Turn threads into processes by giving them unique page directories

src/kernel/boot/TEMP-test_scheduler.c

@@ -1,16 +1,19 @@
 #include <proc.h>
 #include <sched.h>
 #include <mittos/graphics.h>
+#include <memory.h>
 
 extern gfx_context *term_fb;
 extern gfx_context kernel_fb;
 
+int *position = (void *)0x20000;
+
 void thread1()
 {
     int a = 1;
     gfx_context *ctx = framebuffer_make_subcontext(&kernel_fb, 700, 300, 100, 100);
     while(1) {
-        putCharacter(term_fb, 0, 0, RGB(255,255,0), RGB(0,0,0), '0'+(a++%10));
+        putCharacter(term_fb, *position, *position, RGB(255,255,0), RGB(0,0,0), '0'+(a++%10));
         flip(term_fb);
         draw_line(ctx, 0, 100, 50, ((a-1)%100), RGB(0,0,0));
         draw_line(ctx, 0, 100, 50, (a%100), RGB(255,0,0));
@@ -24,7 +27,7 @@ void thread2()
 {
     int a = 0;
     while(1) {
-        putCharacter(term_fb, 10, 10, RGB(0,255,255), RGB(0,0,0), 'A'+(a++%10));
+        putCharacter(term_fb, *position, *position, RGB(0,255,255), RGB(0,0,0), 'A'+(a++%10));
         flip(term_fb);
         sched_yield();
         
@@ -34,9 +37,19 @@ void thread2()
 
 void TEMP_test_scheduler()
 {
-    struct thread *th1 = new_thread(thread1);
+    struct process *th1 = new_process(thread1);
     scheduler_insert(th1);
 
-    struct thread *th2 = new_thread(thread2);
+    struct process *th2 = new_process(thread2);
     scheduler_insert(th2);
+
+    uint64_t p1 = pmm_alloc();
+    uint64_t p2 = pmm_alloc();
+    vmm_set_page(th1->P4, 0x20000, p1, PAGE_PRESENT);
+    vmm_set_page(th2->P4, 0x20000, p2, PAGE_PRESENT);
+    // Write different values into the position variable for the two processes
+    int *a = P2V(p1);
+    *a = 20;
+    a = P2V(p2);
+    *a = 70;
 }

src/kernel/cpu/registers.S

@@ -4,3 +4,8 @@
 load_idt:
     lidt [rdi]
     ret
+
+.global write_cr3
+write_cr3:
+    mov cr3, rdi
+    ret

src/kernel/include/cpu.h

@@ -5,3 +5,4 @@ void cpu_init();
 
 // cpu/registers.S
 void load_idt(void *);
+void write_cr3(uint64_t);

src/kernel/include/memory.h

@@ -32,7 +32,7 @@
     extern uint64_t kernel_P4;
 
     // memory/vmm.c
-    void vmm_init();
+    uint64_t new_P4();
     uint64_t vmm_get_page(uint64_t P4, uint64_t addr);
     int vmm_set_page(uint64_t P4, uint64_t addr, uint64_t page, uint16_t flags);
     void vmm_clear_page(uint64_t P4, uint64_t addr, int free);

src/kernel/include/proc.h

@@ -1,25 +1,26 @@
 #pragma once
 #include <stdint.h>
 
-struct thread
+struct process
 {
-    struct thread *q_next;
+    uint64_t pid;
-    uint64_t tid;
     void *stack_ptr;
     uint64_t state;
+    uint64_t P4;
+    struct process *q_next;
     uint8_t stack[];
 };
 
-// proc/thread.c
+// proc/process.c
-extern struct thread *current_thread;
+extern struct process *current_proc;
 
 // proc/swtch.S
 void *switch_stack(void *out, void *in);
 
-// proc/thread.c
+// proc/process.c
-struct thread *new_thread(void (*function)(void));
+struct process *new_process(void (*function)(void));
-struct thread *thread();
+struct process *proc();
 
 // proc/scheduler.c
-void scheduler_insert(struct thread *new);
+void scheduler_insert(struct process *new);
 void start_scheduler();

src/kernel/memory/vmm.c

@@ -42,6 +42,13 @@ static int touch_P1(uint64_t P4, uint64_t addr, uint16_t flags)
     return 0;
 }
 
