linux-kernel - Re: [PATCH] debug: Do not permit CONFIG_DEBUG_STACK

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Date:	Wed, 25 Jul 2012 09:45:01 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Tony Luck <tony.luck@...el.com>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	"James E.J. Bottomley" <jejb@...isc-linux.org>,
	Helge Deller <deller@....de>, linux-parisc@...r.kernel.org,
	linux-ia64@...r.kernel.org, Fengguang Wu <fengguang.wu@...el.com>
Subject: Re: [PATCH] debug: Do not permit CONFIG_DEBUG_STACK_USAGE=y on IA64
 or PARISC


* Tony Luck <tony.luck@...el.com> wrote:

> The stack_not_used() function in <linux/sched.h> assumes that stacks
> grow downwards. This is not true on IA64 or PARISC, so this function
> would walk off in the wrong direction and into the weeds.
> 
> Found on IA64 because of a compilation failure with recursive dependencies
> on IA64_TASKSIZE and IA64_THREAD_INFO_SIZE.
> 
> Fixing the code is possible, but should be combined with other
> infrastructure additions to set up the "canary" at the end of the stack.
> 
> Reported-by: Fengguang Wu <fengguang.wu@...el.com> (failed allmodconfig build)
> Signed-off-by: Tony Luck <tony.luck@...el.com>
> ---
>  lib/Kconfig.debug | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index ff5bdee..4a18650 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -714,7 +714,7 @@ config STACKTRACE
>  
>  config DEBUG_STACK_USAGE
>  	bool "Stack utilization instrumentation"
> -	depends on DEBUG_KERNEL
> +	depends on DEBUG_KERNEL && !IA64 && !PARISC

The modern way of doing this is by adding an ARCH_SUPPORTS_ 
flag.

Thanks,

	Ingo
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