x

kernel/entry.S

@@ -1,14 +1,8 @@
-	# qemu -kernel starts at 0x1000. the instructions
-        # there seem to be provided by qemu, as if it
-        # were a ROM. the code at 0x1000 jumps to
-        # 0x80000000, the _start function here,
-        # in machine mode. each CPU starts here.
-.section .data
-.globl stack0
+	# qemu -kernel loads the kernel at 0x80000000
+        # and causes each CPU to jump there.
+        # kernel.ld causes the following code to
+        # be placed at 0x80000000.
 .section .text
-.globl start
-.section .text
-.globl _entry
 _entry:
 	# set up a stack for C.
         # stack0 is declared in start.c,
@@ -22,5 +16,5 @@ _entry:
         add sp, sp, a0
 	# jump to start() in start.c
         call start
-junk:
-        j junk
+spin:
+        j spin

user/init.c

@@ -31,8 +31,20 @@ main(void)
       printf("init: exec sh failed\n");
       exit(1);
     }
-    while((wpid=wait(0)) >= 0 && wpid != pid){
-      //printf("zombie!\n");
+
+    for(;;){
+      // this call to wait() returns if the shell exits,
+      // or if a parentless process exits.
+      wpid = wait((int *) 0);
+      if(wpid == pid){
+        // the shell exited; restart it.
+        break;
+      } else if(wpid < 0){
+        printf("init: wait returned an error\n");
+        exit(1);
+      } else {
+        // it was a parentless process; do nothing.
+      }
     }
   }
 }

user/initcode.S

@@ -1,4 +1,4 @@
-# Initial process execs /init.
+# Initial process that execs /init.
 # This code runs in user space.
 
 #include "syscall.h"