Initial commit

9 files changed, 339 insertions, 0 deletions

diff --git a/src/loader/cpu.c b/src/loader/cpu.c
new file mode 100644
index 0000000..a12d2fa
--- /dev/null
+++ b/src/loader/cpu.c
@@ -0,0 +1,26 @@
+// MIT License, Copyright (c) 2021 Marvin Borner
+
+#include <cpu.h>
+
+/**
+ * CPU IO
+ */
+
+u8 inb(u16 port)
+{
+	u8 value;
+	__asm__ volatile("inb %1, %0" : "=a"(value) : "Nd"(port));
+	return value;
+}
+
+u16 inw(u16 port)
+{
+	u16 value;
+	__asm__ volatile("inw %1, %0" : "=a"(value) : "Nd"(port));
+	return value;
+}
+
+void outb(u16 port, u8 data)
+{
+	__asm__ volatile("outb %0, %1" ::"a"(data), "Nd"(port));
+}
diff --git a/src/loader/inc/cpu.h b/src/loader/inc/cpu.h
new file mode 100644
index 0000000..88db34b
--- /dev/null
+++ b/src/loader/inc/cpu.h
@@ -0,0 +1,13 @@
+// MIT License, Copyright (c) 2021 Marvin Borner
+
+#ifndef CPU_H
+#define CPU_H
+
+#include <def.h>
+
+u8 inb(u16 port);
+u16 inw(u16 port);
+
+void outb(u16 port, u8 data);
+
+#endif
diff --git a/src/loader/inc/def.h b/src/loader/inc/def.h
new file mode 100644
index 0000000..8c2f9aa
--- /dev/null
+++ b/src/loader/inc/def.h
@@ -0,0 +1,28 @@
+// MIT License, Copyright (c) 2021 Marvin Borner
+// Useful macros/types
+
+#ifndef DEF_H
+#define DEF_H
+
+typedef signed char s8;
+typedef unsigned char u8;
+
+typedef signed short s16;
+typedef unsigned short u16;
+
+typedef signed int s32;
+typedef unsigned int u32;
+
+typedef __builtin_va_list va_list;
+#define va_start __builtin_va_start
+#define va_end __builtin_va_end
+#define va_arg __builtin_va_arg
+
+#define NULL ((void *)0)
+#define MIN(a, b) (((a) < (b)) ? (a) : (b))
+#define MAX(a, b) (((a) > (b)) ? (a) : (b))
+#define ABS(a) (((a) < 0) ? -(a) : (a))
+
+#define PACKED __attribute__((packed))
+
+#endif
diff --git a/src/loader/inc/lib.h b/src/loader/inc/lib.h
new file mode 100644
index 0000000..997db67
--- /dev/null
+++ b/src/loader/inc/lib.h
@@ -0,0 +1,14 @@
+// MIT License, Copyright (c) 2021 Marvin Borner
+
+#ifndef LIB_H
+#define LIB_H
+
+#include <def.h>
+
+u32 strlen(const char *str);
+u32 strnlen(const char *s, u32 max);
+u32 strlcpy(char *dst, const char *src, u32 size);
+
+int itoa(s32 value, char *buffer, u32 base);
+
+#endif
diff --git a/src/loader/inc/log.h b/src/loader/inc/log.h
new file mode 100644
index 0000000..2d65a76
--- /dev/null
+++ b/src/loader/inc/log.h
@@ -0,0 +1,11 @@
+// MIT License, Copyright (c) 2021 Marvin Borner
+
+#ifndef LOG_H
+#define LOG_H
+
+void serial_install(void);
+void serial_print(const char *data);
+
+void log(const char *format, ...);
+
+#endif
diff --git a/src/loader/lib.c b/src/loader/lib.c
new file mode 100644
index 0000000..c54ef14
--- /dev/null
+++ b/src/loader/lib.c
@@ -0,0 +1,85 @@
+// MIT License, Copyright (c) 2021 Marvin Borner
+
+#include <lib.h>
+
+/**
+ * Common string functions
+ */
+
+u32 strlen(const char *str)
+{
+	const char *s = str;
+	while (*s)
+		s++;
+	return s - str;
+}
+
+u32 strnlen(const char *str, u32 max)
+{
+	const char *s = str;
+	while (max && *s) {
+		s++;
+		max--;
+	}
+	return s - str;
+}
+
+u32 strlcpy(char *dst, const char *src, u32 size)
+{
+	const char *orig = src;
+	u32 left = size;
+
+	if (left)
+		while (--left)
+			if (!(*dst++ = *src++))
+				break;
+
+	if (!left) {
+		if (size)
+			*dst = 0;
+		while (*src++)
+			;
+	}
+
+	return src - orig - 1;
+}
+
+/**
+ * Conversion
+ */
+
+int itoa(s32 value, char *buffer, u32 base)
+{
+	char tmp[16];
+	char *tp = tmp;
+	int i;
