Multi-user multitasking

arch/i686/paging.c

@@ -49,7 +49,7 @@ void set_page_table_entry(size_t address, void* ptr)
 struct x86_Page_Table create_table;
 
 void setup_paging() {
-    struct x86_Page_Table* kernel = get_table(768);
+    struct x86_Page_Table* kernel = get_table(0x300);
     uint16_t i = 0;
     while (kernel[i].present == 0) {
         i++;

include/kernel/elf.h

@@ -1,5 +1,5 @@
 #include <stdint.h>
 #include <stddef.h>
 
-void run_program(uint8_t* code, size_t code_length, uint8_t* data, size_t data_length);
+void run_program(void* code, size_t code_length, void* data, size_t data_length, void* code_destination, void* data_destination);
 

include/kernel/heap.h

@@ -4,17 +4,23 @@
 
 extern struct Heap_Metadata global_heap;
 
+#ifndef __Heap_Metadata
+#define __Heap_Metadata
 struct Heap_Metadata {
     struct Heap_Block* start;
     size_t size;
 };
+#endif
 
+#ifndef __Heap_Block 
+#define __Heap_Block
 struct Heap_Block {
     struct Heap_Block* next;
     size_t size;
     bool used;
     void* data;
 };
+#endif
 
 void heap_init();
 void* malloc(size_t size);

include/kernel/task.h

@@ -1,5 +1,6 @@
 #include <stdint.h>
 #include <stddef.h>
+#include <kernel/heap.h>
 
 struct CPUState {
     size_t eax;
@@ -18,6 +19,10 @@ struct CPUState {
 
 struct Task {
     struct CPUState state;
+    size_t size;
+    struct Heap_Block* code;
+    struct Heap_Block* data;
+    bool needs_pages;
 };
 
 void switch_task(

kernel/elf.c

@@ -14,21 +14,18 @@ static void* memcpy(void* restrict dstptr, const void* restrict srcptr, size_t s
     return dstptr;
 }
 
-void run_program(uint8_t* code, size_t code_length, uint8_t* data, size_t data_length)
+void run_program(void* code, size_t code_length, void* data, size_t data_length, struct Heap_Block* code_block, struct Heap_Block* data_block)
 {
     // TODO: Replace following lines with malloc calls and paging calls
-    uint8_t* userland_code = (uint8_t*) 0x00000000;
+    memcpy(code_block->data, code, code_length);
-    uint8_t* userland_data = (uint8_t*) 0x00400000;
+    memcpy(data_block->data, data, data_length);
-
-    memcpy(userland_code, code, code_length);
-    memcpy(userland_data, data, data_length);
 
     struct CPUState target = {
-        .eip = (size_t) userland_code,
+        .eip = (size_t) 0x00400000,
-        .esp = 0x00400800,
+        .esp = (size_t) 0x00801000,
-        .eax = 0x00400000,
+        .eax = (size_t) 0x00800000,
-        .ebx = 0,
+        .ebx = data_length,
-        .ecx = 0,
+        .ecx = 0x00400000,
         .edx = 0,
         .cs = 0x18 | 0x3,
         .ds = 0x20 | 0x3,
@@ -40,6 +37,9 @@ void run_program(uint8_t* code, size_t code_length, uint8_t* data, size_t data_l
 
     struct Task task = {
         .state = target,
+        .needs_pages = true,
+        .code = code_block,
+        .data = data_block,
     };
 
     add_task(task);

kernel/heap.c

@@ -4,7 +4,7 @@
 #include <kernel/tty.h>
 #include <debugging.h>
 
-#define HEAP_SIZE (1 << 16)
+#define HEAP_SIZE (1 << 12)
 #define NUM_PAGES (128)
 
 uint8_t global_heap_data[HEAP_SIZE + sizeof(struct Heap_Block)];
@@ -169,6 +169,9 @@ void free(void *ptr)
     }
 
     start->next = current;
+    if (start->next == start) {
+        terminal_writestring("Woops");
+    }
     start->size = (size_t)start->next - (size_t)start->data;
 }
 

kernel/kernel.c

@@ -18,13 +18,15 @@ uint8_t program[] = {
     0xff, 0xe1, // jmp *%ecx
 };
 
-uint8_t data[] = "Hello From Userspace\n";
+uint8_t data1[] = "Hello From Userspace 1\n\0";
+uint8_t data2[] = "Hello 2\n\0";
 
-uint8_t kernel_data[] = "Hello From Kernelspace\n";
+uint8_t kernel_data[] = "Hello From Kernelspace\n\0";
 // uint8_t data[] = {};
 
 void kernel_main(void) 
 {
+    asm("cli");
     /* Initialize terminal interface */
     terminal_initialize();
     terminal_writestring("Hello from Kernelspace\n");
@@ -38,32 +40,32 @@ void kernel_main(void)
 
     terminal_writestring("Woaw\n");
 
