arch: i386: add support for x86 processors

Add support for 32-bit x86 processors, i.e. the 80386 and above.

Signed-off-by: Danny Holman <dholman@gymli.xyz>

5 files changed, 142 insertions, 0 deletions

diff --git a/arch/i386/boot.s b/arch/i386/boot.s
new file mode 100644
index 0000000..56ac227
--- /dev/null
+++ b/arch/i386/boot.s
@@ -0,0 +1,32 @@
+.set ALIGN,     1<<0
+.set MEMINFO,   1<<1
+.set FLAGS,     ALIGN | MEMINFO
+.set MAGIC,     0x1BADB002
+.set CHECKSUM,  -(MAGIC + FLAGS)
+
+.section .multiboot
+.align 4
+.long MAGIC
+.long FLAGS
+.long CHECKSUM
+
+.section .bss
+.align 16
+stack_bottom:
+.skip 16384
+stack_top:
+
+.section .text
+.global _start
+.type _start, @function
+
+_start:
+        movl $stack_top, %esp
+
+        call _init
+        call kernel_main
+
+        cli
+1:      hlt
+        jmp 1b
+.size _start, . - _start
diff --git a/arch/i386/crti.s b/arch/i386/crti.s
new file mode 100644
index 0000000..4e1e4cb
--- /dev/null
+++ b/arch/i386/crti.s
@@ -0,0 +1,15 @@
+.section .init
+.global _init
+.type _init, @function
+
+_init:
+        pushl %ebp
+        movl %esp, %ebp
+
+.section .fini
+.global _fini
+.type _fini, @function
+
+_fini:
+        pushl %ebp
+        movl %esp, %ebp
diff --git a/arch/i386/crtn.s b/arch/i386/crtn.s
new file mode 100644
index 0000000..447afb1
--- /dev/null
+++ b/arch/i386/crtn.s
@@ -0,0 +1,7 @@
+.section .init
+        popl %ebp
+        ret
+
+.section .fini
+        popl %ebp
+        ret
diff --git a/arch/i386/tty.c b/arch/i386/tty.c
new file mode 100644
index 0000000..9c3985b
--- /dev/null
+++ b/arch/i386/tty.c
@@ -0,0 +1,55 @@
+#include "vga.h"
+#include <kernel/tty.h>
+#include <kernel/string.h>
+#include <stddef.h>
+#include <stdint.h>
+
+static const size_t VGA_WIDTH = 80;
+static const size_t VGA_HEIGHT = 25;
+static uint16_t *const VGA_MEMORY = (uint16_t*)0xB8000;
+
+static size_t terminal_row;
+static size_t terminal_column;
+static uint8_t terminal_color;
+static uint16_t *terminal_buffer;
+
+void tty_init(void) {
+        terminal_row = 0;
+        terminal_column = 0;
+        terminal_color = vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK);
+        terminal_buffer = VGA_MEMORY;
+        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 tty_setcolor(uint8_t color) {
+        terminal_color = color;
+}
+
+void tty_putentryat(unsigned 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 tty_putchar(char c) {
+        unsigned char uc = c;
+        tty_putentryat(uc, terminal_color, terminal_column, terminal_row);
+        if (++terminal_column == VGA_WIDTH) {
+                terminal_column = 0;
+                if (++terminal_row == VGA_HEIGHT)
+                        terminal_row = 0;
+        }
+}
+
+void tty_write(const char *data, size_t size) {
+        for (size_t i = 0; i < size; i++)
+                tty_putchar(data[i]);
+}
+
+void tty_writestring(const char *data) {
+        tty_write(data, strlen(data));
+}
diff --git a/arch/i386/vga.h b/arch/i386/vga.h
new file mode 100644
index 0000000..e89f202
--- /dev/null
+++ b/arch/i386/vga.h
@@ -0,0 +1,33 @@
+#ifndef I386_VGA_H
+#define I386_VGA_H
+
+#include <stdint.h>
+
+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_LIGHT_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;
+}
+
+#endif