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Changess

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This commit is contained in:
vanten-s 2024-11-27 21:57:18 +01:00
parent bb441eaeb6
commit 887429636c
Signed by: vanten-s
GPG key ID: DE3060396884D3F2
16 changed files with 290 additions and 193 deletions
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4
Makefile
View file

@ -31,12 +31,12 @@ LIB_OBJS=\
$(ARCHDIR)/bootstrap.o \
$(ARCHDIR)/tty.o \
$(ARCHDIR)/strlib.o \
$(ARCHDIR)/paging.o \
$(ARCHDIR)/gdt.o \
$(ARCHDIR)/interrupts/idt.o \
$(ARCHDIR)/interrupts/interrupt.o \
$(ARCHDIR)/interrupts/irq0.o \
$(ARCHDIR)/interrupts/syscall.o \
$(ARCHDIR)/gdt.o \
$(ARCHDIR)/userland.o \
$(ARCHDIR)/interrupts/pic.o \
OBJS=$(KERNEL_OBJS) $(LIB_OBJS)

183
arch/i686/bootstrap.s
View file

@ -1,18 +1,12 @@
/* Declare constants for the multiboot header. */
.set ALIGN, 1<<0 /* align loaded modules on page boundaries */
.set MEMINFO, 1<<1 /* provide memory map */
.set FLAGS, ALIGN | MEMINFO /* this is the Multiboot 'flag' field */
.set MAGIC, 0x1BADB002 /* 'magic number' lets bootloader find the header */
.set CHECKSUM, -(MAGIC + FLAGS) /* checksum of above, to prove we are multiboot */
# Declare constants for the multiboot header.
.set ALIGN, 1<<0 # align loaded modules on page boundaries
.set MEMINFO, 1<<1 # provide memory map
.set FLAGS, ALIGN | MEMINFO # this is the Multiboot 'flag' field
.set MAGIC, 0x1BADB002 # 'magic number' lets bootloader find the header
.set CHECKSUM, -(MAGIC + FLAGS) # checksum of above, to prove we are multiboot
/*
Declare a multiboot header that marks the program as a kernel. These are magic
values that are documented in the multiboot standard. The bootloader will
search for this signature in the first 8 KiB of the kernel file, aligned at a
32-bit boundary. The signature is in its own section so the header can be
forced to be within the first 8 KiB of the kernel file.
*/
.section .multiboot
# Declare a multiboot header that marks the program as a kernel.
.section .multiboot.data, "aw"
.align 4
.long MAGIC
.long FLAGS
@ -31,100 +25,109 @@ stack is properly aligned and failure to align the stack will result in
undefined behavior.
*/
.section .bss
.section .bss, "aw", @nobits
.align 16
stack_bottom:
.skip 16384 # 16 KiB
stack_top:
.global boot_page_directory
.align 4096
boot_page_directory:
.skip 4096
boot_page_table1:
.skip 4096
/*
The linker script specifies _start as the entry point to the kernel and the
bootloader will jump to this position once the kernel has been loaded. It
doesn't make sense to return from this function as the bootloader is gone.
*/
.section .text
.section .multiboot.text, "a"
.global _start
.type _start, @function
_start:
/*
The bootloader has loaded us into 32-bit protected mode on a x86
machine. Interrupts are disabled. Paging is disabled. The processor
state is as defined in the multiboot standard. The kernel has full
control of the CPU. The kernel can only make use of hardware features
and any code it provides as part of itself. There's no printf
function, unless the kernel provides its own <stdio.h> header and a
printf implementation. There are no security restrictions, no
safeguards, no debugging mechanisms, only what the kernel provides
itself. It has absolute and complete power over the
machine.
*/
# Physical address of boot_page_table1.
# TODO: I recall seeing some assembly that used a macro to do the
# conversions to and from physical. Maybe this should be done in this
# code as well?
movl $(boot_page_table1 - 0xC0000000), %edi
# First address to map is address 0.
# TODO: Start at the first kernel page instead. Alternatively map the first
# 1 MiB as it can be generally useful, and there's no need to
# specially map the VGA buffer.
movl $0, %esi
# Map 1023 pages. The 1024th will be the VGA text buffer.
movl $1023, %ecx
/*
To set up a stack, we set the esp register to point to the top of the
stack (as it grows downwards on x86 systems). This is necessarily done
in assembly as languages such as C cannot function without a stack.
*/
1:
# Only map the kernel.
cmpl $_kernel_start, %esi
jl 2f
cmpl $(_kernel_end - 0xC0000000), %esi
jge 3f
# Map physical address as "present, writable". Note that this maps
# .text and .rodata as writable. Mind security and map them as non-writable.
movl %esi, %edx
orl $0x003, %edx
movl %edx, (%edi)
2:
# Size of page is 4096 bytes.
addl $4096, %esi
# Size of entries in boot_page_table1 is 4 bytes.
addl $4, %edi
# Loop to the next entry if we haven't finished.
loop 1b
3:
# Map VGA video memory to 0xC03FF000 as "present, writable".
movl $(0x000B8000 | 0x003), boot_page_table1 - 0xC0000000 + 1023 * 4
# The page table is used at both page directory entry 0 (virtually from 0x0
# to 0x3FFFFF) (thus identity mapping the kernel) and page directory entry
# 768 (virtually from 0xC0000000 to 0xC03FFFFF) (thus mapping it in the
# higher half). The kernel is identity mapped because enabling paging does
# not change the next instruction, which continues to be physical. The CPU
# would instead page fault if there was no identity mapping.
# Map the page table to both virtual addresses 0x00000000 and 0xC0000000.
movl $(boot_page_table1 - 0xC0000000 + 0x003), boot_page_directory - 0xC0000000 + 0
movl $(boot_page_table1 - 0xC0000000 + 0x003), boot_page_directory - 0xC0000000 + 768 * 4
# Set cr3 to the address of the boot_page_directory.
movl $(boot_page_directory - 0xC0000000), %ecx
movl %ecx, %cr3
# Enable paging and the write-protect bit.
movl %cr0, %ecx
orl $0x80010000, %ecx
movl %ecx, %cr0
# Jump to higher half with an absolute jump.
lea 4f, %ecx
jmp *%ecx
.section .text
4:
# At this point, paging is fully set up and enabled.
# Unmap the identity mapping as it is now unnecessary.
movl $0, boot_page_directory + 0
# Reload crc3 to force a TLB flush so the changes to take effect.
movl %cr3, %ecx
movl %ecx, %cr3
# Set up the stack.
mov $stack_top, %esp
cli
call gdt_init
movw $0x10, %ax
movw %ax, %ds
movw %ax, %es
movw %ax, %fs
movw %ax, %gs
movw %ax, %ss
# jmp kernel
ljmp $0x08, $kernel
kernel:
/*
This is a good place to initialize crucial processor state before the
high-level kernel is entered. It's best to minimize the early
environment where crucial features are offline. Note that the
processor is not fully initialized yet: Features such as floating
point instructions and instruction set extensions are not initialized
yet. The GDT should be loaded here. Paging should be enabled here.
C++ features such as global constructors and exceptions will require
runtime support to work as well.
*/
/*
Enter the high-level kernel. The ABI requires the stack is 16-byte
aligned at the time of the call instruction (which afterwards pushes
the return pointer of size 4 bytes). The stack was originally 16-byte
aligned above and we've pushed a multiple of 16 bytes to the
stack since (pushed 0 bytes so far), so the alignment has thus been
preserved and the call is well defined.
*/
# Enter the high-level kernel.
call kernel_main
.global keyboard_test
keyboard_test:
hlt
/*
If the system has nothing more to do, put the computer into an
infinite loop. To do that:
1) Disable interrupts with cli (clear interrupt enable in eflags).
They are already disabled by the bootloader, so this is not needed.
Mind that you might later enable interrupts and return from
kernel_main (which is sort of nonsensical to do).
2) Wait for the next interrupt to arrive with hlt (halt instruction).
Since they are disabled, this will lock up the computer.
3) Jump to the hlt instruction if it ever wakes up due to a
non-maskable interrupt occurring or due to system management mode.
*/
# Infinite loop if the system has nothing more to do.
cli
1: hlt
jmp 1b
/*
Set the size of the _start symbol to the current location '.' minus its start.
This is useful when debugging or when you implement call tracing.
*/
.size _start, . - _start

