did some restructuring, got multitasking almost working

compile_commands.json

@@ -9,11 +9,11 @@
       "-Wextra",
       "-Ikernel",
       "-o",
-      "obj/kernel/boot/boot.o",
+      "obj/kernel/drivers/pit/pit.S.o",
-      "kernel/boot/boot.S"
+      "kernel/drivers/pit/pit.S"
     ],
     "directory": "/home/slinky/source/RockOS",
-    "file": "/home/slinky/source/RockOS/kernel/boot/boot.S",
+    "file": "/home/slinky/source/RockOS/kernel/drivers/pit/pit.S",
-    "output": "/home/slinky/source/RockOS/obj/kernel/boot/boot.o"
+    "output": "/home/slinky/source/RockOS/obj/kernel/drivers/pit/pit.S.o"
   }
 ]

kernel/common.S

@@ -116,3 +116,8 @@ outsw:
     pop %esi
     leave
     ret
+
+.global fetch_cr3
+fetch_cr3: 
+    mov %cr3, %eax 
+    ret

kernel/drivers/pic/pic.S

@@ -1,7 +1,12 @@
-#include "drivers/pic/pic.h"
+#define PIC1_ADDR	0x20 + 0xC0000000
+#define PIC2_ADDR	0xA0 + 0xC0000000		
+#define PIC1_COMMAND	PIC1_ADDR
+#define PIC1_DATA	(PIC1_ADDR+1)
+#define PIC2_COMMAND	PIC2_ADDR
+#define PIC2_DATA	(PIC2_ADDR+1)
+#define PIC_EOI		0x20
 
 .code32
-.extern io_wait
 
 .global init_pic
 init_pic:

kernel/drivers/pic/pic.h

@@ -1,7 +1,9 @@
-#define PIC1_ADDR	0x20 + 0xC0000000
+#ifndef DPIC_H
-#define PIC2_ADDR	0xA0 + 0xC0000000		
+#define DPIC_H
-#define PIC1_COMMAND	PIC1_ADDR
+
-#define PIC1_DATA	(PIC1_ADDR+1)
+void init_pic();
-#define PIC2_COMMAND	PIC2_ADDR
+
-#define PIC2_DATA	(PIC2_ADDR+1)
+void send_eoi_master();
-#define PIC_EOI		0x20	
+void send_eoi_slave();
+
+#endif

kernel/drivers/pit/pit.S

@@ -1,7 +1,4 @@
-#include "drivers/pit/pit.h"
-
 .code32 
-
 .global init_pit
 init_pit: # tickrate: 1193182/1000 = 0x04A9 (1000hz) (1ms)
     movb $0x36, %al

kernel/drivers/pit/pit.h

@@ -0,0 +1,6 @@
+#ifndef DPIT_H
+#define DPIT_H
+
+void init_pit();
+
+#endif

kernel/drivers/ps2/ps2.S

@@ -9,8 +9,6 @@
 .global ps2_write_data
 .global ps2_flush_output_buffer
 
-.extern io_wait
-
 # helpers
 ps2_wait_input_empty: #(void) -> void
     push %ebp

kernel/drivers/ps2/ps2.c

@@ -1,4 +1,5 @@
 #include <stdint.h>
+
 #include <drivers/ps2/ps2.h>
 
 extern void ps2_wait_input_empty(void);

kernel/drivers/ps2/ps2.h

@@ -16,4 +16,10 @@
 #define SELF_TEST_SUCCESS 0x55 
 #define PORT_TEST_SUCCESS 0x00
 
+#ifndef __ASSEMBLER__ 
+#include <stdint.h>
+int init_ps2();
+uint8_t ps2_read_data();
+#endif
+
 #endif

kernel/drivers/vga/vga.c

@@ -26,10 +26,10 @@ enum vga_color {
 	VGA_COLOR_WHITE = 15,
 };
 
-size_t terminal_row;
+static size_t terminal_row;
-size_t terminal_column;
+static size_t terminal_column;
-uint8_t terminal_color;
+static uint8_t terminal_color;
-uint16_t* terminal_buffer = (uint16_t*)VGA_MEMORY;
+static uint16_t* terminal_buffer = (uint16_t*)VGA_MEMORY;
 
 static inline uint8_t vga_entry_color(enum vga_color fg, enum vga_color bg) 
 {
@@ -41,8 +41,7 @@ static inline uint16_t vga_entry(unsigned char uc, uint8_t color)
 	return (uint16_t) uc | (uint16_t) color << 8;
 }
 
-void vga_initialize() 
+void vga_init() {
-{
 	terminal_row = 0;
 	terminal_column = 0;
 	terminal_color = vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK);
@@ -55,8 +54,7 @@ void vga_initialize()
 	}
 }
 
