Added a lot of comments in kernel code. A bit of cleaning too.

5 files changed, 52 insertions, 23 deletions

diff --git a/src/kernel/core/kmain.c b/src/kernel/core/kmain.c
index d8f059a..cfb9935 100644
--- a/src/kernel/core/kmain.c
+++ b/src/kernel/core/kmain.c
@@ -10,7 +10,16 @@
 #include <mem/mem.h>
 #include <linker/elf.h>
 
+/*	The kernel's main procedure. This function is called in loader_.asm.
+	This function calls the initializer functions for all system parts.
+	It then loads the modules the kernel was given by the bootloader. 
+	This function never returns : once multitasking is started for good,
+	the execution flow of this function is never returned to. */
 void kmain(struct multiboot_info_t* mbd, int32_t magic) {
+	monitor_clear();
+
+	ASSERT(magic == MULTIBOOT_BOOTLOADER_MAGIC);
+
 	size_t totalRam = 0;
 	uint32_t i;
 
@@ -25,8 +34,6 @@ void kmain(struct multiboot_info_t* mbd, int32_t magic) {
 			mem_placementAddr = (mods[i].mod_end & 0xFFFFF000) + 0x1000;
 	}
 
-	monitor_clear();
-
 	if (magic != MULTIBOOT_BOOTLOADER_MAGIC) {
 		PANIC("wrong multiboot magic number.");
 	}
@@ -62,4 +69,5 @@ void kmain(struct multiboot_info_t* mbd, int32_t magic) {
 	monitor_write("Modules now RULE THE WORLD !\n");
 	sti();
 	tasking_switch();
+	PANIC("Should never happen. Something probably went wrong with multitasking.");
 }
diff --git a/src/kernel/core/monitor.c b/src/kernel/core/monitor.c
index 6660fe0..0d0f5eb 100644
--- a/src/kernel/core/monitor.c
+++ b/src/kernel/core/monitor.c
@@ -4,6 +4,9 @@
 static int cursor_x = 0, cursor_y = 0;
 static uint16_t *video_memory = (uint16_t*)0xE00B8000;
 
+static uint8_t attribute = 0x07; // 0 = background = black, 7 = foreground = white
+
+/*	For internal use only. Tells hardware to move the cursor at (cursor_x, cursor_y). */
 static void move_cursor() {
 	uint16_t cursor_location = cursor_y * 80 + cursor_x;
 	outb(0x3D4, 14);	//Sending high cursor byte
@@ -12,9 +15,9 @@ static void move_cursor() {
 	outb(0x3D5, cursor_location);
 }
 
+/*	For internal use only. Scrolls everything up one line. */
 static void scroll() {
-	uint8_t attribute_byte = (0 /* black */ << 4) | (7/* white */ & 0x0F);
-	uint16_t blank = (attribute_byte << 8) | 0x20;
+	uint16_t blank = (attribute << 8) | 0x20;
 
 	if (cursor_y >= 25) {
 		int i;
@@ -28,16 +31,11 @@ static void scroll() {
 	}
 }
 
+/*	Put one character on the screen. This function handles special characters \b, \t, \r and  \n. */
 void monitor_put(char c) {
-	uint8_t fg = 7;	//White
-	uint8_t bg = 0; //Black
-
-	uint16_t attribute = (fg & 0x0F) | (bg << 4);
-	attribute = attribute << 8;
-
-	if (c == 0x08 && cursor_x) {	//Backspace
+	if (c == '\b' && cursor_x) {	//Backspace
 		cursor_x--;
-	} else if (c == 0x09) {	//Tab
+	} else if (c == '\t') {	//Tab
 		cursor_x = (cursor_x + 8) & ~(8 - 1);
 	} else if (c == '\r') {	//Carriage return
 		cursor_x = 0;
@@ -45,7 +43,7 @@ void monitor_put(char c) {
 		cursor_x = 0;
 		cursor_y++;
 	} else if (c >= ' ') {	//Any printable character
-		video_memory[cursor_y * 80 + cursor_x] = c | attribute;
+		video_memory[cursor_y * 80 + cursor_x] = c | (attribute << 8);
 		cursor_x++;
 	}
 	if (cursor_x >= 80) {
@@ -57,9 +55,9 @@ void monitor_put(char c) {
 	move_cursor();
 }
 
