linux-kernel - Re: [PATCH] livepatch: Remove reliable stacktrace check in klp_try_switch

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Message-ID: <20180716124138.pyqbiviqoxcbs44g@treble>
Date:   Mon, 16 Jul 2018 07:41:38 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>
Cc:     Miroslav Benes <mbenes@...e.cz>, Jiri Kosina <jkosina@...e.cz>,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] livepatch: Remove reliable stacktrace check in
 klp_try_switch_task()

On Thu, Jul 12, 2018 at 01:35:06PM +0530, Kamalesh Babulal wrote:
> Support for immediate flag was removed by commit d0807da78e11
> ("livepatch: Remove immediate feature").  We bail out during
> patch registration for architectures, those don't support
> reliable stack trace. Remove the check in klp_try_switch_task(),
> as its not required.
> 
> Signed-off-by: Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>

Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>

> ---
>  kernel/livepatch/transition.c | 7 -------
>  1 file changed, 7 deletions(-)
> 
> diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
> index 7c6631e693bc..5bc349805e03 100644
> --- a/kernel/livepatch/transition.c
> +++ b/kernel/livepatch/transition.c
> @@ -310,13 +310,6 @@ static bool klp_try_switch_task(struct task_struct *task)
>  		return true;
>  
>  	/*
> -	 * For arches which don't have reliable stack traces, we have to rely
> -	 * on other methods (e.g., switching tasks at kernel exit).
> -	 */
> -	if (!klp_have_reliable_stack())
> -		return false;
> -
> -	/*
>  	 * Now try to check the stack for any to-be-patched or to-be-unpatched
>  	 * functions.  If all goes well, switch the task to the target patch
>  	 * state.
> -- 
> 2.7.4
> 

-- 
Josh