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, 1 insertions, 0 deletions

diff --git a/sys/include/arch/amd64/cpu.h b/sys/include/arch/amd64/cpu.h
index 16936e9..2ce363c 100644
--- a/sys/include/arch/amd64/cpu.h
+++ b/sys/include/arch/amd64/cpu.h
@@ -42,6 +42,7 @@ struct cpu_info {
     size_t lapic_tmr_freq;
     struct tss_entry *tss;
     struct proc *curtd;
+    struct cpu_info *self;
 };
 
 void cpu_startup(struct cpu_info *ci);