linux-kernel - Re: [PATCH v2] arm64/module: use mod->klp_info section header information for livepatch modules

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Date:   Mon, 29 Oct 2018 14:24:16 +0100 (CET)
From:   Miroslav Benes <mbenes@...e.cz>
To:     Jessica Yu <jeyu@...nel.org>
cc:     Torsten Duwe <duwe@....de>, 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>,
        Petr Mladek <pmladek@...e.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        live-patching@...r.kernel.org
Subject: Re: [PATCH v2] arm64/module: use mod->klp_info section header
 information for livepatch modules


> diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c
> index dd23655fda3a..490e56070a7e 100644
> --- a/arch/arm64/kernel/module.c
> +++ b/arch/arm64/kernel/module.c
> @@ -461,5 +461,15 @@ int module_finalize(const Elf_Ehdr *hdr,
> #endif
> 	}
> 
> +#ifdef CONFIG_LIVEPATCH
> +	/*
> +	 * For livepatching, switch to the saved section header info for .plt
> +	 * stored in mod->klp_info. This is needed so that livepatch is able to
> +	 * call apply_relocate_add() after patch module load.
> +	 */
> +	if (is_livepatch_module(me))
> +		me->arch.core.plt = me->klp_info->sechdrs + me->arch.core.plt_shndx;
> +#endif

I missed it before, but the hunk should be under "#ifdef 
CONFIG_ARM64_MODULE_PLTS" protection similarly to ftrace_trampoline just 
above. me->arch.core.plt may not exist otherwise.

Miroslav