FAST486_TSS Tss;
USHORT OldSs = State->SegmentRegs[FAST486_REG_SS].Selector;
ULONG OldEsp = State->GeneralRegs[FAST486_REG_ESP].Long;
+
+ if (GateType == FAST486_TASK_GATE_SIGNATURE)
+ {
+ /* Task call */
+ return Fast486TaskSwitch(State, FAST486_TASK_CALL, IdtEntry->Selector);
+ }
if (GateSize != (State->SegmentRegs[FAST486_REG_CS].Size))
{
State->ExceptionCount = 0;
}
+BOOLEAN
+FASTCALL
+Fast486TaskSwitch(PFAST486_STATE State, FAST486_TASK_SWITCH_TYPE Type, USHORT Selector)
+{
+ ULONG NewTssAddress;
+ ULONG NewTssLimit;
+ FAST486_TSS OldTss;
+ FAST486_TSS NewTss;
+ FAST486_SYSTEM_DESCRIPTOR NewTssDescriptor;
+
+ /* Read the old TSS */
+ if (!Fast486ReadLinearMemory(State,
+ State->TaskReg.Base,
+ &OldTss,
+ sizeof(OldTss)))
+ {
+ /* Exception occurred */
+ return FALSE;
+ }
+
+ /* If this is a task return, use the linked previous selector */
+ if (Type == FAST486_TASK_RETURN) Selector = LOWORD(OldTss.Link);
+
+ /* Make sure the entry exists in the GDT (not LDT!) */
+ if ((GET_SEGMENT_INDEX(Selector) == 0)
+ || (Selector & SEGMENT_TABLE_INDICATOR)
+ || GET_SEGMENT_INDEX(Selector) >= (State->Gdtr.Size + 1))
+ {
+ Fast486ExceptionWithErrorCode(State, FAST486_EXCEPTION_TS, Selector);
+ return FALSE;
+ }
+
+ /* Get the TSS descriptor from the GDT */
+ if (!Fast486ReadLinearMemory(State,
+ State->Gdtr.Address + GET_SEGMENT_INDEX(Selector),
+ &NewTssDescriptor,
+ sizeof(NewTssDescriptor)))
+ {
+ /* Exception occurred */
+ return FALSE;
+ }
+
+ if (!NewTssDescriptor.Present)
+ {
+ /* Incoming task TSS not present */
+ Fast486ExceptionWithErrorCode(State, FAST486_EXCEPTION_NP, Selector);
+ return FALSE;
+ }
+
+ /* Calculate the linear address of the new TSS */
+ NewTssAddress = NewTssDescriptor.Base;
+ NewTssAddress |= NewTssDescriptor.BaseMid << 16;
+ NewTssAddress |= NewTssDescriptor.BaseHigh << 24;
+
+ /* Calculate the limit of the new TSS */
+ NewTssLimit = NewTssDescriptor.Limit | (NewTssDescriptor.LimitHigh << 16);
+ if (NewTssDescriptor.Granularity) NewTssLimit <<= 12;
+
+ if (NewTssLimit < sizeof(FAST486_TSS))
+ {
+ /* TSS limit too small */
+ Fast486ExceptionWithErrorCode(State, FAST486_EXCEPTION_TS, Selector);
+ }
+
+ /*
+ * The incoming task shouldn't be busy if we're executing it as a
+ * new task, and it should be busy if we're returning to it.
