linux-kernel - Re: [PATCH v5 1/6] Elf: add livepatch-specific Elf constants

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Date:	Mon, 21 Mar 2016 14:47:01 +0100 (CET)
From:	Miroslav Benes <mbenes@...e.cz>
To:	Jessica Yu <jeyu@...hat.com>
cc:	Rusty Russell <rusty@...tcorp.com.au>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Petr Mladek <pmladek@...e.com>, Jiri Kosina <jikos@...nel.org>,
	Jonathan Corbet <corbet@....net>, linux-api@...r.kernel.org,
	live-patching@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
	linux-doc@...r.kernel.org
Subject: Re: [PATCH v5 1/6] Elf: add livepatch-specific Elf constants

On Wed, 16 Mar 2016, Jessica Yu wrote:

> Livepatch manages its own relocation sections and symbols in order to be
> able to reuse module loader code to write relocations. This removes
> livepatch's dependence on separate "dynrela" sections to write relocations
> and also allows livepatch to patch modules that are not yet loaded.
> 
> The livepatch Elf relocation section flag (SHF_RELA_LIVEPATCH),
> and symbol section index (SHN_LIVEPATCH) allow both livepatch and the
> module loader to identity livepatch relocation sections and livepatch
> symbols.
> 
> Livepatch relocation sections are marked with SHF_RELA_LIVEPATCH to
> indicate to the module loader that it should not apply that relocation
> section and that livepatch will handle them.
> 
> The SHN_LIVEPATCH shndx marks symbols that will be resolved by livepatch.
> The module loader ignores these symbols and does not attempt to resolve
> them.
> 
> The values of these Elf constants were selected from OS-specific
> ranges according to the definitions from glibc.
> 
> Signed-off-by: Jessica Yu <jeyu@...hat.com>

Reviewed-by: Miroslav Benes <mbenes@...e.cz>