test: store curproc at top of stack

I don't actually think this is worthwhile, but I figured
I would check it in before reverting it, so that it can
be in the revision history.

Pros:
  * curproc doesn't need to turn on/off interrupts
  * scheduler doesn't have to edit curproc anymore

Cons:
  * it's ugly
  * all the stack computation is more complicated.
  * it doesn't actually simplify anything but curproc,
    and even curproc is harder to follow.

1 files changed, 5 insertions, 3 deletions

diff --git a/main.c b/main.c
index 464112b..0f1acc8 100644
--- a/main.c
+++ b/main.c
@@ -42,12 +42,14 @@ main(void)
   userinit();      // first user process
 
   // Allocate scheduler stacks and boot the other CPUs.
-  for(i=0; i<ncpu; i++)
+  for(i=0; i<ncpu; i++){
     cpus[i].stack = kalloc(KSTACKSIZE);
+    *(void**)(cpus[i].stack + KSTACKTOP) = 0;
+  }
   bootothers();
 
   // Switch to our scheduler stack and continue with mpmain.
-  asm volatile("movl %0, %%esp" : : "r" (cpus[bcpu].stack+KSTACKSIZE));
+  asm volatile("movl %0, %%esp" : : "r" (cpus[bcpu].stack+KSTACKTOP));
   mpmain();
 }
 
@@ -84,7 +86,7 @@ bootothers(void)
       continue;
 
     // Fill in %esp, %eip and start code on cpu.
-    *(void**)(code-4) = c->stack + KSTACKSIZE;
+    *(void**)(code-4) = c->stack + KSTACKTOP;
     *(void**)(code-8) = mpmain;
     lapic_startap(c->apicid, (uint)code);