13
arch/i686/interrupts/interrupt.c
View file

@ -30,14 +30,20 @@ __attribute__((interrupt)) void divide_by_zero(struct interrupt_frame*)
__attribute__((interrupt)) void general_protection_fault(struct interrupt_frame*)
{
terminal_writestring("GPF handler called\n");
while (1) { }
while (1) {
asm("cli");
asm("hlt");
}
}
__attribute__((interrupt)) void double_fault(struct interrupt_frame*)
{
stack_trace();
terminal_writestring("2 Errors in a row, u better behave naughty naughty\n");
while (1) { }
while (1) {
asm("cli");
asm("hlt");
}
}
__attribute__((interrupt)) void exception(struct interrupt_frame*)
@ -48,6 +54,7 @@ __attribute__((interrupt)) void exception(struct interrupt_frame*)
__attribute__((interrupt)) void keyboard_interrupt(struct interrupt_frame*)
{
terminal_writestring("Keyboard Interrupt\n");
uint8_t scancode = inb(0x60);
handle_keyboard(scancode);
outb(0x20, 0x20);
@ -55,11 +62,13 @@ __attribute__((interrupt)) void keyboard_interrupt(struct interrupt_frame*)
__attribute__((interrupt)) void irq_1(struct interrupt_frame*)
{
terminal_writestring("PIC 1\n");
outb(0x20, 0x20);
}
__attribute__((interrupt)) void irq_2(struct interrupt_frame*)
{
terminal_writestring("PIC 2\n");
outb(0xA0, 0x20);
outb(0x20, 0x20);
}

46
arch/i686/interrupts/irq0.s
View file

@ -11,30 +11,34 @@
.extern eip
irq0:
push %esp
pusha
push %ebp
push %edx
push %ecx
push %ebx
push %eax
mov $0x10, %eax
mov %ax, %ds
mov %ax, %es
mov %ax, %fs
mov %ax, %gs
call _switch_task
iret
jump_kernel:
pop %eax /* pop return instruction */
mov $0x20, %eax
outb %al, $0x20
pop %eax
pop %ebx
pop %ecx
pop %edx
mov (ss), %eax
mov %ax, %ds
mov %ax, %es
mov %ax, %fs
mov %ax, %gs
pop %ebp
pop %esp
popa
mov (esp), %esp
push (ss)
push (esp)
push (eflags)
push (cs)
push (eip)
@ -42,14 +46,16 @@ push (eip)
iret
jump_user:
pop %eax /* pop return instruction */
mov $0x20, %eax
outb %al, $0x20
pop %eax
pop %ebx
pop %ecx
pop %edx
mov (ss), %eax
mov %ax, %ds
mov %ax, %es
mov %ax, %fs
mov %ax, %gs
pop %ebp
popa
push (ss)
push (esp)

16
arch/i686/interrupts/syscall.s
View file

@ -1,9 +1,20 @@
.extern _syscall
.global syscall
syscall:
sti
mov $0x10, %edx
mov %ax, %ds
mov %ax, %es
mov %ax, %fs
mov %ax, %gs
mov %esp, %edx
mov $0x00f00000, %esp
push 0x10(%edx)
push 0x0C(%edx)
push 0x08(%edx)
push 0x04(%edx)
push 0x00(%edx)
push %edx
push %ecx
push %ebx
push %eax
@ -13,6 +24,5 @@ call _syscall
pop %eax
pop %ebx
pop %ecx
pop %edx
iret

42
arch/i686/linker.ld
View file

@ -6,47 +6,43 @@ ENTRY(_start)
kernel image. */
SECTIONS
{
/* It used to be universally recommended to use 1M as a start offset,
as it was effectively guaranteed to be available under BIOS systems.
However, UEFI has made things more complicated, and experimental data
strongly suggests that 2M is a safer place to load. In 2016, a new
feature was introduced to the multiboot2 spec to inform bootloaders
that a kernel can be loaded anywhere within a range of addresses and
will be able to relocate itself to run from such a loader-selected
address, in order to give the loader freedom in selecting a span of
memory which is verified to be available by the firmware, in order to
work around this issue. This does not use that feature, so 2M was
chosen as a safer option than the traditional 1M. */
. = 2M;
. = 1M;
_kernel_start = .;
.multiboot.data :
{
*(.multiboot.data)
}
/* First put the multiboot header, as it is required to be put very early
in the image or the bootloader won't recognize the file format.
Next we'll put the .text section. */
.text BLOCK (4K) : ALIGN(4K)
.multiboot.text :
{
*(.multiboot.text)
}
. += 0xC0000000;
.text BLOCK (4K) : AT (ADDR (.text) - 0xC0000000)
{
*(.multiboot)
*(.text)
}
/* Read-only data. */
.rodata BLOCK(4K) : ALIGN(4M)
.rodata BLOCK(4K) : AT (ADDR (.rodata) - 0xC0000000)
{
*(.rodata)
}
/* Read-write data (initialized) */
.data BLOCK(4K) : ALIGN(4K)
.data BLOCK(4K) : AT (ADDR (.data) - 0xC0000000)
{
*(.data)
}
/* Read-write data (uninitialized) and stack */
.bss BLOCK(4K) : ALIGN(4K)
.bss BLOCK(4K) : AT (ADDR (.bss) - 0xC0000000)
{
*(COMMON)
*(.bss)
}
/* The compiler may produce other sections, by default it will put them in
a segment with the same name. Simply add stuff here as needed. */
_kernel_end = .;
}

26
arch/i686/paging.c Normal file
View file

@ -0,0 +1,26 @@
#include <stdint.h>
#include <stdbool.h>
#include <stddef.h>
#include <kernel/paging.h>
#include <kernel/tty.h>
struct x86_Page_Directory {
uint32_t address : 20;
uint8_t available_1 : 4;
bool page_Size: 1;
bool available_2: 1;
bool accesed: 1;
bool cache_disable: 1;
bool write_through: 1;
bool user_supervisor: 1;
bool read_write: 1;
bool present: 1;
} __attribute__((packed));
struct x86_Page_Directory page_directory[1024] __attribute__((aligned(4096)));
void setup_paging() {
size_t size = sizeof(page_directory[0]);
}

10
arch/i686/tty.c
View file

@ -60,7 +60,7 @@ void terminal_initialize(void)
terminal_row = 0;
terminal_column = 0;
terminal_color = vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK);
terminal_buffer = (uint16_t*) 0xB8000;
terminal_buffer = (uint16_t*) 0xC03FF000;
for (size_t y = 0; y < VGA_HEIGHT; y++) {
for (size_t x = 0; x < VGA_WIDTH; x++) {
const size_t index = y * VGA_WIDTH + x;
@ -117,11 +117,13 @@ void terminal_putchar(char c)
return;
}
terminal_putentryat(c, terminal_color, terminal_column, terminal_row);
if (++terminal_column == VGA_WIDTH) {
if (++terminal_column >= VGA_WIDTH) {
terminal_column = 0;
if (++terminal_row == VGA_HEIGHT)
terminal_scroll();
terminal_row++;
}
if (terminal_row >= VGA_HEIGHT)
terminal_scroll();
}
static void terminal_write(const char* data, size_t size)

