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 %p)\n", Entry, Base);
  81
  82    KeAcquireSpinLock(&GdtLock, &oldIrql);
  83
  84    Gdt = (PUSHORT)KeGetPcr()->GDT;
  85    Entry = (Entry & (~0x3)) / 2;
  86
  87    Gdt[Entry + 1] = (USHORT)(((ULONG)Base) & 0xffff);
  88
  89    Gdt[Entry + 2] = Gdt[Entry + 2] & ~(0xff);
  90    Gdt[Entry + 2] = (USHORT)(Gdt[Entry + 2] |
  91      ((((ULONG)Base) & 0xff0000) >> 16));
  92
  93    Gdt[Entry + 3] = Gdt[Entry + 3] & ~(0xff00);
  94    Gdt[Entry + 3] = (USHORT)(Gdt[Entry + 3] |
  95      ((((ULONG)Base) & 0xff000000) >> 16));
  96
  97    DPRINT("%x %x %x %x\n",
  98            Gdt[Entry + 0],
  99            Gdt[Entry + 1],
 100            Gdt[Entry + 2],
 101            Gdt[Entry + 3]);
 102
 103    KeReleaseSpinLock(&GdtLock, oldIrql);
 104 }
 105
 106 VOID
 107 KeSetGdtSelector(ULONG Entry,
 108                  ULONG Value1,
 109                  ULONG Value2)
 110 {
 111    KIRQL oldIrql;
 112    PULONG Gdt;
 113
 114    DPRINT("KeSetGdtSelector(Entry %x, Value1 %x, Value2 %x)\n",
 115            Entry, Value1, Value2);
 116
 117    KeAcquireSpinLock(&GdtLock, &oldIrql);
 118
 119    Gdt = (PULONG) KeGetPcr()->GDT;
 120    Entry = (Entry & (~0x3)) / 4;
 121
 122    Gdt[Entry] = Value1;
 123    Gdt[Entry + 1] = Value2;
 124
 125    DPRINT("%x %x\n",
 126            Gdt[Entry + 0],
 127            Gdt[Entry + 1]);
 128
 129    KeReleaseSpinLock(&GdtLock, oldIrql);
 130 }
 131
 132 BOOLEAN PspIsDescriptorValid(PLDT_ENTRY ldt_entry)
 133 {
 134   ULONG Base, SegLimit;
 135   /*
 136      Allow invalid descriptors.
 137   */
 138   if(!ldt_entry->HighWord.Bits.Type &&
 139      !ldt_entry->HighWord.Bits.Dpl)
 140        return TRUE;
 141
 142   /* eliminate system descriptors and code segments other than
 143      execute and execute/read and DPL<3 descriptors */
 144   if(!(ldt_entry->HighWord.Bits.Type & 0x10) ||
 145      (ldt_entry->HighWord.Bits.Type & 0x8 &&
 146       ldt_entry->HighWord.Bits.Type & 0x4) ||
 147      ldt_entry->HighWord.Bits.Dpl != 3 ||
 148      ldt_entry->HighWord.Bits.Reserved_0) return FALSE;
 149
 150   if(!ldt_entry->HighWord.Bits.Pres) return TRUE;
 151
 152   Base=ldt_entry->BaseLow | (ldt_entry->HighWord.Bytes.BaseMid << 16) |
 153              (ldt_entry->HighWord.Bytes.BaseHi << 24);
 154
 155   SegLimit=ldt_entry->LimitLow |
 156                  (ldt_entry->HighWord.Bits.LimitHi << 16);
 157
 158   if(ldt_entry->HighWord.Bits.Type & 0x4)
 159   {
 160     SegLimit=(ldt_entry->HighWord.Bits.Default_Big) ? -1 : (USHORT)-1;
 161
 162   } else if(ldt_entry->HighWord.Bits.Granularity)
 163   {
 164     SegLimit=(SegLimit << 12) | 0xfff;
 165   }
 166
 167   if ((Base + SegLimit > (ULONG_PTR) MmHighestUserAddress) ||
 168       (Base > Base+SegLimit))
 169   {
 170     DPRINT1("WARNING: Windows would mark this descriptor invalid!");
 171   }
 172
 173   /*
 174      Certain "DOS32" programs expect to be able to create DPMI selectors
 175      that wrap the address space.  Windows NT does not allow user-created
 176      selectors to reach into kernel memory.  However, there is no security
 177      risk in allowing it; the page table will prevent access anyway.
 178   */
 179   return (/*(Base + SegLimit > (ULONG_PTR) MmHighestUserAddress) ||
 180           (Base > Base+SegLimit) ? FALSE : TRUE*/ TRUE);
 181 }
 182
 183 NTSTATUS NTAPI
 184 NtSetLdtEntries (ULONG Selector1,
 185                  LDT_ENTRY LdtEntry1,
 186                  ULONG Selector2,
 187                  LDT_ENTRY LdtEntry2)
 188 {
 189   KIRQL oldIrql;
 190   ULONG NewLdtSize = sizeof(LDT_ENTRY);
 191   PUSHORT LdtDescriptor;
 192   ULONG LdtBase;
 193   ULONG LdtLimit;
 194
 195   if((Selector1 & ~0xffff) || (Selector2 & ~0xffff)) return STATUS_INVALID_LDT_DESCRIPTOR;
 196
 197   Selector1 &= ~0x7;
 198   Selector2 &= ~0x7;
 199
 200   if((Selector1 && !PspIsDescriptorValid(&LdtEntry1)) ||
 201      (Selector2 && !PspIsDescriptorValid(&LdtEntry2))) return STATUS_INVALID_LDT_DESCRIPTOR;
 202   if(!(Selector1 || Selector2)) return STATUS_SUCCESS;
 203
 204   NewLdtSize += (Selector1 >= Selector2) ? Selector1 : Selector2;
 205
 206   KeAcquireSpinLock(&LdtLock, &oldIrql);
 207
 208   LdtDescriptor = (PUSHORT) &PsGetCurrentProcess()->Pcb.LdtDescriptor;
 209   LdtBase = LdtDescriptor[1] |
 210                   ((LdtDescriptor[2] & 0xff) << 16) |
 211                   ((LdtDescriptor[3] & ~0xff) << 16);
 212   LdtLimit = LdtDescriptor[0] |
 213                    ((LdtDescriptor[3] & 0xf) << 16);
 214
 215   if(LdtLimit < (NewLdtSize - 1))
 216   {
 217     /* allocate new ldt, copy old one there, set gdt ldt entry to new
 218        values and load ldtr register and free old ldt */
 219
 220     ULONG NewLdtBase = (ULONG) ExAllocatePool(NonPagedPool,
 221                                               NewLdtSize);
 222
 223     if(!NewLdtBase)
 224     {
 225       KeReleaseSpinLock(&LdtLock, oldIrql);
 226       return STATUS_INSUFFICIENT_RESOURCES;
 227     }
 228
 229     if(LdtBase)
 230     {
 231       memcpy((PVOID) NewLdtBase, (PVOID) LdtBase, LdtLimit+1);
 232     }
 233
 234     LdtDescriptor[0] = (USHORT)((--NewLdtSize) & 0xffff);
 235     LdtDescriptor[1] = (USHORT)(NewLdtBase & 0xffff);
 236     LdtDescriptor[2] = (USHORT)(((NewLdtBase & 0xff0000) >> 16) | 0x8200);
 237     LdtDescriptor[3] = (USHORT)(((NewLdtSize & 0xf0000) >> 16) |
 238                                 ((NewLdtBase & 0xff000000) >> 16));
 239
 240     KeSetGdtSelector(KGDT_LDT,
 241                      ((PULONG) LdtDescriptor)[0],
 242                      ((PULONG) LdtDescriptor)[1]);
 243
 244     Ke386SetLocalDescriptorTable(KGDT_LDT);
 245
 246     if(LdtBase)
 247     {
 248       ExFreePool((PVOID) LdtBase);
 249     }
 250
 251     LdtBase = NewLdtBase;
 252   }
 253
 254   if(Selector1)
 255   {
 256     memcpy((char*)LdtBase + Selector1,
 257            &LdtEntry1,
 258            sizeof(LDT_ENTRY));
 259   }
 260
 261   if(Selector2)
 262   {
 263     memcpy((char*)LdtBase + Selector2,
 264            &LdtEntry2,
 265            sizeof(LDT_ENTRY));
 266   }
 267
 268   KeReleaseSpinLock(&LdtLock, oldIrql);
 269   return STATUS_SUCCESS;
 270 }
 271
 272