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Ported the GDT and TSS to x64.

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This commit is contained in:
Jonas 'Sortie' Termansen 2011-10-02 16:00:02 +02:00
parent a1cf7e9dbc
commit 4579384312
4 changed files with 208 additions and 104 deletions
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114
sortix/descriptor_tables.cpp
View file

@ -33,26 +33,45 @@ namespace Sortix
{
namespace GDT
{
// Lets us access our ASM functions from our C++ code.
extern "C" void gdt_flush(addr_t);
extern "C" void tss_flush();
gdt_entry_t gdt_entries[6];
const size_t GDT_NUM_ENTRIES = 7;
gdt_entry_t gdt_entries[GDT_NUM_ENTRIES];
gdt_ptr_t gdt_ptr;
tss_entry_t tss_entry;
const uint8_t GRAN_64_BIT_MODE = 1<<5;
const uint8_t GRAN_32_BIT_MODE = 1<<6;
const uint8_t GRAN_4KIB_BLOCKS = 1<<7;
void Init()
{
gdt_ptr.limit = (sizeof(gdt_entry_t) * 6) - 1;
gdt_ptr.limit = (sizeof(gdt_entry_t) * GDT_NUM_ENTRIES) - 1;
gdt_ptr.base = (addr_t) &gdt_entries;
#ifdef PLATFORM_X86
const uint8_t gran = GRAN_4KIB_BLOCKS | GRAN_32_BIT_MODE;
#elif defined(PLATFORM_X64)
const uint8_t gran = GRAN_4KIB_BLOCKS | GRAN_64_BIT_MODE;
#endif
SetGate(0, 0, 0, 0, 0); // Null segment
SetGate(1, 0, 0xFFFFFFFF, 0x9A, 0xCF); // Code segment
SetGate(2, 0, 0xFFFFFFFF, 0x92, 0xCF); // Data segment
SetGate(3, 0, 0xFFFFFFFF, 0xFA, 0xCF); // User mode code segment
SetGate(4, 0, 0xFFFFFFFF, 0xF2, 0xCF); // User mode data segment
SetGate(1, 0, 0xFFFFFFFF, 0x9A, gran); // Code segment
SetGate(2, 0, 0xFFFFFFFF, 0x92, gran); // Data segment
SetGate(3, 0, 0xFFFFFFFF, 0xFA, gran); // User mode code segment
SetGate(4, 0, 0xFFFFFFFF, 0xF2, gran); // User mode data segment
WriteTSS(5, 0x10, 0x0);
if ( gdt_ptr.base != (addr_t) &gdt_entries )
{
// If this happens, then either there is a bug in the GDT entry
// writing code - or the struct gdt_entries above is too small.
Panic("Whoops, someone overwrote the GDT pointer while writing "
"to the GDT entries!");
}
gdt_flush((addr_t) &gdt_ptr);
tss_flush();
}
@ -60,47 +79,76 @@ namespace Sortix
// Set the value of a GDT entry.
void SetGate(int32_t num, uint32_t base, uint32_t limit, uint8_t access, uint8_t gran)
{
gdt_entries[num].base_low = (base & 0xFFFF);
gdt_entries[num].base_middle = (base >> 16) & 0xFF;
gdt_entries[num].base_high = (base >> 24) & 0xFF;
gdt_entry_t* entry = (gdt_entry_t*) (&gdt_entries[num]);
gdt_entries[num].limit_low = (limit & 0xFFFF);
gdt_entries[num].granularity = (limit >> 16) & 0x0F;
gdt_entries[num].granularity |= gran & 0xF0;
gdt_entries[num].access = access;
entry->base_low = (base & 0xFFFF);
entry->base_middle = (base >> 16) & 0xFF;
entry->base_high = (base >> 24) & 0xFF;
entry->limit_low = (limit & 0xFFFF);
entry->granularity = ((limit >> 16) & 0x0F) | (gran & 0xF0);
entry->access = access;
}
// Set the value of a GDT entry.
void SetGate64(int32_t num, uint64_t base, uint32_t limit, uint8_t access, uint8_t gran)
{
gdt_entry64_t* entry = (gdt_entry64_t*) (&gdt_entries[num]);
entry->base_low = (base & 0xFFFF);
entry->base_middle = (base >> 16) & 0xFF;
entry->base_high = (base >> 24) & 0xFF;
entry->base_highest = (base >> 32);
entry->limit_low = (limit & 0xFFFF);
entry->granularity = ((limit >> 16) & 0x0F) | (gran & 0xF0);
entry->access = access;
entry->zero1 = 0;
}
// Initialise our task state segment structure.
void WriteTSS(int32_t num, uint16_t ss0, uint32_t esp0)
void WriteTSS(int32_t num, uint16_t ss0, addr_t stack0)
{
// Firstly, let's compute the base and limit of our entry into the GDT.
addr_t base = (addr_t) &tss_entry;
uint32_t limit = base + sizeof(tss_entry);
// First, let's compute the base and limit of our entry in the GDT.
addr_t base = (addr_t) &tss_entry;
uint32_t limit = base + sizeof(tss_entry);
// Now, add our TSS descriptor's address to the GDT.
SetGate(num, base, limit, 0xE9, 0x00);
// Now, add our TSS descriptor's address to the GDT.
#ifdef PLATFORM_X86
SetGate(num, base, limit, 0xE9, 0x00);
#elif defined(PLATFORM_X64)
SetGate64(num, base, limit, 0xE9, 0x00);
#endif
// Ensure the descriptor is initially zero.
Memory::Set(&tss_entry, 0, sizeof(tss_entry));
// Ensure the descriptor is initially zero.
Memory::Set(&tss_entry, 0, sizeof(tss_entry));
tss_entry.ss0 = ss0; // Set the kernel stack segment.
tss_entry.esp0 = esp0; // Set the kernel stack pointer.
#ifdef PLATFORM_X86
tss_entry.ss0 = ss0; // Set the kernel stack segment.
tss_entry.esp0 = stack0; // Set the kernel stack pointer.
// Here we set the cs, ss, ds, es, fs and gs entries in the TSS. These specify what
// segments should be loaded when the processor switches to kernel mode. Therefore
// they are just our normal kernel code/data segments - 0x08 and 0x10 respectively,
// but with the last two bits set, making 0x0b and 0x13. The setting of these bits
// sets the RPL (requested privilege level) to 3, meaning that this TSS can be used
// to switch to kernel mode from ring 3.
tss_entry.cs = 0x08 | 0x3;
tss_entry.ss = tss_entry.ds = tss_entry.es = tss_entry.fs = tss_entry.gs = 0x10 | 0x3;
// Here we set the cs, ss, ds, es, fs and gs entries in the TSS.
// These specify what segments should be loaded when the processor
// switches to kernel mode. Therefore they are just our normal
// kernel code/data segments - 0x08 and 0x10 respectively, but with
// the last two bits set, making 0x0b and 0x13. The setting of these
// bits sets the RPL (requested privilege level) to 3, meaning that
// this TSS can be used to switch to kernel mode from ring 3.
tss_entry.cs = 0x08 | 0x3;
tss_entry.ss = tss_entry.ds = tss_entry.es = tss_entry.fs = tss_entry.gs = 0x10 | 0x3;
#elif defined(PLATFORM_X64)
tss_entry.stack0 = stack0;
#endif
}
void SetKernelStack(size_t* stack)
{
#ifdef PLATFORM_X86
tss_entry.esp0 = (uint32_t) stack;
#elif defined(PLATFORM_X64)
tss_entry.stack0 = (uint64_t) stack;
#else
#warning "TSS is not yet supported on this arch!"
while(true);

