// Kernel descriptor-table setup. This file owns GDT, IDT, and TSS initialization.

// GDT layout (matches segment selectors in ke_switch.asm / ke_syscall.asm):
//   0x00 null
//   0x08 ring-0 code (64-bit)
//   0x10 ring-0 data
//   0x18 ring-3 code (64-bit, DPL=3)
//   0x20 ring-3 data (DPL=3) - note: 0x1B/0x23 = 0x18|3 / 0x20|3
//   0x28 TSS low
//   0x30 TSS high.
#include <stdint.h>
#include <string.h>
#include <kernel/ke_idt.h>
#include <kernel/ke_cpu.h>
#include <kernel/ke_vectors.h>

// External assembly procedures.
extern void KeFlushGdt(void* pGdtr, uint16_t codeSel, uint16_t dataSel, uint16_t tssSel);
extern void KeFlushIdt(void* pIdtr);

extern void KeIrqStub0(void);
extern void KeIrqStub1(void);
extern void KeIrqStub2(void);
extern void KeIrqStub3(void);
extern void KeIrqStub4(void);
extern void KeIrqStub5(void);
extern void KeIrqStub6(void);
extern void KeIrqStub7(void);
extern void KeIrqStub8(void);
extern void KeIrqStub9(void);
extern void KeIrqStub10(void);
extern void KeIrqStub11(void);
extern void KeIrqStub12(void);
extern void KeIrqStub13(void);
extern void KeIrqStub14(void);
extern void KeIrqStub15(void);
extern void KeIrqStub16(void);
extern void KeIrqStub17(void);
extern void KeIrqStub18(void);
extern void KeIrqStub19(void);
extern void KeIrqStub20(void);
extern void KeIrqStub21(void);
extern void KeIrqStub22(void);
extern void KeIrqStub23(void);
extern void KeIrqStub24(void);
extern void KeIrqStub25(void);
extern void KeIrqStub26(void);
extern void KeIrqStub27(void);
extern void KeIrqStub28(void);
extern void KeIrqStub29(void);
extern void KeIrqStub30(void);
extern void KeIrqStub31(void);
extern void KeIrqStub32(void);
extern void KeIrqStub33(void);
extern void KeIrqStub34(void);
extern void KeIrqStub35(void);
extern void KeIrqStub36(void);
extern void KeIrqStub37(void);
extern void KeIrqStub38(void);
extern void KeIrqStub39(void);
extern void KeIrqStub40(void);
extern void KeIrqStub41(void);
extern void KeIrqStub42(void);
extern void KeIrqStub43(void);
extern void KeIrqStub44(void);
extern void KeIrqStub45(void);
extern void KeIrqStub46(void);
extern void KeIrqStub47(void);
extern void KeIrqStub48(void);
extern void KeIrqStub49(void);
extern void KeIrqStub50(void);
extern void KeIrqStub51(void);
extern void KeIrqStub52(void);
extern void KeIrqStub53(void);
extern void KeIrqStub54(void);
extern void KeIrqStub55(void);
extern void KeIrqStub56(void);
extern void KeIrqStub57(void);
extern void KeIrqStub58(void);
extern void KeIrqStub59(void);
extern void KeIrqStub60(void);
extern void KeIrqStub61(void);
extern void KeIrqStub62(void);
extern void KeIrqStub63(void);
extern void KeIrqStub64(void);
extern void KeIrqStub65(void);
extern void KeIrqStub66(void);
extern void KeIrqStub67(void);
extern void KeIrqStub68(void);
extern void KeIrqStub69(void);
extern void KeIrqStub70(void);
extern void KeIrqStub71(void);
extern void KeIrqStub72(void);
extern void KeIrqStub73(void);
extern void KeIrqStub74(void);
extern void KeIrqStub75(void);
extern void KeIrqStub76(void);
extern void KeIrqStub77(void);
extern void KeIrqStub78(void);
extern void KeIrqStub79(void);
extern void KeIrqStub80(void);
extern void KeIrqStub81(void);
extern void KeIrqStub82(void);
extern void KeIrqStub83(void);
extern void KeIrqStub84(void);
extern void KeIrqStub85(void);
extern void KeIrqStub86(void);
extern void KeIrqStub87(void);
extern void KeIrqStub88(void);
extern void KeIrqStub89(void);
extern void KeIrqStub90(void);
extern void KeIrqStub91(void);
extern void KeIrqStub92(void);
extern void KeIrqStub93(void);
extern void KeIrqStub94(void);
extern void KeIrqStub95(void);
extern void KeIrqStub96(void);
extern void KeIrqStub97(void);
extern void KeIrqStub98(void);
extern void KeIrqStub99(void);
extern void KeIrqStub100(void);
extern void KeIrqStub101(void);
extern void KeIrqStub102(void);
extern void KeIrqStub103(void);
extern void KeIrqStub104(void);
extern void KeIrqStub105(void);
extern void KeIrqStub106(void);
extern void KeIrqStub107(void);
extern void KeIrqStub108(void);
extern void KeIrqStub109(void);
extern void KeIrqStub110(void);
extern void KeIrqStub111(void);
extern void KeIrqStub112(void);
extern void KeIrqStub113(void);
extern void KeIrqStub114(void);
extern void KeIrqStub115(void);
extern void KeIrqStub116(void);
extern void KeIrqStub117(void);
extern void KeIrqStub118(void);
extern void KeIrqStub119(void);
extern void KeIrqStub120(void);
extern void KeIrqStub121(void);
extern void KeIrqStub122(void);
extern void KeIrqStub123(void);
extern void KeIrqStub124(void);
extern void KeIrqStub125(void);
extern void KeIrqStub126(void);
extern void KeIrqStub127(void);
extern void KeIrqStub128(void);
extern void KeIrqStub129(void);
extern void KeIrqStub130(void);
extern void KeIrqStub131(void);
extern void KeIrqStub132(void);
extern void KeIrqStub133(void);
extern void KeIrqStub134(void);
extern void KeIrqStub135(void);
extern void KeIrqStub136(void);
extern void KeIrqStub137(void);
extern void KeIrqStub138(void);
extern void KeIrqStub139(void);
extern void KeIrqStub140(void);
extern void KeIrqStub141(void);
extern void KeIrqStub142(void);
extern void KeIrqStub143(void);
extern void KeIrqStub144(void);
extern void KeIrqStub145(void);
extern void KeIrqStub146(void);
extern void KeIrqStub147(void);
extern void KeIrqStub148(void);
extern void KeIrqStub149(void);
extern void KeIrqStub150(void);
extern void KeIrqStub151(void);
extern void KeIrqStub152(void);
extern void KeIrqStub153(void);
extern void KeIrqStub154(void);
extern void KeIrqStub155(void);
extern void KeIrqStub156(void);
extern void KeIrqStub157(void);
extern void KeIrqStub158(void);
extern void KeIrqStub159(void);
extern void KeRescheduleIpiStub(void);
extern void KeLocalTimerStub(void);
extern void KeSpuriousStub(void);