+ */
+ if (((NewTssDescriptor.Signature != FAST486_TSS_SIGNATURE)
+ || (Type == FAST486_TASK_RETURN))
+ && ((NewTssDescriptor.Signature != FAST486_BUSY_TSS_SIGNATURE)
+ || (Type != FAST486_TASK_RETURN)))
+ {
+ Fast486ExceptionWithErrorCode(State, FAST486_EXCEPTION_GP, Selector);
+ return FALSE;
+ }
+
+ /* Read the new TSS */
+ if (!Fast486ReadLinearMemory(State,
+ NewTssAddress,
+ &NewTss,
+ sizeof(NewTss)))
+ {
+ /* Exception occurred */
+ return FALSE;
+ }
+
+ if (Type != FAST486_TASK_CALL)
+ {
+ /* Clear the busy bit of the outgoing task */
+ FAST486_SYSTEM_DESCRIPTOR OldTssDescriptor;
+
+ if (!Fast486ReadLinearMemory(State,
+ State->Gdtr.Address
+ + GET_SEGMENT_INDEX(State->TaskReg.Selector),
+ &OldTssDescriptor,
+ sizeof(OldTssDescriptor)))
+ {
+ /* Exception occurred */
+ return FALSE;
+ }
+
+ OldTssDescriptor.Signature = FAST486_TSS_SIGNATURE;
+
+ if (!Fast486WriteLinearMemory(State,
+ State->Gdtr.Address
+ + GET_SEGMENT_INDEX(State->TaskReg.Selector),
+ &OldTssDescriptor,
+ sizeof(OldTssDescriptor)))
+ {
+ /* Exception occurred */
+ return FALSE;
+ }
+ }
+ else
+ {
+ /* Store the link */
+ NewTss.Link = State->TaskReg.Selector;
+ }
+
+ /* Save the current task into the TSS */
+ OldTss.Cr3 = State->ControlRegisters[FAST486_REG_CR3];
+ OldTss.Eip = State->InstPtr.Long;
+ OldTss.Eflags = State->Flags.Long;
+ OldTss.Eax = State->GeneralRegs[FAST486_REG_EAX].Long;
+ OldTss.Ecx = State->GeneralRegs[FAST486_REG_ECX].Long;
+ OldTss.Edx = State->GeneralRegs[FAST486_REG_EDX].Long;
+ OldTss.Ebx = State->GeneralRegs[FAST486_REG_EBX].Long;
+ OldTss.Esp = State->GeneralRegs[FAST486_REG_ESP].Long;
+ OldTss.Ebp = State->GeneralRegs[FAST486_REG_EBP].Long;
+ OldTss.Esi = State->GeneralRegs[FAST486_REG_ESI].Long;
+ OldTss.Edi = State->GeneralRegs[FAST486_REG_EDI].Long;
+ OldTss.Es = State->SegmentRegs[FAST486_REG_ES].Selector;
+ OldTss.Cs = State->SegmentRegs[FAST486_REG_CS].Selector;
+ OldTss.Ss = State->SegmentRegs[FAST486_REG_SS].Selector;
+ OldTss.Ds = State->SegmentRegs[FAST486_REG_DS].Selector;
+ OldTss.Fs = State->SegmentRegs[FAST486_REG_FS].Selector;
+ OldTss.Gs = State->SegmentRegs[FAST486_REG_GS].Selector;
+ OldTss.Ldtr = State->Ldtr.Selector;
+
+ /* Write back the old TSS */
+ if (!Fast486WriteLinearMemory(State,
+ State->TaskReg.Base,
+ &OldTss,
+ sizeof(OldTss)))
+ {
+ /* Exception occurred */
+ return FALSE;
+ }
+
+ /* Mark the new task as busy */
+ NewTssDescriptor.Signature = FAST486_BUSY_TSS_SIGNATURE;
+
+ /* Write back the new TSS descriptor */
+ if (!Fast486WriteLinearMemory(State,
+ State->Gdtr.Address + GET_SEGMENT_INDEX(Selector),
+ &NewTssDescriptor,
+ sizeof(NewTssDescriptor)))
+ {
+ /* Exception occurred */
+ return FALSE;
+ }
+
+ /* Set the task switch bit */
+ State->ControlRegisters[FAST486_REG_CR0] |= FAST486_CR0_TS;
+
+ /* Load the task register with the new values */
+ State->TaskReg.Selector = Selector;
+ State->TaskReg.Base = NewTssAddress;
+ State->TaskReg.Limit = NewTssLimit;
+
+ /* Change the page directory */
+ State->ControlRegisters[FAST486_REG_CR3] = NewTss.Cr3;