+	unsigned v;
+
+	int sign = (base == 10 && value < 0);
+	if (sign)
+		v = -value;
+	else
+		v = (unsigned)value;
+
+	while (v || tp == tmp) {
+		i = v % base;
+		v /= base;
+		if (i < 10)
+			*tp++ = i + '0';
+		else
+			*tp++ = i + 'a' - 10;
+	}
+
+	int len = tp - tmp;
+
+	if (sign) {
+		*buffer++ = '-';
+		len++;
+	}
+
+	while (tp > tmp)
+		*buffer++ = *--tp;
+	*buffer = '\0';
+
+	return len;
+}
diff --git a/src/loader/link.ld b/src/loader/link.ld
new file mode 100644
index 0000000..aa97f49
--- /dev/null
+++ b/src/loader/link.ld
@@ -0,0 +1,35 @@
+/* MIT License, Copyright (c) 2021 Marvin Borner */
+
+OUTPUT_FORMAT("elf32-i386")
+OUTPUT_ARCH(i386)
+ENTRY(start)
+phys = 0x7e00;
+
+SECTIONS
+{
+	. = phys;
+
+	.text :
+	{
+		*(.text.start)
+		*(.text*)
+	}
+
+	.rodata :
+	{
+		*(.rodata*)
+	}
+
+	.data :
+	{
+		*(.data*)
+	}
+
+	.bss :
+	{
+		*(COMMON)
+		*(.bss)
+	}
+
+	end = .;
+}
diff --git a/src/loader/log.c b/src/loader/log.c
new file mode 100644
index 0000000..a2c05f0
--- /dev/null
+++ b/src/loader/log.c
@@ -0,0 +1,108 @@
+#include <cpu.h>
+#include <lib.h>
+#include <log.h>
+
+/**
+ * Formatting
+ */
+
+static u32 vsnprintf(char *str, u32 size, const char *format, va_list ap)
+{
+	u32 length = 0;
+
+	int temp_int;
+	char temp_ch;
+	char *temp_str;
+
+	char buffer[64] = { 0 };
+
+	// TODO: Fix potential memory overflows because of str[length++]=xxx
+	char ch;
+	while ((ch = *format++)) {
+		if (ch == '%') {
+			switch (*format++) {
+			case '%':
+				str[length++] = '%';
+				break;
+			case 'c':
+				temp_ch = va_arg(ap, int);
+				str[length++] = temp_ch;
+				break;
+			case 's':
+				temp_str = va_arg(ap, char *);
+				length += strlcpy(&str[length], temp_str, size - length);
+				break;
+			case 'b':
+				temp_int = va_arg(ap, int);
+				itoa(temp_int, buffer, 2);
+				length += strlcpy(&str[length], buffer, size - length);
+				break;
+			case 'd':
+				temp_int = va_arg(ap, int);
+				itoa(temp_int, buffer, 10);
+				length += strlcpy(&str[length], buffer, size - length);
+				break;
+			case 'x':
+				temp_int = va_arg(ap, int);
+				itoa(temp_int, buffer, 16);
+				length += strlcpy(&str[length], buffer, size - length);
+				break;
+			default:
+				serial_print("Unknown printf format\n");
+			}
+		} else {
+			str[length++] = ch;
+		}
+	}
+
+	return length;
+}
+
+/**
+ * Serial
+ */
+
+void serial_install(void)
+{
+	outb(0x3f8 + 1, 0x00);
+	outb(0x3f8 + 3, 0x80);
+	outb(0x3f8 + 0, 0x03);
+	outb(0x3f8 + 1, 0x00);
+	outb(0x3f8 + 3, 0x03);
+	outb(0x3f8 + 2, 0xc7);
+	outb(0x3f8 + 4, 0x0B);
+}
+
+static int is_transmit_empty(void)
+{
+	return inb(0x3f8 + 5) & 0x20;
+}
+
+static void serial_put(char ch)
+{
+	while (is_transmit_empty() == 0)
+		;
+	outb(0x3f8, (u8)ch);
+}
+
+void serial_print(const char *data)
+{
+	for (const char *p = data; *p; p++)
+		serial_put(*p);
+}
+
+/**
+ * Universal print function
+ */
+
+void log(const char *format, ...)
+{
+	char buf[1024] = { 0 };
+
+	va_list ap;
+	va_start(ap, format);
+	vsnprintf(buf, sizeof(buf), format, ap);
+	va_end(ap);
+
+	serial_print(buf);
+}
diff --git a/src/loader/main.c b/src/loader/main.c
new file mode 100644
index 0000000..54b5122
--- /dev/null
+++ b/src/loader/main.c
@@ -0,0 +1,19 @@
+// MIT License, Copyright (c) 2021 Marvin Borner
+
+#include <def.h>
+#include <log.h>
+
+/**
+ * Entry
+ */
+
+int start(void);
+int start(void)
+{
+	serial_install();
+	log("Hello %d\n", 42);
+
+	while (1)
+		;
+	return 0;
+}