mirror of
https://github.com/LadybirdBrowser/ladybird.git
synced 2024-11-26 01:20:25 +00:00
Kernel: Use a multiboot header instead of a convoluted two-part bootloader.
The old bootloader was hilariously complicated, requiring a floppy disk with the kernel on it, and a hard drive with the file system. This patch removes the floppy disk from the equation and replaces it with a multiboot header. This means the kernel can now be booted with qemu-system-i386 -kernel kernel
This commit is contained in:
Andreas Kling
parent
d5a9f4596b
commit
ee4d7c18c8
Notes:
sideshowbarker
2024-07-19 14:51:34 +09:00
Author: https://github.com/awesomekling Commit: https://github.com/SerenityOS/serenity/commit/ee4d7c18c8a
7 changed files with 81 additions and 293 deletions
3
Kernel/.gitignore
vendored
3
Kernel/.gitignore
vendored
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@ -1,7 +1,6 @@
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*.o
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*.d
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.floppy-image
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Boot/boot.bin
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Boot/boot.ao
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kernel
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kernel.map
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_fs_contents
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64
Kernel/Boot/boot.S
Normal file
64
Kernel/Boot/boot.S
Normal file
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@ -0,0 +1,64 @@
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.set MULTIBOOT_MAGIC, 0x1badb002
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.set MULTIBOOT_PAGE_ALIGN, 0x1
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.set MULTIBOOT_MEMORY_INFO, 0x2
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.set MULTIBOOT_VIDEO_MODE, 0x4
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.set multiboot_flags, MULTIBOOT_PAGE_ALIGN | MULTIBOOT_MEMORY_INFO | MULTIBOOT_VIDEO_MODE
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.set multiboot_checksum, -(MULTIBOOT_MAGIC + multiboot_flags)
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.section .multiboot
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.align 4
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.long MULTIBOOT_MAGIC
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.long multiboot_flags
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.long multiboot_checksum
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/* for MULTIBOOT_MEMORY_INFO */
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.long 0x00000000 /* header_addr */
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.long 0x00000000 /* load_addr */
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.long 0x00000000 /* load_end_addr */
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.long 0x00000000 /* bss_end_addr */
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.long 0x00000000 /* entry_addr */
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/* for MULTIBOOT_VIDEO_MODE */
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.long 0x00000000 /* mode_type */
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.long 0 /* width */
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.long 0 /* height */
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.long 32 /* depth */
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.section .stack, "aw", @nobits
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stack_bottom:
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.skip 32768
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stack_top:
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.section .text
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.global start
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.type start, @function
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.extern init
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.type init, @function
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start:
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mov $stack_top, %esp
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and $-16, %esp
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pushl %esp
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pushl %eax /* Multiboot header magic */
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pushl %ebx /* Multiboot header pointer */
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cli
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call init
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pushl $exit_message
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call kprintf
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cli
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loop:
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hlt
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jmp loop
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exit_message:
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.asciz "Kernel exited."
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@ -1,252 +0,0 @@
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; asmsyntax=nasm
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[org 0x7c00]
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[bits 16]
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boot:
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cli
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mov ax, 0x8000
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mov ss, ax
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mov sp, 0xffff
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push cs
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pop ds
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xor bx, bx
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mov ah, 0x0e
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mov si, message
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lodsb
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.lewp:
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int 0x10
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lodsb
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cmp al, 0
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jne .lewp
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; Enable A20
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mov ax, 0x2401
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int 0x15
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; HACK: Load the ELF kernel at 0xf000. Assuming that the first
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; LOAD header has a file offset of 0x1000, this puts _start
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; at 0x10000 which we jump to later.
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; This is all quite rickety.
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mov bx, 0xf00
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mov es, bx
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xor bx, bx
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mov cx, word [cur_lba]
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.sector_loop:
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call convert_lba_to_chs
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mov ah, 0x02 ; cmd 0x02 - Read Disk Sectors
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mov al, 1 ; 1 sector at a time
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mov dl, 0 ; drive 0 (fd0)
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int 0x13
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jc fug
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mov ah, 0x0e
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mov al, '.'
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int 0x10
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inc word [cur_lba]
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mov cx, word [cur_lba]
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cmp cx, 900
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jz .sector_loop_end
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mov bx, es
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add bx, 0x20
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mov es, bx
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xor bx, bx
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jmp .sector_loop
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.sector_loop_end:
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call durk
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; Turn off the floppy motor.
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mov dx, 0x3f2
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xor al, al
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out dx, al
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; Let's look at the ELF header.
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mov bx, 0xf00
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mov fs, bx
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cmp [fs:0], dword 0x464c457f ; ELF magic: { 0x7f "ELF" }
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jne fug
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cmp [fs:24], dword 0x10000 ; Entry should be 0x10000
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jne fug
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mov ebx, dword [fs:28] ; EBX <- program header table
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mov ecx, dword [fs:44] ; ECX <- program header count
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; Let's find the BSS and clear it.
