improve swtch comment

1ab23170 · Robert Morris · 4638cabf · 1ab23170
--- a/swtch.S
+++ b/swtch.S
@@ -2,8 +2,9 @@
 #
 #   void swtch(struct context **old, struct context *new);
 # 
-# Save current register context in old
+# Save the current registers on the stack, creating
-# and then load register context from new.
+# a struct context, and save its address in *old.
+# Switch stacks to new and pop previously-saved registers.
 .globl swtch
 swtch: