From 12e9ca82d122e70c10906b62ea489e61883241cc Mon Sep 17 00:00:00 2001
From: d0k3 <tore.anon@gmail.com>
Date: Wed, 22 Feb 2017 17:41:18 +0100
Subject: [PATCH] Include essential.exefs file in virtual NAND (if available)

---
 source/nand/essentials.h |  7 ++++++-
 source/virtual/vnand.c   | 14 ++++++++++++--
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/source/nand/essentials.h b/source/nand/essentials.h
index b265c3a..a61a674 100644
--- a/source/nand/essentials.h
+++ b/source/nand/essentials.h
@@ -3,7 +3,12 @@
 #include "common.h"
 #include "exefs.h"
 
-#define ESSENTIAL_SECTOR 0x1 // start sector of the essential backup in NAND
+// start sector of the essential backup in NAND
+// careful with this, essential backup should never reach sector 0x96
+#define ESSENTIAL_SECTOR 0x1
+
+// magic number for essential backup
+#define ESSENTIAL_MAGIC 'n', 'a', 'n', 'd', '_', 'h', 'd', 'r', 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00
 
 // /rw/sys/LocalFriendCodeSeed_B (/_A) file
 // see: http://3dbrew.org/wiki/Nandrw/sys/LocalFriendCodeSeed_B
diff --git a/source/virtual/vnand.c b/source/virtual/vnand.c
index 658baee..bf8b191 100644
--- a/source/virtual/vnand.c
+++ b/source/virtual/vnand.c
@@ -1,12 +1,14 @@
 #include "vnand.h"
 #include "nand.h"
 #include "agbsave.h"
+#include "essentials.h"
 #include "platform.h"
 
 #define VFLAG_ON_O3DS       NAND_TYPE_O3DS
 #define VFLAG_ON_N3DS       NAND_TYPE_N3DS
 #define VFLAG_ON_NO3DS      NAND_TYPE_NO3DS
 #define VFLAG_ON_NAND       (VFLAG_ON_O3DS | VFLAG_ON_N3DS | VFLAG_ON_NO3DS)
+#define VFLAG_ESSENTIAL     (1UL<<28)
 #define VFLAG_GBA_VC        (1UL<<29)
 #define VFLAG_NEEDS_OTP     (1UL<<30)
 #define VFLAG_NAND_SIZE     (1UL<<31)
@@ -32,8 +34,9 @@ static const VirtualFile vNandFileTemplates[] = {
     { "nand_hdr.bin"     , 0x00000000, 0x00000200, 0xFF, VFLAG_ON_NAND },
     { "twlmbr.bin"       , 0x000001BE, 0x00000042, 0x03, VFLAG_ON_NAND },
     { "free0x01.bin"     , 0x00000200, 0x00012A00, 0xFF, VFLAG_ON_NAND },
-    { "free0x1D7800.bin" , 0x3AF00000, 0x00000000, 0xFF, VFLAG_ON_O3DS | VFLAG_NAND_SIZE },
-    { "free0x26C000.bin" , 0x4D800000, 0x00000000, 0xFF, VFLAG_ON_N3DS | VFLAG_ON_NO3DS | VFLAG_NAND_SIZE },
+    { "essential.exefs"  , 0x00000200, 0x00000000, 0xFF, VFLAG_ON_NAND | VFLAG_ESSENTIAL },
+    { "bonus0x1D7800.bin", 0x3AF00000, 0x00000000, 0xFF, VFLAG_ON_O3DS | VFLAG_NAND_SIZE },
+    { "bonus0x26C000.bin", 0x4D800000, 0x00000000, 0xFF, VFLAG_ON_N3DS | VFLAG_ON_NO3DS | VFLAG_NAND_SIZE },
     { "gbavc.sav"        , 0x0B100200, 0x00000000, 0x07, VFLAG_ON_NAND | VFLAG_GBA_VC },
 };
 
@@ -75,6 +78,13 @@ bool ReadVNandDir(VirtualFile* vfile, VirtualDir* vdir) { // uses a generic vdir
             if (nand_size <= vfile->offset) continue;
             vfile->size = nand_size - vfile->offset;
         }
+        if (vfile->flags & VFLAG_ESSENTIAL) {
+            const u8 magic[] = { ESSENTIAL_MAGIC };
+            u8 data[sizeof(magic)];
+            ReadNandBytes(data, vfile->offset, sizeof(magic), vfile->keyslot, nand_src);
+            if (memcmp(data, magic, sizeof(magic)) != 0) continue;
+            vfile->size = sizeof(EssentialBackup);
+        }
         if (vfile->flags & VFLAG_GBA_VC) {
             if (CheckAgbSaveCmac(nand_src) != 0) continue;
             vfile->size = GetAgbSaveSize(nand_src);