# HG changeset patch
# User John Tsiombikas <nuclear@member.fsf.org>
# Date 1313548383 -10800
# Node ID ef9cc2e902779edff44a07ec0e371fb960e9739d
# Parent  64a57418982436da44ad49a3f3f09ceb8092bc30
added a comment describing the push of just_forked address to the stack frame of the newly-forked process.

diff -r 64a574189824 -r ef9cc2e90277 src/proc.c
--- a/src/proc.c	Wed Aug 17 05:30:06 2011 +0300
+++ b/src/proc.c	Wed Aug 17 05:33:03 2011 +0300
@@ -176,7 +176,11 @@
 	/* child's return from fork returns 0 */
 	((struct intr_frame*)p->ctx.stack_ptr)->regs.eax = 0;
 
-	/* XXX describe */
+	/* we also need the address of just_forked in the stack, so that switch_stacks
+	 * called from context_switch, will return to just_forked when we first switch
+	 * to a newly forked process. just_forked then just calls intr_ret to return to
+	 * userspace with the already constructed interrupt frame (see above).
+	 */
 	p->ctx.stack_ptr -= 4;
 	*(uint32_t*)p->ctx.stack_ptr = (uint32_t)just_forked;