16
arch/i686/userland.s
View file

@ -1,16 +0,0 @@
.global jump_to_userspace
jump_to_userspace:
mov $0x20 | 0x3, %ax
movw %ax, %ds
movw %ax, %es
movw %ax, %fs
movw %ax, %gs
pushl $0x20 | 0x3 /* SS*/
pushl $0x00c00100 /* ESP */
pushf /* EFLAGS */
popl %eax
orl $0x200, %eax
pushl %eax /* Set interrupts */
pushl $0x18 | 0x3 /* CS */
pushl $0x00800000 /* EIP */
iret

2
include/kernel/elf.h
View file

@ -1,5 +1,5 @@
#include <stdint.h>
#include <stddef.h>
void run_program(uint8_t* program, size_t length);
void run_program(uint8_t* code, size_t code_length, uint8_t* data, size_t data_length);

11
include/kernel/paging.h Normal file
View file

@ -0,0 +1,11 @@
#include <stddef.h>
struct PageDirectory {
size_t page_table;
};
struct PageTable {
};
void setup_paging();

2
include/kernel/task.h
View file

@ -9,6 +9,8 @@ struct CPUState {
size_t eip;
size_t esp;
size_t ebp;
size_t edi;
size_t esi;
size_t cs;
size_t ds;
size_t eflags;

13
kernel/elf.c
View file

@ -16,14 +16,17 @@ static void* memcpy(void* restrict dstptr, const void* restrict srcptr, size_t s
extern void jump_to_userspace();
void run_program(uint8_t* program, size_t length)
void run_program(uint8_t* code, size_t code_length, uint8_t* data, size_t data_length)
{
uint8_t* userland_code = (uint8_t*) 0x00800000;
memcpy(userland_code, program, length);
uint8_t* userland_code = (uint8_t*) 0x00000000;
uint8_t* userland_data = (uint8_t*) 0x00800000;
memcpy(userland_code, code, code_length);
memcpy(userland_data, data, data_length);
struct CPUState target = {
.eip = (size_t) userland_code,
.esp = 0x00c00100,
.esp = 0x00000000,
.eax = 0,
.ebx = 0,
.ecx = 0,
@ -31,7 +34,7 @@ void run_program(uint8_t* program, size_t length)
.cs = 0x18 | 0x3,
.ds = 0x20 | 0x3,
.eflags = 0x0200,
.ebp = 0x00c00100,
.ebp = 0x00c00f00,
};
struct Task task = {

20
kernel/kernel.c
View file

@ -4,6 +4,7 @@
#include <kernel/pic.h>
#include <kernel/heap.h>
#include <kernel/task.h>
#include <kernel/paging.h>
#include <debugging.h>
@ -13,33 +14,36 @@
#endif
uint8_t program[] = {
0xba, 0x01, 0x00, 0x00, 0x00, // mov 1, %edx
0xb8, 0xff, 0x00, 0x80, 0x00, // mov $buffer, %eax
// 0xba, 0x01, 0x00, 0x00, 0x00, // mov 1, %edx
0xb8, 0x00, 0x00, 0xC0, 0x00, // mov $buffer, %eax
// 0xcd, 0x80, // int 0x80
0xb9, 0x00, 0x00, 0x00, 0x00, // mov 0, %ecx
0xcd, 0x80, // int 0x80
0xba, 0x00, 0x00, 0x00, 0x00, // mov 0, %edx
0xcd, 0x80, // int 0x80
0xcd, 0x20, // int 0x20
0xb9, 0x00, 0x00, 0x80, 0x00, // mov $start, %ecx
0xff, 0xe1, // jmp *%ecx
};
uint8_t data[] = "Hello From Userspace\n";
void kernel_main(void)
{
/* Initialize terminal interface */
terminal_initialize();
terminal_writestring("Hello from Kernelspace\n");
idt_init();
init_pic();
heap_init();
setup_tasks();
setup_paging();
asm("sti");
run_program(program, sizeof(program));
run_program(program, sizeof(program), data, sizeof(data));
while (true) {
asm("hlt");
terminal_writestring("Hello from Kernelspace\n");
}
}

