diff -urpN -X /home/fletch/.diff.exclude 221-interrupt_stacks/arch/i386/Kconfig 222-stack_usage_check/arch/i386/Kconfig
--- 221-interrupt_stacks/arch/i386/Kconfig	Sun Apr 20 22:07:00 2003
+++ 222-stack_usage_check/arch/i386/Kconfig	Sun Apr 20 22:07:01 2003
@@ -1630,6 +1630,25 @@ config FRAME_POINTER
 	  If you don't debug the kernel, you can say N, but we may not be able
 	  to solve problems without frame pointers.
 
+config X86_STACK_CHECK
+	bool "Detect stack overflows"
+	depends on FRAME_POINTER
+	help
+	  Say Y here to have the kernel attempt to detect when the per-task
+	  kernel stack overflows.  This is much more robust checking than
+	  the above overflow check, which will only occasionally detect
+	  an overflow.  The level of guarantee here is much greater.
+	
+	  Some older versions of gcc don't handle the -p option correctly.  
+	  Kernprof is affected by the same problem, which is described here:
+	  http://oss.sgi.com/projects/kernprof/faq.html#Q9
+	
+	  Basically, if you get oopses in __free_pages_ok during boot when
+	  you have this turned on, you need to fix gcc.  The Redhat 2.96 
+	  version and gcc-3.x seem to work.  
+	
+	  If not debugging a stack overflow problem, say N
+
 config X86_EXTRA_IRQS
 	bool
 	depends on X86_LOCAL_APIC || X86_VOYAGER
diff -urpN -X /home/fletch/.diff.exclude 221-interrupt_stacks/arch/i386/Makefile 222-stack_usage_check/arch/i386/Makefile
--- 221-interrupt_stacks/arch/i386/Makefile	Sun Apr 20 21:09:40 2003
+++ 222-stack_usage_check/arch/i386/Makefile	Sun Apr 20 22:07:01 2003
@@ -76,6 +76,10 @@ mcore-$(CONFIG_X86_SUMMIT)  := mach-defa
 # default subarch .h files
 mflags-y += -Iinclude/asm-i386/mach-default
 
+ifdef CONFIG_X86_STACK_CHECK
+CFLAGS += -p
+endif
+
 head-y := arch/i386/kernel/head.o arch/i386/kernel/init_task.o
 
 libs-y 					+= arch/i386/lib/
diff -urpN -X /home/fletch/.diff.exclude 221-interrupt_stacks/arch/i386/boot/compressed/misc.c 222-stack_usage_check/arch/i386/boot/compressed/misc.c
--- 221-interrupt_stacks/arch/i386/boot/compressed/misc.c	Sun Apr 20 19:34:56 2003
+++ 222-stack_usage_check/arch/i386/boot/compressed/misc.c	Sun Apr 20 22:07:01 2003
@@ -379,3 +379,7 @@ asmlinkage int decompress_kernel(struct 
 	if (high_loaded) close_output_buffer_if_we_run_high(mv);
 	return high_loaded;
 }
+
+/* We don't actually check for stack overflows this early. */
+__asm__(".globl mcount ; mcount: ret\n");
+
diff -urpN -X /home/fletch/.diff.exclude 221-interrupt_stacks/arch/i386/kernel/entry.S 222-stack_usage_check/arch/i386/kernel/entry.S
--- 221-interrupt_stacks/arch/i386/kernel/entry.S	Sun Apr 20 22:07:00 2003
+++ 222-stack_usage_check/arch/i386/kernel/entry.S	Sun Apr 20 22:07:01 2003
@@ -682,6 +682,61 @@ ENTRY(spurious_interrupt_bug)
 	pushl $do_spurious_interrupt_bug
 	jmp error_code
 
