From 448ecd41edd95b86930b5ac7288f2ea9311d476c Mon Sep 17 00:00:00 2001 From: Xander Date: Wed, 28 Jun 2023 21:56:30 +0200 Subject: Reorganizing --- Makefile | 10 +-- arch/x86_64/boot/README.md | 5 ++ arch/x86_64/boot/boot.asm | 163 ++++++++++++++++++++++++++++++++++ arch/x86_64/boot/grub.cfg | 7 ++ arch/x86_64/boot/linker.ld | 16 ++++ arch/x86_64/boot/long_mode_init.asm | 17 ++++ arch/x86_64/boot/multiboot_header.asm | 15 ++++ src/arch/x86_64/boot.asm | 163 ---------------------------------- src/arch/x86_64/grub.cfg | 7 -- src/arch/x86_64/linker.ld | 16 ---- src/arch/x86_64/long_mode_init.asm | 17 ---- src/arch/x86_64/multiboot_header.asm | 15 ---- 12 files changed, 228 insertions(+), 223 deletions(-) create mode 100644 arch/x86_64/boot/README.md create mode 100644 arch/x86_64/boot/boot.asm create mode 100644 arch/x86_64/boot/grub.cfg create mode 100644 arch/x86_64/boot/linker.ld create mode 100644 arch/x86_64/boot/long_mode_init.asm create mode 100644 arch/x86_64/boot/multiboot_header.asm delete mode 100644 src/arch/x86_64/boot.asm delete mode 100644 src/arch/x86_64/grub.cfg delete mode 100644 src/arch/x86_64/linker.ld delete mode 100644 src/arch/x86_64/long_mode_init.asm delete mode 100644 src/arch/x86_64/multiboot_header.asm diff --git a/Makefile b/Makefile index 6d4c9a8..4178a71 100644 --- a/Makefile +++ b/Makefile @@ -2,10 +2,10 @@ arch ?= x86_64 kernel := build/kernel-$(arch).bin iso := build/os-$(arch).iso -linker_script := src/arch/$(arch)/linker.ld -grub_cfg := src/arch/$(arch)/grub.cfg -assembly_source_files := $(wildcard src/arch/$(arch)/*.asm) -assembly_object_files := $(patsubst src/arch/$(arch)/%.asm, \ +linker_script := arch/$(arch)/boot/linker.ld +grub_cfg := arch/$(arch)/boot/grub.cfg +assembly_source_files := $(wildcard arch/$(arch)/boot/*.asm) +assembly_object_files := $(patsubst arch/$(arch)/boot/%.asm, \ build/arch/$(arch)/%.o, $(assembly_source_files)) .PHONY: all clean run iso @@ -31,6 +31,6 @@ $(kernel): $(assembly_object_files) $(linker_script) @ld -n -T $(linker_script) -o $(kernel) $(assembly_object_files) # compile assembly files -build/arch/$(arch)/%.o: src/arch/$(arch)/%.asm +build/arch/$(arch)/%.o: arch/$(arch)/boot/%.asm @mkdir -p $(shell dirname $@) @nasm -felf64 $< -o $@ diff --git a/arch/x86_64/boot/README.md b/arch/x86_64/boot/README.md new file mode 100644 index 0000000..c7cc505 --- /dev/null +++ b/arch/x86_64/boot/README.md @@ -0,0 +1,5 @@ + +Most of the code in this folder is based on Philipp Oppermann's blog os. +https://github.com/phil-opp/blog_os + +Copyright (c) 2019 Philipp Oppermann diff --git a/arch/x86_64/boot/boot.asm b/arch/x86_64/boot/boot.asm new file mode 100644 index 0000000..2e334a8 --- /dev/null +++ b/arch/x86_64/boot/boot.asm @@ -0,0 +1,163 @@ +global start +extern long_mode_start + +section .text +bits 32 +start: + mov esp, stack_top + + call check_multiboot + call check_cpuid + call check_long_mode + + call set_up_page_tables + call enable_paging + + ; load the 64-bit GDT + lgdt [gdt64.pointer] + + jmp gdt64.code:long_mode_start + + ; print `OK` to screen + mov dword [0xb8000], 0x2f4b2f4f + hlt + +check_multiboot: + cmp eax, 0x36d76289 + jne .no_multiboot + ret +.no_multiboot: + mov al, "0" + jmp error + +check_cpuid: + ; Check if CPUID is supported by attempting to flip the ID bit (bit 21) + ; in the FLAGS register. If we can flip it, CPUID is available. + + ; Copy FLAGS in