+
+ /* Flush the TLB */
+ if (State->Tlb) RtlZeroMemory(State->Tlb, NUM_TLB_ENTRIES * sizeof(ULONG));
+
+#ifndef FAST486_NO_PREFETCH
+ /* Context switching invalidates the prefetch */
+ State->PrefetchValid = FALSE;
+#endif
+
+ /* Load the registers */
+ State->InstPtr.Long = State->SavedInstPtr.Long = NewTss.Eip;
+ State->Flags.Long = NewTss.Eflags;
+ State->GeneralRegs[FAST486_REG_EAX].Long = NewTss.Eax;
+ State->GeneralRegs[FAST486_REG_ECX].Long = NewTss.Ecx;
+ State->GeneralRegs[FAST486_REG_EDX].Long = NewTss.Edx;
+ State->GeneralRegs[FAST486_REG_EBX].Long = NewTss.Ebx;
+ State->GeneralRegs[FAST486_REG_ESP].Long = NewTss.Esp;
+ State->GeneralRegs[FAST486_REG_EBP].Long = NewTss.Ebp;
+ State->GeneralRegs[FAST486_REG_ESI].Long = NewTss.Esi;
+ State->GeneralRegs[FAST486_REG_EDI].Long = NewTss.Edi;
+
+ /* Set the NT flag if nesting */
+ if (Type == FAST486_TASK_CALL) State->Flags.Nt = TRUE;
+
+ if (GET_SEGMENT_INDEX(NewTss.Ldtr) != 0)
+ {
+ BOOLEAN Valid;
+ FAST486_SYSTEM_DESCRIPTOR GdtEntry;
+
+ if (NewTss.Ldtr & SEGMENT_TABLE_INDICATOR)
+ {
+ /* This selector doesn't point to the GDT */
+ Fast486ExceptionWithErrorCode(State, FAST486_EXCEPTION_TS, NewTss.Ldtr);
+ return FALSE;
+ }
+
+ if (!Fast486ReadDescriptorEntry(State,
+ NewTss.Ldtr,
+ &Valid,
+ (PFAST486_GDT_ENTRY)&GdtEntry))
+ {
+ /* Exception occurred */
+ return FALSE;
+ }
+
+ if (!Valid)
+ {
+ /* Invalid selector */
+ Fast486ExceptionWithErrorCode(State, FAST486_EXCEPTION_TS, NewTss.Ldtr);
+ return FALSE;
+ }
+
+ if (GdtEntry.Signature != FAST486_LDT_SIGNATURE)
+ {
+ /* This is not an LDT descriptor */
+ Fast486ExceptionWithErrorCode(State, FAST486_EXCEPTION_TS, NewTss.Ldtr);
+ return FALSE;
+ }
+
+ if (!GdtEntry.Present)
+ {
+ Fast486ExceptionWithErrorCode(State, FAST486_EXCEPTION_TS, NewTss.Ldtr);
+ return FALSE;
+ }
+
+ /* Update the LDTR */
+ State->Ldtr.Selector = NewTss.Ldtr;
+ State->Ldtr.Base = GdtEntry.Base | (GdtEntry.BaseMid << 16) | (GdtEntry.BaseHigh << 24);
+ State->Ldtr.Limit = GdtEntry.Limit | (GdtEntry.LimitHigh << 16);
+ if (GdtEntry.Granularity) State->Ldtr.Limit <<= 12;
+ }
+ else
+ {
+ /* The LDT of this task is empty */
+ RtlZeroMemory(&State->Ldtr, sizeof(State->Ldtr));
+ }
+
+ /* Load the new segments */
+ if (!Fast486LoadSegmentInternal(State,
+ FAST486_REG_CS,
+ NewTss.Cs,
+ FAST486_EXCEPTION_TS))
+ {
+ return FALSE;
+ }
+
+ if (!Fast486LoadSegmentInternal(State,
+ FAST486_REG_SS,
+ NewTss.Ss,
+ FAST486_EXCEPTION_TS))
+ {
+ return FALSE;
+ }
+
+ if (!Fast486LoadSegmentInternal(State,
+ FAST486_REG_ES,
+ NewTss.Es,
+ FAST486_EXCEPTION_TS))
+ {
+ return FALSE;
+ }
+
+ if (!Fast486LoadSegmentInternal(State,
+ FAST486_REG_DS,
+ NewTss.Ds,
+ FAST486_EXCEPTION_TS))
+ {
+ return FALSE;
+ }
+
+ if (!Fast486LoadSegmentInternal(State,
+ FAST486_REG_FS,
+ NewTss.Fs,
+ FAST486_EXCEPTION_TS))
+ {
+ return FALSE;
+ }
+
+ if (!Fast486LoadSegmentInternal(State,
+ FAST486_REG_GS,
+ NewTss.Gs,
+ FAST486_EXCEPTION_TS))
+ {
+ return FALSE;
+ }
+
+ return TRUE;
+}
+
/* EOF */
projects / reactos.git / blobdiff