reactos/ntoskrnl/ke/i386/ldt.c

   1 /*
   2  * COPYRIGHT:       See COPYING in the top level directory
   3  * PROJECT:         ReactOS kernel
   4  * FILE:            ntoskrnl/ke/i386/ldt.c
   5  * PURPOSE:         LDT managment
   6  *
   7  * PROGRAMMERS:     David Welch (welch@cwcom.net)
   8  *                  Stefan Ginsberg (stefan.ginsberg@reactos.org)
   9  */
  10
  11 /* INCLUDES *****************************************************************/
  12
  13 #include <ntoskrnl.h>
  14 #define NDEBUG
  15 #include <debug.h>
  16
  17 /* GLOBALS *******************************************************************/
  18
  19 static KSPIN_LOCK LdtLock;
  20 static KSPIN_LOCK GdtLock;
  21
  22 /* FUNCTIONS *****************************************************************/
  23
  24 NTSTATUS
  25 NTAPI
  26 Ke386GetGdtEntryThread(IN PKTHREAD Thread,
  27                        IN ULONG Offset,
  28                        IN PKGDTENTRY Descriptor)
  29 {
  30     /* Make sure the offset isn't outside the allowed range */
  31     if (Offset >= (KGDT_NUMBER * sizeof(KGDTENTRY)))
  32     {
  33         /* It is, fail */
  34         return STATUS_ACCESS_VIOLATION;
  35     }
  36
  37     /* Check if this is the LDT selector */
  38     if (Offset == KGDT_LDT)
  39     {
  40         /* Get it from the thread's process */
  41         RtlCopyMemory(Descriptor,
  42                       &Thread->Process->LdtDescriptor,
  43                       sizeof(KGDTENTRY));
  44     }
  45     else
  46     {
  47         /* Get the descriptor entry from the GDT */
  48         RtlCopyMemory(Descriptor,
  49                       (PVOID)(((ULONG_PTR)KeGetPcr()->GDT) + Offset),
  50                       sizeof(KGDTENTRY));
  51
  52         /* Check if this is the TEB selector */
  53         if (Offset == KGDT_R3_TEB)
  54         {
  55             /*
  56              * Make sure we set the correct base for this thread. This is per
  57              * process and is set in the GDT on context switch, so it might not
  58              * be correct for the thread specified.
  59              */
  60             Descriptor->BaseLow =
  61                 (USHORT)((ULONG_PTR)(Thread->Teb) & 0xFFFF);
  62             Descriptor->HighWord.Bytes.BaseMid =
  63                 (UCHAR)((ULONG_PTR)(Thread->Teb) >> 16);
  64             Descriptor->HighWord.Bytes.BaseHi =
  65                 (UCHAR)((ULONG_PTR)(Thread->Teb) >> 24);
  66         }
  67     }
  68
  69     /* Success */
  70     return STATUS_SUCCESS;
  71 }
  72
  73 VOID
  74 KeSetBaseGdtSelector(ULONG Entry,
  75                      PVOID Base)
  76 {
  77    KIRQL oldIrql;
  78    PUSHORT Gdt;
  79
  80    DPRINT("KeSetBaseGdtSelector(Entry %x, Base %x)\n",
  81            Entry, Base);
  82
  83    KeAcquireSpinLock(&GdtLock, &oldIrql);
  84
  85    Gdt = (PUSHORT)KeGetPcr()->GDT;
  86    Entry = (Entry & (~0x3)) / 2;
  87
  88    Gdt[Entry + 1] = (USHORT)(((ULONG)Base) & 0xffff);
  89
  90    Gdt[Entry + 2] = Gdt[Entry + 2] & ~(0xff);
  91    Gdt[Entry + 2] = (USHORT)(Gdt[Entry + 2] |
  92      ((((ULONG)Base) & 0xff0000) >> 16));
  93
  94    Gdt[Entry + 3] = Gdt[Entry + 3] & ~(0xff00);
  95    Gdt[Entry + 3] = (USHORT)(Gdt[Entry + 3] |
  96      ((((ULONG)Base) & 0xff000000) >> 16));
  97
  98    DPRINT("%x %x %x %x\n",
  99            Gdt[Entry + 0],
 100            Gdt[Entry + 1],
 101            Gdt[Entry + 2],
 102            Gdt[Entry + 3]);
 103
 104    KeReleaseSpinLock(&GdtLock, oldIrql);
 105 }
 106
 107 VOID
 108 KeSetGdtSelector(ULONG Entry,
 109                  ULONG Value1,
 110                  ULONG Value2)
 111 {
 112    KIRQL oldIrql;
 113    PULONG Gdt;
 114
 115    DPRINT("KeSetGdtSelector(Entry %x, Value1 %x, Value2 %x)\n",
 116            Entry, Value1, Value2);
 117
 118    KeAcquireSpinLock(&GdtLock, &oldIrql);
 119
 120    Gdt = (PULONG) KeGetPcr()->GDT;
 121    Entry = (Entry & (~0x3)) / 4;
 122
 123    Gdt[Entry] = Value1;
 124    Gdt[Entry + 1] = Value2;
 125
 126    DPRINT("%x %x\n",
 127            Gdt[Entry + 0],
 128            Gdt[Entry + 1]);
 129
 130    KeReleaseSpinLock(&GdtLock, oldIrql);
 131 }
 132
 133 BOOLEAN PspIsDescriptorValid(PLDT_ENTRY ldt_entry)
 134 {
 135   ULONG Base, SegLimit;
 136   /*
 137      Allow invalid descriptors.
 138   */
 139   if(!ldt_entry->HighWord.Bits.Type &&
 140      !ldt_entry->HighWord.Bits.Dpl)
 141        return TRUE;
 142
 143   /* eliminate system descriptors and code segments other than
 144      execute and execute/read and DPL<3 descriptors */
 145   if(!(ldt_entry->HighWord.Bits.Type & 0x10) ||
 146      (ldt_entry->HighWord.Bits.Type & 0x8 &&
 147       ldt_entry->HighWord.Bits.Type & 0x4) ||
 148      ldt_entry->HighWord.Bits.Dpl != 3 ||
 149      ldt_entry->HighWord.Bits.Reserved_0) return FALSE;
 150
 151   if(!ldt_entry->HighWord.Bits.Pres) return TRUE;
 152
 153   Base=ldt_entry->BaseLow | (ldt_entry->HighWord.Bytes.BaseMid << 16) |
 154              (ldt_entry->HighWord.Bytes.BaseHi << 24);
 155
 156   SegLimit=ldt_entry->LimitLow |
 157                  (ldt_entry->HighWord.Bits.LimitHi << 16);
 158
 159   if(ldt_entry->HighWord.Bits.Type & 0x4)
 160   {
 161     SegLimit=(ldt_entry->HighWord.Bits.Default_Big) ? -1 : (USHORT)-1;
 162
 163   } else if(ldt_entry->HighWord.Bits.Granularity)
 164   {
 165     SegLimit=(SegLimit << 12) | 0xfff;
 166   }
 167
 168   if ((Base + SegLimit > (ULONG_PTR) MmHighestUserAddress) ||
 169       (Base > Base+SegLimit))
 170   {
 171     DPRINT1("WARNING: Windows would mark this descriptor invalid!");
 172   }
 173
 174   /*
 175      Certain "DOS32" programs expect to be able to create DPMI selectors
 176      that wrap the address space.  Windows NT does not allow user-created
 177      selectors to reach into kernel memory.  However, there is no security
 178      risk in allowing it; the page table will prevent access anyway.
 179   */
 180   return (/*(Base + SegLimit > (ULONG_PTR) MmHighestUserAddress) ||
 181           (Base > Base+SegLimit) ? FALSE : TRUE*/ TRUE);
 182 }
 183
 184 NTSTATUS NTAPI
 185 NtSetLdtEntries (ULONG Selector1,
 186                  LDT_ENTRY LdtEntry1,
 187                  ULONG Selector2,
 188                  LDT_ENTRY LdtEntry2)
 189 {
 190   KIRQL oldIrql;
 191   ULONG NewLdtSize = sizeof(LDT_ENTRY);
 192   PUSHORT LdtDescriptor;
 193   ULONG LdtBase;
 194   ULONG LdtLimit;
 195
 196   if((Selector1 & ~0xffff) || (Selector2 & ~0xffff)) return STATUS_INVALID_LDT_DESCRIPTOR;
 197
 198   Selector1 &= ~0x7;
 199   Selector2 &= ~0x7;
 200
 201   if((Selector1 && !PspIsDescriptorValid(&LdtEntry1)) ||
 202      (Selector2 && !PspIsDescriptorValid(&LdtEntry2))) return STATUS_INVALID_LDT_DESCRIPTOR;
 203   if(!(Selector1 || Selector2)) return STATUS_SUCCESS;
 204
 205   NewLdtSize += (Selector1 >= Selector2) ? Selector1 : Selector2;
 206
 207   KeAcquireSpinLock(&LdtLock, &oldIrql);
 208
 209   LdtDescriptor = (PUSHORT) &PsGetCurrentProcess()->Pcb.LdtDescriptor;
 210   LdtBase = LdtDescriptor[1] |
 211                   ((LdtDescriptor[2] & 0xff) << 16) |
 212                   ((LdtDescriptor[3] & ~0xff) << 16);
 213   LdtLimit = LdtDescriptor[0] |
 214                    ((LdtDescriptor[3] & 0xf) << 16);
 215
 216   if(LdtLimit < (NewLdtSize - 1))
 217   {
 218     /* allocate new ldt, copy old one there, set gdt ldt entry to new
 219        values and load ldtr register and free old ldt */
 220
 221     ULONG NewLdtBase = (ULONG) ExAllocatePool(NonPagedPool,
 222                                               NewLdtSize);
 223
 224     if(!NewLdtBase)
 225     {
 226       KeReleaseSpinLock(&LdtLock, oldIrql);
 227       return STATUS_INSUFFICIENT_RESOURCES;
 228     }
 229
 230     if(LdtBase)
 231     {
 232       memcpy((PVOID) NewLdtBase, (PVOID) LdtBase, LdtLimit+1);
 233     }
 234
 235     LdtDescriptor[0] = (USHORT)((--NewLdtSize) & 0xffff);
 236     LdtDescriptor[1] = (USHORT)(NewLdtBase & 0xffff);
 237     LdtDescriptor[2] = (USHORT)(((NewLdtBase & 0xff0000) >> 16) | 0x8200);
 238     LdtDescriptor[3] = (USHORT)(((NewLdtSize & 0xf0000) >> 16) |
 239                                 ((NewLdtBase & 0xff000000) >> 16));
 240
 241     KeSetGdtSelector(KGDT_LDT,
 242                      ((PULONG) LdtDescriptor)[0],
 243                      ((PULONG) LdtDescriptor)[1]);
 244
 245     Ke386SetLocalDescriptorTable(KGDT_LDT);
 246
 247     if(LdtBase)
 248     {
 249       ExFreePool((PVOID) LdtBase);
 250     }
 251
 252     LdtBase = NewLdtBase;
 253   }
 254
 255   if(Selector1)
 256   {
 257     memcpy((char*)LdtBase + Selector1,
 258            &LdtEntry1,
 259            sizeof(LDT_ENTRY));
 260   }
 261
 262   if(Selector2)
 263   {
 264     memcpy((char*)LdtBase + Selector2,
 265            &LdtEntry2,
 266            sizeof(LDT_ENTRY));
 267   }
 268
 269   KeReleaseSpinLock(&LdtLock, oldIrql);
 270   return STATUS_SUCCESS;
 271 }
 272
 273