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

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Message-ID: <nycvar.YFH.7.76.1902150826400.11598@cbobk.fhfr.pm>
Date:   Fri, 15 Feb 2019 08:28:03 +0100 (CET)
From:   Jiri Kosina <jikos@...nel.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>,
        "vojtech@...e.com" <vojtech@...e.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "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, 15 Feb 2019, 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>

What kernel version is this patch based on? We've got rid of x86-specific 
module loading stub and offloaded all the relocation handling to generic 
kmod loader long time ago.

-- 
Jiri Kosina
SUSE Labs