reactos/boot/freeldr/freeldr/disk/ramdisk.c

   1 /*
   2  * PROJECT:         ReactOS Boot Loader
   3  * LICENSE:         BSD - See COPYING.ARM in the top level directory
   4  * FILE:            boot/freeldr/arch/i386/ramdisk.c
   5  * PURPOSE:         Implements routines to support booting from a RAM Disk
   6  * PROGRAMMERS:     ReactOS Portable Systems Group
   7  */
   8
   9 /* INCLUDES *******************************************************************/
  10
  11 #include <freeldr.h>
  12 #define NDEBUG
  13 #include <debug.h>
  14
  15 /* GLOBALS ********************************************************************/
  16
  17 PVOID gRamDiskBase;
  18 ULONG gRamDiskSize;
  19 extern BOOLEAN gCacheEnabled;
  20
  21 /* FUNCTIONS ******************************************************************/
  22
  23 FORCEINLINE
  24 PVOID
  25 RamDiskGetDataAtOffset(IN PVOID Offset)
  26 {
  27     //
  28     // Return data from our RAM Disk
  29     //
  30     assert(((ULONG_PTR)gRamDiskBase + (ULONG_PTR)Offset) <
  31            ((ULONG_PTR)gRamDiskBase + (ULONG_PTR)gRamDiskSize));
  32     return (PVOID)((ULONG_PTR)gRamDiskBase + (ULONG_PTR)(Offset));
  33 }
  34
  35 ULONG
  36 RamDiskGetCacheableBlockCount(IN ULONG Reserved)
  37 {
  38     //
  39     // Allow 32KB transfers (64 sectors), emulating BIOS LBA
  40     //
  41     ASSERT(Reserved == 0x49);
  42     return 64;
  43 }
  44
  45 BOOLEAN
  46 RamDiskGetDriveGeometry(IN ULONG Reserved,
  47                         OUT PGEOMETRY Geometry)
  48 {
  49     //
  50     // Should never be called when the caller expects valid Geometry!
  51     //
  52     ASSERT(Reserved == 0x49);
  53     return TRUE;
  54 }
  55
  56 BOOLEAN
  57 RamDiskReadLogicalSectors(IN ULONG Reserved,
  58                           IN ULONGLONG SectorNumber,
  59                           IN ULONG SectorCount,
  60                           IN PVOID Buffer)
  61 {
  62     PVOID StartAddress;
  63     ULONG Length;
  64     ASSERT(Reserved == 0x49);
  65
  66     //
  67     // Get actual pointers and lengths
  68     //
  69     StartAddress = (PVOID)((ULONG)SectorNumber * 512);
  70     Length = SectorCount * 512;
  71
  72     //
  73     // Don't allow reads past our image
  74     //
  75     if (((ULONG_PTR)StartAddress + Length) > gRamDiskSize) return FALSE;
  76
  77     //
  78     // Do the read
  79     //
  80     RtlCopyMemory(Buffer, RamDiskGetDataAtOffset(StartAddress), Length);
  81     return TRUE;
  82 }
  83
  84 VOID
  85 NTAPI
  86 RamDiskCheckForVirtualFile(VOID)
  87 {
  88     PFILE RamFile;
  89     ULONG TotalRead, ChunkSize;
  90
  91     //
  92     // Try opening the ramdisk file (this assumes the boot volume was opened)
  93     //
  94     RamFile = FsOpenFile("reactos.img");
  95     if (RamFile)
  96     {
  97         //
  98         // Get the file size
  99         //
 100         gRamDiskSize = FsGetFileSize(RamFile);
 101         TuiPrintf("Found virtual ramdisk (%dKB)\n", gRamDiskSize / 1024);
 102         if (!gRamDiskSize) return;
 103
 104         //
 105         // Allocate memory for it
 106         //
 107         ChunkSize = 8 * 1024 * 1024;
 108         gRamDiskBase = MmAllocateMemory(gRamDiskSize);
 109         if (!gRamDiskBase) return;
 110
 111         //
 112         // Read it in chunks
 113         //
 114         TuiPrintf("Loading ramdisk @ 0x%x...", gRamDiskBase);
 115         for (TotalRead = 0; TotalRead < gRamDiskSize; TotalRead += ChunkSize)
 116         {
 117             //
 118             // Check if we're at the last chunk
 119             //
 120             if ((gRamDiskSize - TotalRead) < ChunkSize)
 121             {
 122                 //
 123                 // Only need the actual data required
 124                 //
 125                 ChunkSize = gRamDiskSize - TotalRead;
 126             }
 127
 128             //
 129             // Copy the contents
 130             //
 131             TuiPrintf(".");
 132             if (!FsReadFile(RamFile,
 133                             ChunkSize,
 134                             NULL,
 135                             (PVOID)((ULONG_PTR)gRamDiskBase + TotalRead)))
 136             {
 137                 //
 138                 // Fail
 139                 //
 140                 TuiPrintf("Failed to read ramdisk\n");
 141             }
 142         }
 143         TuiPrintf("\n");
 144     }
 145 }
 146
 147 VOID
 148 NTAPI
 149 RamDiskSwitchFromBios(VOID)
 150 {
 151     extern ULONG BootDrive, BootPartition;
 152
 153     //
 154     // Check if we have a ramdisk, in which case we need to switch routines
 155     //
 156     if (gRamDiskBase)
 157     {
 158         //
 159         // Don't use the BIOS for reads anymore
 160         //
 161         MachVtbl.DiskReadLogicalSectors = RamDiskReadLogicalSectors;
 162         MachVtbl.DiskGetDriveGeometry = RamDiskGetDriveGeometry;
 163         MachVtbl.DiskGetCacheableBlockCount = RamDiskGetCacheableBlockCount;
 164
 165         //
 166         // Also disable cached FAT reads
 167         //
 168         gCacheEnabled = FALSE;
 169
 170         //
 171         // Switch to ramdisk boot partition
 172         //
 173         BootDrive = 0x49;
 174         BootPartition = 0;
 175     }
 176 }