile(const char* path, const u8* data, size_t len);
+    bool ImportFile(const char* path, const char* in);
+    bool ExportFile(const char* path, const char* out);
+    void RemoveFile(const char* path);
+    void RemoveDir(const char* path);
+
+    explicit operator bool() const { return Image != nullptr && CurFS != nullptr; }
+private:
+    u32 GetTitleVersion(u32 category, u32 titleid);
+    bool CreateTicket(const char* path, u32 titleid0, u32 titleid1, u8 version);
+    bool CreateSaveFile(const char* path, u32 len);
+    bool InitTitleFileStructure(const NDSHeader& header, const DSi_TMD::TitleMetadata& tmd, bool readonly);
+    UINT FF_ReadNAND(BYTE* buf, LBA_t sector, UINT num);
+    UINT FF_WriteNAND(const BYTE* buf, LBA_t sector, UINT num);
+
+    NANDImage* Image;
+
+    // We keep a pointer to CurFS because fatfs maintains a global pointer to it;
+    // therefore if we embed the FATFS directly in the object,
+    // we can't give it move semantics.
+    std::unique_ptr<FATFS> CurFS;
 
-void ListTitles(u32 category, std::vector<u32>& titlelist);
-bool TitleExists(u32 category, u32 titleid);
-void GetTitleInfo(u32 category, u32 titleid, u32& version, NDSHeader* header, NDSBanner* banner);
-bool ImportTitle(const char* appfile, const DSi_TMD::TitleMetadata& tmd, bool readonly);
-bool ImportTitle(const u8* app, size_t appLength, const DSi_TMD::TitleMetadata& tmd, bool readonly);
-void DeleteTitle(u32 category, u32 titleid);
+};
 
-u32 GetTitleDataMask(u32 category, u32 titleid);
-bool ImportTitleData(u32 category, u32 titleid, int type, const char* file);
-bool ExportTitleData(u32 category, u32 titleid, int type, const char* file);
 
 typedef std::array<u8, 20> SHA1Hash;
 typedef std::array<u8, 8> TitleID;
diff --git a/src/DSi_SD.cpp b/src/DSi_SD.cpp
index 4f287b1..158ae1e 100644
--- a/src/DSi_SD.cpp
+++ b/src/DSi_SD.cpp
@@ -20,6 +20,7 @@
 #include <string.h>
 #include "DSi.h"
 #include "DSi_SD.h"
+#include "DSi_NAND.h"
 #include "DSi_NWifi.h"
 #include "Platform.h"
 
@@ -137,11 +138,8 @@ void DSi_SDHost::Reset()
         else
             sd = nullptr;
 
-        std::string nandpath = Platform::GetConfigString(Platform::DSi_NANDPath);
-        std::string instnand = nandpath + Platform::InstanceFileSuffix();
-
-        mmc = new DSi_MMCStorage(this, true, instnand);
-        mmc->SetCID(DSi::eMMC_CID);
+        mmc = new DSi_MMCStorage(this, *DSi::NANDImage);
+        mmc->SetCID(DSi::NANDImage->GetEMMCID().data());
 
         Ports[0] = sd;
         Ports[1] = mmc;
@@ -768,14 +766,9 @@ void DSi_SDHost::CheckSwapFIFO()
 
 #define MMC_DESC  (Internal?"NAND":"SDcard")
 
-DSi_MMCStorage::DSi_MMCStorage(DSi_SDHost* host, bool internal, const std::string& filename)
-    : DSi_SDDevice(host)
+DSi_MMCStorage::DSi_MMCStorage(DSi_SDHost* host, DSi_NAND::NANDImage& nand)
+    : DSi_SDDevice(host), Internal(true), NAND(&nand), SD(nullptr)
 {
-    Internal = internal;
-    File = Platform::OpenLocalFile(filename, FileMode::ReadWriteExisting);
-
-    SD = nullptr;
-
     ReadOnly = false;
 }
 
@@ -783,7 +776,7 @@ DSi_MMCStorage::DSi_MMCStorage(DSi_SDHost* host, bool internal, const std::strin
     : DSi_SDDevice(host)
 {
     Internal = internal;
-    File = nullptr;
+    NAND = nullptr;
 
