linux-kernel - Re: [PATCH v4 2/3] arm64: implement live patching

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Message-ID: <alpine.LSU.2.21.1811061745440.30614@pobox.suse.cz>
Date:   Tue, 6 Nov 2018 17:49:07 +0100 (CET)
From:   Miroslav Benes <mbenes@...e.cz>
To:     Torsten Duwe <duwe@....de>
cc:     Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Julien Thierry <julien.thierry@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        live-patching@...r.kernel.org
Subject: Re: [PATCH v4 2/3] arm64: implement live patching

Hi,

On Fri, 26 Oct 2018, Torsten Duwe wrote:

> Based on ftrace with regs, do the usual thing.
> (see Documentation/livepatch/livepatch.txt)
> 
> Use task flag bit 6 to track patch transisiton state for the consistency
> model. Add it to the work mask so it gets cleared on all kernel exits to
> userland.
> 
> Tell livepatch regs->pc is the place to change the return address.
> Make sure the graph tracer call hook is only called on the final function
> entry in case regs->pc gets modified after an interception.
> 
> Signed-off-by: Torsten Duwe <duwe@...e.de>

It looks good now apart from arm64 asm part which should be reviewed by 
someone else.

However, could you summarize our analysis regarding post-module-load calls 
of apply_relocate_add() in the commit log, please? It is important for 
future reference.

Thanks,
Miroslav