mirror of
https://github.com/justinian/jsix.git
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799fbbdd10
More work on process page tables, including only mapping the last 2 pml4 entries (the highest 1TiB of the address space, ie, kernel space) into a new table. Includes the work of actually moving the kernel there, which I had apparently done in name only previously. Oops.
274 lines
6.5 KiB
C++
274 lines
6.5 KiB
C++
#include <stdint.h>
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#include "kutil/assert.h"
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#include "kutil/enum_bitfields.h"
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#include "kutil/memory.h"
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#include "console.h"
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#include "log.h"
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enum class gdt_type : uint8_t
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{
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accessed = 0x01,
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read_write = 0x02,
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conforming = 0x04,
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execute = 0x08,
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system = 0x10,
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ring1 = 0x20,
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ring2 = 0x40,
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ring3 = 0x60,
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present = 0x80
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};
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IS_BITFIELD(gdt_type);
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struct gdt_descriptor
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{
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uint16_t limit_low;
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uint16_t base_low;
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uint8_t base_mid;
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gdt_type type;
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uint8_t size;
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uint8_t base_high;
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} __attribute__ ((packed));
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struct tss_descriptor
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{
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uint16_t limit_low;
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uint16_t base_00;
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uint8_t base_16;
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gdt_type type;
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uint8_t size;
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uint8_t base_24;
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uint32_t base_32;
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uint32_t reserved;
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} __attribute__ ((packed));
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struct tss_entry
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{
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uint32_t reserved0;
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uint64_t rsp[3]; // stack pointers for CPL 0-2
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uint64_t ist[8]; // ist[0] is reserved
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uint64_t reserved1;
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uint16_t reserved2;
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uint16_t iomap_offset;
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} __attribute__ ((packed));
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struct idt_descriptor
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{
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uint16_t base_low;
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uint16_t selector;
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uint8_t ist;
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uint8_t flags;
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uint16_t base_mid;
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uint32_t base_high;
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uint32_t reserved; // must be zero
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} __attribute__ ((packed));
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struct table_ptr
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{
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uint16_t limit;
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uint64_t base;
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} __attribute__ ((packed));
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gdt_descriptor g_gdt_table[10];
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idt_descriptor g_idt_table[256];
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table_ptr g_gdtr;
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table_ptr g_idtr;
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tss_entry g_tss;
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extern "C" {
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void idt_write();
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void idt_load();
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void gdt_write(uint16_t cs, uint16_t ds, uint16_t tr);
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void gdt_load();
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}
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void
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gdt_set_entry(uint8_t i, uint32_t base, uint64_t limit, bool is64, gdt_type type)
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{
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g_gdt_table[i].limit_low = limit & 0xffff;
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g_gdt_table[i].size = (limit >> 16) & 0xf;
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g_gdt_table[i].size |= (is64 ? 0xa0 : 0xc0);
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g_gdt_table[i].base_low = base & 0xffff;
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g_gdt_table[i].base_mid = (base >> 16) & 0xff;
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g_gdt_table[i].base_high = (base >> 24) & 0xff;
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g_gdt_table[i].type = type | gdt_type::system | gdt_type::present;
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}
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void
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tss_set_entry(uint8_t i, uint64_t base, uint64_t limit)
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{
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tss_descriptor tssd;
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tssd.limit_low = limit & 0xffff;
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tssd.size = (limit >> 16) & 0xf;
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tssd.base_00 = base & 0xffff;
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tssd.base_16 = (base >> 16) & 0xff;
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tssd.base_24 = (base >> 24) & 0xff;
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tssd.base_32 = (base >> 32) & 0xffffffff;
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tssd.reserved = 0;
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tssd.type =
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gdt_type::accessed |
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gdt_type::execute |
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gdt_type::ring3 |
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gdt_type::present;
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kutil::memcpy(&g_gdt_table[i], &tssd, sizeof(tss_descriptor));
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}
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void
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idt_set_entry(uint8_t i, uint64_t addr, uint16_t selector, uint8_t flags)
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{
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g_idt_table[i].base_low = addr & 0xffff;
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g_idt_table[i].base_mid = (addr >> 16) & 0xffff;
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g_idt_table[i].base_high = (addr >> 32) & 0xffffffff;
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g_idt_table[i].selector = selector;
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g_idt_table[i].flags = flags;
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g_idt_table[i].ist = 0;
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g_idt_table[i].reserved = 0;
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}
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void
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tss_set_stack(int ring, addr_t rsp)
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{
