Magic commit

Some things work, others don't.

3 files changed, 246 insertions, 0 deletions

diff --git a/src/kernel/tasks/process.asm b/src/kernel/tasks/process.asm
new file mode 100644
index 0000000..a46ac3d
--- /dev/null
+++ b/src/kernel/tasks/process.asm
@@ -0,0 +1,48 @@
+[GLOBAL read_eip]
+read_eip:
+    pop eax
+    jmp eax
+
+[GLOBAL copy_page_physical]
+copy_page_physical:
+    push ebx
+    pushf
+
+    cli
+
+    mov ebx, [esp+12]
+    mov ecx, [esp+16]
+
+    mov edx, cr0
+    and edx, 0x7fffffff
+    mov cr0, edx
+
+    mov edx, 1024
+
+.loop:
+    mov eax, [ebx]
+    mov [ecx], eax
+    add ebx, 4
+    add ecx, 4
+    dec edx
+    jnz .loop
+
+    mov edx, cr0
+    or  edx, 0x80000000
+    mov cr0, edx
+
+    popf
+    pop ebx
+    ret
+
+[GLOBAL perform_task_switch]
+perform_task_switch:
+     cli
+     mov ecx, [esp+4]
+     mov eax, [esp+8]
+     mov ebp, [esp+12]
+     mov esp, [esp+16]
+     mov cr3, eax
+     mov eax, 0x12345
+     sti
+     jmp ecx
\ No newline at end of file
diff --git a/src/kernel/tasks/task.c b/src/kernel/tasks/task.c
new file mode 100644
index 0000000..e6caf9a
--- /dev/null
+++ b/src/kernel/tasks/task.c
@@ -0,0 +1,168 @@
+#include <kernel/memory/paging.h>
+#include <kernel/tasks/task.h>
+#include <kernel/memory/kheap.h>
+#include <kernel/lib/lib.h>
+#include <kernel/gdt/gdt.h>
+#include <kernel/system.h>
+
+volatile task_t *current_task;
+volatile task_t *ready_queue;
+
+extern page_directory_t *kernel_directory;
+extern page_directory_t *current_directory;
+
+extern uint32_t read_eip();
+
+uint32_t next_pid = 1;
+
+void tasking_install()
+{
+    asm ("cli");
+    move_stack((void *) 0xE0000000, 0x2000);
+
+    current_task = ready_queue = (task_t *) kmalloc(sizeof(task_t));
+    current_task->id = (int) next_pid++;
+    current_task->esp = current_task->ebp = 0;
+    current_task->eip = 0;
+    current_task->page_directory = current_directory;
+    current_task->next = 0;
+    current_task->kernel_stack = kmalloc_a(KERNEL_STACK_SIZE);
+
+    vga_log("Installed Tasking");
+    asm ("sti");
+}
+
+void move_stack(void *new_stack_start, uint32_t size)
+{
+    for (uint32_t i = (uint32_t) new_stack_start;
+         i >= ((uint32_t) new_stack_start - size);
+         i -= 0x1000) {
+        paging_alloc_frame(paging_get_page(i, 1, current_directory), 0, 1);
+    }
+
+    uint32_t pd_addr;
+    asm volatile ("mov %%cr3, %0" : "=r" (pd_addr));
+    asm volatile ("mov %0, %%cr3" : : "r" (pd_addr));
+
+    uint32_t old_stack_pointer; asm volatile ("mov %%esp, %0" : "=r" (old_stack_pointer));
+    uint32_t old_base_pointer;  asm volatile ("mov %%ebp, %0" : "=r" (old_base_pointer));
+
+    uint32_t offset = (uint32_t) new_stack_start - initial_esp;
+
+    uint32_t new_stack_pointer = old_stack_pointer + offset;
+    uint32_t new_base_pointer = old_base_pointer + offset;
+
+    memcpy((void *) new_stack_pointer, (void *) old_stack_pointer, initial_esp - old_stack_pointer);
+
+    for (uint32_t i = (uint32_t) new_stack_start; i > (uint32_t) new_stack_start - size; i -= 4) {
+        uint32_t tmp = *(uint32_t *) i;
+        if ((old_stack_pointer < tmp) && (tmp < initial_esp)) {
+            tmp = tmp + offset;
+            uint32_t *tmp2 = (uint32_t *) i;
+            *tmp2 = tmp;