84
sortix/descriptor_tables.h
View file

@ -42,7 +42,20 @@ namespace Sortix
uint8_t base_high; // The last 8 bits of the base.
} __attribute__((packed));
struct gdt_entry64_struct
{
uint16_t limit_low;
uint16_t base_low;
uint8_t base_middle;
uint8_t access;
uint8_t granularity;
uint8_t base_high;
uint32_t base_highest;
uint32_t zero1;
} __attribute__((packed));
typedef struct gdt_entry_struct gdt_entry_t;
typedef struct gdt_entry64_struct gdt_entry64_t;
// This struct describes a GDT pointer. It points to the start of
// our array of GDT entries, and is in the format required by the
@ -56,42 +69,57 @@ namespace Sortix
typedef struct gdt_ptr_struct gdt_ptr_t;
// A struct describing a Task State Segment.
#ifdef PLATFORM_X86
struct tss_entry_struct
{
uint32_t prev_tss; // The previous TSS - if we used hardware task switching this would form a linked list.
uint32_t esp0; // The stack pointer to load when we change to kernel mode.
uint32_t ss0; // The stack segment to load when we change to kernel mode.
uint32_t esp1; // Unused...
uint32_t ss1;
uint32_t esp2;
uint32_t ss2;
uint32_t cr3;
uint32_t eip;
uint32_t eflags;
uint32_t eax;
uint32_t ecx;
uint32_t edx;
uint32_t ebx;
uint32_t esp;
uint32_t ebp;
uint32_t esi;
uint32_t edi;
uint32_t es; // The value to load into ES when we change to kernel mode.
uint32_t cs; // The value to load into CS when we change to kernel mode.
uint32_t ss; // The value to load into SS when we change to kernel mode.
uint32_t ds; // The value to load into DS when we change to kernel mode.
uint32_t fs; // The value to load into FS when we change to kernel mode.
uint32_t gs; // The value to load into GS when we change to kernel mode.
uint32_t ldt; // Unused...
uint16_t trap;
uint16_t iomap_base;
uint32_t prev_tss; // The previous TSS - if we used hardware task switching this would form a linked list.
uint32_t esp0; // The stack pointer to load when we change to kernel mode.
uint32_t ss0; // The stack segment to load when we change to kernel mode.
uint32_t esp1; // Unused...
uint32_t ss1;
uint32_t esp2;
uint32_t ss2;
uint32_t cr3;
uint32_t eip;
uint32_t eflags;
uint32_t eax;
uint32_t ecx;
uint32_t edx;
uint32_t ebx;
uint32_t esp;
uint32_t ebp;
uint32_t esi;
uint32_t edi;
uint32_t es; // The value to load into ES when we change to kernel mode.
uint32_t cs; // The value to load into CS when we change to kernel mode.
uint32_t ss; // The value to load into SS when we change to kernel mode.
uint32_t ds; // The value to load into DS when we change to kernel mode.
uint32_t fs; // The value to load into FS when we change to kernel mode.
uint32_t gs; // The value to load into GS when we change to kernel mode.
uint32_t ldt; // Unused...
uint16_t trap;
uint16_t iomap_base;
} __attribute__((packed));
#else
struct tss_entry_struct
{
uint32_t reserved1;
uint64_t stack0;
uint64_t stack1;
uint64_t stack2;
uint64_t reserved2;
uint64_t ist[7];
uint64_t reserved3;
uint16_t reserved4;
uint16_t iomap_base;
} __attribute__((packed));
#endif
typedef struct tss_entry_struct tss_entry_t;
void Init();
void SetGate(int32_t num, uint32_t base, uint32_t limit, uint8_t access, uint8_t gran);
void WriteTSS(int32_t num, uint16_t ss0, uint32_t esp0);
void WriteTSS(int32_t num, uint16_t ss0, addr_t stack0);
void SetKernelStack(size_t* stack);
}