     SD = new FATStorage(filename, size, readonly, sourcedir);
     SD->Open();
@@ -798,10 +791,8 @@ DSi_MMCStorage::~DSi_MMCStorage()
         SD->Close();
         delete SD;
     }
-    if (File)
-    {
-        CloseFile(File);
-    }
+
+    // Do not close the NANDImage, it's not owned by this object
 }
 
 void DSi_MMCStorage::Reset()
@@ -925,7 +916,7 @@ void DSi_MMCStorage::SendCMD(u8 cmd, u32 param)
 
     case 12: // stop operation
         SetState(0x04);
-        if (File) FileFlush(File);
+        if (NAND) FileFlush(NAND->GetFile());
         RWCommand = 0;
         Host->SendResponse(CSR, true);
         return;
@@ -1052,10 +1043,10 @@ u32 DSi_MMCStorage::ReadBlock(u64 addr)
     {
         SD->ReadSectors((u32)(addr >> 9), 1, data);
     }
-    else if (File)
+    else if (NAND)
     {
-        FileSeek(File, addr, FileSeekOrigin::Start);
-        FileRead(&data[addr & 0x1FF], 1, len, File);
+        FileSeek(NAND->GetFile(), addr, FileSeekOrigin::Start);
+        FileRead(&data[addr & 0x1FF], 1, len, NAND->GetFile());
     }
 
     return Host->DataRX(&data[addr & 0x1FF], len);
@@ -1082,10 +1073,10 @@ u32 DSi_MMCStorage::WriteBlock(u64 addr)
             {
                 SD->WriteSectors((u32)(addr >> 9), 1, data);
             }
-            else if (File)
+            else if (NAND)
             {
-                FileSeek(File, addr, FileSeekOrigin::Start);
-                FileWrite(&data[addr & 0x1FF], 1, len, File);
+                FileSeek(NAND->GetFile(), addr, FileSeekOrigin::Start);
+                FileWrite(&data[addr & 0x1FF], 1, len, NAND->GetFile());
             }
         }
     }
diff --git a/src/DSi_SD.h b/src/DSi_SD.h
index fe9e23a..8e53a77 100644
--- a/src/DSi_SD.h
+++ b/src/DSi_SD.h
@@ -24,6 +24,11 @@
 #include "FATStorage.h"
 #include "Savestate.h"
 
+namespace DSi_NAND
+{
+    class NANDImage;
+}
+
 class DSi_SDDevice;
 
 
@@ -125,7 +130,7 @@ protected:
 class DSi_MMCStorage : public DSi_SDDevice
 {
 public:
-    DSi_MMCStorage(DSi_SDHost* host, bool internal, const std::string& filename);
+    DSi_MMCStorage(DSi_SDHost* host, DSi_NAND::NANDImage& nand);
     DSi_MMCStorage(DSi_SDHost* host, bool internal, const std::string& filename, u64 size, bool readonly, const std::string& sourcedir);
     ~DSi_MMCStorage();
 
@@ -133,7 +138,7 @@ public:
 
     void DoSavestate(Savestate* file);
 
-    void SetCID(u8* cid) { memcpy(CID, cid, 16); }
+    void SetCID(const u8* cid) { memcpy(CID, cid, sizeof(CID)); }
 
     void SendCMD(u8 cmd, u32 param);
     void SendACMD(u8 cmd, u32 param);
@@ -142,7 +147,7 @@ public:
 
 private:
     bool Internal;
-    Platform::FileHandle* File;
+    DSi_NAND::NANDImage* NAND;
     FATStorage* SD;
 
     u8 CID[16];
diff --git a/src/fatfs/diskio.c b/src/FATIO.cpp
index 5b5c054..3e91fba 100644
--- a/src/fatfs/diskio.c
+++ b/src/FATIO.cpp
@@ -1,15 +1,24 @@
-/*-----------------------------------------------------------------------*/
-/* Low level disk I/O module SKELETON for FatFs     (C)ChaN, 2019        */
-/*-----------------------------------------------------------------------*/
-/* If a working storage control module is available, it should be        */
-/* attached to the FatFs via a glue function rather than modifying it.   */
-/* This is an example of glue functions to attach various exsisting      */
-/* storage control modules to the FatFs module with a defined API.       */
-/*-----------------------------------------------------------------------*/
+/*
+    Copyright 2016-2023 melonDS team
+
+    This file is part of melonDS.
+
+    melonDS is free software: you can redistribute it and/or modify it under
+    the terms of the GNU General Public License as published by the Free
+    Software Foundation, either version 3 of the License, or (at your option)
+    any later version.
+
+    melonDS is distributed in the hope that it will be useful, but WITHOUT ANY
+    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+    FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 
-#include "ff.h"			/* Obtains integer types */
-#include "diskio.h"		/* Declarations of disk functions */
+    You should have received a copy of the GNU General Public License along
+    with melonDS. If not, see http://www.gnu.org/licenses/.
+*/
 
