From a9f29cfe168f634434047b55ab16b760e9020680 Mon Sep 17 00:00:00 2001 From: Aleksa Vučković Date: Wed, 6 Oct 2021 23:32:15 +0200 Subject: newlines and scrolling --- Makefile | 13 +++--- README.md | 11 +++++- boot.asm | 90 ------------------------------------------ boot.s | 109 --------------------------------------------------- grub.cfg | 3 -- kernel.c | 114 ----------------------------------------------------- linker.ld | 43 -------------------- src/boot.asm | 90 ++++++++++++++++++++++++++++++++++++++++++ src/boot.s | 109 +++++++++++++++++++++++++++++++++++++++++++++++++++ src/grub.cfg | 3 ++ src/kernel.c | 124 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ src/linker.ld | 43 ++++++++++++++++++++ 12 files changed, 386 insertions(+), 366 deletions(-) delete mode 100644 boot.asm delete mode 100644 boot.s delete mode 100644 grub.cfg delete mode 100644 kernel.c delete mode 100644 linker.ld create mode 100644 src/boot.asm create mode 100644 src/boot.s create mode 100644 src/grub.cfg create mode 100644 src/kernel.c create mode 100644 src/linker.ld diff --git a/Makefile b/Makefile index f3f5b47..56ffd05 100644 --- a/Makefile +++ b/Makefile @@ -1,3 +1,4 @@ +SOURCE_DIR=src BUILD_DIR=build ISO_DIR=isodir @@ -6,20 +7,20 @@ all: $(BUILD_DIR)/myos.bin grub-file --is-x86-multiboot $(BUILD_DIR)/myos.bin mkdir -p $(ISO_DIR)/boot/grub cp $(BUILD_DIR)/myos.bin $(ISO_DIR)/boot/myos.bin - cp grub.cfg $(ISO_DIR)/boot/grub/grub.cfg + cp $(SOURCE_DIR)/grub.cfg $(ISO_DIR)/boot/grub/grub.cfg grub-mkrescue -o myos.iso $(ISO_DIR) -$(BUILD_DIR)/boot.o: boot.s +$(BUILD_DIR)/boot.o: $(SOURCE_DIR)/boot.s mkdir -p $(BUILD_DIR) - i686-elf-as boot.s -o $(BUILD_DIR)/boot.o + i686-elf-as $(SOURCE_DIR)/boot.s -o $(BUILD_DIR)/boot.o -$(BUILD_DIR)/kernel.o: kernel.c +$(BUILD_DIR)/kernel.o: $(SOURCE_DIR)/kernel.c mkdir -p $(BUILD_DIR) - i686-elf-gcc -c kernel.c -o $(BUILD_DIR)/kernel.o -std=gnu99 -ffreestanding -O2 -Wall -Wextra + i686-elf-gcc -c $(SOURCE_DIR)/kernel.c -o $(BUILD_DIR)/kernel.o -std=gnu99 -ffreestanding -O2 -Wall -Wextra $(BUILD_DIR)/myos.bin: $(BUILD_DIR)/kernel.o $(BUILD_DIR)/boot.o mkdir -p $(BUILD_DIR) - i686-elf-gcc -T linker.ld -o $(BUILD_DIR)/myos.bin -ffreestanding -O2 -nostdlib $(BUILD_DIR)/boot.o $(BUILD_DIR)/kernel.o -lgcc + i686-elf-gcc -T $(SOURCE_DIR)/linker.ld -o $(BUILD_DIR)/myos.bin -ffreestanding -O2 -nostdlib $(BUILD_DIR)/boot.o $(BUILD_DIR)/kernel.o -lgcc .PHONY: clean clean: diff --git a/README.md b/README.md index d4fecca..917cdb3 100644 --- a/README.md +++ b/README.md @@ -1 +1,10 @@ -# mykernel \ No newline at end of file +# mykernel + +## i686-elf cross compiler +First install binutils and gcc from your package manager. +On Arch based distributions they are available in AUR: +- [binutils](https://aur.archlinux.org/packages/i686-elf-binutils/) +- [gcc](https://aur.archlinux.org/packages/i686-elf-gcc/) + +## Bare bones kernel in as and C +[osdev](https://wiki.osdev.org/Bare_Bones) diff --git a/boot.asm b/boot.asm deleted file mode 100644 index 94b4c57..0000000 --- a/boot.asm +++ /dev/null @@ -1,90 +0,0 @@ -; Declare constants for the multiboot header. -MBALIGN equ 1 << 0 ; align loaded modules on page boundaries -MEMINFO equ 1 << 1 ; provide memory map -FLAGS equ MBALIGN | MEMINFO ; this is the Multiboot 'flag' field -MAGIC equ 0x1BADB002 ; 'magic number' lets bootloader find the header -CHECKSUM equ -(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 -align 4 - dd MAGIC - dd FLAGS - dd CHECKSUM - -; The multiboot standard does not define the value of the stack pointer register -; (esp) and it is up to the kernel to provide a stack. This allocates room for a -; small stack by creating a symbol at the bottom of it, then allocating 16384 -; bytes for it, and finally creating a symbol at the top. The stack grows -; downwards on x86. The stack is in its own section so it can be marked nobits, -; which means the kernel file is smaller because it does not contain an -; uninitialized stack. The stack on x86 must be 16-byte aligned according to the -; System V ABI standard and de-facto extensions. The compiler will assume the -; stack is properly aligned and failure to align the stack will result in -; undefined behavior. -section .bss -align 16 -stack_bottom: -resb 16384 ; 16 KiB -stack_top: - -; 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. -; Declare _start as a function symbol with the given symbol size. -section .text -global _start:function (_start.end - _start) -_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 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. - - ; To set up a stack, we set the esp register to point to the top of our - ; stack (as it grows downwards on x86 systems). This is necessarily done - ; in assembly as languages such as C cannot function without a stack. - mov esp, stack_top - - ; 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 isnot 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 since pushed a multiple of 16 bytes to the - ; stack since (pushed 0 bytes so far) and the alignment is thus - ; preserved and the call is well defined. - ; note, that if you are building on Windows, C functions may have "_" prefix in assembly: _kernel_main - extern kernel_main - call kernel_main - - ; 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. - cli -.hang: hlt - jmp .hang -.end: diff --git a/boot.s b/boot.s deleted file mode 100644 index 172fd14..0000000 --- a/boot.s +++ /dev/null @@ -1,109 +0,0 @@ -/* 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 -.align 4 -.long MAGIC -.long FLAGS -.long CHECKSUM - -/* -The multiboot standard does not define the value of the stack pointer register -(esp) and it is up to the kernel to provide a stack. This allocates room for a -small stack by creating a symbol at the bottom of it, then allocating 16384 -bytes for it, and finally creating a symbol at the top. The stack grows -downwards on x86. The stack is in its own section so it can be marked nobits, -which means the kernel file is smaller because it does not contain an -uninitialized stack. The stack on x86 must be 16-byte aligned according to the -System V ABI standard and de-facto extensions. The compiler will assume the -stack is properly aligned and failure to align the stack will result in -undefined behavior. -*/ -.section .bss -.align 16 -stack_bottom: -.skip 16384 # 16 KiB -stack_top: - -/* -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 -.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 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. - */ - - /* - 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. - */ - mov $stack_top, %esp - - /* - 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 instuctions 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. - */ - call kernel_main - - /* - 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. - */ - 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 diff --git a/grub.cfg b/grub.cfg deleted file mode 100644 index b2f8404..0000000 --- a/grub.cfg +++ /dev/null @@ -1,3 +0,0 @@ -menuentry "myos" { - multiboot /boot/myos.bin -} diff --git a/kernel.c b/kernel.c deleted file mode 100644 index 0516f16..0000000 --- a/kernel.c +++ /dev/null @@ -1,114 +0,0 @@ -#include -#include -#include - -/* Check if the compiler thinks you are targeting the wrong operating system. */ -#if defined(__linux__) -#error "You are not using a cross-compiler, you will most certainly run into trouble" -#endif - -/* This tutorial will only work for the 32-bit ix86 targets. */ -#if !defined(__i386__) -#error "This tutorial needs to be compiled with a ix86-elf compiler" -#endif - -/* Hardware text mode color constants. */ -enum vga_color { - VGA_COLOR_BLACK = 0, - VGA_COLOR_BLUE = 1, - VGA_COLOR_GREEN = 2, - VGA_COLOR_CYAN = 3, - VGA_COLOR_RED = 4, - VGA_COLOR_MAGENTA = 5, - VGA_COLOR_BROWN = 6, - VGA_COLOR_LIGHT_GREY = 7, - VGA_COLOR_DARK_GREY = 8, - VGA_COLOR_LIGHT_BLUE = 9, - VGA_COLOR_LIGHT_GREEN = 10, - VGA_COLOR_LIGHT_CYAN = 11, - VGA_COLOR_LIGHT_RED = 12, - VGA_COLOR_LIGHT_MAGENTA = 13, - VGA_COLOR_LIGHT_BROWN = 14, - VGA_COLOR_WHITE = 15, -}; - -static inline uint8_t vga_entry_color(enum vga_color fg, enum vga_color bg) -{ - return fg | bg << 4; -} - -static inline uint16_t vga_entry(unsigned char uc, uint8_t color) -{ - return (uint16_t) uc | (uint16_t) color << 8; -} - -size_t strlen(const char* str) -{ - size_t len = 0; - while (str[len]) - len++; - return