-void vga_putchar(char c) 
+void vga_putchar(char c) {
-{
 	if (c == '\n') {
 		terminal_row++;
 		terminal_column = 0;
@@ -78,8 +76,3 @@ void vga_putchar(char c)
 			terminal_row = 0;
 	}
 }
-
-print_stream_t vga_print_stream = {
-    .putchar = vga_putchar,
-    .trunc = vga_initialize,
-};

kernel/drivers/vga/vga.h

@@ -0,0 +1,7 @@
+#ifndef DVGA_H
+#define DVGA_H
+
+void vga_init();
+void vga_putchar(char c);
+
+#endif

kernel/gdt.S

@@ -1,4 +1,5 @@
 .code32
+
 .extern gdtr 
 .global load_gdt
 load_gdt:

kernel/gdt.c

@@ -84,7 +84,7 @@ tss_entry tss;
 extern void load_gdt();
 extern void tss_flush();
 
-uint64_t create_descriptor(uint32_t base, uint32_t limit, uint16_t flag)
+static uint64_t create_descriptor(uint32_t base, uint32_t limit, uint16_t flag)
 {
     uint64_t descriptor;
  
@@ -101,7 +101,7 @@ uint64_t create_descriptor(uint32_t base, uint32_t limit, uint16_t flag)
     return descriptor;
 }
 
-uint64_t create_tss_descriptor(uint32_t base, uint32_t limit)
+static uint64_t create_tss_descriptor(uint32_t base, uint32_t limit)
 {
     uint64_t descriptor;
     uint16_t tss_flags = SEG_PRES(1) | SEG_PRIV(0) | SEG_DESCTYPE(0) | 0x09;

kernel/gdt.h

@@ -0,0 +1,6 @@
+#ifndef KGDT_H
+#define KGDT_H
+
+void init_gdt();
+
+#endif

kernel/globals.c

@@ -1,8 +1,7 @@
-#include <lib/stream.h>
 #include <stddef.h>
+
 #include "multiboot.h"
 
-print_stream_t* kout;
 multiboot_info* grub_boot_struct_ptr = NULL;
 
 extern char __kernel_start;

kernel/idt.c

@@ -1,61 +0,0 @@
-#include <stdint.h>
-#include <idt.h>
-
-#define IDT_MAX_DESCRIPTORS 256
-
-#define ATTR_KERN_32 0x8E // active(1), ring 0 (00), interrupt gate(0), 32 bit (1110)
-#define ATTR_USER_32 0xEE // active, ring 3, 32bit
-
-#define SEGMENT_KERN 0x08
-
-extern void load_idt(void);
-extern void enable_int(void);
-
-extern void isr0();
-extern void isr1();
-extern void isr8();
-extern void isr13();
-extern void isr14();
-extern void isr32();
-extern void isr33();
-
-void* isr_stub_table[256] = {
-    [0] = isr0,
-    [1] = isr1,
-    [8] = isr8,
-    [13] = isr13,
-    [14] = isr14,
-    [32] = isr32,
-    [33] = isr33,
-};
-
-idt_entry idt[IDT_MAX_DESCRIPTORS];
-idt_ptr idtr;
-
-void set_idtr(uint8_t vector, void* isr, uint16_t sel, uint8_t attributes) {
-    idt_entry* desc = &idt[vector];
-
-    desc->isr_low    = (uint32_t)isr & 0xFFFF;
-    desc->selector  = SEGMENT_KERN;
-    desc->reserved   = 0;
-    desc->attributes = attributes;
-    desc->isr_high   = ((uint32_t)isr >> 16) & 0xFFFF;
-}
-
-void init_idt() {
-    idtr.limit = (sizeof(idt_entry) * IDT_MAX_DESCRIPTORS) - 1;
-    idtr.base  = (uint32_t)&idt;
-
-    for (int i = 0; i < IDT_MAX_DESCRIPTORS; i++) {
-        if (isr_stub_table[i] != 0) {
-            set_idtr(i, isr_stub_table[i], SEGMENT_KERN, ATTR_KERN_32);
-        } else {
-            set_idtr(i, 0, SEGMENT_KERN, 0);
-        }
-    }
-
-    extern void syscall_handler();
-    set_idtr(0x80, syscall_handler, SEGMENT_KERN, ATTR_USER_32);
-
-    load_idt();
-}

kernel/idt.h

@@ -1,19 +0,0 @@
-#ifndef KIDT_H
-#define KIDT_H
-
-#include <stdint.h>
-
-typedef struct __attribute__((packed)){
-    uint16_t isr_low; 
-    uint16_t selector; 
-    uint8_t  reserved;  
-    uint8_t  attributes;
-    uint16_t isr_high; 
-} idt_entry;
-
-typedef struct __attribute__((packed)){
-    uint16_t limit;
-    uint32_t base;
-} idt_ptr;
-
-#endif

kernel/interrupts.S

@@ -1,5 +1,4 @@
 .code32
-
 .macro ISR_NOERRCODE num
 .global isr\num
 isr\num:
@@ -33,18 +32,29 @@ load_idt:
     lidt idtr 
     ret
 
-.global enable_int
-enable_int:
-    sti
-    ret
-
 ISR_NOERRCODE 0    # Divide by Zero
 ISR_NOERRCODE 1    # Debug
 ISR_ERRCODE   8    # Double Fault (Has Error Code!)
 ISR_ERRCODE   13   # General Protection Fault (Has Error Code!)
 ISR_ERRCODE   14   # Page Fault (Has Error Code!)
 
