Move to GitHub for flexing

include/gdt.h

@@ -14,4 +14,8 @@ struct GDT_ptr {
     uint32_t base;
 } __attribute((packed));
 
+uint8_t gdt_entries[8 * 3]; // (8 bytes per entry) * (num entries) 
+
+void encodeGDT(uint8_t* gdtEntry, struct GDT source);
+void initializeGDT();
 #endif //GDT_H

include/idt.h

@@ -0,0 +1,56 @@
+#ifndef IDT_H
+#define IDT_H
+
+#include "types.h"
+
+struct IDT {
+    uint32_t base;
+    uint16_t selector;
+    uint8_t  flags;
+} __attribute__((packed));
+
+struct IDT_ptr {
+    uint16_t limit;
+    uint32_t base;
+} __attribute__((packed));
+
+uint8_t idt_entries[8 * 256]; // 8 bytes per entry * 256 entries
+
+struct IDT createIDT(uint32_t base, uint16_t selector, uint8_t flags); 
+void encodeIDT(uint8_t* idtEntry, struct IDT source);
+void initializeIDT();
+
+extern void isr0 (); 
+extern void isr1 ();
+extern void isr2 ();
+extern void isr3 ();
+extern void isr4 ();
+extern void isr5 ();
+extern void isr6 ();
+extern void isr7 ();
+extern void isr8 ();
+extern void isr9 ();
+extern void isr10();
+extern void isr11(); 
+extern void isr12();
+extern void isr13();
+extern void isr14();
+extern void isr15();
+extern void isr16();
+extern void isr17();
+extern void isr18();
+extern void isr19();
+extern void isr20();
+extern void isr21();
+extern void isr22();
+extern void isr23();
+extern void isr24();
+extern void isr25();
+extern void isr26();
+extern void isr27();
+extern void isr28();
+extern void isr29();
+extern void isr30();
+extern void isr31();
+
+#endif // IDT_H

include/isr.h

@@ -0,0 +1,13 @@
+#ifndef ISR_H
+#define ISR_H
+
+#include "types.h"
+
+struct registers{
+    uint32_t ds;
+    uint32_t edi, esi, ebp, esp, ebx, edx, ecx, eax;
+    uint32_t int_no, err_code;
+    uint32_t eip, cs, eflags, useresp, ss;
+} __attribute__((packed));
+
+#endif // ISR_H

include/port.h

@@ -0,0 +1,11 @@
+#ifndef PORT_H
+#define PORT_H
+
+#include "types.h"
+
+uint8_t  port_byte_in (uint8_t port);
+void     port_byte_out(uint8_t port, uint8_t data);
+uint16_t port_word_in (uint16_t port); 
+void     port_word_out(uint16_t port, uint16_t data);
+
+#endif // PORT_H

include/print.h

@@ -11,9 +11,14 @@ typedef struct TextOutput {
     uint16_t* vid_mem;
 }__attribute__((packed)) TextOutput;
 
+TextOutput monitor;
+
 TextOutput createOutput(const int max_row, const int max_column, uint16_t* vid_mem);
 void scrollText(TextOutput* textOutput);
 void putChar(uint8_t character, uint8_t background, uint8_t foreground, TextOutput* textOutput);
 void print(char* string, uint8_t background, uint8_t foreground, TextOutput* textOutput);
+char* itoa(int value, char* buffer, int base);
+void printToMonitor(char* string);
+void printIntToMonitor(int num, int base);
 
 #endif // PRINT_H

makefile

@@ -3,7 +3,7 @@ CXX     = i386-elf-gcc
 CFLAGS  = -std=gnu99 -ffreestanding -O2 -Wall -Wextra -nostdlib -Iinclude
 ASM     = nasm
 
-OBJECTS = gdt.o boot.o print.o kernel.o
+OBJECTS = boot.o gdt.o isr.o idt.o port.o print.o kernel.o
 
 %.o : src/%.c
 	$(CXX) $(CFLAGS) -o $@ -c $<

src/boot.s

@@ -38,19 +38,100 @@ stack_top:
 ; Declare _start as a function symbol with the given symbol size.
 section .text
 