extern void KeFaultDB(void);
extern void KeFaultNMI(void);
extern void KeNmiIpiStub(void);
extern void KeFaultBP(void);
extern void KeFaultOF(void);
extern void KeFaultBR(void);
extern void KeFaultUD(void);
extern void KeFaultNM(void);
extern void KeFaultDF(void);
extern void KeFaultCSO(void);
extern void KeFaultTS(void);
extern void KeFaultNP(void);
extern void KeFaultSS(void);
extern void KeFaultRSV15(void);
extern void KeFaultMF(void);
extern void KeFaultAC(void);
extern void KeFaultMC(void);
extern void KeFaultXM(void);
extern void KeFaultVE(void);
extern void KeFaultCP(void);
extern void KeFaultRSV22(void);
extern void KeFaultRSV23(void);
extern void KeFaultRSV24(void);
extern void KeFaultRSV25(void);
extern void KeFaultRSV26(void);
extern void KeFaultRSV27(void);
extern void KeFaultHV(void);
extern void KeFaultVC(void);
extern void KeFaultSX(void);
extern void KeFaultRSV31(void);

#define NUM_DEVICE_VECTORS (KE_VECTOR_DEVICE_LAST - KE_VECTOR_DEVICE_FIRST + 1u)

// GDT.
static void KiGdtSetEntry(uint64_t* gdt, int idx, uint32_t base, uint32_t limit,
                        uint8_t access, uint8_t flags) {
    gdt[idx] =
        ((uint64_t)(limit & 0xFFFF))           |
        ((uint64_t)(base  & 0xFFFFFF) << 16)   |
        ((uint64_t)access             << 40)   |
        ((uint64_t)(limit >> 16 & 0xF)<< 48)   |
        ((uint64_t)(flags & 0xF)      << 52)   |
        ((uint64_t)(base >> 24 & 0xFF)<< 56);
}