+#include "FATIO.h"
+#include "fatfs/ff.h"
+#include "fatfs/diskio.h"
 
 static ff_disk_read_cb ReadCb;
 static ff_disk_write_cb WriteCb;
@@ -17,7 +26,7 @@ static LBA_t SectorCount;
 static DSTATUS Status = STA_NOINIT | STA_NODISK;
 
 
-void ff_disk_open(ff_disk_read_cb readcb, ff_disk_write_cb writecb, LBA_t seccnt)
+void ff_disk_open(const ff_disk_read_cb& readcb, const ff_disk_write_cb& writecb, LBA_t seccnt)
 {
     if (!readcb) return;
 
@@ -30,10 +39,10 @@ void ff_disk_open(ff_disk_read_cb readcb, ff_disk_write_cb writecb, LBA_t seccnt
     else          Status &= ~STA_PROTECT;
 }
 
-void ff_disk_close(void)
+void ff_disk_close()
 {
-    ReadCb = (void*)0;
-    WriteCb = (void*)0;
+    ReadCb = nullptr;
+    WriteCb = nullptr;
     SectorCount = 0;
 
     Status &= ~STA_PROTECT;
diff --git a/src/FATIO.h b/src/FATIO.h
new file mode 100644
index 0000000..b3b63f3
--- /dev/null
+++ b/src/FATIO.h
@@ -0,0 +1,34 @@
+/*
+    Copyright 2016-2023 melonDS team
+
+    This file is part of melonDS.
+
+    melonDS is free software: you can redistribute it and/or modify it under
+    the terms of the GNU General Public License as published by the Free
+    Software Foundation, either version 3 of the License, or (at your option)
+    any later version.
+
+    melonDS is distributed in the hope that it will be useful, but WITHOUT ANY
+    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+    FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with melonDS. If not, see http://www.gnu.org/licenses/.
+*/
+
+
+#ifndef FATIO_H
+#define FATIO_H
+
+#include <functional>
+#include "fatfs/ff.h"
+
+// extra additions for interfacing with melonDS
+
+using ff_disk_read_cb = std::function<UINT(BYTE*, LBA_t, UINT)>;
+using ff_disk_write_cb = std::function<UINT(const BYTE*, LBA_t, UINT)>;
+
+void ff_disk_open(const ff_disk_read_cb& readcb, const ff_disk_write_cb& writecb, LBA_t seccnt);
+void ff_disk_close();
+
+#endif // FATIO_H
diff --git a/src/FATStorage.cpp b/src/FATStorage.cpp
index d882f8d..1d8b741 100644
--- a/src/FATStorage.cpp
+++ b/src/FATStorage.cpp
@@ -21,6 +21,7 @@
 #include <inttypes.h>
 #include <vector>
 
+#include "FATIO.h"
 #include "FATStorage.h"
 #include "Platform.h"
 
@@ -122,7 +123,7 @@ UINT FATStorage::FF_ReadStorage(BYTE* buf, LBA_t sector, UINT num)
     return ReadSectorsInternal(FF_File, FF_FileSize, sector, num, buf);
 }
 
-UINT FATStorage::FF_WriteStorage(BYTE* buf, LBA_t sector, UINT num)
+UINT FATStorage::FF_WriteStorage(const BYTE* buf, LBA_t sector, UINT num)
 {
     return WriteSectorsInternal(FF_File, FF_FileSize, sector, num, buf);
 }
@@ -157,7 +158,7 @@ u32 FATStorage::ReadSectorsInternal(FileHandle* file, u64 filelen, u32 start, u3
     return res;
 }
 