to EAX via stack + pushfd + pop eax + + ; Copy to ECX as well for comparing later on + mov ecx, eax + + ; Flip the ID bit + xor eax, 1 << 21 + + ; Copy EAX to FLAGS via the stack + push eax + popfd + + ; Copy FLAGS back to EAX (with the flipped bit if CPUID is supported) + pushfd + pop eax + + ; Restore FLAGS from the old version stored in ECX (i.e. flipping the + ; ID bit back if it was ever flipped). + push ecx + popfd + + ; Compare EAX and ECX. If they are equal then that means the bit + ; wasn't flipped, and CPUID isn't supported. + cmp eax, ecx + je .no_cpuid + ret +.no_cpuid: + mov al, "1" + jmp error + +check_long_mode: + ; test if extended processor info in available + mov eax, 0x80000000 ; implicit argument for cpuid + cpuid ; get highest supported argument + cmp eax, 0x80000001 ; it needs to be at least 0x80000001 + jb .no_long_mode ; if it's less, the CPU is too old for long mode + + ; use extended info to test if long mode is available + mov eax, 0x80000001 ; argument for extended processor info + cpuid ; returns various feature bits in ecx and edx + test edx, 1 << 29 ; test if the LM-bit is set in the D-register + jz .no_long_mode ; If it's not set, there is no long mode + ret +.no_long_mode: + mov al, "2" + jmp error + +; Prints `ERR: ` and the given error code to screen and hangs. +; parameter: error code (in ascii) in al +error: + mov dword [0xb8000], 0x4f524f45 + mov dword [0xb8004], 0x4f3a4f52 + mov dword [0xb8008], 0x4f204f20 + mov byte [0xb800a], al + hlt + +set_up_page_tables: + ; map first P4 entry to P3 table + mov eax, p3_table + or eax, 0b11 ; present + writable + mov [p4_table], eax + + ; map first P3 entry to P2 table + mov eax, p2_table + or eax, 0b11 ; present + writable + mov [p3_table], eax + + ; map each P2 entry to a huge 2MiB page + mov ecx, 0 ; counter variable +.map_p2_table: + ; map ecx-th P2 entry to a huge page that starts at address 2MiB*ecx + mov eax, 0x200000 ; 2MiB + mul ecx ; start address of ecx-th page + or eax, 0b10000011 ; present + writable + huge + mov [p2_table + ecx * 8], eax ; map ecx-th entry + + inc ecx ; increase counter + cmp ecx, 512 ; if counter == 512, the whole P2 table is mapped + jne .map_p2_table ; else map the next entry + + ret + +enable_paging: + ; load P4 to cr3 register (cpu uses this to access the P4 table) + mov eax, p4_table + mov cr3, eax + + ; enable PAE-flag in cr4 (Physical Address Extension) + mov eax, cr4 + or eax, 1 << 5 + mov cr4, eax + + ; set the long mode bit in the EFER MSR (model specific register) + mov ecx, 0xC0000080 + rdmsr + or eax, 1 << 8 + wrmsr + + ; enable paging in the cr0 register + mov eax, cr0 + or eax, 1 << 31 + mov cr0, eax + + ret + +section .bss +align 4096 +p4_table: + resb 4096 +p3_table: + resb 4096 +p2_table: + resb 4096 +stack_bottom: + resb 64 +stack_top: + +section .rodata +gdt64: + dq 0 ; zero entry +.code: equ $ - gdt64 + dq (1<<43) | (1<<44) | (1<<47) | (1<<53) ; code segment +.pointer: + dw $ - gdt64 - 1 + dq gdt64 diff --git a/arch/x86_64/boot/grub.cfg b/arch/x86_64/boot/grub.cfg new file mode 100644 index 0000000..7c34c9c --- /dev/null +++ b/arch/x86_64/boot/grub.cfg @@ -0,0 +1,7 @@ +set timeout=0 +set default=0 + +menuentry "ats-os" { + multiboot2 /boot/kernel.bin + boot +} diff --git a/arch/x86_64/boot/linker.ld b/arch/x86_64/boot/linker.ld new file mode 100644 index 0000000..5d788f1 --- /dev/null +++ b/arch/x86_64/boot/linker.ld @@ -0,0 +1,16 @@ +ENTRY(start) + +SECTIONS { + . = 1M; + + .boot : + { + /* ensure that the multiboot header is at the beginning */ + *(.multiboot_header) + } + + .text : + { + *(.text) + } +} diff --git a/arch/x86_64/boot/long_mode_init.asm b/arch/x86_64/boot/long_mode_init.asm new file mode 100644 index 0000000..eab3788 --- /dev/null +++ b/arch/x86_64/boot/long_mode_init.asm @@ -0,0 +1,17 @@ +global long_mode_start + +section .text +bits 64 +long_mode_start: + ; load 0 into all data segment registers + mov ax, 0 + mov ss, ax + mov ds, ax + mov es, ax + mov fs, ax + mov gs, ax + + ; print `OKAY` to screen + mov rax, 0x2f592f412f4b2f4f + mov qword [0xb8000], rax + hlt diff --git a/arch/x86_64/boot/multiboot_header.asm b/arch/x86_64/boot/multiboot_header.asm new file mode 100644 index 0000000..9a9289c --- /dev/null +++ b/arch/x86_64/boot/multiboot_header.asm @@ -0,0 +1,15 @@ +section .multiboot_header +header_start: + dd 0xe85250d6 ; magic number (multiboot 2) + dd 0 ; architecture 0 (protected mode i386) + dd header_end - header_start ; header length + ; checksum + dd 0x100000000 - (0xe85250d6 + 0 + (header_end - header_start)) + + ; insert optional multiboot tags here + + ; required end tag + dw 0 ; type + dw 0 ; flags + dd 8 ; size +header_end: diff --git a/src/arch/x86_64/boot.asm b/src/arch/x86_64/boot.asm deleted file mode 100644 index 2e334a8..0000000 --- a/src/arch/x86_64/boot.asm +++ /dev/null @@ -1,163 +0,0 @@ -global start -extern long_mode_start - -section .text -bits 32 -start: - mov esp, stack_top - - call check_multiboot - call check_cpuid - call check_long_mode - - call set_up_page_tables - call enable_paging - - ; load the 64-bit GDT - lgdt [gdt64.pointer] - - jmp gdt64.code:long_mode_start - - ; print `OK` to screen - mov dword [0xb8000], 0x2f4b2f4f - hlt - -check_multiboot: - cmp eax, 0x36d76289 - jne .no_multiboot - ret -.no_multiboot: - mov al, "0" - jmp error - -check_cpuid: - ; Check if CPUID is supported by attempting to flip the ID bit (bit 21) - ; in the FLAGS register. If we can flip it, CPUID is available. - - ; Copy FLAGS in to EAX via stack - pushfd - pop eax - - ; Copy to ECX as well for comparing later on - mov ecx, eax - - ; Flip the ID bit - xor eax, 1 << 21 - - ; Copy EAX to FLAGS via the stack - push eax - popfd - - ; Copy FLAGS back to EAX (with the flipped bit if CPUID is supported) - pushfd - pop eax - - ; Restore FLAGS from the old version stored in ECX (i.e. flipping the - ; ID bit back if it was ever flipped). - push ecx - popfd - - ; Compare EAX and ECX. If they are equal then that means the bit - ; wasn't flipped, and CPUID isn't supported. - cmp eax, ecx - je .no_cpuid - ret -.no_cpuid: - mov al, "1" - jmp error - -check_long_mode: - ; test if extended processor info in available - mov eax, 0x80000000 ; implicit argument for cpuid - cpuid ; get highest supported argument - cmp eax, 0x80000001 ; it needs to be at least 0x80000001 - jb .no_long_mode ; if it's less, the CPU is too old for long mode - - ; use extended info to test if long mode is available - mov eax, 0x80000001 ; argument for extended processor info - cpuid ; returns various feature bits in ecx and edx - test edx, 1 << 29 ; test if the LM-bit is set in the D-register - jz .no_long_mode ; If it's not set, there is no long mode - ret -.no_long_mode: - mov al, "2" - jmp error - -; Prints `ERR: ` and the given error code