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

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Date:	Fri, 31 Aug 2007 09:32:53 -0700
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	linux-kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH] detect & print stack overruns at oops time

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
*** Remember to use Documentation/SubmitChecklist when testing your code ***
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