-u32 FATStorage::WriteSectorsInternal(FileHandle* file, u64 filelen, u32 start, u32 num, u8* data)
+u32 FATStorage::WriteSectorsInternal(FileHandle* file, u64 filelen, u32 start, u32 num, const u8* data)
 {
     if (!file) return 0;
 
diff --git a/src/FATStorage.h b/src/FATStorage.h
index 6b9beb5..7edad13 100644
--- a/src/FATStorage.h
+++ b/src/FATStorage.h
@@ -55,10 +55,10 @@ private:
     static Platform::FileHandle* FF_File;
     static u64 FF_FileSize;
     static UINT FF_ReadStorage(BYTE* buf, LBA_t sector, UINT num);
-    static UINT FF_WriteStorage(BYTE* buf, LBA_t sector, UINT num);
+    static UINT FF_WriteStorage(const BYTE* buf, LBA_t sector, UINT num);
 
     static u32 ReadSectorsInternal(Platform::FileHandle* file, u64 filelen, u32 start, u32 num, u8* data);
-    static u32 WriteSectorsInternal(Platform::FileHandle* file, u64 filelen, u32 start, u32 num, u8* data);
+    static u32 WriteSectorsInternal(Platform::FileHandle* file, u64 filelen, u32 start, u32 num, const u8* data);
 
     void LoadIndex();
     void SaveIndex();
diff --git a/src/Platform.h b/src/Platform.h
index 9752239..67e6b33 100644
--- a/src/Platform.h
+++ b/src/Platform.h
@@ -107,8 +107,6 @@ enum ConfigEntry
 
     ExternalBIOSEnable,
 
-    DSi_NANDPath,
-
     DLDI_Enable,
     DLDI_ImagePath,
     DLDI_ImageSize,
diff --git a/src/fatfs/ff.h b/src/fatfs/ff.h
index a8c34aa..c2832be 100644
--- a/src/fatfs/ff.h
+++ b/src/fatfs/ff.h
@@ -414,16 +414,6 @@ int ff_del_syncobj (FF_SYNC_t sobj);	/* Delete a sync object */
 #define AM_DIR	0x10	/* Directory */
 #define AM_ARC	0x20	/* Archive */
 
-
-// extra additions for interfacing with melonDS
-
-typedef UINT (*ff_disk_read_cb)(BYTE* buff, LBA_t sector, UINT count);
-typedef UINT (*ff_disk_write_cb)(BYTE* buff, LBA_t sector, UINT count);
-
-void ff_disk_open(ff_disk_read_cb readcb, ff_disk_write_cb writecb, LBA_t seccnt);
-void ff_disk_close(void);
-
-
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/frontend/qt_sdl/Platform.cpp b/src/frontend/qt_sdl/Platform.cpp
index 0574d5d..7f6e1d5 100644
--- a/src/frontend/qt_sdl/Platform.cpp
+++ b/src/frontend/qt_sdl/Platform.cpp
@@ -250,8 +250,6 @@ std::string GetConfigString(ConfigEntry entry)
 {
     switch (entry)
     {
-    case DSi_NANDPath: return Config::DSiNANDPath;
-
     case DLDI_ImagePath: return Config::DLDISDPath;
     case DLDI_FolderPath: return Config::DLDIFolderPath;
 
diff --git a/src/frontend/qt_sdl/ROMManager.cpp b/src/frontend/qt_sdl/ROMManager.cpp
index 49f4c45..206332b 100644
--- a/src/frontend/qt_sdl/ROMManager.cpp
+++ b/src/frontend/qt_sdl/ROMManager.cpp
@@ -595,6 +595,10 @@ void Reset()
     LoadBIOSFiles();
 
     InstallFirmware();
+    if (Config::ConsoleType == 1)
+    {
+        InstallNAND(&DSi::ARM7iBIOS[0x8308]);
+    }
     NDS::Reset();
     SetBatteryLevels();
 
@@ -657,6 +661,9 @@ bool LoadBIOS()
     if (!InstallFirmware())
         return false;
 
+    if (Config::ConsoleType == 1 && !InstallNAND(&DSi::ARM7iBIOS[0x8308]))
+        return false;
+
     if (NDS::NeedsDirectBoot())
         return false;
 
@@ -948,6 +955,47 @@ void LoadUserSettingsFromConfig(SPI_Firmware::Firmware& firmware)
     firmware.UpdateChecksums();
 }
 
