[USER] Fork syscall

kernel/include/syscall.h

@@ -42,3 +42,4 @@ typedef long (*syscall_handler_t)(long num, long, long, long, long, long, long);
 
 SYSCALL_DECL(write);
 SYSCALL_DECL(brk);
+SYSCALL_DECL(fork);

kernel/syscall/sys_proc.c

@@ -0,0 +1,27 @@
+#include <syscall.h>
+#include <process.h>
+#include <thread.h>
+#include <scheduler.h>
+#include <string.h>
+
+SYSCALL_DEF(fork)
+{
+  SYSCALL_INIT();
+
+  // Copy process and memory space
+  process_t *p = get_current_process();
+  process_t *new = process_spawn(p);
+
+  // Copy thread
+  thread_t *th = new_thread(0, 1);
+  memcpy(&th->r, &get_current_thread()->r, sizeof(registers_t));
+
+  // Make new thread return 0
+  th->r.rax = 0;
+  process_attach(new, th);
+  scheduler_insert(th);
+
+  // Return new pid
+  return new->pid;
+
+}

kernel/syscall/syscall.c

@@ -58,6 +58,7 @@ void syscall_init()
     SYSCALL_REGISTER(debug, SYS_DEBUG);
     SYSCALL_REGISTER(write, SYS_WRITE);
     SYSCALL_REGISTER(brk, SYS_BRK);
+    SYSCALL_REGISTER(fork, SYS_FORK);
   }
 
 }