-ISR_NOERRCODE 32   # IRQ0 - Timer
+// This is a special case so we need to handle it for task switching
+.global isr32
+isr32:
+    cli
+    pushal 
+
+    pushl %esp 
+    call schedule_next_task
+    movl %eax, %esp 
+
+    call send_eoi_master
+
+    popal
+    
+    sti
+    iret 
+
 ISR_NOERRCODE 33   # IRQ1 - Keyboard
 
 ISR_NOERRCODE 46   # IRQ14

kernel/interrupts.c

@@ -1,23 +1,61 @@
-#include "lib/print.h"
 #include <stdint.h>
 
-extern void send_eoi_master(void);
+#include <lib/print.h>
-extern void send_eoi_slave(void);
-extern uint8_t read_isr_master(void);
-extern uint8_t read_isr_slave(void);
 
-extern uint8_t ps2_read_data();
+#include "syscall.h"
 
-struct registers {
+#include <drivers/pic/pic.h>
+#include <drivers/ps2/ps2.h>
+
+#define IDT_MAX_DESCRIPTORS 256
+#define ATTR_KERN_32 0x8E // active(1), ring 0 (00), interrupt gate(0), 32 bit (1110)
+#define ATTR_USER_32 0xEE // active, ring 3, 32bit
+#define SEGMENT_KERN 0x08
+
+typedef struct __attribute__((packed)) {
+    uint16_t isr_low; 
+    uint16_t selector; 
+    uint8_t  reserved;  
+    uint8_t  attributes;
+    uint16_t isr_high; 
+} idt_entry;
+
+typedef struct __attribute__((packed)) {
+    uint16_t limit;
+    uint32_t base;
+} idt_ptr;
+
+typedef struct __attribute__((packed)) {
     uint32_t edi, esi, ebp, esp_dummy, ebx, edx, ecx, eax;
     
     uint32_t int_no;    
     uint32_t error_code;
     
     uint32_t eip, cs, eflags, useresp, ss;
+} registers;
+
+extern void load_idt(void);
+
+// isr stubs
+extern void isr0();
+extern void isr1();
+extern void isr8();
+extern void isr13();
+extern void isr14();
+extern void isr32();
+extern void isr33();
+
+static void* isr_stub_table[256] = {
+    [0] = isr0,
+    [1] = isr1,
+    [8] = isr8,
+    [13] = isr13,
+    [14] = isr14,
+    [32] = isr32,
+    [33] = isr33,
 };
 
-const char* err_messages[32] = {
+static const char* err_messages[32] = {
     [0] = "Divide by 0",
     [1] = "",
     [8] = "",
@@ -25,7 +63,37 @@ const char* err_messages[32] = {
     [14] = "Page Fault",
 };
 
-void common_interrupt_handler(struct registers *args) {
+idt_entry idt[IDT_MAX_DESCRIPTORS];
+idt_ptr idtr;
+
+static void set_idtr(uint8_t vector, void* isr, uint16_t sel, uint8_t attributes) {
+    idt_entry* desc = &idt[vector];
+
+    desc->isr_low    = (uint32_t)isr & 0xFFFF;
+    desc->selector  = SEGMENT_KERN;
+    desc->reserved   = 0;
+    desc->attributes = attributes;
+    desc->isr_high   = ((uint32_t)isr >> 16) & 0xFFFF;
+}
+
+void init_idt() {
+    idtr.limit = (sizeof(idt_entry) * IDT_MAX_DESCRIPTORS) - 1;
+    idtr.base  = (uint32_t)&idt;
+
+    for (int i = 0; i < IDT_MAX_DESCRIPTORS; i++) {
+        if (isr_stub_table[i] != 0) {
+            set_idtr(i, isr_stub_table[i], SEGMENT_KERN, ATTR_KERN_32);
+        } else {
+            set_idtr(i, 0, SEGMENT_KERN, 0);
+        }
+    }
+
+    set_idtr(0x80, syscall_handler, SEGMENT_KERN, ATTR_USER_32);
+
+    load_idt();
+}
+
+void common_interrupt_handler(registers *args) {
     switch (args->int_no) {
         case 0:
         case 1:

kernel/interrupts.h

@@ -0,0 +1,6 @@
+#ifndef KIDT_H
+#define KIDT_H
+
+void init_idt();
+
+#endif

kernel/kmain.c

@@ -1,150 +1,62 @@
 #include "multiboot.h"
-#include "idt.h"
+#include "interrupts.h"
 #include "elf.h"
+#include "gdt.h"
+#include "scheduler.h"
 
