linux-kernel - Re: [PATCH] x86: livepatch: Treat R_X86_64_PLT32 as R_X86_64

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Date:   Mon, 18 Feb 2019 12:47:49 +0100
From:   "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
To:     "chenzefeng (A)" <chenzefeng2@...wei.com>
Cc:     "hjl.tools@...il.com" <hjl.tools@...il.com>,
        "jpoimboe@...hat.com" <jpoimboe@...hat.com>,
        "sjenning@...hat.com" <sjenning@...hat.com>,
        "jikos@...nel.org" <jikos@...nel.org>,
        "vojtech@...e.com" <vojtech@...e.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
        "live-patching@...r.kernel.org" <live-patching@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "chengjian (D)" <cj.chengjian@...wei.com>
Subject: Re: [PATCH] x86: livepatch: Treat R_X86_64_PLT32 as R_X86_64_PC32

On Fri, Feb 15, 2019 at 02:01:31AM +0000, chenzefeng (A) wrote:
> On x86-64, for 32-bit PC-relacive branches, we can generate PLT32 relocation, instead of PC32 relocation. and R_X86_64_PLT32 can be treated the same as R_X86_64_PC32 since linux kernel doesn't use PLT.
> 
> In linux 4.4 commit b21ebf2fb4cd ("x86: Treat R_X86_64_PLT32 as R_X86_64_PC32") been fixed for the module loading, but not fixed for livepatch relocation, which will fail to load livepatch with the error message as follow:
> relocation failed for symbol <symbol name> at <symbol address>
> 
> Signed-off-by: chenzefeng <chenzefeng2@...wei.com>
> ---
>  arch/x86/kernel/livepatch.c | 1 +
>  1 file changed, 1 insertion(+)

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>