-global _gdt_flush     ; Allows the C code to link to this
+global reloadSegments ; Flush GDT
-extern _gp            ; Says that '_gp' is in another file
+reloadSegments:
-_gdt_flush:
+   ; Reload CS register containing code selector:
-    lgdt [_gp]        ; Load the GDT with our '_gp' which is a special pointer
+   JMP   0x08:reload_CS ; 0x08 points at the new code selector
-    mov ax, 0x10      ; 0x10 is the offset in the GDT to our data segment
+reload_CS:
+   ; Reload data segment registers:
+   MOV   AX, 0x10 ; 0x10 points at the new data selector
+   MOV   DS, AX
+   MOV   ES, AX
+   MOV   FS, AX
+   MOV   GS, AX
+   MOV   SS, AX
+   RET
+
+%macro ISR_NOERRCODE 1  ; define a macro, taking one parameter
+  [GLOBAL isr%1]        ; %1 accesses the first parameter.
+  isr%1:
+    cli
+    push byte 0
+    push byte %1
+    jmp isr_common_stub
+%endmacro
+
+%macro ISR_ERRCODE 1
+  [GLOBAL isr%1]
+  isr%1:
+    cli
+    push byte %1
+    jmp isr_common_stub
+%endmacro 
+
+ISR_NOERRCODE 0
+ISR_NOERRCODE 1
+ISR_NOERRCODE 2
+ISR_NOERRCODE 3
+ISR_NOERRCODE 4
+ISR_NOERRCODE 5
+ISR_NOERRCODE 6
+ISR_NOERRCODE 7
+ISR_NOERRCODE 8
+ISR_NOERRCODE 9
+ISR_NOERRCODE 10
+ISR_NOERRCODE 11
+ISR_NOERRCODE 12
+ISR_NOERRCODE 13
+ISR_NOERRCODE 14
+ISR_NOERRCODE 15
+ISR_NOERRCODE 16
+ISR_NOERRCODE 17
+ISR_NOERRCODE 18
+ISR_NOERRCODE 19
+ISR_NOERRCODE 20
+ISR_NOERRCODE 21
+ISR_NOERRCODE 22
+ISR_NOERRCODE 23
+ISR_NOERRCODE 24
+ISR_NOERRCODE 25
+ISR_NOERRCODE 26
+ISR_NOERRCODE 27
+ISR_NOERRCODE 28
+ISR_NOERRCODE 29
+ISR_NOERRCODE 30
+ISR_NOERRCODE 31
+
+
+[EXTERN isr_handler]
+
+; This is our common ISR stub. It saves the processor state, sets
+; up for kernel mode segments, calls the C-level fault handler,
+; and finally restores the stack frame.
+isr_common_stub:
+   pusha                    ; Pushes edi,esi,ebp,esp,ebx,edx,ecx,eax
+
+   mov ax, ds               ; Lower 16-bits of eax = ds.
+   push eax                 ; save the data segment descriptor
+
+   mov ax, 0x10  ; load the kernel data segment descriptor
    mov ds, ax
    mov es, ax
    mov fs, ax
    mov gs, ax
-    mov ss, ax
+
-    jmp 0x08:flush2   ; 0x08 is the offset to our code segment: Far jump!
+   call isr_handler
-flush2:
+
-    ret               ; Returns back to the C code!
+   pop eax        ; reload the original data segment descriptor
+   mov ds, ax
+   mov es, ax
+   mov fs, ax
+   mov gs, ax
+
+   popa                     ; Pops edi,esi,ebp...
+   add esp, 8     ; Cleans up the pushed error code and pushed ISR number
+   sti
+   iret           ; pops 5 things at once: CS, EIP, EFLAGS, SS, and ESP
 
 global _start:function (_start.end - _start)
 _start:
@@ -70,6 +151,7 @@ _start:
 	; 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

src/gdt.c

@@ -1,5 +1,7 @@
 #include "gdt.h"
 