 #include <lib/print.h>
 #include <lib/stream.h>
 #include <lib/memory.h>
 
-#include "memory/mm.h"
+#include <memory/mm.h>
 
-#include "drivers/iso/iso.h"
+#include <drivers/iso/iso.h>
-#include "drivers/ide/ide.h"
+#include <drivers/ide/ide.h>
+#include <drivers/pic/pic.h>
+#include <drivers/ps2/ps2.h>
+#include <drivers/pit/pit.h>
+#include <drivers/vga/vga.h>
 
 #include <stddef.h>
 #include <stdint.h>
 
-extern void init_idt();
-extern void init_gdt();
-extern void init_pic();
-extern void init_pit();
-extern int init_ps2();
 extern void enable_interrupts();
-
+extern void disable_interrupts();
-void* page = NULL;
+extern uint32_t fetch_cr3();
 
 extern char __kernel_start;
 extern char __kernel_end;
 
-void* user_page_directories[10];
+void kernel_test_task() {
-
+  while (1) {
-void load_origin_program(multiboot_info* mbi) {
+    kprintf("task sleeping...\n");
-  user_page_directories[0] = create_user_pd();
+    sleep(10000000);
-  kprintf("Created origin process page directory @ [phys] 0x%x\n", user_page_directories[0]);
-  extern void load_pd(void* pd);
-  extern void flush_tlb();
-  load_pd(user_page_directories[0]);
-  flush_tlb();
-  kprintf("switched to user address space\n");
-
-  uint32_t mods_virtual_addr = mbi->mods_addr + 0xC0000000;
-  kprintf("parsing mutliboot modules @ 0x%x\n", mods_virtual_addr);
-
-  if (mbi->mods_count == 0) {
-    return;
   }
-
-  multiboot_module_entry* modules = (multiboot_module_entry*)mods_virtual_addr;
-
-  uint32_t elf_vbase = 0xE0000000;
-  uint32_t elf_pbase = modules[0].mod_start;
-  uint32_t elf_limit = modules[0].mod_end - modules[0].mod_start;
-  uint32_t elf_pages_needed = (elf_limit / 4096) + 1;
-
-  for (uint32_t i = 0; i < elf_pages_needed; i++) {
-    const uint32_t vaddr = elf_vbase + (i * 4096);
-    const uint32_t paddr = elf_pbase + (i * 4096);
-    map_page(vaddr, paddr, PAGE_PRESENT | PAGE_WRITABLE);
-  }
-
-  elf_header_t* elf = (elf_header_t*)elf_vbase;
-  elf_program_header_t* ph = (elf_program_header_t*)(elf_vbase + elf->e_phoff);
-
-  kprintf("elf header @ 0x%x\n", elf);
-  kprintf("program headers @ 0x%x\n", ph);
-
-  // load program sections into physical memory and map the pages
-  for (int i = 0; i < elf->e_phnum; i++) {
-    if (ph[i].p_type == PT_LOAD) {
-      uint32_t v_start = ph[i].p_vaddr & 0xFFFFF000;
-      uint32_t v_end = (ph[i].p_vaddr + ph[i].p_memsz + 4095) & 0xFFFFF000;
-
-      for (uint32_t page = v_start; page < v_end; page += 4096) {
-        uint32_t frame_paddr = (uint32_t)p_alloc_frame();
-        map_page(page, frame_paddr, PAGE_PRESENT | PAGE_WRITABLE | PAGE_USER);
-      }
-
-      for (uint32_t j = 0; j < ph[i].p_memsz; j++) {
-        ((char*)ph[i].p_vaddr)[j] = 0;
-      }
-
-      for (uint32_t j = 0; j < ph[i].p_filesz; j++) {
-        ((char*)ph[i].p_vaddr)[j] = ((char*)(elf_vbase + ph[i].p_offset))[j];
-      }
-    }
-  }
-
-  // allocate the user stack
-  uint32_t stack_paddr = (uint32_t)p_alloc_frame();
-  map_page(0xBFFFF000, stack_paddr, PAGE_PRESENT | PAGE_WRITABLE | PAGE_USER);
-
-  kprintf("program loaded into memory @ [virt] 0x%x\n", elf->e_entry);
-
-  extern void liftoff(uint32_t entry, uint32_t stack_top);
-  kprintf("launching origin process\n");
-  uint32_t stack_top =  0xBFFFF000 + 4095;
-  liftoff(elf->e_entry, stack_top);
 }
 
 void kmain(uint32_t magic, multiboot_info* mbi)  {
-  extern print_stream_t vga_print_stream;
-  extern print_stream_t* kout;
-  kout = &vga_print_stream;
-  kout->trunc();
-
-  kprintf("kernel start: 0x%x\n", &__kernel_start);
-  kprintf("kernel end: 0x%x\n", &__kernel_end);
-  uint32_t size = (&__kernel_end - &__kernel_start) / 1024;
-  kprintf("kernel size: %dKB\n", size);
-
   if (!(mbi->flags & (1 << 6))) {
     return;
   } 
 
