Moved PCB for each process to kernel heap

src/Makefile.am

@@ -14,7 +14,7 @@ quark_kernel_SOURCES += x86/paging.c \
                         x86/isr.c \
                         x86/msr.c \
                         x86/context.c \
-                        x86/contextswitch.S \
+                        x86/load_context.S \
                         x86/preempt.S \
                         x86/quark_x86.c \
                         x86/entry.S 

src/kernel.c

@@ -57,7 +57,7 @@ void kernel_initialize(struct boot_info_t *boot_info)
     asm("hlt");*/
 
     irq_enable();
-    load_context(next_process(NULL));
+    load_context(next_process());
 }
 
 int set_syscall(int id, int arg_count, int pid, void *func_ptr)
@@ -219,13 +219,8 @@ int add_process(void *program_entry, int priority, physaddr_t address_space)
     return new_process->resource_id;
 }
 
-struct process_context_t *next_process(struct process_context_t *prev_state)
+struct process_context_t *next_process()
 {  
-    if(prev_state != NULL)
-    {
-        kernel.active_process->state = prev_state;
-        queue_insert(&kernel.priority_queue, kernel.active_process, kernel.active_process->priority);
-    }
     kernel.active_process = extract_min(&kernel.priority_queue);
     if(kernel.active_process != NULL)
     {
@@ -254,6 +249,19 @@ int terminate_process(size_t process_id)
     return S_OK;
 }
 
+int store_active_context(struct process_context_t *context, size_t size)
+{
+    if(kernel.active_process != NULL && kernel.active_process->state != NULL)
+    {
+        memcpy(kernel.active_process->state, context, size);
+        return S_OK;
+    }
+    else
+    {
+        return S_DOESNT_EXIST;
+    }
+}
+
 /*
 int accept_message(size_t process_id, struct message_t *message)
 {

src/x86/context.c

@@ -1,35 +1,45 @@
 #include "platform/context.h"
+#include "kernel.h"
 #include "mmgr.h"
+#include "heap.h"
 #include "string.h"
+#include "system.h"
 #include "x86/processstate.h"
 
 void *initialize_context(void *task_entry)
 {
-    /* 
-     * TODO: this implementation is a goddamn mess.
-     * Stack pointer is hardcoded, and the stack isn't resizable.
-     * PCB pointer is just a constant.
-     */
-    map_page(NULL, reserve_page(), PAGE_RW);
-    map_page((void*)0xFF3FF000, reserve_page(), PAGE_RW | PAGE_USERMODE);
-    unmap_page((void*)0xFF3FE000);
-    uint32_t flags;
-    asm("pushf; "
-        "mov (%%esp), %0; "
-        "popf; "
-        : "=r"(flags));
-    struct process_context_t *state = (struct process_context_t*)PCB_LOCATION;
-    memset(NULL, 0, page_size);
-    state->cs = 0x1B;
-    state->eip = (uint32_t)task_entry;
-    state->flags = (flags & ~0xFD) | 0x200;
-    state->ss = 0x23;
-    state->esp = 0xFF400000;
-    state->ebp = 0xFF400000;
-    return (void*)state;
+    physaddr_t stack_frame = reserve_page();
+    if(stack_frame % page_size != 0)
+    {
+        return NULL;
+    }
+    map_page((void*)&_kernel_start - page_size, stack_frame, PAGE_RW | PAGE_USERMODE);
+    unmap_page((void*)&_kernel_start - (2 * page_size));
+    struct process_context_t *context = kmalloc(sizeof(struct process_context_t));
+    if(context != NULL)
+    {
+       memset(context, 0, sizeof(struct process_context_t));
+       uint32_t flags;
+       asm("pushf; "
+           "mov (%%esp), %0; "
+           "popf; "
+           : "=r"(flags));
+       context->cs = 0x1B;
+       context->eip = (uint32_t)task_entry;
+       context->flags = (flags & ~0xFD) | 0x200;
+       context->ss = 0x23;
+       context->esp = &_kernel_start;
+       context->ebp = &_kernel_start;
+    }
+    return (void*)context;
 }
 
 void destroy_context(void *ctx)
 {
-    // Nothing to do...
+    kfree(ctx);
+}
+
+void save_context(struct process_context_t *context)
+{
+    store_active_context(context, sizeof(*context));
 }

src/x86/contextswitch.S

@@ -1,67 +0,0 @@
-.section .text
-
-/*
- * save_context(struct process_state_t *context, struct interrupt_frame_t *frame)
- */
- .global save_context
- .type save_context, @function
-save_context:
-    push %edi
-    push %esi
-    push %eax
-    mov $0x10, %ax
-    mov %ax, %ds
-    mov %ax, %es
-    mov %ax, %fs
-    mov %ax, %gs
-    mov 16(%esp), %eax
-    mov %ebx, 0x04(%eax)
-    mov %ecx, 0x08(%eax)
-    mov %edx, 0x0C(%eax)
-    mov %edi, 0x10(%eax)
-    mov %esi, 0x14(%eax)
-    mov %ebp, 0x18(%eax)
-    mov %eax, %edi
-    pop %eax
-    mov %eax, 0x00(%edi)
-    mov 16(%esp), %esi
-    mov 0x10(%esi), %eax
-    mov %eax, 0x1C(%edi)
-    mov 0x0C(%esi), %eax
-    mov %eax, 0x20(%edi)
-    mov 0x08(%esi), %eax
-    mov %eax, 0x2C(%edi)
-    mov 0x04(%esi), %eax
-    mov %eax, 0x24(%edi)
-    mov 0x00(%esi), %eax
-    mov %eax, 0x28(%edi)
-    pop %esi
-    pop %edi
-    ret
-
-/*
- * load_context(struct process_state_t *context)
- */
-.global load_context
-.type load_context, @function
-load_context:
-    mov 4(%esp), %eax
-    push 0x1C(%eax)
-    push 0x20(%eax)
-    push 0x2C(%eax)
-    push 0x24(%eax)
-    push 0x28(%eax)
-    push 0x00(%eax)
-    mov 0x04(%eax), %ebx
-    mov 0x08(%eax), %ecx
-    mov 0x0C(%eax), %edx
-    mov 0x10(%eax), %edi
-    mov 0x14(%eax), %esi
-    mov 0x18(%eax), %ebp
-    mov 0x1C(%eax), %ax
-    mov %ax, %ds
-    mov %ax, %es
-    mov %ax, %fs
-    mov %ax, %gs
-    pop %eax
-    iret

src/x86/load_context.S

@@ -0,0 +1,28 @@
+.section .text
+
+/*
+ * load_context(struct process_state_t *context)
+ */
+.global load_context
+.type load_context, @function
+load_context:
+    mov 4(%esp), %eax
+    push 0x1C(%eax)
+    push 0x20(%eax)
+    push 0x2C(%eax)
+    push 0x24(%eax)
+    push 0x28(%eax)
+    push 0x00(%eax)
+    mov 0x04(%eax), %ebx
+    mov 0x08(%eax), %ecx
+    mov 0x0C(%eax), %edx
+    mov 0x10(%eax), %edi
+    mov 0x14(%eax), %esi
+    mov 0x18(%eax), %ebp
+    mov 0x1C(%eax), %ax
+    mov %ax, %ds
+    mov %ax, %es
+    mov %ax, %fs
+    mov %ax, %gs
+    pop %eax
+    iret

src/x86/preempt.S

@@ -25,14 +25,63 @@ isr_syscall:
 .global isr_preempt
 .type isr_preempt, @function
 isr_preempt:
+
+    // Disable interrupts for now
     cli
+
+    // Save process's base pointer
+    push %ebp
+
+    // Save base pointer; it points to the interrupt stack frame
+    mov %esp, %ebp
+    sub $4, %ebp
+
+    // Save EAX on stack so it can be used as a buffer
+    push %eax
+
+    // Load EFLAGS, then push it onto stack
+    mov 8(%ebp), %eax
+    push %eax
+
+    // Load EIP, then push it onto stack
+    mov 16(%ebp), %eax
+    push %eax
+
+    // Load CS, then push it onto stack
+    mov 12(%ebp), %eax
+    push %eax
+
+    // Load ESP, then push it onto stack
+    mov 4(%ebp), %eax
+    push %eax
+
+    // Load SS, then push it onto stack
+    mov (%ebp), %eax
+    push %eax
+
+    // Load EBP, then push it onto stack
+    mov -4(%ebp), %eax
+    push %eax
+
+    // Push GP registers onto stack
+    push %esi
+    push %edi
+    push %edx
+    push %ecx
+    push %ebx
+
+    // Restore saved value of EAX, then push it onto stack
+    mov -8(%ebp), %eax
+    push %eax
+
+    // Push pointer to the process context saved on the stack
     push %esp
-    push $0x800
+
     call save_context
-    add $8, %esp
-    push $0x800
+    mov %ebp, %esp
+
     call next_process
-    add $8, %esp
+
     push %eax
     call load_context