+extern void reloadSegments();
+
 void encodeGDT(uint8_t* gdtEntry, struct GDT source) {
     if ((source.limit > 65536) && ((source.limit & 0xFFF) == 0xFFF)) {
         // Set the GDT to use paging
@@ -34,3 +36,32 @@ void encodeGDT(uint8_t* gdtEntry, struct GDT source) {
     // where most of the ideas for this function are taken from shamelessly
     gdtEntry[5] = source.type;
 }
+
+void initializeGDT() {
+    struct GDT nullEntry;
+    nullEntry.limit = 0;
+    nullEntry.base  = 0;
+    nullEntry.type  = 0;
+
+    struct GDT codeSection;
+    codeSection.limit = 0xFFFFFFFF;
+    codeSection.base  = 0;
+    codeSection.type  = 0x9A;
+
+    struct GDT dataSection;
+    dataSection.limit = 0xFFFFFFFF;
+    dataSection.base  = 0;
+    dataSection.type  = 0x92;
+
+    encodeGDT(gdt_entries     , nullEntry  );
+    encodeGDT(gdt_entries + 8 , codeSection);
+    encodeGDT(gdt_entries + 16, dataSection);
+
+    struct GDT_ptr gdt_ptr;
+    gdt_ptr.limit = 8*3;
+    gdt_ptr.base  = (uint32_t)(&gdt_entries);
+
+    asm("lgdt (%0)" : :"r" ((uint8_t*)(&gdt_ptr)));
+
+    reloadSegments();
+}