len; -} - -static const size_t VGA_WIDTH = 80; -static const size_t VGA_HEIGHT = 25; - -size_t terminal_row; -size_t terminal_column; -uint8_t terminal_color; -uint16_t* terminal_buffer; - -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; - 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; - terminal_buffer[index] = vga_entry(' ', terminal_color); - } - } -} - -void terminal_setcoor(uint8_t color) -{ - terminal_color = color; -} - -void terminal_putentryat(char c, uint8_t color, size_t x, size_t y) -{ - const size_t index = y * VGA_WIDTH + x; - terminal_buffer[index] = vga_entry(c, color); -} - -void terminal_putchar(char c) -{ - terminal_putentryat(c, terminal_color, terminal_column, terminal_row); - if (++terminal_column == VGA_WIDTH) { - terminal_column = 0; - if (++terminal_row == VGA_HEIGHT) - terminal_row = 0; - } -} - -void terminal_write(const char* data, size_t size) -{ - for (size_t i = 0; i < size; i++) - terminal_putchar(data[i]); -} - -void terminal_writestring(const char* data) -{ - terminal_write(data, strlen(data)); -} - -void kernel_main(void) -{ - /* Initialize terminal interface */ - terminal_initialize(); - - /* Newline support is left as an exercise. */ - terminal_writestring("Hello, kernel World!\n"); -} diff --git a/linker.ld b/linker.ld deleted file mode 100644 index 38ddd94..0000000 --- a/linker.ld +++ /dev/null @@ -1,43 +0,0 @@ -/* The bootloader will look at this image and start execution at the symbol - designated as the entry point. */ -ENTRY(_start) - -/* Tell where the various sections of the object files will be put in the final - kernel image. */ -SECTIONS -{ - /* Begin putting sections at 1 MiB, a conventional place for kernels to be - loaded at by the bootloader. */ - . = 1M; - - /* First put the multiboot header, as it is required to be put very early - 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) - } - - /* Read-only data. */ - .rodata BLOCK(4K) : ALIGN(4K) - { - *(.rodata) - } - - /* Read-write data (initialized) */ - .data BLOCK(4K) : ALIGN(4K) - { - *(.data) - } - - /* Read-write data (uninitialized) and stack */ - .bss BLOCK(4K) : ALIGN(4K) - { - *(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. */ -} diff --git a/src/boot.asm b/src/boot.asm new file mode 100644 index 0000000..94b4c57 --- /dev/null +++ b/src/boot.asm @@ -0,0 +1,90 @@ +; Declare constants for the multiboot header. +MBALIGN equ 1 << 0 ; align loaded modules on page boundaries +MEMINFO equ 1 << 1 ; provide memory map +FLAGS equ MBALIGN | MEMINFO ; this is the Multiboot 'flag' field +MAGIC equ 0x1BADB002 ; 'magic number' lets bootloader find the header +CHECKSUM equ -(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 +align 4 + dd MAGIC + dd FLAGS + dd CHECKSUM + +; The multiboot standard does not define the value of the stack pointer register +; (esp) and it is up to the kernel to provide a stack. This allocates room for a +; small stack by creating a symbol at the bottom of it, then allocating 16384 +; bytes for it, and finally creating a symbol at the top. The stack grows +; downwards on x86. The stack is in its own section so it can be marked nobits, +; which means the kernel file is smaller because it does not contain an +; uninitialized stack. The stack on x86 must be 16-byte aligned according to the +; System V ABI standard and de-facto extensions. The compiler will assume the +; stack is properly aligned and failure to align the stack will result in +; undefined behavior. +section .bss +align 16 +stack_bottom: +resb 16384 ; 16 KiB +stack_top: + +; 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. +; Declare _start as a function symbol with the given symbol size. +section .text +global _start:function (_start.end - _start) +_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 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. + + ; To set up a stack, we set the esp register to point to the top of our + ; stack (as it grows downwards on x86 systems). This is necessarily done + ; in assembly as languages such as C cannot function without a stack. + mov esp, stack_top + + ; 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 isnot 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 