-  kprintf("multiboot virtual address: 0x%x\n", mbi);
+  vga_init();
 
-  kprintf("parsing multiboot memory map\n");
   uint32_t mmap_virtual_addr = mbi->mmap_addr + 0xC0000000;
-  kprintf("mmap virtual address: 0x%x\n", mmap_virtual_addr);
   init_pmm((void*)mmap_virtual_addr, mbi->mmap_length);
+  kprintf("memory detection complete. total free memory: %dMB\n", total_free_memory() / 1024 / 1024);
 
-  kprintf("RockOS booting...\n");
   init_gdt();
-  extern uint64_t gdt[5];
-  kprintf("GDT set @ 0x%x\n", &gdt);
- 
   init_idt();
-  extern idt_entry idt[256];
-  kprintf("IDT set @ 0x%x\n", &idt);
-
   init_pic();
-  kprintf("PIC initialized\n");
-
   init_pit();
-  kprintf("PIT initialized\n"); 
   
   init_page_tables();
-  kprintf("Page tables initialized\n");
 
-  kgrow(1);
+  kprintf("basic initializations complete\n");
-  kprintf("Allocated 4kb for kernel heap\n");
 
-  kprintf("scanning for drives\n");
+  disable_interrupts();
-  extern void scan_drives();
+  init_scheduler();
-  scan_drives();
+  enable_interrupts();
 
-  ide_device_t* boot_cd_rom = get_ide_device(0);
+  while(1) yield();
-  read_iso(boot_cd_rom);
-
-  while(1);
 }

kernel/lib/memory.c

@@ -4,8 +4,9 @@
 #define KHEAP_START 0xE0000000
 
 typedef struct __attribute__((packed)) {
+    size_t size;
     uint8_t free;
-    uint32_t next_blk;
+    void* next_blk;
 } alloc_header_t;
 
 void memcpy(const void* src, void* dst, size_t sz) {
@@ -42,18 +43,6 @@ static void* kernel_heap_end = (void*)KHEAP_START;
 alloc_header_t* blk_list = NULL;
 
 void kgrow(size_t pages) {
-    if (kernel_heap_end == kernel_heap_start) {
-        // probaably not great, but if we don't have a heap yet, allocate the first (or only) frame requested.
-        // Then initialize the first block header for the allocator
-        void* frame = p_alloc_frame();
-        map_page((uint32_t)kernel_heap_end, (uint32_t)frame, PAGE_PRESENT | PAGE_WRITABLE);
-        kernel_heap_end = (void*)((uint32_t)kernel_heap_end + PAGE_SIZE);
-        pages--;
-        blk_list = kernel_heap_start;
-        blk_list->free = 1;
-        blk_list->next_blk = 0;
-    }
-
     for (size_t p = 0; p < pages; p++) {
         void* frame = p_alloc_frame();
         map_page((uint32_t)kernel_heap_end, (uint32_t)frame, PAGE_PRESENT | PAGE_WRITABLE);
@@ -61,34 +50,60 @@ void kgrow(size_t pages) {
     }
 }
 
+#define ALIGNMENT 4
+#define ALIGN(size) (((size) + (ALIGNMENT - 1)) & ~(ALIGNMENT - 1))
 void* kalloc(size_t sz) {
-    if (sz == 0) {
+    sz = ALIGN(sz);
-        return NULL;
+
+    if (kernel_heap_end == kernel_heap_start) {
+        // probaably not great, but if we don't have a heap yet, allocate the first (or only) frame requested.
+        // Then initialize the first block header for the allocator
+        kgrow(4);
+        
+        blk_list = (alloc_header_t*)kernel_heap_start;
+        blk_list->size = ((uint32_t)kernel_heap_end - (uint32_t)kernel_heap_start) - sizeof(alloc_header_t);
+        blk_list->free = 1;
+        blk_list->next_blk = NULL;
     }
 
-    alloc_header_t* header = blk_list;
+    alloc_header_t* curr = blk_list;
-    while (!header->free) {
+    alloc_header_t* prev = NULL;
-        if (header->next_blk == 0) {
+
-            return NULL;
+    while (curr != NULL) {
+        if (curr->free && curr->size >= sz) {
+            if (curr->size >= sz + sizeof(alloc_header_t) + ALIGNMENT) {
+                alloc_header_t* new_blk = (alloc_header_t*)((uint32_t)curr + sizeof(alloc_header_t) + sz);
+                
+                new_blk->size = curr->size - sz - sizeof(alloc_header_t);
+                new_blk->free = 1;
+                new_blk->next_blk = curr->next_blk;
+                
+                curr->size = sz;
+                curr->next_blk = new_blk;
+            }
+            
+            curr->free = 0; 
+            return (void*)((uint32_t)curr + sizeof(alloc_header_t));
         }
-        header = (alloc_header_t*)header->next_blk;
+        prev = curr;
+        curr = curr->next_blk;
     }
 
