Re: [PATCH] (3/3) stack overflow checking for x86

["David C. Hansen" <haveblue@us.ibm.com>]

On Thu, 2002-10-31 at 13:30, Dave Jones wrote:
> On Thu, Oct 31, 2002 at 11:20:52AM -0800, David C. Hansen wrote:
>  > * stack checking (3/3)
>  >    - use gcc's profiling features to check for stack overflows upon
>  >      entry to functions.
>  >    - Warn if the task goes over 4k.
>  >    - Panic if the stack gets within 512 bytes of overflowing.
>  >    - use kksymoops information, if available
>  > 
>  > This won't apply cleanly without the irqstack patch, but the conflict is
>  > easy to resolve.  It requires the thread_info cleanup.
> 
> I'm wondering about interaction between this patch and the
> already merged CONFIG_DEBUG_STACKOVERFLOW ?

The currently merged one is very, very simple, but relatively worthless.
There are no guarantees about catching an overflow, especially if it
happens in a long call chain _after_ do_IRQ with interrupts disabled.  
Ben's version checks on entrance to every function, making it _much_
more likely to be caught, even during an interrupt.  But, the currently
merged one doesn't have any strange compiler requirements, like adding
the -p option.

The irq stack patch would make the current check pretty worthless
because the check happens just after the switch to a fresh irqstack
would have happened.

But, if they both get in, it can be cleaned up later because even if
both are turned on, nothing will blow up.  
-- 
Dave Hansen
haveblue@us.ibm.com