1 files changed, 39 insertions, 18 deletions

diff --git a/main.c b/main.c
index 60cd1b3..1a49bc6 100644
--- a/main.c
+++ b/main.c
@@ -6,23 +6,42 @@
 #include "x86.h"
 
 static void bootothers(void);
-static void mpmain(void) __attribute__((noreturn));
+static void mpmain(void);
+void jkstack(void)  __attribute__((noreturn));
+void mainc(void);
 
 // Bootstrap processor starts running C code here.
 int
 main(void)
 {
-  mpinit(); // collect info about this machine
+  mpinit();        // collect info about this machine
   lapicinit(mpbcpu());
-  ksegment();
+  ksegment();      // set up segments
   picinit();       // interrupt controller
   ioapicinit();    // another interrupt controller
   consoleinit();   // I/O devices & their interrupts
   uartinit();      // serial port
-cprintf("cpus %p cpu %p\n", cpus, cpu);
-  cprintf("\ncpu%d: starting xv6\n\n", cpu->id);
+  pminit();        // discover how much memory there is
+  jkstack();       // call mainc() on a properly-allocated stack 
+}
+
+void
+jkstack(void)
+{
+  char *kstack = kalloc(PGSIZE);
+  if (!kstack)
+    panic("jkstack\n");
+  char *top = kstack + PGSIZE;
+  asm volatile("movl %0,%%esp" : : "r" (top));
+  asm volatile("call mainc");
+  panic("jkstack");
+}
 
-  kinit();         // physical memory allocator
+void
+mainc(void)
+{
+  cprintf("\ncpu%d: starting xv6\n\n", cpu->id);
+  kvmalloc();      // initialize the kernel page table
   pinit();         // process table
   tvinit();        // trap vectors
   binit();         // buffer cache
@@ -38,20 +57,21 @@ cprintf("cpus %p cpu %p\n", cpus, cpu);
   mpmain();
 }
 
-// Bootstrap processor gets here after setting up the hardware.
-// Additional processors start here.
+// Common CPU setup code.
+// Bootstrap CPU comes here from mainc().
+// Other CPUs jump here from bootother.S.
 static void
 mpmain(void)
 {
-  if(cpunum() != mpbcpu())
+  if(cpunum() != mpbcpu()) {
+    ksegment();
     lapicinit(cpunum());
-  ksegment();
-  cprintf("cpu%d: mpmain\n", cpu->id);
-  idtinit();
+  }
+  vmenable();        // turn on paging
+  cprintf("cpu%d: starting\n", cpu->id);
+  idtinit();       // load idt register
   xchg(&cpu->booted, 1);
-
-  cprintf("cpu%d: scheduling\n", cpu->id);
-  scheduler();
+  scheduler();     // start running processes
 }
 
 static void
@@ -62,8 +82,9 @@ bootothers(void)
   struct cpu *c;
   char *stack;
 
-  // Write bootstrap code to unused memory at 0x7000.
-  code = (uchar*)0x7000;
+  // Write bootstrap code to unused memory at 0x7000.  The linker has
+  // placed the start of bootother.S there.
+  code = (uchar *) 0x7000;
   memmove(code, _binary_bootother_start, (uint)_binary_bootother_size);
 
   for(c = cpus; c < cpus+ncpu; c++){
@@ -76,7 +97,7 @@ bootothers(void)
     *(void**)(code-8) = mpmain;
     lapicstartap(c->id, (uint)code);
 
-    // Wait for cpu to get through bootstrap.
+    // Wait for cpu to finish mpmain()
     while(c->booted == 0)
       ;
   }