+static Platform::FileHandle* OpenNANDFile() noexcept
+{
+    std::string nandpath = Config::DSiNANDPath;
+    std::string instnand = nandpath + Platform::InstanceFileSuffix();
+
+    FileHandle* nandfile = Platform::OpenLocalFile(instnand, FileMode::ReadWriteExisting);
+    if ((!nandfile) && (Platform::InstanceID() > 0))
+    {
+        FileHandle* orig = Platform::OpenLocalFile(nandpath, FileMode::Read);
+        if (!orig)
+        {
+            Log(LogLevel::Error, "Failed to open DSi NAND\n");
+            return nullptr;
+        }
+
+        QFile::copy(QString::fromStdString(nandpath), QString::fromStdString(instnand));
+
+        nandfile = Platform::OpenLocalFile(instnand, FileMode::ReadWriteExisting);
+    }
+
+    return nandfile;
+}
+
+bool InstallNAND(const u8* es_keyY)
+{
+    Platform::FileHandle* nandfile = OpenNANDFile();
+    if (!nandfile)
+        return false;
+
+    if (auto nand = std::make_unique<DSi_NAND::NANDImage>(nandfile, es_keyY); *nand)
+    {
+        DSi::NANDImage = std::move(nand);
+        return true;
+    }
+    else
+    {
+        DSi::NANDImage = nullptr;
+        return false;
+    }
+}
+
 bool InstallFirmware()
 {
     using namespace SPI_Firmware;
@@ -1089,6 +1137,9 @@ bool LoadROM(QStringList filepath, bool reset)
         NDS::SetConsoleType(Config::ConsoleType);
         NDS::EjectCart();
         LoadBIOSFiles();
+        if (Config::ConsoleType == 1)
+            InstallNAND(&DSi::ARM7iBIOS[0x8308]);
+
         NDS::Reset();
         SetBatteryLevels();
     }
diff --git a/src/frontend/qt_sdl/ROMManager.h b/src/frontend/qt_sdl/ROMManager.h
index 5faef1a..2eeed0a 100644
--- a/src/frontend/qt_sdl/ROMManager.h
+++ b/src/frontend/qt_sdl/ROMManager.h
@@ -22,6 +22,7 @@
 #include "types.h"
 #include "SaveManager.h"
 #include "AREngine.h"
+#include "DSi_NAND.h"
 
 #include <string>
 #include <memory>
@@ -40,6 +41,7 @@ bool LoadBIOS();
 void ClearBackupState();
 
 bool InstallFirmware();
+bool InstallNAND(const u8* es_keyY);
 bool LoadROM(QStringList filepath, bool reset);
 void EjectCart();
 bool CartInserted();
diff --git a/src/frontend/qt_sdl/TitleManagerDialog.cpp b/src/frontend/qt_sdl/TitleManagerDialog.cpp
index d5147fc..84bd1ef 100644
--- a/src/frontend/qt_sdl/TitleManagerDialog.cpp
+++ b/src/frontend/qt_sdl/TitleManagerDialog.cpp
@@ -32,13 +32,13 @@
 
 using namespace Platform;
 
-bool TitleManagerDialog::NANDInited = false;
+std::unique_ptr<DSi_NAND::NANDImage> TitleManagerDialog::nand = nullptr;
 TitleManagerDialog* TitleManagerDialog::currentDlg = nullptr;
 
 extern std::string EmuDirectory;
 
 
-TitleManagerDialog::TitleManagerDialog(QWidget* parent) : QDialog(parent), ui(new Ui::TitleManagerDialog)
+TitleManagerDialog::TitleManagerDialog(QWidget* parent, DSi_NAND::NANDImage& image) : QDialog(parent), ui(new Ui::TitleManagerDialog), nandmount(image)
 {
     ui->setupUi(this);
     setAttribute(Qt::WA_DeleteOnClose);
@@ -47,7 +47,7 @@ TitleManagerDialog::TitleManagerDialog(QWidget* parent) : QDialog(parent), ui(ne
 
     const u32 category = 0x00030004;
     std::vector<u32> titlelist;
-    DSi_NAND::ListTitles(category, titlelist);
+    nandmount.ListTitles(category, titlelist);
 
     for (std::vector<u32>::iterator it = titlelist.begin(); it != titlelist.end(); it++)
     {
@@ -109,7 +109,7 @@ void TitleManagerDialog::createTitleItem(u32 category, u32 titleid)
     NDSHeader header;
     NDSBanner banner;
 