src/idt.c

@@ -0,0 +1,67 @@
+#include "idt.h"
+
+struct IDT createIDT(uint32_t base, uint16_t selector, uint8_t flags) {
+    struct IDT result;
+    result.base     = base;
+    result.selector = selector;
+    result.flags    = flags;
+    return result;
+}
+
+void encodeIDT(uint8_t* idtEntry, struct IDT source) {
+    // Low base bytes
+    idtEntry[0] = source.base & 0xFF;
+    idtEntry[1] = (source.base >> 8) & 0xFF;
+    // Selector bytes
+    idtEntry[2] = source.selector & 0xFF;
+    idtEntry[3] = (source.selector >> 8) & 0xFF;
+    idtEntry[4] = 0; // Null byte
+    idtEntry[5] = source.flags; // Flag bytes
+    // High base bytes
+    idtEntry[6] = (source.base >> 16) & 0xFF;
+    idtEntry[7] = (source.base >> 24) & 0xFF;
+}
+
+void initializeIDT() {
+    struct IDT_ptr idt_ptr;
+    idt_ptr.limit = 8*256 - 1;
+    idt_ptr.base  = (uint32_t)&idt_entries;
+    
+    for (int i = 0; i < 256*8; i++)
+        idt_entries[i] = 0; // Just to be safe, set IDT to all 0
+
+    encodeIDT(&idt_entries[0]       , createIDT((uint32_t)isr0 , 0x08, 0x8E));
+    encodeIDT(&idt_entries[1*8 - 1] , createIDT((uint32_t)isr1 , 0x08, 0x8E));
+    encodeIDT(&idt_entries[2*8 - 1] , createIDT((uint32_t)isr2 , 0x08, 0x8E));
+    encodeIDT(&idt_entries[3*8 - 1] , createIDT((uint32_t)isr3 , 0x08, 0x8E));
+    encodeIDT(&idt_entries[4*8 - 1] , createIDT((uint32_t)isr4 , 0x08, 0x8E));
+    encodeIDT(&idt_entries[5*8 - 1] , createIDT((uint32_t)isr5 , 0x08, 0x8E));
+    encodeIDT(&idt_entries[6*8 - 1] , createIDT((uint32_t)isr6 , 0x08, 0x8E));
+    encodeIDT(&idt_entries[7*8 - 1] , createIDT((uint32_t)isr7 , 0x08, 0x8E));
+    encodeIDT(&idt_entries[8*8 - 1] , createIDT((uint32_t)isr8 , 0x08, 0x8E));
+    encodeIDT(&idt_entries[9*8 - 1] , createIDT((uint32_t)isr9 , 0x08, 0x8E));
+    encodeIDT(&idt_entries[10*8 - 1], createIDT((uint32_t)isr10, 0x08, 0x8E));
+    encodeIDT(&idt_entries[11*8 - 1], createIDT((uint32_t)isr11, 0x08, 0x8E));
+    encodeIDT(&idt_entries[12*8 - 1], createIDT((uint32_t)isr12, 0x08, 0x8E));
+    encodeIDT(&idt_entries[13*8 - 1], createIDT((uint32_t)isr13, 0x08, 0x8E));
+    encodeIDT(&idt_entries[14*8 - 1], createIDT((uint32_t)isr14, 0x08, 0x8E));
+    encodeIDT(&idt_entries[15*8 - 1], createIDT((uint32_t)isr15, 0x08, 0x8E));
+    encodeIDT(&idt_entries[16*8 - 1], createIDT((uint32_t)isr16, 0x08, 0x8E));
+    encodeIDT(&idt_entries[17*8 - 1], createIDT((uint32_t)isr17, 0x08, 0x8E));
+    encodeIDT(&idt_entries[18*8 - 1], createIDT((uint32_t)isr18, 0x08, 0x8E));
+    encodeIDT(&idt_entries[19*8 - 1], createIDT((uint32_t)isr19, 0x08, 0x8E));
+    encodeIDT(&idt_entries[20*8 - 1], createIDT((uint32_t)isr20, 0x08, 0x8E));
+    encodeIDT(&idt_entries[21*8 - 1], createIDT((uint32_t)isr21, 0x08, 0x8E));
+    encodeIDT(&idt_entries[22*8 - 1], createIDT((uint32_t)isr22, 0x08, 0x8E));
+    encodeIDT(&idt_entries[23*8 - 1], createIDT((uint32_t)isr23, 0x08, 0x8E));
+    encodeIDT(&idt_entries[24*8 - 1], createIDT((uint32_t)isr24, 0x08, 0x8E));
+    encodeIDT(&idt_entries[25*8 - 1], createIDT((uint32_t)isr25, 0x08, 0x8E));
+    encodeIDT(&idt_entries[26*8 - 1], createIDT((uint32_t)isr26, 0x08, 0x8E));
+    encodeIDT(&idt_entries[27*8 - 1], createIDT((uint32_t)isr27, 0x08, 0x8E));
+    encodeIDT(&idt_entries[28*8 - 1], createIDT((uint32_t)isr28, 0x08, 0x8E));
+    encodeIDT(&idt_entries[29*8 - 1], createIDT((uint32_t)isr29, 0x08, 0x8E));
+    encodeIDT(&idt_entries[30*8 - 1], createIDT((uint32_t)isr30, 0x08, 0x8E));
+    encodeIDT(&idt_entries[31*8 - 1], createIDT((uint32_t)isr31, 0x08, 0x8E));
+
+    asm("lidt (%0)" : :"r" ((uint8_t*)(&idt_ptr)));
+}

src/isr.c

@@ -0,0 +1,8 @@
+#include "isr.h"
+#include "print.h"
+
+void isr_handler(struct registers regs) {
+    printToMonitor("recieved interrupt: \n");
+    printIntToMonitor(regs.int_no, 10);
+    printToMonitor("\n");
+}

src/kernel.c

@@ -1,22 +1,21 @@
 #include "gdt.h"
+#include "idt.h"
+#include "isr.h"
 #include "types.h"
 #include "print.h"
+#include "port.h"
+
+// inline function to swap two numbers
 
