Changed back to lower half kernel, since im dump.

I dont see the benefit of higher half (and could not get multiboot info)
This commit is contained in:
Bananymous 2022-11-15 00:32:07 +02:00
parent 9e933a5ec5
commit d289916bc0
5 changed files with 66 additions and 118 deletions

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@ -6,109 +6,34 @@
.set MB_CHECKSUM, -(MB_MAGIC + MB_FLAGS) #checksum of above, to prove we are multiboot .set MB_CHECKSUM, -(MB_MAGIC + MB_FLAGS) #checksum of above, to prove we are multiboot
# Multiboot header # Multiboot header
.section .multiboot.data, "aw" .section .multiboot
.align 4 .align 4
.long MB_MAGIC .long MB_MAGIC
.long MB_FLAGS .long MB_FLAGS
.long MB_CHECKSUM .long MB_CHECKSUM
# Create stack # Create stack
.section .bootstrap_stack, "aw", @nobits .section .bss
stack_bottom: stack_bottom:
.skip 16384 # 16 KiB .skip 16384 # 16 KiB
stack_top: stack_top:
# Preallocate pages .section .text
.section .bss, "aw", @nobits
.align 4096
boot_page_directory:
.skip 4096
boot_page_table1:
.skip 4096
# Kernel entrypoint
.section .multiboot.text, "a"
.global _start .global _start
.type _start, @function .type _start, @function
_start: _start:
# Physical address of boot_page_table1 movl $stack_top, %esp
movl $(boot_page_table1 - 0xC0000000), %edi
# First address to map is 0 pushl %eax
movl $0, %esi pushl %ebx
# Map 1023 pages, 1024th will be VGA memory call _init
movl $1023, %ecx
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 entry in boot_page_table1 is 4 bytes
addl $4, %edi
# Loop to next entry if we haven't finished
loop 1b
3:
# Map VGA 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 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:
# Now paging is fully set up and enabled
# Unmap the identity mapping since it is not unnecessary
movl $0, boot_page_directory + 0
# Reload crc3 to force a TLB flush for the changes to take effect
movl %cr3, %ecx
movl %ecx, %cr3
# Setup stack
mov $stack_top, %esp
# Call into C code
call kernel_main call kernel_main
# Hang if kernel_main returns
cli cli
1: hlt 1:
hlt
jmp 1b jmp 1b
.size _start, . - _start

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@ -2,37 +2,24 @@ ENTRY(_start)
SECTIONS SECTIONS
{ {
. = 0x00100000; . = 1M;
_kernel_start = .; .text BLOCK(4K) : ALIGN(4K)
.multiboot.data : {
*(.multiboot.data)
}
.multiboot.text : {
*(.multiboot.text)
}
. += 0xC0000000;
.text ALIGN(4K) : AT(ADDR(.text) - 0xC0000000)
{ {
*(.multiboot)
*(.text) *(.text)
} }
.rodata ALIGN(4K) : AT(ADDR(.rodata) - 0xC0000000) .rodata BLOCK(4K) : ALIGN(4K)
{ {
*(.rodata) *(.rodata)
} }
.data ALIGN(4K) : AT(ADDR(.data) - 0xC0000000) .data BLOCK(4K) : ALIGN(4K)
{ {
*(.data) *(.data)
} }
.bss ALIGN(4K) : AT(ADDR(.bss) - 0xC0000000) .bss BLOCK(4K) : ALIGN(4K)
{ {
*(COMMON) *(COMMON)
*(.bss) *(.bss)
*(.bootstrap_stack)
} }
_kernel_end = .;
} }

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@ -7,7 +7,7 @@
static constexpr size_t VGA_WIDTH = 80; static constexpr size_t VGA_WIDTH = 80;
static constexpr size_t VGA_HEIGHT = 25; static constexpr size_t VGA_HEIGHT = 25;
static uint16_t* const VGA_MEMORY = (uint16_t*)0xC03FF000; static uint16_t* const VGA_MEMORY = (uint16_t*)0xB8000;
static size_t terminal_row; static size_t terminal_row;
static size_t terminal_col; static size_t terminal_col;

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@ -3,11 +3,8 @@
#include <stddef.h> #include <stddef.h>
#include <sys/cdefs.h> #include <sys/cdefs.h>
__BEGIN_DECLS
void terminal_initialize(); void terminal_initialize();
void terminal_putchar(char c); void terminal_putchar(char c);
void terminal_write(const char* data, size_t size); void terminal_write(const char* data, size_t size);
void terminal_writestring(const char* data); void terminal_writestring(const char* data);
__END_DECLS

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@ -1,21 +1,60 @@
#include <kernel/GDT.h>
#include <kernel/kmalloc.h>
#include <kernel/panic.h>
#include <kernel/tty.h> #include <kernel/tty.h>
#include <stdio.h> #include <stdio.h>
#include <stdint.h> #include <string.h>
#include <stdlib.h>
#define DISABLE_INTERRUPTS() asm volatile("cli")
#define ENABLE_INTERRUPTS() asm volatile("sti")
// https://www.gnu.org/software/grub/manual/multiboot/multiboot.html#Boot-information-format
struct multiboot_info_t
{
uint32_t flags;
uint32_t mem_lower;
uint32_t mem_upper;
uint32_t boot_device;
uint32_t cmdline;
uint32_t mods_count;
uint32_t mods_addr;
uint32_t syms[4];
uint32_t mmap_length;
uint32_t mmap_addr;
uint32_t drives_length;
uint32_t drives_addr;
uint32_t config_table;
uint32_t boot_loader_name;
uint32_t apm_table;
uint32_t vbe_control_info;
uint32_t vbe_mode_info;
uint16_t vbe_mode;
uint16_t vbe_interface_seg;
uint16_t vbe_interface_off;
uint16_t vbe_interface_len;
uint8_t framebuffer[22];
#if 1
uint8_t color_info[6];
#endif
} __attribute__((packed));
extern "C" extern "C"
void kernel_main() void kernel_main(multiboot_info_t* mbi, uint32_t magic)
{ {
asm volatile("cli"); DISABLE_INTERRUPTS();
terminal_initialize(); terminal_initialize();
if (magic != 0x2BADB002)
Kernel::panic("Invalid magic in multiboot");
if (mbi->flags & 0b00100000)
{
printf("mmap_length: %d\n", mbi->mmap_length);
printf("mmap_addr: %p\n", mbi->mmap_addr);
}
printf("Hello from the kernel!\n"); printf("Hello from the kernel!\n");
printf("%p\n", kernel_main);
int a = 10;
printf("%p\n", &a);
} }