ptos/amd64: Add task state segment

Signed-off-by: Chloe M <chloe@mensia.org>
2026-07-13 23:27:01 -04:00
parent 4165241b6f
commit bb55a52b69
4 changed files with 258 additions and 0 deletions
@@ -12,6 +12,10 @@
 #include <machine/trap.h>
 #include <machine/msr.h>
 #include <machine/lapic.h>
+#include <machine/gdt.h>
+
+/* Externs */
+extern GDT_ENTRY g_GDT[GDT_ENTRY_COUNT];

 /*
 * Initialize interrupts for the current processor
@@ -66,9 +70,22 @@ HalKpcrP1Init(KPCR *Kpcr)
 VOID
 HalKpcrP2Init(KPCR *Kpcr)
 {
+    TSS_DESCRIPTOR *TssDesc;
+
    /* Initialize per-processor pools */
    ExPoolRegionInit(&Kpcr->PoolRegion);

    /* Initialize the Local APIC unit */
    MdLapicInit(Kpcr);
+
+    /* Load the Task State Segment */
+    TssDesc = (TSS_DESCRIPTOR *)&g_GDT[GDT_TSS_INDEX];
+    MdTssInit(TssDesc);
+    ASMV(
+        "mov %0, %%ax\n"
+        "ltr %%ax\n"
+        :
+        : "i" (GDT_TSS)
+        : "memory"
+    );
 }
@@ -0,0 +1,139 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description: Task state segment
+ * Author:      Chloe M.
+ */
+
+#include <machine/tss.h>
+#include <hal/kpcr.h>
+#include <ex/pool.h>
+#include <ke/bugcheck.h>
+
+#define TSS_POOL_TAG 'TSS'
+
+VOID
+MdTssAllocIst(UCHAR IstIndex, USIZE StackSize)
+{
+    KPCR *Kpcr;
+    MCB *Mcb;
+    TSS_ENTRY *TssEntry;
+    UPTR StackBase, *Ptr;
+    UPTR StackTop;
+    ULONG BaseLow, BaseHigh;
+
+    if (StackSize == 0 || IstIndex > 7) {
+        return;
+    }
+
+    Kpcr = HalKpcrCurrent();
+    Mcb = &Kpcr->Mcb;
+    TssEntry = Mcb->Tss;
+
+    /* Allocate the stack */
+    Ptr = ExAllocatePoolWithTag(
+        POOL_NON_PAGED,
+        StackSize,
+        TSS_POOL_TAG
+    );
+
+    if (Ptr == NULL) {
+        KeBugCheck(
+            BUGCHECK_OOM,
+            "failed to allocate interrupt stack %d\n",
+            IstIndex
+        );
+    }
+
+    /* Obtain the stack base */
+    StackBase = (UPTR)Ptr;
+    StackTop = StackBase + StackSize;
+    BaseLow = StackTop & 0xFFFFFFFF;
+    BaseHigh = (StackTop >> 32) & 0xFFFFFFFF;
+
+    /* Set the target index */
+    switch (IstIndex) {
+    case 0:
+        KeBugCheck(
+            BUGCHECK_MISC,
+            "cannot set IST index 0\n"
+        );
+
+        break;
+    case 1:
+        TssEntry->Ist1Low = BaseLow;
+        TssEntry->Ist1High = BaseHigh;
+        break;
+    case 2:
+        TssEntry->Ist2Low = BaseLow;
+        TssEntry->Ist2High = BaseHigh;
+        break;
+    case 3:
+        TssEntry->Ist3Low = BaseLow;
+        TssEntry->Ist3High = BaseHigh;
+        break;
+    case 4:
+        TssEntry->Ist4Low = BaseLow;
+        TssEntry->Ist4High = BaseHigh;
+        break;
+    case 5:
+        TssEntry->Ist5Low = BaseLow;
+        TssEntry->Ist5High = BaseHigh;
+        break;
+    case 6:
+        TssEntry->Ist6Low = BaseLow;
+        TssEntry->Ist6High = BaseHigh;
+        break;
+    case 7:
+        TssEntry->Ist7Low = BaseLow;
+        TssEntry->Ist7High = BaseHigh;
+        break;
+    }
+}
+
+VOID
+MdTssInit(TSS_DESCRIPTOR *Descriptor)
+{
+    TSS_ENTRY *TssEntry;
+    KPCR *KpcrCurrent;
+    MCB *Mcb;
+    UPTR TssBase;
+
+    if (Descriptor == NULL) {
+        KeBugCheck(
+            BUGCHECK_MISC,
+            "bad descriptor passed to MdTssInit()\n"
+        );
+    }
+
+    TssEntry = ExAllocatePoolWithTag(
+        POOL_NON_PAGED,
+        sizeof(*TssEntry),
+        TSS_POOL_TAG
+    );
+
+    if (TssEntry == NULL) {
+        KeBugCheck(
+            BUGCHECK_OOM,
+            "out of memory when allocating tss\n"
+        );
+    }
+
+    TssBase = (UPTR)TssEntry;
+    Descriptor->SegmentLimit = sizeof(*TssEntry);
+    Descriptor->Present = 1;
+    Descriptor->Gran = 1;
+    Descriptor->Type = 0x9;
+    Descriptor->Avl = 0;
+    Descriptor->Dpl = 0;
+    Descriptor->BaseLow16 = TssBase & 0xFFFF;
+    Descriptor->BaseMid8 = (TssBase >> 16) & 0xFF;
+    Descriptor->BaseHighMid8 = (TssBase >> 24) & 0xFF;
+    Descriptor->BaseHigh32 = (TssBase >> 32) & 0xFFFFFFFF;
+    TssEntry->IoBitmap = 0xFF;
+
+    KpcrCurrent = HalKpcrCurrent();
+    Mcb = &KpcrCurrent->Mcb;
+    Mcb->Tss = TssEntry;
+}