Re: [RFC][PATCH] detect & print stack overruns at oops time

Randy Dunlap
2007-08-31T16:33:20Z

On Fri, 31 Aug 2007 00:28:58 -0500 Eric Sandeen wrote:

> Index: linux-2.6.22-rc4/arch/i386/mm/fault.c
> ===================================================================
> --- linux-2.6.22-rc4.orig/arch/i386/mm/fault.c
> +++ linux-2.6.22-rc4/arch/i386/mm/fault.c
> @@ -543,6 +545,27 @@ no_context:
> printk(KERN_ALERT "BUG: unable to handle kernel paging"
> " request");
> printk(" at virtual address %08lx\n",address);
> +
> + overrun = (unsigned long)stackend - (unsigned long)(&regs->esp);
> + if (overrun > 0) {
> + printk(KERN_ALERT "Thread overrunning stack by %d "
> + "bytes\n", overrun);
> + } else {

Hi,

Is there something that tells us what <Thread> is doing all of this
bad juju?

> +#ifdef CONFIG_DEBUG_STACK_USAGE
> + int free;
> + unsigned long *n = stackend;
> + while (!*n)
> + n++;
> + free = (unsigned long)n - (unsigned long)stackend;
> + if (free)
> + printk(KERN_ALERT "Thread used within %d bytes"
> + " of stack end\n", free);
> +#endif
> + /* won't catch 100% - stack may have 0s here by chance */
> + if (*stackend) /* was init'd to 0 */
> + printk(KERN_ALERT "Thread overran the stack?\n");
> + }
> +
> printk(KERN_ALERT " printing eip:\n");
> printk("%08lx\n", regs->eip);
>

---
~Randy
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