+
+#ifdef CONFIG_X86_STACK_CHECK
+.data
+	.globl	stack_overflowed
+stack_overflowed:
+	.long	0
+.text
+
+ENTRY(mcount)
+	push %eax
+	movl $(THREAD_SIZE - 1),%eax
+	andl %esp,%eax
+	cmpl $STACK_WARN,%eax	/* more than half the stack is used*/
+	jle 1f
+2:
+	popl %eax
+	ret
+1:	
+	lock;   btsl    $0,stack_overflowed
+	jc      2b
+	
+	# switch to overflow stack
+	movl	%esp,%eax
+	movl	$(stack_overflow_stack + THREAD_SIZE - 4),%esp
+
+	pushf
+	cli
+	pushl	%eax
+
+	# push eip then esp of error for stack_overflow_panic
+	pushl	4(%eax)
+	pushl	%eax
+
+	# update the task pointer and cpu in the overflow stack's thread_info.
+	GET_THREAD_INFO_WITH_ESP(%eax)
+	movl	TI_TASK(%eax),%ebx
+	movl	%ebx,stack_overflow_stack+TI_TASK
+	movl	TI_CPU(%eax),%ebx
+	movl	%ebx,stack_overflow_stack+TI_CPU
+
+	call	stack_overflow
+
+	# pop off call arguments
+	addl	$8,%esp 
+
+	popl	%eax
+	popf
+	movl	%eax,%esp
+	popl	%eax
+	movl	$0,stack_overflowed
+	ret
+
+#warning stack check enabled
+#endif
+
 .data
 ENTRY(sys_call_table)
 	.long sys_restart_syscall	/* 0 - old "setup()" system call, used for restarting */
diff -urpN -X /home/fletch/.diff.exclude 221-interrupt_stacks/arch/i386/kernel/i386_ksyms.c 222-stack_usage_check/arch/i386/kernel/i386_ksyms.c
--- 221-interrupt_stacks/arch/i386/kernel/i386_ksyms.c	Sun Apr 20 21:28:58 2003
+++ 222-stack_usage_check/arch/i386/kernel/i386_ksyms.c	Sun Apr 20 22:07:01 2003
@@ -225,3 +225,8 @@ EXPORT_SYMBOL(kmap_atomic_to_page);
 EXPORT_SYMBOL(edd);
 EXPORT_SYMBOL(eddnr);
 #endif
+
+#ifdef CONFIG_X86_STACK_CHECK
+extern void mcount(void);
+EXPORT_SYMBOL(mcount);
+#endif
diff -urpN -X /home/fletch/.diff.exclude 221-interrupt_stacks/arch/i386/kernel/init_task.c 222-stack_usage_check/arch/i386/kernel/init_task.c
--- 221-interrupt_stacks/arch/i386/kernel/init_task.c	Sun Apr 20 22:07:00 2003
+++ 222-stack_usage_check/arch/i386/kernel/init_task.c	Sun Apr 20 22:07:01 2003
@@ -17,6 +17,10 @@ struct mm_struct init_mm = INIT_MM(init_
 union thread_union init_irq_union
 	__attribute__((__section__(".data.init_task")));
 
+#ifdef CONFIG_X86_STACK_CHECK
+union thread_union stack_overflow_stack
+	__attribute__((__section__(".data.init_task")));
+#endif
 
 /*
  * Initial thread structure.
diff -urpN -X /home/fletch/.diff.exclude 221-interrupt_stacks/arch/i386/kernel/process.c 222-stack_usage_check/arch/i386/kernel/process.c
--- 221-interrupt_stacks/arch/i386/kernel/process.c	Sun Apr 20 22:07:00 2003
+++ 222-stack_usage_check/arch/i386/kernel/process.c	Sun Apr 20 22:07:01 2003
@@ -160,7 +160,25 @@ static int __init idle_setup (char *str)
 
 __setup("idle=", idle_setup);
 
-void show_regs(struct pt_regs * regs)
+void stack_overflow(unsigned long esp, unsigned long eip)
+{
+	int panicing = ((esp&(THREAD_SIZE-1)) <= STACK_PANIC);
+
+	printk( "esp: 0x%lx masked: 0x%lx STACK_PANIC:0x%x %d %d\n", 
+		esp, (esp&(THREAD_SIZE-1)), STACK_PANIC, (((esp&(THREAD_SIZE-1)) <= STACK_PANIC)), panicing );
+	
+	if (panicing)
+		print_symbol("stack overflow from %s\n", eip);
+	else
+		print_symbol("excessive stack use from %s\n", eip);
+	printk("esp: %p\n", (void*)esp);
+	show_trace((void*)esp);
+	
+	if (panicing)
+		panic("stack overflow\n");
+}
+
+asmlinkage void show_regs(struct pt_regs * regs)
 {
 	unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
 
diff -urpN -X /home/fletch/.diff.exclude 221-interrupt_stacks/include/asm-i386/thread_info.h 222-stack_usage_check/include/asm-i386/thread_info.h
--- 221-interrupt_stacks/include/asm-i386/thread_info.h	Sun Apr 20 22:07:00 2003
+++ 222-stack_usage_check/include/asm-i386/thread_info.h	Sun Apr 20 22:07:01 2003
@@ -65,6 +65,8 @@ struct thread_info {
  */
 #define THREAD_ORDER 1 
 #define INIT_THREAD_SIZE       THREAD_SIZE
+#define STACK_PANIC		0x200ul
+#define STACK_WARN		((THREAD_SIZE)>>1)
 
 #ifndef __ASSEMBLY__