since pushed a multiple of 16 bytes to the + ; stack since (pushed 0 bytes so far) and the alignment is thus + ; preserved and the call is well defined. + ; note, that if you are building on Windows, C functions may have "_" prefix in assembly: _kernel_main + extern kernel_main + call kernel_main + + ; 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. + cli +.hang: hlt + jmp .hang +.end: diff --git a/src/boot.s b/src/boot.s new file mode 100644 index 0000000..172fd14 --- /dev/null +++ b/src/boot.s @@ -0,0 +1,109 @@ +/* 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 +.align 4 +.long MAGIC +.long FLAGS +.long CHECKSUM + +/* +The multiboot standard does not define the value of the stack pointer register +(esp) and it is up to the kernel to provide a stack. This allocates room for a +small stack by creating a symbol at the bottom of it, then allocating 16384 +bytes for it, and finally creating a symbol at the top. The stack grows +downwards on x86. The stack is in its own section so it can be marked nobits, +which means the kernel file is smaller because it does not contain an +uninitialized stack. The stack on x86 must be 16-byte aligned according to the +System V ABI standard and de-facto extensions. The compiler will assume the +stack is properly aligned and failure to align the stack will result in +undefined behavior. +*/ +.section .bss +.align 16 +stack_bottom: +.skip 16384 # 16 KiB +stack_top: + +/* +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 +.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 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. + */ + + /* + 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. + */ + mov $stack_top, %esp + + /* + 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 instuctions 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. + */ + call kernel_main + + /* + 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. + */ + 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 diff --git a/src/grub.cfg b/src/grub.cfg new file mode 100644 index 0000000..b2f8404 --- /dev/null +++ b/src/grub.cfg @@ -0,0 +1,3 @@ +menuentry "myos" { + multiboot /boot/myos.bin +} diff --git a/src/kernel.c b/src/kernel.c new file mode 100644 index 0000000..dd81d33 --- /dev/null +++ b/src/kernel.c @@ -0,0 +1,124 @@ +#include +#include +#include + +/* Check if the compiler thinks you are targeting the wrong operating system. */ +#if defined(__linux__) +#error "You are not using a cross-compiler, you will most certainly run into trouble" +#endif + +/* This tutorial will only work for the 32-bit ix86 targets. */ +#if !defined(__i386__) +#error "This tutorial needs to be compiled with a ix86-elf compiler" +#endif + +/* Hardware text mode color constants. */ +enum vga_color { + VGA_COLOR_BLACK = 0, + VGA_COLOR_BLUE = 1, + VGA_COLOR_GREEN = 2, + VGA_COLOR_CYAN = 3, + VGA_COLOR_RED = 4, + VGA_COLOR_MAGENTA = 5, + VGA_COLOR_BROWN = 6, + VGA_COLOR_LIGHT_GREY = 7, + VGA_COLOR_DARK_GREY = 8, + VGA_COLOR_LIGHT_BLUE = 9, + VGA_COLOR_LIGHT_GREEN = 10, + VGA_COLOR_LIGHT_CYAN = 11, + VGA_COLOR_LIGHT_RED = 12, + VGA_COLOR_LIGHT_MAGENTA = 13, + VGA_COLOR_LIGHT_BROWN = 14, + VGA_COLOR_WHITE = 15, +}; + +static inline uint8_t vga_entry_color(enum vga_color fg, enum vga_color bg) +{ + return fg | bg << 4; +} + +static inline uint16_t vga_entry(unsigned char uc, uint8_t color) +{ + return (uint16_t) uc | (uint16_t) color << 8; +} + +size_t strlen(const char* str) +{ + size_t len = 0; + while (str[len]) len++; + return len; +} + +static const size_t VGA_WIDTH = 80; +static const size_t VGA_HEIGHT = 25; + +size_t terminal_row; +size_t terminal_column; +uint8_t terminal_color; +uint16_t* terminal_buffer; + +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; + 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; + terminal_buffer[index] = vga_entry(' ', terminal_color); + } + } +} + +void terminal_setcoor(uint8_t color) +{ + terminal_color = color; +} + +void terminal_putentryat(char c, uint8_t color, size_t x, size_t y) +{ + const size_t index = y * VGA_WIDTH + x; + terminal_buffer[index] = vga_entry(c, color); +} + +void movescreen() +{ + if (terminal_row == VGA_HEIGHT) + { + terminal_row--; + for(size_t i=0;i