linux-kernel - Re: [PATCH RFC] debugobjects: Make stack check warning more informative

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Message-ID: <b036f4a3-1108-c117-873e-3cb0ccfcf2f3@redhat.com>
Date:   Mon, 23 Jul 2018 20:33:47 -0400
From:   Waiman Long <longman@...hat.com>
To:     Joel Fernandes <joel@...lfernandes.org>,
        linux-kernel@...r.kernel.org
Cc:     kernel-team@...roid.com, Thomas Gleixner <tglx@...utronix.de>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        Arnd Bergmann <arnd@...db.de>, astrachan@...gle.com
Subject: Re: [PATCH RFC] debugobjects: Make stack check warning more
 informative

On 07/23/2018 05:25 PM, Joel Fernandes wrote:
> From: "Joel Fernandes (Google)" <joel@...lfernandes.org>
>
> Recently we debugged an issue where debugobject tracking was telling
> us of an annotation issue. Turns out the issue was due to the object in
> concern being on a different stack which was due to another issue.
>
> Discussing with tglx, he suggested printing the pointers and the
> location of the stack for the currently running task. This helped find
> the object was on the wrong stack. I turned the resulting patch into
> something upstreamable, so that the error message is more informative
> and can help in debugging for similar issues in the future.
>
> Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> ---
>  lib/debugobjects.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/lib/debugobjects.c b/lib/debugobjects.c
> index 994be4805cec..24c1df0d7466 100644
> --- a/lib/debugobjects.c
> +++ b/lib/debugobjects.c
> @@ -360,9 +360,12 @@ static void debug_object_is_on_stack(void *addr, int onstack)
>  
>  	limit++;
>  	if (is_on_stack)
> -		pr_warn("object is on stack, but not annotated\n");
> +		pr_warn("object %p is on stack %p, but NOT annotated.\n", addr,
> +			 task_stack_page(current));
>  	else
> -		pr_warn("object is not on stack, but annotated\n");
> +		pr_warn("object %p is NOT on stack %p, but annotated.\n", addr,
> +			 task_stack_page(current));
> +
>  	WARN_ON(1);
>  }
>  

Acked-by: Waiman Long <longman@...hat.com>