5
kernel/syscall.c
View file

@ -9,6 +9,7 @@ static void print(char* buffer)
static void input(char* buffer)
{
terminal_writestring("Input: ");
while (true) {
for (size_t i = 0; i < keyboard_buffer_top; i++) {
buffer[i] = keyboard_buffer[i];
@ -22,9 +23,9 @@ static void input(char* buffer)
}
}
void _syscall(uint32_t a, uint32_t b, uint32_t c, uint32_t d)
void _syscall(uint32_t a, uint32_t b, uint32_t c)
{
switch (d) {
switch (c) {
case 0x00:
print((char*) a);
break;

74
kernel/task.c
View file

@ -1,5 +1,6 @@
#include <kernel/task.h>
#include <kernel/heap.h>
#include <kernel/tty.h>
struct Task* tasks;
size_t tasks_capacity;
@ -16,6 +17,7 @@ void setup_tasks()
void add_task(struct Task task)
{
asm("cli");
if (num_tasks == tasks_capacity) {
struct Task* temp = malloc(sizeof(*tasks) * tasks_capacity * 2);
@ -31,6 +33,7 @@ void add_task(struct Task task)
tasks[num_tasks] = task;
num_tasks++;
asm("sti");
}
size_t ss;
@ -39,8 +42,26 @@ size_t eflags;
size_t cs;
size_t eip;
void jump_kernel(size_t eax, size_t ebx, size_t ecx, size_t edx, size_t ebp, size_t esp);
void jump_user(size_t eax, size_t ebx, size_t ecx, size_t edx, size_t ebp);
void jump_kernel(
size_t edi,
size_t esi,
size_t ebp,
size_t esp,
size_t ebx,
size_t edx,
size_t ecx,
size_t eax
);
void jump_user(
size_t edi,
size_t esi,
size_t ebp,
size_t esp,
size_t ebx,
size_t edx,
size_t ecx,
size_t eax
);
static void save_state(
size_t eax,
@ -51,6 +72,9 @@ static void save_state(
size_t esp,
size_t ebp,
size_t esi,
size_t edi,
size_t eip,
size_t cs,
@ -69,6 +93,9 @@ static void save_state(
.eip = eip,
.esi = esi,
.edi = edi,
.cs = cs,
.ds = ds,
@ -91,21 +118,39 @@ void next_task() {
eip = s.eip;
if ((cs & 3) == 0) {
jump_kernel(s.eax, s.ebx, s.ecx, s.edx, s.ebp, s.esp);
jump_kernel(
s.edi,
s.esi,
s.ebp,
s.esp,
s.ebx,
s.edx,
s.ecx,
s.eax
);
} else {
jump_user(s.eax, s.ebx, s.ecx, s.edx, s.ebp);
jump_user(
s.edi,
s.esi,
s.ebp,
s.esp,
s.ebx,
s.edx,
s.ecx,
s.eax
);
}
}
void _switch_task(
size_t eax,
size_t ebx,
size_t ecx,
size_t edx,
size_t edi,
size_t esi,
size_t ebp,
size_t esp_current,
size_t ebx,
size_t edx,
size_t ecx,
size_t eax,
size_t eip_passed,
size_t cs_passed,
@ -114,6 +159,7 @@ void _switch_task(
size_t ds_passed
)
{
terminal_writestring("Switching task\n");
if (num_tasks == 0) {
return;
};
@ -127,13 +173,7 @@ void _switch_task(
esp_current = esp_passed;
}
ss = ds_passed;
esp = esp_passed;
eflags = eflags_passed;
cs = cs_passed;
eip = eip_passed;
save_state(eax, ebx, ecx, edx, esp, ebp, eip_passed, cs_passed, ds, eflags_passed);
save_state(eax, ebx, ecx, edx, esp_current, ebp, esi, edi, eip_passed, cs_passed, ds, eflags_passed);
next_task();
}