// Implements the gdt Set Tss operation.
static void KiGdtSetTss(uint64_t* gdt, int idx, uintptr_t base, uint32_t limit) {
    // TSS descriptor is 16 bytes (two GDT slots).
    gdt[idx]   = 0;
    gdt[idx+1] = 0;

    gdt[idx] =
        ((uint64_t)(limit & 0xFFFF))            |
        ((uint64_t)(base  & 0xFFFFFF) << 16)    |
        (0x89ULL                      << 40)    |  // P=1,DPL=0,type=TSS64 avail
        ((uint64_t)((limit>>16)&0xF)  << 48)    |
        ((uint64_t)(base>>24 & 0xFF)  << 56);

    gdt[idx+1] = (base >> 32);
}

// Initializes gdt For Cpu.
void KeInitializeGdtForCpu(KCPU* cpu) {
    if (!cpu) return;

    TSS64* tss = &cpu->Tss;
    uint64_t* gdt = cpu->Gdt;

    memset(gdt, 0, sizeof(cpu->Gdt));

    // 0x00: Null.
    KiGdtSetEntry(gdt, 0, 0, 0, 0, 0);
    // 0x08: Ring-0 Code (Access 0x9A, Flags 0xA for 64-bit).
    KiGdtSetEntry(gdt, 1, 0, 0xFFFFF, 0x9A, 0xA);
    // 0x10: Ring-0 Data.
    KiGdtSetEntry(gdt, 2, 0, 0xFFFFF, 0x92, 0xC);
    // 0x18: Ring-3 Code.
    KiGdtSetEntry(gdt, 3, 0, 0xFFFFF, 0xFA, 0xA);
    // 0x20: Ring-3 Data.
    KiGdtSetEntry(gdt, 4, 0, 0xFFFFF, 0xF2, 0xC);

    // 0x28: CPU-local TSS (occupies slots 0x28 and 0x30).
    tss->IoMapBase = sizeof(TSS64);
    if (!tss->RSP0)
        tss->RSP0 = cpu->KernelStackTop;

    KiGdtSetTss(gdt, 5, (uintptr_t)tss, sizeof(TSS64) - 1);

    cpu->Gdtr.Limit = sizeof(cpu->Gdt) - 1;
    cpu->Gdtr.Base = (uint64_t)cpu->Gdt;
}

// Loads gdt For Current Cpu.
void KeLoadGdtForCurrentCpu(KCPU* cpu) {
    if (!cpu) cpu = KeGetCurrentCpu();
    KeFlushGdt(&cpu->Gdtr, 0x08, 0x10, 0x28);

    // Reloading GS as a segment register during GDT reload can disturb the
    // hidden GS base. Reinstall the kernel per-CPU base immediately after
    // the descriptor reload so KeGetCurrentCpu() remains GS-backed.
    KeLoadKernelGsBase(cpu);
}

// Initializes gdt.
void KeInitializeGdt(void) {
    KCPU* cpu = KeGetCurrentCpu();
    KeInitializeGdtForCpu(cpu);
    KeLoadGdtForCurrentCpu(cpu);
}

// Updates current Tss Rsp0.
void KeSetCurrentTssRsp0(uintptr_t rsp0) {
    TSS64* tss = KeGetCurrentTss();
    if (tss)
        tss->RSP0 = rsp0;
}

// IDT.
#define IDT_ENTRIES  256

#define KI_IDT_TYPE_INTERRUPT_GATE     0x8Eu
#define KI_IDT_TYPE_USER_INTERRUPT_GATE 0xEEu

#pragma pack(push, 1)
typedef struct {
    uint16_t OffsetLow;
    uint16_t Selector;
    uint8_t  Ist;
    uint8_t  TypeAttr;
    uint16_t OffsetMid;
    uint32_t OffsetHigh;
    uint32_t MustBeZero;
} IDT_ENTRY;
#pragma pack(pop)

static IDT_ENTRY gIdt[IDT_ENTRIES];

#pragma pack(push, 1)
typedef struct { uint16_t Limit; uint64_t Base; } IDTR;
#pragma pack(pop)

static void KiIdtSetGate(int vec, uintptr_t handler,
                       uint8_t typeAttr, uint8_t ist) {
    gIdt[vec].OffsetLow  = (uint16_t)(handler & 0xFFFF);
    gIdt[vec].Selector   = 0x08;   // ring-0 code segment
    gIdt[vec].Ist        = ist;
    gIdt[vec].TypeAttr   = typeAttr;
    gIdt[vec].OffsetMid  = (uint16_t)((handler >> 16) & 0xFFFF);
    gIdt[vec].OffsetHigh = (uint32_t)((handler >> 32) & 0xFFFFFFFF);
    gIdt[vec].MustBeZero = 0;
}