-    DSi_NAND::GetTitleInfo(category, titleid, version, &header, &banner);
+    nandmount.GetTitleInfo(category, titleid, version, &header, &banner);
 
     u32 icondata[32*32];
     ROMManager::ROMIcon(banner.Icon, banner.Palette, icondata);
@@ -137,7 +137,7 @@ void TitleManagerDialog::createTitleItem(u32 category, u32 titleid)
 
 bool TitleManagerDialog::openNAND()
 {
-    NANDInited = false;
+    nand = nullptr;
 
     FileHandle* bios7i = Platform::OpenLocalFile(Config::DSiBIOS7Path, FileMode::Read);
     if (!bios7i)
@@ -148,22 +148,25 @@ bool TitleManagerDialog::openNAND()
     FileRead(es_keyY, 16, 1, bios7i);
     CloseFile(bios7i);
 
-    if (!DSi_NAND::Init(es_keyY))
-    {
+    FileHandle* nandfile = Platform::OpenLocalFile(Config::DSiNANDPath, FileMode::ReadWriteExisting);
+    if (!nandfile)
+        return false;
+
+    nand = std::make_unique<DSi_NAND::NANDImage>(nandfile, es_keyY);
+    if (!*nand)
+    { // If loading and mounting the NAND image failed...
+        nand = nullptr;
         return false;
+        // NOTE: The NANDImage takes ownership of the FileHandle,
+        // so it will be closed even if the NANDImage constructor fails.
     }
 
-    NANDInited = true;
     return true;
 }
 
 void TitleManagerDialog::closeNAND()
 {
-    if (NANDInited)
-    {
-        DSi_NAND::DeInit();
-        NANDInited = false;
-    }
+    nand = nullptr;
 }
 
 void TitleManagerDialog::done(int r)
@@ -175,7 +178,7 @@ void TitleManagerDialog::done(int r)
 
 void TitleManagerDialog::on_btnImportTitle_clicked()
 {
-    TitleImportDialog* importdlg = new TitleImportDialog(this, importAppPath, &importTmdData, importReadOnly);
+    TitleImportDialog* importdlg = new TitleImportDialog(this, importAppPath, &importTmdData, importReadOnly, nandmount);
     importdlg->open();
     connect(importdlg, &TitleImportDialog::finished, this, &TitleManagerDialog::onImportTitleFinished);
 
@@ -190,14 +193,16 @@ void TitleManagerDialog::onImportTitleFinished(int res)
     titleid[0] = importTmdData.GetCategory();
     titleid[1] = importTmdData.GetID();
 
+    assert(nand != nullptr);
+    assert(*nand);
     // remove anything that might hinder the install
-    DSi_NAND::DeleteTitle(titleid[0], titleid[1]);
+    nandmount.DeleteTitle(titleid[0], titleid[1]);
 
-    bool importres = DSi_NAND::ImportTitle(importAppPath.toStdString().c_str(), importTmdData, importReadOnly);
+    bool importres = nandmount.ImportTitle(importAppPath.toStdString().c_str(), importTmdData, importReadOnly);
     if (!importres)
     {
         // remove a potential half-completed install
-        DSi_NAND::DeleteTitle(titleid[0], titleid[1]);
+        nandmount.DeleteTitle(titleid[0], titleid[1]);
 
         QMessageBox::critical(this,
                               "Import title - melonDS",
@@ -224,7 +229,7 @@ void TitleManagerDialog::on_btnDeleteTitle_clicked()
         return;
 
     u64 titleid = cur->data(Qt::UserRole).toULongLong();
-    DSi_NAND::DeleteTitle((u32)(titleid >> 32), (u32)titleid);
+    nandmount.DeleteTitle((u32)(titleid >> 32), (u32)titleid);
 
     delete cur;
 }
@@ -317,7 +322,7 @@ void TitleManagerDialog::onImportTitleData()
     }
 
     u64 titleid = cur->data(Qt::UserRole).toULongLong();
-    bool res = DSi_NAND::ImportTitleData((u32)(titleid >> 32), (u32)titleid, type, file.toStdString().c_str());
+    bool res = nandmount.ImportTitleData((u32)(titleid >> 32), (u32)titleid, type, file.toStdString().c_str());
     if (!res)
     {
         QMessageBox::critical(this,
@@ -370,7 +375,7 @@ void TitleManagerDialog::onExportTitleData()
     if (file.isEmpty()) return;
 