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kassert(ring < 3, "Bad ring passed to tss_set_stack.");
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g_tss.rsp[ring] = rsp;
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}
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addr_t
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tss_get_stack(int ring)
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{
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kassert(ring < 3, "Bad ring passed to tss_get_stack.");
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return g_tss.rsp[ring];
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}
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void
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gdt_init()
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{
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kutil::memset(&g_gdt_table, 0, sizeof(g_gdt_table));
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kutil::memset(&g_idt_table, 0, sizeof(g_idt_table));
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g_gdtr.limit = sizeof(g_gdt_table) - 1;
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g_gdtr.base = reinterpret_cast<uint64_t>(&g_gdt_table);
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// Kernel CS/SS - always 64bit
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gdt_set_entry(1, 0, 0xfffff, true, gdt_type::read_write | gdt_type::execute);
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gdt_set_entry(2, 0, 0xfffff, true, gdt_type::read_write);
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// User CS32/SS/CS64 - layout expected by SYSRET
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gdt_set_entry(3, 0, 0xfffff, false, gdt_type::ring3 | gdt_type::read_write | gdt_type::execute);
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gdt_set_entry(4, 0, 0xfffff, true, gdt_type::ring3 | gdt_type::read_write);
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gdt_set_entry(5, 0, 0xfffff, true, gdt_type::ring3 | gdt_type::read_write | gdt_type::execute);
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kutil::memset(&g_tss, 0, sizeof(tss_entry));
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g_tss.iomap_offset = sizeof(tss_entry);
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addr_t tss_base = reinterpret_cast<addr_t>(&g_tss);
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// Note that this takes TWO GDT entries
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tss_set_entry(6, tss_base, sizeof(tss_entry));
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gdt_write(1 << 3, 2 << 3, 6 << 3);
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g_idtr.limit = sizeof(g_idt_table) - 1;
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g_idtr.base = reinterpret_cast<uint64_t>(&g_idt_table);
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idt_write();
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}
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void
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gdt_dump()
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{
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const table_ptr &table = g_gdtr;
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console *cons = console::get();
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cons->printf(" GDT: loc:%lx size:%d\n", table.base, table.limit+1);
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int count = (table.limit + 1) / sizeof(gdt_descriptor);
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const gdt_descriptor *gdt =
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reinterpret_cast<const gdt_descriptor *>(table.base);
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for (int i = 0; i < count; ++i) {
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uint32_t base =
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(gdt[i].base_high << 24) |
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(gdt[i].base_mid << 16) |
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gdt[i].base_low;
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uint32_t limit =
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static_cast<uint32_t>(gdt[i].size & 0x0f) << 16 |
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gdt[i].limit_low;
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cons->printf(" %02d:", i);
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if (! bitfield_has(gdt[i].type, gdt_type::present)) {
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cons->puts(" Not Present\n");
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continue;
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}
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cons->printf(" Base %08x limit %05x ", base, limit);
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switch (gdt[i].type & gdt_type::ring3) {
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case gdt_type::ring3: cons->puts("ring3"); break;
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case gdt_type::ring2: cons->puts("ring2"); break;
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case gdt_type::ring1: cons->puts("ring1"); break;
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default: cons->puts("ring0"); break;
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}
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cons->printf(" %s %s %s %s %s %s %s\n",
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bitfield_has(gdt[i].type, gdt_type::accessed) ? "A" : " ",
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bitfield_has(gdt[i].type, gdt_type::read_write) ? "RW" : " ",
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bitfield_has(gdt[i].type, gdt_type::conforming) ? "C" : " ",
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bitfield_has(gdt[i].type, gdt_type::execute) ? "EX" : " ",
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bitfield_has(gdt[i].type, gdt_type::system) ? "S" : " ",
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(gdt[i].size & 0x80) ? "KB" : " B",
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(gdt[i].size & 0x60) == 0x20 ? "64" :
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(gdt[i].size & 0x60) == 0x40 ? "32" : "16");
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}
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}
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void
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idt_dump()
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{
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const table_ptr &table = g_idtr;
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log::info(logs::boot, "Loaded IDT at: %lx size: %d bytes", table.base, table.limit+1);
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int count = (table.limit + 1) / sizeof(idt_descriptor);
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const idt_descriptor *idt =
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reinterpret_cast<const idt_descriptor *>(table.base);
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for (int i = 0; i < count; ++i) {
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uint64_t base =
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(static_cast<uint64_t>(idt[i].base_high) << 32) |
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(static_cast<uint64_t>(idt[i].base_mid) << 16) |
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idt[i].base_low;
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char const *type;
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switch (idt[i].flags & 0xf) {
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case 0x5: type = " 32tsk "; break;
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case 0x6: type = " 16int "; break;
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case 0x7: type = " 16trp "; break;
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case 0xe: type = " 32int "; break;
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case 0xf: type = " 32trp "; break;
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default: type = " ????? "; break;
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}
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if (idt[i].flags & 0x80) {
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log::debug(logs::boot,
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" Entry %3d: Base:%lx Sel(rpl %d, ti %d, %3d) IST:%d %s DPL:%d", i, base,
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(idt[i].selector & 0x3),
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((idt[i].selector & 0x4) >> 2),
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(idt[i].selector >> 3),
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idt[i].ist,
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type,
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((idt[i].flags >> 5) & 0x3));
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}
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}
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}
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