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parse_program_header:
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cmp [fs:ebx], dword 0x1 ; Is Load segment?
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jne .next
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cmp [fs:ebx+24], dword 0x6 ; Is read+write but not execute?
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jne .next
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mov edi, [fs:ebx+8] ; EDI <- p_vaddr
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add edi, [fs:ebx+16] ; skip over 'p_filesz' bytes (leave them intact)
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push ecx
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sub edi, [fs:ebx+16] ; skip over 'p_filesz' bytes (see above)
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; Since we're in 16-bit real mode, create a segment address.
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mov eax, edi
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shr eax, 4
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mov es, ax
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and edi, 0xf
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mov ecx, [fs:ebx+20] ; ECX <- p_memsz
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xor al, al
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rep stosb
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pop ecx
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.next:
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add ebx, 32
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loop parse_program_header
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; Okay we're all set to go!
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lets_go:
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lgdt [cs:test_gdt_ptr]
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mov eax, cr0
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or al, 1
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mov cr0, eax
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jmp 0x08:pmode
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durk:
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push cs
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pop ds
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xor bx, bx
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mov ah, 0x0e
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mov si, msg_sectors_loaded
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lodsb
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.lewp:
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int 0x10
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lodsb
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cmp al, 0
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jne .lewp
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ret
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pmode:
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[bits 32]
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mov ax, 0x10
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mov ds, ax
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mov es, ax
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mov fs, ax
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mov gs, ax
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mov ss, ax
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mov esp, 0x4000
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xor eax, eax
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xor ebx, ebx
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xor ecx, ecx
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xor edx, edx
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xor ebp, ebp
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xor esi, esi
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xor edi, edi
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jmp 0x10000
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hlt
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test_gdt_ptr:
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dw (test_gdt_end-test_gdt)
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dd test_gdt
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test_gdt:
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dd 0
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dd 0
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dd 0x0000ffff
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dd 0x00cf9a00
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dd 0x0000ffff
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dd 0x00cf9200
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dd 0
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dd 0
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dd 0
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dd 0
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test_gdt_end:
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[bits 16]
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fug:
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xor bx, bx
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mov ah, 0x0e
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mov si, fug_message
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lodsb
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.lewp:
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int 0x10
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lodsb
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cmp al, 0
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jne .lewp
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cli
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hlt
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; Input:
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;
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; AX = LBA
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;
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; Output:
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;
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; CX and DH = C/H/S address formatted for Int13,2
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; CL = sector (LBA % sectors_per_track) + 1
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;
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; 1.44M floppy stats:
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; (sectors_per_track: 18)
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; (heads: 2)
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; (sectors: 2880)
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convert_lba_to_chs:
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mov ax, cx
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; AX = LBA/spt, DX = LBA%spt
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xor dx, dx
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div word [sectors_per_track]
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; CL = sector (LBA % sectors_per_track) + 1
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mov cl, dl
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inc cl
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; CH = track (LBA / sectors_per_track) / heads
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mov ch, al
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shr ch, 1
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; AX = (LBA/spt)/heads, DX = (LBA/spt)%heads
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xor dx, dx
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div word [heads]
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; DH = sector (LBA / sectors_per_track) % heads
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mov dh, dl
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ret
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cur_lba:
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dw 1
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sectors_per_track:
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dw 18
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heads:
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dw 2
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msg_sectors_loaded:
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db "done!", 0x0d, 0x0a, 0
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message:
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db "Loading kernel", 0
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fug_message:
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db "FUG!", 0x0d, 0x0a, 0
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times 510-($-$$) db 0
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dw 0xaa55
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@ -1,5 +1,4 @@
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KERNEL_OBJS = \
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_start.o \
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init.o \
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kmalloc.o \
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StdLib.o \
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@ -65,12 +64,10 @@ AK_OBJS = \
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../AK/FileSystemPath.o \