to screen and hangs. -; parameter: error code (in ascii) in al -error: - mov dword [0xb8000], 0x4f524f45 - mov dword [0xb8004], 0x4f3a4f52 - mov dword [0xb8008], 0x4f204f20 - mov byte [0xb800a], al - hlt - -set_up_page_tables: - ; map first P4 entry to P3 table - mov eax, p3_table - or eax, 0b11 ; present + writable - mov [p4_table], eax - - ; map first P3 entry to P2 table - mov eax, p2_table - or eax, 0b11 ; present + writable - mov [p3_table], eax - - ; map each P2 entry to a huge 2MiB page - mov ecx, 0 ; counter variable -.map_p2_table: - ; map ecx-th P2 entry to a huge page that starts at address 2MiB*ecx - mov eax, 0x200000 ; 2MiB - mul ecx ; start address of ecx-th page - or eax, 0b10000011 ; present + writable + huge - mov [p2_table + ecx * 8], eax ; map ecx-th entry - - inc ecx ; increase counter - cmp ecx, 512 ; if counter == 512, the whole P2 table is mapped - jne .map_p2_table ; else map the next entry - - ret - -enable_paging: - ; load P4 to cr3 register (cpu uses this to access the P4 table) - mov eax, p4_table - mov cr3, eax - - ; enable PAE-flag in cr4 (Physical Address Extension) - mov eax, cr4 - or eax, 1 << 5 - mov cr4, eax - - ; set the long mode bit in the EFER MSR (model specific register) - mov ecx, 0xC0000080 - rdmsr - or eax, 1 << 8 - wrmsr - - ; enable paging in the cr0 register - mov eax, cr0 - or eax, 1 << 31 - mov cr0, eax - - ret - -section .bss -align 4096 -p4_table: - resb 4096 -p3_table: - resb 4096 -p2_table: - resb 4096 -stack_bottom: - resb 64 -stack_top: - -section .rodata -gdt64: - dq 0 ; zero entry -.code: equ $ - gdt64 - dq (1<<43) | (1<<44) | (1<<47) | (1<<53) ; code segment -.pointer: - dw $ - gdt64 - 1 - dq gdt64 diff --git a/src/arch/x86_64/grub.cfg b/src/arch/x86_64/grub.cfg deleted file mode 100644 index 7c34c9c..0000000 --- a/src/arch/x86_64/grub.cfg +++ /dev/null @@ -1,7 +0,0 @@ -set timeout=0 -set default=0 - -menuentry "ats-os" { - multiboot2 /boot/kernel.bin - boot -} diff --git a/src/arch/x86_64/linker.ld b/src/arch/x86_64/linker.ld deleted file mode 100644 index 5d788f1..0000000 --- a/src/arch/x86_64/linker.ld +++ /dev/null @@ -1,16 +0,0 @@ -ENTRY(start) - -SECTIONS { - . = 1M; - - .boot : - { - /* ensure that the multiboot header is at the beginning */ - *(.multiboot_header) - } - - .text : - { - *(.text) - } -} diff --git a/src/arch/x86_64/long_mode_init.asm b/src/arch/x86_64/long_mode_init.asm deleted file mode 100644 index eab3788..0000000 --- a/src/arch/x86_64/long_mode_init.asm +++ /dev/null @@ -1,17 +0,0 @@ -global long_mode_start - -section .text -bits 64 -long_mode_start: - ; load 0 into all data segment registers - mov ax, 0 - mov ss, ax - mov ds, ax - mov es, ax - mov fs, ax - mov gs, ax - - ; print `OKAY` to screen - mov rax, 0x2f592f412f4b2f4f - mov qword [0xb8000], rax - hlt diff --git a/src/arch/x86_64/multiboot_header.asm b/src/arch/x86_64/multiboot_header.asm deleted file mode 100644 index 9a9289c..0000000 --- a/src/arch/x86_64/multiboot_header.asm +++ /dev/null @@ -1,15 +0,0 @@ -section .multiboot_header -header_start: - dd 0xe85250d6 ; magic number (multiboot 2) - dd 0 ; architecture 0 (protected mode i386) - dd header_end - header_start ; header length - ; checksum - dd 0x100000000 - (0xe85250d6 + 0 + (header_end - header_start)) - - ; insert optional multiboot tags here - - ; required end tag - dw 0 ; type - dw 0 ; flags - dd 8 ; size -header_end: -- cgit v1.2.3