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Date:   Sun, 08 Oct 2017 12:44:12 +0200
From:   Richard Weinberger <richard@....at>
To:     Thomas Meyer <thomas@...3r.de>
Cc:     user-mode-linux-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] um: Fix kcov crash before kernel is started.

Am Sonntag, 8. Oktober 2017, 12:31:58 CEST schrieb Thomas Meyer:
> UMLs current_thread_info() unconditionally assumes that the top of the stack
> contains the thread_info structure. But on UML the __sanitizer_cov_trace_pc
> function is called for *all* functions! This results in an early crash:
> 
> Prevent kcov from using invalid curent_thread_info() data by checking
> the system_state.
> 
> Signed-off-by: Thomas Meyer <thomas@...3r.de>
> ---
>  kernel/kcov.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/kernel/kcov.c b/kernel/kcov.c
> index 3f693a0f6f3e..d601c0e956f6 100644
> --- a/kernel/kcov.c
> +++ b/kernel/kcov.c
> @@ -56,6 +56,12 @@ void notrace __sanitizer_cov_trace_pc(void)
>  	struct task_struct *t;
>  	enum kcov_mode mode;
> 
> +#ifdef CONFIG_UML
> +	if(!(system_state == SYSTEM_SCHEDULING ||
> +	     system_state == SYSTEM_RUNNING))
> +		return;
> +#endif

Hmm, and why does it work on all other archs then?

Thanks,
//richard

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