// Initializes idt.
void KeInitializeIdt(void) {
    memset(gIdt, 0, sizeof(gIdt));

    static void* faultStubs[32] = {
        (void*)KeFaultDE,    (void*)KeFaultDB,    (void*)KeNmiIpiStub,
        (void*)KeFaultBP,    (void*)KeFaultOF,    (void*)KeFaultBR,
        (void*)KeFaultUD,    (void*)KeFaultNM,    (void*)KeFaultDF,
        (void*)KeFaultCSO,   (void*)KeFaultTS,    (void*)KeFaultNP,
        (void*)KeFaultSS,    (void*)KeFaultGP,    (void*)KeFaultPF,
        (void*)KeFaultRSV15, (void*)KeFaultMF,    (void*)KeFaultAC,
        (void*)KeFaultMC,    (void*)KeFaultXM,    (void*)KeFaultVE,
        (void*)KeFaultCP,    (void*)KeFaultRSV22, (void*)KeFaultRSV23,
        (void*)KeFaultRSV24, (void*)KeFaultRSV25, (void*)KeFaultRSV26,
        (void*)KeFaultRSV27, (void*)KeFaultHV,    (void*)KeFaultVC,
        (void*)KeFaultSX,    (void*)KeFaultRSV31,
    };

    for (int i = 0; i < 32; i++)
        KiIdtSetGate(i, (uintptr_t)faultStubs[i], KI_IDT_TYPE_INTERRUPT_GATE, 0);

    // User-mode INT3 must enter #BP, not fail the gate-DPL check and become #GP.
    KiIdtSetGate(3, (uintptr_t)KeFaultBP, KI_IDT_TYPE_USER_INTERRUPT_GATE, 0);

    KiIdtSetGate(KE_VECTOR_SYSCALL, (uintptr_t)KeSyscallEntry, KI_IDT_TYPE_USER_INTERRUPT_GATE, 0);