+        }
+    }
+
+    asm volatile ("mov %0, %%esp" : : "r" (new_stack_pointer));
+    asm volatile ("mov %0, %%ebp" : : "r" (new_base_pointer));
+}
+
+extern void perform_task_switch(uint32_t, uint32_t, uint32_t, uint32_t);
+
+void switch_task()
+{
+    if (!current_task)
+        return;
+
+    uint32_t esp, ebp, eip;
+    asm volatile ("mov %%esp, %0" : "=r"(esp));
+    asm volatile ("mov %%ebp, %0" : "=r"(ebp));
+
+    eip = read_eip();
+
+    if (eip == 0x12345)
+        return;
+
+    current_task->eip = eip;
+    current_task->esp = esp;
+    current_task->ebp = ebp;
+
+    current_task = current_task->next;
+    if (!current_task) current_task = ready_queue;
+
+    eip = current_task->eip;
+    esp = current_task->esp;
+    ebp = current_task->ebp;
+
+    current_directory = current_task->page_directory;
+
+    set_kernel_stack(current_task->kernel_stack + KERNEL_STACK_SIZE);
+
+    perform_task_switch(eip, current_directory->physicalAddr, ebp, esp);
+}
+
+int fork()
+{
+    asm ("cli");
+
+    task_t *parent_task = (task_t *) current_task;
+
+    page_directory_t *directory = paging_clone_directory(current_directory);
+
+    task_t *new_task = (task_t *) kmalloc(sizeof(task_t));
+    new_task->id = (int) next_pid++;
+    new_task->esp = new_task->ebp = 0;
+    new_task->eip = 0;
+    new_task->page_directory = directory;
+    current_task->kernel_stack = kmalloc_a(KERNEL_STACK_SIZE);
+    new_task->next = 0;
+
+    task_t *tmp_task = (task_t *) ready_queue;
+    while (tmp_task->next)
+        tmp_task = tmp_task->next;
+    tmp_task->next = new_task;
+
+    uint32_t eip = read_eip();
+
+    if (current_task == parent_task) {
+        uint32_t esp; asm volatile ("mov %%esp, %0" : "=r"(esp));
+        uint32_t ebp; asm volatile ("mov %%ebp, %0" : "=r"(ebp));
+        new_task->esp = esp;
+        new_task->ebp = ebp;
+        new_task->eip = eip;
+        asm volatile ("sti");
+
+        return new_task->id;
+    } else {
+        return 0;
+    }
+}
+
+int getpid()
+{
+    return current_task->id;
+}
+
+void switch_to_usermode(uint32_t binary)
+{
+    set_kernel_stack(current_task->kernel_stack + KERNEL_STACK_SIZE);
+
+    info("Switching to user mode...");
+
+    asm volatile ("\
+      cli; \
+      mov $0x23, %%ax; \
+      mov %%ax, %%ds; \
+      mov %%ax, %%es; \
+      mov %%ax, %%fs; \
+      mov %%ax, %%gs; \
+      mov %%esp, %%eax; \
+      pushl $0x23; \
+      pushl %%esp; \
+      pushf; \
+      pushl $0x1B; \
+      push %0; \
+      iret; \
+    1: \
+      " : : "r" (binary));
+}
\ No newline at end of file
diff --git a/src/kernel/tasks/task.h b/src/kernel/tasks/task.h
new file mode 100644
index 0000000..97aeb15
--- /dev/null
+++ b/src/kernel/tasks/task.h
@@ -0,0 +1,30 @@
+#ifndef MELVIX_TASK_H
+#define MELVIX_TASK_H
+
+#include <stdint.h>
+#include <kernel/memory/paging.h>
+
+#define KERNEL_STACK_SIZE 2048
+
+typedef struct task {
+    int id;
+    uint32_t esp, ebp;
+    uint32_t eip;
+    page_directory_t *page_directory;
+    uint32_t kernel_stack;
+    struct task *next;
+} task_t;
+
+void tasking_install();
+
+void switch_task();
+
+int fork();
+
+void move_stack(void *new_stack_start, uint32_t size);
+
+int getpid();
+
+void switch_to_usermode(uint32_t);
+
+#endif