From 2cf6b32d4dbc915f5d3b2d7b0e382c0ad20299be Mon Sep 17 00:00:00 2001
From: Robert Morris <rtm@nephron.lcs.mit.edu>
Date: Thu, 5 Aug 2010 14:15:03 -0400
Subject: move jkstack to main.c replace jstack with asm()s

---
 main.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

(limited to 'main.c')

diff --git a/main.c b/main.c
index 78cd334..8be66e3 100644
--- a/main.c
+++ b/main.c
@@ -7,7 +7,8 @@
 
 static void bootothers(void);
 static void mpmain(void);
-void jkstack(void) __attribute__((noreturn));
+void jkstack(void)  __attribute__((noreturn));
+void mainc(void);
 
 // Bootstrap processor starts running C code here.
 int
@@ -21,13 +22,24 @@ main(void)
   consoleinit();   // I/O devices & their interrupts
   uartinit();      // serial port
   pminit();        // physical memory for kernel
-  jkstack();       // Jump to mainc on a proper-allocated kernel stack 
+  jkstack();       // Jump to 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");
 }
 
 void
 mainc(void)
 {
-  cprintf("cpus %p cpu %p\n", cpus, cpu);
   cprintf("\ncpu%d: starting xv6\n\n", cpu->id);
   kvmalloc();      // allocate the kernel page table
   pinit();         // process table
@@ -52,14 +64,12 @@ mpmain(void)
 {
   if(cpunum() != mpbcpu()) {
     ksegment();
-    cprintf("other cpu\n");
     lapicinit(cpunum());
   }
   vminit();        // Run with paging on each processor
-  cprintf("cpu%d: mpmain\n", cpu->id);
+  cprintf("cpu%d: starting\n", cpu->id);
   idtinit();
   xchg(&cpu->booted, 1);
-  cprintf("cpu%d: scheduling\n", cpu->id);
   scheduler();
 }
 
-- 
cgit v1.2.3


From 1afc9d3fcaa7c5992659bb8b69f639b746dda2bc Mon Sep 17 00:00:00 2001
From: Robert Morris <rtm@nephron.lcs.mit.edu>
Date: Thu, 5 Aug 2010 21:16:55 -0400
Subject: add some comments find out the hard way why user and kernel must have
 separate segment descriptors

---
 main.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

(limited to 'main.c')

diff --git a/main.c b/main.c
index 8be66e3..a6088cb 100644
--- a/main.c
+++ b/main.c
@@ -16,13 +16,13 @@ main(void)
 {
   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
-  pminit();        // physical memory for kernel
-  jkstack();       // Jump to mainc on a properly-allocated stack 
+  pminit();        // discover how much memory there is
+  jkstack();       // call mainc() on a properly-allocated stack 
 }
 
 void
@@ -41,7 +41,7 @@ void
 mainc(void)
 {
   cprintf("\ncpu%d: starting xv6\n\n", cpu->id);
-  kvmalloc();      // allocate the kernel page table
+  kvmalloc();      // initialze the kernel page table
   pinit();         // process table
   tvinit();        // trap vectors
   binit();         // buffer cache
@@ -57,8 +57,9 @@ mainc(void)
   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)
 {
@@ -66,11 +67,11 @@ mpmain(void)
     ksegment();
     lapicinit(cpunum());
   }
-  vminit();        // Run with paging on each processor
+  vminit();        // turn on paging
   cprintf("cpu%d: starting\n", cpu->id);
-  idtinit();
+  idtinit();       // load idt register
   xchg(&cpu->booted, 1);
-  scheduler();
+  scheduler();     // start running processes
 }
 
 static void
@@ -85,6 +86,7 @@ bootothers(void)
   // 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++){
     if(c == cpus+cpunum())  // We've started already.
       continue;
@@ -95,7 +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)
       ;
   }
-- 
cgit v1.2.3