kitten/arch/x86_64/kernel/task.c

   1 #include <lwk/kernel.h>
   2 #include <lwk/aspace.h>
   3 #include <lwk/task.h>
   4 #include <arch/ptrace.h>
   5
   6 int
   7 arch_task_create(struct task_struct *task,
   8                  const start_state_t *start_state)
   9 {
  10         struct pt_regs *regs;
  11         kaddr_t kstack_top;
  12         kaddr_t initial_ksp;
  13
  14         regs        = ((struct pt_regs *)((kaddr_t)task + TASK_SIZE)) - 1;
  15         kstack_top  = (kaddr_t)(regs + 1);
  16         initial_ksp = (kaddr_t)regs;
  17
  18         task->arch.thread.rsp0    = kstack_top;
  19         task->arch.thread.rsp     = initial_ksp;
  20         task->arch.thread.userrsp = start_state->stack_ptr;
  21
  22         /* Mark this as a new-task... arch_context_switch() checks this flag */
  23         task->arch.flags = TF_NEW_TASK;
  24
  25         /* Task's address space is from [0, task->addr_limit) */
  26         task->arch.addr_limit = PAGE_OFFSET;
  27
  28         /* Initialize FPU state */
  29         task->arch.thread.i387.fxsave.cwd = 0x37f;
  30         task->arch.thread.i387.fxsave.mxcsr = 0x1f80;
  31
  32         /* CPU control unit uses these fields to start the user task running */
  33         if (start_state->aspace_id == KERNEL_ASPACE_ID) {
  34                 regs->ss     = __KERNEL_DS;
  35                 regs->rsp    = (vaddr_t)task + TASK_SIZE;
  36                 regs->eflags = (1 << 9);  /* enable interrupts */
  37                 regs->cs     = __KERNEL_CS;
  38         } else {
  39                 regs->ss     = __USER_DS;
  40                 regs->rsp    = start_state->stack_ptr;
  41                 regs->eflags = (1 << 9);  /* enable interrupts */
  42                 regs->cs     = __USER_CS;
  43         }
  44         regs->rip = start_state->entry_point;
  45
  46         return 0;
  47 }