kernel/amd64: Handle the user GS segment register

This commit introduces usage of swapgs to switch out the GS register
with the user GS register. An md_td_kick() function is also introduced
to start up user threads. The this_cpu() function uses the GS register
to read the current CPU structure using a new "self" field.

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/sys/kern/kern_exec.c b/sys/kern/kern_exec.c
index b21404b..7825448 100644
--- a/sys/kern/kern_exec.c
+++ b/sys/kern/kern_exec.c
@@ -98,11 +98,11 @@ execve(struct proc *td, const struct execve_args *args)
     setregs(td, &prog, stack_top);
 
     /*
-     * Done, reset flags and yield
+     * Done, reset flags and start the user thread.
      *
      * XXX: PROC_EXEC is unset by the scheduler so it
      *      can properly start the new exec'd program.
      */
     td->flags &= ~PROC_INEXEC;
-    sched_enter();
+    md_td_kick(td);
 }