-    uint32_t data_ptr = (uint32_t)header + sizeof(alloc_header_t);
+    // no more space, grow!!
-    if (data_ptr >= (uint32_t)kernel_heap_end) {
+    size_t required_space = sz + sizeof(alloc_header_t);
-        return NULL;
+    size_t pages_to_grow = (required_space + PAGE_SIZE - 1) / PAGE_SIZE; 
-    } // if the start of the data is already at the end, we don't have room
     
-    uint32_t end_of_blk = data_ptr + sz;
+    alloc_header_t* new_heap_blk = (alloc_header_t*)kernel_heap_end;
-    if (end_of_blk > (uint32_t)kernel_heap_end) {
-        return NULL;
-    } // if the end of the data is past the end, we don't have room
     
-    if (end_of_blk != header->next_blk && end_of_blk < ((uint32_t)kernel_heap_end - sizeof(alloc_header_t))) {
+    kgrow(pages_to_grow);
-        header->next_blk = end_of_blk;
-        alloc_header_t* next_header = (alloc_header_t*)header->next_blk;
-        next_header->f
-    } // see if we have room to place the next header and at least 1 byte of data
     
-    return (void*)data_ptr;
+    new_heap_blk->size = (pages_to_grow * PAGE_SIZE) - sizeof(alloc_header_t);
+    new_heap_blk->free = 1;
+    new_heap_blk->next_blk = NULL;
+    
+    if (prev != NULL) {
+        prev->next_blk = new_heap_blk;
+    }
+    
+    return kalloc(sz);
 }

kernel/lib/memory.h

@@ -11,7 +11,7 @@ int strcmp(const char *s1, const char *s2);
 int strlen(const char* str);
 
 void kgrow(size_t pages);
-void* alloc(size_t sz);
+void* kalloc(size_t sz);
 
 
 #endif

kernel/lib/print.c

@@ -1,20 +1,25 @@
 #include "print.h"
 #include "stream.h"
+#include "tasks.h"
+
 #include <stdarg.h>
 
-extern print_stream_t* kout;
+#include <drivers/vga/vga.h>
+
+spinlock_t kwrite_lock = {0};
+
 static char* hex_chars = "0123456789abcdef";
 
 static void kprint(const char *str) {
     while (*str) {
-        kout->putchar(*str);
+        vga_putchar(*str);
         str++;
     }
 }
 
 static void kputd(int d) {
     if (d == 0) {
-        kout->putchar('0');
+        vga_putchar('0');
         return;
     }
     char buffer[12];
@@ -24,13 +29,13 @@ static void kputd(int d) {
         d /= 10;
     }
     for (int j = i - 1; j >= 0; j--) {
-        kout->putchar(buffer[j]);
+        vga_putchar(buffer[j]);
     }
 }
 
 static void kputx(unsigned int x) {
     if (x == 0) {
-        kout->putchar('0');
+        vga_putchar('0');
         return;
     }
     char buffer[8];
@@ -41,15 +46,18 @@ static void kputx(unsigned int x) {
         x >>= 4;
     }
     for (int j = i - 1; j >= 0; j--) {
-        kout->putchar(buffer[j]);
+        vga_putchar(buffer[j]);
     }
 }
 
 void kputc(const char c) {
-    kout->putchar(c);
+    spin_lock(&kwrite_lock);
+    vga_putchar(c);
+    spin_unlock(&kwrite_lock);
 }
 
 void kprintf(const char* fmt, ...) {
+    spin_lock(&kwrite_lock);
     va_list args;
     va_start(args, fmt);
     
@@ -73,19 +81,20 @@ void kprintf(const char* fmt, ...) {
                     break;
                 }
                 case '%':
-                    kout->putchar('%');
+                    vga_putchar('%');
                     break;
                 default:
-                    kout->putchar('%');
+                    vga_putchar('%');
-                    kout->putchar(*fmt);
+                    vga_putchar(*fmt);
                     break;
             }
             fmt++;
         } else {
-            kout->putchar(*fmt);
+            vga_putchar(*fmt);
             fmt++;
         }
     }
     
     va_end(args);
+    spin_unlock(&kwrite_lock);
 }

kernel/lib/tasks.c

@@ -0,0 +1,11 @@
+#include <lib/tasks.h>
+
+void spin_lock(spinlock_t *lock) {
+    while (__sync_lock_test_and_set(&lock->locked, 1)) {
+        asm volatile("pause"); 
+    }
+}
+
+void spin_unlock(spinlock_t *lock) {
+    __sync_lock_release(&lock->locked);
+}

kernel/lib/tasks.h

@@ -0,0 +1,13 @@
+#ifndef KTASKS_H
+#define KTASKS_H
+
+#include <stdint.h>
+
+typedef struct {
+    volatile uint32_t locked;
+} spinlock_t;
+
+void spin_lock(spinlock_t *lock);
+void spin_unlock(spinlock_t *lock);
+
+#endif 

kernel/memory/mm.c

@@ -18,7 +18,7 @@ extern void disable_pae();
 #define PAGE_TABLES  0xFFC00000
 #define PAGE_DIRECTORY  0xFFFFF000
 
