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Kernel: Cleanup GDT code

This commit is contained in:
Bananymous 2023-10-13 16:18:22 +03:00
parent 6b180da4e8
commit 45a6783c3d
1 changed files with 21 additions and 25 deletions
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46
kernel/arch/x86_64/GDT.cpp
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@ -1,4 +1,4 @@
#include <BAN/Assert.h> #include <BAN/Array.h>
#include <kernel/GDT.h> #include <kernel/GDT.h>
#include <string.h> #include <string.h>
@ -56,44 +56,44 @@ namespace Kernel::GDT
static constexpr uint16_t s_tss_offset = 0x28; static constexpr uint16_t s_tss_offset = 0x28;
static TaskStateSegment* s_tss = nullptr; static TaskStateSegment s_tss;
static SegmentDescriptor* s_gdt = nullptr; static BAN::Array<SegmentDescriptor, 7> s_gdt; // null, kernel code, kernel data, user code, user data, tss low, tss high
static GDTR s_gdtr; static GDTR s_gdtr;
static void write_entry(uint8_t offset, uint32_t base, uint32_t limit, uint8_t access, uint8_t flags) static void write_entry(uint8_t offset, uint32_t base, uint32_t limit, uint8_t access, uint8_t flags)
{ {
SegmentDescriptor& desc = *(SegmentDescriptor*)((uintptr_t)s_gdt + offset); ASSERT(offset % sizeof(SegmentDescriptor) == 0);
desc.base1 = base;
desc.base2 = base >> 16;
desc.base3 = base >> 24;
desc.limit1 = limit; SegmentDescriptor& desc = s_gdt[offset / sizeof(SegmentDescriptor)];
desc.limit2 = limit >> 16; desc.base1 = (base >> 0) & 0xFFFF;
desc.base2 = (base >> 16) & 0xFF;
desc.base3 = (base >> 24) & 0xFF;
desc.access = access; desc.limit1 = (limit >> 0) & 0xFFFF;
desc.limit2 = (limit >> 16) & 0x0F;
desc.flags = flags; desc.access = access & 0xFF;
desc.flags = flags & 0x0F;
} }
static void write_tss() static void write_tss()
{ {
s_tss = new TaskStateSegment(); memset(&s_tss, 0x00, sizeof(TaskStateSegment));
ASSERT(s_tss); s_tss.iopb = sizeof(TaskStateSegment);
memset(s_tss, 0x00, sizeof(TaskStateSegment)); uint64_t base = (uint64_t)&s_tss;
s_tss->rsp0 = 0;
uintptr_t base = (uintptr_t)s_tss;
write_entry(s_tss_offset, (uint32_t)base, sizeof(TaskStateSegment), 0x89, 0x0); write_entry(s_tss_offset, (uint32_t)base, sizeof(TaskStateSegment), 0x89, 0x0);
SegmentDescriptor& desc = *(SegmentDescriptor*)((uintptr_t)s_gdt + s_tss_offset + 0x08);
SegmentDescriptor& desc = s_gdt[s_tss_offset / sizeof(SegmentDescriptor) + 1];
desc.low = base >> 32; desc.low = base >> 32;
desc.high = 0; desc.high = 0;
} }
void set_tss_stack(uintptr_t rsp) void set_tss_stack(uintptr_t rsp)
{ {
s_tss->rsp0 = rsp; s_tss.rsp0 = rsp;
} }
static void flush_gdt() static void flush_gdt()
@ -108,12 +108,8 @@ namespace Kernel::GDT
void initialize() void initialize()
{ {
constexpr uint32_t descriptor_count = 6 + 1; // tss takes 2 s_gdtr.address = (uint64_t)&s_gdt;
s_gdt = new SegmentDescriptor[descriptor_count]; s_gdtr.size = s_gdt.size() * sizeof(SegmentDescriptor) - 1;
ASSERT(s_gdt);
s_gdtr.address = (uint64_t)s_gdt;
s_gdtr.size = descriptor_count * sizeof(SegmentDescriptor) - 1;
write_entry(0x00, 0x00000000, 0x00000, 0x00, 0x0); // null write_entry(0x00, 0x00000000, 0x00000, 0x00, 0x0); // null
write_entry(0x08, 0x00000000, 0xFFFFF, 0x9A, 0xA); // kernel code write_entry(0x08, 0x00000000, 0xFFFFF, 0x9A, 0xA); // kernel code