    static void* irqStubs[NUM_DEVICE_VECTORS] = {
        (void*)KeIrqStub0,
        (void*)KeIrqStub1,
        (void*)KeIrqStub2,
        (void*)KeIrqStub3,
        (void*)KeIrqStub4,
        (void*)KeIrqStub5,
        (void*)KeIrqStub6,
        (void*)KeIrqStub7,
        (void*)KeIrqStub8,
        (void*)KeIrqStub9,
        (void*)KeIrqStub10,
        (void*)KeIrqStub11,
        (void*)KeIrqStub12,
        (void*)KeIrqStub13,
        (void*)KeIrqStub14,
        (void*)KeIrqStub15,
        (void*)KeIrqStub16,
        (void*)KeIrqStub17,
        (void*)KeIrqStub18,
        (void*)KeIrqStub19,
        (void*)KeIrqStub20,
        (void*)KeIrqStub21,
        (void*)KeIrqStub22,
        (void*)KeIrqStub23,
        (void*)KeIrqStub24,
        (void*)KeIrqStub25,
        (void*)KeIrqStub26,
        (void*)KeIrqStub27,
        (void*)KeIrqStub28,
        (void*)KeIrqStub29,
        (void*)KeIrqStub30,
        (void*)KeIrqStub31,
        (void*)KeIrqStub32,
        (void*)KeIrqStub33,
        (void*)KeIrqStub34,
        (void*)KeIrqStub35,
        (void*)KeIrqStub36,
        (void*)KeIrqStub37,
        (void*)KeIrqStub38,
        (void*)KeIrqStub39,
        (void*)KeIrqStub40,
        (void*)KeIrqStub41,
        (void*)KeIrqStub42,
        (void*)KeIrqStub43,
        (void*)KeIrqStub44,
        (void*)KeIrqStub45,
        (void*)KeIrqStub46,
        (void*)KeIrqStub47,
        (void*)KeIrqStub48,
        (void*)KeIrqStub49,
        (void*)KeIrqStub50,
        (void*)KeIrqStub51,
        (void*)KeIrqStub52,
        (void*)KeIrqStub53,
        (void*)KeIrqStub54,
        (void*)KeIrqStub55,
        (void*)KeIrqStub56,
        (void*)KeIrqStub57,
        (void*)KeIrqStub58,
        (void*)KeIrqStub59,
        (void*)KeIrqStub60,
        (void*)KeIrqStub61,
        (void*)KeIrqStub62,
        (void*)KeIrqStub63,
        (void*)KeIrqStub64,
        (void*)KeIrqStub65,
        (void*)KeIrqStub66,
        (void*)KeIrqStub67,
        (void*)KeIrqStub68,
        (void*)KeIrqStub69,
        (void*)KeIrqStub70,
        (void*)KeIrqStub71,
        (void*)KeIrqStub72,
        (void*)KeIrqStub73,
        (void*)KeIrqStub74,
        (void*)KeIrqStub75,
        (void*)KeIrqStub76,
        (void*)KeIrqStub77,
        (void*)KeIrqStub78,
        (void*)KeIrqStub79,
        (void*)KeIrqStub80,
        (void*)KeIrqStub81,
        (void*)KeIrqStub82,
        (void*)KeIrqStub83,
        (void*)KeIrqStub84,
        (void*)KeIrqStub85,
        (void*)KeIrqStub86,
        (void*)KeIrqStub87,
        (void*)KeIrqStub88,
        (void*)KeIrqStub89,
        (void*)KeIrqStub90,
        (void*)KeIrqStub91,
        (void*)KeIrqStub92,
        (void*)KeIrqStub93,
        (void*)KeIrqStub94,
        (void*)KeIrqStub95,
        (void*)KeIrqStub96,
        (void*)KeIrqStub97,
        (void*)KeIrqStub98,
        (void*)KeIrqStub99,
        (void*)KeIrqStub100,
        (void*)KeIrqStub101,
        (void*)KeIrqStub102,
        (void*)KeIrqStub103,
        (void*)KeIrqStub104,
        (void*)KeIrqStub105,
        (void*)KeIrqStub106,
        (void*)KeIrqStub107,
        (void*)KeIrqStub108,
        (void*)KeIrqStub109,
        (void*)KeIrqStub110,
        (void*)KeIrqStub111,
        (void*)KeIrqStub112,
        (void*)KeIrqStub113,
        (void*)KeIrqStub114,
        (void*)KeIrqStub115,
        (void*)KeIrqStub116,
        (void*)KeIrqStub117,
        (void*)KeIrqStub118,
        (void*)KeIrqStub119,
        (void*)KeIrqStub120,
        (void*)KeIrqStub121,
        (void*)KeIrqStub122,
        (void*)KeIrqStub123,
        (void*)KeIrqStub124,
        (void*)KeIrqStub125,
        (void*)KeIrqStub126,
        (void*)KeIrqStub127,
        (void*)KeIrqStub128,
        (void*)KeIrqStub129,
        (void*)KeIrqStub130,
        (void*)KeIrqStub131,
        (void*)KeIrqStub132,
        (void*)KeIrqStub133,
        (void*)KeIrqStub134,
        (void*)KeIrqStub135,
        (void*)KeIrqStub136,
        (void*)KeIrqStub137,
        (void*)KeIrqStub138,
        (void*)KeIrqStub139,
        (void*)KeIrqStub140,
        (void*)KeIrqStub141,
        (void*)KeIrqStub142,
        (void*)KeIrqStub143,
        (void*)KeIrqStub144,
        (void*)KeIrqStub145,
        (void*)KeIrqStub146,
        (void*)KeIrqStub147,
        (void*)KeIrqStub148,
        (void*)KeIrqStub149,
        (void*)KeIrqStub150,
        (void*)KeIrqStub151,
        (void*)KeIrqStub152,
        (void*)KeIrqStub153,
        (void*)KeIrqStub154,
        (void*)KeIrqStub155,
        (void*)KeIrqStub156,
        (void*)KeIrqStub157,
        (void*)KeIrqStub158,
        (void*)KeIrqStub159,
    };
    for (uint32_t i = 0; i < NUM_DEVICE_VECTORS; i++)
        KiIdtSetGate(KE_VECTOR_DEVICE_FIRST + i, (uintptr_t)irqStubs[i],
                     KI_IDT_TYPE_INTERRUPT_GATE, 0);

    KiIdtSetGate(KE_VECTOR_CPU_TIMER, (uintptr_t)KeLocalTimerStub,
                  KI_IDT_TYPE_INTERRUPT_GATE, 0);
    KiIdtSetGate(KE_VECTOR_RESCHEDULE_IPI, (uintptr_t)KeRescheduleIpiStub,
                  KI_IDT_TYPE_INTERRUPT_GATE, 0);
    KiIdtSetGate(KE_VECTOR_SPURIOUS, (uintptr_t)KeSpuriousStub,
                  KI_IDT_TYPE_INTERRUPT_GATE, 0);

    KeLoadIdtForCurrentCpu();
}

// Loads idt For Current Cpu.
void KeLoadIdtForCurrentCpu(void) {
    IDTR idtr = { sizeof(gIdt) - 1, (uint64_t)gIdt };
    KeFlushIdt(&idtr);
}