-#define TEMP_MAPPING_VADDR 0xE0000000
+#define TEMP_MAPPING_VADDR 0xDFFF0000
 
 static uint32_t max_address = 0;
 static uint32_t total_available_memory = 0;
@@ -141,8 +141,6 @@ void init_pmm(void* mmap_base, uint32_t mmap_limit) {
     if (mmap_base != NULL && mmap_limit > 0) {
         parse_multiboot_mmap(mmap_base, mmap_limit);
     }
-
-    kprintf("total free memory: %dMB\n", total_available_memory / 1024 / 1024);
 }
 
 void init_page_tables() {
@@ -165,7 +163,7 @@ uint32_t total_free_memory() {
     return total_available_memory;
 }
 
-void* create_user_pd() {
+void* create_task_pd() {
     uint32_t pd_address = (uint32_t)p_alloc_frame();
     if (pd_address == 0) {
         return 0;
@@ -173,18 +171,18 @@ void* create_user_pd() {
 
     map_page(TEMP_MAPPING_VADDR, pd_address, PAGE_PRESENT | PAGE_WRITABLE);
 
-    uint32_t* user_pd = (uint32_t*)TEMP_MAPPING_VADDR;
+    uint32_t* task_pd = (uint32_t*)TEMP_MAPPING_VADDR;
     uint32_t* kernel_pd = (uint32_t*)PAGE_DIRECTORY;
 
     for(int i = 0; i < 768; i++) {
-        user_pd[i] = 0;
+        task_pd[i] = 0;
     }
 
     for(int i = 768; i < 1023; i++) {
-        user_pd[i] = kernel_pd[i];
+        task_pd[i] = kernel_pd[i];
     }
     
-    user_pd[1023] = (uint32_t)pd_address | PAGE_PRESENT | PAGE_WRITABLE;
+    task_pd[1023] = (uint32_t)pd_address | PAGE_PRESENT | PAGE_WRITABLE;
 
     uint32_t pde = TEMP_MAPPING_VADDR >> 22;
     uint32_t pte = (TEMP_MAPPING_VADDR >> 12) & 0x3FF; 

kernel/memory/mm.h

@@ -20,7 +20,7 @@ void* p_alloc_frame();
 
 uint32_t total_free_memory();
 
-void* create_user_pd();
+void* create_task_pd();
 
 void map_page(uint32_t vaddr, uint32_t paddr, uint32_t flags);
 

kernel/process.h

@@ -0,0 +1,20 @@
+#ifndef KPROCESS_H
+#define KPROCESS_H
+
+#include <stdint.h>
+
+typedef enum {
+    STATE_READY,
+    STATE_SLEEPING,
+    STATE_DEAD
+} process_state_t;
+
+typedef struct {
+    uint32_t pid;
+    uint32_t esp;
+    uint32_t cr3;
+    process_state_t state;
+    uint32_t sleep;
+} __attribute__((packed)) process_t;
+
+#endif 

kernel/scheduler.S

@@ -0,0 +1,12 @@
+.code32 
+.extern schedule_next_task
+.global yield 
+yield:
+    cli 
+    pushal 
+    push %esp 
+    call schedule_next_task
+    movl %eax, %esp 
+    popal 
+    sti 
+    ret