-    struct Heap_Block* block;
+    struct Heap_Block* code_block_1;
-    void* code_page = alloc_page(1, &block);
+    struct Heap_Block* data_block_1;
-    void* data_page = alloc_page(1, &block);
 
-    set_page_table_entry(0, code_page);
+    alloc_page(2, &code_block_1);
-    set_page_table_entry(0x00400000, data_page);
+    alloc_page(2, &data_block_1);
 
-    *(int*)0 = 1;
+    struct Heap_Block* code_block_2;
+    struct Heap_Block* data_block_2;
 
-    while (true) { }
+    alloc_page(2, &code_block_2);
+    alloc_page(2, &data_block_2);
 
-    /* asm("cli");
+    // set_page_table_entry(0, code_page);
+    // set_page_table_entry(0x00400000, data_page);
 
-    run_program(program, sizeof(program), data, sizeof(data));
+    run_program(program, sizeof(program), data1, sizeof(data1), code_block_1, data_block_1);
+    run_program(program, sizeof(program), data2, sizeof(data2), code_block_2, data_block_2);
 
     asm("sti");
-    asm("int $0x20");
 
     int i = 0;
     while (true) {
         i += 1;
-        if (i == 1 << 16) {
+        if (i == 1 << 1) {
-            asm("mov %0, %%eax" :: "r" (kernel_data) );
+            asm("mov $0, %%ecx; int $0x80" :: "a" (kernel_data), "b" (sizeof(kernel_data)));
-            asm("mov $0, %ecx");
-            asm("int $0x80");
             i = 0;
         }
-    } */
+    }
 }

kernel/syscall.c

@@ -1,8 +1,9 @@
 #include <kernel/tty.h>
 #include <kernel/io/keyboard.h>
 #include <debugging.h>
+#include <kernel/heap.h>
 
-static void print(char* buffer) 
+static void print(char* buffer, size_t length) 
 {
     terminal_writestring(buffer);
 }
@@ -23,14 +24,14 @@ static void input(char* buffer)
     }
 }
 
-void _syscall(uint32_t a, uint32_t b, uint32_t c)
+void _syscall(size_t a, size_t b, size_t c)
 {
-    switch (c) {
+    // switch (c) {
-        case 0x00:
+        // case 0x00:
-            print((char*) a);
+            print((char*) a, b);
-            break;
+            // break;
-        case 0x01:
+        // case 0x01:
-            input((char*) a);
+            // input((char*) a);
-            break;
+            // break;
-    }
+    // }
 }

kernel/task.c

@@ -2,6 +2,7 @@
 #include <kernel/heap.h>
 #include <kernel/tty.h>
 #include <debugging.h>
+#include <kernel/paging.h>
 
 struct Task* tasks;
 size_t tasks_capacity;
@@ -14,13 +15,14 @@ void setup_tasks()
     tasks = malloc(sizeof(*tasks));
     tasks[0].state.cs = 8;
     tasks[0].state.ds = 16;
+    tasks[0].needs_pages = false;
     tasks_capacity = 1;
     num_tasks = 1;
 }
 
 void add_task(struct Task task)
 {
-    asm("cli");
+    // asm("cli");
     if (num_tasks == tasks_capacity) {
         struct Task* temp = malloc(sizeof(*tasks) * tasks_capacity * 2);
 
@@ -36,7 +38,7 @@ void add_task(struct Task task)
 
     tasks[num_tasks] = task;
     num_tasks++;
-    asm("sti");
+    // asm("sti");
 }
 
 size_t ss;
@@ -104,7 +106,8 @@ static void save_state(
     current_task %= num_tasks;
 }
 
-void next_task() {
+void next_task() 
+{
     struct CPUState s = tasks[current_task].state;
 
     ss = s.ds;
@@ -116,6 +119,15 @@ void next_task() {
     print_hex_bytes(&tasks[current_task].state.eip, 4);
     terminal_writestring("\n");
 
+    if (tasks[current_task].needs_pages) {
+        set_page_directory_entry(0x00400000,        tasks[current_task].code->data + 4096);
+        set_page_directory_entry(0x00800000, tasks[current_task].data->data + 4096);
+        set_page_table_entry(0x00400000,        tasks[current_task].code->data);
+        set_page_table_entry(0x00800000, tasks[current_task].data->data);
+        asm("	movl	%cr3,%eax; \
+	            movl	%eax,%cr3;");
+    }
+
     if ((cs & 3) == 0) {
         jump_kernel(
             s.edi,