43
sortix/x64/gdt.asm
View file

@ -1,43 +0,0 @@
;
; Gdt.s -- contains global descriptor table and interrupt descriptor table
; setup code.
; Based on code from Bran's kernel development tutorials.
; Rewritten for JamesM's kernel development tutorials.
[GLOBAL gdt_flush] ; Allows the C code to call gdt_flush().
gdt_flush:
; TODO: Actually make this stuff work!
mov eax, [esp+4] ; Get the pointer to the GDT, passed as a parameter.
lgdt [eax] ; Load the new GDT pointer
mov ax, 0x10 ; 0x10 is the offset in the GDT to our data segment
mov ds, ax ; Load all data segment selectors
mov es, ax
; mov fs, ax ; TODO: Not on 64-bit!
mov gs, ax
mov ss, ax
; TODO: Not on 64-bit!
; jmp 0x08:.flush ; 0x08 is the offset to our code segment: Far jump!
.flush:
ret
[GLOBAL idt_flush] ; Allows the C code to call idt_flush().
idt_flush:
mov eax, [esp+4] ; Get the pointer to the IDT, passed as a parameter.
lidt [eax] ; Load the IDT pointer.
sti
ret
[GLOBAL tss_flush] ; Allows our C code to call tss_flush().
tss_flush:
mov ax, 0x2B ; Load the index of our TSS structure - The index is
; 0x28, as it is the 5th selector and each is 8 bytes
; long, but we set the bottom two bits (making 0x2B)
; so that it has an RPL of 3, not zero.
ltr ax ; Load 0x2B into the task state register.
ret

71
sortix/x64/gdt.s Normal file
View file

@ -0,0 +1,71 @@
/******************************************************************************
COPYRIGHT(C) JONAS 'SORTIE' TERMANSEN 2011.
This file is part of Sortix.
Sortix is free software: you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later
version.
Sortix is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
details.
You should have received a copy of the GNU General Public License along
with Sortix. If not, see <http://www.gnu.org/licenses/>.
x64/gdt.cpp
Handles initialization of the 64-bit global descriptor table.
******************************************************************************/
.section .text
.global gdt_flush
.type gdt_flush, @function
gdt_flush:
# Load the new GDT pointer
lgdtq (%rdi)
# 0x10 is the offset in the GDT to our data segment
mov $0x10, %ax
mov %ax, %ds
mov %ax, %es
mov %ax, %fs
mov %ax, %gs
# 0x08 is the offset to our code segment: Far jump!
ljmp *GDT_FLUSH_POSTJMP
gdt_flush_postjmp:
ret
.global idt_flush
.type idt_flush, @function
idt_flush:
# Load the IDT pointer.
lidt (%rdi)
# Enable interrupts
sti
ret
.global tss_flush
.type tss_flush, @function
tss_flush:
# Load the index of our TSS structure - The index is 0x28, as it is the 5th
# selector and each is 8 bytes long, but we set the bottom two bits (making
# 0x2B) so that it has an RPL of 3, not zero.
mov $0x2B, %ax
# Load the task state register.
ltr %ax
ret
.section .data
GDT_FLUSH_POSTJMP:
.long gdt_flush_postjmp
.word 0x08