+/* Clears the screen and moves cursor to (0,0) (top left corner) */
 void monitor_clear() {
-	uint8_t attribute_byte = (0 /* black */ << 4) | (15 /* white */ & 0x0F);
-	uint16_t blank = (attribute_byte << 8) | 0x20;
+	uint16_t blank = (attribute << 8) | 0x20;
 
 	int i;
 
@@ -71,12 +69,14 @@ void monitor_clear() {
 	move_cursor();
 }
 
+/* Writes a string to the monitor */
 void monitor_write(char *s) {
 	while (*s) {
 		monitor_put(*(s++));
 	}
 }
 
+/* Writes a number in hexadecimal notation to the monitor */
 void monitor_writeHex(uint32_t v) {
 	int i;
 
@@ -89,6 +89,7 @@ void monitor_writeHex(uint32_t v) {
 	}
 }
 
+/* Writes a number in decimal notation to the monitor */
 void monitor_writeDec(uint32_t v) {
 	if (v == 0) {
 		monitor_put('0');
diff --git a/src/kernel/core/monitor.h b/src/kernel/core/monitor.h
index f4605cf..c04632e 100644
--- a/src/kernel/core/monitor.h
+++ b/src/kernel/core/monitor.h
@@ -10,6 +10,11 @@ void monitor_writeHex(uint32_t v);
 void monitor_writeDec(uint32_t v);
 
 #define NL monitor_put('\n');
+#define WHERE { monitor_write("(kernel:");	\
+				monitor_write(__FILE__);	\
+				monitor_write(":");			\
+				monitor_writeDec(__LINE__);	\
+				monitor_write(") "); }
 
 #endif
 
diff --git a/src/kernel/core/sys.c b/src/kernel/core/sys.c
index 1e07f7c..96d4908 100644
--- a/src/kernel/core/sys.c
+++ b/src/kernel/core/sys.c
@@ -1,6 +1,9 @@
 #include "sys.h"
 #include "monitor.h"
 
+/*	These four functions are wrappers around ASM operations.
+	These functions are used when comunicating with the system hardware. */
+
 void outb(uint16_t port, uint8_t value) {
 	asm volatile("outb %1, %0" : : "dN"(port), "a"(value));
 }
@@ -21,14 +24,24 @@ uint16_t inw(uint16_t port) {
 	return ret;
 }
 
+/*	These two functions stop the system, reporting an error message, because something bad happenned. */
+
 void panic(char* message, char* file, int line) {
-	monitor_write("\n>> PANIC: >>");
-	monitor_write(message); monitor_write("<< at "); monitor_write(file);
-	monitor_write(":"); monitor_writeDec(line);
-	monitor_write("\nSystem halted -_-'");
+	monitor_write("\n\nPANIC:\t\t"); monitor_write(message);
+	monitor_write("\n File:\t\t"); monitor_write(file); monitor_put(':'); monitor_writeDec(line);
+	monitor_write("\n\t\tSystem halted -_-'\n");
+	asm volatile("cli; hlt");
+}
+
+void panic_assert(char* assertion, char* file, int line) {
+	monitor_write("\n\nASSERT FAILED:\t"); monitor_write(assertion);
+	monitor_write("\n File:\t\t"); monitor_write(file); monitor_put(':'); monitor_writeDec(line);
+	monitor_write("\n\t\tSystem halted -_-'\n");
 	asm volatile("cli; hlt");
 }
 
+/* Global system mutex. See comments in sys.h. */
+
 static uint32_t if_locks = 1;
 
 void cli() {
diff --git a/src/kernel/core/sys.h b/src/kernel/core/sys.h
index 2f8cd5e..f147922 100644
--- a/src/kernel/core/sys.h
+++ b/src/kernel/core/sys.h
@@ -9,11 +9,13 @@ uint8_t inb(uint16_t port);
 uint16_t inw(uint16_t port);
 
 #define PANIC(s) panic(s, __FILE__, __LINE__);
+#define ASSERT(s) { if (!(s)) panic_assert(#s, __FILE__, __LINE__); }
 void panic(char* message, char* file, int line);
+void panic_assert(char* assertion, char* file, int line);
 
-void sti();		//GLOBAL SYSTEM MUTEX
-void cli();
-
-#define WHERE { monitor_write("(kernel:"); monitor_write(__FILE__); monitor_write(":"); monitor_writeDec(__LINE__); monitor_write(") "); }
+/*	For some actions, we use cli and sti as a global system mutex.
+	These actions include : system initialization, process creation, interrupt handling. */
+void cli();	//lock
+void sti();	//unlock
 
 #endif