+uint64_t new_P4()
+{
+    uint64_t p4 = pmm_alloc();
+    memcpy(P2V(p4), (void *)kernel_P4, PAGE_SIZE);
+    return p4;
+}
+
 uint64_t vmm_get_page(uint64_t P4, uint64_t addr)
 {
     if(P1_exists(P4, addr))

src/kernel/proc/process.c

@@ -0,0 +1,39 @@
+#include <stdint.h>
+#include <proc.h>
+#include <memory.h>
+
+struct swtch_stack
+{
+    uint64_t RBP;
+    uint64_t RBX;
+    uint64_t R12;
+    uint64_t R13;
+    uint64_t R14;
+    uint64_t R15;
+    uint64_t RBP2;
+    uint64_t ret;
+};
+
+static uint64_t next_pid = 1;
+
+struct process *current_proc;
+
+struct process *new_process(void (*function)(void))
+{
+    struct process *p = P2V(pmm_calloc());
+    p->pid = next_pid++;
+    p->stack_ptr = incptr(p, PAGE_SIZE - sizeof(struct swtch_stack));
+    p->q_next = 0;
+    p->P4 = new_P4();
+
+    struct swtch_stack *stck = p->stack_ptr;
+    stck->RBP = (uint64_t)&stck->RBP2;
+    stck->ret = (uint64_t)function;
+
+    return p;
+}
+
+struct process *proc()
+{
+    return current_proc;
+}

src/kernel/proc/scheduler.c

@@ -1,21 +1,22 @@
 #include <proc.h>
+#include <cpu.h>
 
 static struct {
-    struct thread *first;
+    struct process *first;
-    struct thread *last;
+    struct process *last;
 } run_q = {0,0};
 
-static struct thread *scheduler_thread;
+static struct process *scheduler_proc;
 
-static struct thread *scheduler_next()
+static struct process *scheduler_next()
 {
-    struct thread *ret = run_q.first;
+    struct process *ret = run_q.first;
     if(run_q.first && !(run_q.first = run_q.first->q_next))
         run_q.last = 0;
     return ret;
 }
 
-void scheduler_insert(struct thread *new)
+void scheduler_insert(struct process *new)
 {
     if(run_q.last) {
         run_q.last->q_next = new;
@@ -30,28 +31,29 @@ void scheduler()
 {
     while(1)
     {
-        struct thread *new = 0;
+        struct process *new = 0;
         while(!(new = scheduler_next()));
 
-        current_thread = new;
+        current_proc = new;
-        switch_stack(&scheduler_thread->stack_ptr, &new->stack_ptr);
+        write_cr3(new->P4);
+        switch_stack(&scheduler_proc->stack_ptr, &new->stack_ptr);
 
-        scheduler_insert(current_thread);
+        scheduler_insert(current_proc);
-        current_thread = 0;
+        current_proc = 0;
     }
 }
 
 long k_sched_yield(long, long, long, long, long, long)
 {
-    switch_stack(&current_thread->stack_ptr, &scheduler_thread->stack_ptr);
+    switch_stack(&current_proc->stack_ptr, &scheduler_proc->stack_ptr);
     return 0;
 }
 
 void start_scheduler()
 {
-    scheduler_thread = new_thread(scheduler);
+    scheduler_proc = new_process(scheduler);
-    scheduler_thread->tid = (uint64_t)-1;
+    scheduler_proc->pid = (uint64_t)-1;
 
     uint64_t stack;
-    switch_stack(&stack, &scheduler_thread->stack_ptr);
+    switch_stack(&stack, &scheduler_proc->stack_ptr);
 }

src/kernel/proc/thread.c

@@ -1,38 +0,0 @@
-#include <stdint.h>
-#include <proc.h>
-#include <memory.h>
-
-struct swtch_stack
-{
-    uint64_t RBP;
-    uint64_t RBX;
-    uint64_t R12;
-    uint64_t R13;
-    uint64_t R14;
-    uint64_t R15;
-    uint64_t RBP2;
-    uint64_t ret;
-};
-
-static uint64_t next_tid = 1;
-
-struct thread *current_thread;
-
-struct thread *new_thread(void (*function)(void))
-{
-    struct thread *th = P2V(pmm_calloc());
-    th->tid = next_tid++;
-    th->stack_ptr = incptr(th, PAGE_SIZE - sizeof(struct swtch_stack));
-    th->q_next = 0;
-
-    struct swtch_stack *stck = th->stack_ptr;
-    stck->RBP = (uint64_t)&stck->RBP2;
-    stck->ret = (uint64_t)function;
-
-    return th;
-}
-
-struct thread *thread()
-{
-    return current_thread;
-}