     u64 titleid = cur->data(Qt::UserRole).toULongLong();
-    bool res = DSi_NAND::ExportTitleData((u32)(titleid >> 32), (u32)titleid, type, file.toStdString().c_str());
+    bool res = nandmount.ExportTitleData((u32)(titleid >> 32), (u32)titleid, type, file.toStdString().c_str());
     if (!res)
     {
         QMessageBox::critical(this,
@@ -380,8 +385,8 @@ void TitleManagerDialog::onExportTitleData()
 }
 
 
-TitleImportDialog::TitleImportDialog(QWidget* parent, QString& apppath, const DSi_TMD::TitleMetadata* tmd, bool& readonly)
-: QDialog(parent), ui(new Ui::TitleImportDialog), appPath(apppath), tmdData(tmd), readOnly(readonly)
+TitleImportDialog::TitleImportDialog(QWidget* parent, QString& apppath, const DSi_TMD::TitleMetadata* tmd, bool& readonly, DSi_NAND::NANDMount& nandmount)
+: QDialog(parent), ui(new Ui::TitleImportDialog), appPath(apppath), tmdData(tmd), readOnly(readonly), nandmount(nandmount)
 {
     ui->setupUi(this);
     setAttribute(Qt::WA_DeleteOnClose);
@@ -455,7 +460,7 @@ void TitleImportDialog::accept()
         }
     }
 
-    if (DSi_NAND::TitleExists(titleid[1], titleid[0]))
+    if (nandmount.TitleExists(titleid[1], titleid[0]))
     {
         if (QMessageBox::question(this,
                                   "Import title - melonDS",
diff --git a/src/frontend/qt_sdl/TitleManagerDialog.h b/src/frontend/qt_sdl/TitleManagerDialog.h
index fc92fd8..5182e1d 100644
--- a/src/frontend/qt_sdl/TitleManagerDialog.h
+++ b/src/frontend/qt_sdl/TitleManagerDialog.h
@@ -19,6 +19,7 @@
 #ifndef TITLEMANAGERDIALOG_H
 #define TITLEMANAGERDIALOG_H
 
+#include <memory>
 #include <QDialog>
 #include <QMessageBox>
 #include <QListWidget>
@@ -30,6 +31,7 @@
 #include <QNetworkAccessManager>
 
 #include "DSi_TMD.h"
+#include "DSi_NAND.h"
 
 namespace Ui
 {
@@ -44,10 +46,10 @@ class TitleManagerDialog : public QDialog
     Q_OBJECT
 
 public:
-    explicit TitleManagerDialog(QWidget* parent);
+    explicit TitleManagerDialog(QWidget* parent, DSi_NAND::NANDImage& image);
     ~TitleManagerDialog();
 
-    static bool NANDInited;
+    static std::unique_ptr<DSi_NAND::NANDImage> nand;
     static bool openNAND();
     static void closeNAND();
 
@@ -68,7 +70,10 @@ public:
             return nullptr;
         }
 
-        currentDlg = new TitleManagerDialog(parent);
+        assert(nand != nullptr);
+        assert(*nand);
+
+        currentDlg = new TitleManagerDialog(parent, *nand);
         currentDlg->open();
         return currentDlg;
     }
@@ -89,6 +94,7 @@ private slots:
     void onExportTitleData();
 
 private:
+    DSi_NAND::NANDMount nandmount;
     Ui::TitleManagerDialog* ui;
 
     QString importAppPath;
@@ -106,7 +112,7 @@ class TitleImportDialog : public QDialog
     Q_OBJECT
 
 public:
-    explicit TitleImportDialog(QWidget* parent, QString& apppath, const DSi_TMD::TitleMetadata* tmd, bool& readonly);
+    explicit TitleImportDialog(QWidget* parent, QString& apppath, const DSi_TMD::TitleMetadata* tmd, bool& readonly, DSi_NAND::NANDMount& nand);
     ~TitleImportDialog();
 
 private slots:
@@ -119,6 +125,7 @@ private slots:
 
 private:
     Ui::TitleImportDialog* ui;
+    DSi_NAND::NANDMount& nandmount;
 
     QButtonGroup* grpTmdSource;