 #define FOREGROUND 0x0 
 #define BACKGROUND 0xF
 
-void PrintWithScreenFill(char* string, TextOutput* output_stream) {
-    // Print a string and fill the screen
-    print(string, BACKGROUND, FOREGROUND, output_stream);
-    int row = output_stream->terminal_row;
-    while (output_stream->terminal_row < output_stream->max_row) {
-        putChar('\n', BACKGROUND, FOREGROUND, output_stream);
-    }
-    output_stream->terminal_row = row;
-}
-
 void kernel_main(void) {
-    TextOutput output_stream = createOutput(25,80,(uint16_t*)0xB8000);
+    initializeGDT();
-    PrintWithScreenFill("Hello, Logan World!\n", &output_stream);
+    initializeIDT();
+    printToMonitor("Hello\n");
+    printIntToMonitor(10, 10);
+    asm ("int $0x3");
+    asm ("int $0x4");
 }
 

src/port.c

@@ -0,0 +1,21 @@
+#include "port.h"
+
+uint8_t port_byte_in (uint8_t port) {
+    uint8_t result;
+    __asm__("in %%dx, %%al" : "=a" (result) : "d" (port));
+    return result;
+}
+
+void port_byte_out(uint8_t port, uint8_t data) {
+    __asm__("out %%al, %%dx" : :"a" (data), "d" (port));
+}
+
+uint16_t port_word_in (uint16_t port) {
+    uint16_t result;
+    __asm__("in %%dx, %%ax" : "=a" (result) : "d" (port));
+    return result;
+}
+
+void port_word_out (uint16_t port, uint16_t data) {
+    __asm__("out %%ax, %%dx" : :"a" (data), "d" (port));
+}

src/print.c

@@ -1,5 +1,8 @@
 #include "print.h"
 
+#define FOREGROUND 0x0 
+#define BACKGROUND 0xF
+
 TextOutput createOutput(const int max_row, const int max_column, uint16_t* vid_mem) {
     // Create a new TextOutput interface
     TextOutput output;
@@ -66,8 +69,77 @@ void putChar(uint8_t character, uint8_t background, uint8_t foreground,
 
 void print(char* string, uint8_t background, uint8_t foreground, TextOutput* textOutput) {
     // Print a string
-    for (string; *string; string++) {
+    while (*string) {
         putChar(*string, background, foreground, textOutput);
+        string++;
     }
 }
 
+void PrintWithScreenFill(char* string, TextOutput* output_stream) {
+    // Print a string and fill the screen
+    print(string, BACKGROUND, FOREGROUND, output_stream);
+    int row = output_stream->terminal_row;
+    while (output_stream->terminal_row < output_stream->max_row) {
+        putChar('\n', BACKGROUND, FOREGROUND, output_stream);
+    }
+    output_stream->terminal_row = row;
+}
+
+
+inline void swap(char *x, char *y) {
+    char t = *x; *x = *y; *y = t;
+}
+
+int abs(int value) {
+    return (value < 0 ? -value : value);
+}
+ 
+// function to reverse buffer[i..j]
+char* reverse(char *buffer, int i, int j)
+{
+    while (i < j)
+        swap(&buffer[i++], &buffer[j--]);
+ 
+    return buffer;
+}
+ 
+// Iterative function to implement itoa() function in C
+char* itoa(int value, char* buffer, int base)
+{
+    if (base < 2 || base > 32)
+        return buffer;
+    int n = abs(value);
+    int i = 0;
+    while (n)
+    {
+        int r = n % base;
+        if (r >= 10) 
+            buffer[i++] = 65 + (r - 10);
+        else
+            buffer[i++] = 48 + r;
+        n = n / base;
+    }
+    if (i == 0)
+        buffer[i++] = '0';
+    if (value < 0 && base == 10)
+        buffer[i++] = '-';
+    buffer[i] = '\0';
+    return reverse(buffer, 0, i - 1);
+}
+
+int haveFilledScreen = 0;
+
+void printToMonitor(char* string) {
+    if (!haveFilledScreen) {
+        monitor = createOutput(25, 80, (uint16_t*)(0xB8000));
+        PrintWithScreenFill(string, &monitor);
+        haveFilledScreen = 1;
+    }
+    else
+        print(string, BACKGROUND, FOREGROUND, &monitor);
+}
+
+void printIntToMonitor(int num, int base) {
+    char* buffer;
+    printToMonitor(itoa(num, buffer, base));
+}