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../AK/StdLibExtras.o
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OBJS = $(KERNEL_OBJS) $(VFS_OBJS) $(AK_OBJS)
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CXX_OBJS = $(KERNEL_OBJS) $(VFS_OBJS) $(AK_OBJS)
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OBJS = $(CXX_OBJS) Boot/boot.ao
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NASM = nasm
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KERNEL = kernel
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BOOTLOADER = Boot/boot.bin
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IMAGE = .floppy-image
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ARCH_FLAGS =
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STANDARD_FLAGS = -std=c++17 -nostdinc++ -nostdlib -nostdinc
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KERNEL_FLAGS =
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@ -87,9 +84,10 @@ CXXFLAGS = -MMD -MP $(WARNING_FLAGS) $(OPTIMIZATION_FLAGS) $(KERNEL_FLAGS) $(FLA
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#CXX = clang $(CLANG_FLAGS)
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CXX = i686-elf-g++
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LD = i686-elf-ld
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AS = i686-elf-as
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LDFLAGS = -T linker.ld
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all: $(KERNEL) $(IMAGE) kernel.map
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all: $(KERNEL) kernel.map
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kernel.map: kernel
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@echo "MKMAP $@"; sh mkmap.sh
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@ -97,20 +95,14 @@ kernel.map: kernel
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$(KERNEL): $(OBJS)
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@echo "LD $@"; $(LD) $(LDFLAGS) -o $@ -Ttext 0x10000 $(OBJS)
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$(IMAGE): $(KERNEL) $(BOOTLOADER)
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@echo "CREATE $@"; cat $(BOOTLOADER) $(KERNEL) > .tmp-floppy-image
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@dd if=/dev/zero bs=2M count=1 >> .tmp-floppy-image 2> /dev/null
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@dd if=.tmp-floppy-image of=.floppy-image bs=1440k count=1 2>/dev/null
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@rm -f .tmp-floppy-image
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$(BOOTLOADER): Boot/boot.asm
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@echo "NASM $<"; $(NASM) -f bin -o $@ $<
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.cpp.o:
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@echo "CXX $<"; $(CXX) $(CXXFLAGS) -o $@ -c $<
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-include $(OBJS:%.o=%.d)
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%.ao: %.S
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@echo "AS $@"; $(AS) -o $@ $<
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-include $(CXX_OBJS:%.o=%.d)
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clean:
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@echo "CLEAN"; rm -f $(KERNEL) $(OBJS) $(BOOTLOADER) $(IMAGE) *.d
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@echo "CLEAN"; rm -f $(KERNEL) $(OBJS) *.d
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@ -136,7 +136,7 @@ VFS* vfs;
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ASSERT_NOT_REACHED();
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}
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[[noreturn]] void init()
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extern "C" [[noreturn]] void init()
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{
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cli();
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@ -1,44 +1,29 @@
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/* The bootloader will look at this image and start execution at the symbol
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designated as the entry point. */
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ENTRY(_start)
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ENTRY(start)
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/* Tell where the various sections of the object files will be put in the final
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kernel image. */
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SECTIONS
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{
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/* Begin putting sections at 1 MiB, a conventional place for kernels to be
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loaded at by the bootloader. */
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. = 0x10000;
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/* First put the multiboot header, as it is required to be put very early
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early in the image or the bootloader won't recognize the file format.
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Next we'll put the .text section. */
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.text BLOCK(4K) : ALIGN(4K)
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{
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_start.o
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Boot/boot.ao
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*(.multiboot)
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*(.text)
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}
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/* Read-only data. */
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.rodata BLOCK(4K) : ALIGN(4K)
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{
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*(.rodata)
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}
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/* Read-write data (initialized) */
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.data BLOCK(4K) : ALIGN(4K)
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{
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*(.data)
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}
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/* Read-write data (uninitialized) and stack */
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.bss BLOCK(4K) : ALIGN(4K)
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{
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*(COMMON)
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*(.bss)
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}
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/* The compiler may produce other sections, by default it will put them in
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a segment with the same name. Simply add stuff here as needed. */
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}
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@ -7,17 +7,17 @@ if [ "$1" = "b" ]; then
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bochs -q -f .bochsrc
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elif [ "$1" = "qn" ]; then
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# ./run qn: qemu without network
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qemu-system-i386 -s -m $ram_size -device e1000 -drive format=raw,file=.floppy-image,if=floppy -drive format=raw,file=_fs_contents #$@
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qemu-system-i386 -s -m $ram_size -device e1000 -kernel kernel -hda _fs_contents
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elif [ "$1" = "qtap" ]; then
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# ./run qtap: qemu with tap
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sudo qemu-system-i386 -s -m $ram_size -object filter-dump,id=hue,netdev=br0,file=e1000.pcap -netdev tap,ifname=tap0,id=br0 -device e1000,netdev=br0 -drive format=raw,file=.floppy-image,if=floppy -drive format=raw,file=_fs_contents
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sudo qemu-system-i386 -s -m $ram_size -object filter-dump,id=hue,netdev=br0,file=e1000.pcap -netdev tap,ifname=tap0,id=br0 -device e1000,netdev=br0 -kernel kernel -hda _fs_contents
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else
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# ./run: qemu with user networking
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qemu-system-i386 -s -m $ram_size \
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-object filter-dump,id=hue,netdev=breh,file=e1000.pcap \
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-netdev user,id=breh,hostfwd=tcp:127.0.0.1:8888-192.168.5.2:8888 \
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-device e1000,netdev=breh \
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-drive format=raw,file=.floppy-image,if=floppy \
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-drive format=raw,file=_fs_contents
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-kernel kernel \
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-hda _fs_contents
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fi
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