Implemented support for out-of-bounds rom reads. Fixes #138, fixes #113

Gericom · Apr 7, 2024 · d1efd9b · d1efd9b
1 parent 2f0609f
commit d1efd9b
Showing 1 changed file with 44 additions and 14 deletions.
diff --git a/code/core/arm9/source/SdCache/SdCache.c b/code/core/arm9/source/SdCache/SdCache.c
@@ -1,4 +1,5 @@
 #include "common.h"
+#include <string.h>
 #include "Fat/ff.h"
 #include "Fat/diskio.h"
 #include "Fat/FsIpc.h"
@@ -93,16 +94,35 @@ static u32 getSdSectorOfRomBlock(u32 romBlock)
     return sector;
 }
 
+static void fillOutOfBoundsCacheBlock(u32 romBlock, u32 cacheBlock)
+{
+    u32 romSize = f_size(&gFile);
+    u32 powerOf2RomSize = romSize < 0x100000 ? 0x100000 : (1 << (32 - __builtin_clz(romSize - 1)));
+    if (romBlock * SDC_BLOCK_SIZE < powerOf2RomSize)
+    {
+        memset(&sdc_cache[cacheBlock][0], 0xFF, SDC_BLOCK_SIZE);
+    }
+    else
+    {
+        for (u32 i = 0; i < SDC_BLOCK_SIZE; i += 4)
+        {
+            u32 address = romBlock * SDC_BLOCK_SIZE + i;
+            u32 oobValue = (address >> 1) & 0xFFFF;
+            *(u32 *)&sdc_cache[cacheBlock][i] = oobValue | ((oobValue + 1) << 16);
+        }
+    }
+
+    sCacheBlockToRomBlock[cacheBlock] = romBlock;
+    sdc_romBlockToCacheBlock[romBlock] = &sdc_cache[cacheBlock][0];
+    dc_drainWriteBuffer();
+}
+
 /// @brief Loads a rom block to the given buffer.
 /// @param romBlock Rom block index to load.
 /// @param dst The destination buffer.
 static void* loadRomBlock(u32 romBlock, u32 cacheBlock)
 {
     u32 sector = getSdSectorOfRomBlock(romBlock);
-    if (sector == 0)
-    {
-        return &sdc_cache[0][0];
-    }
 
     u32 irqs = fs_waitForCompletionOfCurrentTransaction(true);
     if (isCurrentlyFetching())
@@ -148,26 +168,36 @@ static void* loadRomBlock(u32 romBlock, u32 cacheBlock)
     }
 
     FsWaitToken waitToken;
-    fs_readCacheAlignedSectorsAsync(
-        gFile.obj.fs->pdrv == DEV_FAT ? FS_DEVICE_DLDI : FS_DEVICE_DSI_SD,
-        &sdc_cache[cacheBlock][0], sector,
-        SDC_BLOCK_SIZE / 512, &waitToken);
-    sCurrentFetch.romBlock = romBlock;
-    sCurrentFetch.cacheBlock = cacheBlock;
+    if (sector != 0)
+    {
+        fs_readCacheAlignedSectorsAsync(
+            gFile.obj.fs->pdrv == DEV_FAT ? FS_DEVICE_DLDI : FS_DEVICE_DSI_SD,
+            &sdc_cache[cacheBlock][0], sector,
+            SDC_BLOCK_SIZE / 512, &waitToken);
+        sCurrentFetch.romBlock = romBlock;
+        sCurrentFetch.cacheBlock = cacheBlock;
+    }
 
     if ((arm_getCpsr() & 0x1F) != 0x12)
     {
         sTabuBlock = cacheBlock;
     }
 
     arm_restoreIrqs(irqs);
-    irqs = fs_waitForCompletion(&waitToken, true);
-    if (sCurrentFetch.romBlock == romBlock)
+    if (sector != 0)
     {
-        finishFetch();
+        irqs = fs_waitForCompletion(&waitToken, true);
+        if (sCurrentFetch.romBlock == romBlock)
+        {
+            finishFetch();
+        }
+        arm_restoreIrqs(irqs);
+    }
+    else
+    {
+        fillOutOfBoundsCacheBlock(romBlock, cacheBlock);
     }
 
-    arm_restoreIrqs(irqs);
     return &sdc_cache[cacheBlock][0];
 }