kernel/scheduler.c

@@ -0,0 +1,136 @@
+#include <lib/tasks.h>
+#include <lib/memory.h>
+
+#include <memory/mm.h>
+
+#include <stddef.h>
+
+#include "process.h"
+#include "scheduler.h"
+
+static process_t* process_table;
+static spinlock_t process_table_lock = {0};
+
+static int current_process = 0;
+static int total_processes = 0;
+
+extern uint32_t fetch_cr3();
+
+#define IDLE_TASK_PID 1
+static void idle_task() {
+  while (1) asm volatile("hlt");
+}
+
+uint32_t schedule_next_task(uint32_t current_esp) {
+    spin_lock(&process_table_lock);
+    process_table[current_process].esp = current_esp;
+
+    for (int i = 0; i < total_processes; i++) {
+        if (process_table[i].state == STATE_SLEEPING) {
+            if (process_table[i].sleep > 0) {
+                process_table[i].sleep--;
+            }
+
+            if (process_table[i].sleep == 0) {
+                process_table[i].state = STATE_READY;
+            }
+        }
+    }
+
+    int next_process = current_process;
+    int found_ready = 0;
+    while (1) {
+        next_process = (next_process + 1) % total_processes;
+        if (next_process != IDLE_TASK_PID && process_table[next_process].state == STATE_READY) {
+            found_ready = 1;
+            break;
+        }
+
+        if (next_process == current_process) {
+            break; 
+        }
+    }
+
+    if (!found_ready) {
+        if (process_table[current_process].state == STATE_READY) {
+            next_process = current_process;
+        } else {
+            next_process = IDLE_TASK_PID;
+        }
+    }
+
+    current_process = next_process;
+
+    if (fetch_cr3() != process_table[current_process].cr3) {
+        extern void load_pd(uint32_t table);
+        load_pd(process_table[current_process].cr3);
+    }
+
+    uint32_t rtn = process_table[current_process].esp;
+    spin_unlock(&process_table_lock);
+
+    return rtn;
+}
+
+void init_scheduler() {
+    process_table = kalloc(16 * sizeof(process_t));
+    total_processes = 0;
+
+    process_t* process = &process_table[total_processes];
+    process->pid = total_processes;
+    process->esp = 0;
+    process->cr3 = fetch_cr3();
+    process->state = STATE_READY;
+    process->sleep = 0;
+    total_processes++;
+
+    create_task((uint32_t)idle_task, fetch_cr3());
+
+    current_process = 0;
+}
+
+int create_task(uint32_t entry_point, uint32_t cr3) {
+    if (total_processes >= 16) {
+        return 0;
+    }
+
+    spin_lock(&process_table_lock);
+    process_t* process = &process_table[total_processes];
+    process->pid = total_processes;
+    process->cr3 = cr3;
+    process->state = STATE_READY;
+    process->sleep = 0;
+
+    void* stack_bottom = kalloc(4096);
+    uint32_t* esp = (uint32_t*)((uint32_t)stack_bottom + 4096);
+
+    *(--esp) = 0x0202;        // EFLAGS   
+    *(--esp) = 0x08;          // CS
+    *(--esp) = entry_point;   // EIP
+
+    *(--esp) = 0;             // EAX
+    *(--esp) = 0;             // ECX
+    *(--esp) = 0;             // EDX
+    *(--esp) = 0;             // EBX
+    *(--esp) = 0;             // ESP
+    *(--esp) = 0;             // EBP
+    *(--esp) = 0;             // ESI
+    *(--esp) = 0;             // EDI
+
+    process->esp = (uint32_t)esp;
+    spin_unlock(&process_table_lock);
+
+    total_processes++;
+    return 1;
+}
+
+void sleep(uint32_t ticks) {
+    if (ticks == 0) return;
+
+    spin_lock(&process_table_lock);
+    process_table[current_process].sleep = ticks;
+    process_table[current_process].state = STATE_SLEEPING;
+    spin_unlock(&process_table_lock);
+
+    yield();
+}

kernel/scheduler.h

@@ -0,0 +1,13 @@
+#ifndef KSCHEDULER_H
+#define KSCHEDULER_H
+
+#include <stdint.h>
+
+void init_scheduler();
+
+int create_task(uint32_t entry_point, uint32_t cr3);
+
+void sleep(uint32_t ticks);
+void yield();
+
+#endif

kernel/syscall.h

@@ -0,0 +1,6 @@
+#ifndef KSYSCALL_H
+#define KSYSCALL_H
+
+void syscall_handler();
+
+#endif

makefile

@@ -6,8 +6,7 @@ OSNAME := rockos
 C_SOURCES := $(shell find kernel -type f -name '*.c')
 S_SOURCES := $(shell find kernel -type f -name '*.S')
 
-# This correctly generates paths like obj/kernel/main.o
+OBJECTS := $(patsubst %, obj/%.o, $(C_SOURCES) $(S_SOURCES))
-OBJECTS := $(patsubst %.c, obj/%.o, $(C_SOURCES)) $(patsubst %.S, obj/%.o, $(S_SOURCES))
 
 CFLAGS  := -ffreestanding -O2 -Wall -Wextra -Ikernel
 LDFLAGS := -T kernel/linker.ld
@@ -25,11 +24,11 @@ $(OSNAME).iso: $(OSNAME).bin grub.cfg
 	cp grub.cfg isodir/boot/grub/grub.cfg
 	grub-mkrescue -o $(OSNAME).iso isodir
 
-obj/kernel/%.o: kernel/%.c
+obj/%.c.o: %.c
 	@mkdir -p $(dir $@)
 	$(CC) -c $< -o $@ $(CFLAGS)
 
-obj/kernel/%.o: kernel/%.S
+obj/%.S.o: %.S
 	@mkdir -p $(dir $@)
 	$(CC) -c $< -o $@ $(CFLAGS)