linux-kernel - Re: [PATCH] livepatch: Enforce reliable stack trace as config dependency

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Message-ID: <20190211085345.xiyoto3u2joeajwt@pathway.suse.cz>
Date:   Mon, 11 Feb 2019 09:53:45 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>
Cc:     live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        Miroslav Benes <mbenes@...e.cz>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jiri Kosina <jikos@...nel.org>
Subject: Re: [PATCH] livepatch: Enforce reliable stack trace as config
 dependency

On Sat 2019-02-09 14:47:28, Kamalesh Babulal wrote:
> While the consistency model was introduced, architectures without the
> reliable stack trace implementation could use the immediate flag for
> livepatching but with its own limitations.
> 
> After removal of the immediate flag by commit d0807da78e11
> ("livepatch: Remove immediate feature"), reliable stack trace became
> enforcing dependency for livepatch support on any architecture. In
> the current code, we ensure that the dependency is met when
> enabling the patch during the module load.
> 
> This dependency check can be improved by moving it to the Kconfig,
> which disables the support for livepatching in the kernel for unmet
> dependencies. This patch moves both HAVE_RELIABLE_STACKTRACE and
> STACKTRACE under config LIVEPATCH, it also removes the
> klp_have_reliable_stack() function.
> 
> Loading a livepatching module on an architecture where reliable
> stack trace is yet to be implemented, the user should see:
> 
> insmod: ERROR: could not insert module ./livepatch-sample.ko: Invalid module format
> 
> ...
> [  286.453463] livepatch_sample: module is marked as livepatch module, but livepatch support is disabled
> 
> [pmladek@...e.com: Suggested to explicitly add CONFIG_STACKTRACE under
>  config LIVEPATCH]
> Signed-off-by: Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>

Acked-by: Petr Mladek <pmladek@...e.com>

Best Regards,
Petr